Investigating Effects of Direct Injection During NVO on HCCI Combustion

1. Investigating Effects of Direct Injection During NVO on HCCI Combustion Effects of PreDI % Students: John Waldman, Dennis Nitz Advisor: Prof. David E. Foster Visiting Researchers: Takeru Ibara, Minoru Iida Funding by: Yamaha Motor Company Definitions • Negative Valve Overlap (NVO) – time during end of exhaust stroke and beginning of intake stroke when both intake and exhaust valves are closed • PreDI – Early Direct fuel injection during negative valve overlap • DI – Secondary Direct fuel injection during intake stroke • PI – Port fuel injection during intake stroke Single Cylinder Yamaha Research Engine Objectives Effects of PreDI% on HCCI combustion. Note: the combustion timing is advanced with higher percentages of PreDI. Also NOx emissions are more sensitive to changes in PreDI % at leaner AFR. • Outline HCCI operating regime • Study effects on HCCI combustion from varying: • PreDI percent of total fuel flow • PreDI timing and duration • PI and DI durations Effects of PreDI Timing PI Duration (usec) PI Duration (usec) Laboratory Schematic eTDC eTDC EVC EVC Baseline Operating Range Effects of PreDI timing with different amounts of PI fuel. Note: the timing is retarded as PreDI timing is retarded. Also, THC emissions reach a minimum value around 430 CAD bfTDC. Summary • Pre-DI timing can control: 1. Timing of HCCI combustion 2. Emissions produced from HCCI combustion • Varying the pre-DI % of total fuel injection can also be used to influence the timing of HCCI combustion and emissions output. • Different trends in combustion efficiency were found using Port Injection vs. Direct Injection. Valve Timings and Details Operating range obtained with current valve timings for both Port Injection and Direct Injection with PreDI. This map was obtained with fixed valve timing, fixed injection timing, fixed PreDI duration and the load varied by reducing the PI or DI duration. Combustion Efficiency Future Work • Improving HCCI combustion by: • Varying PreDI timing with shorter injection durations • Increasing coolant temperature to help expand lower load limit • Using different fuels with PreDI injection • Varying PreDI timings and durations with lower amounts of trapped exhaust gas residuals Port Injection vs. Direct injection Combustion Efficiency. Note the different trends from PI to DI.