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Article
Publication date: 29 June 2020

Chaoyue Wang, Fujun Wang, Changliang Ye, Benhong Wang and Zhichao Zou

Tip leakage vortex flow (TLV) is a common flow phenomenon in the axial-flow hydraulic machinery. High-efficiency simulation of TLV is still not an easy task because of the…

Abstract

Purpose

Tip leakage vortex flow (TLV) is a common flow phenomenon in the axial-flow hydraulic machinery. High-efficiency simulation of TLV is still not an easy task because of the complex turbulent vortex-cavitation interactions. As an important basis of CFD, turbulence model directly affects the efficient computation of TLV. The purpose of this paper is to evaluate the newly developed MST turbulence model in predicting the TLV flows.

Design/methodology/approach

By using the MST turbulence model and the ZGB cavitation model, numerical simulations of the TLV generated by a NACA0009 hydrofoil were performed under the cavitation-free and cavitation conditions, and the results were compared with the available experimental data.

Findings

The important features of TLV are well captured by the MST-based simulation scheme, and the problem of under-predicting the cavitating TLV tube is well solved. Turbulent viscosity is reasonably adjusted in the TLV core regions, and the LES-like mode is activated, which is beneficial to obtain more turbulent information on the same URANS grids. The requirements of grid size and time step of the MST model are much lower than that of the LES method, thereby weighing a good balance between the simulation accuracy and computation cost.

Originality/value

The MST turbulence model is suitable for the high-efficiency simulation of the TLV flows, which can lay a good foundation for efficient engineering computations of the cavitating TLV in the axial-flow hydraulic machinery.

Details

Engineering Computations, vol. 38 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 19 July 2011

Wen‐Guang Li

A method for optimizing net positive suction head required of axial‐flow pumps has been proposed by the present author, which is based on the two‐dimensional potential…

Abstract

Purpose

A method for optimizing net positive suction head required of axial‐flow pumps has been proposed by the present author, which is based on the two‐dimensional potential flow model and without considering the tip gap effect. The objective of the paper is to confirm if the method is just and feasible for the case of viscous fluid flow in impellers with tip gap.

Design/methodology/approach

A series of steady, three‐dimensional, noncavitating and cavitating, turbulent, incompressible flows of water through two axial‐flow pump impellers were calculated by using CFD code Fluent. The two impellers included a reference one with constant circulation at outlet and an optimized one with variable circulation designed with the author's method and code. In computations, the throttling and unthrottling approaches were used, respectively. Comparison of hydraulic performance, averaged flow variables at the impeller inlet and exit, flow in the tip gap, flow variables on blade surfaces and suction performance between the optimized and reference impellers was made.

Findings

It was confirmed that the optimized impeller has better hydraulic and suction performances. The method for optimizing with variable flow circulation profile along blade span at the outlet to impeller is proper and practical. Additionally, an unstable regime in the head curves of two impellers is presented. In the regime, a stall occurs on the pressure side of the blade and a hysteresis exists, which causes a hysteresis‐loop.

Research limitations/implications

The effect of suction entry on flow is represented approximately by using a free‐vortex and uniform axial velocity. The diffusing component behind the impellers is not taken into account. The unsteadiness of flow is not considered, which would have a connection with stall pattern in an axial‐flow impeller.

Originality/value

The hydraulic and suction performances and flow variables of two axial‐flow pump impellers with tip clearance are obtained successfully with CFD. Stall and hysteresis as well as hysteresis‐loop in head curve are observed by using throttling and unthrottling approaches.

Details

Engineering Computations, vol. 28 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 9 March 2010

Zhengwei Wang, Guangjie Peng, Lingjiu Zhou and Deyi Hu

The pump of the Taipuhe Pump Station, larger flow discharge, lower head, is one of the largest 15° slanted axial‐flow pumps in the world. However, few studies have been…

Abstract

Purpose

The pump of the Taipuhe Pump Station, larger flow discharge, lower head, is one of the largest 15° slanted axial‐flow pumps in the world. However, few studies have been done for the larger slanted axial‐flow pump on safe operation. The purpose of this paper is to analyze the impeller elevation, unsteady flow, hydraulic thrust and the zero‐head flow characteristics of the pump.

Design/methodology/approach

The flow field in and through the pump was analyzed numerically during the initial stages of the pump design process, then the entire flow passage through the pump was analyzed to calculate the hydraulic thrust to prevent damage to the bearings and improve the operating stability. The zero‐head pump flow characteristics were analyzed to ensure that the pump will work reliably at much lower heads.

Findings

The calculated results are in good agreement with experimental data for the pump elevation effects, the performance curve, pressure oscillations, hydraulic thrust and zero‐head performance.

Research limitations/implications

Since it is assumed that there is no gap between blades and shroud, gap cavitations are beyond the scope of the paper.

Originality/value

The paper indicates the slanted axial‐flow pump characteristics including the characteristic curves, pressure fluctuations, hydraulic thrust and radial force for normal operating conditions and zero‐head conditions. It shows how to guarantee the pump safety operating by computational fluid dynamics.

Details

Engineering Computations, vol. 27 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 7 November 2016

Ran Tao, Ruofu Xiao and Fujun Wang

High speed axial flow pumps are widely used in aircraft fuel systems. Conventional axial flow pumps often generate radial secondary flows at partial-load conditions which…

Abstract

Purpose

High speed axial flow pumps are widely used in aircraft fuel systems. Conventional axial flow pumps often generate radial secondary flows at partial-load conditions which influence the flow structure and form a “saddle-shaped” region in the Q-H curve that can destabilize the operation. Thus, the “saddle-shaped” Q-H region must be eliminated. The paper aims to discuss these issues.

Design/methodology/approach

The swept stacking method is often used for radial flow control in turbo-machinery impeller blade design. Hence, this study uses the swept stacking method to design a high speed axial flow pump. The detached eddy simulation method and experiments are used to compare the performance of a swept blade impeller in a high speed axial fuel pump with the original straight blade impeller. Both the pump performance and internal flow characteristics are studied.

Findings

The results show separation vortices in the impeller with the straight blade design at partial-load conditions that are driven by the rotating centrifugal force to gather near the shroud. The swept geometry provides an extra force which is opposite to the rotating centrifugal force that creates a new radial equilibrium which turns the flow back towards the middle of the blade which eliminates the vortices and the “saddle-shaped” Q-H region. The swept blade impeller also improves the critical cavitation performance. Analysis of the pressure pulsations shows that the swept blade design does not affect the stability.

Originality/value

This study is the initial application of swept blades for axial flow liquid pumps. The results show how the swept stacking changes the radial equilibrium of the high density, high viscosity flow and the effects on the mass transfer and pressure pulsations. The swept blade effectively improves the operating stability of high speed fuel pumps.

Details

Engineering Computations, vol. 33 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 1 December 1957

The breakdown of laminar flow in the clearance space of a journal is considered, and the point of transition is considered in relation to experiments carried out with…

Abstract

The breakdown of laminar flow in the clearance space of a journal is considered, and the point of transition is considered in relation to experiments carried out with ‘bearings’ of large clearance. Experiments involving flow visualization with very large clearance ratios of 0.05 to 0.3 show that the laminar regime gives way to cellular or ring vertices at the critical Reynolds number predicted by G. I. Taylor for concentric cylinders even in the presence of an axial flow and at a rather higher Reynolds number in the case of eccentric cylinders. The effect of the transition on the axial flow between the cylinders is small. The critical speed for transition as deduced by Taylor, is little affected by moderate axial flows and is increased by eccentricity. The effect of critical condition on the axial‐flow characteristics of the bearing system appears to be negligible, again for moderate axial flows. Assuming that the results can be extrapolated to clearances applicable to bearing operation, the main conclusion of this paper is that the breakdown of laminar flow, which is a practical possibility in very high‐speed bearings, is delayed by eccentric operation.

Details

Industrial Lubrication and Tribology, vol. 9 no. 12
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 5 March 2018

Wei Li, Leilei Ji, Weidong Shi, Ling Zhou, Xiaoping Jiang and Yang Zhang

The purpose of this paper is to experimentally and numerically study the transient hydraulic impact and overall performance during startup accelerating process of mixed-flow pump.

Abstract

Purpose

The purpose of this paper is to experimentally and numerically study the transient hydraulic impact and overall performance during startup accelerating process of mixed-flow pump.

Design/methodology/approach

In this study, the impeller rotor vibration characteristics during the starting period under the action of fluid–structure interaction was investigated, which is based on the bidirectional synchronization cooperative solving method for the flow field and impeller structural response of the mixed-flow pump. Experimental transient external characteristic and the transient dimensionless head results were compared with the numerical calculation results, to validate the accuracy of numerical calculation method. Besides, the deformation and dynamic stress distribution of the blade under the stable rotating speed and accelerating condition were studied based on the bidirectional fluid–structure interaction.

Findings

The results show that the combined action of complex hydrodynamic environment and impeller centrifugal force in the startup accelerating process makes the deformation and dynamic stress of blade have the rising trend of reciprocating oscillation. At the end of acceleration, the stress and strain appear as transient peak values and the transient effect is nonignorable. The starting acceleration has a great impact on the deformation and dynamic stress of blade, and the maximum deformation near the rim of impeller outlet edge increases 5 per cent above the stable condition. The maximum stress value increases by about 68.7 per cent more than the steady-state condition at the impeller outlet edge near the hub. The quick change of rotating speed makes the vibration problem around the blade tip area more serious, and then it takes the excessive stress concentration and destruction at the blade root.

Originality/value

This study provides basis and reference for the safety operation of pumps during starting period

Details

Engineering Computations, vol. 35 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 13 November 2009

Shuhong Liu, Jianqiang Mai, Jie Shao and Yulin Wu

The purpose of this paper is to predict pressure pulsation in Kaplan hydraulic turbines.

Abstract

Purpose

The purpose of this paper is to predict pressure pulsation in Kaplan hydraulic turbines.

Design/methodology/approach

State of the art numerical simulation techniques are employed to simulate three‐dimensional flows in the whole flow passage of a Kaplan turbine so that pressure pulsations can be computed in both time domain and frequency domain. Numerical results are verified by experiments carried out on the most advanced experimental platform in China.

Findings

It is found that the proposed numerical model is a viable tool for prediction of pressure pulsations. The simulation shows that the model turbine and prototype turbine have the same pressure pulsation frequencies and rotating frequencies and the same transmission patterns under similar operation conditions. However, there is no similarity for the amplitude of the pressure pulsation between the model turbine and the prototype turbine. Therefore pressure pulsations in a prototype turbine cannot be obtained by scaling the experimental results of the model turbine using a similarity relationship.

Practical implications

The findings will be very valuable for the design of hydraulic turbines and large‐scale hydraulic power stations.

Originality/value

The proposed numerical method provides a viable tool for hydraulic turbine and power station designers to predict the pressure pulsations in prototype turbines. It is a useful tool to help improve the performance of hydraulic turbines. The findings made in the numerical simulation have been verified by experiments, which is also a valuable reference for hydraulic turbine designers.

Details

Engineering Computations, vol. 26 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 1 August 1960

ORIGINALLY a motor ship, the Shell tanker Auris of 12,000 tons d.w. has since been fitted with gas turbine machinery and successfully completed sea trials last year, thus…

Abstract

ORIGINALLY a motor ship, the Shell tanker Auris of 12,000 tons d.w. has since been fitted with gas turbine machinery and successfully completed sea trials last year, thus becoming the first tanker to be driven by a gas turbine. Though operating on the same principle as the gas turbines used in many air‐craft, that in the Auris has a different type of construction to make it more robust, to give it a longer life and to make possible the use of a less refined fuel. The Auris also has a new type hydraulic reversing gearbox designed by the Pametrada research organisation of the British shipbuilding industry for use with the gas turbine which provides for astern as well as ahead movement. In this system, a hydraulic coupling is used for ahead rotation of the propeller while a reversing torque converter is used for astern rotation. To eliminate the 6% slip in the ahead coupling, however, a hydraulically operated friction clutch has been fitted and is engaged under cruising conditions.

Details

Industrial Lubrication and Tribology, vol. 12 no. 8
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 1 May 1948

D.M.C.

Within the last two decades great progress has been made in the field of hydrodynamics, both in the theoretical sense as well as the practical. This has been particularly…

Abstract

Within the last two decades great progress has been made in the field of hydrodynamics, both in the theoretical sense as well as the practical. This has been particularly noticeable in the rapid advances made, in aircraft and propeller design, which owes most to the successful application of aerodynamical theory. Not so noticeable, and certainly less obvious, are the results obtained by the application of fluid mechanics in other branches of engineering, as for example, in the design of turbo‐machinery such as turbines, pumps, compressors and that pump‐cum‐turbine arrangement known as the torque converter and the so‐called fluid flywheel. In these latter classes of machinery the more modern theories do not attempt to throw down or displace the older laws, by whose means many successful designs have been accomplished, but on the other hand are direct developments thereof as a result of more intensive study. The most important development of recent years, due to the greater knowledge of fluid mechanics, is adequately illustrated by the amazing progress made in the design and performance of axial compressors. Some thirty years ago, a similar but less spectacular application of fluid mechanics was devised in the form of the Michel or Kingsbury thrust bearing.

Details

Aircraft Engineering and Aerospace Technology, vol. 20 no. 5
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 February 1984

CASTROL'S industrial know‐how has borne important fruit in the world of robotics. Castrol helped Austin Rover and Unimation, the world's largest industrial robot makers…

Abstract

CASTROL'S industrial know‐how has borne important fruit in the world of robotics. Castrol helped Austin Rover and Unimation, the world's largest industrial robot makers, cure a critical problem on the embryonic Metro line at Longbridge in 1980 and now, the product involved, Castrol's Anvol SW68 hydraulic lubricant is the sole specified flame‐retardant fluid for all Unimation robots. With the need to safeguard both manpower and investment increasing all the time flame‐retardant products can be critical to acceptance by industry.

Details

Industrial Lubrication and Tribology, vol. 36 no. 2
Type: Research Article
ISSN: 0036-8792

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