Study On Spray Evaporation And Ignition Characteristics Of Diesel In Constant Volume Bomb At High Temperature

In order to realize the lightweight of diesel engine,a design idea of high power density diesel engine was put forward.High power density diesel engine can achieve a high power rise,the same size of diesel engine output more power,.The temperature and density of the combustion chamber of the high power density diesel engine in the process of jet combustion are very high.In view of this situation,it is of great significance to study the evaporation and ignition characteristics of diesel spray under high temperature.In this paper,a premixed combustion type constant volume combustion bomb platform is used to test the evaporation and ignition characteristics of diesel fuel under high temperature.Various optical methods are used to obtain the required image of the test,the MATLAB program is used to process the images,all kinds of characteristic data of the spray are obtained,and the data are analyzed and analyzed.Firstly,the evaporation characteristics and ignition characteristics of diesel spray under different ambient temperature conditions are studied.Five test temperature conditions of 900 K,1100K,1200 K,1300K and 1400 K are studied.The experimental results show that the penetration distance of spray is sensitive to temperature.The higher the temperature is,the shorter the penetration distance is.The temperature has no effect on the macro penetration and diffusion characteristics of spray evaporation.On the other hand,under the condition of too high ambient temperature,too short ignition delay and too close to the nozzle are the main reasons for combustion deterioration.Then,starting with the injection strategy and EGR rate,the favorable factors for improving combustion deterioration at high temperature are explored.The evaporation and ignition characteristics of 1200 K ambient temperature under different injection duration and ignition characteristics under different oxygen concentration conditions are tested.The results show that the fuel injection duration has little effect on evaporation and ignition characteristics,but shorter fuel injection duration has better oil-gas mixing effect.The higher the oxygen concentration,the shorter the ignition delay period,the larger the proportion of diffusion combustion,and the more soot generated during combustion.However,the combustion duration is shorter when the oxygen concentration is higher,and the concentrated exothermic is beneficial to the oxidation of soot.When the oxygen concentration is low,the combustion duration is too long,the ignition delay is prolonged,and the premixed combustion ratio is increased,but the soot generated may not have enough time to be oxidized.