Experimental Study on the Effects of Injector Nozzle and Piston Bowl Geometry on Combustion and Performance in Medium-Speed Diesel Engines

In recent years, many regulations of exhaust gas emissions have been enhanced in not only automotive engines but also marine and power generation engines. So we have done the various studies to reduce NOx in a medium speed diesel engine, HYUNDAI HiMSEN, for satisfying the next IMO(International Maritime Organization) regulation (Tier2, 20∼30% reduction for current limit). The selected parameters for in this study are fuel injector nozzle and piston bowl geometry. These have significant effect on engine performance and combustion. In this study, engine performance experiments have been carried out to investigate the effects of fuel injector nozzle geometry including the nozzle hole diameter, hole number, hole length, and injection angle on the fuel oil consumption and NOx emission of HYUNDAI HiMSEN engine. Also experiments have been carried out to evaluate engine performance and combustion with changing piston bowl geometry including the diameter and depth of piston bowl. The measured parameters of engine performance include cylinder pressure, fuel pump pressure, injection pressure, and heat release rate and NOx, etc. We could find out the optimum point of the nozzle geometry and the piston bowl shape regarding to the trade-off curve on fuel oil consumption versus NOx emission to minimize fuel oil consumption and to satisfy NOx regulation of HYUNDAI HiMSEN engines.