Energy Performance and Flow Patterns of a Mixed-Flow Pump with Different Tip Clearance Sizes

Abstract

Tip clearance between blade end and shroud is inevitable in pump operation and of great importance on pump energy performance and pressure fluctuation. As the tip clearance size increases, the head and efficiency of the mixed flow pump drop accordingly. The simulation results show that the development of a leakage vortex is observed as the tip clearance increases, and the trajectory of this leakage vortex remains in the same direction along the blade suction side for different tip clearances. With the increase in tip clearance size, the intensity of the leakage vortex is enhanced, and the separation between the main leakage vortex and the secondary leakage vortex is also strengthened. The leakage separation angle near the blade tip remains at the same value of 10° for different tip clearance sizes. As for the spectrum analysis, the maximum amplitudes of pressure fluctuations dramatically increase in the impeller when the tip clearance increases from 0.0 mm to 1.0 mm, and the dominant frequencies go from 145 Hz to 184 Hz due to the considerable leakage flow.

Influence of Prewhirl Angle and Axial Distance on Energy Performance and Pressure Fluctuation for a Centrifugal Pump with Inlet Guide Vanes

“…The boundary conditions are set as: the total pressure at pump inlet, the mass flow rate at the pump outlet, and no slip wall at the walls. The methods of frozen-rotor and transient-rotor-stator are applied to couple the rotational and stationary domains for steady and unsteady calculations, respectively [22][23][24]. The relative position between the stable suction pipe and the volute and the rotational impeller remains unchanged in the frozen-rotor method, while it varies according to the angular velocity of the impeller in the transient-rotor-stator method.…”

A Review of Tip Clearance in Propeller, Pump and Turbine

“…Leakage flow through tip clearance interacts with the main flow and results in complex vortex structures and an unstable flow pattern in the tip-clearance region [7], such as cavitation [8] and pressure fluctuation [5,9]. Figure 2 illustrates the tip-leakage vortex (TLV) cavitation of an axial pump at cavitation number (σ) 0.481.…”

“…Machinery Type Performance Change 0-1 mm Mixed-flow pump [5,6] Head drops by 10% at design flow rate; efficiency drops by 4% at design flow rate; pressure fluctuation near blade-trailing edge increases by 20 times; unsymmetrical tip clearance deteriorates cavitation performance and increases radial-force fluctuation.…”

“…As shown in Table 1, tip clearance can induce tip-leakage flow and further influence the energy performance and operation stability of pump and turbine. The head and efficiency can be significantly influenced by the variation of tip clearance [5,6]. Therefore, the appropriate design of tip clearance is necessary to optimize the performance of pumps and turbines.…”

Influence of tip clearance on the performance of a screw axial-flow pump

“…The mechanism of tip clearance flow in impeller machinery has been studied deeply and systemically. [5][6][7][8][9] RL Miorini et al 10 and Wu et al [11][12][13] measured the flow field structure and the turbulent kinetic energy distribution of the leakage vortex in the tip clearance of water-jet propulsion through particle image velocimetry (PIV). The internal flow field and external characteristics of the axial-flow pump impeller with different tip clearances were studied by Zhang et al, 14,15 by means of CFD numerical simulation, PIV, and other test methods.…”