reciprocating internal combustion engines lecture... · 2 bond strength 12 cefrc6 june 28 ......
TRANSCRIPT
1 CEFRC6 June 28, 2012
Reciprocating Internal Combustion Engines
Prof. Rolf D. Reitz,Engine Research Center,
University of Wisconsin-Madison
2012 Princeton-CEFRCSummer Program on Combustion
Course Length: 9 hrs
(Wed., Thur., Fri., June 27-29)
Hour 6
Copyright ©2012 by Rolf D. Reitz.This material is not to be sold, reproduced or distributed withoutprior written permission of the owner, Rolf D. Reitz.
2 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Short course outine:
Engine fundamentals and performance metrics, computer modeling supportedby in-depth understanding of fundamental engine processes and detailedexperiments in engine design optimization.
Day 1 (Engine fundamentals)Hour 1: IC Engine Review, 0, 1 and 3-D modelingHour 2: Turbochargers, Engine Performance MetricsHour 3: Chemical Kinetics, HCCI & SI Combustion
Day 2 (Spray combustion modeling)Hour 4: Atomization, Drop Breakup/CoalescenceHour 5: Drop Drag/Wall Impinge/VaporizationHour 6: Heat transfer, NOx and Soot Emissions
Day 3 (Applications)Hour 7: Diesel combustion and SI knock modelingHour 8: Optimization and Low Temperature CombustionHour 9: Automotive applications and the Future
Scorching Detonation Cracking
Engine Heat transfer
Up to 30% of the fuel energy is lost to wall heat transferCan influence engine ignition/knockEngine durability – catastrophic engine failure
3 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Challen & Baranescu, 1998.
Heat Transfer
c s rII p Q Q Q
t
u u J
Gas phase energy equation
Radiation source term
4
, 4rbQ I d I
Ω
r r Ω Ω r
* *ln 2.1 33.34
2.1ln 2.5g p g g w
w
C u T T T y G uq
y
* ln
2.1ln 2.5p g g w
w
C u T T Tq
y
2.12.1w
g p
qdTG
dy C y
2.1 * ln
2.1ln 2.5
gg
w
Tu T TdT
dy y y
Wall heat flux (account for compressibility)With radiation Without radiation
G radiative heat flux = qwr
4 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Han & Reitz, 1995
Radiation modeling
Radiation Transfer Equation:
Scattering terms, , S ~ usually neglected compared to absorption
Radiation intensity at wall
surface emissivity
, , ,4
snet s bI a I I S
Ω r Ω r Ω r r Ω
net absorption coefficient, scattering coefficientneta s
net sa extinction coefficient
4
wb
TI
r
4
0
,rw wG q I d T
n Ω
n Ω r Ω Ω
Back body radiative flux (independent of angle)
Discrete ordinates model
1
4nDir
r m mb
m
Q I I
r r r
5 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
s
Wiedenhoefer, SAE 2003-01-0560
Soot and Gas Absorption
Total absorption coefficient
Soot absorption
Wide band model for CO2 and H2O
2 2net soot CO H Oa a a
-11260 msoot soota C T CO2 absorption bands
2
312,
1b band center C Tband center
CTe
1, , ln 1 , ,g e g ee
a T P L T P LL
2 2
1 1 1 1 1fuel CO CO H O
Importance of soot:
1g a sa
T so o ta T
4
4
, 4rb gas sootQ a I d I a a T
Ω
r r Ω Ω r 3 5gas sootT T
6 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Wiedenhoefer, SAE 2003-01-0560
Wall heat transfer
Conjugate heat transfer modelingERC - Heat Conduction in Components code (HCC)
Iterative couplingbetween HCCand CFD code
UnstructuredHCC Mesh
7 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Wiedenhoefer & Reitz, 2000
Wall heat transfer
Cut Plane
Cummins N14 engine
8 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
. . . . . . . . .
Caterpillar SCOTE engine
Wiedenhoefer & Reitz, 2000
-20 -15 -10 -5 0
560
580
600
620
640
660
680
700
720
740No Radiation
Run 1Run 2Run 3
With RadiationRun 1Run 2Run 3
Pe
ak
Pis
ton
Te
mp
erat
ure
[K]
Start of Injection, ATDC
= 0.7
Predicted piston temperature - CDC
Effect of radiation on wall heat lossTotal heat loss increased by 30% due toradiation.34% - head, 19% - liner, 47% - piston.Lowers bulk gas temperaturesResults in lower NOx and higher sootNOx reduced by as much as 30% (ave)
-20 -15 -10 -5 0
2
4
6
8
10
12
14
16
NO
x[g
/kW
h]
Start-of-injection, ATDC
= 0.5Uniform Temp / No radNon-uniform Temp / With Rad
= 0.7Uniform Temp / No radNon-uniform Temp / With Rad
9 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Wiedenhoefer & Reitz,SAE 2003-01-0560
Engine emissions - Transportation & Toxic Air Pollutants
Toxic air pollutants - Hazardous Air Pollutants or HAPs known to cause orsuspected of causing cancer or other serious health ailments.
- Clean Air Act Amendments of 1990 lists 188 HAPs from transportation.
In 2001, EPA issued Mobile Source Air Toxics Rule:- identified 21 MSAT compounds.- a subset of six identified having the greatest influence on health:
benzene, 1,3-butadiene, formaldehyde, acrolein, acetaldehyde,and diesel particulate matter (DPM).
Harmful effects on the central nervous system:BTEX/N/S - benzene, toluene, ethylbenzene, xylenes, Naphthalene, Styrene
Criteria air contaminants (CAC), or criteria pollutants- air pollutants that cause smog, acid rain and other health hazards.
EPA sets standards on:1.) Ozone (O3),2.) Particulate Matter (soot):
PM10, coarse particles: 2.5 micrometers (μm) to 10 μm in sizePM2.5, fine particles: 2.5 μm in size or less
3.) Carbon monoxide (CO), 4.) Sulfur dioxide (SO2),5.) Nitrogen oxides (NOx), 6.) Lead (Pb)
10 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Diesel emission solutions– Selective Catalytic Reduction (SCR) and Diesel Particulate Filter (DPF)
EGR?
SCR?Cummins Cu-Zeolite with DEF for 2010Claim 3-5% fuel economy gain (Class 8 truck 1% ≈$1,000 per year)“StableGuard Premix” dose rate ~2% of fuel consumption rate
Cost? $3/gal? AdBlue at pump in Germany $12/galVolvo announced surcharge of $9,600 for 2010 compliance
(complex – dosing rate, DEF freezes at 12F, gasifies at 130F)Plus $7,500 for 2007 compliance AT system cost equals cost of engine!
Navistar – no SCREnabling technologies (Cost?):Improved combustion bowl design - PCCIImproved EGR valves, air-handling, VVATwin-series turbochargers, inter-stage coolingHigh-pressure CR fuel injection (31,800 psi)
11 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
US EPA 2010 HD soot: 0.0134 g/kW-hrNOx: 0.2682 g/kW-hr.
1.)
2.)
Zeldo’vich thermal NOx mechanism
ERC 12-step NOx model is based on GRI-Mech v3.11 and includes:Thermal NOxPrompt NOx around 1000 K.
ExtensionsNO can convert HCN and NH3
Interaction between NO and Soot
NOx modeling
Rate controlling step due to high N2 bond strength
12 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Yoshikawa SAE 2008-01-2413
Zeldovich, 1946
Fenimore, 1979
Eberius, 1987
Guo, 2007
ERC 12 step NOx Mechanism
SENKIN2 used topredict specieshistories.
XSENKPLOT used tovisualize reactionpathways and identifyimportant reactionsand species.
Reduced mechanismvalidated for testtemperatures from700K to 1100 K andequivalence ratiosfrom 0.3 to 3.0.
Four additional species(N, NO, N2O, NO2)and 12 reactionsadded to ERC PRFmechanism
Kong, ASME 2007
13 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Detailed mechanism: Smith, GRI-mech, 2005
ERC 12 step NOx Mechanism
2
2
2 2 2
2
2 2
2 2 2
2 2
2 2
2
2 2
2
N NO N ON O NO ON + OH NO HN O O N ON O O 2NON O H N OHN O OH N HON O M N O MHO NO NO OHNO O M NO M
NO O NO ONO H NO OH
GRI mechanism results Reduced mechanism results
14 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Comparison of NOx predictions (T=900K, P=3.7MPa)
Diesel spray computation
inj
Kong, ASME 2007
Detailed mechanism: Smith, GRI-mech, 2005
CH radical and HCN bridge in fuel-rich regions
Tini=769K
Pini=40bar
Time=100ms
φφ=1.0=1.0 φφ=3.0=3.0N group
CxHy group
ConstantvolumeSENKINanalysis withERC n-heptanemechanism &GRI ver.3 NOxmechanism
Absolute Fluxnormalized toNO byXSENKPLOT
Competing?
15 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Yoshikawa & Reitz, SAE 2008-01-2413
Expanded ERC NOx reaction mechanismn+no <=> n2+o 3.500e+13 .00 330.0n+o2 <=> no+o 2.650e+12 .00 6400.0n+oh <=> no+h 7.333e+13 .00 1120.0n2o+o <=> n2+o2 1.400e+12 .00 10810.0n2o+o <=> 2no 2.900e+13 .00 23150.0n2o+h <=> n2+oh 4.400e+14 .00 18880.0n2o+oh <=> n2+ho2 2.000e+12 .00 21060.0n2o(+m)<=> n2+o(+m) 1.300e+11 .00 59620.0
low / 6.200e+14 .000 56100.00/h2/2.00/ h2o/6.00/ ch4/2.00/ co/1.50/ co2/2.00/
ho2+no <=> no2+oh 2.110e+12 .00 -480.0no+o+m <=> no2+m 1.060e+20 -1.410 .0
h2/2.00/ h2o/6.00/ ch4/2.00/ co/1.50/ co2/2.00/no2+o <=> no+o2 3.900e+12 .00 -240.0no2+h <=> no+oh 1.320e+14 .00 360.0
ch+n2 <=> hcn+n 2.857e+08 1.10 20400.0ch+no <=> hcn+o 5.000e+13 .00 .0ch+no <=> n+hco 3.000e+13 .00 .0ch2+no <=> oh+hcn 2.900e+14 -.69 760.0ch3+no <=> hcn+h2o 9.600e+13 .00 28800.0ch3+n <=> hcn+h2 3.700e+12 .15 -90.0oh+ch <=> h+hco 3.000E+13 .00 .0oh+ch2 <=>ch+h2o 1.130E+07 2.00 3000.0ch+o2 <=> o+hco 3.300E+13 .00 .0ch+h2 <=> h+ch2 1.107E+08 1.79 1670.0ch+h2o <=> h+ch2o 1.713E+13 .00 -755.0ch+ch2 <=> h+c2h2 4.000E+13 .00 .0ch+ch3 <=> h+c2h3 3.000E+13 .00 .0ch+ch4 <=> h+c2h4 6.000E+13 .00 .0ch+co2 <=> hco+co 3.400E+12 .00 690.0
12-step NOx reactions
Additional 15 reactions
with CH and HCN
[Sun, 2007]
Main species
N, NO, N2O, NO2
16 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Yoshikawa & Reitz,SAE 2008-01-2413
Expanded ERC NOx reaction mechanismnh3+h <=> nh2+h2 5.400e+05 2.400 9915.0nh3+oh <=> nh2+h2o 5.000e+07 1.600 955.0nh3+o <=> nh2+oh 9.400e+06 1.940 6460.0hcn+oh <=> hnco+h* 39.60e+00 3.217 8210.7ch2+no <=> h+hnco 3.100e+17 -1.380 1270.0hnco+o <=> nh+co2 9.800e+07 1.410 8500.0hnco+h <=> nh2+co 2.250e+07 1.700 3800.0hnco+oh <=> nh2+co2 1.550e+12 .000 6850.0hnco+m <=> nh+co+m 1.180e+16 .000 84720.0
h2/2.00/ h2o/6.00/ ch4/2.00/ co/1.50/ co2/2.00/nh2+o <=> oh+nh 7.000e+12 .000 .0nh2+h <=> nh+h2 4.000e+13 .000 3650.0nh2+oh <=> nh+h2o 9.000e+07 1.500 -460.0hcn+oh <=> nh2+co 1.600e+02 2.560 9000.0nh+o <=> no+h 5.000e+13 .000 .0nh+h <=> n+h2 3.200e+13 .000 330.0nh+oh <=> n+h2o 2.000e+09 1.200 .0nh+o2 <=> no+oh 1.280e+06 1.500 100.0nh+n <=> n2+h 1.500e+13 .000 .0nh+no <=> n2+oh 2.160e+13 -.230 .0nh+no <=> n2o+h 4.160e+14 -.450 .0hcn+o <=> nh+co 2.767e+03 2.640 4980.0ch2+n2 <=> hcn+nh 1.000e+13 .000 74000.0
Additional 22 reactions
with NH3, HNCO, NH2,and NH
* 3 reactions were combined into 1 reaction:
hcn+oh<=>hnco+h
hcn+oh<=>hocn+h
hocn+h<=>h+hnco
17 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Yoshikawa & Reitz,SAE 2008-01-2413
1818
Influence of Soot Radiation on Combustion and NOx
Computational meshSandia Optical Engine
BW: measured
Colored: prediction
18 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Yoshikawa & Reitz,2009
Musculus, SAE 2005-01-0925
0
2
4
6
8
-15 -10 -5 0 5 10 15 20SOI [CAD]
Max
SIN
L[a
.u.]
Model w/ radiation
Musculus (2005)
0
20
40
60
80
100
120
140
-15 -10 -5 0 5 10 15 20SOI [CAD]
NO
x[g
/kgf
uel]
Musculus (2005)
0
10
20
30
40
50
60
70
80
-15 -10 -5 0 5 10 15 20SOI [CAD]
NO
x[g
/kgf
uel]
Model w/o radiation
Model w/ radiation
Model w/o soot and radiation
Measured
soot
Predicted
“NOx bump”
“NOx bump” not observed in prediction, butreduction in predicted NOx seen with retard ofSOI (~ SOI=8 CAD ATDC)Radiation lowers predicted NOx ~ 7.5 %Absence of soot lowered predicted NOx ~ 2.5 %NOx model underpredicts measured NOxMagnitude sensitive to turbulent Schmidt #
Influence of Soot Radiation on Combustion and NOx
19 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Yoshikawa & Reitz,2009
2
3
4
5
6 7 8 9 10 11gIMEP [bar]
NO
x[m
g/cy
cle]
Experiment12-step NOxGRI-Mech 3.0Improved reduced NOx12-step NOx w/o radiation
Measured and predicted engine-outNOx as a function of load
(Sandia experiments)
ERC 12-step
Species4
(N, NO,N2O,NO2)
Reactions12
ERC 12-step +HCN, CH 6 27
ERC 12-step +HCN, CH, NH3,HNCO, NH2, NH
10 49
GRI v2.11 29 197
GRI v3.11 32 235
20 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Yoshikawa & Reitz, SAE 2008-01-2413
Smith, GRI-mech, 2005
Soot Modeling at ERC
Soot models
Two-step modelMulti-step
Phenomenological(MSP) model
PAH chemistry
Patterson, SAE 940523Kong, ASME 2007Vishwanathan & Reitz, SAE2008-01-1331Vishwanathan & Reitz,2009
Kazakov & Foster, SAE 982463Tao, 2009Tao, SAE 2006-01-0196Tao, 2006Vishwanathan & Reitz, SAE
2008-01-1331
Vishwanathan &Reitz, CST 2010
Models of soot formation/oxidation – Kennedy, Prog. Energy Comb. Sc., 1997Soot processes in engines - Tree and Svenson, Prog. Energy Comb. Sc., V2007
21 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
ssf so
d(M )=M -M
dt
0.5sf sf sf C2H2M =A P exp(-E /RT) M
so nsc ss nom
6M = W M
ρD
Two-step model
Hiroyasu sootformation
Nagle and Strickland-Constable (NSC)
oxidation
Net soot mass
C2H2 soot precursor
ρs = Soot density = 2 g/cm3
Dnom = assumed nominal soot diameter
= 25 nm
Wnsc = NSC oxidation rate/area
Mc2h2 = C2H2 Mass, Ms = Mass of soot
22 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
“tuning” constant
Hiroyasu & Kadota, SAE 760129Nagle & Strickland-Constable, 1962
SANDIA spray chamber:
Vishwanathan & Reitz,SAE 2008-01-1331
C2H2 inception occurs at lift-off location
Inclusion of PAH chemistry needed for accurate prediction of soot form/oxid.
Soot mass comparison
0
0.5
1
1.5
2
0 20 40 60 80 100 120Distance from Injector (mm)
Soot
Mas
s(m
icro
gms)
Expt.Model
Model predicted soot inception location→ Lift-off length position
Performance of two-step soot model
23 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Pickett & Siebers, 2004
HCHO flame soot
10 mm 90 mm
100 mm0 mm
Heptaneinjection
C2H2 inception occurs at lift-off location
Inclusion of PAH chemistry needed for accurate prediction of soot form/oxid.
Performance of two-step soot model
24 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Sandia experiment
Model
Vishwanathan & Reitz,SAE 2008-01-1331
Pickett & Siebers, 2004
Soot Modeling
25 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Reduced PAH mechanismReduced PAH mechanism of Xi & Zhong, 2006 basedon detailed mechanism of Wang &Frenklach, 1997 wasintegrated (20 species and 52 reactions)A1 formation through propargyl radical (C3H3)Higher aromatics formed through HACA scheme(hydrogen abstraction, carbon addition)
Reaction Arrhenius parameters-A, n, E. (Units of A in mole-cm-sec-K and units of E in cal/mole)
C3H3 + C3H3 → A1 2.0E+12, 0.0, 0.0
A1- + C4H4 ↔ A2 + H 2.50E+29, -4.4, 26400.0
A1+ A1-↔ P2 + H 1.10E+23, -2.9, 15890.0
A2-1 + C4H4 ↔ A3 + H 2.50E+29, -4.4, 26400.0
A1C2H* + A1 ↔ A3 + H 1.10E+23, -2.9, 15890.0
A3-4 + C2H2↔ A4 + H 3.00E+26, -3.6, 22700.0
A1 = benzene, A2 = naphthalene, P2 = biphenyl, A3 = phenanthrene, A4= pyrene, A1- = phenyl,A2-1 = 1-naphthyl, A3-4 = 4-phenanthryl, A1C2H* = phenylacetylene radical
Vishwanathan & Reitz, ASME 2009
26 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Amount of dry-carbon mass locked-up in aromatic precursors smallcompared to measured soot
PAH species
0 20 40 60 80 1001E-5
1E-4
1E-3
0.01
0.1
1Expt. soot mass
A4
A3
A2
A1
C2H2
Soo
t/Car
bon
mas
sin
prec
urso
rs(
g)
Distance from Injector (mm.)
15% O2
X=0 mm X=85 mm
Soot mass fraction
15% O2, A3 is precursor
Expt.
CFD
Improvement in soot location
Reduced PAH mechanism implemented considering up to 4 aromatic rings (pyrene)- A3 (Phenanthrene) as precursor for formation
~ peak of 0.016 ppm
27 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Vishwanathan & Reitz, ASME 2009
Sandia expts: Pickett & Idicheria, 2006
Soot model implementation in KIVA
1. Soot inception through A4:
2. C2H2 assisted surface growth:
3. Soot coagulation:
1 1 1ω -1= k [A ], k = 2000 {s }4
2 2 2 2 2
p
ω { }
N { }p
{
4 -1= k [C H ], k = 9.0 10 exp(-12100/T) S s
2 -1S = πd cm
1/36Y ρc(s)
d = cm}πρ Nc(s)
Surface area perunit volume
Particle size
Graphitization
YC(S) = soot mass fraction
N = soot number density (per cc)
ρC(S) = 2.0 gm/cm3
MC(S) = MW of carbon
Kbc = Boltzmann’s constant
Ca = agglomeration constant = 9
1ωC H (A ) 16C(s) + 5H16 10 4 2
2ωC(s) +C H 3C(s) + H2 2 2
3ωnC(s) C(s)n
3
1/6 1/26M ρY6K Tc(s) c(s) 1/6 11/6 -3 -1bcω = 2C [ ] [N] {particles cm s }a πρ ρ Mc(s) c(s) c(s)
Mono –disperse locally: All soot in a comp. cell have same diameter
28 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Vishwanathan & Reitz, CST 2010
Leung CNF 1991
Leung CNF 1991
4. O2 assisted soot oxidation (NSC model):
5. OH assisted oxidation (Modified Fenimore and Jones model):
4c(s)
K PA O12 -3 -12ω = x+K P (1-x) S {mol cm s }B OM 1+K P 2Z O2
x = P (P + (K /K ))T BO O2 2-2 -1 -1K = 30.0 exp (-15800/T) {g cm s atm }A
-3 -2 -1 -1K = 8.0 10 exp (-7640/T) {g cm s atm }B5 -2 -1K = 1.51 10 exp (-49800/T) {g cm s }T
-1K = 27.0 exp (3000/T) {atm }Z
-1/25 OH OH
-3 -1ω = (12) 10.58 γ X T S {mol cm s }
x = fraction of A sites
(1-x) = fraction of B sites
PO2 = partial pressure of O2
KA,B,T,Z = rate constants
XOH = mole fraction of OH
γOH = OH collision efficiency = 0.13
41 ωC(s) + O CO22
52
1ωC(s) + OH CO + H
2
Soot model implementation in KIVA
29 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Vishwanathan & Reitz, CST 2010
Fenimore & Jones, 1967
6. PAH-assisted surface-growth
k = number of carbon atoms and j = number of hydrogen atoms,
γks = 0.3 is the collision efficiency between soot and PAH, βks = collision frequency,
di = collisional diameter of PAH, dA = size of single aromatic ring = 1.393√3 Ǻ,
μi,j = Reduced mass of colliding species = Mass of PAH,
mi = mass of PAH expressed in terms of number of carbon atoms - k
Most models consider only mono-aromatic benzene as growth species.
6ωk,j 2 6 ks ks k,j
jC(s) + PAH C(s+k) + H , ω = γ β PAH N
2
2 3 -1bcks p PAH
i,j
πK Tβ = 2.2 (d + d ) cm s
2 μ
iPAH A
2md = d
3
Soot model implementation in KIVA
30 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Vishwanathan & Reitz, CST 2010
7. Transport equations:
M = ρYc(s) (soot species density) and N (number density) with N being treatedas passive species
Thermophoresis term implemented as a source term
dnuci = 1.25 nm (~100 carbon atoms)
MM μ M μ T
M ξM SSC ρ ρ T
vt
πηξ=0.75 (1+ ) , η = 0.9
8
M 1 2 6 4 5 c(s)-3 -1S = 16ω+ 2ω +6ω - ω - ω M {g cm s } for ρYc(s)
M 1 3
Mc(s) -3 -1S = 16ω - ω {particles cm s } for NMnuci
π 3M = d ρ nuci nuci c(s)6
Thermophoresis Source termsdiffusionconvection
Soot model implementation in KIVA
31 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Vishwanathan & Reitz, CST 2010
Soot mass and particle diameter predictions
22 20 18 16 14 12 10 8 60
10
20
30
40
50
60
70
80
90
100
Squares - amb = 30 kg/m3
Triangles - amb = 14.8 kg/m3
Expt. (Pickett and Idicheria, 2006)Mech-1 + PAH-1 without PAH induced growthMech-2 + PAH-1 without PAH induced growthMech-2 + PAH-1 with PAH induced growth
Tot
also
otm
ass
inje
t(
g)
Ambient % O2
PAH-1 (21 species and 52 reactions)PAH-2 (21 species and 208 reactions)
0 5 10 15 20 25 30 350
5
10
15
20
25
dnoz
= 100
%S
oot
ma
ss
dp (nm)
Pinj
= 190 MPa
Pinj
= 140 MPaP
inj= 90 MPa
Pinj
= 40 MPa
Effect of injection pressure
32 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Vishwanathan & Reitz, CST 2010
SANDIA optical engine – HTC/LTC
Engine Parameter
Bore x stroke (cm) 13.97 x 15.24
Speed (rpm) 1200
Compression ratio (CR) 11.2:1
Swirl ratio 0.5
Number of nozzle holes 8
Orifice diameter (mm) 0.196
Included angle 152°
Fuel Diesel #2
Sector angle 45
HTC-diff./premixed
LTCEarly/late
Amb. O2 % 21 12.7
SOI -7/-5 -22/0
Pin (bar) 2.33/1.92 2.14/2.02
Tin (C) 111/47 90/70
Fuel (mg) 61 56
Pinj (bar) 1200 1600
Expt. Data: Singh, IJER 2007
33 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Vishwanathan & Reitz, CST 2010
SANDIA optical engine – HTC/LTC
HTC-Diffusion
LTC-Early inj.
Diffusion to premixed combustion, soot ↓
HTC to LTC, soot ↓
In-cylinder soot formation/oxidation
Difference in HTC and LTC soot amountswell captured
-10 -5 0 5 10 15 20 25 30 35 40 45 500
2
4
6
8
10
12
14
16
18
20 HTC-DiffusionHTC-Long ignition delayLTC-Early injectionLTC-Late injection
Solid - Expt. (Singh et al. 2007)Dashed - Model Predicted
In-c
ylin
ders
oot(
g/kg
-f)
CAD ATDC
-50 -40 -30 -20 -10 0 10 20 30 40 500
2
4
6
8
10 Expt. (Singh et al. 2007)Model Predicted
CAD ATDC
Pre
ssur
e(M
Pa)
0200400600
8001000120014001600180020002200
2400H
RR
(J/D
eg)
-50 -40 -30 -20 -10 0 10 20 30 40 500
2
4
6
8
10
HR
R(J
/Deg
)
Expt. (Singh et al. 2007)Model Predicted
Pre
ssur
e(M
Pa)
CAD ATDC
0
100
200
300
400
500
600
700
800
900
1000
34 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions
Vishwanathan & Reitz, CST 2010
Summary and Future directions
Integration of soot model with multi-component vaporization and chemistry models
Extension to GDI and H/P/RCCI
Organic fraction modeling:OF correlates with premixedness
Soot diameter comparisons with TEMmeasurements obtained from variouscombustion modes
InceptionH2 +
C2H2 assisted surfacegrowth
Coagulation
Coagula
tion
Oxidation by OH
Oxidation by O2
+ CO+ H2
Gasoline/Diesel
Fuel-aromatic assisted
surface growth
H2 +
Need development/improvement
Fuel breakdown + fuelaromatic led PAH growth
35 CEFRC6 June 28, 2012
Hour 6: Heat transfer, NOx and Soot Emissions