预旋系统功热转换机理与优化设计研究

As a component for supply cooling air to the rotating turbine blade, preswirl system is very interested to the researchers for its potential capability of relative total temperature reduction. The flow in the rotating parts like receiver hole, supply hole and impeller can be divided into two completely different flows. One is the pressure difference driven forced convection flow in axial and radial direction which is related to mass flow rate and flow resistance. Another one is the wheel driven swirl flow in circumferential direction which is the dominant flow in rotating parts and related to swirl ratio and transformation of work and heat. Relative reference frame method is usually used to analyse and calculate the radial and axial flow in rotating parts, while the swirl flow and rotor work are rarely considered. This led to a low efficiency of temperature reduction in preswirl system. Additional new method of analysis and calculation based on absolute reference frame is proposed in this application, with which the swirl flow and rotor work will be considered. With theory analysis, numerical simulation and experimental measurement, the relationship between work consumption and temperature reduction, and the relationship between efficiency of temperature reduction and rotator work and discharge coefficient and swirl ratio of rotating parts, will be proposed and validated. Methods of calculating idea maximum temperature reduction and idea minimum work consumption will be presented also. Based on this, numerical optimization on the impeller, receiver hole and supply hole and experimental validation ware carried out to maximize temperature reduction and minimize work consumption. Systematic method of design and optimization on preswirl system will be established and criterions to evaluate the performance of a preswirl system will be suggested during this research.

预旋系统作为向涡轮转子叶片提供冷却气流的部件系统，因具有显著降低冷气相对总温的潜力而受到关注。系统中接收孔、供气孔和叶轮等转动元件的流动可分解为轴径向流动和周向流动，前者为压差驱动的与流量和流阻相关的强迫对流流动；后者为转动驱动的与旋转比和功热转换相关的旋流流动并在转动件中占有主导地位。学界当前一般采用相对坐标系法对转动件中的轴径向流动进行分析研究，而对旋流流动和功热转换关注很少，导致现有预旋系统的温降效率普遍较低。本项目提出需要补充考虑旋流和作功的绝对坐标系分析方法，并通过理论分析、数值计算和实验测量，探寻和验证预旋系统中温降与功耗的关系，理想最大温降和理想最小功耗的计算方法，以及温降效率和作功效率与转动件流量系数和旋转比等特性参数的关系。在此基础上对接收孔、供气孔和叶轮等转动件进行结构优化改进计算研究和实验验证，增大系统温降和减小功耗，建立预旋系统设计和优化改进的方法体系和评价指标。

项目针对预旋系统的流动温降特性开展了理论分析、数值计算和实验测量研究。基于有功热转换的热力学系统理论推导，获得了预旋系统理想最大温降和理想最小功耗的计算公式，以及实际温降与功耗的数学关系，并定义温降效率作为评价预旋系统性能的主要指标。在所提出的通过减小周向速度差和功耗，提高作功效率来增大温降的理论指导下，对现有预旋系统进行了大量优化改进数值计算工作，提出并研究了叶孔式预旋喷嘴、直接受孔长叶轮和斜接受孔短叶轮等流动温降特性优异的新型预旋结构。设计建造了直径500mm，转速10000rpm的预旋系统流动温降特性旋转实验台，可以模拟发动机状态的流动雷诺数，旋转雷诺数，流动马赫数和旋转马赫，发展了在高速转盘上获得气流温度和压力的测量技术与标定方法。实验验证了无量纲温降与无量纲功耗的线性关系，实验研究了压比、转速和背压对预旋系统流动温降特性的影响，并在设计点对比研究了不同结构在满足供气压力和供气流量条件下的温降效果。实验表明预旋系统的温降随压比的增大而显著增大，随转速的增大先增大后减小，随背压的变化基本不变。最优结构可以在现有结构基础上提高温降效率85%，在发动机状态下降低供气温度20~30K。. 本项目的主要科学意义是解决了基于功热转换和旋流的预旋系统设计理论基础，为预旋系统优化改进设计指明了通过减小功耗，提高作功效率来增大温降的技术途径,定义温降效率作为评价预旋系统设计效果的性能指标；所建立的预旋系统设计和优化改进方法以及所提出的新型结构应用到预旋系统的结构设计中，可以大幅度降低供气温度，显著提高涡轮动叶的可靠性和寿命，具有重要的军事和经济价值。所设计建造的高速旋转实验台和发展的转动参数测量技术，解决了该领域实验研究的技术瓶颈，该技术可以推广到发动机其它旋转部件流动传热问题的实验研究中，具有广阔的应用前景。