Optimization Of Combustion Chamber And Fuel Injection Timing For Diesel Rotary Engine

Since its birth,rotary engine has been widely used in military and civil fields because of its advantages of simple structure,high work weight ratio,low cost of maintenance and so on.In order to optimize the performance of the rotor engine,this paper takes the diesel engine as the research object,and uses the method of experiment and numerical simulation to combine the optimization of the flow field distribution with the improvement of the spray characteristics,and puts forward a new type of double concave combustor,and optimizes the fuel injection timing.The optimization design of a new type of double concave combustion chamber is completed.The distribution of the flow field,the combustion characteristics and the emission characteristics are compared with the conventional combustion chamber.The results show that under the structure of a new type of double concave combustion chamber,in the compression process,The strength of the swirl is obviously enhanced,and the flow field distribution of multi swirl coexistence is formed during the expansion process.The expansion swirl promotes the mixing process of oil and gas,increases the diffusion combustion speed,and increases the maximum combustion pressure in the cylinder by 8.6%.In terms of emission characteristics,the amount of NO generation decrease significantly,and the amount of Soot generation increase slightly.In the two aspects of power performance and emission performance,the double concave combustion chamber significantly improved the performance of the rotor engine.Secondly,for the spray characteristics,based on the devices such as fixed volume bomb and high speed camera,the spray characteristics test of the rotor engine was carried out.The effect of spray back pressure and injection pressure on the spray diffusion process was studied.The back pressure value increased from 0.2 MPa to 0.8 MPa,the penetration distance decreased by about 36 mm,the spray cone angle increased by 5.45 degrees,and the atomization effect was obviously improved,indicating that the change of spray back pressure has a significant influence on the spray characteristics,and the effect of the injection pressure on spray characteristics was not evident.Finally,on the basis of the combustion chamber optimization and the study of the spray characteristics,the optimization of the fuel injection timing under the structure of double concave combustion chamber is carried out.The results show that the combustion and emission characteristics are influenced by the distribution law of the flow field and the spray characteristics in the cylinder.When the injection timing changes in the range of 55°BTDC~85°BTDC,on one hand,due to the larger back pressure value of spray environment,the spray cone angle is larger,and the fuel atomization effect is better.On the other hand,due to the late time of the injection,the effect of the swirl on the fuel spray is weak,which leads to the concentration distribution of the two regions at 20°BTDC.When the injection time changes in the range of 95°BTDC~115°BTDC,on one hand,the back pressure is small,and the penetration distance increases,so the effect of fuel atomization is deteriorated.On the other hand,with the injection time advance,the effect time of the swirl on the fuel spray is increased,and the fuel in the cylinder is obviously influenced by the swirl,showing a uniform distribution law.When the injection timing is 105°BTDC,under the action of spray and flow field,the matching effect of fuel distribution and ignition scheme is the best.The swirl in the expansion process significantly promoted the mixing of oil and gas,increased the burning rate,and the maximum combustion pressure reached the maximum value of 4.14 MPa,and the power performance is the best.In terms of emission,considering NO and Soot emission levels,when the injection timing is 105°BTDC,the emission performance is better.When the fuel injection timing is 75°BTDC,the emission performance is the best.In summary,under the double concave combustion chamber structure,considering the power performance and emission performance,the best injection timing parameter is 105°BTDC.