Analysis Of The Effect Of External Air Flow In Aero Engine Components Fire Test

The fire test of aero engine components is an important means to inspect the fireproof and fire resistance of engine components.The use of burners for flat plate impact test is currently the main method for studying engine fire test.However,there is no uniform fire test standard and general experimental conditions for aero-engine components,but the existing research has clearly pointed out that the laboratory environment will directly affect the test results.To determine the law of influence of the external environmental factors on the fire test,this paper studied the dimensions and environment of the test piece by means of simulation.The influence of temperature,external air flow velocity and external air impact angle on the ablation of the test piece was analyzed,and its influence law was determined,which will provide a certain reference for the future definition of environmental conditions of fire test.Firstly,the NexGen burner and its simulation model were introduced.In order to improve the computational efficiency,a simplified model was established.Using the flame surface method and the suitable numerical models to simulate the combustion flame.Near-wall Y+ validation and mesh-independence verification confirmed the validity of the grid,and verified the effectiveness of flame of the simplified simulation model by comparing the flame velocity,temperature and heat flux fields of the two models,and comparing the simulated values with experimental values of the University of Cincinnati.Secondly,the impact of the test piece size on the ablation of the test piece was analyzed.This section consists of three test pieces with lengths of 12 inches,18 inches,and 24 inches and a thickness of 1/4 inch.Simulation studies were carried out without external air impingement to investigate the test piece size versus surface heat transfer,surface temperature distribution,and the impact of the burning properties of the test pieces,studies have shown that as the size of the test piece increases,the melting rate of the test piece gradually decreases,and the 24-inch test piece is most likely to burn through.Finally,the influence of the external airflow environment on the ablation of the test piece was investigated.The main influencing factors of the external airflow were determined as the ambient temperature,the airflow velocity,and the direction of the airflow impact.The simulations without ambient air flow were performed at ambient temperatures of 280 K,290K,300 K,and 310 K.It is found that the ambient temperature has less effect on the ablation of the test piece without the external airflow.At ambient temperature of 300 K,three different forward airflow were respectively used to impact the back of the test piece,studies have shown that as the environmental speed increases,the melting rate gradually decreases,and the burn-through time of the test piece gradually increases.And by simulating under different temperature environments and different airflow impact speeds,it was found that the test pieces could not be burned through in the environment of low-temperature high-speed airflow impact.Besides,the influence of lateral air flow impact on the ablation of the test piece was explored,the simulations of small-size and large-size test pieces were carried out under different speeds of lateral air flow,and the study found that lateral airflow has a greater impact on the ablation of small-sized test pieces.