Study On The Methods Of Smoke Simulation Within Aircraft Cargo Compartments

The aircraft cargo smoke detection system should be certified by ground and inflight tests.Currently,the fire smoke is placed by the simulated smoke produced by smoke generator.Engineers have some doubts about the use of smoke generator.It is the important to ensure that the smoke produced by the smoke generator consistent with the fire smoke and that the test results of simulated smoke can represent the real fire test results.The real fire smoke model and smoke diffusion model of smoke generator are established by using computational fluid dynamics software,and smoke experiments of smoke generator are carried out in the laboratory in the study.The different characteristics and smoke diffusion laws between real smoke and smoke generator smoke are studied by simulation.And the influence of smoke factors on smoke simulation is explored.In addition,a smoke simulation method is found.A B707 cargo space geometric model is established.ICEM is used to divide high quality hexahedral grid.Fluent as a CFD software is used to select a reasonable calculation model to calculate the diffusion of fire smoke in cargo compartment.The results show that the diffusion of smoke is a ceiling jet phenomenon,and the established real fire smoke model can accurately predict the experimental results.The smoke experiment and simulation of the smoke generator were carried out in the laboratory.The experimental results were compared with the simulation results,and the smoke diffusion law of the smoke generator was studied,and compared with the real fire smoke diffusion law.The results show that the smoke model of the smoke generator can accurately predict the smoke concentration,and the simulation shows that the smoke diffusion principle of the smoke generator is consistent with that of the fire smoke.Studying the smoke characteristics of smoke generators and different points of smoke released by fire,and studying the influence of smoke concentration,smoke particle size and smoke temperature of smoke generators on smoke diffusion,the results show that there is no obvious law of the influence of 150nm-400 nm particle size and 330k-770 k smoke temperature on smoke diffusion,therefore,in the cargo fire smoke simulation experiment,in the range of 330k-770 k smoke temperature and 150nm-400 nm smoke particle size,there is no need to pay special attention to the influence of smoke temperature and smoke particle size on the approximation of smoke generators to simulate real fire smoke.In addition,changing the release rate of smoke can obviously change the approximation of smoke generator to real fire smoke simulation.If the smoke location is close,the smoke rate should be properly reduced,and if the smoke location is far away,the smoke rate should be properly increased.If the detector is located close to the smoke generator,the smoke rate will have less influence on the alarm time,while the distance will have greater influence.It can provide some reference for airworthiness examination of aircraft cargo smoke.