轴对称喷管与圆转方喷管冷却换热特性的比较

为了解和比较轴对称喷管与圆转方喷管不同的再生冷却换热特性,分别对轴对称喷管(推力室)与圆转方喷管(推力室)建立计算模型,通过数值模拟的方法重点研究和比较了轴对称喷管与圆转方喷管的流场、壁面热流密度和温度分布、冷却剂温升和冷却通道压降等换热特性.计算结果表明:圆转方喷管由于型面不连续,在转方位置后壁面出现了温度和热流密度的峰值,从而导致沿周向壁面温度和热流密度的分布也不均匀.      

层板发汗冷却在液体火箭发动机中的应用与发展综述

较系统地介绍了应用于液体火箭发动机推力室冷却的层板技术,指出了层板发汗冷却的技术优势。介绍了一内壁全部由层板构成的液体火箭发动机推力室结构及其层板发汗冷却单元的设计和加工工艺问题。总结了国内外关于层板发汗在火箭推力室冷却方面的研究进展,并简要论述了其应用前景。     

Efficient computation of energy release rates for delaminated beam structures

The often encountered problem of mode partitioning for delaminated, isotropic beam structures is addressed. For the sake of efficiency, solutions that do not require complex continuum solutions – in practise mostly obtained by the finite element method – are examined. Three approaches that meet the postulated efficiency are reviewed and compared. While one method fits consistently into the concept of linear-elastic fracture mechanics, the remaining two deduce mode partitioning hypotheses solely from kinematic quantities of beam theory. The results obtained through these hypotheses are then compared to continuum-based solutions. The latter are generated by the finite element method and are validated by analytical solutions as applicable. Furthermore, mode partitioning solutions for beams, loaded in transverse shear, are given with excellent accuracy. Finally, the conditions for which the different methods comply with or substantially deviate from each other are discussed.     

平面扇形可倾瓦推力轴承性能的研究

可倾瓦推力轴承的最佳支承位置决定了该轴承具有最佳的性能。为了准确确定平面扇形可倾瓦推力轴承的最佳支点位置,本文分析了离心力效应,提出了何时考虑离心力效应的判据和出现空穴现象的判据,较系统地给出了处于最佳支点位置的平面扇形可倾瓦推力轴承的性能计算线图。     

脉冲爆震发动机(PDE)引射增推装置试验

PDE设计了两种结构的排气引射增推装置,通过对两种结构排气引射增推装置的试验对比,研究了排气引射增推装置对PDE推力贡献,试验结果表明在合理的结构设计下,采用排气引射增推装置可使PDE平均推力增加50%左右。理论分析了排气引射增推装置的工作机理,及不同结构参数对PDE排气引射增推装置的影响,为PDE排气引射增推装置优化设计提供了理论和试验依据。      

Performance analysis of variable speed tail rotors with Gurney flaps

Gurney Flaps (GFs) are used for improving the performance of variable speed tail rotors. A validated analytical helicopter model able to predict the main and tail rotor power is utilized. The fixed height GF has substantially small influence on the tail rotor power in hover and low to medium speed forward flight, and can obtain significant power reduction in high speed flight. This ability can be enhanced by decreasing the tail rotor speed. With the deployment of GF, the collective pitch of the tail rotor decreases, and the maximum tail rotor thrust increases. The GF can compensate the reduction of the maximum thrust by the decrease in the tail rotor speed. The GF with a height of 5% of the chord length can almost remedy 50% of the thrust reduction introduced by decreasing 10% of the tail rotor speed. With the increase of GF height, the maximum thrust generated by the tail rotor increases. The GF with larger height can cause the increase in the tail rotor power in hover and low to medium speed flight. The retractable GF can obtain more power savings than the fixed height GF. However, the benefit is substantially small even in high speed flight. Considering the side effects introduced by the active GF, the fixed height GF may be more preferable. The mechanism for the retractable GF to generate more tail rotor thrust is to increase the lift in advancing side due to the higher dynamic pressure.     

基于被动二次流的射流偏转比例控制

射流偏转比例控制一直是流体式推力矢量(FTV)技术所追求的目标之一。本文研制了一种二元流体式推力矢量喷管,采用能量消耗极小的被动二次流与Conada壁面相结合的方式对低速主射流进行矢量偏转控制,通过改变喷管控制缝入口面积实现了主射流偏转的连续比例控制。对低速主射流两侧控制缝压力和射流偏转角进行测量,获得了主射流偏转角随两侧控制缝压力差系数变化的控制规律曲线。结果表明:低速主射流最大偏转角达到19°,在偏转范围内控制曲线分为敏感区和迟钝区。敏感区的控制曲线近似线性,斜率较大,范围约为±15°;而迟钝区的控制曲线斜率较小,在两侧15°~19°的范围内。该结果证实了主射流两侧的压力差是造成其偏转的直接原因。     

Robust control for constant thrust rendezvous under thrust failure

A robust constant thrust rendezvous approach under thrust failure is proposed based on the relative motion dynamic model. Firstly, the design problem is cast into a convex optimization problem by introducing a Lyapunov function subject to linear matrix inequalities. Secondly, the robust controllers satisfying the requirements can be designed by solving this optimization problem.Then, a new algorithm of constant thrust fitting is proposed through the impulse compensation and the fuel consumption under the theoretical continuous thrust and the actual constant thrust is calculated and compared by using the method proposed in this paper. Finally, the proposed method having the advantage of saving fuel is proved and the actual constant thrust switch control laws are obtained through the isochronous interpolation method, meanwhile, an illustrative example is provided to show the effectiveness of the proposed control design method.     

基于SysML的反推力系统安全性分析

通过应用系统工程建模工具SysML(系统建模语言),对反推力系统的使用场景进行建模,分别建立起反推力系统的用例图和顺序图模型.在使用场景模型的基础上,进一步应用HAZOP(危险和可操作性)分析方法对使用场景进行危险分析,得到了反推力系统在使用中可能存在的危险状态,并提出了相应的安全性要求.此方法应用表明,综合SysML...     

航空发动机室内台架推力测量修正方法研究

为解决缺少标准发动机而不能对试车台进行定期校准来确定试车台推力修正值的问题,通过数据统计分析方法,得到台架的发动机推力修正值;通过台架气动流场参数测试,计算出气动冲量、喷口负压和迎风阻力等对发动机推力的影响,并根据验证统计数据,分析了推力修正值的合理性。