Experimental Study On High Pressure Injection And Premixed Combustion Of Methane Under Variable Turbulence

With the rapid development of automobile industry,the problems of emission pollution and oil shortage are becoming more and more serious.Gas fuel has broad application prospects in dealing with emission pollution and oil shortage.For the in-cylinder direct injection natural gas engine,the jet characteristics of natural gas under high pressure injection and the turbulent combustion characteristics in the cylinder directly affect the power,economy and emissions of the engine.Therefore,the experimental study on the characteristics of methane high pressure jet and methane-air premixed turbulent combustion in turbulent environment is carried out to provide experimental data for the optimization of gas-fueled engines.Based on the principle of turbulence generation,a new type of turbulence generation system is designed in this paper.A continuous and controllable isotropic turbulence environment is created in a constant volume combustion bomb by the method of intake jet combined with jet collision.According to the conservation equation,turbulence model,volume bomb and the working principle of turbulence building system,the numerical simulation model of turbulent constant volume combustion bomb is established by using Fluent software.The internal flow of turbulent constant volume combustion bomb is numerically simulated.The feasibility of the design scheme of turbulent constant volume combustion bomb is verified by analyzing the internal flow field of turbulent constant volume combustion bomb.In this paper,the function of the turbulent combustion test platform is analyzed,and the overall design of the turbulent combustion test platform is completed.The structure and working principle of each subsystem of the test platform have been designed.The key parameters of each subsystem have been calculated and theoretically demonstrated.The turbulence measurement system in the constant volume combustion bomb has been developed.The turbulence intensity in the center of the capacitance bomb has been measured and calibrated by the system.The turbulence intensity measurement results have been analyzed and the uniform symmetry and controllability of turbulent environment in a constant volume combustion bomb are demonstrated.Based on the developed test platform,the experimental study on the characteristics of high pressure methane jet was carried out.An image processing program for jet development photographs taken by high-speed photography was developed.The effects of injection pressure,turbulence intensity and ambient back pressure on the characteristics of high pressure methane jet were studied.The experimental results show that turbulence promotes the radial development of high pressure methane jet,while the axial development is mainly reflected in the main stage of the jet.Turbulence enhances the entrainment of the jet to the surrounding medium gas,which is conducive to the mixing of methane jet and medium gas.The experimental study of methane-air premixed turbulent combustion was carried out,and the characteristic parameters of premixed turbulent combustion were analyzed.The effects of turbulence intensity and equivalence ratio on flame propagation characteristics and combustion process of methane-air premixed turbulent combustion were studied.The results show that for methane-air premixed turbulent combustion,turbulence can accelerate flame propagation,increase combustion heat release rate and shorten combustion duration.