Performance Evaluation of a Dual Fuel Engine (Diesel + LPG)

The paper presents the results on the existing diesel engines that can be suitably modified to operate on the dual fuel mode to conserve diesel and also reduce environmental pollution. The conventional fuels, petrol and diesel for internal combustion engines are getting exhausted at an alarming rate, due to tremendous increase in the vehicular population. Further these fuels cause serious environmental problems as they release toxic gases into the atmosphere at high temperatures and concentrations. Some of the pollutants released by the engines are UBHC, CO, NOx, smoke and particulate matter. In view of this and many other related issues, these fuels will have to be replaced by alternative and eco-friendly fuels. A 4-stroke, single-cylinder diesel engine has been considered for the purpose of experimentation. It is modified suitably to run on the dual fuel mode. LPG carburetor is incorporated on the intake side of the engine. The fuel injection system is also altered so that it injects only the pilot fuel. The engine is interfaced with a computer, so that the data could be generated on-line and stored for the off-line analysis. The performance of the engine is evaluated at a constant speed of 1500 rpm under varying load conditions for different proportions of LPG energy. The LPG energy substitution could be done up to 50% at lower loads and up to 20% at higher loads. The engine performance is better on pure diesel up to engine loads of about 35%. At higher engine loads, the dual fuel mode is superior to the pure diesel mode of operation. This is true with regard to the emissions also. The smoke density is considerably reduced on dual-fuel operation, compared to that of pure diesel operation. At lower loads, for improved performance, the engine could be operated on pure diesel operation. However for higher loads, the operation could be switched over to the dual fuel mode. The threshold load of transition from diesel fuel mode to the dual fuel mode is found to be about 35%. Dual fuel engines can be conveniently used in various applications, particularly at higher loads.