Research On Atomization Characteristics In High Speed And Low Pressure Flow

There are many problems in ramjet combustor in high speed and low pressure flow,especially the low combustion efficiency,which is fundamentally traced back to the atomization in high-speed and low-pressure environment.In order to solve the above problems,the research on fuel atomization characteristics under high-speed and low-pressure environment is of great significance for improving fuel supply in RAM combustor,improving fuel atomization quality and solving combustion efficiency problems in RAM combustor in the future.The main research work of this paper is carried out in two directions: one is to complete the numerical simulation of fuel atomization characteristics under high-speed and low-pressure environment;the other is to carry out experimental research using PIV at the same time,and to obtain fuel trajectory and particle size information using image processing technology.The two parts aim at complementing and perfecting the characteristics of fuel penetration depth,fuel atomization particle size and fuel concentration spatial distribution under high-speed and lowpressure environment.The main variables in this study include air temperature T(300-800K),ambient pressure P(0.02-0.05MPa),Mach number Ma(0.17-0.25),fuel pressure difference P(0.2-1 MPa),fuel-air ratio(2.85-5.53),fuel rod distance from the stabilizer trailing edge L(100-200 mm).The results show that:(1)the penetration depth of fuel increases with the increase of fuel pressure difference,inflow Mach number,fuel-air ratio and injecting hole diameters,and decreases with the increase of air temperature and pressure;(2)there are many factors affecting fuel particle size,which are not monotonous because of the change of some factors.With the increase of oil pressure difference,the atomization becomes worse in the distance from the nozzle,and the trend of fuel atomization is closer with the increase of distance;with the increase of temperature,the atomization effect will be better than the normal temperature in the range higher than the normal temperature,but there may be some high temperature effect will be slightly worse;with the increase of air pressure,the fuel atomization will become worse;with the increase of Mach number,the fuel particles will break down.The number of fragments is more,but the change of particle size along the way is larger at the nozzle outlet and closer at the back.Weber number has a certain influence on fuel atomization particle size,but a single Weber number is not enough to describe the rule of particle size change.(3)Under different gas-thermal parameters,the spatial distribution of fuel always has the same rule: with the increase of radial or flow direction distance,the fuel concentration decreases gradually.The results of this study provide a reference for the fuel atomization characteristics of ramjet combustor in high-speed and low-pressure environment,and have a certain guiding significance for the design of ramjet combustor in high-speed and low-pressure environment.