hidraulica magazine 3-4-2012

8/13/2019 Hidraulica Magazine 3-4-2012

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HYDRAULICS

PNEUMATICS

TRIBOLOGY

ECOLOGY

MECHATRONICS

SENSORICS

THEMATICS:

No. 3 - 4 / November 2012

www.fluidas.ro/hidraulica

is published with support of ASSOCIATION OF

HYDRAULICS AND PNEUMATICSFLUIDAS

HIDRAULICA Magazine HIDRAULICA Magazineis indexed in the

Romanian Editorial PlatformSCIPIO

HIDRAULICA Magazineis edited by

HYDRAULICS & PNEUMATICSRESEARCH INSTITUTE

INOE 2000 - IHP

HIDRAULICA Magazine is indexed in the international databases

ISSN 1453 - 7303


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ISSN 1453 - 7303 HIDRAULICA (No. 3-4/2012)

Magazine of Hydraulics, Pneumatics, Tribology , Ecology, Sensorics, Mechatronics

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CONTENTS

PREGATIREA SPECIALISTILOR IN VEDEREA ADAPTABILITATII SI CRESTERIICOMPETITIVITATII

Dr. Ing. Gabriela MATACHE, Dr. Ing. Corneliu CRISTESCU, Dr. Ing. Ctlin DUMITRESCU, Asc. Valentin MIROIU

7 - 14

MICRO-HYDROPOWER STATION FOR KINETIC ENERGY CONVERSION OFFLOWING WHATER

Ion BOSTAN, Valeriu DULGHERU

15 - 21

EXPERIMENTAL RESULTS REGARDING ROTATIONAL SPEED OF THE ALTERNATING FLOW DRIVEN HYDRAULIC MOTORS WITH A STARINTERCONNECTION OF THE WORKING VOLUMES

Ioan-Lucian MARCU, Daniel- Vasile BANYAI, Claudia KOZMA, Gabriela MATACHE

22 - 27

NUMERICAL SIMULATION OF THE SERVO MECHANISM FOR ADJUSTING THECAPACITY OF THE RADIAL PISTON PUMPS

Liliana DUMITRESCU, Ctlin DUMITRESCU,Ioan LEPDATU

28 - 33

CONSIDERATIONS ABOUT DIGITAL PID CONTROL OF ELECTRO-HYDRAULICSEQUIPMENT

Iulian DUU, Radu RDOI, Corneliu CRISTESCU

34 - 38

PNEUMATIC MEASURING OF THE BIOMASS CONSUMPTION FOR TLUD

GENERATORErol MURAD, Ctlin DUMITRESCU, Georgeta HARAGA, Liliana DUMITRESCU

39 - 44

OSCILLATORY ANALYSIS OF PISTON PUMPSIoana Sfrlea, Daniel Banyai, Lucian Marcu, Liviu Vaida, Dan Oprua

45 - 53

EDUCATION IN DEVELOPMENT OF ELECTRONIC MODULES USING FREE ANDOPEN SOURCE SOFTWARE TOOLS

Andrei DRUMEA

54 -60

SYNTHESIS OF MAIN CHARACTERISTICS AND COMMON SCHEMES USED INSTRUCTURING OF HYDRAULIC SOURCES

Radu RADOI, Catalin DUMITRESCU, Iulian DUTU, Gabriela MATACHE

61 - 66

THE MODERNIZATION OF THE MAC 3 MACHINES FROM THE SUBSTITUTIONOF THE MECHANISM OF THE PRESSING ROOM

DAVID Ladislau, DINU Ion

67 - 72

COMPUTER ASSISTED ELECTRO-HYDRAULIC STAND FOR TESTINGSERVOVALVES

Iulian DUU, Gabriela MATACHE

73 - 77


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MANAGER OF PUBLICATION

- PhD. Eng. Petrin DRUMEA - Manager - Hydraulics and Pneumatics Research Institute in

Bucharest, Romania

CHIEF EDITOR

- PhD.Eng. Gabriela MATACHE - Hydraulics and Pneumatics Research Institute in Bucharest,

Romania

EXECUTIVE EDITORS

- Ana-Maria POPESCU - Hydraulics and Pneumatics Research Institute in Bucharest, Romania

- Valentin MIROIU - Hydraulics and Pneumatics Research Institute in Bucharest, Romania

SPECIALIZED REVIEWERS

- PhD. Eng. Heinrich THEISSEN Scientific Director of Institute for Fluid Power Drives and

Controls IFAS, Aachen - Germany

- Prof. PhD. Eng. Henryk CHROSTOWSKI Wroclaw University of Technology, Poland

- Prof. PhD. Eng. Pavel MACH Czech Technical University in Prague, Czech Republic

- Prof. PhD. Eng. Alexandru MARIN POLITEHNICA University of Bucharest, Romania

- Assoc. Prof. PhD. Eng. Constantin RANEA POLITEHNICA University of Bucharest, Romania

- Lect. PhD. Eng. Andrei DRUMEA POLITEHNICA University of Bucharest, Romania

- PhD.Eng. Ion PIRNA - General Manager - National Institute Of Research - Development for

Machines and Installations Designed to Agriculture and Food Industry INMA, Bucharest-

Romania

- Prof. PhD.Eng. Gheorghe GHEORGHE - General Manager - National Institute of Research and

Development in Mechatronics and Measurement Technique (INCDMTM), Bucharest, Romania

- PhD.Eng. Gabriela MATACHE - Hydraulics & Pneumatics Research Institute in Bucharest,

Romania

- PhD.Eng.Corneliu CRISTESCU - Hydraulics & Pneumatics Research Institute in Bucharest,

Romania

- Prof.PhD.Eng. Dan Opruta - Technical University of Cluj Napoca, ROMANIA

Published by:Hydraulics & Pneumatics Research Instit ute, Bucharest-Romania Address: 14 Cuitul de Argint, district 4, Bucharest, cod 040557, ROMANIA Phone: +40 21 336 39 90; +40 21 336 39 91 ; Fax:+40 21 337 30 40 ; E-mail: [email protected]: www.ihp.rowith support of:National Professio nal Asso ciation o f Hydraulics and Pneumatics in Romania - FLUIDASE-mail: [email protected]: www.fluidas.ro


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PREGATIREA SPECIALISTILOR IN VEDEREA ADAPTABILITATII SICRESTERII COMPETITIVITATII

Dr. Ing. Gabriela MATACHE*, Dr. Ing. Corneliu CRISTESCU*, Dr. Ing. Ctlin DUMITRESCU*,Asc. Valentin MIROIU*

*Asociaia Na ional Profesional de Hidraulic si Pneumatic FLUIDAS, Bucureti - ROMANIAe-mail: [email protected]

1. Introducere

n ultimii ani, hidraulica i pneumatica au cunoscut o cretere nemantlnit n istorie i simultan odezvoltare calitativ, tehnico-tiinific, greu de asimilat chiar i de oamenii cu preocupri n

domeniu. Introducerea pe scar larg a electronicii i informaticii n sistemele hidropneumatice,diversificarea i multiplicarea funciilor echipamentelor au condus la relansarea discuiilor privindpregtirea profesional a lucrtorilor din domeniu. La o analiz atent i obiectiv se constat cnumrul specialitilor cu pregtire superioar i medie a scazut la limite alarmante. Este interesantc la nivelul absolvenilor de invmnt superior problemele se cantoneaz n zona calitiipregtirii i a interesului pentru domeniu dup absolvire, n timp ce la tehnicieni i muncitori,problemele apar nc de la nceput prin lipsa colilor de specialitate sau a unor cursuri de pregtirespecific de perfecionare sau de reconversie. n anii 1990-2000 aveam specialiti cu o pregtire ndelungat n vechile uniti de producie sau n unitile de cercetare-proiectare, specialitiselectai dintre cei peste 30.000 de lucrtori din domeniu. ntruct aceea a fost o perioad decdere a hid raulicii, ca de altfel a ntregii industrii, nu s-a mai pus nici o clip problema crerii denoi specialiti, astfel c n ultimul timp numrul acestora s-a diminuat foarte mult, fie pe cinaturale (pensionri), fie prin migrarea spre domenii mai interesante financiar. Singura ramur cares-a dezvoltat n acest timp a fost cea a vnzrilor, dar i aici au aparut multe probleme legate denumr i de nivelul pregtirii. Ideea c nu mai e chiar aa mare nevoie de tehnicieni, pentru caproducia a sczut la aproximativ o zecime fa de anul 1989, a fost i este eronat, fiind posibil snu mai fim capabili nici s exploatam echipamentele fabricate de alii. S nu uitm c timpul ncare poate fi pregtit un bun specialist n domeniu, indiferent de nivelul tehnico-tiinific la careajunge, este de ordinul a 2- 3 ani n condiiile n care lucreaz n permanen n domeniu. Dinpcate, la ora actual hidraulic i pneumatic au puine argumente (evident financiare) prin carear putea face un tnr s intre ntr -un program intens de pregatire poate n afar de obinerea unuicertificat care s-i permit angajarea la orice firm european membr a CETOP. Interesant esteca problemele legate de lipsa specialitilor n domeniu sunt acut resimite i n restul riloreuropene, motiv pentru care asociaia de specialitate CETOP a pornit o aciune intens de stabilirea unor metode de ridicare a nivelului profesional, care s permit celor care trec printr -o anumitpregatire i evaluare s capete o recunoatere valabil l a nivel continental.

2. Corelarea perfecionrii pregtirii profesionale cu cerinele economiei

Sistemele de acionare hidraulice sunt folosite pe scar larg ntr -un numr mare de aplicaiidatorit posibilittii de a obine cupluri i fore mari pentru un gabarit redus sau pentru obinereaunor parametrii mecanici (pozitii, viteze, acceleraii, fore, cupluri, puteri, etc.) n condiii de preciziei dinamic ridicat. ndeplinirea condiiilor de precizie i dinamic ridicat nu este posibil frutilizarea elementelor electronice/informatice i a conceptului de mecatronic. O alt gam de aplicaii este legat de robotic industrial i sisteme flexibile de fabricaie.

Exist mai multe necesiti pentru obinerea unor specialiti n acest domeniu i nu numai::


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- necesitatea perfecionrii profesionale a lucrtorilor din domeniu, pornind de la largarspndire a acionrilor hidropneumatice pe toate utilajele mobile i pe majoritatea celor fixe, i dela creterea nivelului tehnico-stiinific al echipamentelor i sistemelor;

- necesitatea nfiinrii unor centre dotate cu personal i laboratoare capabile s desfoareo astfel de perfecionare;

- obligativitatea alinierii pregtirii profesionale a lucrtorilor din ar n domeniul hidraulicii lanivelul cerinelor europene;

- situaia real existent n ar care face ca s nu se poat trece la o perfecionare ndomeniul hidraulicii fr o perfecionare prealabil n domeniul mecanicii fine. Echipamentele i utilajele complexe care includ micare, au nevoie de un sistem de acionarecare, tradiional, poate fi mecanic, electric, hidraulic sau pneumatic, dar de cele mai multe ori ocombinaie a acestora. Exist o competiie acerb ntre aceste tipuri de sisteme, dar ctigtoruleste dat de perform an tehnic, de calculul economic i mai nou i de performaa de ecologie -mediu. Competiia aceasta suplimentar competiiei dintre productori a condus la o dezvoltareinteresant a sistemelor hidropneumatice, cu consecine pozitive n nivelul tehnic al utilajelorcomplexe. Creterea nivelului tehnico-tiinific s-a realizat mai ales n domeniile pneumaticii isistemelor de ungere centralizat.

Principalele tendine , care vor implica modificri structurale n pregtirea lucrtorilor dindomeniu sunt ur mtoarele:

- electronizarea i informatizarea echipamentelor i subansamblelor. Aceasta soluie a fos,tdeja, aplicat n zona pneumaticii i a echipamentelor de ungere centralizat fcnd din acestea obaz important a mecatronicii. Hidraulica dei a pornit actiunea de mai mult timp nc i maicaut elementele tehnice eficiente economic. Aceast tendin a mrit n Romnia discrepanadintre nivelul tehnic ridicat al echipamentelor i nivelul profesional sczut al lucrtorilor dindomeniu;

- utilizarea materialelor noi cu performane ridicate n fabricaia echipamentelorhidropneumatice. Primele efecte au fost acelea de a putea fi ridicai parametri funcionali de tipul

presiunilor, forelor i momentelor pentru echipamente de acelai gabarit. Aceast tendinnecesit o abordare nou mai ales la nivelul proteciei muncii; - utilizarea unor tehnologii de fabricaie moderne. Aceste nouti au condus la creterea

performanelor de tipul debitelor i vitezelor, permind schimbri i la nivelul comenzilor.Modificrile de acest tip au mari influene asupra pregtirii profesionale a lucrtorilor n privinamentenanei i a proteciei muncii;

- utilizarea unor fluide de lucru biodegradabile sau nepoluante. Schimbarea fluidelor delucru asigur o ans n plus hidraulicii de a scap de necazul impactului negativ asupra mediului,dar i o modificare a gndirii tehnologice a productorilor i utilizatorilor de astfel de echipamente.

n ultimii ani, s-a constatat o cretere a deficitului de lucrtori specializai simultan cucreterea nivelului tehnic al echipamentelor hidropneumatice importate direct sau n componenaunor utilaje complexe. Urmarea este c de cele mai multe ori dup incercri euate de mentenani reparaii cu diversi pseudospecialiti, posesorii acestor utilaje i echipamente au fost obligai sapeleze la specialitii strini. Cheltuielile cu acetia au devenit foarte mari conducnd la o cretereartificial i nedorit a produselor i serviciilor realizate cu aceste utilaje i echipamente. Pr actica adovedit c lucrtorii notri au probleme nu doar cu hidropneumatica ci i cu mecanica fin i cuansamblurile mecano-hidraulice.

De asemenea, lucrtorii, precum i conductorii acestora nc nu au neles importanaecologizrii activitii i necesitatea aplicrii unor tehnologii de lucru i de mentenan care spermit si s asigure evitarea impactului negativ asupra mediului. Toate aceste aciunipreconizate trebuie s se desfsoare cu o mare atenie privind protecia muncii , date fiindnoutile tehnice i pericolele implicate asupra personalului de intreinere.


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3. Experiena internaional n perfecionarea pregtirii specialistilor de intreinere cuspecializarea n echipamente de acionare hidraulic i pneumatic

La nivel European cursurile de perfecionare n domeniul acionrilor hidro-pneumatice sunt laun nivel foarte ridicat. rile cu industrie dezvoltat i-au dat seama de necesitatea instruiriicontinue a specialistilor pentru a ine pasul cu noile descoperiri n domeniu. nEuropa, sunt centrede pregtire n domeniu n ri ca Germania, Anglia, Italia, Franta, Spania si Polonia, figura 1..Toate aceste Centre de perfecionare respect recomandrile Comisiei de educaie a CETOP.

Fig. 1 Centre de pregtire n domeniu hidraulicii i pneumaticii

Relaia dintre pregtirea teoretic i cea practic la nivel European Analiznd situaia pregtirii profesionale din domeniul hidraulicii i pneumaticii s-a constatat la niveleuropean o situaie, de altfel asteptat, n care cei care tiu teorie nu prea au capacitatea de atransfera n practic ceea ce tiu, iar cei cu o indemnare acceptabil nu au inelegerea teoretic afenomenelor pe care le supravegheaz. Pornind de la aceste date, la nivelul CETOP s -a decis cperfectionarea pregtirii profesionale s fie n aa fel structurat nct personalul s se transforme n specialiti numai cnd exist o corelare foarte exact a cunotinelor teoretice necesare cu obun ndemanarea i capacitatea de a le aplica n practic. Aceasta idee artat faptul ca structuracursurilor trebuie sa fie adaptata n consecin, iar evaluarea s cuprind n egal msura ambeleaspecte.Este de mare interes s tim c indiferent de nivelul de pregtire ce urmeaz a fi acreditat, esteimplicat o bun cunoastere a structurii echipamentelor i sistemelor, precum i capacitateaintervenei directe i calificate. Cursurile de pregtire n domeniu sunt echilibrate ca numr de ore ntre teorie i practic i se vor finaliza ntotdeauna cu o evaluare complet. Orice examen pentrua fi trecut trebuie s consemneze i reuita la teorie i reuita la practic . Nu exist posibilitateaacordrii unei trepte de specializare, dac nu sunt indeplinite baremurile la ambele pri alecursului. Acest lucru va obliga pe cei care se ocup de perfecionarea pregtirii profesionale sstructureze cursurile n acest sens i s dispun de faciliti minime att pentru partea teoretic dari pentru partea practic.

Propunerea de educare i formare i iniiative de armoniza re pentru EUROPA

Odat cu nevoia ridicat din Europa i din lume pentru o mn de lucru competent i bineeducat, capabil s menin i s manevreze sisteme hidraulice, CETOP a preluat initiaiva de alansa o propunere pentru a dezvolta un program de a instrui mna de lucru pe domeniul respectiv.


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Scopul acestui program consta n realizarea unei structurii agreate i acceptate de Baza decalificare a competenelor reflectnd nevoile persoanelor care se afl n categoriile 1,2 i 3acoperite de Nivelul Ocupaional. Aceast structur, reflect nevoile persoanelor angajate sau carese pregatesc s se angajeze intr -un domeniu particular.Din punct de vedere istoric, un numr mare de persoane au obinut o calificare care atest nivelullor academic i nu evideniaz abilitatea acelei persoane de a pune n aplicare cunotineledobndite.Abilitile asociate domeniului de Management i Mentenan a sistemelor hidraulice sunt:

Planificarea i pregtirea; Instalarea; Punerea n funciune; Testarea; Mentenana; Diagnozai rectificare; nlocuirea i modificarea; Demontarea i asamblarea.

Pentru a realiza aceste activiti la diferite niveluri ocupaionale i pentru a r ealiza un nivel deperforman i repetabilitate ntr -un timp dat, necesit ca acea persoan s fie COMPETENT. O Calificare pe Baz de Competene, va consta dintr -o combinare de cunotine i aplicareacunotinelor, susinute de experiena practic la locul de munc sau n domenii simulate.

4. Nivelele ocupaionale versus programele de studii pentru a respecta nevoi leocupaionale bazate pe cunotine /competen

n continuare se prezint; o exemplificare a diferenelor dintre cunotinele bazate pe nivelurile deconsideraiune. Ca exemplu este folosit o supap de siguran i aceast ANALOGIEevideniaz diferena de cunoatere, necesar la diferite niveluri, i indic clar modul n carepregtirea i experiena fac diferena, i anume:

La nivelul 1 candidaii trebuie s tie ce este o supap de siguran, rolul ei, i scopul utilizrii.(Funciile de Baz)

La nivelul 2 candidaii trebuie s tie n plus fa de cei de la nivelul 1 i modul n carefuncioneaz. (Funcii de Baz i ionare)

La nivelul 3 candidaii trebuie s tie i diferitele modaliti de folosire a valvei de siguran(control proporional, golire), i ce erori pot aprea (Noiuni, Operaii, Aplicaii i SpecificaiiTehnice)

La nivelul 4 candidaii trebuie s cunoasc toate detaliile de la nivelul 3 si ar putea fii implicai i n stadiul de proiectare i selectarea componentelor compabilitate.

La nivelul 5 candidatul trebuie s aibe toate cunotinele celorlalte nivele i n plus priceperea icunotinele care s -i permit s proiecteze sau s restructureze supapa de siguran. Folosindexemplu dat se poate observa faptul c dei o persoan de nivel 5 trebuie s aibe aceleaicunotine ca o persoan de nivelul 1, exist diferen de amploare i profunzime. Nivelul 1reprezint o abordare sumar a subiectului, pe cnd nivelul 5 reprezint o abordare n profunzimei acoperirea unei varieti de subiecte adiacente.Diferena dintre nivelul de baz i nivelul 1, este dat de educaie i formare profesional ,activitile de baz fiind repetitive, urmrind proceduri bine stabilite, experiena i cunotineminime de alte domenii Trecerea de la nivelul 1 la nivelul 2 necesit educare i formare la un nivelde competene care s intruneasc Cerinele ocupaionale de nivel 2.


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Fig. 2 Centre recomandate CETOP Fig. 3 Metode recomandate de evaluare

De la nivelul doi la nivelul 3 este necesar o aprofundare a cunotinelor mai mare dect ceanecesar pentru nivelul 2, completate cu alte domenii adiacente hidra ulicii. La nivelul 3,competenele profesionale ar trebui s reflecte n mod clar un nivel de experien, capabil s facfa unei game de activiti numeroase i complexe pentru a respecta atribuiile ocupaionale alacestui nivel.Nivelul 4 i nivelul 5 necesit cunotine i pricepere n alte domenii inginereti i o cunoatereaprofundat a domeniului. Acoperind astfel domenii ca: materiale, calcule de rezisten,matematic, fizic, specificaii tehnice i tehnologii Pentru etapa actuala CETOP a pastrat active doar nivelele 1,2 si 3.

Corelarea pregtirii n Romnia cu modalitile europene de pregtire n Romnia este n derulare un proiect pe programul POSDRU n care se dezvolt o reea deCentre de pregtire i perfecionare profesional, reea ce va fi recunoscut de Forurilecompetente din Europa. Iniiativa va permite angajatorilor s identifice nivelele de competenta,aptitudinile, si cunostinele unei persoane care deine un certificat de competente CETOP, ifurniza o garanie mrit a asigurrii calitii pe parcursul activitii.

Calificrile CETOP trebuie s devin o referin in educarea i formarea n acionrilehidraulice din Europa, i totodat s asigure oportuniti mrite pentru angajri i transfer deaptitudini n interiorul Europei. Responsabilitatea implementrii i managementul armonizariiprogramului (odata dezvoltat i aprobat) va fi a Membrilor Asociaiei CETOP(asociatiileprofesionale nationale in Romania, FLUIDAS). Este recomandat c fiecare membru s

colaboreze cu diver se instituii de invmnt i formare din interiorul rii, ca s se asigure ctoate aspectele de asigurarea calitii, validare i verificarea sunt conforme recomandrilorCETOP.

Intenia este ca fiecare membru CETOP s ating n structura nvtmntului naionalpunctele dorite, oferiind fiecarei organizaii flexibilitate i control total pentru a dezvolta iimplementa modalitile necesare pentru atingerea obiectivului

Membrii asociaiei vor fi, de asemenea, responsabili pentru recomandarea i avizareaorganizaiilor de instruire s realizeze propunerea i s asiste companiile membre n asigurareai suinerea resurselor necesare.


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Fig. 4 Model de implementare a calificrilorCETOP

Fiecare membru CETOP va nmnacertificate individuale care s ateste nivelul de pregtire dobndit. Acestcertificat va reprezenta o calificarerecunoscut pe plan european. Pedurata perioadei de studiu i dedobndire a competenelor, toicandidai vor fi obligai s menin unraport individul de aptitudini. Acestaar trebuii s formeze un portofoliu alcunotinelor i competenelorobtinute, aparinnd niveluluiocupaional personal. Toate acesterapoarte trebuiesc semnate pentruautenticitate i vor deveni bazeledezvoltarii profesionale continue.

Va fi responsabilitatea Centrelor recomandate s asigure informare i indrumare referitor lanevoile personale, luand n considerare noiunile i experiena precedent. Aceasta nu nseamnc o persoan cu nivel ocupational 3 este capabil s urmeze un program de studiu de nivel 3.Persoane diferite, vor avea nevoie de pregtire educaional i profesional diferit depinznd de: a cunotinele actuale, aptitudinile, experiena, i statutul salarial, omer sau angajat b ateptrile angajatorului n funcie de incadrarea la locul de munc sau de aptitudinile dorielalocul de munca (de exemplu: pentru un absolvent n domeniul electronic este necesar ocunotere sumar n domeniul hidraulicii, ncat o instruire de nivelul 1 ar putea satisface nevoilepersoanei respective)Centrele de formare trebuie s asigure oportuniti egale candidailor la toate nivelurile, i sasigure diferite metode de instruire, variind de la:

- Cursuri scurte i module - Program de nvmnt la distan - Studiu personal

In cadrul proiectului PREGATIREA SPECIALISTILOR IN DOMENIILE MECANICII,HIDRAULICII SI PNEUMATICII IN SCOPUL PROMOVARII ADAPTABILITATII SI

CRESTERII COMPETITIVITATII POSDRU/81/3.2/S/47649 , Asociatia Nationala

Profesionala FLUIDAS, partener in cadrul proiectului, a organizat cursuri de hidraulica sipneumatica. Prima grup , pilot,organizata de Fluidas, a susinut cu succes examenul de absolvire a cursului,participanii dovedind o bun ntelegere a teoriei precum i punerea n practic a acesteia, figura 4.

Fig. 4 Instruire pr actic in laboratoare


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Dupa acest curs pilot , am perfecionat metodele de predare i programa astfel nct la cursurileurmtoare s -a putut rspunde prompt cerinelor i problemelor cursanilor.Pe parcursul acestui an, au avut loc i alte cursuri n urmtoarele luni: septembrie i octombrie,figura 5.

Fig. 5 Cursuri septembrie octombrie si instruire practic in laboratoare

Aceste cursuri se adreseaz angajailor din domeniile ce utilizeaz acionri hidraulice ipneumat ice. Surpriza avut de organizatori a fost ca la primele cursuri s-au inscris foarte muliangajati cu preg tire superioar , idea fiind marea lips a lucrtorilor cu pregtire profesionalmedie tehnic in cadrul intreprinderilor. Chiar i n aceast situaie cursul este prezentat la nivelaccesibil tuturor salariailor dornici s devin specialiti n domeniul hidraulicii i pneumaticii.

5. Concluzii n general, la nivel european, Se admite c, gradul de pregtire profesional asigurat de scoalnu spune nimic despre capacitatea unei persoane de a aplica n practic toate sau mcar oparte din cunotinele teoretice acumulate. De aici, decurge nevoia de pregtire profesional , detraining specializat , care s contribuie la mbuntirea capacitii de adaptare a intreprinderilor ia angajailor la realitile tehnologice, ca i la cele economice, spre a -i gsi locul pe o pia amuncii dinamic i competitiv, aa cum este cea actual. De asemenea, nici lucrtorii i nici managerii acestora nc nu au neles importana ecologizriiactivitii i necesitatea aplicrii unor tehnologii de lucru i de mentenan care s permit is asigure evitarea impactului negativ asupra mediului . Un deziderat n plus al activitii de

training pentru mentenana n domeniul acionrilor hidraulice, l constituie aceste noi tendine.


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Un alt motiv, pentru care e necesar training specializat n domeniu , este acela ca la nivelnational nu a existat i nu exist coli pentru lucrtorii din acest mare cmp de activitate i, caurmare, aa -ziii specialiti sunt provenii din personal calificat la locul de munc. Universitatile tehnice trebuie sa ia in mod serios structura specialistilor necesari economieinationale care acum i n urmtorii civa ani vor cere cu precadere ingineri specializati nmentenan i mai puini specialiti n cercetarea i proiectarea echipamentelor. Prin toate cele menionate, trainingul pentru mentenan n FLUID POWER devine tot mai necesardaca se vrea ca domeniul i specialitii si s se adapteze i s se dezvolte i n timp de criz.

BIBLIOGRAFIE1. CETOP education recomandations.. Editor: CETOP Education Commission, 2006.2. Studiu de analiz proiect Pregatirea specialitilor n domeniile mecanicii, hidraulicii i

pneumaticii n scopul promovrii adaptabilittii i creterii competitivitiiPOSDRU/81/3.2/S/47649

3. Petrin DRUMEA editorial HIDRAULICA nr. 1/2008, ISSN 1403-7303.


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MICRO-HYDROPOWER STATION FOR KINETIC ENERGYCONVERSION OF FLOWING WHATER

Ion BOSTAN, Valeriu DULGHERU, Viorel BOSTAN, Anatol SOCHIREANU, Oleg CIOBANU,Radu CIOBANU

Technical University of Moldova, 168, tefan cel Mare str., Chiinu, 2004, Republic of Mo ldova

Abst ract - An efficient conversion of kinetic energy of river water into mechanical or electricalenergy without building barrages is provided by micro-hydropower stations. Increased efficiency isachieved by an optimum position of the blades with hydrodynamic profile. The formulation used tocompute the hydrodynamic forces is an inviscid boundary layer model. Micro-hydropower stationprovides kinetic energy conversion of river water into mechanical or electrical energy withoutbuilding barrages. Increased efficiency is provided by blades aerodynamic profile and theiroptimum position for efficient conversion of water kinetic energy. Two industrial prototypes arefabricated. The efficiency of the micro-hydro power stations as conversion systems of renewableenergy sources kinetic energy of flowing rivers depends mostly on profiles of the hydrofoils used inthe rotors construction for interaction with fluid. The main goal of this paper consists in theelaboration of the modified hydrofoils, and based on them of the turbines with increasedconversion efficiency. The following objectives were established: Elaboration of the transientcomputational models of the hydrodynamic turbine with 3 and 5 hydrofoils for extensivesimulations in the framework of computational fluid dynamics (CFD) using software applicationsICEM CFD, CFX, TurboGrid and ANSYS, that will allow a variation of the attack angle for eachindividual blade during a full rotors revolution.

Expected results: Elaboration of the technical and technological documentations,manufacturing and testing of the hydrodynamic rotor for the micro-hydro power station.

Key words: water wheel, hydrodynamic profile, micro-hydropower station.

1. INTRODUCTION

The existence of water on the Earth hasconditioned the emergence and development oflife. From the times immemorial, man haschosen a place to live near rivers and lakes to

meet their natural needs in water, but also forcarrying out basic irrigation works. Floating orrowing led human thought by observation, touse water force and energy. Thus, themechanical power of running water can beconsidered one of the oldest tools.The means of water use and exploitation haveevolved from a historical epoch to another, fromone nation to another, in relation to the naturalconditions, depending on the level of productionrelationships and forces. Thus, water energyuses has marked stages of development of the

social systems from the primitive to modernsociety.

Figure 1: Conceptual diagram of the water wheelwith rectilinear profile of blades


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To avoid the construction of dams, the kinetic energy of rivers can be utilised by means ofexploiting water stream turbines. This type of turbines is easily mounted, is simple in operationand maintenance cost is suitable. The 1m/s current velocity represents an energetic density of500W/m 2 of the crossing section, but only a part of this energy can be drawn off and convertedinto useful electrical or mechanical energy. This fact depends on the type of rotor and blades.Velocity is especially important as a double increase in the water velocity can result in an eighttimes rising of energetic density. Prut river has a section equivalent to 60 m 2 and an averagevelocity in explorable zones of (1 1,3) m/s, which is equivalent to an approximate theoreticalenergy of (30 65) kW. Taking into account the fact that the turbine can occupy only a portion ofthe river bed the generated energy might be much smaller. There are various conceptualsolutions, but the issue of increasing the conversion efficiency of water kinetic energy is in theview of researchers. The analysis of constructive versions of floatable micro-hydro power stationspreviously examined did not satisfy at all from the point of view of conversion efficiency of waterkinetic energy. In a classical hydraulic wheel horizontal axle (Fig. 1) [1] the maximum depth atwhich one of blades is sunk makes approximately 2/3 of the blade height h. Namely, only this areaparticipates in the transformation of water kinetic energy into mechanical one. As well, the priorblade covers approximately 2/3 of the blade surface sunk utmost in the water (h 2/3h) . This factreduces significantly the water stream pressure on the blade. The blade that comes next to theblade that sunk maximally into water is covered completely by it and practically does not participatein the conversion of water kinetic energy. Therefore, the efficiency of such hydraulic wheels issmall.The insistent searches of authors lead to the elaboration and patenting of some advancedtechnical solutions for floatable micro-hydro power stations, based on the hydrodynamic effect,generated by the hydrodynamic profile of blades, and their orientation at optimum positionsconcerning the water streams with account of energy conversion in each phase of the turbine rotorrotation (Fig. 2) [1,2].

Figure 2: Conceptual diagram of the rotor with hydrodynamic profile of adjustable blades concerning thewater streams.

Therefore it was necessary to perform a large volume of multi-criteria theoretical researchconcerning the selection of optimum hydrodynamic profile of the blades and the design of theorientation mechanism towards the water streams.


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2. CONCEPTUAL DIAGRAM OF THE MICRO HYDROPOWER PLANT WITH HYDRODYNAMICROTOR

The results of the carried out research by the authors concerning the water flow rate in thelocation selected for the micro-hydro power stations mounting, the geological prospecting of theriver banks in the place of anchoring foundation mounting, the energetic needs of the consumingpotential, represent initial data for the conceptual design of the micro-hydro power stations and itsworking element.

Aiming at an increase of the conversion coefficient of the water kinetic energy (Betz coefficient), anumber of structural diagrams of floatable micro-hydro power plants have been designed andpatented [2-7]. They comprise a rotor with pintle and vertical blades, and hydrodynamic profile innormal section. The blades are interconnected by an orientation mechanism towards the directionof the water streams. The motion of rotation of the rotor with pintle is multiplied by a mechanicaltransmission system and is transmitted to an electrical generator or to a hydraulic pump. Thementioned knots are fixed on a platform, mounted on floatable bodies. The platform is linked to thebank by a hinged metallic truss and by straining cables.

A very important aspect in the functional optimization of micro-hydro power plants is the selectionof optimum hydrodynamic profile of the blades which allows increasing the conversion coefficient(Betz coefficient). Due to the hydrodynamic upward forces the increase in the conversion level isreached by means of ensuring the optimum position of the blade towards the water streams invarious phases of rotor rotation by utilizing blades orientation mechanism. Thus, practically allblades (even those which move opposite the water streams) participate simultaneously in thegeneration of summary torque moment. The blades which move along the water streams utilizeboth hydrodynamic forces and water pressure exercised on blade surfaces for the generation ofthe torque moment. The blades which move opposite the water streams utilize only hydrodynamicupward forces for the generation of the torque moment. Due to the fact that the relative velocity of

the blades toward water streams at their motion opposite water streams is practically twice bigger,the hydrodynamic upward force is relatively big and the generated torque moment is measurable tothe one generated by the water pressure. This effect forms the basis of all patented technicalsolutions.The adopted technical solutions have resulted in an ample theoretical and experimental researchcarried out at the Centre for Renewable Energy Conversion Systems Design, Department of theTheory of Mechanisms and Machine Parts. To justify the constructive and functional parameters,supplementary digital modelling and simulation have been carried out by utilizing ANSYS CFX5.7software. Subprograms developed by authors for the MathCAD, AutoDesk MotionInventor, etc.software, have been utilized, namely simulation of the interaction flow-blade of the floatablesteadiness and also the optimization of blades hydrodynamic profile, with the purpose to increasethe river water kinetic energy conversion efficiency for different velocities by using 3, 4 and 5 blade

rotors. In the process of micro-hydro power plants design, the experience gained at research-design-manufacturing of the pilot plant was utilized.The efficiency of micro-hydro power plant operation by private consumers for special purposesdepend on the right selection of micro-hydro power plant constructive configuration and of thefunctional characteristics of the component aggregates participating in the process of flowing waterkinetic energy conversion into useful energy. In order to satisfy the objectives and consumersdemand for micro-hydro power plants, and also for the increase in the flowing water kineticpotential conversion efficiency in the certain zone of the river, the authors have designed variousconstructive and functional concepts based on modular assembling. The mentioned micro-hydropower plants, conceived as modular ones, allow the modification of destination and functionalcharacteristics by replacing certain aggregates with other (generator, pump, blades with differenthydrodynamic profile, 3-5 blades rotor).Micro-hydro power plants have similar resistance structure as constructions calculated from thepoint of view of resistance and rigidity at dynamic demands. Floatability and maintenance of theperpendicularity of micro-hydro power plant rotor spindle for a variable river water level are


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ensured by technical solutions protected by patents [3-7]. The instant orientation mechanism ofblades for a constant entering angle concerning the direction of the water flow represents Know-How and it is not described. The main working element on which the quantity of kinetic energyconverted into useful energy depends is the blade with the hydro-dynamic profile NACA 0016,developed on the basis of the performed digital modelling. Two types of rotors with 3 and 5 bladeshave been designed for the mentioned micro-hydro power plants. The installed capacity of micro-hydro power plants with diameter D = 4 m , water-submersed blade height h = 1,4 m and the lengthof the blade cord l = 1,3 m for water flowing velocity V = 1...2 m/s can be within P =2...19 kW .In micro hydro power plant (Fig. 3) [3] the turbine 1 comprises blades 2, executed with thehydrodynamic profile and mounted on the axles 3, fixed by their upper part on the extreme ends ofthe bars 4, with the possibility to rotate around their axles. The position of the blades 2 at angle to the direction of water flow is ensured by the controlling mechanism 5. Platform 6 is consolidatedadditionally by a winch 7 fixed on the truss that is mounted unshiftable on the shore pillar 8. Theturbine 1 and the blades 2 are placed in the river water flow. The floating bodies 9 and the hollowblades 2 themselves control the position of turbine 1 and blades 2 concerning the water level. Themulti-blade rotor is connected cinematically and coaxially to the electric generator 11 by themultiplier 10. The winch 7 is used for turbine 1 maintenance which fact requires its removal fromthe water. The blade 2 is positioned under angle towar ds the water flow; it changes dependingon the blade position to the water flow direction.

Figure 3: Floatable micro hydropower plant with blades orientation mechanism

The components of force F, acting on the blade, are determined from the relationships:2

2 x xv

F C S = ,

2

2 y yv

F C S = , (1)

where: is water density; v is the water flow linear velocity; s is the blade surface; C x, C y are liftand drag (resistance) coefficients of the blade profile. Coefficients C x and C y depend on the bladeentering angle (the angle between the blade and the water flow direction) and on the profileshape. The angle is determined either experimentally or by numerical calculations. The torquedeveloped by one blade is described by the equation:


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(cos sin )2 2 y xd d

M F F F

= = , (2)

where F is the projection of force F on the tangent drawn to the path of motion of the blade axis.

The summary torque includes the general component of the resistance force F h . The torquemoment generated by the turbine consists of the torques generated by each separate blade.Currently only one blade will not generate positive moment (it will generate a negative moment the resistance one). Thus, the torque generated by the proposed turbine will be essentially biggerthan the torque produced by the existing turbines for the same geometrical (blades dimensions)and kinematical parameters of water. The proposed micro hydro power plant allows thetransformation of the water flow kinetic energy into mechanical or electrical energy with anincreased utilization coefficient of water energy.

3. INDUSTRIAL PROTOTYPE OF MICRO-HYDRO POWER PLANT WITH HYDRODYNAMICROTOR

The micro-hydro power plant for river water kinetic energy conversion into electrical andmechanical energy (Fig. 4) [1,2] is poli-functional and can be utilized for street illumination, heating,water pumping for irrigation by weeping, for drainage of agricultural areas adjacent to rivers. Theassembling of blades 1 with NACA 0016 profile in hydrodynamic rotor 2 and its mounting on theinlet shaft of the multiplier 3 are done in the same manner as for micro-hydro-power plant. Thekinematics and constructive peculiarities of micro-hydro plant are the following: rotation motion ofhydrodynamic rotor 2 with angular speed 1 , by means of multiplier 3 and of belt drive 4 having aneffective multiplying coefficient i = 212,8, is being multiplied up to angular working speed of thegenerator with permanent magnets with small rotations 5: 3= 1 i1 (s -1).

Torque moment T3 , applied to rotor 5, is:

1 1 2 r 3

T T ,( Nm )

i = ,

where: 1 is the mechanical efficiency of the multiplier ( 1 = 0,9) ; 2 - mechanical efficiency of the belt drive ( 1 = 0,95) ; r - mechanical efficiency of the hydrodynamic rotor bearings ( 1 = 0,99) .i effective multiplication coefficient equal to the composition of multiplying ratios of the

planetary multiplier and of the belt drive.

The electric energy produced by the generator with permanent magnets 5 (fig. 4,5) can be utilizedboth for private consumer needs of power and for supplying electricity to impeller pump 6 (CH

400), for water pumping into irrigation systems by means of weeping or drainage of agriculturalareas adjacent to the rivers (by relocation of the impeller pump 6).

In the fig. 6 the dependence of the torque moment T 1 at hydrodinamic rotor shaft at one rotation ispresented. In the case of electric energy production, the energy utilization efficiency with accountof mechanical losses in the kinematics chain of the micro-hydro power plant and in the generatorwith permanent magnets makes up (at generator terminal):

1 2 r g 0,9 0,95 0,99 0,87 0,736, = = =

and in case of water pumping (at the shaft of the pump):

1 2 r g me 0,9 0,95 0,99 0,87 0,91 0,67, = = =

where: g is generator efficiency;


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me efficiency of the hydraulic pump of the electric motor.

Figure 4: Micro-hydro power plant with hydrodynamic rotor river water kinetic energy conversion intoelectrical and mechanical energy (rotor diameter D = 4m , water-submersed blade height h = 1,4m ,

length of the blade cord l =1,3.

Water flow

Pump CH-400

Q=(20...)40m -3 /h

Planetarymultiplicator i=112

Repression

Aspiration

33

Figure 5: Micro-hydro power plant kinematics.

On the basis of the conceptual diagram designed above, technical documentation was developedindustrial prototype of micro-hydro power plant for river water kinetic energy conversion intoelectrical and mechanical energy was manufactured (fig. 7). Thus, micro-hydro power plantprovides conversion of up to 73,6% and 67% of useful energy for electricity production and forwater pumping from the energy potential of flowing water entrapped by the hydrodynamic rotor.Now, the industrial prototype of micro-hydro power plant is tested on the test area on the Prut river,c. Stoieneti , Cantemir (fig. 8).


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Figure 6. Torque moment T 1 at hydrodinamic rotor shaft with NACA 0016 profile blades.

Figure 7: Industrial prototype of micro-hydro powerplant for river water kinetic energy conversion

Figure 8: Testing of the industrial prototype ofmicro-hydro power plant on the Prut river.

CONCLUSIONS

In conclusion, we state that micro hydropower plants ensures the transformation of 7086 % ofthe flowing water potential energy into useful electrical energy transmitted to the hydrodynamicrotor. The basic advantages of micro-hydro power stations are as follows:

- small impact on the environment; it is not necessary to carry out civil constructions;- the river does not change its natural course; the possibility to utilise local knowledge in

order to produce floatable turbines;

- the possibility to mount a series of micro-hydro stations at small distances (approximately30-50 m) because the influence of turbulence provoked by the adjacent installations can beexcluded.

REFERENCES:

[1] Bostan I., Dulgheru V., Sobor Ion, Bostan V., Sochirean A., (2007), Systems for Renewable Energies Conversion: eolian, solar andhydraulic (in Romanian), Ed.: BonsOffices SRL, 592pp.

[2] Bostan I., Dulgheru V., Bostan V. , Ciuperc R. (2009), Anthology of Inventions, vol. 3. Systems for Renewable Energies Conver sion(in Romanian). Ed.: BonsOffices SRL, 458pp.

[3] Bostan I., Dulgheru V., Bostan V., Ciobanu O., Sochireanu A., (2006), Hydro-electric plant. Patent MD Nr. 2991 .[4] Bostan I., Dulgheru V., Sochireanu A., Bostan V., Ciobanu O., Ciobanu R., (2006), Hydro-electric plant. Patent MD Nr. 2992 .[5] Bostan I., Dulgheru V., Bostan V., Sochireanu A., Trifan N., (2006), Hydro turbine. Patent MD Nr. 2993 .[6] Bostan I., Dulgheru V., Bostan V. Sochireanu A., Ciobanu O., Ciobanu R., Dicusar I., (2006), Hydro -electric plant. Patent MD Nr.

3104.[7] Bostan I., Dulgheru V., Bostan V., Sochireanu A., Ciobanu O., Ciobanu R., (2009), Hydro-electric station. Patent MD Nr. 3845 .


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EXPERIMENTAL RESULTS REGARDING ROTATIONAL SPEED OF THE

ALTERNATING FLOW DRIVEN HYDRAULIC MOTORS WITH A STARINTERCONNECTION OF THE WORKING VOLUMES

Ioan-Lucian MARCU 1, Daniel- Vasil e BANYAI 2, Claudia KOZMA 3, Gabriela MATACHE 4 1 Technical University of Cluj-Napoca, [email protected] [email protected] [email protected]

4 Hydraulics & Pneumatics Research Intsitute, Bucharest ROMANIA, [email protected]

Abst ract: The presents aspects regarding the theoretical aproach and experimental results on thethe speed of the rotation of an alternating flow driven hydraulic motor having a star interconnectionof the working volumes. The mathematical model is developed considering the alternant flowsfunction of the generator driving speed, the constructive parameters of the whole system,considering the elasticity of the phase pipes and the oil column compressibility under pressure.There are presented diagrams between the curves of the obtained theoretical speeds and thecurves obtained by experimental results interpretation, which are validating the elaboratedmathematical model.

Keywords : alternating flow, three-phase hydraulic motor, rotational speed, star interconnection

1. Introduction

Alternating flow driven systems involves a new approach of the driving systems using pressurizedliquids, because we have here, in the entire system, along the pipes, an energy transmissionswithout volumetric flow transportation between the energy converters, hydraulic generator andhydraulic motor. [1], [2], [3], [4], [5]

Generally, an alternating flow driven hydraulic transmission consists in a alternating flows andpressures generator and a motor, the connection between them being realized with a number ofpipes equal with the number of phases, the pipes being filled with fluid at a certain (pre-established) pressure. During the functioning of the system the pressure and the flow within eachpipe varies in a sinusoidal way, around an average value.

Within these systems, the active stroke of the hydraulic motor pistons, is produced by thepressurized fluid flow from the generator, while, for the retraction stroke there is necessary asupplementary connection (in a star configuration for example) to a pressure generator, working inopposite phase with respect to the first one.

2. Theoretical approaches regarding t he rotational speed of the hydralic motor

Considering the constructive characteristics of the hydraulic generator and motor, and using themedium flow formula, we can calculate the rotational speed of the output shaft of the hydraulicmotor as follows. [1], [2]

The medium value of the volumetric flow for a phase of the hydraulic generator, for an active

angle 12 ggg = , is defined using the equation:


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=2

112

1g

g

g ggigg

imed dQQ

1

The instantaneous volumetric flow is defined as:

)sin(2 0

+= tSx

Q gg

gi 2

in which gx is the generator piston stroke, gS is the generator piston surface, and g is the angular

frequency of the generator.

The effective volumetric flow eQ is influenced by the capacitive flow iCQ , like figure 1 present:

iCie QQQ = 3

Figure 1. Influence of the capacitive flow on the instantaneous flow [5]

If we consider that the capacitive flow is a "negative flow", then the medium value of the volumetricflow which reaches to the hydraulic motor is:

( ) =2

112

1 g

g

med gCiigg

e dQQQ

4

Taking into account the constructive characteristics of the flow driven hydraulic generator andmotor, the interconnection pipes, the elasticity of the oil and also of the pipes, the rotational speed

mn of an alternating flow driven three-phase hydraulic motor, with a star interconnections of theworking volumes, can be expressed using the formula:

1

5,15,211

4433

max2

2

2

int

intint

+

+= a

c

c

c

c

pipeoil

ccgg

mm

gm p

d

d

d

d

EE

ldSx

Sr

nn

ext

ext

5

in which gn is the rotational speed of the hydraulic generator and maxap is the amplitude of the

pressure along the interconnection pipes.


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In figure 2 are presented the principles of the star interconnection working volumes for analternating flow driven three-phase hydraulic motor.

Figure 2. The principles of the star interconnection of the hydraulic motor working volumes.

Schematically the interconnections of the working volumes are presented in figure 2m in which:- 1, 2, 3 - phase pipes;- MHL 1 , MHL 2 , MHL 3 - linear hydraulic motors;- Q i1 , Q i2 , Q i3 - the instantaneous volumetric flows of the three phases;- p i1 , p i2 , p i3 - the instantaneous pressures of the three phases.

Each hydraulic linear motor will act individually on the output shaft of the hydraulic motor.

The instantaneous flow of the three-phase hydraulic generator, which provides the active stroke fora linear hydraulic motor is equal with the instantaneous flow generated by the motor pistonsmovement, and which is provide also the retraction stroke for the next two pistons. So, like thefigure 2 shows, we can define the equation:

121311 iiii QQQQ star +== 6

in which Q i13 and Q i12 are the volumetric flows providing the retraction strokes of the MHL 2 andMHL3 hydraulic motors.

Similarly the relations defining the flows for the next two phases, when those are actives,can be written as::



This type of interconnection of the hydraulic motor working volumes is characterized by a null sumof the instantaneous three-phase volumetric flow in the connection point:

03

1

= iQ 9


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In figure 3 is presented the alternating flow driven hydraulic motor with a star interconnectionworking volumes.

Figure 3. The star interconnection of the hydraulic motor working volumes. [1]

3. Experimental results

The designed version of the three-phase alternating flow driven hydraulic motor included in theexperimental strand is schematically presented in figure 4.

Figure 4. The schematic representation of the experimental stand, having a star

interconnection for the motor working volumes. [1]


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The components of the hydraulic system presented in figure 4 are:

1 - continuous current electric motor;2 - axial pistons flow generator;3 - auxiliary oil tank;4 - manual screw pump;5 - vanes;6 - capillary hydraulic resistances;7 - hydraulic accumulator;8 - alternating flow drive hydraulic motor;

9 - manometer;10 - braking device;11 - proximity sensors;12 - pressure sensors;13 - displacement sensor;14 - phase pipes;15 - interconnection pipes;16 - secondary hydraulic ramification

In order to acquire the experimental data during the testing process we had to precisely control themechanical and hydraulic parameters using proximity sensors mounted on the rotation shafts,pressure sensors mounted on the representative points of the hydraulic pipes and displacementsensors mounted on the motor cylinder pistons, figure 4.

The monitoring protocol of the entire system was established using an input/output parametersdiagram. The preliminary experimental data, representing the functional parameters, were obtainedconsidering the monitoring protocol, the sensors disposition and using a data acquisition board.The large amount of information was reviewed and processed afterwards, taking into considerationeach particularly mechanical configuration and input adjustments.

In figure 5 and figure 6 are presented some comparative diagrams obtained using the experimentaldata and the numerical simulation application developed by using the mathematical model.

The mathematical model was developed considering the two energy converters, hydraulicgenerator and hydraulic motor, the compressibility of the oil column and also the elasticity of the

connections pipes. Another condition was that the volumetric flow provided by the generator istotally used by the hydraulic motor

0

2040

60

80

100

120

0 200 400 600 800 1000

Generator rotational speed [rpm]

M o t o r r o

t a t i o n a

l s p e e d

[ r p m

Real speed Theoretical speed

Figure 5. Motor rotational speed evolution: star interconnection schema, generator piston

stroke 8 mm and initial static pressure 25 bar.


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4. Conclusions

The objective of this research was a new approach of the hydraulic drives, in which the pressureand flow is not continuously transmitted between the energy converters (pumps and motors). Thepaper describes the constructive principles of the alternating flow driven hydraulic systems, andalso its main components.

The experimental results, combined with the developed mathematical model of this system,demonstrates the possibility to adjust, during the functioning, several input parameters (like theinitial static pressure and the generator angular speed), in order to obtain the anticipated outputvalues of some parameters, or if the system load is modifying.

REFERENCES

[1] Marcu, I. L., "Researches and contributions regarding the functional improvements of the alternating flowdriven hydraulic systems", PhD Thesis, Technical University of Cluj-Napoca, 2004.

[2] Marcu, I.L., Pop, I. Interconnection possibilities for the working volumes of the alternating hydraulicmotors Proc. of the 6th International Conference on Hydraulic Machinery and Hydrodynamics -HMH2004 in Trans. of Mechanics, Tom 49 (63), Timisoara, October 2004, ISSN 1224-6077, pp. 365-370.

[3] Pop, I., Marcu, I.L., Khader, M., Denes Pop, I., "Conventional Hydraulics", Ed. U.T.PRES, Cluj-Napoca,1999.

[4] Pop, I., "Sonic Theory Treatise", Ed. Performantica, Iasi, 2006.[5] Pop, I. et al, "Sonics Applications. Experimental Results ", Ed. Performantica, Iasi, 2007.

0

20

40

60

80

100

120

0 100 200 300 400 500 600 700 800Generator rotational speed [rpm]

M o t o r r o

t a t i o n a

l s p e e d

[ r p m

Real speed Theoretical speed

Figure 6. Motor rotational speed evolution: star interconnection schema, generator pistonstroke 12 mm and initial static pressure 25 bar.


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NUMERICAL SIMULATION OF THE SERVO MECHANISM

FOR ADJUSTING THE CAPACITY OF THE RADIAL PISTON PUMPS

Liliana DUMITRESCU 1, Ctlin DUMITRESCU1 Ioan LEPDATU1 1 INOE 2000 - IHP e-mail address: [email protected]

Abst ract: The paper presents the simulation of static and dynamic behavior of system capacitycontrol radial piston pumps using the program AMESim.

Keywords : simulation, pumps, rung signal, sinusoidal signal

1. IntroductionTo analyze the static and dynamic behavior of the control system capacity of radial piston pumps,was used a powerful and performant graphical program, AMES / Imagine. For the composition ofthe simulation models were used standardized symbols specific hydraulic elements existing in thelibrary program.

AMESim is a simulation environment built on multiport considerations. The exchange ofinformation between the components is bidirectional and thus made fewer lines of communication.

At the same time the simulation environment shapes almost exactly real models of the dynamicsystems simulated. Another important feature of the program is the automatic choice of the methodof integration of the systems of equations that can be adapted during simulation according to thecharacteristics of equations.

From the user point of view, the program is a suggestive graphical interface that displays theevolution of the whole system during the simulation process.

2. Structure for simulation of servo

In fig. 1 is shown the structure for simulation of servo positioning. It is then specified thecorrespondence between the components of the simulation model and the physical modelelements [1]. The analyzed system is the real mechatronic control system eccentricity / flow, whichis composed of:- Electro-hydraulic proportional distributor 4/3 with center closed - Item 8;- Supply group with oil under pressure - Item 3, 4 and 2;- Tank - Item 1;

- Position transducer - Item 13;- Compensator - Item 16;- Linear hydraulic motor + inertial load + viscous frictions - Item 14, 15, 11, 10 and 12;- Signal generator - Item 7.


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Fig.1 The network for simulation of the servo control of radial piston pump capacity

Their correspondence with the real control system eccentricity is shown in Fig. 2. For an easyidentification it was complied the numbering of positions from Fig. 1.


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Fig. 2. Physical structure of the positioning system for adjusting the eccentricity

In these pictures are distinguished in the following:1. tank; 9. small piston chamber ;2. pressure limiting valve ; 10. small piston spring ;

3. Volumetric pump 11. piston with small area ;4. electric motor; 12. inertial mass (sliding ring); 5. electromechanical converter ; 13. inductive position transducer; 6. electronic compensator; 14. piston with large area; 7. the command prescription channel; 15. piston spring with large area; 8. proportional distributor body ; 16. large piston chamber.

3. Static and dynamic characteristics of the syst em

To determine the static and dynamic characteristics of the system, it was controlled by triangular

electrical signals voltage step and sinusoidal type in the field (0 ... 10) V DC. Frequency signal,type ramp was chosen small enough to generate a quasi-static regime.The were obtained featuresfrom simulation which are presented in Fig. 3....7, the monitored parameter at the (output of the)system output being eccentricity, whose values, when used as an experimental model pump is:

( ) .5... mme =


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Fig. 3. System response to the ramp signal, frequency 0.1 Hz

Fig. 4. System response to sinusoidal signal, frequency 0.1 Hz

R e p

l y o

b t a i n e

d b y s

i m u

l a t i o n , e

R e p

l y o

b t a i n e

d b y s

i m u

l a t i o n ,

e

C o m m a n

d p r e s c r

i b e

d U c

C o m m a n

d p r e s c r i

b e

d U c

command

simulatedreponse

commandsimulatedreponse


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Fig. 5. Static characteristic, frequency of 0.05 Hz

Fig. 6. Response to the signal rung

C

o m m a n

d p r e s c r

i b e

d U c

R e p

l y o

b t a i n e

d b y s

i m u

l a t i o n , e

CommandSimulated

R e p

l y o

b t a i n e

d b y s

i m u

l a t i o n ,

e

Command prescribed Uc


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Fig. 7. Bode diagram

4. Conclusions

All features obtained using AMESim program, have very small deviations between the commandand simulation which means that the obtained results simulate with a very good accuracyfunctioning of the control eccentricity system.Considered the reference, the results obtained by numerical simulation will be validatedexperimentally. Experimental research results and comparison with the simulated results will bepresented in another article.

REFERENCES

[1] I. Lep datu , Theoretical and applied research on mechatronic systems adjusting the flow of hydraulicrotary generators by eccentricity, U.P.B. Doctoral Thesis, 2010.

[2] M. Blejan, B.Lupu, I.Dutu, D.Rotaru, T.C.Popescu - ELECTRONIC OSCILLATOR FOR A HYDRAULICFLOW DIVIDER - 32 nd International Spring Seminar on Electronics Technology ISSE 2009 BRNO, CZECHREPUBLIC[3] A. Mirea, A. Marin, G.Matache, I. Dutu - THE THEORETICAL AND EXPERIMENTAL STUDYS ABOUTTUNIG OF THE DISPLACEMENT UNITS WHIT THE HYDRAULIC ACTUATION - SIITME 2006 - THE 6 TH INTERNATIONAL SYMPOSIUM FOR INFORMATICS AND TECHNOLOGY IN ELECTRONIC MODULESDOMAIN

The phase shift characteristicobtained by simulation

The amplitude characteristicobtained by simulation

P h a s e s

h i f t ( g r d

)

A m p

l i f i c a

t i o n

( d b )


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CONSIDERATIONS ABOUT DIGITAL PID CONTROLOF ELECTRO-HYDRAULICS EQUIPMENT

Iulian DUU1, Radu RDOI2, Gabriela MATACHE 3

1Hydraulics and Pneumatics Research Institute, Servo and Electronics Compartment, Bucharest Romania,[email protected] 2Hydraulics and Pneumatics Research Institute, Servo and Electronics Compartment, Bucharest Romania,[email protected] 3Hydraulics and Pneumatics Research Institute, Special Equipments Compartment, Bucharest Romania,[email protected]

Abst ract: Classic hydraulic systems offer a sum of advantages such as robustness and easyadaptability to some variations of the working environment, being capable of realizing high forceand torque values at relatively low costs of implementation and maintenance. The global evolutionof electronics and informatics fields had influenced positively hydraulic researches on developingnew types of equipment, tending to facilitate an easy integration with digital controllers of computercontrolled systems. It has been imposed the concept of intelligent hydraulic equipment, whichinclude in their structure digital electronic modules (with self-diagnosis, auto-adjustment and buscommunication features) and specific transducers. These improvements had a positive effect onthe dynamic characteristics of electro-hydraulic equipment, some of them being known in technicalliterature as intelligent electro-hydraulic equipment.

Keywords: electro-hydraulics, digital PID, driving systems

1. IntroductionElectro-hydraulic systems are widely used nowadays, being the most suitable solution for powertransmission over a certain distance, control and flexibility because of the technologicaldevelopments in high precision industrial systems such as robotics, multi-axis control and 3Dpositioning applications. Classical approaches to a certain problem are still used in industry, butthere are some applications that need digital electronics control along with IT solutions. Mainly, thearchitecture of electro-hydraulic driving systems include software components and IT technologies,digital and analog electronic modules and, of course, the electro-hydraulic equipment themselves.This kind of approach facilitates the measurement and acquisition of systems working parameters,trying to correlate the output control signal with program reference signal and environmentalfactors (such as temperature, vibrations, perturbations and so on) thus obtaining a low error andhigh positioning accuracy. Also, the flexibility of the electro-hydraulic drive is one important factorbecause the control system itself can adapt to new requirements not needing, in most cases, ahardware reconfiguration which is expensive.

2. Why choos ing electro-hydraulic systemsChoosing the best drive system for an industrial application is not an easy task - the systemsengineer must take into consideration various technical, functional, environmental or reliability

criteria [1]. Basically, hydraulic drives can be classified into two major categories: hydrostatic andhydrodynamic power systems.
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Hydrodynamic systems functioning is based on increasing the kinetic energy of the working fluid,usually mineral oil, having a high power-weight ratio, improved controllability but there are mostlylimited to rotary motion.

Hydrostatic systems transmit power by increasing the pressure of the working fluid, being the mostused type of drive system in industry, aviation equipment or heavy machinery control. Mainbenefits of hydrostatic drive systems are protection against overloading, energy storagecapabilities (accumulators), high power/weight ratio, increased stiffness of cylinders and lubricationthrough working fluid.The need for accurate positioning systems based on electronics and hydraulicsequipment/modules, leaded to the establishment of electro-hydraulics field using proportional andservo devices. These kinds of systems put together the advantages of hydraulic drive systems andelectronic modules: accuracy, precision, controllability, high power/weight ratio and stiffness.Mainly, electro-hydraulic equipment is dived into: digital valves, servovalves, proportional valvesand ON/OFF valves. Electro-hydraulic equipment has high static and dynamic performances, thusoffering optimal solutions for certain industrial applications and sometimes being the only availablesolution for complex drive and control issues[5]. Current trends in improvement of electro-hydraulicequipment imply continuous increasing of static and dynamic performances along with loweringmanufacturing and running costs. These all can be realized by putting together various technicalfields such as mechanics, electronics, control engineering and IT. Various manufacturers ofelectro-hydraulic equipment tend to offer fully integrated solutions made of transducers, controllers,displays and the electro-hydraulic equipment itself.

3. A few considerations on digital PID controllersElectro-hydraulic drives can be regarded as mechanical transmission systems from a powersource towards actuators, using a pressurized fluid as transmission mean, and can be classifiedinto three major categories, as follows:

- electro-hydraulic control systems;- command systems for external high power equipment;- driving system, having the sole role to transmit mechanical energy without having control

over the quantity and parameters of working fluid.By including electro-hydraulic equipment into a drive, the systems engineer obtains high static anddynamic performances using only an electrical control current that ranges between 200800 [mA]for proportional equipment and between -8080 [mA] for servovalves[4]. Widespread of computertechnologies and digital electronic control systems along with high-integration of electronic

components, allowed the manufacturers to develop new types of electronic modules that can beincluded into the structure of electro-hydraulic equipment.PID (Proportional-Integrative-Derivative) control algorithm [2,3] has the following analogmathematical expression:

(1)

Using the finite difference approximations on the PID equation given above (1), we will obtain thedigital equivalent:

(2)

(3)


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Closed loop control (Figure 2) represents a system where the interest parameter is measuredpermanently by using a transducer and automatically adjusted by the electronic controller in orderto equal the output and setpoint signals. The transducers signal is usually called feedback,allowing permanent automatic adjustment of the output signal in order to obtain prescribedhydraulic parameters.Main elements of modernization were made combining electronic digital modules and hydraulics,allowing varying mechanical parameters such as speed, force or torque through electronic controlof hydraulic parameters in the electro-hydraulic system. Hydraulic control through electronicmodules has changed ON/OFF electro-hydraulic valves into proportional and servo equipment.Furthermore, by combining hydraulics, electronics, sensors and informatics it was obtained newand more accurate driving systems based on mechatronics concepts.

Figure 2 Closed loop electro-hydraulic system (example)Main components of any closed loop hydraulic control system are the electronic controller andelectro-hydraulic adjustment equipments that have improved over time having two structural andfunctional directions: servo and proportional equipment. In servos the electro-mechanic convertoris generally a torque motor, capable to work at relatively high frequency. In proportional equipment,

the electro-mechanic convertor is a proportional electromagnet capable to work at mediumfrequencies. These differences in functional performances have an influence on purchase andmaintenance costs.Usually, automated electro-hydraulic control systems are based on translation unit architectureusing an electric signal as command input. Their controller uses the difference usually called error- between the setpoint and feedback signals, the structure being represented by a block diagramresulted from a set of differential equations or from the transfer function equation (when it isneeded to perform the transient and stationary analysis of the output signal for small variations ofthe setpoint).

5. ConclusionsDigital control of electro-hydraulic equipment is considered to be a complex technical field, whichinvolves mechanics, hydraulics, electronics and informatics. When choosing a digital controlsystem for a specific industrial application, systems engineer must analyze thoroughly existingsolutions and define correctly interest parameters and their way of variation and must take intoconsideration practical aspects along with manufacturing and maintenance costs.Digital electronics and informatics technologies combined simplify implementation andreconfiguration of industrial electro-hydraulic systems, by using specific sensors and transducers,data acquisition boards, virtual instrumentation and so on.Future developments on digital electro-hydraulic field include an even more miniaturization ofequipments, due to advanced researches on materials and electronics fields (such as using highintegration SMD components).

-+

Adjustable

setpoint Electroniccontrol module

Electro-

hydraulicadjustmentequipment

Constant

output value

Perturbation

Hydraulicactuator

Transducer


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6. References[1] Duminic, D., Avram, A., Alexandrescu, N ., Stadiul actual n domeniul acionrilor hidronice, Simpozionul

Relansarea i creterea competitivitii sectoarelor economice din industria prelucrtoare, Bucureti,23-24 septembrie 2004, n volumul confer inei.

[2] Flaus, J. M ., La rgulation industrielle. Rgulateurs PID, prdictifs et flous, Editions Herms, Paris, 1994.[3] Guillon, M ., Commande et asservissement hydrauliques et electrohydrauliques, Editions Lavoisier, Paris,

1996.[4] M. Comes, A. Drumea , Tehnologie de realizare a modulului electronic PID pentru distribuitoare hidrauliceproporionale cu electronic integrat, Prima Conferin a Hidroenergeticienilor din Romnia, 26-27 Mai2000, Bucureti, Romnia, ISBN 973-652-144-3, pp. 611-614.[5] D. Ion Gu, I. Lepadatu, C. Dumitrescu, G. Matache, Using real time simulation for off - line testing ofelectro - hydraulic control systems, COMEFIM10 - The 10-th International Conference on Mechatronics andPrecision Engineering, Bucharest 19-21 May 2011, http:// www.comefim10.pub.ro , MCT 2/2011 -Mecatronica Review No. 2/2011. [6] Drago Ion GU, Ctlin DUMITRESCU, Ioan LEPADTU, Corneliu CRISTESCU , Experimentalidentification of electrohydraulic servomechanisms with virtual instruments technique, HIDRAULICA review,No. 3, October 2010, pp.49-56.
http://www.comefim10.pub.ro/http://www.comefim10.pub.ro/http://www.comefim10.pub.ro/


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PNEUMATIC MEASURING OF THE BIOMASS CONSUMPTION FOR TLUD

GENERATORErol MURAD 1, Ctlin DUMITRESCU 2, Ioan LEPADATU 2, Liliana DUMITRESCU 2

1 Universitatea POLITEHNICA din Bucuret i, e-mail address: [email protected] 2 INOE 2000 IHP, e-mail address: [email protected]

Abst ract: Efficient management of energy production from biomass with thermal generators andgenerators TLUD requires continuous measurements of biomass consumption correlated withinput parameters which is air flow for gasification. As an alternative to electronic measuringsystems, which in the exploitation conditions for gasogen are more expensive than the usual ones,it is analyzed the use of pneumatic force sensors at which the measured pressure is not sensitiveto temperature variations.Measurement of biomass is performed online with a pneumatic force transducer working undersampled measurements. Measurement structure presented has very low energy consumption,specific to the technical systems with energy independence and low cost automation. Themeasurement system is connected to PLC for automatic driving of thermal system. Adjustingperformances of the thermal generator operating mode and energy consumption for forcetransducer were determined by simulation experiments conducted with a simulation model and anumerical simulation program, developed in the simulation environment MEDSIMFP10. Simulationexperiments confirmed low pneumatic energy consumption and a better measurement accuracy.Keywords : pneumatic transducer, power, biomass, TLUD, energy consumption, low cost

1. Introduction

The production of energy from biomass is an ecological and economical method which is incompetition with other sources: solar thermal and photovoltaic, wind energy, hydro or geothermal.The main advantage of biomass is that it can be produced energy with it when, where and in thenecessary amounts.

At present, in parallel with up-draft and down-draft gasification systems, are developedsystems based on the TLUD process that is easy to use and stable in operation; the system hasthe advantage of being cheap and recently revealed that produces an unconverted carbon quotacalled biochar, which if is introduced in soil represents a great soil amendment and contributes tothe increase of land fertility and through carbon sequestration in soil relatively large periods of timecontributes directly to the reduction of the CO 2 in the atmosphere. A TLUD thermal generatorconsists of a generator with TLUD process of micro-gasification of biomass which produces fuelgas which is combusted in a burner directly coupled to the generator. [2,8,9]. The automaticmanagement of thermal power generation process requires the measurement of biomass C bm consumption (kg. bm /s) and air flow D ag for gasification (kg. aer /s). TLUD thermal modules requirevery little electricity to operate, maximum 0.3% of rated thermal power, TLUD being the thermalenergy source suitable for installations with energy independence used in agriculture and isolatedareas. [1,3,7,8]

This paper presents and analyzes the operation and performances of a measurementscheme online for the weight of a TLUD generator that uses a pneumatic force transducer workingunder sampled mode. The solution presented is characterized by very low energy consumption,low price and a measurement error 2%. The measurement system is connected to the PLCdedicated to automatic management of thermal system.
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2. Thermal generator with TLUD gasogen

An ecological and economical alternative for biomass gasification is the process of micro-gasification TLUD (Top-Lit Up-Draft), designed by Thomas Reed in 1985. In this TLUD processbiomass layer is fixed in the reactor and the oxidation and pyrolysis front continuously descendsconsuming biomass, features that ensure safe operation and controllers. Operation is in batcheswith acceptable variation thermal load from 50 to 100%. In Figure 1 is a functional schematicdiagram for a thermal module TLUD and in Figure 2 a thermal module GAZMER FORTE-30. [8]

Fig. 1 Schematic functional of a thermal moduleTLUD

Fig. 2 Thermal module TLUD by 30 kW

G MGB weight thermal module is the weight of the generator and burner G G and the weight ofthe biomass and biochar G bm from reactor:

Fig. 3 Diagram of positions for centers of gravity

)( b mGb mG M G B M M gGGG +=+= ( 1)CG G center of gravity is fixed as position but thecenter of gravity CG bm volume of biomass isoffset horizontally by e bm (figure 3); thereforethe center of gravity position CG MGB thermalmodule is between CG G and CG bm shiftedhorizontally by e MGB (m). It follows that there isan eccentricity between CG G and horizontalpositions CG bm . Calibration of the weighingsystem is done with G G value which is known.When biomass is loaded, thermal module centerof gravity moves in CG MGB which is offset fromthe CG G with e MGB that will have a value of:

b mG

b mb m M G B GG

Gee +

= ( 2 )

value decreases during operation due to. This


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biomass consumption and weight reduction G bm function will affect measurement accuracy.

3. Pneumatic for ce transducer

Applying the concepts of minimizing energy consumption, energy independence and lowcost automation system, there was designed an unconventional pneumatic transducer which dontneed a special source of compressed air, consumption being extremely low, which simplifiesconstruction, so the cost of the transducer and total energy consumption is very low. [4,5,6].

It has been chosen pneumatic version because the pressure signal, that is proportional tothe measured weight, is not influenced by the environment temperature, measurement accuracybeing high. The main element of transducer is the pneumatic load cell that converts the measuredforce F mas in a pressure p mas that is proportional to the force.

In figure 4 is presented the functional diagram of the pneumatic load cell designed fordrying processes that can be used at processes at which variation of the measured force isproduced slowly and in a single direction. F mas (t) measured force is applied to the head of a rod 4fixed to the rigid center 3 of a goffered flexible membrane 2 with effective diameter D ef andconstant effective surface S ef , mounted in the body 1. On the rod 4 is fixed a nozzle 5, withdiameter d d , which rests on a ball 6, with diameter d b , closing the air access from measurementchamber to the outside through holes in the membrane, rigid center and rod. The measuringchamber can be connected in parallel with a pneumatic capacity V ad . The supply of pneumaticcircuit is made by a pneumatic variable resistance RP and a distributor DP type 2/2. The pressuresource should have p al 1.5 p mas max . The measured pressure p mas (t) is applied to a converterp/U, which has at the output a voltage Y F [1,3] Vcc.

Fig. 4 Functional diagram of the pneumatic force transducer

To measure a force with a variation in a single direction, specific for the gasificationprocesses in the fixed layer of biomass, when the weight of the gasogen decreases continuously,is necessary a single compressed air supply after operation reactor charging with batch biomass.During thermal energy generation F mas decreases continuously, p mas decreases continuously andamount of excess air is discharged outside through the space between the nozzle and the ball to

keep the balance of power. This measurement method uses a very small amount of compressedair, therefore very little pneumatic energy. Pneumatic output signal p mas from measuring chamberis converted into electric unified signal with a converter p/U. [5,6].

Fig. 5. Functional diagram for a gasogen weighting system


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4. Measurement algorithm

For reducing pneumatic and electric energy consumption was designed a managementalgorithm for transducer operation in regime sampled with a period T es (10...20) s only at the startof the gasification process, about 3 -10 min, after that the pneumatic sensor doesnt be need tosupplied with compressed air. Reading the transducer output voltage y G is realized in PLC with afrequency 10 Hz .

For measurement of biomass consumption, the gasogen 1 is positioned on a support 2which is leaned on two ball bearings 3 and on another support 4 type knife-wedge, on the lever ofweighing 5 which has one end resting on base and the other end resting on the pneumatic forcetransducer 6 which is connected to the interface block 7 through which the compressed air supplyto pressure p al and measuring signal exits Y G . Vertical center of gravity CG MGB is at the distance L1from supports 3. The distance between 3 and 4 supports is L2. The measured force F mas applied tothe transducer has the value:

m a s bm a s GF b mGb mGm a s F F K M M

L L

L LGGF +=+=+= )()(

24

13 (3)

where: M G and M bm weight of gasogen and biomass (kg);KF - transfer factor of the weighing machine (s/m 2);F masG the component due to gasogen (N);F masbm the component due to biomass (N);Biomass consumption dM bm / dt (kg/s) in the variant of sampled reading with t will be:

t

F

K t

M m a s

F

b m

=

1 (4)

Electrical out

hidraulica magazine 3-4-2012

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