The Numerical Simulation Of Sands’ Trajectory In Air Flow Channel

During takeoff and landing aero-engine may inhale some of particles such as dust, sand, weed, andice. These particles flowing into the core engine may cause engine failure, so to inferunce service lifeand reliability, and then to affect comprehensive capabilities and safety of aircraft. Especially for thetransport aircraft and helicopter, it may inhale foreign objects more easily because of take-off frominformal airport. In this paper, a group of sands’ trajectory in fan air flow channel of turbo-fan enginehas been studied to guide the engine design, so that percentage of particles flying into the core enginecan be reduced. This research is committed to estimate the percentage of particles flying into the coreengine from the statistical results of a lot of sand particles.In this paper, determinate particle trajectory model has been used to calculate the sand particeltrajectory in flowfield. Since the objective of this study is to calculate statistically the percentage ofparticles flying through the bypass of the fan, sphere shape assumption can be used to simulate thisstatistical result. The trajectory is calculated by considering aerodynamic force and rebound from themetal surfaces. After the CFD result of fan model with intake cone imported into MS SQL Serverdatabase system, every gride node’s flow parameter database has been obtained. And the reboundmodel database can be also obtained from various kinds of rebound simulation in different conditions.When the sand particles fly into the air flow, the relative flow parameter of air flow around the sandparticle is calculated with interpolation considering the distance between the sand particle and nodesas average weight. When the sand particles impact the metal boundary of air flow channel, databaseinterpolation will calculate the relational rebound velocity and direction.A calculation program is implemented by Visual C++6.0platform, an object-oriented language.Database technology using in this simulation accelerates the data storage and inquiry, so that onetrajectory simulation takes only less than30seconds in data of millions nodes. Typically, the sandparticle trajectory can be shown in the visual graphic interface quickly and the percentage of sandparticles flowing into core engine cand be obtained. From present research, a series of conclusion canbe known as follows:The viscous drag force of air flow and the impact of sand particles and metal surface is a majorfactor to influence the particle trajectory. When sand particles flying in the air flow, drag force is thekey factor which forces the particles following with air flow. It is much likely to inpact the intakecone, bldes, hub or engine casing when partilces flying into fan blade channel, which will change theoriginal trajectory of sand particles. When sand particles impact the metal surface, the increasing of impact angle leads to the increasing of energy loss of collision, which will result the increase ofvelocity loss. Because of the relatively large enough impact velocity and short impact time, theinfluence of friction from metal surface can be ignored. In given area, different size of sand particleswill greatly influence on the air flow drag force but has no affect when sand particles impact metalsurface.The research of particles movement in air flow channel is always important in research of particleseparater equipment. This paper provides a representative simulation method used in simulatingparticles trajectory in complicated air flow channel, which can be extended to other situation.