Kiyoshi Minemura

Three-Dimensional Calculation of Air-Water Two-Phase Flow in Centrifugal Pump Impeller Based on a Bubbly Flow Model

To predict the behavior of gas-liquid two-phase flows in a centrifugal pump impeller, a three-dimensional numerical method is proposed on the basis of a bubbly flow model. Under the assumption of homogeneous bubbly flow entraining fine bubbles, the equation of motion of the mixture is represented by that of liquid-phase and the liquid velocity is expressed as a potential for a quasi-harmonic equation. This equation is solved with a finite element method to obtain the velocities, and the equation of motion of an air bubble is integrated numerically in the flow field to obtain the void fraction. These calculations are iterated to obtain a converged solution. The method has been applied to a radial-flow pump, and the results obtained have been confirmed by experiments within the range of bubbly flow regime.

Prediction of Air-Water Two-Phase Flow Performance of a Centrifugal Pump Based on One-Dimensional Two-Fluid Model

To predict the performance of centrifugal pumps under air-water two-phase flow conditions, a consistent one-dimensional two-fluid model with fluid viscosity and air-phase compressibility in a rotating impeller is proposed by considering energy changes in the transitional flow from the rotating impeller to the stationary volute casing. The two-fluid model is numerically solved for the case of a radial-flow pump after various constitutive equations are applied

Measurement of erosion due to particle impingement and numerical prediction of wear in pump casing

Erosion damage of wear-resistant materials due to sand particle impingement is measured and correlated based on Bitters erosion model to clarify the effects of particle impinging velocity and angle, particle size and concentration on the wear. Using the empirical formula for the correlation and calculating impinging velocities of sand particles on a casing wall of a pump, successive erosion of the wall is numerically calculated to demonstrate the viability of the prediction method proposed in our previous study.

Simultaneous measuring method for both volumetric flow rates of air-water mixture using a turbine flowmeter

A turbine flowmeter is employed in this study in connection with offshore oil field development, in order to measure simultaneously both the volumetric flow rates of air-water two-phase mixture. Though a conventional turbine flowmeter is generally used to measure the single-phase volumetric flow rate by obtaining the rotational rotor speed, the method proposed additionally reads the pressure drop across the meter. After the pressure drop and rotor speed measured are correlated as functions of the volumetric flow ratio of the air to the whole fluid and the total volumetric flow rate, both the flow rates are iteratively evaluated with the functions on the premise that the liquid density is known. The evaluated flow rates are confirmed to have adequate accuracy, and thus the applicability of the method to oil fields.

Effects of Entrained Air on the Performance of a Horizontal Axial-Flow Pump

The performance of an axial-flow pump was investigated under air-admitting conditions and the results were compared with those obtained for radial-flow pumps investigated in our previous studies. For the axial-flow pump we measured head as a function of impeller speed, liquid flow rate, and air void fraction. Flow visualization was performed and we correlated air bubble size as a function of Weber number based on mean impeller velocity. Overall flow patterns and the locations of air coalesence within the impeller were observed and diagrammed. These data contribute to earlier data obtained by ourselves and others to develop analytical models to predict pump performance degradation due to air admittance.

Numerical prediction of turbulent bubbly two‐phase flow in a rotating complicated duct

A fully three-dimensional numerical procedure based on the two-fluid model in a general curvilinear co-ordinate system is proposed for the prediction of developing turbulent bubbly two-phase flow in a rotating complicated duct. A Coriolis-modified turbulence model is extended to two-phase flows to account for the rotational effect on the lateral phase distribution. The governing equations are solved using a finite volume technique with a non-staggered variable arrangement

Prediction of pump performance under air-water two-phase flow based on a bubbly flow model

This paper is concerned with the determination of the performance change in centrifugal pumps operating under two-phase flow conditions using the velocities and void fractions calculated under the assumption of an inviscid bubbly flow with slippage between the two phases. The estimated changes in the theoretical head are confirmed with experiments within the range of bubbly flow regime.

Calculation of the Three-Dimensional Behaviour of Spherical Solid Particles Entrained in a Radial-Flow Impeller Pump

Equations of motion of solid particles in a pump impeller having a low specific speed were solved numerically in the flow field obtained with assumptions of an inviscid and incompressible three-dimensional potential flow, and general movements of solid particles in the pump were clarified. Trajectories of the sand particles and manganese ores, with diameters ranging from 1 to 5 mm, were obtained for different flow capacities. The positions and velocities with which the particles impact on the boundary surface of the pump were also discussed in order to estimate erosion damage in pumps.

Experimental investigations on bubbly flows in a straight channel rotated around an axis perpendicular to the channel

Abstract This paper describes experimental investigations on the behavior of an air-water two-phase mixture in a horizontal, radial-flow and square-sectioned straight channel, which rotates around an axis perpendicular to the channel. The hydraulic loss of head and the distributions of pressures and void fractions in the channel were measured mainly in a bubbly flow regime, and the effects of the rotating speed of the channel and the flow rate of water on the loss were discussed in relation to the inlet void fraction. When the rotating speed is increased or the flow rate of water is decreased, a predominant region of high void fractions appearing on the downstream negative side tends to expand upstream as the Rossby number is increased. An almost imperceptible pressure rise in the radial direction of this region causes an excessive increase in the hydraulic loss.

Distributions of Velocities and Void Fractions in a Radial-Flow Pump Impeller Handling Air- Water Two-Phase Mixtures

To clarify the performance changes of a centrifugal-pump under gas-liquid two-phase flow conditions, distributions of velocities and void fractions in and after a radial-flow pump impeller as well as the pump performance under air admitting conditions were measured. The distributions of the void fraction obtained are extremely uneven and much affected by the admitted air quantity, while those of the flow velocities are also changed corresponding to the air quantity, showing close relations of the changes in pump performance with those in the internal flow phenomena of the mixtures.