Homogeneous Charge Compression Ignition (HCCI) Engines: A Review
The homogeneous charge compression ignition (HCCI) combustion is considered to be the principally promising future IC engine concepts. HCCI is a concept of hybrid combustion, between the Otto engine and Diesel engine. HCCI is however not a modern finding. Already in the early twentieth century hot bulb engines operated with an HCCI like combustion. They were superior in terms of brake efficiency compared with the contemporary gasoline engines and at the same level as the diesel engines. High engine efficiencies and ultra low NO emissions and low particulates are the benefits of HCCI engines. Volumetric auto ignited combustion of the compressed lean air fuel mixture is attributed to these benefits. There are few drawbacks also were there in HCCI engines like, low specific output, narrow operating range, lack control over the ignition process, long start up time and high emissions like CO and UHC emissions. The CO and UHC emissions can be after treated using catalytic converters. In this study a literature review on HCCI engine has been performed and the parameters affecting the HCCI combustion phasing, performance and emissions were discussed. Strategies to widen the peak load bearing capacity of HCCI engine, reducing the emissions like NOx, CO and UHC, easy auto ignition were discussed in the present study.