Modelling of cavitation in centrifugal pumps

Cavitation, which occurs mostly due to the operation in inappropriate conditions, is the most important problem that limits the service life of centrifugal pumps. However, some centrifugal pumps are low-resistive to cavitation and are exposed to cavitation during their operation. In this study, cavitation performance enhancement of a commercial centrifugal pump is achieved via computational fluid Dynamics (CFD). Besides, the effect of inlet blade angle and wrap angle on cavitation performance of the centrifugal pump are investigated in detail. Two phase CFD study is conducted for both hub and shroud aforementioned angles so, the effect of hub and shroud values of these angles are investigated separately. The study consists of five chapters. In the first chapter, the cavitation phenomenon is explained and a detailed literature review about the topic is provided. In the second chapter numerical modelling of the pump is conducted after providing 3D sketches. After the required modification on the impeller sketch, two phase CFD study is carried out and it is seen that the results are good agreement with the experimental data. One of the main objectives of the study is to investigate the effect of inlet blade angle and wrap angle on cavitation performance of the pump. For this purpose, the pump is parameterized with Ansys BladeGen module by using main pump design parameters such as head, discharge, rotational speed, blade angles and wrap angle. Thus, instead of using a 3D CAD programme for each design, the value of desired parameter is set as data input and the flow volume is created automatically. According to the two phase CFD studies results of the parameterized pump are extremely in good agreement with the numerical pump results in previous section. In the fourth chapter the effect of inlet blade angle and wrap angle both at hub and shroud are investigated. The effect of hub and shroud inlet blade and Wrap angles are investigated separately and simultaneously. Afterwards, the results of best design are compared with the parameterized pump. Finally, a multi parameter optimization is conducted with Taguchi method. According to the Taguchi design of experiment, cavitation tests are conducted via CFD and the best design is obtained according to the signal noise ratios. The results and discussion about the study is given in the sixth chapter.