Study On Characteristics Of Exhaust Gas Cooling Using Ejection Combined With Atomization

The popularity of infrared guided weapons and the increasing resolution of optoelectronic imaging satellites pose a significant threat to the safety of military vehicles.Reducing the infrared characteristics of engine exhaust is critical to vehicle safety.The ejector with the residual pressure head of the exhaust gas is simple in structure and has a good cooling effect.The spray has a large amount of phase change potential to achieve a second cooling.Therefore,the cooling method of ejector in combination with spray cooling is proposed to control infrared radiation of military equipment.Based on CFD method,a numerical method for ejector mixing is established.The mixing process of high temperature exhaust gas to the outside cold air is simulated,the temperature and the pressure field,and the development of the boundary layer inside the ejector,the temperature distribution at the outlet are obtained.The gas-liquid two-phase flow is simulated by the DPM method.Species transport model is applied to simulate the mixing process.The physical properties of each parameter under the simulated conditions are determined by reference.Experiments are carried out to verify the correctness of the ejector model by comparing the simulated data with the experimental data under the same condition.The effects of inlet diameter Din and throat diameterDth on the entrainment ratio ?,pressure ratio ?,jet core length l,outlet average temperature T,outlet average pressure p,and uniformity index ?m are investigated under different operating conditions.Limited throat diameter impedes the development of the jet boundary layer,resulting in limited flow of the entrained airflow.The increase in the diameter of the inlet diameter can enlarge the ej ector area,which is favorable for inj ection more ambient cold air.However,this process may cause adversepressure at the outlet,causing gas backflow.The effects of the operating conditions on the ejector performance are investigated.The operating conditions include exhaust gas injection pressure and spray characteristics.An increase in the injection pressure can expand the length of the jet core region.The spray can improve the performance of ejector in many aspects.The latent heat of phase change carried by the spray can reduce the temperature of the exhaust gas while improving the distribution of the outlet pressure.Another function of the spray is to aid in the sedimentation of carbon particles in the exhaust.Based on the simulation results,a set of ejector atomization system that can reduce the infrared radiation of exhaust gas is processed.After infrared suppression by the ejector atomizer,the temperature of the exhaust gas is reduced from 205.1 ? to 90.5?,the temperature is lowered by 114.6?,and the infrared radiation energy is reduced by 64%.