Numerical and Experimental Investigations of the Cavitation Structure in Inducer

在之前的项目中，可以证明，只要按照既定的设计程序规定，为了达到规定的压力上升，就不能在轴向设计诱导器。因此，问题出现了，设计比既定设计程序规定的更短的诱导器是否能够完全或充分地减少轴向空化，从而使后面的叶轮的功能不受影响。到目前为止，这个问题还没有在公开文献中得到处理。基本上，问题出现了多长轴向尺寸的诱导必须完全履行其职能（增加压力，减少空化）。在目前的项目中，将制定一些准则，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，诱导剂的扫掠前缘导致npsh行为的改善。这一点可以从之前项目的结果中得到证实。为什么掠前缘会导致npsh行为的改善，这是一个悬而未决的问题。这个问题与制定最佳后掠前缘标准的要求有关。在本项目中，将研究前缘区域的压力分布，以找出为什么掠前缘处理更好的npsh行为。最后，公开文献没有给出诱导轮与叶轮相互作用的答案。诱导器产生了一个旋流，该旋流施加在主流方向的流入侧。另一方面，叶轮对诱导轮的旋流有影响。在本项目中，我们将通过测量和cfd模拟来研究不受叶轮影响的诱导轮的旋流。然后考虑叶轮的影响。在最后一步中，生产了一个改进的叶轮，它与诱导器一起很好地工作。

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.