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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The aim of this experimental study was to investigate the effect of addition of methanol and ethanol (5% - 10% and 15%) as a fuel at low rates to gasoline fuel against performance, and emissions characteristics. The experiments were car-ried out in a single cylinder, four-stroke, air-cooled spark plug ignition engine at various engine loads (2 - 2.5 - 3 - 3.5 and 4 Nm) and constant engine speed (2500 rpm). Performance, and emission characteristics of gasoline, methanol-gasoline and ethanol-gasoline blends were evaluated. When the results are examined, with the addition of ethanol and methanol, the specific fuel consumption and specific energy consumption increased, while the brake thermal efficiency decreased. Apart from that, CO and HC emissions have improved. The lowest CO and HC emissions were obtained in G85M15 and G85E15 fuels, respectively. Compared to gasoline, a reduction in CO and HC emissions of over 50% was observed.

This study aimed to investigate the effects on performance, emission, and combustion characteristics of adding biodiesel and bioethanol to diesel fuel. Diesel fuel and blend fuels were tested in a water-cooled compression ignition engine with direct injection. Test results showed that brake specific fuel consumption and volumetric efficiency increased by about 30.6% and 3.7%, respectively, with the addition of bioethanol to binary blend fuels. The results of the blend fuel's combustion analysis were similar to the diesel fuel's results. Bioethanol increased maximal in-cylinder pressure compared to biodiesel and diesel fuel at both 1400 rpm and 2800 rpm. Emissions of CO increased by an amount of about 80% for fuels containing a high level of bioethanol when compared to CO emissions for diesel fuel. Using biodiesel, NO emissions increased by an average of 31.3%, HC emissions decreased by an average of 39.25%, and smoke opacity decreased by an average of 6.5% when compared with diesel fuel. In addition, when using bioethanol, NO emissions and smoke opacity decreased by 55% and 17% on average, respectively, and HC emissions increased by an average of 53% compared with diesel fuel.