论文部分内容阅读
旋翼/平尾非定常气动干扰是导致直升机纵向“抬头(Pitch-up)”现象的主要原因。为在直升机设计阶段准确分析旋翼/平尾非定常气动干扰以及由此引起的低速纵向操纵特性变化,通过涡量等效原则和Neumann物面边界条件建立了适用于旋翼/平尾气动干扰分析的非定常面元/黏性涡粒子混合法。该方法耦合了考虑尾迹时变效应的非定常面元法、黏性涡粒子法及涡量镜面法,以准确模拟旋翼和平尾的非定常气动载荷、旋翼尾迹的非定常特性以及旋翼尾迹对平尾的气动干扰效应。首先通过计算NASA ROBIN(Rotor Body Interaction)旋翼尾迹几何和诱导速度分布,并与实验测量值、时间精确自由尾迹及CFD计算结果对比验证方法的准确性。相比于时间精确自由尾迹,本文方法计算精度更高。随后分析了旋翼/平尾非定常气动干扰对平尾向下气动载荷和气动导数的影响,并分析了平尾构型对旋翼/平尾非定常气动干扰的影响规律。分析表明:旋翼尾迹与平尾干扰导致低速状态的平尾载荷突增,气动导数反号;低平尾气动载荷突增较大,高平尾较小,但高速气动导数反号;前置平尾载荷突增量减小,但对应速度范围较宽;右旋直升机右平尾载荷突增量较小,但气动导数特性基本不变。
Rotor / Flat Tail Unsteady aerodynamic interference is the main cause of the “Pitch-up” phenomenon in the longitudinal direction of a helicopter. In order to accurately analyze the unsteady aerodynamic disturbances of the rotor / tail at the helicopter design stage and the resulting low-speed longitudinal maneuvering characteristics, the unsteady aerodynamic analysis of rotor / tail-end aerodynamic interference was established by the principle of vorticity equivalence and Neumann surface boundary conditions Bone / viscous vortex particle mixing method. The method coupled with the unsteady face element method, viscous vortex particle method and vorticity mirror method, which takes into account the time-varying wake effects, can accurately simulate the unsteady aerodynamic loads of rotor and tail, the unsteady characteristics of rotor wake, Pneumatic interference effect. First, by calculating rotor geometry and induced velocity distribution of NASA ROBIN (Rotor Body Interaction), the accuracy of the method is verified by comparison with experimental measurements, time-accurate free wake and CFD calculation results. Compared with the time-accurate free wake, the proposed method is more accurate. Then the influence of the unsteady aerodynamic disturbance of the rotor / tail on the aerodynamic loads and aerodynamic derivatives of the tail is analyzed. The influence of the flat tail configuration on the unsteady aerodynamic disturbance of the rotor / tail is analyzed. The results show that the rotor tail and tail-tail disturbance cause sudden increase of flat-tail load and inverse number of aerodynamic derivative at low speed. The dynamic load of low-level tail gas suddenly increases sharply, But the corresponding speed range is wider; the sudden increase of right-tail-tail load of right-handed helicopter is smaller, but the characteristics of aerodynamic derivative are basically unchanged.