舰载机滑跃起飞斜板形状的优化研究

根据动力学原理，建立了考虑起落架变形运动影响的飞机在甲板上的运动方程，提出了舰载飞机滑跃起飞斜板形状的最优化数学模型性能指标，约束条件和目标函数。其中，引进了罚函烽，把有约束的极值问题化为无约速的极值问题，并采用Ｐｏｗｅｌｌ法以及用商代替导数的ＤＦＰ方法进行了优化计算。计算结果表明，对斜板形状进行优化后，可以在很大程度上提高舰载机的斜板滑跃起飞性能。     

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.     

让客户支援成为直升机制造业的核心竞争力

随着近年来我国直升机事业的迅猛发展,直升机销售额日益增长,直升机制造业规模不断扩大,客户支援团队也在日益壮大,同时对整个客户支援力量的要求也越来越高。这就出现了一个问题——直升机群体的增大造成了客户支援管理难度的大大增加,这是所有直升机制造业面临的问题,需要更合理地构建一流客户支援体系,提高客户满意度,提升直升机制造业产品的市场竞争力。     

直升机结构承载能力研究

介绍用迭代方法求解直升机结构承载能力的过程,求解非线性方程。计算时,首先假定结构是给定的,求出结构最大承载能力;以某一直升机模拟试验件为例,算出各试验件每一元素的应力、位移、屈服情况、失稳部位随着加载过程而变化情况以及最大承载能力等。计算结果与试验结果吻合很好。     

直升机复合材料结构试验与分析一致性技术的应用研究

本文主要进行了一致性评判技术在直升机复合材料结构试验与分析中的应用研究。对复合材料典型结构件,本文先进行了有限元建模及分析计算;然后进行了相应的强度试验并得出试验结果。通过对位移计算结果和试验结果的对比分析,本文对其进行了一致性模糊综合证券,从而验证了该评判方法的有效性。     

Sensor selection of helicopter transmission systems based on physical model and sensitivity analysis

In the helicopter transmission systems, it is important to monitor and track the tooth damage evolution using lots of sensors and detection methods. This paper develops a novel approach for sensor selection based on physical model and sensitivity analysis. Firstly, a physical model of tooth damage and mesh stiffness is built. Secondly, some effective condition indicators(CIs) are presented, and the optimal CIs set is selected by comparing their test statistics according to Mann–Kendall test. Afterwards, the selected CIs are used to generate a health indicator(HI)through sen slop estimator. Then, the sensors are selected according to the monotonic relevance and sensitivity to the damage levels. Finally, the proposed method is verified by the simulation and experimental data. The results show that the approach can provide a guide for health monitoring of helicopter transmission systems, and it is effective to reduce the test cost and improve the system's reliability.     

Progress in helicopter infrared signature suppression

Due to their low-attitude and relatively low-speed fight profiles, helicopters are subjected to serious threats from radio, infrared(IR), visual, and aural detection and tracking. Among these threats, infrared detection and tracking are regarded as more crucial for the survivability of helicopters. In order to meet the requirements of infrared stealth, several different types of infrared suppressor(IRS) for helicopters have been developed. This paper reviews contemporary developments in this discipline, with particular emphasis on infrared signature suppression, advances in mixer-ejectors and prediction for helicopters. In addition, several remaining challenges, such as advanced IRS, emissivity optimization technique, helicopter infrared characterization, etc., are proposed, as an initial guide and stimulation for future research. In the future, the comprehensive infrared suppression in the 3–5 lm and 8–14 lm bands will doubtfully become the emphasis of helicopter stealth. Multidisciplinary optimization of a complete infrared suppression system deserves further investigation.     

Team effectiveness evaluation and virtual reality scenario mapping model for helicopter emergency rescue

The application of helicopter emergency rescue is becoming increasingly widespread, but the flight crew training in this area is still difficult due to high cost and risk. Nevertheless, with the development of Virtual Reality (VR) technology, virtual simulation has become a significant role in crew training of helicopter rescue. During the implementation of VR-based training, how to transform complex real tasks into VR scenarios and how to evaluate the performance of crew are of great importance. To address these issues, a novel VR-based R-E-A-D (Report, Evaluate, Agree, Do) evaluation model for training is proposed, which is suitable for complex missions with multiple tasks, multiple scenarios, and multiple people. Then, a mapping method of VR scenarios is put forward, which can transform the real tasks into virtual scenarios to serve the virtual simulation training. Finally, an experiment is carried out to verify the feasibility of the evaluation method and virtual scenario mapping method.     

Efficient prediction of ground noise from helicopters and parametric studies based on acoustic mapping

Based on the acoustic mapping, a prediction model for the ground noise radiated from an in-flight helicopter is established. For the enhancement of calculation efficiency, a high-efficiency second-level acoustic radiation model capable of taking the influence of atmosphere absorption on noise into account is first developed by the combination of the point-source idea and the rotor noise radiation characteristics. The comparison between the present model and the direct computation method of noise is done and the high efficiency of the model is validated. Rotor free-wake analysis method and Ffowcs Williams-Hawkings (FW-H) equation are applied to the aerodynamics and noise prediction in the present model. Secondly, a database of noise spheres with the characteristic parameters of advance ratio and tip-path-plane angle is established by the helicopter trim model together with a parametric modeling approach. Furthermore, based on acoustic mapping, a method of rapid simulation for the ground noise radiated from an in-flight helicopter is developed. The noise footprint for AH-1 rotor is then calculated and the influence of some parameters including advance ratio and flight path angle on ground noise is deeply analyzed using the developed model. The results suggest that with the increase of advance ratio and flight path angle, the peak noise levels on the ground first increase and then decrease, in the meantime, the maximum Sound Exposure Level (SEL) noise on the ground shifts toward the advancing side of rotor. Besides, through the analysis of the effects of longitudinal forces on miss-distance and rotor Blade-Vortex Interaction (BVI) noise in descent flight, some meaningful results for reducing the BVI noise on the ground are obtained.     

Trajectory optimization of aerial slung load release for piloted helicopters

This study aims to provide the pilot with optimal control time histories for stabilization of a helicopter after releasing the slung load in aerial delivery missions. A model with 21 degrees of freedom (21-DOF) has been developed and validated for a helicopter slung load system. The control history is generated with detailed procedure based on trajectory optimization. Effects of the objective function formulation on the results are discussed and rules are obtained to assist in the objective function determination. We conclude that the pilot should first decrease and then increase the collective control and adjust the longitudinal control to stabilize the helicopter after the in-hover slung load release. The obtained control history is reasonable and helpful for safety and efficiency improvement. Effects of path constraints and the Flight Control System (FCS) are studied. More stringent path constraints will lead to longer time spent and more controls. Stronger stiffness and weaker damping from the FCS will cause milder control histories but sharper on-axis state histories.