A Simulation Study On The Performance Of A Mono Fuel CNG Engine Refitted By The 6135Z Diesel Engine

With the rapid development of automobile industry, environment pollution and global shortage of oil resources is increasingly serious, which must be a challenge to the traditional oil fuel and combustion form of automobile engines. The natural gas becomes an alternative fuel with great potential for development, for its low emission, cheap price and abundant resource. At present, the domestic natural gas engines are mostly refitted by gasoline engines and diesel engines. The main problem of the modified engines is a decrease of engine power.In order to study the reasons of engine power decreasing and how to restore engine power, this paper takes an example for 6135Z diesel engine, and the research is made on 6135Z natural gas engine originated from it. The main research work includes:(1) The whole 6135Z diesel engine model is built up with GT-POWER, and the performance of the 6135Z dies engine is simulated. The result of the simulation is basically consistent with the experimental result, which proves the correctness of the engine model.(2) A natural gas engine model is built on the basis of the diesel engine model, and analyze is made on how the natural gas engine performance is impacted when the way of pressure charging varies. The external characteristic of the natural gas engine is simulated with the model. The reasons of engine power decreasing are indicated by comparing the external characteristic of the natural gas engine and the one of the diesel engine.(3) In order to improve the natural gas engine power, pressure ratio of the compressor is increased, and air-fuel ratio, compression ratio, ignition advance angle and valve timing are optimized. Relevant improvement views are made by analyzing their influence on the natural gas engine power.According to the simulation result, when improving pressure ratio of the compressor, appropriate air-fuel ratio, compression ratio, ignition advance angle and valve timing can restore the natural gas engine power to 99.4% of the diesel engine power.