Reactivity Controlled Compression Ignition (RCCI) of Gasoline- CNG Mixtures

Abstract

Reactivity controlled compression ignition (RCCI) is a dual fuel combustion method that relies on the significant difference in reactivity of the fuels involved. RCCI had a low performance at high engine speed due to its high tendency on knocking and high pressure rise rate. Therefore, this study investigates the effect of the fuel stratification on the RCCI combustion and its extended to the interaction of two low reactive fuels, gasoline and compressed natural gas (CNG), in the RCCI combustion system. The investigation was experimentally performed on a single cylinder engine and constant volume chamber. The stratification was created by varying injection timing in the engine by injecting CNG at 80 and 120 before top dead center (BTDC) and varying injection gap in the constant volume chamber with the gaps between two fuel injection timing were varied between 0 ms to 20 ms. The results in the engine experiment show that proportions of gasoline and CNG and degree of stratification of CNG were found to be effective means of combustion control within certain limits of engine load and HC and CO emissions could be significantly reduced. While in constant volume chamber it has a significant effect on the combustion phasing. Stratified mixture produces shorter combustion duration while homogeneous mixture produces longer duration.

A review of technical solutions for RCCI engines

“…It translates into higher thermal efficiency of engines with this type of ignition. However, in order to achieve ignition in the combustion chamber of the engine, very specific conditions are required, which are difficult to achieve [5]. Effective control of the moment at which ignition takes place in all areas of the engine operation is currently beyond the possibilities of designers.…”