外吹式襟翼动力增升效果评估方法

外吹式动力增升襟翼可以有效地缩短运输类飞机的起降距离,其增升效果评估方法是运输机动力增升设计的关键技术之一。本文采用基准气动力耦合速度修正方法,发展了一套适用于外吹式襟翼动力增升效果快速评估的计算方法;该方法充分考虑了动力增升飞机性能计算对气动力数据的需求,解决了传统推力系数法的小速度大推力系数求解限制问题、无法准确求解离地速度以及多速度点气动力求解引起的计算效率问题。以某运输机为例,分析了其气动力及起飞性能,对其外吹式襟翼动力增升效果进行了评估,验证了方法的正确性。研究表明:通过优化动力增升襟翼偏转角,起飞滑跑距离最大减小量可达到25%;过大的襟翼偏转角将显著地增加飞机阻力,不利于缩短起飞滑跑距离。研究工作对运输机的外吹式动力增升襟翼设计,具有一定的工程指导价值。

Method for evaluating powered high-lift effects of externally blown flap

Externally blown flaps are usually adopted to shorten the takeoff and land distance of transport aircrafts,and the method for evaluating the powered high-lift effect of the externally blown flap is one of the most important techniques in the design of transport aircrafts.A method for rapidly evaluating the powered high-lift effect of the externally blown flap is developed by coupling basic aerodynamics with the velocity correction technique.The proposed method takes into consideration the requirements for aerodynamic data in the performance computation of powered high-lift aircrafts,and can overcome disadvantages of classical trust coefficient method,such as low speed,limits of large thrust coefficient computation,low precision in solving unstick speed,and inefficiency of solving the problem of aerodynamic loading at multi-velocity point.The aerodynamic and takeoff performance of a transport aircraft are analyzed and the powered high-lift effects of the externally blown flaps are evaluated to validate the proposed method.The results show that the takeoff running distance can be shortened by 25％ by deflecting the flaps rationally.However,with too large deflection angle of powered high-lift flaps,the aircraft drag will increase dramatically to go against shortening the takeoff running distance.The research results would provide some guidance for the design of externally blown flaps.