Study of leakage flow through a spool valve under blocked-actuator port condition—Simulation and experiment

2013 ◽  
Vol 228 (8) ◽  
pp. 1405-1417 ◽  
Author(s):  
Milan K Mondal ◽  
Nirmal K Manna ◽  
Rana Saha
Keyword(s):  
Experimental Results ◽  
Radial Clearance ◽  
Leakage Flow ◽  
Pressure Sensitivity ◽  
Hydraulic Control ◽  
Leakage Flow Rate ◽  
Simulation And Experiment ◽  
Flow Through ◽  
Spool Valve ◽  
Hydraulic Control System

The spool valve is the key component of hydraulic control system, and the performance of spool valve depends on its leakage behaviour. Again, the leakage flow of spool valve is highly susceptible to valve uncertain dimensions, radial clearance and overlap or underlap. In the present work, the relative performance of critically lapped, underlapped and overlapped valves has been demonstrated in terms of leakage flow rate and pressure sensitivity about the metered ports. An approach to explore uncertain dimensions of the valve has been developed using CFD as an investigating tool. The comparison of CFD prediction against experimental results has also been carried out. It is found that the CFD predictions are in excellent agreement with the experimental results.

A Comparative Study of Navier-Stokes Equation and Reynolds Equation in Simulating Spool Valve

2011 ◽  
Author(s):  
S. H. Hong ◽  
S. I. Son ◽  
K. W. Kim
Keyword(s):  
Pressure Distribution ◽  
Stokes Equation ◽  
Flow Rate ◽  
Reynolds Equation ◽  
Navier Stokes ◽  
Radial Clearance ◽  
Leakage Flow ◽  
Navier Stokes Equation ◽  
Leakage Flow Rate ◽  
Spool Valve

In order to maintain the accurate and precise movement of the actuator of the hydraulic systems, it is necessary to guarantee smooth function of the fluid flow control valves. Concerning hydraulic valves, the spool type directional control valve has particular lock problem. The hydraulic lock occurs when uneven pressure distribution surrounding the spool in the clearance between spool and sleeve causes the spool to move sideways out of its centered position. And the contact between spool and sleeve causes to increase friction and eventually, the spool is blocked inside the sleeve. To reduce the possibility of hydraulic lock, peripheral grooves balancing uneven pressure distribution in the radial clearance is commonly applied to spool. Reynolds equation is commonly used to investigate the lubrication characteristics of the spool valve. However, some of assumptions used in Reynolds equation are not valid when cavitation occurs or fluid inertia is significant in spool valve. So, the study on the applicability and precision of Reynolds equation for spool valve analysis is needed. In this study, the differences between the results from Navier-Stokes equation and Reynolds equation are compared when the cavitation is considered. Frictional forces, lateral forces and leakage flow rate with various aspect ratio of groove are calculated. Besides, when the number of groove is increased, the forces and leakage flow rate are compared. Based on the comparison the applicability of Reynolds equation in calculating the spool valve is also discussed.

A New Approach of Direct Digital Control for Spool Valves

1999 ◽  
Author(s):  
J. Ruan ◽  
R. Burton
Keyword(s):  
Digital Control ◽  
Stepper Motor ◽  
Hydraulic Control ◽  
New Approach ◽  
Control Approach ◽  
Speed Of Response ◽  
Spool Valves ◽  
Spool Valve ◽  
Direct Digital Control ◽  
Hydraulic Control System

Abstract In many applications, digital valves driven from stepping motors are often characterized by quantitative errors and in some cases, slow response. A new means of direct digital control is introduced for a spool valve actuated by a stepper motor. With this control strategy, both excellent speed of response and accuracy are simultaneously sustained for the valve. By way of illustration, the characteristics of a digital spool valve are theoretically and experimentally investigated. This paper also deals with the design of the controller and some concepts concerning the digital control of a valve, such as initialization, false protection, etc. An example is given to demonstrate the effectiveness of this digital control approach for a practical electro-hydraulic control system.

The Interaction of Turbine Inter-Platform Leakage Flow With the Mainstream Flow

2005 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Three Dimensional ◽  
Leakage Flow ◽  
Turbine Performance ◽  
Leakage Flow Rate ◽  
Single Piece ◽  
Flow Through ◽  
Aero Engines ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Leakage Fraction

Individual nozzle guide vanes (NGVs) in modern aero engines are often cast as a single piece with integral hub and casing endwalls. When in operation there is a leakage flow through the chord-wise inter-platform gaps. An investigation into the effect of this leakage flow on turbine performance is presented. Efficiency measurements and NGV exit area traverse data from a low speed research turbine are reported. Tests show that this leakage flow can have a significant impact on turbine performance, but that below a threshold leakage fraction this penalty does not rise with increasing leakage flow rate. The effect of various seal clearances are also investigated. Results from steady-state simulations using a three-dimensional multiblock RANS solver are presented with particular emphasis paid to the physics of the mainstream/leakage interaction and the loss generation.

scholarly journals Effect of Swirl on Rotordynamic Forces Caused by Front Shroud Pump Leakage

2002 ◽  
Vol 124 (4) ◽  
pp. 1005-1010 ◽  
Author(s):  
Yun Hsu ◽  
Christopher E. Brennen
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Leakage Flow ◽  
Unsteady Forces ◽  
Low Leakage ◽  
Leakage Path ◽  
Leakage Flow Rate ◽  
Inlet Swirl ◽  
Flow Through ◽  
Rotordynamic Forces

Unsteady forces generated by fluid flow through the impeller shroud leakage path of a centrifugal pump were investigated. The effect of leakage path inlet swirl (pump discharge swirl) on the rotordynamic forces was re-examined. It was observed that increasing the inlet swirl is destabilizing both for normal and tangential rotordynamic forces. Attempts to reduce the swirl within the leakage path using ribs and grooves as swirl brakes showed benefits only at low leakage flow rate.

Analysis of a Three-Phase Pulsating Flow Hydraulic System

1978 ◽  
Vol 5 (1) ◽  
pp. 24-30
Author(s):  
Y.M. EI-Ibiary ◽  
P.R. Ukrainetz ◽  
P.N. Nikiforuk
Keyword(s):  
Control System ◽  
Hydraulic System ◽  
Low Pressure ◽  
Area Ratio ◽  
Pulsating Flow ◽  
Experimental Results ◽  
Hydraulic Control ◽  
Three Phase ◽  
Hydraulic Control System

An analysis is presented of a three-phase pulsating flow hydraulic control system. Such a system consists of five basic components – an alternator, transformers, rectifiers, a compensator and high and low pressure accumulators. In carrying out this analysis, it is assumed that there is no leakage, the fluid is incompressible, the transformer area ratio is unity and the transformers and check valves of the rectifier unit are symmetric. Some typical simulation and experimental results are included.

Design of Hydraulic Servovalve for Maximum Pressure Sensitivity

1984 ◽  
Vol 106 (1) ◽  
pp. 116-119
Author(s):  
S. LeQuoc
Keyword(s):  
Load Flow ◽  
Radial Clearance ◽  
Maximum Pressure ◽  
Physical Parameters ◽  
Pressure Sensitivity ◽  
Sensitivity Curves ◽  
Spool Valve ◽  
Land Width

The performance of a hydraulic servomechanism depends largely upon the servovalve characteristics which in turn are determined by various physical parameters such as spool land width, radial clearance etc... The work described in this paper is concerned with the design of hydraulic spool valve for a maximum pressure sensitivity in a no load flow application. It has been demonstrated that this condition is achieved by having an underlap equal to the radial clearance. The results are experimentally verified and the effects of rounded corners of metering lands on the pressure sensitivity curves are discussed.

The Interaction of Turbine Inter-Platform Leakage Flow With the Mainstream Flow

2005 ◽  
Vol 129 (2) ◽  
pp. 303-310 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Three Dimensional ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Turbine Performance ◽  
Leakage Flow Rate ◽  
Single Piece ◽  
Flow Through ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Leakage Fraction

Individual nozzle guide vanes (NGV’s) in modern aeroengines are often cast as a single piece with integral hub and casing endwalls. When in operation, there is a leakage flow through the chord-wise interplatform gaps. An investigation into the effect of this leakage flow on turbine performance is presented. Efficiency measurements and NGV exit area traverse data from a low-speed research turbine are reported. Tests show that this leakage flow can have a significant impact on turbine performance, but that below a threshold leakage fraction this penalty does not rise with increasing leakage flow rate. The effect of various seal clearances are also investigated. Results from steady-state simulations using a three-dimensional multiblock Reynolds-averaged Navier-Stokes solver are presented with particular emphasis paid to the physics of the mainstream/leakage interaction and the loss generation.

Attempts on the Reduction of Leakage Flow Through the Stator Well in an Axial Compressor

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Xiaozhi Kong ◽  
Yuxin Liu ◽  
Gaowen Liu ◽  
David M. Birch ◽  
Longxi Zheng
Keyword(s):  
Tangential Velocity ◽  
Axial Compressor ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Performance Improvements ◽  
Pressure Distributions ◽  
Leakage Flow Rate ◽  
Flow Mechanisms ◽  
Total Temperature ◽  
Flow Through

As performance improvements of compressors become more difficult to obtain, the optimization of stator well structure to control the reverse leakage flow is a more important research subject. Normally, the stator well can be considered as two rotor–stator cavities linked by the labyrinth seal. The flow with high tangential velocity and high total temperature exited from the stator well interacts with the main flow, which can affect the compressor aerodynamic performance. Based on the flow mechanisms in the basic stator well, four geometries were proposed and studied. For geometry a and geometry b, seal lips were attached to the rotor and stator inside downstream rim seal while impellers were positioned in the cavities for geometry c and geometry d. Leakage flow rates, tangential velocities, and pressure distributions in the cavities were analyzed using validated method of computational fluid dynamics. In the current study, where ω = 8000 rpm, π = 1.05–1.30, the maximum reductions of leakage flow rate for geometry a and geometry b are 7.9% and 15.9%, respectively, compared to the baseline model. In addition, the rotating impellers in the downstream cavity for geometry c contribute to a more significant pressure gradient along radial direction, reducing the leakage flow as much as 46%. Although the stationary impellers in the upstream cavity for geometry d appear to have little effect upon the leakage, these impellers can be used to adjust the tangential velocity of ejected flow from the stator well to the mainstream.

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