Pressure fluctuation and flow pattern of a mixed-flow pump with different blade tip clearances under cavitation condition

Abstract

Cavitation phenomenon has strong transient characteristics and is highly influenced by geometric structure. In this study, the cavitation performance with influence of blade tip clearance for a mixed-flow pump is studied using the renormalization group (RNG) k-e turbulence model and the Zwart-Gerber-Belamri cavitation model. The dominant frequency and maximum amplitude values at non-cavitation condition and different cavitation conditions are compared and associated with flow field features. The results show that the dominant frequency value under incipient cavitation and critical cavitation is 3.2f i and when the cavitation is severe, the frequency value changes to 3.5f i . Then, the influence of tip clearance width on cavitation performance of the mixed-flow pump is also discussed. The results show that the increase in tip clearance will significantly aggravate the performance drop of the pump under cavitation conditions. The critical net positive suction head value increases in 4.79% of the value under no-tip clearance condition. At the same time, by the inner flow field observation and analysis, the morphological of cavitation bubbles is also changed, and the cavitation bubbles tend to attach to the blade suction side and the attachment length increases as the tip clearance increases.

Numerical study on the cavitation phenomenon for the head drop and unsteady bubble patterns with a difference in the incidence angle of a mixed-flow pump

“…3 In contrast, the cloud cavity is eventually separated at the impeller shroud along the streamwise direction. [4][5][6][7] The cloud cavity is complex owing to the flow rates and blade geometries. [8][9][10] Among the two representative classes of the cavity, this study is focused on the former, sheet cavity.…”

Unsteady Flow and Structural Behaviors of Centrifugal Pump under Cavitation Conditions

“…To compensate for the shortage of experimental methods, computational fluid dynamics (CFD) methods were used, and its predictions of cavitation behaviors in centrifugal pumps revealed interesting results. During the simulation, the Reynolds-averaged Navier-Stokes (RANS) equations coupled with a homogeneous mixture of cavitation models were applied to obtain a clearer picture of transient cavitation flow structures and pressure pulsations in both the rotating part (impeller) and stationary part (volute or vane diffusor) [7][8][9][10][11]. In addition, a number of studies focused primarily on the structural behaviors of pumps under cavitation conditions.…”

A Review of Tip Clearance in Propeller, Pump and Turbine

“…Cavitation also influences the characteristics of pressure fluctuations. Xu [73] found that the maximum magnitude of pressure fluctuation increases with the deteriorating cavitation induced by increasing the tip clearance in a mixed-flow pump. characteristics of pressure fluctuations.…”

“…characteristics of pressure fluctuations. Xu [73] found that the maximum magnitude of pressure fluctuation increases with the deteriorating cavitation induced by increasing the tip clearance in a mixed-flow pump. The above analyses illustrate that the influence of tip clearance on pressure fluctuation has various forms in terms of magnitude, frequency, and variation trends for different types of pumps and turbines, and the variation of the impact is due to the complex flow pattern in those divers machineries.…”

“…By contrast, Boulon et al [12] concluded that the decrease in tip clearance can reduce the cavitation-cloud size near the hydrofoil if the tip clearance is below 4 mm. Numerical results for a mixed-flow pump [73] show that increasing the tip-clearance size can increase the TLV strength and the critical-cavitation number, which exacerbates the cavitation (see Table 4 for parameters). NPSHC is the critical net positive suction head.…”