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Introduction
Self-priming pump has the advantages of compact structure, convenient operation, long life, and strong self-priming capacity. It has been widely used in agriculture, fire control, municipal, electric power, mining and chemical industry, and other fields.[1]-[4] It is especially suitable for occasions in which equipment needs to be started frequently, the work is mobile, the irrigation is difficult, or the drainage is flowing.
In actual operation, however, the performance of the pump under operating flow rate is not always consistent with the maximum efficiency point. Therefore, the method of trimming the impeller outlet diameter has been widely used to adjust the performance of pump, according to the similarity criterion.[5]-[9] Impeller trim can not only expand the application range of the pump, which is helpful for the standardization and serialization of the pump production, but also stimulate a reasonable match for the maximum efficiency point and the required operating flow rate. Moreover, it can improve the operating efficiency of pumping system and reduce operating costs.[10],[11]
Over the years, scholars have conducted a lot of research on the influence of impeller trim on the performance of the centrifugal pump. Khalifa[12] experimentally investigated the effect of trimming the impeller diameter on the pump performance and vibration levels and compared the changes of the pressure fluctuations inside the pump volute and around the impeller blade exits. Yang et al.[13] studied the effect and influence impeller trimming had on the performance of a single-stage centrifugal pump as turbine using experiment and numerical methods. By numerical simulation method, Wang and Liu[14] obtained the pressure distribution as well as velocity distribution of the internal flow field of the pump with different impeller outlet diameters and found that the impeller trim would lead to a decline of the pump performance.
However, the research into influence of impeller trim on the performance of multi-stage self-priming pump is relatively few. Therefore, the main motive of this article is to study the effects of impeller trim on the performance of a two-stage self-priming centrifugal pump with computational fluid dynamics (CFD) and experiment methods and then analyze the time-domain and frequency-domain characteristics of pressure pulsation and time-domain characteristics of the radial force under different impeller trims.
Determination of impeller trim
Two-stage...