The Optimization And Improvement Of Combustion Chamber For Large Natural Gas Engine

Since the21st century, due to the deterioration of the global environment, lookingfor a clean and environmentally friendly alternative fuel has become the focus of thecontemporary combustion engine industry research. Because natural gas is a clean andenvironmentally fuel, natural gas engines get widespread attention. Compared totraditional fuel engines, natural gas engines’ emission performance is superior, but itscombustion is slower, later combustion phenomenon is more serious, exhausttemperature is higher. Lean-burn technology is an effective measure to reduce thetemperature of the exhaust gas, but the in-cylinder combustion speed of the in-cylindercombustion becomes more slowly, and even leads to flameout.In this paper, through natural gas engine combustion chamber componentsimprovement to accelerate flow rate of lean-burn cylinder, increase the turbulent kineticenergy, and then accelerates the burning speed, reduces combustion duration, in order toachieve rapid combustion and reduce exhaust temperature purposes simultaneously.Using KIVA program establishes numerical simulation model of the natural gasengine combustion chamber. At first, changing the shape of the combustion chamber toaccelerate the rate of gas flow and increase the turbulence intensity, thus to improvecombustion of the engine and reduce the exhaust temperature. The improvement of thecylinder gas flow is too small that we propose the secondary improvement programbased on the combustion chamber eccentric. At last, considering gas flow rate, theturbulence intensity and the flow of uniformity, we select offset0.3cm cuff bowl-shapedchamber in the X direction as the optimal solution.The paper has carried on the bench test to the improved gas engines, collectingrelevant test dates and comparing with the original piston engine. The test results showthat: once the natural gas engines use new combustion chamber, the exhaust gastemperature has been effectively reduced, gas economy improved, gas consumptionreduced by11.4%compared to the original combustion chamber engines.At700KW operating point, the excess air ratio is1.78, higher than the engineswhich use original combustion chamber, the performance of engine lean-burn has beenimproved. The gas consumption has been reduced by8.5%, improved the economicperformance of the engine effectively. Compared with the original combustion chamberengine, the maximum cylinder pressure increases0.845MPa, maximum cylinderpressure points advances2degrees, the development of flame reduces six degrees and rapid combustion period reduces six degrees.