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Optimization and Low Temperature Combustion

Optimization and Low Temperature Combustion 20
Part 8: Optimization and Low Temperature Combustion 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 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion 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 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Shi, 2011 Overview of optimization techniques Enumerative or exhaustive Calculus or gradientbased “local” methods which search in the neighborhood of current design point Random “global” methods such as genetic algorithms (GA) which typically converge on a global optimum Univariate (onefactoratatime) Design of Experiments (DOE) Twolevel factorial designs (main and interaction effects) Response surface methods (RSM) Statistical model building 3 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Senecal, 2000 Genetic algorithms “Individuals” are generated through random selection and a “population” is produced A model is used to evaluate the fitness of each individual The fittest individuals are allowed to “reproduce” A new “generation” is formed “mutations” are allowed through random changes The fitness criteria thins out the population and the most fit solution is achieved over successive generations 4 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Goldberg, 1989 Carrol, 1996 Implementation of algorithm Senecal, 2000 Binary representation of parameters X “genes” X X X 1 2 3 10101101 01101 01001001 “chromosome” gene string  XX i,max i,min  Precision  2 1 Evaluate merit f (X) for each generation member identify “fittest” Binary tournament selection Bitswapping “Crossover” Parent 1 Parent 2 01100100 1110110101011 10101101 0110101001001 Bitflipping 10101101 1110110101011 Random “mutation” 01100100 0110101001001 Descendants 5 CEFRC48, 2014 swirl ratio NOx g/kgf Part 8: Optimization and Low Temperature Combustion Liu, 2006 Coello, 2001 Optimization methodology MultiObjective Genetic Algorithm Nonparametric Regression Technique 0.3 All Citizens Produced 208 0.3 Pareto Citizens 0.28 204 0.26 0.25 0.24 200 0.22 0.2 196 0.2 192 0.15 1.0 0.18 0.5 0.1 0.9 0.8 1.5 0.2 0.8 2.5 0.3 0.6 0.16 0.4 3.5 0.7 4.5 0.5 0.6 0.4 0.6 0.2 0.7 Regression technique suitable for handling Simultaneous optimization of many irregular and undesigned data sets objectives 1 (e.g., GA data) 2 No merit function required to drive search Utilizes otherwise discarded optimization Pareto front offers more information than data a single optimum Captures magnitude of effects AND the shape of their response 6 CEFRC48, 2014 bowl diameter Soot g/kgf NOx g/kgf GISFC g/kWhrPart 8: Optimization and Low Temperature Combustion Genzale, 2007 Example optimization piston bowl design Parameters and Objectives Optimize: 7 Geometry Parameters: NOx Soot Pip height ISFC Bowl diameter f of bowl bottom 4 curvature control points Injector Spray Angle Swirl Ratio 7 CEFRC48, 2014 NOx g/kgf Part 8: Optimization and Low Temperature Combustion Genzale, 2007 Pareto front designs All Citizens Bowl geometry or injection 300 Pareto Citizens targeting trends 280 NOx ↓68 260 Soot ↑77 swirl = 0.7 GISFC ↑15 240 220 NOx ↓57 2.0 200 1.6 Soot ↑6 swirl = 1.4 1.2 GISFC ↓0 180 0.8 0.1 0.2 0.4 0.3 0.4 0.0 0.5 ↓45 NOx ↓30 Soot swirl = 3.1 GISFC ↓2 NOx ↓5 Soot ↓42 swirl = 3.1 GISFC ↓6 8 CEFRC48, 2014 Soot /kgf GISFC g/kWhrbowl diameter ( bore) spray angle spray angle Part 8: Optimization and Low Temperature Combustion Genzale, 2007 Regression – Identify dominant design parameters Regression fits performed for each design on the Pareto front • 3 dominant design parameters identified: 1. Spray angle 2. Swirl ratio 3. Bowl diameter 0.8 1.4 2 1.2 0.6 1.5 1 1 0.4 0.8 0.5 4.5 0.2 0.6 0 0.6 0.6 3.5 0.5 50 50 0.65 55 55 1.5 60 0.7 0.4 2.5 60 65 0.75 65 2.5 70 70 1.5 0.8 0.2 75 75 3.5 0.85 80 80 0.5 0.9 4.5 85 0 85 9 CEFRC48, 2014 pip height ( bowl depth) swirl ratio swirl ratio soot g/kgf soot g/kgf soot g/kgfbowl diameter ( bore) spray angle Part 8: Optimization and Low Temperature Combustion Genzale, 2007 Regression – Understand Parameter Effects 0.8 2 0.6 1.5 swirl = 3.1 1 0.4 0.5 NOx ↓45 4.5 0.2 0 0.6 Soot ↓30 0.5 3.5 50 0.65 55 1.5 0.7 2.5 60 ↓2 GISFC 0.75 2.5 65 70 1.5 0.8 3.5 75 0.85 80 0.5 0.9 4.5 85 Response Surface Observations: An optimal spray angle is predicted. Increased swirl ratio is predicted to enhance soot reduction near the optimal spray angle. Increases soot emissions at narrow spray angles. Increased swirl ratio is predicted to decrease soot at all bowl diameters. 10 CEFRC48, 2014 swirl ratio swirl ratio soot g/kgf soot g/kgfPart 8: Optimization and Low Temperature Combustion Klingbeil, 2003 Optimization of LTC low temperature combustion Increased interest in advanced combustion regimes RCCI, HCCI, PCCI, MK offer simultaneous reduction of NOx and soot Challenges High CO, HC High loads Transients NOx EGR Soot 11 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Kokjohn, 2009 Combustion optimization fuel and EGR selection HCCI simulations used to choose optimal EGR rate and PRF 100 (isooctane/nheptane) blend 1 6 91 b b b a aa r IMEP r IMEP r IMEP MISFIRE Net ISFC 100 100 100 90 28 bar/deg At 6, 9, and 11 bar IMEP MISFIRE g/kWhr MISFIRE 80 230 16 160 1300 rev/min 250 24 bar/deg 80 80 80 bar/deg. 240 70 180 g/kWhr 180 170 g/kWhr 230 As load is increased the minimum 190 60 10 bar/deg. 60 60 60 ISFC cannot be achieved with 50 200 180 g/k5.6 Whr 10 210 190 g/kWhr bar/deg. 40 bar/deg. either neat diesel fuel of neat 40 40 210 40 30 gasoline 190 190 g/kWhr 220 20 180 g/kWhr 20 20 20 Predicted contours are in good 10 170 190 200 agreement with HCCI g/kWhr 0 0 0 0 0 10 20 30 40 50 60 0 0 0 10 10 10 20 20 20 30 30 30 40 40 40 50 50 50 60 60 60 experiments EGR Rate EGR Rate EGR Rate EGR Rate EGR Rate 12 CEFRC48, 2014 PRF PRF PRF PRF PRF Part 8: Optimization and Low Temperature Combustion Kokjohn, 2009 Charge preparation optimization 100 to 1500 bar Inj. 1 Pressure Premixed and Direct Injected fuel blending 100 to 1500 bar Inj. 2 Pressure Desirable to use traditional diesel SOI 1 IVC to (SOI220) ºATDC type injector 50 to 30 ºATDC SOI 2 Large nozzle hole (250 μm) Wide angle (145° included angle) 0 100 Diesel Fuel Fuel split ncells KIVA + MultiObjective Genetic 2 m PRF PRF      i i GLOBAL Algorithm (MOGA) i1 NSD  PRF ncells Fuel reactivity and EGR from HCCI PRF m GLOBAL  i investigation (9 bar IMEP) i1 0.30 Results Global PRF = 65 Film () All Sol utions 0.45 EGR rate = 50 0.28 PRF Inhomogeneity 0.19 Pareto Solutions Five optimization parameters 0.26 Minimize two objectives Parameters Wall film amount 0.24 Inj. Pres. 1 (bar) 115 Inj. Pres. 2 (bar) 555 PRF Inhomogeneity 0.22 SOI1 (°ATDC) 67 Simulations run to 10 °BTDC SOI2 (°ATDC) 33 0.20 21 generations with a population size Fraction in first pulse 0.64 of 24 0.18 0 1 2 3 4 5 6 7 8 Wall Film of Total Fuel 13 CEFRC48, 2014 PRF Inhomogeneity Part 8: Optimization and Low Temperature Combustion Kokjohn, 2009 Optimized Reactivity Controlled Compression Ignition (RCCI) Port injected gasoline Optimized fuel blending incylinder Direct injected diesel Gasoline Squish Ignition Conditioning Source Diesel 80 to 50 45 to 30 Crank Angle (deg. ATDC) Gasoline Diesel 14 CEFRC48, 2014 Injection SignalPart 8: Optimization and Low Temperature Combustion Heavy and lightduty ERC experimental engines LD HD Engine Heavy Duty Light Duty Engine CAT SCOTE GM 1.9 L Displ. (L/cyl) 2.44 0.477 Bore (cm) 13.72 8.2 Stroke (cm) 16.51 9.04 Squish (cm) 0.157 0.133 CR 16.1:1 15.2:1 Swirl ratio 0.7 2.2 IVC ( ATDC) 85 and 143 132 ° EVO(°ATDC) 130 112 Injector type Common rail Nozzle holes 6 8 Hole size (µm) 250 128 Engine size scaling Staples, 2009 15 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Hanson, 2010 Experimental validation HD Caterpillar SCOTE IMEP (bar) 9 Effect of gasoline percentage Speed (rpm) 1300 Experiment 14 1400 Simulation 82 EGR () 43 12 1200 89 76 10 1000 Equivalence ratio () 0.5 Neat Diesel Fuel 89 8 800 Gasoline Intake Temp. (°C) 32 Neat 6 600 Gasoline Intake pressure (bar) 1.74 4 400 Gasoline ( mass) 76 82 89 2 200 Diesel inject press. (bar) 800 0 0 30 20 10 0 10 20 30 SOI1 (°ATDC) 58 Crank ATDC SOI2 (°ATDC) 37 st Fract. diesel in 1 pulse 0.62 IVC (ºBTDC)/Comp ratio 143/16 Computer modeling predictions confirmed Combustion timing and Pressure Rise Rate control with diesel/gasoline ratio Dualfuel can be used to extend load limits of either pure diesel or gasoline 16 CEFRC48, 2014 Pressure MPa Apparent Heat Release Rate J/Part 8: Optimization and Low Temperature Combustion Hanson, 2011 Splitter, 2010 RCCI – high efficiency, low emissions, fuel flexibility Heavyduty RCCI (gas/gas+3.5 2EHN, 1300 RPM) Heavyduty RCCI (E85/Diesel, 1300 RPM) Indicated efficiency of 58±1 Heavyduty RCCI (gas/diesel 1300 RPM) achieved with E85/diesel 0.3 HD Target (2010 Levels) Emissions met incylinder, 0.2 without need for aftertreatment 0.1 Considerable fuel flexibility, 0.0 including ‘single’ fuel operation 0.03 HD Target (2010 Levels) Diesel can be replaced with 0.02 0.5 total cetane improver 0.01 (2EHN/DTBP) in gasoline 0.00 less additive than SCR DEF 57 54 51 48 45 4 6 8 10 12 14 16 Gross IMEP bar 17 CEFRC48, 2014 Gross Ind. Soot NOx Efficiency g/kWhr g/kWhrPart 8: Optimization and Low Temperature Combustion Kokjohn, 2011 Dual fuel RCCI combustion – controlled HCCI RCCI Heat release occurs in 3 stages (SAE 2010010345, 2012010375) Cool flame reactions result from diesel (nheptane) injection First energy release occurs where both fuels are mixed Final energy release occurs where lower reactivity fuel is located Changing fuel ratios changes relative magnitudes of stages Fueling ratio provides “next cycle” CA50 transient control 200 95 Cool Flame PRF Burn Isooctane Burn 90  nheptane Primarly  Primarly  150 + entrained isooctane nheptane CA50=2 ˚ ATDC 85 isooctane 80 100 75 70 50 65 RCCI 60 0 SOI = 50 ATDC 20 10 0 10 20 55 o 80 90 100 110 120 130 140 150 160 170 Crank ATDC o 18 Intake Temperature C 18 CEFRC48, 2014  o AHRR J/ Delivery Ratio isooctanePart 8: Optimization and Low Temperature Combustion Splitter, 2010 Understanding RCCI combustion Lo Loca catio tion n B B w wiit th dummy h dummy Optical Cylinder Head pl plug in ug insta stall lled ed comm common on ra rail il in injec jector tor Port Fuel Injector Lo Loca catio tion n A A fib fiber er to to comm common on ra rail il w wiit th opti h optics cs FTIR FTIR fuel fuel spra spray y in insta stall lled ed 19 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Splitter, 2010 Understanding RCCI combustion 10 10 10 10 400 400 400 400 10 400 Experiment Ex Ex Ex Expe pe pe perim rim rim rimen en en entttt Simulation Simulat Simulat Simulat Simulation ion ion ion 8 8 8 8 320 320 320 320 8 320 Location B 6 6 6 240 240 240 6 6 240 240 4 4 4 4 4 160 160 160 160 160 2 2 2 2 2 80 80 80 80 80 0 0 0 0 0 0 0 0 0 0 20 20 20 15 15 15 10 10 10 5 5 5 0 0 0 5 5 5 10 10 10 15 15 15 20 20 20 20 20 15 15 10 10 5 5 0 0 5 5 10 10 15 15 20 20 Crank Crank Crank Crank Crank     ATDC ATDC ATDC ATDC ATDC 11 deg 7 d 3 d 3 deg A eg A eg A A TDC TDC TDC TDC 16 deg ATDC Pr Pr Prod od oduct uct ucts s s Pr Prod oduct ucts s Reactant Reactant Reactant Reactant Reactants s s s s Location A B B B B B Experimental incylinder FTIR measurements of combustion process at two locations Spectra shows different fuel species at locations A and B, a result of the reactivity gradient Fuel decomposition and combustion products form A A A A A at a slower rate at location B, extending combustion duration 2300 2300 2300 2300 2700 2700 2700 2700 3100 3100 3100 3100 3500 3500 3500 3500 3900 3900 3900 3900 2300 2700 3100 3500 3900 Wav Wav Wavel el elen en ength ( gth ( gth (nm) nm) nm) Wav Wavel elen ength ( gth (nm) nm) 20 CEFRC48, 2014 Pressure MPa Press Press Press Pressure ure ure ure M M M MPa Pa Pa Pa Heat Release Rate J/ H H H Heat eat eat eat R R R Releas eleas eleas elease e e e Rat Rat Rat Rate e e e J J J J////    Part 8: Optimization and Low Temperature Combustion Kokjohn, 2012 RCCI optical experiments Engine Cummins N14 Bore x stroke 13.97 x 15.24 cm Displacement 2.34 L Geometric compression ratio 10.75 RCCI experiments in Sandia heavyduty optical engine LED illumination through side windows to visualize sprays Images recorded through both piston GDI crown and upper window Isooctane Crankangleresolved hightemperature 100 bar 7x150 micron chemiluminescence with highspeed CMOS camera Commonrail Shortwave pass filter to reject long nheptane wavelength (green through IR) soot 600 bar 8x140 micron luminosity Inc. Ang. 152° 21 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Kokjohn, 2011 RCCI combustion luminosity imaging Load: 4.2 bar IMEP GDI SOI: 240°ATDC Speed: 1200 rpm CR SOI: 57°/37° ATDC Intake Temperature: 90° C Equivalence ratio: 0.42 Intake Pressure: 1.1 bar abs. Isooctane mass : 64 Bowl window Squish (upper) window 22 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Kokjohn, 2013 Lightduty drivecycle performance Compare conventional diesel combustion Combustion Chamber Geometry (CDC) and Reactivity Controlled Compression Ignition (RCCI) combustion Compare at same operating conditions (CR, boost, IMT, swirl..) ERC KIVAChemkin Code Reduced primary reference fuel used Engine specifications to model diesel and gasoline kinetics Base engine type GM 1.9 L Suite of improved ERC spray models Bore (mm) 82 Stroke (mm) 90.4 Diesel fuel injector specifications Connecting rod length (mm) 145.5 Type Bosch common rail Squish height (mm) 0.617 Actuation type Solenoid Displacement (L) 0.4774 Included angle 155° Compression ratio 16.7:1 Number of holes 7 Swirl ratio 1.5 to 3.2 Hole size (µm) IVC (°ATDC) 141 132° EVO (°ATDC) 112° 23 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Kokjohn, 2013 Comparison between RCCI and conventional diesel Adhoc fuels working group 12 Five operating points of Adhoc fuels SAE 2001010151 working group 10 Size shows relative Tier 2 bin 5 NOx targets from 5 weighting Cooper, SAE 2006011145 8 (assumes 3500lb Passenger Car) 6 4 Evaluate NOx / fuel efficiency 4 2 tradeoff using SCR for CDC 3 2 1 Assumptions Diesel exhaust fluid (DEF) 0 1000 1500 2000 2500 3000 consumption is 1 per g/kWhr Speed rev/min NOx reduction Speed IMEP CDC Baseline NOx Target Johnson, SAE 2011010304 Mode (rpm) (bar) NOx (g/kgf) (g/kgf) 1 1500 2 1.3 0.2 No penalty for DPF regeneration 2 1500 3.9 0.9 0.4 UHC and CO only contribute to 3 2000 3.3 1.1 0.3 reduced work 4 2300 5.5 8.4 0.6 5 2600 9 17.2 1.2 Baseline CDC Euro 4: Hanson, SAE 2012010380 24 CEFRC48, 2014 IMEP bar gPart 8: Optimization and Low Temperature Combustion Kokjohn, 2013 Euro 4 operating conditions conventional diesel CDC Operating Conditions Model validation Mode 1 2 3 4 5 IMEPg (bar) 2.3 3.9 3.3 5.5 9 Speed (rev/min) 1500 1500 2000 2300 2600 Total Fuel (mg/inj.) 5.6 9.5 8 13.3 20.9 Intake Temp. (deg. C) 60 60 70 67 64 Intake Press. (bar abs.) 1 1 1 1.3 1.6 EGR Rate () 47 38 42 25 15 CR Inj. Pressure (bar) 330 400 500 780 1100 Pilot SOI advance (°CA) 7 7 11 15 18 Main SOI (° ATDC) (actual) 0.9 0 0.1 0.5 1.8 Percent of DI fuel in Pilot () 20 15 15 10 10 100 100 100 100 100 100 100 100 Experiment Experiment Mode 2 Mode 5 Mode 3 Simulation Mode 4 Simulation 80 80 80 80 80 80 80 80 Experiment Experiment Simulation Simulation 60 60 60 60 60 60 60 60 40 40 40 40 40 40 40 40 20 20 20 20 20 20 20 20 0 0 0 0 0 0 0 30 20 10 0 10 20 30 40 50 0 30 20 10 0 10 20 30 40 50 Crank deg. ATDC 30 20 10 0 10 20 30 40 50 30 20 10 0 10 20 30 40 50 Crank deg. ATDC Crank deg. ATDC Crank deg. ATDC Baseline CDC Euro 4: Hanson, SAE 2012010380 25 CEFRC48, 2014 Cylinder Pressure bar Cylinder Pressure bar AHRR J/deg. Cylinder Pressure bar AHRR J/deg. Cylinder Pressure bar AHRR J/deg. AHRR J/deg.Part 8: Optimization and Low Temperature Combustion Kokjohn, 2013 Model validation (Euro 4) Cycle average emissions and performance 3.5 42 Comparison at 5 Modes Experiment Experiment 3 Simulation 30 Simulation 40 Experiment Simulation 2.5 20 38 2 10 36 Tier 2 Bin 5 1.5 0 34 1 2 32 1.5 0.5 1 0 30 EINOx EISoot GIE 0.5 Optimized CDC with SCR for Tier 2 Bin 5 0 100 100 ExperimentEuro 4 45 Mode 3 Simulation Euro 4 CDC optimized 80 80 CDC Peak GIE 40 GIE has higher 60 60 35 allowable PPRR (advanced SOI) 40 40 30 1 2 3 4 5 than Euro 4 Mode 20 calibration 20 5 E Weight Weighted  imode imode imode=1 0 E  0 average: cycle 5 20 10 0 10 20 30 40 Weight  imode Crank deg. ATDC imode=1 26 CEFRC48, 2014 EISoot g/kgf GIE EINOx g/kgf Cycle NOx and Soot g/kgf Cylinder Pressure bar AHRR J/deg. Cycle GIE Part 8: Optimization and Low Temperature Combustion Kokjohn, 2013 Comparison between RCCI and conventional diesel “CDC Peak GIE” point shown for reference (does not meet NOx target) CDC and RCCI efficiency sensitive to selected value of peak PRR Maximum allowable PRR of CDC points set at 1.5 times higher than for RCCI CDC RCCI CDC RCCI CDC RCCI CDC RCCI CDC RCCI Mode 1 2 3 4 5 IMEPg (bar) 2.3 3.9 3.3 5.5 9 Speed (rev/min) 1500 1500 2000 2300 2600 Total Fuel (mg/inj.) 5.6 9.5 8 13.3 20.9 Intake Temp. (deg. C) 60 60 70 67 64 Intake Press. (bar abs.) 1 1 1 1.3 1.6 EGR Rate () 47 61 38 0 42 0 25 0 15 36 Premixed Gasoline () 0 0 0 65 0 48 0 79 0 90 CR Inj. Pressure (bar) 330 500 400 500 500 500 780 500 1100 500 Pilot SOI advance (°CA) N/A 7 16 7 21 11 21 15 18 21 Main SOI (° ATDC) Baseline 0.9 17 0 37 0.1 37 0.5 60 1.8 37 Main SOI (° ATDC) Peak GIE 4.6 N/A 1.3 N/A 4.1 N/A 3.6 N/A 8 N/A Main SOI (° ATDC) Bin 5 SCR N/A N/A N/A N/A N/A 4.6 1.3 4.1 2 6.3 Percent of DI fuel in Pilot () 20 42 15 60 15 60 10 0 10 60 DEF () 0.6 0 0.4 0 0.5 0 2.1 0 4.9 0 27 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Kokjohn, 2013 RCCI vs. CDC + SCR CDC optimization with SCR CDC (with SCR) Main injection timing swept DEF consumption 1 per 1 g/kWhr Euro 4 reduction in NOx Work 180 to 180 GIE100 Total m m LHV   DEF Fuel Fuel Peak efficiency at tradeoff between fuel consumption (SOI timing) and DEF consumption (engineout NOx) RCCI (No SCR needed) Gasoline amount controls CA50 to meet NOx/PRR constraints Mode 1 uses diesel LTC (i.e., no gasoline and EGR is added) Mode 5 has EGR for phasing control 28 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Kokjohn, 2013 Comparison of efficiency, NOx and PRR 2 Target NOx at Tier 2 Bin 5 10 RCCIBin5 RCCI meets NOx targets without DEF CDCPeak GIE CDCEuro4 w/o SCR 1 10 DEF NOx aftertreatment has small CDCBin5+SCR efficiency penalty at lightload (2 to 4 0 bar IMEP) and moderate EGR (40) 10 DEF penalty is larger above 5 bar IMEP where EGR is below 40 1 10 RCCI 2 10 9 RCCIBin5 CDCPeak GIE 8 CDCEuro4 w/o SCR CDCBin5+SCR 7 6 5 4 RCCI 3 2 1 Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 29 CEFRC48, 2014 Tailpipe NOx g/kgf Peak PRR bar/degPart 8: Optimization and Low Temperature Combustion Kokjohn, 2013 Cycle averaged NOx, Soot and GIE RCCI and CDC compared at baseline and Tier 2 Bin 5 NOx CDC NOxGIE tradeoff controlled by main injection timing RCCI meets NOx targets without after treatment RCCI gives 8 improvement in fuel consumption over CDC+SCR RCCI soot is an order of magnitude lower than CDC+SCR RCCI HC is 5 times higher than CDC+SCR Currently addressing methods to reduce HC emissions Creviceoriginated HC emissions Splitter, SAE 2012010383 Thermal barrier coated piston 30 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Splitter, 2014 Combustion  97 PPRR 12 (bar/CA) 70 Optimizing RCCI efficiency 28 29 30 32 33 34 36 35 65 Heavyduty SCOTE engine 60 20 21 23 24 25 27 19 26 55 IMEPn (bar) 8.45±.05 50 CA50 (°CA ATDC) 0.5±.5 45 10 11 12 13 15 17 18 Speed (rev/min) 1300 40 Piston Bowl Shape Bathtub 35 1 1 1 2 3 4 5 6 7 8 9 1 6 1 Cr () 14.88:1 4 30 0.25 0.30 0.35 0.40 0.45 0.50 DI Timing (°CA ATDC) 60/35  Global  DI Bias (SOI1, SOI2) 60/40 GTE vs. intake pressure temperature PFI Timing (°CA ATDC) 320 70 Comb.  97 GTE 65 PPRR 12 (bar/CA) EGR () 0 0.55 60 Intake Temperature (°C) 3266 (varied) 0.54 55 0.54 Intake Pressure (bar) 1.312.18 (varied) 0.53 50 Exhaust Pressure (bar) Fixed turbo. η 0.53 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.545 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 45 0.52 Overall Turbo η () 65 (simulated) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.525 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 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Temperature (C) Intake Temperature (C)Φ Premixed () Part 8: Optimization and Low Temperature Combustion Splitter, 2014 Premixed vs. global  intake temp Lines of Constant Intake Temperature 66 C 57 C ( C) 70 42 C Comb.  97  Premixed 65 PPRR 12 (bar/CA) 0.22 60 0.20 32 C 55 0.18 50 0.16 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.20 0 0 0 0 0 0 0 0 0.14 45 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.18 8 8 8 8 8 8 8 8 0.12 40 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.16 6 6 6 6 6 6 6 6 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.14 4 4 4 4 4 4 4 4 35 Φ Global () 30 0.25 0.30 0.35 0.40 0.45 0.50  Global () CA50 TDC Fueling: DI=3 2EHN in 91 PON gas PFI=E85 Highest GTE occurs at lean conditions with 63 of charge fully premixed 32 CEFRC48, 2014 Intake Temperature (C)Part 8: Optimization and Low Temperature Combustion Splitter, 2013 Limits of dualfuel RCCI efficiency Calibrate 0D code with Exp. GT GT CR=14.88 experiments POWER POWER Use code to determine 14.88 14.88 18.6 Compression ratio conditions needed to reach 8.00 7.86 8.69 60 GTE IMEPn (bar) Fueling (mg/cyc) 87.13 87.13 87.13 Results: 60 GTE possible with: 54.3 54.5 59.7 Gross Therm Eff. () High Cr 52.0 52.1 57.5 Net Therm Eff. () Lean operation (Φ0.3) 45.3 45.1 49.1 BTE () 50 reduction in 1.03 1.0 1.2 FMEP (bar) heat transfer Convection HX N/A 0.4 0.2 combustion losses Comb. Eff. () 98 98 99 • Deactivate underpiston Intake Pressure (bar) 1.5 1.5 1.68 oil jet cooling Exhaust Pressure (bar) 1.625 1.625 1.75 Turbo eff. (air filter + 67.5 62.3 72.8 DOC) 33 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Splitter, 2013 GTE with / without oil jet cooling • Largest advantage in GTE observed at lean conditions • High GTE Realized Close to 60 EGR, Matched Φ′=.253 Operation 1 0.036 0.031 0.083 0.086 0.9 0.388 0.380 0.8 0.294 0.305 0.7 0.6 0.5 0.4 0.3 0.590 0.576 0.2 0.1 0 Cooling No Cooling Oil Matrix Points Oil Matrix Points 53, 59,61,6466,68 8385,9294 GTE EX HX Comb 34 CEFRC48, 2014 Fraction of Fuel Energy ()Part 8: Optimization and Low Temperature Combustion Splitter, 2013 Ultrahigh efficiency dualfuel RCCI combustion IMEPg IMEPn GTE () NTE () (bar) (bar) EXP (pt. 83) 59.1 6.82 55.0 6.27 GT Power HX =0.2 58.8 6.79 54.8 6.25 High efficiency demonstrated GT Power HX =0.4 56.7 6.55 52.8 6.02 Simulation heat transfer tuned to EXP, Squirter off, 43 EGR, Oil Matrix Point 83 E85 / 3 EHN+91 PON RCCI GTPower, HX=0, 100 comb. , 43 EGR match data 43C intake, 42 EGR, GTPower, HX=0, 100 comb. , 0 EGR 6.3 bar IMEPn 150 750 14.88:1 required HX = 0.4 135 18.7:1 required HX = 0.3 120 600 105 (Pancake 1.2 less surface area) 90 450 18.7:1 w/o oil cooling HX = 0.2 75 GTE IMEPg NTE IMEPn 60 300 () (bar) () (bar) 45 Experiment 59.1 6.82 55.0 6.27 30 150 Model, HX =0 15 62.4 7.12 58.5 6.85 100 comb. η 0 Model, HX =0 0 15 100 comb.η, 63.4 7.23 61.0 6.95 40 30 20 10 0 10 20 30 40 0 EGR Crank Angle (CA ATDC) 94 of maximum theoretical cycle efficiency achieved Splitter, “RCCI Engine Operation Towards 60 Thermal Efficiency”, SAE 2013010279 35 CEFRC48, 2014 Pressure (bar) AHRR (J/ CA)Part 8: Optimization and Low Temperature Combustion Lim, 2014 Extending RCCI load range High load RCCI attempt with gasoline/diesel leads to HCCI Conventional RCCI: Low reactivity fuel (i.e., gasoline or isooctane) is port injected, and high reactivity fuel (i.e., diesel or nheptane) is directinjected. • 21bar IMEP requires 245mg of fuel. • 3.42bar, 90°C, 46EGR IVC, 1800 rev/min leads to HCCI combustion when isooctane is portinjected. • Use two direct injectors to provide more flexibility 36 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Lim, 2014 Extending RCCI load range Independent Stratification of Reactivity and Equivalence Ratio with Dual Direct Injection 37 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Lim, 2014 Extending RCCI load range Allows utilization of piston geometry • IVC condition: 3.42bar, 90°C, 46EGR • Direct injection of isooctane can place fuel in different locations at different timings. • The stock piston geometry creates 2 combustion zones. – Squish with high surface:volume ratio – Bowl with low S:V ratio • If fuel is placed in the squish region, its reaction rate can be controlled by heat transfer to the walls. 38 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Lim, 2014 Extending RCCI load range • Use NSGA (Nondominated Sorting Genetic Algorithms) II searchbased global optimization tool – Searching for designs of 6 parameters to reduce 6 objectives: soot, NOx, CO, UHC, ISFC, and Ringing intensity – Total fuel mass: 245mg – 1800 rev/min Relatively small nheptane mass Design Parameters Range nheptane mass mg 0 to 20 nheptane injection close to TDC nheptane SOI ATDC 40 to 0 Premixed isooctane 0 to 60 st Isooctane in 1 inj. 0 to 50 DI Isooctane SOI 1 ATDC 143 to 50 1 injection into squish DI Isooctane SOI 2 ATDC 50 to 0 1 injection into bowl 39 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Lim, 2014 Extending RCCI load range GA search for optimum injection strategy US 2010 Emission Targets Soot: 0.01g/kWhr NOx: 0.26g/kWhr Optimum Design Parameters Soot g/kWhr 0.015 Premixed isooctane mass mg 2.8 NOx g/kWhr 0.058 DI Isooctane mass 1 mg 118.8 CO g/kWhr 0.73 DI Isooctane mass 2 mg 115.0 UHC g/kWhr 1.13 nheptane mass mg 8.4 ISFC g/kWhr, IVC→EVO 174.7 DI Isooctane SOI 1 ATDC 126.8 η , BDC→BDC 48.7 g 2 DI Isooctane SOI 2 ATDC 49.7 Ringing Intensity MW/m 10.2 nheptane SOI ATDC 16.7 PPRR bar/deg 12.6 40 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Lim, 2014 Extending RCCI load range Combustion control mechanism nd 2 injection into bowl, separating squish and st bowl 1 injection into squish Combustion starts from nheptane. Squish region remains cooler Squish combustion starts later 41 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Lim, 2014 Extending RCCI load range Source of emissions Soot from liner NOx from ignition site CO from liner UHC from ring pack crevice 42 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Lim, 2014 Extending RCCI load range Conclusions • With 2 independent direct injectors RCCI combustion becomes possible at high load conditions. st • Larger mass of 1 isooctane injection at 80°ATDC is most effective in squish “cooling.” nd • 2 injection timing sweeps show that earlier injection is more effective in lowering ringing intensity. • nheptane injection mass and timing is most effective for combustion control. • Further study of piston geometry and injection direction is necessary. 43 CEFRC48, 2014 Part 8: Optimization and Low Temperature Combustion Summary and conclusions CFD modeling can be integrated with efficient optimization techniques for improved engine design New combustion strategies can be discovered using CFDoptimization Reactivity Controlled Compression Ignition strategy explained and validated with engine experiments Dual fuel and singlefuel (with additive) RCCI provides combustion control using optimized blending of port and directinjected fuels RCCI offers high thermal efficiency and meets EPA NOx and soot emissions mandates incylinder, without the need for aftertreatment RCCI HCCI 44 CEFRC48, 2014
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