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101.
为获得新型圆周缝结构救生伞的充气性能,文章采用任意拉格朗日欧拉流固耦合方法对该救生伞进行了充气过程的数值模拟,用空投试验结果验证了该数值方法的可行性。数值结果得到了绕伞衣流场、伞衣外形、运动的动态信息,对数值结果的分析发现初始充气阶段后期流场对上部伞衣影响很大,为充气过程中上部伞衣的控制提供了依据,但是初始充气期救生伞的摆动角度小于充满期。对于结构透气量不对称设计的伞衣,不对称充气是绝对的,圆周缝会首先在结构透气量少的部位张开。结果表明,对不同的圆周缝节点设计不同的开缝力将有助于保持良好的对称充气状态,改变开缝力的设计参数将会改变圆周缝的开缝时间及圆周缝完全张开所需的时长,将达到更好的减载效果。研究结果对圆周缝型降落伞的优化设计有一定的参考作用。 相似文献
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Gray bootstrap method for estimating frequency-varying random vibration signals with small samples 总被引:2,自引:0,他引:2
During environment testing, the estimation of random vibration signals (RVS) is an important technique for the airborne platform safety and reliability. However, the available meth- ods including extreme value envelope method (EVEM), statistical tolerances method (STM) and improved statistical tolerance method (ISTM) require large samples and typical probability distri- bution. Moreover, the frequency-varying characteristic of RVS is usually not taken into account. Gray bootstrap method (GBM) is proposed to solve the problem of estimating frequency-varying RVS with small samples. Firstly, the estimated indexes are obtained including the estimated inter- val, the estimated uncertainty, the estimated value, the estimated error and estimated reliability. In addition, GBM is applied to estimating the single flight testing of certain aircraft. At last, in order to evaluate the estimated performance, GBM is compared with bootstrap method (BM) and gray method (GM) in testing analysis. The result shows that GBM has superiority for estimating dynamic signals with small samples and estimated reliability is proved to be 100% at the given confidence level. 相似文献
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The effectiveness of grinding fluid supply has a crucial impact on grinding quality and efficiency in high speed grinding. In order to improve the cooling and lubrication, through in-depth research of self-inhaling internal cooling method and intermittent grinding mechanism, a new spray cooling method used in high speed grinding is proposed. By referring to the structure of bowl- shaped dispersion disk, the grinding wheel matrix with atomization ability is designed; through studying heat transfer of droplet collision and the influence of micro-groove on the boiling heat transfer, grinding segment with micro-groove is designed to enhance the heat flux of coolant and achieve maximum heat transfer between droplets and grinding contact zone. High-speed grinding experiments on GH4169 with the developed grinding wheel are carried out. The results show that with the micro-groove grinding wheel just 5.4% of pump outlet flow rate and 0.5% of spindle energy is needed to reduce the grinding temperature to 200℃, which means the developed grinding wheel makes cooling high efficient and low energy consuming. 相似文献
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The main goal of this paper is to study the characteristics of regression rate of solid grain during thrust regulation process. For this purpose, an unsteady numerical model of regression rate is established. Gas–solid coupling is considered between the solid grain surface and combustion gas.Dynamic mesh is used to simulate the regression process of the solid fuel surface. Based on this model, numerical simulations on a H2O2/HTPB(hydroxyl-terminated polybutadiene) hybrid motor have been performed in the flow control process. The simulation results show that under the step change of the oxidizer mass flow rate condition, the regression rate cannot reach a stable value instantly because the flow field requires a short time period to adjust. The regression rate increases with the linear gain of oxidizer mass flow rate, and has a higher slope than the relative inlet function of oxidizer flow rate. A shorter regulation time can cause a higher regression rate during regulation process. The results also show that transient calculation can better simulate the instantaneous regression rate in the operation process. 相似文献
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谭永刚张迎春 《民用飞机设计与研究》2014,(4):58-60
阐述并解析了运输类飞机适航规章对结构制造方法的内在要求,介绍了复合材料工艺适航审查的流程、验证级别、验证所需考虑的要素,以及为表明对适航规章的符合性,复合材料工艺规范应包含的必要组成部分以及各部分的编制要求。 相似文献
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在定位分析航空维修工程专业所面向的岗位、工作任务以及完成任务所要求具备的职业能力的基础上,研究运用基于工作过程的实践教学方法进行教学内容和方法设计的改革,构建并优化了案例库。实践表明,该教学改革可充分发挥学生的主体作用,提高了学生实践技能,增强了学生的工程意识。 相似文献