Numerical and Experimental Investigations of the Cavitation Structure in Inducer

在以前的项目中，可以证明，只要按照既定的设计程序来规定，为了达到规定的压力升高，诱导器就不能沿轴向设计。因此，一个比既定设计程序所规定的更短的诱导器是否能够完全或充分地减少轴向的空化，从而使下一个叶轮的功能不受影响。这个问题到目前为止还没有在公开文献中被讨论过。基本上，问题是诱导器的轴向尺寸必须有多长才能完全发挥其功能(增加压力，减少空化)。在本项目中，将制定标准，使设计具有足够轴向长度的诱导器成为可能。在公开的科学文献中表明，诱导器的前缘被扫过会导致NPSH行为的改善。这一点可以从前一个项目的结果中得到证实。一个悬而未决的问题是，横扫领先优势为何会导致不良资产救助行为的改善。这个问题涉及到建立最佳后掠前缘准则的要求。在本项目中，将研究前缘区域的压力分布，以找出为什么后掠前缘具有更好的NPSH行为。最后，公开的文献没有给出诱导器和叶轮之间的相互作用的答案。引进器产生一个旋流，该旋流施加在主流方向上跟随叶轮的进水侧。另一方面，叶轮影响着诱导轮的涡流。在本项目中，这一问题是通过测量和CFD模拟来研究在不受叶轮影响的情况下诱导器的旋流。之后，考虑了叶轮的影响。在最后一步中，制造出与诱导器配合良好的改进型叶轮。

In the previous project it could be demonstrated that an inducer must not be designed in the axial direction as long as it is prescribed by the established design procedures in order to reach a prescribed pressure rise. Therefore the question arises whether an inducer, which is shorter designed than the established design procedures prescribe, is able to reduce the cavitation completely or sufficiently in axial direction, respectively, so that the following impeller is not affected in its function. This question has not been treated in the open literature until now. Basically, the question arises how long the axial dimension of an inducer must be to fulfil its function (increase of pressure, reduction of cavitation) completely. In the present project criterions are to be developed making it possible to design an inducer with sufficient axial length. In the open scientific literature it is shown that a swept leading edge of an inducer leads to an improvement of the NPSH-behaviour. This could be confirmed by the results of the previous project. It is an open question why a swept leading edge leads to an improved NPSH-behaviour. This question is related to the request to develop criterions of an optimal swept leading edge. In the present project the pressure distribution is to be investigated in the leading edge region in order to find out why a swept leading edges processes a better NPSH-behaviour. Finally, the open literature does not give an answer of the interaction between inducer and impeller. The inducer produced a swirl which is imposed on the inflow side of the in main stream direction following impeller. On the other hand the impeller influences the swirl of the inducer. In the present project this problem is to be treated by investigating the swirl of the inducer without influence of the impeller by measurements and CFD-simulation. After that the influence of the impeller is taken into account. In a last step a modified impeller is produced which works well together with the inducer.