Potential of a Production DI Two-Stroke Engine Adapted for Range Extender and Motorcycle Applications JSAE 20179082 /SAE 2017-32-0082 Pierre DURET, IFP School, France Stéphane VENTURI & Antonio SCIARRETTA, IFPEN Nigel FOXHALL & Walter HINTERBERGER, BRP-Rotax
Potential of a Production DI Two-Stroke Engine Adapted for Range Extender and Motorcycle Application Production DI 2-Stroke for Range Extender Applications Production DI 2-Stroke for Motorcycle Applications Page 2 / 23
Potential of a Production DI Two-Stroke Engine Adapted for Range Extender and Motorcycle Application Production DI 2-Stroke for Range Extender Applications Production DI 2-Stroke for Motorcycle Applications Main objective of the 1st study to demonstrate the potential of the production based REX DI 2-stroke engine to meet Euro 6d and RDE NOx Emissions Standards without DeNOx Aftertreatment Page 3 / 23
Production DI 2-Stroke for REX Applications Vehicle specifications and hybrid architecture Main vehicle specifications (adapted from Segula Hagora vehicle project): Lightweight 3-seat mid-size vehicle Electric Vehicle with range extender 100 km full electric range Acceleration: 0-100 km/h < 10s Top speed: 150 km/h Range extender (REX) series hybrid architecture & energy flows 4 Page 4 / 23
Production DI 2-Stroke for REX Applications Thermal engine specifications Main engine modifications Exhaust opening Transfer opening Thermal engine specifications based on a 2-cylinder snowmobile ROTAX 600 HO engine High power / weight Longest stroke available DI 2-stroke engine Already equipped with direct fuel injection (E-Tec) Modified to reach efficiency & emissions of IFP experimental DI CAI 2-stroke data base With reduced ports opening duration for high torque at low speed and limited maximum speed 5 Production Rotax 600 HO 82 deg. CA ATDC 110 deg. CA ATDC Modified engine 110 deg. CA ATDC 125 deg. CA ATDC Max speed 7900 rpm 4500 rpm With exhaust throttling valves for CAI (Controlled Auto-Ignition) Page 5 / 23
Production DI 2-Stroke for REX Applications EURO 6d WLTC with single point strategy in REX mode Thermal engine power demand for the WLTC driving cycle Battery state of charge along the WLTC cycle 6 Page 6 / 23
Production DI 2-Stroke for REX Applications EURO 6d WLTC with single point strategy in REX mode WLTC with one single selected REX operating point & Euro 6d NOx emissions compliance 7 Page 7 / 23
Production DI 2-Stroke for REX Applications Euro 6d RDE with 2 points strategy in REX mode Example of RDE (Real Drive Emissions) driving cycle selected to undertake this project 8 Battery state of charge along the RDE cycle with 2 REX operating points Page 8 / 23
Production DI 2-Stroke for REX Applications Euro 6d RDE with 2 points strategy in REX mode The compliance with Euro 6d RDE NOx emissions is possible (even with a conformity factor of 1): when a fuel enrichment strategy is used for the higher load point with a rather limited penalty in average CO2 emissions 9 Page 9 / 23
Production DI 2-Stroke for REX Applications Conclusions Part 1 The purpose of this 1 st project: to demonstrate the potential of using an adapted DI production 2-stroke engine for EV range extender Its main issue: Euro 6d both on WLTC and in RDE without DeNOx The solution investigated: 2 engine operating points strategy with one lower load point in ultra-low NOx CAI combustion and a higher load point with enriched air-fuel mixture to minimize NOx emissions. All the existing production Rotax snowmobile engine hardware can be used with only some minor modifications : Simplification of the cylinder blocks with fixed and reduced exhaust & transfer ports opening duration Implementation of a two-position exhaust throttling valve for each cylinder. Two main associated positions for the intake throttle To experimentally test a production engine including such modifications could be the subject of further study 10 Page 10 / 23
Potential of a Production DI Two-Stroke Engine Adapted for Range Extender and Motorcycle Application Production DI 2-Stroke for Range Extender Applications Production DI 2-Stroke for Motorcycle Applications Main objective of the 2 nd study to demonstrate the potential of the production based motorcycle DI 2-stroke engine to meet Euro 4 & 5 Motorcycle Emissions Standards on the WMTC driving cycle without DeNOx aftertreatment Page 11 / 23
Production DI 2-Stroke for Motorcycle Applications Emissions standards for motorcycles Euro 4 and Euro 5 emissions limits for motorcycles WMTC driving cycle for L3e vehicles category (motorcycles) 12 Page 12 / 23
Production DI 2-Stroke for Motorcycle Applications Engine & Motorcycle Specifications 13 Example of motorcycles considered for the engine performance benchmark Page 13 / 23
Production DI 2-Stroke for Motorcycle Applications DI 2-Stroke engine specifications Engine specifications based on a 2-cylinder snowmobile ROTAX 600 HO engine High power / weight Longest stroke available DI 2-stroke engine Already equipped with direct fuel injection (E-Tec) Modified to reach efficiency & emissions of IFP experimental DI CAI 2-stroke data base With the RAVE (Rotax Adjustable Variable Exhaust) exhaust valve in the lower position below 5000 rpm for minimum exhaust port duration With exhaust throttling valves for ultra low NOx CAI (Controlled Auto-Ignition) 14 Page 14 / 23
Production DI 2-Stroke for Motorcycle Applications Methodology & Calculations BMEP/rpm engine operating points during the 3 parts of the WMTC driving cycle for the BMW F800 GS motorcycle 15 Page 15 / 23
Production DI 2-Stroke for Motorcycle Applications Methodology & Calculations 16 Correlation between the WMTC cycle, the CAI combustion range and the 5 engine test bench data used for the 5-point method The 5-point method with appropriate weighting factors gives a first estimation in hot conditions of fuel consumption and emissions on the WMTC cycle good correlation between the 5-point method and WMTC chassis dyno measurements: about 2% difference for NOx and fuel consumption Page 16 / 23
Production DI 2-Stroke for Motorcycle Applications Interest of gasoline CAI for 2-stroke motorcycle 17 5-point method comparison of the WMTC fuel consumption & NOx emissions of the base engine without & with CAI combustion strategy Implementation of CAI on points 2, 3 & 4 significant effect on fuel consumption reduction much lower effect on NOx emissions reduction because about 70 % of these emissions come from the higher load point 5 outside the CAI range far to be sufficient for meeting Euro 4 NOx levels Page 17 / 23
Production DI 2-Stroke for Motorcycle Applications Interest of gasoline CAI for 2-stroke motorcycle 5-point method comparison of the WMTC raw emissions of CO & HC of the base engine without & with CAI combustion strategy Implementation of CAI on points 2, 3 & 4 More complete combustion in CAI much higher effect on HC & CO emissions reduction because the high CO & HC emitter points 2, 3 & 4 are inside the CAI range reduced requirements in terms of oxidation catalyst conversion 18 Page 18 / 23
Production DI 2-Stroke for Motorcycle Applications Fuel enrichment strategy for NOx emissions control How to reduce the NOx emissions of the point 5? by applying a fuel enrichment strategy necessary to estimate the NOx emissions of the point 5 as a function of the Trapped Equivalence Ratio (test data) (estimation) = point 5 19 Measured and estimated NOx emissions versus Trapped Equivalence ratio at full load and 40% load (corresponding to the point 5) Page 19 / 23
Production DI 2-Stroke for Motorcycle Applications Fuel enrichment strategy for NOx emissions control 5-point method comparison of NOx emissions between: base engine base engine + CAI base engine + CAI + fuel enrichment 20 Fuel enrichment strategy for NOx emissions reduction of the point 5 Euro 4 NOx can now be reached with some margin with a point 5 trapped equivalence ratio of 1,21 (NOx emissions divided by 2) Euro 5 can be reached with a point 5 trapped equivalence ratio of 1,36. In such conditions, exhaust equivalence ratio close to 1 >>> it could even be beneficial to use a 3-Way cat formulation for further NOx emissions reduction Page 20 / 23
Production DI 2-Stroke for Motorcycle Applications Fuel enrichment strategy for NOx emissions control 5-point method comparison of fuel consumption between: base engine base engine + CAI base engine + CAI + fuel enrichment 21 Impact on the overall motorcycle fuel consumption: the fuel enrichment increases the overall fuel consumption by about 8 % compared to the case with CAI only the combination of CAI during Part 1 and Part 2 with fuel enrichment during Part 3 of the WMTC remains beneficial by about 8%. the slightly modified production DI 2-stroke engine has the potential to meet Euro 4 emissions limits, with some improvements in fuel consumption Page 21 / 23
Production DI 2-Stroke for Motorcycle Applications Conclusions Part 2 The purpose of this 2 nd project: to demonstrate the potential of using an adapted DI production 2-stroke engine for a 100 hp motorcycle application Its main issue: to meet the most stringent Euro 4 & Euro 5 NOx emissions limits on the new WMTC with conventional aftertreatment technology >>> without DeNOx The solution investigated: to combine CAI combustion at part load with an enriched air-fuel mixture strategy during the higher loads All the existing production Rotax snowmobile engine hardware can be used with only some minor modifications : Implementation of exhaust throttling valves close to the exhaust ports Implementation a small ECU-driven electric motor to control the position of these exhaust valves To experimentally test a production engine including such modifications could be the subject of further study 22 Page 22 / 23
ACKNOWLEDGMENTS The authors would like to particularly thank the following IFP School students who actively contributed to this work: Wassim HARB, Pierre LEMARIE, Arnaud LEURET and Edgar ZAHONERO who contributed to the range extender project, Zélia GOUX, Yannick MORENO, Bruno RS DE CAMARGO, Edouard SUILLAUD who contributed to the motorcycle project. 23 Page 23 / 23