The Study Of Combustion Process In Spark-ignition Methanol Engine Using Rapid Compression-expansion Machine

Spark-ignition methanol engine with high compression ratio is one of the technology which can use the pure methanol high-efficiently and cleanly as the alternative fuel in the engines. The combustion process of a SI(Spark-ignition) methanol engine is simulated and measured using a RCEM(Rapid CompressionExpansion Machine) in order to finding the way to optimize the combustion process and achieve knocking suppression. Some factors, such as fuel concentration, ignition timing, drive hydraulic pressure, the combustion chamber shape and the number of the spark plugs are researched and analyzed, mainly on how they affect the combustion process and knocking tendency of the methanol engine.Firstly, the SI methanol engine simulating experimental platform is set up using the self-designed RCEM. The control and data acquisition system and an universal ECU calibration system using CCP/XCP protocol has been developed. then, the influence on the combustion process and knocking tendency of the fuel concentration, ignition timing, drive hydraulic pressure, the combustion chamber shape and the number of the spark plugs are researched on the SI methanol engine simulating experimental platform, the result shows the optimum ignition time delayed when the mixture concentration is thicker and the combustion rate is also faster, the thin mixture concentration can achieve the highest efficiency. With the improvement of compression ratio, the indicated efficiency increases, but the higher compression ratio also increases the knocking tendency. The different combustion chamber shape has a great influence on the combustion rate and efficiency. The using of double/dual spark plugs can increase the combustion rate and the indicated efficiency, it also has a great suppression influence on knocking. In conclusion of all the result of the factors, this project put forward a plan using the optimized combustion chamber shape and higher compression ratio, the optimum ignition timing and thinner mixture concentration with dual spark plugs which can achieve the higher efficiency without knocking.The conclusion of this study provides several effective technical ways to achieve an efficient combustion in spark-ignition methanol engine with high compression ratio, and also provides several solutions of knocking suppression on high compression ratio condition, meanwhile it also makes progress of the technology to use methanol fuel efficiently in the free piston engines.