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991.
为了研究弯曲叶片对涡轮叶片非定常气动力的控制作用,采用非定常数值模拟方法对高压涡轮两级的内部流场进行了计算,研究了第一级静叶采用正弯叶片时,汽轮机涡轮叶片非定常气动力和非定常压力场的变化.结果表明,采用弯曲静叶的设计方法,通过改变静叶出口处径向压力梯度和涡量分布,能够有效抑制动静叶片表面气动力的非定常脉动作用.但弯叶片给非定常压力场带来的改善是局部的,其对叶片中间截面改善最为显著.从整体上来看,正弯曲的静叶设计对于减小非定常流场中的压力脉动是有益的. 相似文献
992.
为探究涡轮高效设计技术,从低维优化层面出发,提出了一种基于粒子群优化算法的多级低压涡轮一维设计和优化方法.该方法以涡轮效率为目标,通过建立涡轮子午流道形式以及气动特性等约束条件将涡轮一维设计转化成包含约束限制的极大值优化问题.在验证粒子群算法优化性能的基础上发展了多级低压涡轮一维气动优化设计程序,该程序通过优化地选取涡轮各级的多个设计变量,有效地生成满足多个约束条件的级最佳速度三角形以及最佳初步子午流道形式.利用该程序完成了原型低压涡轮的优化改型工作,三维数值模拟结果表明,优化改型方案在设计点和非设计点的气动性能均获得了不同程度的改善. 相似文献
993.
994.
针对波音737CL飞机模拟式座舱压力控制系统部件老龄化问题,提出部件预防性维修措施.减少因部件内部元器件老化造成的重复性故障,供业内同行参考。 相似文献
995.
多级低压涡轮内部非定常流场扰动分析 总被引:1,自引:0,他引:1
采用三维数值模拟方法,对带有过渡段和后机匣支板的低压涡轮进行全环非定常数值模拟,分析了各个叶片排流场中存在的非定常扰动及扰动源,研究了低压涡轮第二级中存在的多种扰动源叠加现象,并对流场中的静压波动进行了频谱分析。结果显示,过渡段的二次流对低压涡轮内部流场存在明显扰动,并向下游传播至涡轮出口。第二级动叶中,上游导叶通过频率与过渡段二次流自身脉动频率产生叠加,形成的新扰动频率为两者产生的差频。采用全环非定常数值模拟预测多级低压涡轮内部流动中存在的各种扰动频率及其相互叠加很有必要。 相似文献
996.
《中国航空学报》2020,33(1):16-30
The piston pump is the key power component in the civil aircraft hydraulic system, and the most common pump used in the aviation field is the pressure compensated variable displacement type. In this review paper, a basic introduction to the civil aircraft piston pump is presented, including the classification, structure, working principle, design features, and achievements by some research groups. Then, the future directions of the aircraft pump are reported from various perspectives. Further, the critical technologies are analyzed and summarized in detail from six thrust areas: friction couples, noise reduction, inlet boost, thermal management, fault diagnosis and health management, and mechanical seal. Finally, the challenges and limitations of the research on the aircraft pump are discussed to provide valuable insight for future scholars. 相似文献
997.
The acquisition of survey knowledge for local and global landmark configurations under time pressure
Sascha Credé Tyler Thrash Christoph Hölscher Sara Irina Fabrikant 《Spatial Cognition & Computation》2019,19(3):190-219
The influence of stress states on cognition is widely recognized. However, the manner in which stress affects survey knowledge acquisition is still unresolved. For the present study, we investigated whether survey knowledge acquisition during a stressful task (i.e., under time pressure) is more accurate for the mental representation of global or local landmarks. Participants navigated through virtual cities with a navigation aid and explicit learning instructions for different landmark configurations. Participants’ judgments of relative direction (JRDs) suggest that global landmark configurations were not represented more accurately than local landmark configurations and that survey knowledge acquisition was not impaired under time pressure. In contrast to prior findings, our results indicate the limitations of the utility of global landmarks for spatial knowledge acquisition. 相似文献
998.
C.J. Rodriguez-Solano U. HugentoblerP. Steigenberger 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
One of the major uncertainty sources affecting Global Positioning System (GPS) satellite orbits is the direct solar radiation pressure. In this paper a new model for the solar radiation pressure on GPS satellites is presented that is based on a box-wing satellite model, and assumes nominal attitude. The box-wing model is based on the physical interaction between solar radiation and satellite surfaces, and can be adjusted to fit the GPS tracking data. 相似文献
999.
1000.
For a typical pressurized system with a novel dual-stage gas pressure reducing regulator, a system model is established with modular models of various typical components. The simulation study on the whole working period shows that the general trends and magnitudes of simulation curves are in agreement with experimental measured curves. As the key component in the pressurized system, the regulator is studied by a series of numerical simulations to reveal the influences of various structure parameters on its stability. Furthermore, the variable ranges which can guarantee the stability of regulator and system are obtained to provide guidance for design. The modeling and analysis approach can be applied to other systems and components. 相似文献