| The Synergetic Air-Breathing Rocket Engine(SABRE)is a revolutionary new type of deeply precooled combined cycle engine,which could expand the flight envelope,increase trust and the weight-to-weight ratio.The precooling heat exchanger and the air intake are the key components of the SABRE engine.The precooler is installed in the air intake,and the temperature of high-temperature air is greatly reduced after passing through the precooler.How to realize the integrated design of precooler and air intake,and use CFD(Computational Fluid Dynamics)numerical simulation to simulate the precooling effect of the precooler are the key technologies of precooler engine.In this paper,a precooler engine intake is designed for SABRE-3 engine.Based on this,multiple precooler and inlet integration solutions are proposed.With different precooling calculation methods,the effects of precooling on the flow characteristics of engine inlet were studied,and the feasibility of precooling calculation methods was explored.First of all,based on the design method of external pressure inlet,a axisymmetric variable inlet for precooled engine was made to achieve the sealed design of center cone shock wave for each working condition.Numerical simulation was used as a research method to calculate the critical state of inlet in each working condition,and the performances under critical state were also calculated.The results show that:mass flow ratio of inlet in the whole envelope is basically above 0.97,and the terminal shock wave is stabilized behind the windshields;in critical state,the performance of inlet is better at low-speed conditions,the total pressure recovery coefficient of two channels which is lower at high-speed conditions,gradually decreases with the increase of Ma_?.Secondly,two integrated models of linear precooler,stepped precooler and inlet were designed.The flow field of critical-state inlet without precooling was used as basic flow field and the influences of cooling effect of linear precooler on the inlet characteristics were studied under different precoolers and different installation angles by single source term method which was used to cool the high-temperature air.The results show that:After precooling,the total temperature of turbine channel outlet of two precoolers/inlet could be reduced below 320K at low-speed conditions.Mass flow ratio of turbine channel is basically higher than without precooling,and the total pressure recovery coefficient doesn't change much.Different installation angles will affect inlet.The cooling performance of 30°linear precooler is the best and the total temperature of turbine channel is uniform.Finally,an integrated model of 30°liner precooler and inlet was designed.A porous media coupled source term method was carried out to simulate the pressure drop effect and cooling effect of precooler,and the feasibility of simulating fluid resistance and pressure drop in porous media was verified.The influences of precooling effect of the flow characteristics of inlet were studied,and the precooling performance of four methods under two schemes was compared.Studies indicate that porous media in stepped precooler/inlet could give consideration to simulate both pressure drop effect and cooling effect and terminal shock wave moves forward a distance after precooling.The total temperature of turbine channel outlet under each working condition decreases by 49%?73%,among which the total temperature at low-speed conditions reduces to around 210K.Under the precooling effect,the exit Mach number of turbine channel outlet is reduced,and its mass flow ratio decreases by about 9%?20%comparing with before precooling.The change of total pressure recovery coefficient of the two channels before and after precooling is not obvious. |
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