연료분무 및 연소 1 : 바이오디젤 저온연소에서 질소화합물과 매연 동시저감을 위한 최적 흡기압과 흡기산소농도 = Fuel Injection and Combustion 1 : Optimal Intake Pressure and Oxygen Concentration with Biodiesel Low Temperature Combustion for Simultaneous NOx and smoke reduction

다국어 초록 (Multilingual Abstract)

One effective way to simultaneously reduce NOx and smoke emissions in a diesel compression-ignition engine is to operate the engine in low temperature combustion (LTC) regimes. Two strategies are commonly used to realize the LTC operation, dilution-controlled LTC and late-injection LTC. The present study applied the former approach. In the dilution controlled regime, LTC is achieved by supplying a substantial amount of EGR to the cylinder. The significant EGR gas increases the heat capacity of in-cylinder charge mixture while decreasing oxygen concentration of the charge, activating low temperature oxidation reaction and lowering NOx and smoke emissions. However, the use of high EGR levels deteriorates combustion efficiency and engine power output. Therefore, it is widely considered to use increased intake pressure as a way to resolve this issue. Effects of intake pressure and oxygen concentration levels were investigated with a single-cylinder engine. Biodiesel (BD100) required intake oxygen concentration reduction to 13% to achieve simultaneous reduction of smoke and NOx, while Diesel required oxygen reduction to 8%, as in Figure 1. When intake pressure increased, combustion efficiency was improved so that THC and CO emissions were decreased. A shift of the peak smoke location was also observed to lower O2 concentration while NOx levels were kept nearly zero. In addition, an elevation of intake pressure enhanced engine power output as well as indicated thermal efficiency in LTC regimes. All these results suggested that LTC operation range can be extended and emissions can be further reduced by adjusting intake pressure.