h i g h l i g h t sCAI combustion is achieved in a 2-stroke poppet valve GDI engine. Gasoline and its mixture with ethanol are used as the fuel on the engine. The effect of ethanol content on operating range, combustion and emissions are analysed. a b s t r a c t Controlled Auto Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), is one of the most promising combustion technologies to reduce the fuel consumpt ion and NOx emissions . Currently, CAI combustion is constrained at part load operation conditions becau se of misfire at low load and knocking combustion at high load, and the lack of effective means to control the combustion process. Extending its ope rating range including high load boundary towards full load and low load boun dary towards idle in order to allow the CAI engine to meet the demand of whole vehicle driving cycles, has become one of the key issues facing the industrialisation of CAI/HCCI technology. Furthermore, this combustion mode should be compatible to different fuels, and can switch back to conventional spark ignition operation when necessary. In this paper, the CAI operation is demonstrated on a 2-stroke gasoline direct injection (GDI) engine equipped with a poppet valve train. The results shown that the CAI combustion can be readily achieved in the 2-stroke cycle of a poppet valve engine and the range of CAI combustion can be significantly extended compared to the 4-stroke cycle operation . In addition, the effect s of ethanol concentration on 2-stroke CAI operational range, combustion proce ss, emissions and efficiencies are studied and presented.
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