Reactivity-Controlled Compression Ignition Combustion Using Alcohols

Abstract

Rapidly increasing fossil fuel consumption along with increasing fuel cost and serious concerns about carbon dioxide (CO2) emission reduction from the transportation sector motivated the automotive researchers to explore new internal combustion (IC) engine technologies, which can deliver higher engine efficiency with a lower impact on the environment and human health. These issues can be resolved by using advanced combustion strategies, which are also capable of utilizing alternative fuels. In last few years, reactivity-controlled compression ignition (RCCI) combustion has attracted significant attention due to its capability of ultra-low oxides of nitrogen (NOx) and particulate emissions without any soot-NOx trade-off and superior engine efficiency compared to compression ignition (CI) and spark ignition (SI) combustion. RCCI combustion is a combination of dual-fuel and partially premixed combustion (PPC) techniques, in which a low-reactivity fuel such as gasoline, compressed natural gas (CNG), alcohols are injected into the intake port and a high-reactivity fuel such as mineral diesel, biodiesel is directly injected into the combustion chamber. Blending of these two fuels in the combustion chamber controls the heat release rate (HRR) and combustion phasing. Premixed ratio and spatial stratification between these two fuels control the combustion phasing and combustion duration. RCCI combustion and emission characteristics are also dependent on fuel injection strategies such as fuel injection pressure (FIP), number of injections, start of injection (SOI) timings, exhaust gas recirculation (EGR) rate, and intake charge temperature. This chapter reviews all these factors and presents important features of RCCI combustion for application in future automotive engines. A separate section for use of alcohols in RCCI combustion is also included in this chapter, which shows various pathways for alternative fuel utilization in this advanced combustion technique. Roadmap for future research directions for RCCI combustion is also discussed in this chapter.