Icing Calculation,Wind Tunnel Experiment And Flight Test For Large Civil Aircraft

The ice accretion is one of the main factors that threaten civil aircraft flight security and affect the flight performance.This paper represents a deep and systematical study of the large civil aircraft icing problem including the aerodynamic characteristics of aircraft icing,the determination of critical ice shape and wind tunnel test validation,hybrid wing design and wind tunnel test validation,stimulant ice fabrication and testing and flight test study.The numerical simulation of CFD with different ice shapes for one-and multi-section airfoil is carried out and the results are in good agreement with the experimental results.The influence of different ice shapes on the aerodynamic characteristics of a given airfoil is obtained,which lays a foundation for the judgment of critical ice shape.A method to determine the critical ice shape of large civil aircraft is developed.Based on the sensitivity analysis of the parameters which affect the icing on the aircraft using numerical simulation and icing tunnel experiment,the conditions of severe icing are obtained.Then,the critical ice shapes on the wing and horizontal tail are obtained according to the judgement of critical ice shape and analysis principle,by combining the icing shapes under the severe icing conditions.According to the similarity criterion,the critical ice shape of the model is calculated and the wind tunnel test is carried out.The calculated critical ice shape agrees with the experimental ice shape,veridating the developed critical ice shape determination method.A hybrid wing design method is proposed for ice wind tunnel test,and is then applied to ice wind tunnel test of civil aircraft ice accretion on wings.The Navier-Stokes(N-S)equations are used to calculate the distribution of the airfoil pressure,to make the pressure distribution near the leading edge of the hybrid and original airfoil as uniform as possible.A method called the simple influence coefficient and control point linear interpolation,is proposed.The design chord length of the hybrid wing is shortened by 40% on the basis of the same leading edge between the hybrid and original airfoil.The hybrid wing at the same angle of attack has the same pressure distribution near the leading edge as the original airfoil,so as to ensure that the both have the same water droplet impact characteristics and icing conditions.The design theory and design results lay a sound foundation for the ice wind tunnel test of civil aircraft type.The flight test and ice model modification design for the ice bars on Radoar cover,leading edge slats,wing tips,vertical tail,horizontal tail and the engine pylon wre carried out,including the ice bar structure design,manufacturing,performance testing and on-site installation,removal and so on.The fiberglass core sandwich structure is light in weight and fulfills the rigidity and strength requirements and is made of three-dimensional numerical control machine tool,which can meet the requirements of size precision.The inner and outer panels were made by hand laying technology to simulate the ice core sandwich structure.The forming process is simple and the quality is stable.The experimental results show that the strength of the ice bond between the simulated ice bars and the skin was very high,and it was concluded that the ice bars in the flight process would not fall off.It is feasible to produce simulated ice bars by direct installation in the worksite.The use of epoxy resin for easy peeling and demolition can ensure the aircraft surface quality.