滑块和固定叶片组成的可调径流/混流涡轮新构型导流叶片理论构建与实验

The variable radial / mixed flow turbine can improve the matching relationship between the turbocharger and the engine in the full range of working conditions. In application, it is found that the efficiency of turbine decreases significantly when the opening of guide vane is turned off and the turbine is worked in the small flow rate condition. The tip clearance leakage loss of guide vane and the attack angle loss at rotor inlet are the reasons why the efficiency of the turbine decreases significantly. Therefore, it is urgent to increase the efficiency of the turbine in small flow conditions. In this project, a new guide vane of radial / mixed flow turbine consists of slide block and fixed vane is proposed, which is designed to eliminate the tip clearance leakage flow of the guide vane. The flow area of the guide vane is adjusted by moving the slide block on the fixed vane. The parametric design and investigation are conducted based on the new configuration of guide vane, and the design theory of the new configuration of guide vane is constructed. It reveals the exchange mechanisms of mass and momentum between the slide block end flow and the main flow, establishes the mathematical loss model of the slide block end flow. The effects of the tip clearance flow of the slide block / fixed vane on the velocity deficit degree of the guide vane wake, turbulent flow field parameters distributions, and the shedding process of the trailing edge vortex are studied. And an effective organization method of the guide vane trailing edge blowing of the radial / mixed flow turbine is obtained. The research results lay the groundwork for improving the efficiency of turbocharger, and further improving the thermal efficiency of vehicle engine.

导流叶片可调径流/混流涡轮能够改善涡轮增压器和发动机在全工况范围内的匹配关系。实际使用中发现，当关小导流叶片开度，使涡轮工作在小流量工况时，会出现涡轮效率大幅下降的现象。可调导流叶片叶端间隙泄漏损失和转子入口攻角损失是涡轮效率大幅下降的原因，提高小流量下涡轮效率是目前亟待解决的问题。为此提出了一种由滑块和固定叶片组成的可调径流/混流涡轮新构型导流叶片，旨在消除叶端间隙泄漏流动。通过滑块在固定叶片上的移动实现导流叶片流通面积的调节。针对新构型导流叶片开展参数化设计研究工作，构建新构型导流叶片的设计理论。揭示滑块端部流动与主流之间的质量动量交换机制，建立滑块端部流动损失数学模型。发现滑块/固定叶片间隙喷流影响导流叶片尾迹速度亏损程度、湍流场参数分布和尾缘涡脱落过程的规律，获得径流/混流涡轮导流叶片尾缘喷流的有效组织方法。研究结果为提高涡轮增压器的效率和车用发动机热效率奠定理论基础。

导流叶片可调径流/混流涡轮能够改善涡轮增压器和发动机在全工况范围内的匹配关系，近些年来被广泛地应用和研究。实际使用中发现，当关小导流叶片开度，使涡轮工作在小流量工况时，会出现涡轮效率大幅下降的现象。可调导流叶片叶端间隙泄漏损失和转子入口攻角损失是涡轮效率大幅下降的原因，提高小流量下涡轮效率是目前亟待解决的问题。已有关于可调涡轮低端工况下性能改善和激波弱化两个方面的研究相对较少，对新构型导叶设计和研究基本处于空白。.本项目研究了新构型导叶对可调涡轮全局性能的影响，主要研究内容和成果如下：. (1) 针对导叶间隙泄漏和尾缘激波两个影响涡轮性能和转子可靠性的负面因素，设计了一种前部转动式导叶。将原始模型和前部转动式模型进行了定常/非定常数值计算，对比了两种模型在10%，40%和80%三个代表性开度下的性能以及在40%开度下涡轮内部非定常流动特性。结果表明在10%开度下，前部转动式导叶可提高涡轮效率达8%，同时通过转静距离的合理设计，导叶尾缘激波被成功抑制。然而，由于前部转动式导叶固有的几何特征，使其在大于80%开度后效率降低，因此前部转动式导叶的使用是有局限性的。同时针对导叶间隙泄漏流和导叶尾缘激波对下游转子叶片的气动干涉做出了对比分析。.(2) 打破传统的可调涡轮导叶结构与调节方式，创新性地提出并设计了一种分体滑动式导叶来提高可调涡轮全局性能，同时削弱导叶尾缘激波强度。对设计的分体滑动式导叶与原始叶型在10%，40%和100%三个开度下进行了数值研究，分析了装配分体滑动式导叶的可调涡轮性能以及内部非定常流动特征。结果表明分体滑动式导叶能够在全工况范围内实现可调涡轮性能的提升。在10%导叶开度下，分体滑动式导叶间隙泄漏流量降低了约65%，可调涡轮的峰值效率比原始模型提高了10%。在100%导叶开度下，分体滑动式导叶在满足排气流量的前提下仍可提高涡轮1%的峰值效率，并保持其它速比点效率不降低。同时，分体滑动式导叶有效地弱化了作用于转子前缘的导叶尾缘激波强度。