تحقیقات عددی و آزمایشی بر روی خصوصیات حفره ای یک پمپ سانتریفیوژ سرعت بالای دارای القا کننده تیغه شکاف Numerical and experimental investigations on the cavitation characteristics of a high-speed centrifugal pump with a splitter-blade inducer

Centrifugal pumps have been widely applied in different industries, including the petro-chemical, aerospace, and energy industries. With the rapid development of these industries, centrifugal pumps are required to increase in speed. In such cases, cavitation frequently occurs. Equipping an inducer in front of the main centrifugal impeller is an effective method to suppress cavitation [1]. A splitter-blade inducer is a common type and highly contributes to the anti-cavitation performance of pumps. The flow in the splitter-blade inducer is highly turbulent, particularly during cavitation. Several numerical and experimental studies have recently investigated the cavitating flow of a centrifugal pump with a forward-attached inducer. Li et al. [2] and Okita et al. [3] showed that the numerical simulation of the performance of a centrifugal pump with an inducer agrees with experiments conducted on test models. Semenov et al. [4] performed simulations and experiments on the cavitating flow in an inducer. They discovered a new type of cavitation instability in the pump. Pouffary et al. [5] simulated the cavitation behavior of a four-blade rocket engine turbo pump inducer and observed five cavitation patterns. Kim et al. [6] investigated the effects of tip clearance on the anti-cavitation performance and flow characteristics of a turbo pump inducer by using the computational fluid dynamics (CFD) approach. They found that cavitation is generated on the long blade for large tip clearances and that this cavitation obstructs the throat between two adjacent blades. Lee et al. [7] conducted experimental and numerical investigations on the cavitation instability of a two-bladed inducer. They found that the local flow around the cavity closure significantly contributes to the occurrence of asymmetric cavitation. Iga et al. [8] found three types of cavitation surges in an inducer on the basis of oscillation characteristics and flow fields. CamposAmezcua et al. [9] numerically simulated an unsteady cavitating flow and explored local cavitation instabilities, such as alternate blade cavitation and rotating blade cavitation, which can appear in axial inducers. Tamura et al. [10] established a bubble dynamics model to improve simulation quality. Yoshida et al. [11] tested four-bladed inducers with various amounts of cutback to suppress rotating cavitation by applying alternate leading edge cutback. They showed that regions with alternate blade cavitation and asymmetric cavitation become enlarged with an increasing cutback amount. Yoshida et al. [12] investigated the relationship of the uneven cavity length and rotor dynamic force in a cavitating inducer with three blades. They indicated that the shaft vibration because of rotating cavitation is a type of self-excited vibration arising from the coupling of cavitation instability and rotor dynamics. Tani et al. [13] investigated the relationship between the rotating cavitation and flow coefficient of an inducer through numerical simulations. They showed that the flow coefficient influences the onset of cavitation instabilities, such as rotating and asymmetric cavitation. Horiguchi et al. [14] analyzed steady cavitating flow in cascades and found that the stability of the flow affects the camber and blade thickness. Horiguchi et al. [15] found that the three-dimensionality of cavitating flow changes the angle of attack, which is associated with the change in meridional velocity. Kimura et al. [16] researched the vortex structure in the inducer for three types of inlet casing geometries with various flow rates. Their results showed that the development of the tip leakage vortex is dependent on the inlet casing geometry and the flow rate. Hong et al. [17] experimented on a pump with an inducer and found that the inducer exhibits a negligible effect on the head and efficiency of the pump but exerts a significant effect on anti-cavitation performance. Many scholars [18-22] have focused on cavitation and arrived at certain conclusions. However, research on the anticavitation characteristics of a high-speed centrifugal pump with a splitter-blade inducer is insufficient. Moreover, the external characteristics and visualization of internal flow have been rarely experimented. Therefore, investigations on the rotating cavitation characteristics of a centrifugal pump with a splitter-blade inducer are essential. This study aims to numerically and experimentally investigate the rotating cavitation characteristics of a high-speed centrifugal pump with a splitter-blade inducer. The objective of this work is to analyze the cavitation around the splitterblade inducer and the impeller of the centrifugal pump. The rotating cavitation is numerically investigated with the use of a mixture model through the CFD approach. Experiments on the external characteristics of the centrifugal pump are performed on a closed system. The cavitating flow in the inducer is observed by visualization with a high-speed video system. The unsteady behavior of cavitation is discussed by comparison of the numerical results with the experimental data.