Combustion characteristics of a common rail direct injection engine using different fuel injection strategies.

Abstract Fuel injection parameters such as fuel injection pressure (FIP) and start of injection (SOI) timing significantly affect combustion, performance, emission and durability of a common rail direct injection (CRDI) diesel engine. In this study, a state-of-the-art single cylinder research engine was used to investigate the effects of FIP and SOI timings on engine combustion characteristics, which affects heat transfer and soot formation as well. The experimental setup consisted of an instrumented single cylinder engine with provision to vary the fuel injection parameters along with online high speed combustion data acquisition and analysis system. Experiments were conducted at constant engine speed (1500 rpm) at four different FIPs (300, 500, 750 and 1000 bar), four different SOI timings and different fuel injection quantities. Combustion characteristics of the engine were analyzed using exhaustive heat release analysis based on in-cylinder pressure data. In direct injection compression ignition (DICI) engines, fuel vaporization and heat transfer characteristics affect fuel-air mixing, which is also influenced by the FIP and SOI timings. These injection parameters significantly control the rate of pressure rise (ROPR), and heat release rate (HRR), which in-turn affect the heat transfer from the engine cylinder as well as the engine power output. Therefore, it is necessary to optimize the fuel injection parameters to develop efficient and clean combustion diesel engines. Highlights • Heat transfer from cylinder walls affects combustion characteristics. • Combustion characteristics are highly dependent on SOI timings & FIP. • Increase in FIP led to higher peak cylinder pressure at all SOI timings. • At higher FIP, lower radiative heat losses from soot were observed. • IMEP increased with increasing FIP up to 500 bar and then decreased at 1000 bar. [ABSTRACT FROM AUTHOR]