Single Cylinder Diesel Engine Startup Experiments with Fast Cycle Resolved In-cylinder and Exhaust Sampling 2009-01-1973
Single cylinder diesel engine cycle resolved startup experiments were performed at two different Compression Ratios. At CR18 (CR = 18) conventional engine starting resulted in a broad range of acceptable startup equivalence ratios (φ). However, reducing the CR to 16 resulted in problematic engine starting regardless of fuel level. In an effect to produce robust engine starting at lower CRs the engine was motored first. This allowed for strong starting performance coupled with high load fueling levels. For both CRs, IMEPg and exhaust CO2% increased as fueling level increased. However, while in-cylinder CO2% exceeded exhaust CO2% for moderate φ, this trend was reversed as fueling was reduced. Exhaust CO% was minimal except for stoichiometric fueling at CR18. Peak NOx production occurred at CR18 and φ = 0.55. Exhaust UHCs were maximized for higher fueling cases but dropped quickly after start. Similarly, ignition delay increased with φ but decreased during warm-up. As a result, burn duration was shortest with higher fueling and tended to decrease a few seconds after start. In-cylinder UHC started high (5000 - 15000 ppm) but decreased steadily during warm-up and dropped by one or two orders of magnitude during the exhaust phase. Finally, soot emissions were relatively independent of CR and increased with fueling level.