Investigation on Premixed Charge Compression Ignition combustion control using multi pulse ultrahigh pressure injection 2019-01-1155
Compression ignition (CI) engines provide higher thermal efficiency compared to other internal combustion engines although large amounts of NOx and soot are produced during combustion. NOx and soot emissions can be reduced by using Premixed Charge Compression Ignition (PCCI). However, the problems of PCCI combustion limited operating range, unstable start of combustion and also increase of combustion noise. This multi-pulse ultrahigh pressure injection allows fuel to be injected near TDC, improve mixture formation and enhance possibility to extend operating range of PCCI combustion. The objective of this paper is to control and extend operating range of PCCI combustion using multi-pulse ultrahigh pressure injection that has not been studied before. Combustion characteristics were investigated using rate of heat release analysis, heat balance analysis, exhaust emission measurement and soot concentration measurement. The experiments were carried out on a single cylinder engine at 0.7MPa IMEP and 2,000 rpm. The injection pressures were varied at 200, 250, 300 and 350MPa to investigate effect of injection pressure and shortened fuel injection timing. The injection pulses were varied at 2 pilot injections following by 2, 3 and 4 pulses of the main injection. The main injection timing were varied from -14 to 4.5 ATDC to compensate combustion duration prolonged from multi-pulse injection. The results showed that increasing injection pressure combines with injection pulse increased thermal efficiency and simultaneously decreased NOx and smoke. In case of 2 pulses main injection, the heat release rate at 1st pulse is PCCI. For 3 and 4 pulses main injection, 1st, 2nd pulse are PCCI following by diffusive combustion due to lack of oxygen concentration.
Pop-Paul Ewphun, Tsuyoshi Nagasawa, Hidenori Kosaka, Susumu Sato