7. lp turbine - engsoft · 2017-12-21 · conventional inlet casing (torous) axial design...

Steam Turbine 7. LP Turbine 1 / 53

7. LP Turbine Bearings

LP Casing

LP Inner Casing

Reheat Stop and

Intercept Valves Double Shells Packing

Head

Packing

Head

Wheels and

Diaphragms


Toshiba

Nomenclature


LP Turbine Structure


Characteristics of LP Steam Turbines

Longer blades

• 3D design

• Titanium blade

Wet steam

• Lower efficiency caused by moisture loss

• Difficult to predict flow behavior

• Water droplet erosion

Erosion shield (stellite), or flame hardening

Titanium blade

Vibration control

Reduced axial distance

Hard to develop a new model


LP Steam Turbine

The efficiency of modern HP and IP steam turbines can be predicted very accurately because it is mainly a

function of the flow losses in the blade (steam path).

The flow losses have been established in systematic experiments in the fluid mechanics laboratories for all

geometric dimensions and flow conditions.

The economic optimization (availability, efficiency, and capital cost) of the LP turbine design is not always so

successful.

Wet steam and three-dimensional flow patterns make complete and accurate measurements difficult.

The high costs of systematic tests with LP turbines have until now also prevented the accumulation of data

which would permit an accurate efficiency analysis of the LP turbine alternatives.

In addition, the LP efficiency has hardly been indentified theoretically, so that an empirical evaluation based

on a few measuring points was all that was possible.

Currently, this kind of problem has being solved with an aid of CFD techniques.

However, the problem related to the wet steam is still vague because phase change can not be solved with

CFD techniques.

In conclusion, in order to optimize the LP turbine, we have to rely on the experience of engineers who are

familiar with the complexity of the problem and can bridge the gaps with reasonable assumptions.


The LP turbine efficiency is greatly affected by exhaust loss.

Double flow provides smaller annulus area at the LSB exit

plane, and it requires shorter LSB.

The axial thrust is equalized by the double flow, therefore, no

dummy piston is required.

LP Steam Turbine


Skoda - Doosan

Conventional inlet casing (Torous) Axial design

Radial-axial design

LP Steam Inlet Design


Although the velocities are much lower in the inlets,

meaning that less performance is lost than in the

exhaust, some improvements can be made.

Aside from the basic area rules of crossover to LP

inlet to 1st stage used to avoid acceleration, the LP

inlet shape can be designed to reduce pressure

drop.

Figure shows a CFD analysis of an LP inlet before

and after aerodynamic optimization. The colors

represent areas of different velocity. (red is high,

blue is low)

Velocity magnitude contours (GE)

Old Design New Design

LP Steam Inlet Design


LP터빈은 입구부터 배기까지 온도차가 매우 크기 때문에 케이싱을 2중 구조로 제작하여 각각의 케이싱에서 발생하는 온도차를 적게하여 케이싱의 열변형 방지.

내부케이싱에는 노즐과 다이아프램(블레이드 링) 장착.

외부케이싱은 LP터빈 외형 형성.

외부케이싱 외부는 대기압, 내부는 복수기 진공압력이 작용하기 때문에 외부케이싱에는 약 500톤의 진공하중 작용. 외부케이싱은 진공하중 이외에 내부케이싱 중량과 약 150톤 정도의 외부케이싱 자중 작용. 따라서 외부케이싱은 이들 하중에 견딜 수 있도록 강도와 강성을 확보하기 위하여 내부 여러 곳에 지지대와 리브 설치.

외부케이싱 상부에는 동판으로 제작된 대기방출판(atmospheric relief diaphragm, or breakable diaphragm, or rupture disc) 설치.

대기방출판은 증기터빈 안전장치로서 복수기에 냉각수 공급이 정지하거나 어떤 다른 원인에 의해서 LP exhaust hood 압력이 대기압보다 높은 압력(130~140 kPa)으로 올라가면 외부케이싱 외부로 증기압력이 작용하여 동판이 칼날에 의해 절단되면서 증기를 외부로 방출시켜 LP exhaust hood 및 복수기 파손 방지.

만약 운전 중에 배압이 상승하면 경보가 울리며, 계속해서 상승하면 low vacuum trip이 작동하여 증기터빈을 트립시켜 LP exhaust hood와 복수기를 보호하지만 그 이상으로 올라가면 최종적으로 대기방출판이 절단되면서 증기터빈 보호.

Casing

Inner Casing (GE)


LP Turbine (Siemens) LP Turbine Inner Casing (Siemens)

Casing


A push rod concept permits parallel axial thermal expansion of LP rotor and inner casing.

This reduces clearances between rotor and casing and improves the efficiency.

SST5-6000 Steam

Turbine (Siemens)

Casing


LP Exhaust Hood

LP exhaust hood is a transition structure

between the LSB exit and the condenser.

It consists of a steam guide, bearing cone,

butterfly vane, outer casing, end wall, and

various plates.

It changes the direction of the steam flow

exiting LSB plane from axial to radial in the

case of downward flow LP exhaust hood.

It supports the main components of LP

turbine, such as inner casing, diaphragms,

bearings etc.

Condenser Flange

Steam

Guide

Collector

Bearing

Cone

Outer Casing

End

Wall

LSB

Inner Casing

Steam Flow

Siemens


Bearing cone

Horizontal joints

Flow plate

Transverse plates

Side plates

Front wall

Inner casing

Butterfly vane

Steam guide

Central plate

Radial

plates

GE Configuration GE

LP Exhaust Hood


It is generally employed for small industrial steam turbines.

The steam exiting LSB enters condenser in axial direction.

The flow distribution is uniform on LSB exit plane along the circumferential direction.

It has a lower exhaust loss than downward flow LP exhaust hood.

It requires a larger plant area than downward flow LP exhaust hood.

1) Axial Flow Exhaust

SST-800 (Siemens) SST-600 (Siemens)

LP Exhaust Hood


Type of LP Exhaust Hood

It is generally employed for large steam turbines.

It has a higher exhaust loss than axial flow LP exhaust hood because of the change of flow direction from

axial to radial, and then downward finally.

It requires a smaller plant area than axial flow LP exhaust hood.

2) Downward Flow Exhaust


It acts as a diffuser to provide static pressure recovery.

The LP exhaust hood must be aerodynamically designed such that it provides a minimal

obstruction to the steam flow from the LSB exit plane to the condenser to minimize loss of

energy.

Pressure loss of 1 in.Hg in a LP exhaust hood can result in a 1% increase in plant overall

heat rate.

It is a supporting structure for the LP rotor bearings.

Typically, the LP bearings are supported in a cone shaped structure overhung into the

hood at the end walls.

This arrangement is used to minimize the rotor span, and thus minimize rotor bending

from the gravitational force and to optimize critical speeds of the rotor.

It supports the weight of the inner casing and diaphragms and must provides

precise positioning of the inner casing, diaphragms, bearing and packing.

3 Major Functions

LP Exhaust Hood


Extremely low back pressure

Large annular flow area

Large volumetric flow rate of working fluid

High turbine exit velocity

• Faced with strength limit because of

Increased active length of blade

• Increased capital cost

• Increased leaving loss because of high

turbine exit velocity

• Required advanced LP exhaust hoods

High kinetic energy leaving LSB

Pressure recovery

The function of LP exhaust hood

• Increased turbine output

• Decreased cycle heat rate

Function

LP Exhaust Hood


LSB annulus plane; Bearing cone; Steam guide; Collector

Inner casing; Outer casing; Condenser flange; End wall

Flow Behaviors in LP Exhaust Hood

LP exhaust hood is one of the few

steam turbine components having the

potential to be improved

Flow is highly three-dimensional

Geometry is extremely complex

Hard to model parametrically

Many potential design parameters


Losses of Turbine Components

Com

po

nen

t L

osse

s R

ela

ted

to T

urb

ine

Ou

tpu

t

HP Turbine IP Turbine LP Turbine

Steam Turbine Efficiency

1970

1990

87%

90%

%

2.0

1.0

Siemens 600 MW Reheat Steam Turbine

① Valve and admission

② Profile

③ Shaft & inter-stage seal

④ Extraction & exhaust

⑤ Reheat pressure

⑥ X-over pressure

⑦ Moisture

⑧ Mechanical


GE

A Typical USC Steam Turbine


500 MW Steam Turbine [Example]

(a) Started from LSB hub (b) Started from LSB pitch (c) Started from LSB tip

Steam Path Lines in a LP Exhaust Hood


1) Flow distribution should be improved because

of the flow concentration on the end wall makes

the exhaust loss get higher and the flow

distribution on the LSB annulus plane get

worse.

2) Exhaust loss is very high because of old style

of steam guide. This type of steam guide has

never been used recently in the design of

advanced steam turbines.

3) The strength of the swirl flow at collector is so

strong that contributes higher exhaust loss.

500 MW Steam Turbine [Example]

Flow Behavior in a LP Exhaust Hood


Condenser Flange

[ Velocity Vectors in a LP Exhaust Hood ]



(a) Conventional 500 MW Steam Turbine (a) Newly Designed LP Exhaust Hood

[ Velocity Vectors on the LSB Exit Plane ]

Flow Behavior in a LSB Exit Plane


Steam guide 벽면으로의 유동 부착 및 집중

방향전환 mechanism (axial radial)

Coanda Effect


E D C B A

1) Discuss the flow behavior on the LSB exit plane in terms of power output.

2) LP turbine vibration can be improved?


[ Normalized Velocity Magnitude on the LSB Exit Plane ] -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50V1

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

V2

1.5

1.25

1.0

0.5

0.75 A B C D E

Improved Design Conventional Design


Some Issues


207D-17

Steam Turbine

109D-14

Steam Turbine

GEA18786 (June/2011)

Some Issues


LP Rotor Shaft

Shrunk-on rotor

Monoblock rotor

Welded rotor

블레이드가 장착되어 있는 로터축은 LP터빈 전체 가격의 약 40% 차지.

로터축 가격은 허브 지름에 의해서 결정. 로터축 가격을 낮추기 위하여 허브 지름을 줄이면 버켓 단 수와 로터축 길이 증가 (h U2). 로터축이 가늘고 길어지면 회전체 동력학 측면에서 설계 어려움. 아울러 로터축이 길어지면 터빈빌딩이 커지기 때문에 발전소 건설비용 증가.

단 수와 허브 지름은 LP터빈 구성과 로터축 설계를 결정하는 가장 중요한 요소.


열박음 로터축(shrunk-on rotor)

• 초대형 잉곳을 확보하기 어려울 때 사용.

• 지름이 작은 로터축을 제작한 후에 휠 디스크를 제작하여 열박음 통하여 일체화.

• 제작이 쉬운 반면에 기동정지 시에 불안정한 진동이 발생하기 쉬우며, 휠 디스크에 응력부식균열이 발생하는 단점 보유.

• 최근에는 거의 채택하지 않고 있음.

일체형 로터축(monoblock rotor)

• 최근 제강기술이 발달하여 가공중량 200톤 정도의 일체형 로터축 제작

• 열박음 로터축에 비해 강도가 한층 높으며, 응력부식균열이 나타나지 않기 때문에 신뢰성이 높음.

• 열박음 로터축에 비해 제작에 많은 시간이 소요.

• 국내 화력발전 LP터빈 로터축은 모두 일체형이며, 원자력발전은 영광 5.6호기와 울진 5.6호기부터 모두 일체형으로 설계.

용접 로터축(welded rotor)

• 원자력발전과 같은 대형 LP터빈에 사용. 현재는 용접기술과 열처리기술이 발달하여 몇 개의 로터를 용접으로 연결하여 하나의 로터축으로 제작한 용접 로터축 많이 사용.

• 가격이 상대적으로 저렴한 작은 잉곳 여러 개를 이용하기 때문에 전체적으로 가격 저렴.

• 제작단계에서 재료결함 검사가 용이하기 때문에 신뢰성 우수. 일반적으로 로터축 내부 빈 공간은 부식 방지를 위해 진공 유지.

• 두 가지 이상의 서로 다른 재료를 용접하여 사용할 수 있기 때문에 로터축 온도분포에 따른 최적의 로터축 제작. 초임계압 발전에서 나타나는 고온부식을 줄이기 위해 전통적으로 사용하던 CrMoV에 9Cr과 12Cr강을 용접하여 사용.

LP Rotor Shaft


LSB Features

Last Stage Blade [1/14]

1) LSB는 LP터빈 형상을 결정하는 중요한 요소이다.

2) LSB 길이는 사이트 대기조건과 응축계통에 의해서 가장 큰 영향을 받는다.

3) LSB가 길어질수록 배기손실이 감소하여 증기터빈 성능이 향상된다. 그러나 동일한 출력을 가지는 증기터빈의 경우 LSB가 길어질수록 제작비가 증가한다.

4) LSB는 큰 출력을 생산한다. 일반적으로 대형 화력발전의 경우 LSB는 증기터빈 전체 출력 가운데 약 10%를 생산한다. 복합발전의 경우에는 증기터빈 출력의 15~17% 정도가 LSB에서 생산된다.

5) LSB가 길어지면 큰 회전속도가 나타나는 LSB 팁 부위에서 초음속유동이 발생한다. 따라서 길이가 긴 LSB 팁 부위 날개형상은 초음속유동에 적합한 수축-확산노즐 형태를 가진다.

6) LSB는 습증기 영역에서 운전되며, 큰 회전속도를 가지는 팁 부위에서는 물방울과 큰 속도로 충돌하기 때문에 습분침식이 발생한다. 따라서 대부분의 LSB는 화염 경화나 방식막 부착 등을 통해서 습분침식에 대비하고 있다.

7) LSB에는 큰 인장응력이 발생한다. 최근에는 인장응력을 이겨내기 위해서 티타늄합금을 이용하여 LSB를 제작하고 있다. 티타늄합금은 습분침식과 부식 저항성이 우수하기 때문에 LSB 재료로 많이 사용되고 있다. 그러나 티타늄합금은 가공성이 불량하기 때문에 LSB 가격이 비싸진다.

8) LSB는 길어질수록 고유진동수가 작아지기 때문에 진동특성이 나빠진다.


57 inch

1.45 m

69 inch

1.75 m

75 inch

1.9 m

[ A typical LSB for Fossil Power Plants ] [ Typical LSBs for Nuclear Power Plants ]



Each LP turbine is characterized by its outlet area.

Sout = dp2(h/dp)

where, dp = pitch diameter of LSB, h = active

length of blade)

If the hub diameter and thus the pitch diameter of

LSB is reduced, the blade length/diameter ratio must

be increased.

However, h/dp is a parameter which greatly

influences the three-dimensional flow in the last

stage. Today’s customary values lie between 0.3

and 0.35, and may reach 0.38 in extreme cases.

The larger the h/dp, the harder the sound

aerodynamical design of the blade.

An increase in the h/dp for a fixed outlet area leads

to longer LSB.

The risk of blade vibration increases with blade

length because the natural frequencies of the blade

decrease as the blade length increases.

dp

h



Turbine Output and Annular Exhaust Area

45 LSB results in a 28% increase in annulus area over that of the 40 LSB.

Longer LSB provides reduced leaving velocity, which results in low exhaust losses and improved heat rate.

Increasing the turbine exhaust annular area gives increased capacity and turbine efficiency, but it increases

turbine size and capital and construction costs.

Increasing the LSB length is restricted by centrifugal stresses in blades, and the number of LP flows and LP

cylinders cannot be too great because of the total turbine length.

A way to reduce the centrifugal loads and make the longer LSB is to use titanium materials, which is lighter

and stronger than steel.

Longer blades are more expensive than shorter ones because they have a better resistance to water droplet

erosion.

The longer the blades, the harder vibration control of blades because of lower natural frequency.

A cylinder with too long a rotor has to be designed with increased radial clearances in its steam path because

of weight bowing of the rotor and danger of its increased vibration.



32-LSB/3600rpm (Siemens)

Mach Number Distribution



LSB Tip Profile [GE]

Supersonic Converging-Diverging Nozzle

Blade Overlap

Supersonic Converging-Diverging Nozzle

Blade Overlap



The convergent-divergent LSB gives higher efficiency than

conventional LSB for higher discharge velocities of Mach

number of 1.4 in the tip section

However, the LSB having flat profile becomes more efficient

below a Mach number of 1.4

Therefore, it should be investigated flow behaviors at the tip

region of LSB during part load operation and changed back

pressure

It was found that, with reduced volumetric flow in the last stage

blade, the steam moves towards tip section, Thus, when the

overall volumetric flow is decreased, the flow distribution over

the blade length changes, resulting in a much larger reduction

of flow in the hub section and little change at the tip section

Typically, discharge velocity at the tip of LSB does not drop

below a Mach number of 1.3, which justifies the application of

the convergent-divergent profile under typically changing

operating conditions of power plants

Siemens

[ Free standing LSB (Siemens) ]



Advanced LSB Nozzle

[ 40 L-0 Nozzle Assembly ]



Both tangential and axial lean are applied to the L-0 nozzle.

Compound tangential lean is utilized to impart an inward radial force on the flow – forcing more flow into the

hub region and increasing the pressure.

Combined with the flow path contouring the L-0 nozzle lean reduces the radial pressure gradient at the nozzle

exit, raises the root reaction.

Axial lean is used to control the nozzle to bucket spacing while minimizing the potential for erosion.

An increased nozzle to bucket distance near the tip reduces the possibility of nozzle induced stimulus, which

results in a more robust mechanical design.

Advanced LSB nozzle not only reduces losses within its boundaries, but also optimizes the flow conditions for

the following moving blades.

Advanced LSB Nozzle


The advanced forward curved and twisted blade provides an optimal flow

distribution with increased flow at the hub avoiding flow separation, and

reduced flow at the moving blade tip for minimizing boundary losses.

The best performing center section of moving blade receives an increased

mass flow.

The hollow stationary blade is ideally suited to form a thick profile at the outer

diameter and to provide suction slots for moisture removal.


Advanced LSB Nozzle



Steam flow during low load and high exhaust

pressure operation

During the low load and high exhaust

pressure, random vibration or stall

flutter occurs in last stage blades of

LP turbine.

In such condition the steam inlet flow

angle is larger than normal resulting in

negative angle of attack.

As a result of large negative angle at

the inlet to the blade, steam flow

separation causes the blades to

vibrate in stall flutter.

Flutter of Turbine Blades

Stall

C1,off

U

W1,off

C1,design

W1,design

W1,design

W1,off

Bucket

Nozzle

U = Wheel speed

C1 = Absolute velocity

W1 = Relative velocity



The structural instability is due to the interaction between the unsteady aerodynamics and the structural

dynamics of the blades.

In the power generation industry, there is a drive to increasingly large exhaust areas of low-pressure steam

turbines, leading to longer blades.

Under this condition, design of turbine blades is more likely to react to the effects of dynamic loading due to

unsteady aerodynamics.

The last stage blades, that contribute approximately 10% of the overall output of a modern power plant are

surrounded by hostile aerodynamic environment due to the transonic and droplet laden flow.

The longest blades of the last row in a LP turbine are always tapered and twisted to accommodate the

demands of mechanical integrity and aerodynamic performance.

Flutter of Turbine Blades


The tip section of freestanding blades

in the last row is more flexible, thus it

is difficult to control tip vibration and

its susceptibility to flutter.

Continuously coupled blade row has

greater stiffness that helps to resist

vibration and bending forces.

http://www.google.co.kr/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjl3qe5h4HNAhWD3KYKHQ3rDKoQjRwIBw&url=http://www.alstom.com/press-centre/2012/644425/alstom-announces-worlds-longest-turbine-blade-for-optimum-nuclear-power-plant-efficiency/&bvm=bv.123325700,d.dGY&psig=AFQjCNGGz3qgjnIGajbz3vbv1iVw-f4Nyw&ust=1464672193254064

http://www.google.co.kr/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj7sKvSh4HNAhXCYaYKHZ-JDHQQjRwIBw&url=http://www.ccj-online.com/7fa-d11-a-10-inspection/&bvm=bv.123325700,d.dGY&psig=AFQjCNGvuFYDzC-YQWNc6K5BJByQmW1SjA&ust=1464672292920942


① Harmonic excitation

• Time dependent periodic fluctuating flow

• By design practice all the long blades are tuned so as to avoid due to harmonic excitation

② Random or broadband excitation

• This is primarily due to temporal unsteadiness of the flow over the stationary blades.

• Sudden changes in the flow path and steam extraction have been observed to initiate flutter in the

blade

③ Self excitation

• It does not need external excitation, but excitation is internally generated.

• Stall flutter, usually occurred during low load operation and high exhaust pressure, belongs to this.

Flutter of Turbine Blades - Sources of Blade Excitation



Cold-end Optimization [1/4]

The kinetic energy of the steam leaving the LSB exit plane is

assumed to be almost completely lost.

The exhaust volume flow ( ) is fixed approximately by the

turbine power output and the condenser conditions.

Hence for a given volume flow, this lost kinetic energy will

depend only upon exhaust area.

It becomes a matter of economic optimization to select the

optimum exhaust area and therefore the active length of the

LSB. This process is known as cold-end optimization.

For cold-end optimization, the LP turbine, condenser, lowest LP

feedwater heater, and the cooling water system are taken into

consideration.

For this optimization, the condenser pressure cannot be chosen

freely because climatic conditions, such as air temperature,

humidity, and cooling water temperature, may limit the choice of

the pressure.

But, within the given limits, the investigation will provide the

economic optimum.

m 1

2

3

5

6

7

8

4

1. LP Turbine 2. Condenser

3. Cooling water pump

4. Main condensate control valve

5. Condensate pump 6. LP Feed water heater 1

7. Cooling tower 8. Extracted steam

[ Fluid Flow in LP Turbines ]


ho

h

EL

1

2

p2

h

p2

m2

p2

hmOutput

Effect of Condenser Pressure [1/3]



Siemens

The kinetic energy of the steam

leaving the LSB exit plane

increases as the condenser

pressure decreases.

However, at a certain condenser

pressure, the choking condition is

reached at the last stage.

Any further decrease of the

condenser pressure increases

exhaust losses, h remaining

unchanged.


0.5 1.0 1.5 2.0 1.76 in.Hga

0 2 12 16 19

18

16

14

12

10

8

6

4

2

0

Cooling Water Inlet Temperature

Po

we

r G

ain

, M

W

4F30"

4F32"

4F38"

6F32"

C

Choking



h increases as the condenser pressure decreases, but the temperature of the condensate at the inlet to the

lowest LP feedwater heater falls.

In this case, the extracted steam flow rate increases, and the steam flow through LSB will decreases at the

same time.

The selected condenser pressure will determine a set of parameters including turbine output, cost of

components and operating costs.

For given climatic conditions, the condenser pressure can be lowered only by taking measures which

increase the cost of the plant and the cooling system, for example by increasing cooling water flow and

condenser heat transfer surface.

Similarly, the added thermal resistance of dry or wet cooling tower will generally require increased condenser

size and result in a higher optimum condenser pressure.




Modified sliding pressure operation uses control valve reserve so the valves are slightly closed at 90% to

95% and some boiler stored energy can respond more quickly to rapid load change near full load.

Condensate throttling is applied when the grid frequency is decreased greatly.

If the grid frequency requires high power demand and the unit is in modified sliding pressure operation(hybrid

operation), the turbine control valve is opened to raise the load (except if the valves are fully opened already).

Simultaneously the main condensate control valve is throttled to a calculated position allowing a reduced

condensate mass flow passing through the LP feedwater heaters.

Considering a certain time respond, the extraction steam mass flow of the LP feedwater heater and the

deaerator / feedwater tank are reduced.

The surplus steam remains in the turbine and generates additional power.

The resulting load increase depends on the amount of pre-set throttling of main control valve of the turbine,

the throttling of the main condensate control valve and the actual unit load.

By means of additional fast acting valves in the regarding extraction steam lines the response time behavior

can be optimized.

This condensate throttling serves as compensator for the transient time behavior of the boiler.

Frequency Control – Condensate Throttling [1/3]


The accumulated condensate is stored in the condenser hotwell or a separate condensate collecting tank.

Parallel to the above mentioned measures the firing rate of the boiler is increased to meet the load

requirements.

The feeding of the boiler is continued and increased.

Thus, the level of the feedwater storage tank is decreased accordingly.

During this time the condensate flow reduction is gradually released and has reached steady state condition

again.

Refilling of the feedwater storage tank is initiated by releasing the condensate control valve to control the

level of the hotwell or condensate collecting tank.

The maximum allowable condensate mass flow is monitored and the refill flow is limited to a maximum value.

Due to the increased condensate flow through the LP feedwater heaters and into the deaerator, the steam

extraction from the affected turbine extractions is increased.

The generator output decreases correspondingly.

To compensate this influence the boiler-firing rate is increased.

However, the maximum allowable superheater outlet flow is limited to 100% BMCR(Boiler Maximum

Continuous Rating)



Steam Turbine Load, %

Ma

in S

tea

m P

ressu

re, %

0 20 40 60 80 100 0

25

50

75

100

• Today, modern power plants are operated in natural

sliding pressure mode or modified sliding pressure mode.

• Primary electrical power response (additional

electrical power within seconds) is produced by

condensate throttling.

• At a certain part load, the control valves can to be

throttled to improve the primary response capacity

Fixed Pressure Mode

Fixed Pressure Mode



질의 및 응답

작성자: 이 병 은 작성일: 2016.6.21 (Ver.7) 연락처: [email protected] Mobile: 010-3122-2262 저서: 실무 발전설비 열역학 증기터빈 열유체기술 발전용 가스터빈

7. lp turbine - engsoft · 2017-12-21 · conventional inlet casing (torous) axial design...

Documents