Dual-Fuelling of a Direct-Injection Automotive Diesel Engine by Diesel-Gas Method

Use of liquefied petroleum gas (LPG) in compression-ignition (C-I) engines has always been considered important in the diesel engineering field. This is due to its easy accessibility and good combustion characteristics. In this paper the application of LPG fuel along with diesel oil in a direct- injection automotive diesel engine is experimentally investigated. In order to convert the pure diesel engine into a diesel-gas one, a carbureted LPG fuel system has been designed and fitted into the engine. Then by means of a system of rods, the LPG system is linked to the diesel fuel injection system. The dual- fuel system is adjusted so that, at full load conditions, the quantity of diesel oil is reduced to 70%, and 30% of its equivalent energy is substituted by LPG fuel. Performance tests conducted under various loads and speeds on both diesel and diesel-gas engines, show that with equal power the diesel-gas engine has the potential to improve overall engine performance. For example, within useful speed range, its fuel economy increases by 2-5% and the amount of smoke and mean exhaust gas temperature are reduced by 25-48% and 3.5 -7.2% respectively. Also various proportions of LPG and diesel oil are investigated. It is found that the ratio of 30% LPG/70% diesel oil is the most suitable one. The experimental results verify the predicted results, obtained from a diesel-gas engine cycle model.