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Heat transfer, NOx and Soot Emissions

Heat transfer, NOx and Soot Emissions 16
Part 4: Heat transfer, NOx and Soot Emissions Reciprocating Internal Combustion Engines Prof. Rolf D. Reitz Engine Research Center University of WisconsinMadison 2014 PrincetonCEFRC Summer School on Combustion Course Length: 15 hrs (Mon. Fri., June 23 – 27, 2014) Copyright ©2014 by Rolf D. Reitz. This material is not to be sold, reproduced or distributed without prior written permission of the owner, Rolf D. Reitz. 1 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Short course outine: Engine fundamentals and performance metrics, computer modeling supported by indepth understanding of fundamental engine processes and detailed experiments in engine design optimization. Day 1 (Engine fundamentals) Part 1: IC Engine Review, 0, 1 and 3D modeling Part 2: Turbochargers, Engine Performance Metrics Day 2 (Combustion Modeling) Part 3: Chemical Kinetics, HCCI SI Combustion Part 4: Heat transfer, NOx and Soot Emissions Day 3 (Spray Modeling) Part 5: Atomization, Drop Breakup/Coalescence Part 6: Drop Drag/Wall Impinge/Vaporization/Sprays Day 4 (Engine Optimization) Part 7: Diesel combustion and SI knock modeling Part 8: Optimization and Low Temperature Combustion Day 5 (Applications and the Future) Part 9: Fuels, Aftertreatment and Controls Part 10: Vehicle Applications, Future of IC Engines 2 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Challen, 1998 Engine heat transfer Up to 30 of the fuel energy is lost to wall heat transfer Can influence engine ignition/knock Engine durability – catastrophic engine failure Scorching Detonation Cracking 3 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Han, 1995 Wang, 2012 Heat transfer Gas phase energy equation I  c s r uI p u J Q Q Q  t q Radiation source term w   u Dy r y Dyu / Qrr I,4Ω dΩ Ir   b  Ω4 wall Wall heat flux (account for compressibility) With radiation Without radiation   C u T ln T T 2.1y 33.34 G uC u T ln T T  g p g g w p g g w q q w w   2.1ln y 2.5 2.1ln y 2.5   T  g 2.1uT ln g  dT q 2.1  T w dT w   2.1G    dy  C y   gp dy yy 2.1ln 2.5   r G radiative heat flux = q w 4 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Wiedenhoefer, 2003 Radiation modeling Radiation Transfer Equation:  s Ω Ir,Ω a Ir,Ω Ir Sr,Ω  net s b 4 a net absorption coefficient, scattering coefficient net s   a extinction coefficient net s 4 T w Back body radiative flux (independent of angle) I r  b   Scattering terms, , S usually neglected compared to absorption s Radiation intensity at wall r 4  G q nΩ Ir,Ω dΩT  ww   nΩ0 surface emissivity  Discrete ordinates model nDir  r m m Q r I r 4 I r   b   m1 5 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Wiedenhoefer, 2003a Soot and gas absorption 1 a T, P, L ln 1 T, P, L Total absorption coefficient  g e g e  L e a  a a 1 1 1 1 1 net soot COH O   22 fuel CO CO H O 22 Soot absorption 1 CO absorption bands a1260C T m 2 soot soot Wide band model for CO and H O 2 2 3  2C 1  ,T  b band center  CT 2 e1  band center Importance of soot: 1 a aT gas soot T  r 4 35  Qrr a I,4Ω dΩ Ir a a T   TT  b gas soot   gas soot  Ω4 6 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Wiedenhoefer, 2000 Wall heat transfer Conjugate heat transfer modeling ERC Heat Conduction in Components code (HCC) Iterative coupling between HCC and CFD code Unstructured HCC Mesh 7 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Wiedenhoefer, 2000 Wall heat transfer Cummins N14 engine . . . . . . . . . Caterpillar SCOTE engine Cut Plane 8 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Wiedenhoefer, 2003 Predicted piston temperature CDC No Radiation Run 1 740 F = 0.7 Effect of radiation on wall heat loss Run 2 Run 3 720 Total heat loss increased by 30 due to With Radiation 700 Run 1 radiation. Run 2 680 Run 3 34 head, 19 liner, 47 piston. 660 Lowers bulk gas temperatures 640 Results in lower NOx and higher soot 620 NOx reduced by as much as 30 (ave) 600 16 F = 0.5 580 Uniform Temp / No rad 14 Nonuniform Temp / With Rad 560 F = 0.7 20 15 10 5 0 12 Uniform Temp / No rad Start of Injection, ATDC Nonuniform Temp / With Rad 10 8 6 4 2 20 15 10 5 0 Startofinjection, ATDC 9 CEFRC24, 2014 Peak Piston Temperature K NOx g/kWhPart 4: Heat transfer, NOx and Soot Emissions Gingrich, 2014 Wall heat flux measurements Dry Compressed Chilled Air Water Engine Geometry AVL 415S Smoke Base Engine GM 1.9L Diesel Choked Flow Meter Compression Ratio 16.3 Orifices Water Heater Displacement (Liters) 0.477 Horiba Stroke (mm) 90.4 Hydrocarbon Bore (mm) 82 Analyzer EGR Heat Exchanger Intake Valve Closing 132° aTDC Exhaust Valve Opening 112° aTDC Horiba Analyzers Swirl Ratio 1.5 4.8 NOx Stock (Re DC Dyno Air CO Piston Bowl Type entrant) Heater O2 Port Fuel Injectors Exhaust CO2 Intake CO2 Included Spray Angle 20° Port Swirl Barrel 4 Fuel Injection Pressure (bar) 2 to 10 Direct Control Heater Injectors Injector Rated Flow (cc/sec) 10 Valves 3 Intake Bosch Common Rail Injector Exhaust Surge 2 Surge Tank Number of Holes 7 Tank 1 Hole Diameter (mm) 0.14 Included Spray Angle 155° 4cylinder engine head Injection Pressure (bar) 250 to 1000 bar cylinder 1,3,4 deactivated 10 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Gingrich, 2014 Thermocouples 5 7 1 Power 6 Piston Converter 4 Transmitter 2 Primary Coil 3 (Engine Mounted) Data Inductive Secondary Acqusition Power Coil Supply (Piston Mounted) Receiver • Fourier analysis is applied to find dynamic heat flux • Integral of the dynamic heat flux over the full cycle is zero T(t) T A cos(n t) B sin(n t) m n n Dynamic Steady N kn q (TT ) k (A B )cos(n t) (A B )sin(n t) m l n n n n l 2 n1 11 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Gingrich, 2014 Combustion strategy effects CDC / HCCI / RCCI Mode 1 Mode 2 Mode 3 Mode 4 Speed (RPM) 1490 1900 2300 2300 IMEPg (bar) 4.2 5.7 5.7 8 CA50 (degATDC) 4 5 4.5 8 Swirl 1.5 1.5 1.5 1.5 Intake Temperature (C) 75 50 50 35 Intake Pressure (kPa) 115 130 130 188 ERG () 0 0 0 55 Regime Fuel Fuels: HCCI 91PON Gasoline / nheptane RCCI F76 / 91PON Gasoline CDC F76 12 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Gingrich, 2014 Heat Release Rate 150 Combustion strategy effects Heat release rate Location 3 Temperature Mode 3 100 150 5.7 bar IMEPg CDC 5 deg ATDC CA50 HCCI 145 50 2300 rev/min RCCI 140 0 135 20 10 0 10 20 30 40 Crank Angle deg 6 Location 3 6 Location 7 x 10 130 x 10 5 5 T =169.1C T =191.8C m m T =155.4C 125 4 T =182.1C 4 m m T =140.6C T =158.5C m m 3 3 120 400 200 0 200 400 Crank Angle deg 2 2 1 1 0 0 20 10 0 10 20 30 40 20 10 0 10 20 30 40 Crank Angle deg Crank Angle deg 13 CEFRC24, 2014 2 Heat Flux W/m Temperature C 2 Heat Flux W/m AHRR J/degLocation 7 Location 7 6000 6000 Part 4: Heat transfer, NOx and Soot Emissions Gingrich, 2014 5000 5000 Combustion strategy effects CDC / HCCI / RCCI Location 3 Location 7 4000 4000 6000 6000 CDC CDC 3000 3000 HCCI HCCI 5000 5000 RCCI RCCI 2000 2000 4000 4000 CDC CDC 1000 1000 3000 3000 HCCI HCCI RCCI RCCI 0 0 1 2 3 4 1 2 3 4 2000 2000 Mode Mode 1000 1000 0 0 1 2 3 4 1 2 3 4 Mode Mode Heat losses significantly less with low temperature combustion strategies 14 CEFRC24, 2014 2 Integrated Heat Flux J/m 2 Integrated Heat Flux J/m 2 Integrated Heat Flux J/m 2 Integrated Heat Flux J/m Part 4: Heat transfer, NOx and Soot Emissions Hendricks, 2014 Heavyduty diesel heat flux data Compare CDC and RCCI combustion at matched CDC CA50, load, Φg (4.6°CA ATDC, 0.35) RCCI piston heat flux measured to be lower than CDC Area integrated HX and temp. determined RCCI CDC RCCI 7.7 5.9 ∫Piston HX fuel energy () GTE () 51.2 52.7 15 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Engine emissions transportation toxic air pollutants 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 size PM2.5, fine particles: 2.5 μm in size or less 3.) Carbon monoxide (CO), 4.) Sulfur dioxide (SO2), 5.) Nitrogen oxides (NOx), 6.) Lead (Pb) Toxic air pollutants Hazardous Air Pollutants or HAPs known to cause or suspected 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, 1,3butadiene, formaldehyde, acrolein, acetaldehyde, and diesel particulate matter (DPM). Harmful effects on the central nervous system: BTEX/N/S benzene, toluene, ethylbenzene, xylenes, Naphthalene, Styrene 16 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Curtis, 2014 Engine emissions transportation toxic air pollutants 17 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Diesel emission solutions – Selective Catalytic Reduction (SCR) and Diesel Particulate Filter (DPF) US EPA 2010 HD soot: 0.0134 g/kWhr NOx: 0.2682 g/kWhr. 1.) EGR Navistar – no SCR Enabling technologies (Cost): Improved combustion bowl design PCCI Improved EGR valves, airhandling, VVA Twinseries turbochargers, interstage cooling Highpressure CR fuel injection (31,800 psi) 2.) SCR Cummins CuZeolite with DEF for 2010 Claim 35 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/gal Volvo 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 18 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Yoshikawa, 2008 NOx modeling Zeldo’vich thermal NOx mechanism Rate controlling step due to high N bond strength 2 ERC 12step NOx model is based on GRIMech v3.11 and includes: Zeldovich, 1946 Thermal NOx Fenimore, 1979 Prompt NOx around 1000 K. Extensions Eberius, 1987 NO can convert HCN and NH 3 Guo, 2007 Interaction between NO and Soot 19 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Kong, 2007 ERC 12 step NOx Mechanism SENKIN2 used to predict species histories. XSENKPLOT used to visualize reaction pathways and identify important reactions and species. Reduced mechanism validated for test temperatures from 700K to 1100 K and equivalence ratios from 0.3 to 3.0. Four additional species (N, NO, N O, NO ) 2 2 and 12 reactions added to ERC PRF mechanism Detailed mechanism: Smith, GRImech, 2005 20 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Kong, 2007 ERC 12 step NOx mechanism Diesel spray computations Comparison of NOx predictions (T=900K, P=3.7MPa) N NO N O 2 N O NO O 2 N + OH NO H N O O N O 2 2 2 N O O 2NO 2 N O H N OH 22 N O OH N HO 2 2 2 N O M N O M 22 HO NO NO OH 22 NO O M NO M 2 NO O NO O 22 NO H NO OH 2 GRI mechanism results Reduced mechanism results Detailed mechanism: Smith, GRImech, 2005 21 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Yoshikawa, 2008 CH radical and HCN bridge in fuelrich regions Constant volume SENKIN Competing analysis with ERC nheptane mechanism GRI ver.3 NOx C H group x y mechanism φ=1.0 φ=3.0 N group Absolute Flux normalized to NO by XSENKPLOT T =769K ini P =40bar ini Time=100ms 22 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Influence of soot radiation on combustion and NOx BW: measured Musculus, 2005 Colored: prediction Yoshikawa, 2009 23 23 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Yoshikawa, 2009 Influence of soot radiation on combustion and NOx 8 140 120 Musculus (2005) soot 6 100 80 4 “NOx bump” 60 40 Model w/ radiation 2 20 Musculus (2005) Measured 0 0 15 10 5 0 5 10 15 20 15 10 5 0 5 10 15 20 SOI CAD SOI CAD 80 Model w/o radiation “NOx bump” not observed in prediction, but 70 Model w/ radiation Model w/o soot and radiation reduction in predicted NOx seen with retard of 60 SOI ( SOI=8 CAD ATDC) 50 40 Radiation lowers predicted NOx 7.5 30 Absence of soot lowered predicted NOx 2.5 20 NOx model underpredicts measured NOx 10 Predicted Magnitude sensitive to turbulent Schmidt 0 15 10 5 0 5 10 15 20 SOI CAD 24 CEFRC24, 2014 NOx g/kgfuel NOx g/kgfuel Max SINL a.u.Part 4: Heat transfer, NOx and Soot Emissions Kittelson, 1998 Particulate emissions Regulated emissions PM2.5 New challenge engines must meet particulate numberbased regulations (PN). Euro 6: PN limit 6.0e11 particles/km for vehicles produced after 2017. California Air Resources Board (CARB) LEV III: Total PM mass: 3.8 mg/km for 2014 and 1.9mg/km for 2017 PN: 3.8e12 and 1.9e12 particle/km. Greatest health risk fine particles can lodge deeply into the lungs 25 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Soot modeling at the ERC Soot models Multistep Twostep model PAH chemistry Phenomenological (MSP) model Kazakov Foster, SAE 982463 Patterson, SAE 940523 Vishwanathan Tao, 2009 Kong, ASME 2007 Reitz, CST 2010 Vishwanathan Reitz, SAE Tao, SAE 2006010196 Tao, 2006 2008011331 Vishwanathan Reitz, SAE 2008 Vishwanathan Reitz, 2009 011331 Models of soot formation/oxidation – Kennedy, Prog. Energy Comb. Sc., 1997 Soot processes in engines Tree and Svenson, Prog. Energy Comb. Sc., V2007 26 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Twostep model “tuning” constant Hiroyasu soot 0.5 M =APexp(E /RT)M sf sf sf C2H2 formation Nagle and Strickland 6 M =  W M Constable (NSC) so nsc s ρD s nom oxidation d(M ) s Net soot mass =M M sf so dt C H soot precursor 2 2 3 ρ = Soot density = 2 g/cm s D = assumed nominal soot diameter nom = 25 nm Hiroyasu Kadota, SAE 760129 W = NSC oxidation rate/area Nagle StricklandConstable, 1962 nsc M = C H Mass, M = Mass of soot c2h2 2 2 s 27 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2008 Performance of twostep soot model Pickett, 2004 SANDIA spray chamber: Soot mass comparison Model predicted soot inception location 2 → Liftoff length position 1.5 Expt. 1 Model 0.5 0 0 20 40 60 80 100 120 Distance from Injector (mm) C H inception occurs at liftoff location 2 2 Inclusion of PAH chemistry needed for accurate prediction of soot form/oxid. 28 CEFRC24, 2014 Soot Mass (micro gms)Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2008 Performance of twostep soot model 90 mm 10 mm Sandia experiment Pickett, 2004 Heptane injection Model HCHO flame soot Vishwanathan, 2008 0 mm 100 mm C H inception occurs at liftoff location 2 2 Inclusion of PAH chemistry needed for accurate prediction of soot form/oxid. 29 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Phenomenological soot models 30 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2009 Reduced PAH mechanism Reduced PAH mechanism of Xi Zhong, 2006 based on detailed mechanism of Wang Frenklach, 1997 was integrated (20 species and 52 reactions) A formation through propargyl radical (C H ) 1 3 3 Higher aromatics formed through HACA scheme (hydrogen abstraction, carbon addition) Reaction Arrhenius parametersA, n, E. (Units of A in mole cmsecK and units of E in cal/mole) C H + C H → A 2.0E+12, 0.0, 0.0 3 3 3 3 1 A + C H ↔ A + H 2.50E+29, 4.4, 26400.0 1 4 4 2 A + A ↔ P + H 1.10E+23, 2.9, 15890.0 1 1 2 A 1 + C H ↔ A + H 2.50E+29, 4.4, 26400.0 2 4 4 3 A C H + A ↔ A + H 1.10E+23, 2.9, 15890.0 1 2 1 3 A 4 + C H ↔ A + H 3.00E+26, 3.6, 22700.0 3 2 2 4 A = benzene, A = naphthalene, P = biphenyl, A = phenanthrene, A = pyrene, A = phenyl, 1 2 2 3 4 1 A 1 = 1naphthyl, A 4 = 4phenanthryl, A C H = phenylacetylene radical 2 3 1 2 31 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2009 PAH species Reduced PAH mechanism implemented considering up to 4 aromatic rings (pyrene) A (Phenanthrene) used as precursor for soot formation model 3 C H 2 2 Expt. soot mass 1 Sandia expts: Pickett Idicheria, 2006 15 O , A is precursor 2 3 0.1 A 1 Expt. 0.01 A 15 O 1E3 2 2 Soot mass fraction 1E4 A 3 CFD A 4 1E5 0 20 40 60 80 100 X=0 mm X=85 mm peak of 0.016 ppm Distance from Injector (mm.) Improvement in soot location Amount of drycarbon mass lockedup in aromatic precursors small compared to measured soot 32 CEFRC24, 2014 Soot/Carbon mass in precursors (g)Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2010 Soot model implementation ω 1 C H (A )  16C(s) + 5H 1. Soot inception through A : Graphitization 16 10 4 2 4 1 ω = kA , k = 2000 s 1 1 1 4 ω 2 Leung, 1991 2. C H assisted surface growth: C(s) +C H  3C(s) + H 2 2 2 2 2 4 1 ω = kC H , k = 9.010 exp(12100/T) S s 2 2 2 2 2 Y = soot mass fraction C(S) 2 1 Surface area per S = πd N cm N = soot number density (per cc) p unit volume 3 1/3 ρ = 2.0 gm/cm C(S)  6Y ρ c(s) M = MW of carbon  d = cm C(S) Particle size p  πρ N c(s) K = Boltzmann’s constant  bc C = agglomeration constant = 9 a Mono –disperse locally: All soot in a comp. cell have same diameter ω 3 Leung, 1991 nC(s)  C(s) 3. Soot coagulation: n 1/6 1/2  6M ρY 6K T c(s) c(s) 1/6 11/6 3 1 bc  ω = 2C N particles cm s 3 a  πρ ρ M c(s) c(s) c(s)  33 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2010 Soot model implementation 1 ω 4 C(s) + O CO 4. O assisted soot oxidation (NSC model): 2 2 2   KP AO 12   3 1 2 ω = x+K P(1x)S mol cm s 4  B O  M 1+K P 2 c(s)   Z O 2   x = P (P + (K /K )) OO TB x = fraction of A sites 22 2 1 1 (1x) = fraction of B sites K = 30.0exp (15800/T) g cm s atm A 3 2 1 1 P = partial pressure of O O2 2 K = 8.0 10 exp (7640/T) g cm s atm B K = rate constants 5 2 1 A,B,T,Z K = 1.51 10 exp (49800/T) g cm s T X = mole fraction of OH 1 OH K = 27.0exp (3000/T) atm Z γ = OH collision efficiency = 0.13 OH Fenimore, 1967 5. OH assisted oxidation (Modified Fenimore and Jones model): 1 ω 5 1/2 3 1 C(s) + OH CO + H ω = (12)10.58γXTS mol cm s 2 5 OH OH 2 34 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2010 Soot model implementation 6. PAHassisted surfacegrowth j ω 6  C(s) + PAH  C(s+k) + H , ω = γβ PAH N k,j 2 6 ks ks k,j  2 π K T 2 3 1 bc β = 2.2(d + d ) cm s  ks p PAH 2μ i,j 2m i d = d PAH A 3 k = number of carbon atoms and j = number of hydrogen atoms, γ = 0.3 is the collision efficiency between soot and PAH, β = collision frequency, ks ks d = collisional diameter of PAH, d = size of single aromatic ring = 1.393√3 Ǻ, i A μ = Reduced mass of colliding species = Mass of PAH, i,j m = mass of PAH expressed in terms of number of carbon atoms k i Most models consider only monoaromatic benzene as growth species. 35 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2010 Soot model implementation 7. Transport equations:    M μ M μ T πη  Mv ξ M S ξ=0.75 (1+ ) , η = 0.9   M  t SC ρ ρ T 8   convection Thermophoresis Source terms diffusion M = ρY (soot species density) and N (number density) with N being treated c(s) as passive species Thermophoresis term implemented as a source term 3 1 S = 16ω + 2ω +6ω ω ωM g cm s for ρY  M 1 2 6 4 5 c(s) c(s) M  c(s) 3 1  S = 16ω ω particles cm s for N M 1 3  M nuci  π 3 M =  d ρ nuci nuci c(s) 6 d = 1.25 nm (100 carbon atoms) nuci 36 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Jiao, 2014 Soot mass and particle diameter prediction Premixed charge SI engine particulate modeling 70,000 cells at BDC, including the intake and exhaust manifolds and cylinders. Spark plug: at center of cylinder head. Completely homogeneous fuel/air mixture at IVC Experiment: EPA Tier II EEE certification fuel, 28 aromatics. ERC KIVA code simulations: DPIK ignition model, GEquation combustion model. Fuel: isooctane/28 toluene by volume. MultiChem mechanism: ic8h18/nc7h16/c7h8/PAH (79 species 379 reactions) 37 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Jiao, 2014 Soot formation prediction 0.03 F; C/O 0.78; 0.26 0.98; 0.33 1.2 ; 0.41 1.3 ; 0.44 0.02 1.4 ; 0.48 1.5 ; 0.51 0.01 0.00 40 20 0 20 40 60 80 Crank Angle (deg) CAD 680 700 720 740 760 780 800 Predicted soot mass no longer reduces significantly after 80 ATDC. Soot produced at 80 ATDC increases with increase of φ. Soot formation dominates first and then soot oxidation begins to play a key role. Peak incylinder soot mass increases w/ an increase of φ. •38 38 CEFRC24, 2014 Incylinder soot (g/kgf) C H mass fraction () 2 2 G () Part 4: Heat transfer, NOx and Soot Emissions Jiao, 2014 TDC φ =1.5 3500 4 Incylinder temperature TDC 3000 3 G () 2500 2 2000 1 1500 0 burnt 1000 1 500 2 4 3 2 1 0 1 2 3 4 9 Radial position (cm) 4 2x10 6x10 A mass fraction TDC 4 4 5x10 9 C H mass fraction 2x10 2 2 4 4x10 C2H2 9 4 1x10 3x10 4 2x10 10 A4 5x10 4 1x10 burnt 0 0 4 3 2 1 0 1 2 3 4 Radial position (cm) 39 CEFRC24, 2014 A mass fraction () Temperature (K) 4 O , OH mass fraction () Particle size (nm) 2 Part 4: Heat transfer, NOx and Soot Emissions Jiao, 2014 TDC φ =1.5 6 1 4x10 10 Soot mass fraction 0 TDC 10 O mass fraction 6 O2 2 1 3x10 10 OH mass fraction 2 10 6 2x10 3 10 4 soot OH 6 10 1x10 5 10 burnt 6 0 10 4 3 2 1 0 1 2 3 4 Radial position (cm) 12 400 1x10 Number density 10 TDC 1x10 Particle size 8 300 nd 1x10 6 1x10 200 4 1x10 burnt 2 dp 1x10 100 0 1x10 2 0 1x10 4 3 2 1 0 1 2 3 4 Radial position (cm) 40 CEFRC24, 2014 3 Number density (/cm ) Soot mass fraction () O , OH mass fraction () 2 Particle size (nm) Part 4: Heat transfer, NOx and Soot Emissions Jiao, 2014 0 80 ATDC φ =1.5 6 4 1x10 1x10 Soot mass fraction 0 80 aTDC 7 5 8x10 O mass fraction 8x10 2 7 5 OH mass fraction soot 6x10 6x10 OH 7 5 4x10 4x10 7 5 2x10 2x10 0 0 O2 4 3 2 1 0 1 2 3 4 Radial position (cm) 500 8 Number density 0 1x10 80 aTDC Particle size 400 6 1x10 300 4 1x10 nd 2 200 1x10 dp 0 100 1x10 2 0 1x10 4 3 2 1 0 1 2 3 4 Radial position (cm) 41 CEFRC24, 2014 3 Soot mass fraction () Number density (/cm ) Part 4: Heat transfer, NOx and Soot Emissions Jiao, 2014 Particulate size distributions Simulation Experiment 1 10 10 1x10 1x10 referenceFC/O 9 expt 9 1x10 1x10   8 8 1x10 1x10   7 7 1x10  1x10 6 6 1x10 1x10 5 FC/O 1x10 5  1x10  4 1x10 4  1x10  3 1x10  3 1x10  2 1x10 2 10 100 1x10 10 100 d (nm) p d (nm) p For φ 1.4, shape of PSDs is very flat and broad, Nearly identical PSDs until about φ =1.3, which is different from experiment, but looks nd sharply declines with increase of dp. like PSDs for A/F of 14.6 for engine loads When φ 1.3, nd consistently increases lower than 4 bar in Ref. 2. with increasing φ , and decreases gradually For φ =1.4 and 1.5 , magnitude of nd of small particles are well represented, nd decreases with increasing dp. with increasing dp. 1 Hageman, 2013. 2 Maricq, 1999 42 CEFRC24, 2014 3 dN/dlog(d ) (/cm ) p 3 Averaged particle number density (/cm ) Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2010 Soot in stratified charge engines HTCdiff./ LTC SANDIA optical engine – HTC/LTC premixed Early/late Amb. O 21 12.7 Engine Parameter 2 SOI 7/5 22/0 Bore x stroke (cm) 13.97 x 15.24 P (bar) 2.33/1.92 2.14/2.02 in Speed (rpm) 1200 T (C) 111/47 90/70 in Fuel (mg) 61 56 Compression ratio (CR) 11.2:1 P (bar) 1200 1600 inj Swirl ratio 0.5 Number of nozzle holes 8 Orifice diameter (mm) 0.196 Included angle 152° Fuel Diesel 2 Sector angle 45 Expt. Data: Singh, 2007 43 CEFRC24, 2014 Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2010 SNL optical engine – HTC/LTC 10 1000 Expt. (Singh et al. 2007) Incylinder soot formation/oxidation Model Predicted 900 HTCDiffusion Difference in HTC and LTC soot amounts well 8 800 captured 700 6 600 500 20 HTCDiffusion 4 400 HTCLong ignition delay 18 300 LTCEarly injection LTCLate injection 2 200 16 100 14 Solid Expt. (Singh et al. 2007) 0 0 Dashed Model Predicted 50 40 30 20 10 0 10 20 30 40 50 12 CAD ATDC 10 Expt. (Singh et al. 2007) 10 2400 8 Model Predicted 2200 LTCEarly inj. 6 2000 8 1800 4 1600 2 6 1400 1200 0 10 5 0 5 10 15 20 25 30 35 40 45 50 1000 4 800 CAD ATDC 600 2 400 Diffusion to premixed combustion, soot ↓ 200 HTC to LTC, soot ↓ 0 0 50 40 30 20 10 0 10 20 30 40 50 Expt. Data: Singh, 2007 CAD ATDC 44 CEFRC24, 2014 Pressure (MPa) Pressure (MPa) HRR (J/Deg) HRR (J/Deg) Incylinder soot (g/kgf) Coagulation Fuelaromatic assisted surface growth Part 4: Heat transfer, NOx and Soot Emissions Summary and current directions Integration of soot model with multicomponent vaporization and chemistry models Fuel breakdown + fuel aromatic led PAH growth H + 2 Inception C H assisted surface Oxidation by O 2 2 2 growth Gasoline/Diesel + CO + H 2 Oxidation by OH H + 2 Need development/improvement Extension to GDI and H/P/RCCI Organic fraction modeling: OF correlates with premixedness Soot diameter comparisons with TEM measurements obtained from various combustion modes 45 CEFRC24, 2014 Coagulation
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