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The present work investigates the emission and thermal performance of DI CI variable compression ratio engine using blends of biodiesel and standard diesel as a fuel at compression ratios of 15,16,17 and 18. The biodiesel derived from non edible Calophyllum Inophyllum linn oil is used on the engine. The blends of biodiesel and diesel used were B20, B40, B60, B80 and 100% biodiesel. At 18 CR the brake thermal efficiency of the engine operated with 100% biodiesel is 8.9% less than Diesel and the brake specific fuel consumption for biodiesel found to be more than that of diesel. There is major reduction in Carbon monoxide and Hydrocarbon emissions with 100% biodiesel as a fuel compared to diesel at compression ratio of 18.

This paper presents the effect of static fuel injection timings and blends of biodiesel with conventional diesel on the performance and emission characteristics of a DI-CI VCR engine. Blends of Honne oil methyl ester (HnOME) and diesel was used as fuel. The default value of static injection timing of the engine was 23 bTDC (before top dead centre). Injection timing was retarded and advanced from default value by 4 bTDC. Experiments were conducted at three levels of timings using the blends B20, B40, B60, B80 and B100 (pure HnOME). Conventional diesel was used as a reference fuel. The decrease in brake thermal efficiency for B20, B40, B60, B80 and HnOME compared to diesel at 19 bTDC were 5.4, 15.7, 13, 10 and 2.9% respectively. Brake thermal efficiency decreased by 4.2, 15.7, 13.5, 10.15 and 2.96% for B20, B40, B60, B80 and HnOME respectively compared to diesel at 27 bTDC. Nitric oxide emissions reduced for both advanced and retarded timings, but the reduction was more for retarded timing. Smoke intensity increased for retarded timing. Blend B60 to B80 can be successfully used by retarded timing combined with higher compression ratio and fuel injection pressure. KEYWORDSHonne oil methyl ester; fuel injection timing; thermal performance; emission characteristics; brake specific energy consumption Acronyms HnOME Honne oil methyl ester CI Compression Ignition DI Direct injection VCR Variable compression ratio B80 80% HnOME and 20% mineral diesel by volume BTE Brake thermal efficiency BSFC Brake specific fuel consumption EGT Exhaust gas temperature BSEC Brake specific energy consumption HC Unburned hydrocarbon CO Carbon monoxide CO 2 Carbon dioxide NO X Oxides of nitrogen HSU Hartridge smoke unit