Effect of fuel inlet temperature on cottonseed oil–diesel mixture composition and performance in a DI diesel engine

Vegetable oils are receiving a lot of attraction as alternative engine fuels as they are renewable. The main problems with the use of neat vegetable oils in direct injection (DI) diesel engines are higher viscosity and relatively lower thermal efficiency as compared to diesel fuel. In this investigation the cotton seed oil (CSO) has been considered as an alternative fuel for the compression ignition (C.I.) engine. The viscosity of this oil is decreased by blending with diesel and preheating the CSO–diesel blends to reduce the viscosity further. The mixture of varying proportions of cotton seed oil and diesel were prepared and their viscosities at various inlet temperatures were calculated and the performance and emission levels of these mixtures are compared with diesel fuel. The performance of the engine using preheated blends and cottonseed oil were studied using a single cylinder diesel engine. Significant improvement in engine performance is observed with preheated CSO and diesel mixture compared to neat CSO. Test results show that there is a marginal increase in the brake thermal efficiency of the engine, as the fuel inlet temperature of the blend and the amount of diesel in the blend increases. It is increases from 28% to the maximum of 30.5% with preheated CSO and diesel mixture of 40%. The smoke, carbon monoxide (CO) and unburnt hydrocarbons (HC) emissions of the engine is also less with the preheated blends. Smoke emission reduces from 3.9 Bosch smoke unit (BSU) to 3.5 Bosch smoke unit (BSU) which is very close to diesel smoke value of 3.4 BSU. Heat release rates indicated an increase in combustion rate with preheated mixtures. The cylinder peak pressure increases from 70.4 bar to 72.5 bar for optimum preheated mixture (60% CSO and 40% diesel at 343 K). From the engine test results it has been established that 60% of cotton seed oil at 343 K can be substituted for diesel.