Power balance method in calculation of helicopter maneuverability taking into account specific operational conditions

A method for evaluating helicopter capabilities to perform standard and advanced aerobatics taking into account specific operational conditions is proposed.     

直升机维修手册创作流程研究

以某民用直升机工作卡的创作为例,阐述和分析了直升机维修手册的创作流程、技术要求、用语规范和图示要求,为今后直升机技术出版物的创作提供方法和参考。     

直升机飞行品质评估数学模型研究

针对飞行品质评估需要，结合建模工作中的经验，讨论了模型复杂度和真实度之间的关系，分析了不同阶次的入流模型和非定常气动模型对结果的影响，考虑了旋翼尾迹对机身的气动干扰作用，并对涡轮轴发动机和飞行控制系统模型在飞行力学模型中的重要作用做了阐述。还地逆仿真方法在飞行品质研究中的应用提出了一些见解。     

直升机综合性能发展态势估算方法

本文提出用首飞期描述直升机综合性能的思想，给出其性能综合评价及发展态势估算方法和模型，运用实际样本资料给出算例，为时序多属性高技术产品性能综合评价及发展态势估算提供思路。     

Aircraft maneuverability improvement by direct lift control system application

The handling qualities of an aircraft will be improved if the Direct Lift Control (DLC) system is applied. In this paper, an attempt has been made to evaluate the influence of DLC-type system parameters on the aircraft's maneuverability and to determine the desired values of these parameters for the purpose of obtaining required values of the handling maneuverability criteria. Published papers which deal with direct lift control do not list requirements for evaluating handling qualities and maneuverability of aircraft equipped with DLC system. In this paper, three new criteria permitting the evaluation of results of employing DLC have been defined. Analysis of influence of DLC system parameters on selected known handling qualities criteria (for example CAP, C^*), as well as new DLC efficiency coefficients, have been illustrated with a numeric example of A4D “Skyhawk” fighter aircraft and PZL M-18 “Dromader” agricultural airplane control system modification.     

Development of the discrete vortex cylinders method for calculating the helicopter rotor induced velocity

The numerical method for calculating the induced velocities of the helicopter rotor was developed based on Shaidakov’s disk theory. The numerical experiments were performed to test and estimate the method developed.     

Nonlinear autopilot for high maneuverability of bank-to-turnmissiles

This paper presents a novel approach to autopilot design for highly maneuvering bank-to-turn (BTT) missiles. In the design and performance analysis of the proposed nonlinear autopilot, all nonlinearities of missile dynamics including the coupling between roll, yaw, and pitch channels as well as the asymmetric structure of missile body are taken into full account. It is shown that through a kind of feedback linearization technique along with a singular perturbation-like technique, the input/output (I/O) dynamic characteristics of pitch, yaw, and roll channels are made linear, decoupled, and independent of flight conditions such as air density and missile velocity. In particular, the proposed autopilot controllers can provide excellent set-point tracking performance for roll and pitch channels while keeping the side-slip angle negligible. The generality and practicality of our approach are demonstrated through mathematical analysis and various simulation results using an ILAAT missile     

通用型武装直升机调整试飞的主要流程和方法设置

武装直升机的调整试飞工作主要分两部分进行:第一部分为平台(直升机本身)的调整试飞;第二部分为航电、武器火控系统的调整试飞。在这两部分都调整到位后才能达到鉴定技术状态。本文就武装直升机的平台和航电、武器火控系统的调整试飞流程和方法设置做几点阐述,通过交流积累经验,规避风险,减少不必要的飞行时间架次,缩短调整试飞周期,为武装直升机的调整或鉴定试飞提供技术参考。     

Identification method for helicopter flight dynamics modeling with rotor degrees of freedom

A comprehensive method based on system identification theory for helicopter flight dynamics modeling with rotor degrees of freedom is developed. A fully parameterized rotor flapping equation for identification purpose is derived without using any theoretical model, so the confidence of the identified model is increased, and then the 6 degrees of freedom rigid body model is extended to 9 degrees of freedom high-order model. Bode sensitivity function is derived to increase the accuracy of frequency spectra calculation which influences the accuracy of model parameter identification. Then a frequency domain identification algorithm is established. Acceleration technique is developed furthermore to increase calculation efficiency, and the total identification time is reduced by more than 50% using this technique. A comprehensive two-step method is established for helicopter high-order flight dynamics model identification which increases the numerical stability of model identification compared with single step algorithm. Application of the developed method to identify the flight dynamics model of BO 105 helicopter based on flight test data is implemented. A comparative study between the high-order model and rigid body model is performed at last. The results show that the developed method can be used for helicopter high-order flight dynamics model identification with high accuracy as well as efficiency, and the advantage of identified high-order model is very obvious compared with low-order model.     

反潜直升机吊放声纳水面舰艇编队尾后锯齿形法搜潜

针对水面舰艇编队尾后方向的潜艇威胁,研究反潜直升机使用吊放声纳搜潜中的警戒扇面、兵力需求、参数决策等问题。通过分析锯齿形法特点、吊放声纳搜潜过程,建立了多机舰艇编队尾后搜潜的警戒扇面定量计算模型。研究了齿形法相邻探测点间距系数、搜索速度等制约因素,探索了吊放声纳作用距离与潜艇航速的定量关系,给出了已探测区等效圆半径的计算方法。仿真计算了舰艇编队尾后搜潜中实际对潜警戒扇面、最优间距系数、不同任务要求下的兵力需求。结果表明:配置2架直升机于舰艇编队尾后15海里处,可建立80.9°的对潜警戒扇面;齿形法最佳间距系数介于1.1~1.3之间。     

Robust Navier-Stokes method for predicting unsteady flowfield and aerodynamic characteristics of helicopter rotor

A robust unsteady rotor flowfield solver CLORNS code is established to predict the complex unsteady aerodynamic characteristics of rotor flowfield. In order to handle the difficult problem about grid generation around rotor with complex aerodynamic shape in this CFD code,a parameterized grid generated method is established, and the moving-embedded grids are constructed by several proposed universal methods. In this work, the unsteady Reynolds-Averaged Navier-Stokes(RANS) equations with Spalart-Allmaras are selected as the governing equations to predict the unsteady flowfield of helicopter rotor. The discretization of convective fluxes is accomplished by employing the second-order central difference scheme, third-order MUSCL-Roe scheme, and fifth-order WENO-Roe scheme. Aimed at simulating the unsteady aerodynamic characteristics of helicopter rotor, the dual-time scheme with implicit LU-SGS scheme is employed to accomplish the temporal discretization. In order to improve the computational efficiency of holecells and donor elements searching of the moving-embedded grid technology, the ‘‘disturbance diffraction method and ‘‘minimum distance scheme of donor elements method are established in this work. To improve the computational efficiency, Message Passing Interface(MPI) parallel method based on subdivision of grid, local preconditioning method and Full Approximation Storage(FAS) multi-grid method are combined in this code. By comparison of the numerical results simulated by CLORNS code with test data, it is illustrated that the present code could simulate the aerodynamic loads and aerodynamic noise characteristics of helicopter rotor accurately.     

Panel/full-span free-wake coupled method for unsteady aerodynamics of helicopter rotor blade

A full-span free-wake method is coupled with an unsteady panel method to accurately predict the unsteady aerodynamics of helicopter rotor blades in hover and forward flight. The unsteady potential-based panel method is used to consider aerodynamics of finite thickness multi-bladed rotors, and the full-span free-wake method is applied to simulating dynamics of rotor wake. These methods are tightly coupled through trailing-edge Kutta condition and by converting doublet-wake panels to full-span vortex filaments. A velocity-field integration technique is also adopted to overcome singularity problem during the interaction between the rotor wake and blades. Helicopter rotors including Caradonna-Tung, UH-60A, and AH-1G rotors, are simulated in hover and forward flight to validate the accuracy of this approach. The predicted aerodynamic loads of rotor blades agree well with available measured data and computational fluid dynamics (CFD) results, and the unsteady dynamics of rotor wake is also well simulated. Compared to CFD, the present method obtains accurate results more efficiently and is suitable to rotorcraft aeroelastic analysis.     

直升机旋翼黏弹阻尼器时域动力学建模与分析

建立一种适用于旋翼气动弹性分析的黏弹阻尼器模型,该模型考虑了黏弹材料本身的刚度非线性及激振力频率和幅值对黏弹阻尼器应力-应变关系的影响。通过引入新型几何非线性弹簧模块,根据需要调整模型的刚度变化规律,避免了现有黏弹阻尼器模型模拟不同类型材料时因刚度变化规律差异而需重新建模的缺陷,模型适应性强。模型采用多个内变量场,既能体现阻尼器幅变特性,也能准确反映多频激励下的黏弹性特性。以两种不同类型黏弹材料制造的黏弹阻尼器为研究对象,在旋翼黏弹阻尼器的典型工作幅值和频率范围内,进行了简谐实验。利用建立的旋翼黏弹阻尼器非线性时域动力学模型,计算不同类型黏弹材料制造的阻尼器在多种应变幅值、频率下的动态特性并与实验相比较,分析了黏弹阻尼器损耗模量、储能模量频变特性和双频激励对阻尼器的影响。结果表明,建立的非线性黏弹阻尼器动力学模型能够更好地反映不同类型黏弹材料构成的黏弹阻尼器的动刚度和阻尼,适合于直升机旋翼载荷计算和气动弹性分析。     

拉刀CAD自动设计方法的探讨

开发了一个基于Microsoft Windows操作系统的拉刀参数化CAD和图档与设计文档管理系统。介绍了系统的总体方案及基本功能模块，探讨了基于网络的图文档案数据库管理、系统安全等相关问题。     

基于CFD和混合配平算法的直升机旋翼地面效应模拟

建立了一套基于非结构网格技术和动量源模型的直升机旋翼计算流体力学(CFD)方法,用来模拟贴地飞行时直升机旋翼非定常气动特性。其中,控制方程采用三维Navier-Stokes方程,空间方向上采用Jameson格式,时间方向上采用五步Runge-Kutta迭代法,选用Spalart-Allmaras湍流模型。旋翼对流场的作用采用动量源项模拟,为更真实地模拟地面效应(IGE)的作用,采用了"移动地面"的物面边界来代替常规的"固定地面"边界,并对旋翼附近及旋翼与地面之间的网格进行加密处理,以提高地面涡的捕捉精度。考虑实际飞行环境下旋翼的运动和操纵,在流场计算时考虑旋翼配平特性。其中,配平方程的旋翼气动力通过CFD方法和动量-叶素组合理论模型的耦合计算给出,为了提高配平方法的鲁棒性和效率,提出并建立了基于遗传算法/拟牛顿法的高效混合迭代算法。运用所建立的方法,首先,选用有试验结果可供对比的算例计算了地面效应作用下的旋翼拉力增益、功率变化,验证了计算方法的有效性,解决了涡流理论方法较难模拟的"小速度前飞旋翼需用功率突增"问题。然后,着重研究了UH-60A直升机旋翼在不同离地高度、不同前进比状态,旋翼需用功率、诱导速度、地面涡及旋翼操纵的变化规律。计算结果表明:地面涡出现在较小的前进比范围内,随前进比的增大,地面涡在纵向平面将顺来流方向移动,在轴向方位靠近地面方向移动,直至最后不断减弱消失。     

浅谈舰载直升机的海上试飞

针对舰载直升机的特殊使用环境，分析了舰船运动情况对舰载直升机实施起飞、着舰和舰上机动飞行的影响，最后，探讨了MIL－F－83300等直升机规范对舰载直升机的各种使用规定及特殊的飞行品质要求。     

High-efficiency prediction method for helicopter global/ground noise based on near-field acoustic holography

Abstract Noise reduction program design is an effective approach that relies on efficient noise prediction for reducing ground noise during flight. The existing noise prediction methods have the limitations of being computationally expensive or only applicable to far-fields. In this paper, a HighEfficiency Prediction Method (HEPM) for helicopter global/ground noise based on near-field acoustic holography is proposed. The HEPM can predict the global noise based on acoustic modal analysis and has the advantages of high prediction accuracy and low time cost. The process is given as follows:firstly, the rotor noise on the holographic surface in the specified flight is obtained by simulations or experiments. Secondly, the global noise model, which maps time-domain noise to acoustic modes, is established based on near-field acoustic holography and Fourier acoustic analysis methods. Finally, combined with acoustic modal amplitude, the model established enables efficiently predicting the global/ground noise in the corresponding flight state. To verify the accuracy of the prediction method, a simulation study is conducted in hovering and forward flight states using a model helicopter with a 2-meter rotor and Rotor Body Interaction (ROBIN) fuselage.The comparison of HEPM with numerical results shows that the average prediction errors of the global and ground noise are less than 0.3 d B and 0.2 d B, respectively. For a region containing100000 observers, the computation time of the HEPM is only one-fifth of that of the acoustic hemisphere method, demonstrating the rapidity of the proposed method.     

直升机飞行过渡速度现象研究

针对直升机飞行中通过过渡速度时产生的振动、抬头、偏转和倾斜等一系列现象,从旋翼动力学的角度进行了深入的研究,并且给出了系统的解释.首先,分析了旋翼尾涡对直升机状态的影响;然后,研究了桨涡干涉效应,发现桨涡干涉效应导致旋翼前行桨叶平均拉力增加、后行桨叶平均拉力减小,这是引起直升机抬头、倾斜和振动的根本原因;最后,研究了起飞和着陆中通过过渡速度时操纵对策的差异及其原因.     

Investigation of power gas turbine drives on the basis of mathematical models

A method for investigation of power gas turbine drives on the basis of mathematical models that makes it possible to enhance an information content and precision of existing techniques of power audit is proposed.