Vegetable oils are a promising alternative among the different diesel fuel alternatives. However, the high viscosity, poor volatility and cold flow characteristics of vegetable oils can cause some problems such as injector coking, severe engine deposits, filter gumming, piston ring sticking and thickening of lubrication oil from long-term use in diesel engines. These problems can be eliminated or minimized by transesterification of the vegetable oils to form monoesters. These monoesters are known as biodiesel. The important advantages of biodiesel are lower exhaust gas emissions and its biodegradability and renewability compared with petroleum-based diesel fuel. Although the transesterification improves the fuel properties of vegetable oil, the viscosity and volatility of biodiesel are still worse than that of petroleum diesel fuel. The energy of the biodiesel can be released more efficiently with the concept of low heat rejection (LHR) engine. The aim of this study is to apply LHR engine for improving engine performance when biodiesel is used as an alternative fuel. For this purpose, a turbocharged direct injection (DI) diesel engine was converted to a LHR engine and the effects of biodiesel (produced from sunflower oil) usage in the LHR engine on its performance characteristics have been investigated experimentally. The results showed that specific fuel consumption and the brake thermal efficiency were improved and exhaust gas temperature before the turbine inlet was increased for both fuels in the LHR engine. r

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In this study, the effect of thermal-barrier-coated piston top and combustion chamber surfaces on turbocharged diesel engine performance was experimentally investigated. Satisfactory performance was obtained with TBC 1 (with coated cylinder head and valves) and TBC 2 (with coated cylinder head, piston top, and valves). Compared with a standard diesel engine, engine power was increased by 2 per cent, the engine torque was increased by 1.5-2.5 per cent, and brake specific fuel consumption (b.s.f.c.) was decreased by 4.5-9 per cent. The NO x emissions were increased by 10 per cent in diesel engines with TBC coatings compared with a standard diesel engine. Experimental studies have shown that there is a reduction in smoke emissions of up to 18 per cent as a result of TBC application.

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