An experimental study on mode switching between conventional diesel and reactivity controlled compression ignition combustion modes in a light duty automotive diesel engine

Abstract

Reactivity Controlled Compression Ignition (RCCI) is a low-temperature combustion (LTC) concept in which two fuels of different Cetane numbers are mixed through an in-cylinder blending technique for better charge preparation to control the combustion phasing and combustion duration to attain higher efficiency, CO2 reduction and lower emissions. RCCI is a superior LTC strategy and provides better control over combustion through reactivity stratification, equivalence ratio stratification, and temperature stratifications over other LTC strategies. However high unburnt emissions at low loads and higher rate of pressure rise at high loads mandates mode switching from conventional diesel combustion (CDC) mode to RCCI mode and vice versa in those operating conditions. Smooth mode transition is essential for effective implementation of the RCCI strategy at the vehicle level. Only few studies were reported in the literature on RCCI mode shifting which motivated to perform this research. RCCI with all possible dual fuel combinations have been reported by several authors concluding high efficiency, ultra-low NOx, and Soot emissions. Even studies on controlling unburnt emissions, improving combustion efficiency at low loads, and extending the operating range at high loads were observed from the literature. Whereas, experimental studies exploring mode switching and methods of developing control algorithm are not reported in the literature. Hence, to explore the mode switching and to develop a control algorithm for smooth mode transition this experimental study was performed. With this intent, the mode switching between CDC and RCCI combustion modes at different torque and speeds of the test engine was investigated. newline newline