旋翼/平尾气动干扰对直升机配平特性的影响分析

Analysis on influence of rotor/empennage aerodynamic interaction on helicopter trim characteristic

旋翼/平尾气动干扰建模是直升机全机配平模型和飞行动力学模型的核心内容。常规全机配平模型主要通过旋翼下洗流或诱导速度等方式间接考虑旋翼对平尾的气动干扰作用,但未充分考虑旋翼对平尾非定常气动干扰产生的非线性气动载荷,因而仍难于准确体现旋翼/平尾气动干扰对全机配平特性的影响。为此本文基于非定常面元/黏性涡粒子法,通过在平尾面元中增加由旋翼和平尾尾迹时变干扰产生的非定常压力项,建立旋翼/平尾气动干扰模型,直接计算平尾非线性气动载荷,并耦合基于GA/LM混合优化的直升机全机配平方法,构建旋翼/平尾气动干扰作用下的直升机全机配平特性分析方法。通过计算UH-60A直升机的旋翼操纵量和机体姿态,并与试验测试值对比验证本文方法的准确性。通过与基于诱导速度考虑旋翼/平尾气动干扰的直升机配平结果比较表明,后者难于体现直升机低速纵向操纵量和机体俯仰角突增现象,而本文方法能较好地体现直升机低速纵向操纵量和机体俯仰角突增,且与OH-6A、EH-101等试验测量的特性一致。研究不同平尾构型对旋翼/平尾气动干扰下直升机全机配平特性的影响,分析表明低平尾产生较大的低速纵向操纵量突增,而高平尾则增加高速纵向操纵量;前置平尾产生较大的低速纵向操纵量突增,右旋直升机的右置平尾有利于减小低速纵向操纵量突增和机体俯仰角。

Unsteady aerodynamic interaction of rotor and empennage is the core content of helicopter trim model and flight dynamic model. The rotor/empennage aerodynamic interaction effect was considered indirect- ly through rotor inflow or induced velocity of rotor wake in classical trim method. However, the nonlinear air- load induced by the unsteady aerodynamic interaction was not fully taken into account, and it is then difficult to reflect the influence of the rotor/empennage aerodynamic interaction on the trim characteristic. Therefore, based on unsteady panel/viscous vortex particle method, a rotor/empennage unsteady aerodynamic interaction- al model is established by adding an unsteady pressure term into empennage panel which is induced by un- steady interaction of rotor and empennage wake, and the nonlinear airload on empennage is simulated. The helicopter trim characteristic analysis method under rotor/empennage aerodynamic interaction is then estab- lished by coupling with helicopter trim method based on GA/LM hybrid optimization. The control of rotor and attitude of fuselage of UH-60A are simulated and compared with the flight test data to validate the present method. Compared with the result of the classic helicopter trim method in which rotor/empennage aerodynamic interaction is indirectly accounted through induced velocity, it is shown that the increase of longitudinal control and fuselage attitude is not simulated by the classic helicopter trim method; however, the phenomenon is cap- tured by the present method, and is consistent with the tested characteristics of OH-6A, EH-101, etc. The in- fluence of empennage＇ s type on helicopter trim characteristic is then analyzed, and it is shown that the in- crease of rotor longitudinal control is great with low-set empennage, forward-set empennage in low-speed for- ward flight, and high-set empennage in high-speed forward flight. Start-set empennage for right revel rotor is useful to decrease the increasement of longitudinal control and fuselage attitude in low-speed forward.