1. University of Wisconsin Engine Research Center Diesel Stoichiometric Combustion SANGSUK LEE & Rolf D. REITZ Motivation  Diesel engines face difficulties in satisfying emission regulations, especially reducing NOx emissions.  Three-way catalyst is an well-established technology with gasoline engines.  Can the three-way catalyst be used with diesel engines? Fuel Economy is top priority! Emissions Objectives  To explore characteristics of rich diesel combustion  To achieve Diesel Stoichiometric Combustion with acceptable fuel economy impact  To identify achievable level of fuel consumption under stoichiometric operation with current strategies  To evaluate the effects of operating parameters on diesel stoichiometric characteristics Combustion Phasing on Fuel Consumption Operating Conditions Emissions under phi = 1.0 Effects of Op. Parameters on Fuel Consumption under stoichiometric Operation Split Injection under phi = 1.0 Conclusions  Combustion regimes don’t have significant effect on fuel consumption as  becomes richer.  7% fuel consumption disadvantage at  = 1.0 1.Fuel consumption and emissions characteristics are determined mostly by the equivalence ratio under rich diesel combustion. 2.PCCI combustion showed a low level (0.2 g/kW-hr) of soot emission even at stoichiometric operation. 3.Stoichiometric operation yielded ISFC levels of about 245 g/kW-hr which is around 7% higher than that of the best fuel economy case under leaner standard diesel operation. 4.High boost pressure and injection pressure improved fuel consumption under stoichiometric operation while high swirl ratio sacrificed fuel consumption. 5.Phasing of the heat release rate had only a minor influence on the fuel consumption since better phasing was accompanied by longer burn durations which canceled the gain. 6.PCCI based split injections under stoichiometric operation did not have significant fuel economy advantage while split injections with late injection impacted fuel economy due to improper air entrainment of 2 nd spray. ParameterBaselineRange Engine Speed 2000 rpm Boost Pressure 130kPa110 ~ 140 kPa Injection Pressure 150 MPa90 ~ 150 MPa Intake Air Temp. 90 °C40 ~ 90°C Fuel Mass16.0 mg/cyc15 ~ 20 mg/cyc Start of Injection - 35, -15°ATDC-35 ~ -5 ° ATDC Swirl Ratio1.851.85 ~ 3.3 EGR50%35 ~ 60% Injector Nozzles 130° (8-hole) 400 cm 3 / 30 min under 100bar Spray Included Angle ISFC (g/kW-hr) = 307 – 0.38xBoost P. – 0.21x Inj. P. + 5.82xSwirl – 0.11xSOI + 0.11xFuel Mass– 0.06xIntake Temp. Linear Regression* (R 2 = 80%) * Minitab Boost Pressure ~ Injection Pressure > Swirl > Fuel Mass ~ SOI ~ Intake Temp. ~  Boost P.Inj. P.SwirlSOI Fuel Mass Intake Temp. UnitkPaMPa ° BTDC mg/cyc °C°C Range110~14090~1501.8~3.35~3515~2140~90 Effect 11.4  12.4  8.7  3.3  0.7  3.0  Operating Parameters BASE Boost Press (140kPa). SOI (-15’ATDC) T air (40’C) Peak HRR (°ATDC) -4.50 0.751.00 Burn Duration (°CA) 5.004.7513.757.00 Heat Rejection Efficiency (%) 64 65 ISFC (g/kW-hr) 248244246243  Same Levels of ISFC and Heat rejection efficiency  Shifted combustion phasing doesn’t improve work conversion efficiency and fuel consumption. Boost P. Inj. P.SwirlSOI Engine Load Intake Temp. Unit kPaMPa ° BTDC mg/cyc °C°C Range 110~14090~1501.8~3.35~3515~2140~90 NOx 0.26  0.01  0.07  0.12  0.40  0.19  Soot 0.45  0.24  0.61  1.13  0.82  0.75  CO 3.70  17.3  0.23  37.5  24.9  13.4  HC 0.28  3.4  0.03  4.9  14.1  5.3  Red : Significant Effect > 2  Blue : Moderate Effect >  Black : negligible Effect<  ISFC 4.7% % Fuel Energy Wasted with CO and HC Emissions SOI = -35 & -15’ ATDC SOI = -35 & 15’ ATDC