The Research Of Combustion Process On A Compression Ignition CNG Engine

With the decreasing of petroleum resource, it became an urgent affair to look for alternative fuel now. The natural gas has attracted a lot attention due to its advantage in cost and emission. Developing natural gas engine is one of effective means to solve the traditional energy crisis.This paper presents a newly designed compression ignition divided chamber combustion system of the natural gas engine. The study has been done using a prototype test engine modified from the S195 single cylinder engine. The modification includes the designing of chambers, computer-controlled system and natural gas supply system. The combustion chamber consists of the main combustion chamber on the top of the piston, the auxiliary combustion chamber in the cylinder head and the passage between the main and auxiliary chambers. The oxide-coated zirconium of the chambers at the piston and cylinder head, the design of air gap on the auxiliary chamber are applied to lower heat rejection. The electrical ceramic glow plug is inserted in the auxiliary chamber to assist ignition. The EGR system has been installed to find the effect of EGR on natural gas engine.The compression ignition and combustion of the newly designed combustion system of the natural gas engine have been investigated. The effect of the natural gas supply method, passage diameter and heated temperature of intake air on the ignition, combustion and emission are studied. The results show that low pressure natural gas supply can easily realize the premixed charge compression ignition of the natural gas engine on condition of heating the intake air and increasing the temperature of the electrical glow plug. Moderately increasing the passage diameter between the main and auxiliary chambers is beneficial to the smooth start of the engine. EGR system is helpful for decreasing HC and NOx emission and stabilizing the combustion process of the engine.It carries out a new combustion system on natural gas engine. Meanwhile a new method to reduce emission and boost economy of natural gas engines is proposed in this paper.