Research on in-cylinder steam injection in a turbocompound diesel engine for fuel savings

Abstract

Turbocompounding and in-cylinder steam injection (ICSI) are both effective methods for engine waste heat utilization. The fuel savings potential obtained by the combination of the two methods is not clear. In the paper, the effects of ICSI on the performance of a turbocompound engine are investigated. Firstly, the layout of the turbocompound engine with ICSI is described. Then, the simulation model of a turbocompound diesel engine is developed and calibrated. Finally, the influences of different ICSI parameters on the performance of the turbocompound engine are studied. The results show that the gross power and fuel economy of the turbocompound engine are remarkably improved by ICSI. With optimal steam injection mass, the brake specific fuel consumption of the turbocompound engine is reduced by 3.0%–5.4% under different engine speed conditions. The performances of turbocharged turbine and power turbine are both improved. In-cylinder combustion process is improved and overall in-cylinder pressure profile is enhanced. Steam injection mass and timing have great impacts on the performance of the turbocompound engine. As steam injection mass increases, the engine fuel economy is further improved. The earlier the steam is injected, the better the engine performance will be obtained.