Oscillations in a system of two coupled self‐regulating spool valves with switching properties

In hydraulic components, nonlinearities are responsible for critical behaviors that make it difficult to realize a reliable mathematical model for numerical simulation. With particular reference to hydraulic spool valves, the viscous friction coefficient between the sliding and the fixed body is an unknown parameter that is normally set a posteriori in order to obtain a good agreement with the experimental data. In this paper, two different methodologies to characterize experimentally the viscous friction coefficient in a hydraulic component with spool are presented. The two approaches are significantly different and are both based on experimental tests; they were developed in two distinct laboratories in different periods of time and applied to the same flow compensator of a pump displacement control. One of the procedures was carried out at the Fluid Power Research Laboratory of the Politecnico di Torino, while the other approach was developed at the University of Parma. Both the proposed methods reached similar outcomes; moreover, neither method requires the installation of a spool displacement transducer that can significantly affect the results.

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Spool Valve Hydraulic Measurement Flow Pattern Error Based on Variable Discharge Coefficient

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.667.444 ◽

2015 ◽

Vol 667 ◽

pp. 444-448

Author(s):

Zhuo Lin

Keyword(s):

Flow Pattern ◽

Discharge Coefficient ◽

Compensation Method ◽

Measuring Process ◽

Important Method ◽

Flow Pattern Transition ◽

Spool Valves ◽

Spool Valve ◽

Submerged Discharge

Spool valves are the main elements in electro-hydro servo valves. Hydraulic measurement is an important method for spool valve’s null cutting measuring process. Because of the flow pattern transition, the discharge coefficient is a variable. This phenomenon causes errors if we assume the discharge coefficient is a constant as we always do. In this paper, the variable discharge coefficient is considered to the submerged discharge equation, and the flow pattern error is defined. For improving the precision of overlap values measurements, a compensation method of flow pattern error is presented in this paper.

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Internal Leakage Predicition of Hydraulic Spool valves Based on Acoustic Emission Technology

Journal of Physics Conference Series ◽

10.1088/1742-6596/2113/1/012016 ◽

2021 ◽

Vol 2113 (1) ◽

pp. 012016

Author(s):

Fei Song ◽

Likun Peng ◽

Jia Chen ◽

Benmeng Wang

Keyword(s):

Acoustic Emission ◽

High Frequency ◽

Peak Frequency ◽

Leakage Rate ◽

High Frequency Band ◽

Signal Characteristics ◽

Spool Valves ◽

The Relationship ◽

Ae Signals ◽

Acoustic Emission Technology

Abstract In order to realize the nondestructive testing (NDT) of the internal leakage fault of hydraulic spool valves, the internal leakage rate must be predicted by AE (acoustic emission) technology. An AE experimental platform of internal leakage of hydraulic spool valves is built to study the characteristics of AE signals of internal leakage and the relationship between AE signals and leakage rates. The research results show the AE signals present a wideband characteristic. The main frequencies are concentrated in 30~50 kHz and the peak frequency is around 40 kHz. When the leakage rate is large, there are significant signal characteristics appearing in the high frequency band of 75~100 kHz. The exponent of the root mean square(RMS) of AE signals is positively correlated with the exponent of the leakage rate only if the leakage rate is greater than 2~3 mL/min. This find could be used to predict the internal leakage rate of hydraulic spool valves.

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Cavitation Inception in Spool Valves

Journal of Fluids Engineering ◽

10.1115/1.3241768 ◽

1981 ◽

Vol 103 (4) ◽

pp. 564-575 ◽

Cited By ~ 37

Author(s):

C. Samuel Martin ◽

H. Medlarz ◽

D. C. Wiggert ◽

C. Brennen

Keyword(s):

Reynolds Number ◽

Hydraulic Systems ◽

Cavitation Inception ◽

Pressure Transducers ◽

High Frequency Response ◽

Annular Jet ◽

Directional Control ◽

Valve Opening ◽

Response Pressure ◽

Spool Valves

Cavitation has been investigated in directional control valves in order to identify damage mechanisms characteristic of components of aircraft hydraulic systems. Tests have been conducted in a representative metal spool valve and in a model three times larger. Data taken under noncavitating conditions with both valves showed that the position of the high-velocity annular jet shifts orientation, depending upon valve opening and Reynolds number. By means of high-frequency response pressure transducers strategically placed in the valve chamber cavitation could be sensed by the correlation of noise with a cavitation index. The onset of cavitation can be detected by comparing energy spectra for a fixed valve opening and a constant discharge. Another sensitive indicator of cavitation inception is the ratio of cavitating to noncavitating spectral densities. The incipient cavitation number as defined in this investigation is correlated with the Reynolds number for both valves.

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A New Approach of Direct Digital Control for Spool Valves

10.1115/imece1999-0778 ◽

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.

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Hydraulic Spool Valve Metering Notch Characterization Using CFD

Fluid Power Systems and Technology ◽

10.1115/imece2003-42420 ◽

2003 ◽

Cited By ~ 4

Author(s):

Roger Yang

Keyword(s):

Flow Characteristics ◽

Post Processing ◽

Hydraulic Oil ◽

Simulation Procedure ◽

Discharge Coefficients ◽

Oil Flow ◽

Computational Fluid Dynamics Cfd ◽

Spool Valves ◽

Spool Valve ◽

Mode A

This paper presents some results from an attempt to characterize hydraulic oil flow inside spool valves with different spool metering notches using Computational Fluid Dynamics (CFD). Hydraulic spool valve oil flow under different conditions has been simulated using a commercially available CFD software program. The fluid flow is assumed steady-state, incompressible, isothermal and normally in a turbulent mode. A complete simulation procedure is presented from parametric geometry creation with a 3-D solid CAD program through final post-processing of CFD results. Main focus of this study is to explore the effects of geometric parameters of notches on important hydraulic oil flow characteristics, such as flow force and discharge coefficients. Formulas, intended for predicting such flow forces and discharge coefficients at different stage of spool notch openings, have been generalized and summarized under certain conditions based on a CFD result database from groups of same types of notches. Results comparison to experimental data is also presented.

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Closure to “Discussions of ‘Cavitation Inception in Spool Valves’” (1981, ASME J. Fluids Eng., 103, pp. 575–576)

Journal of Fluids Engineering ◽

10.1115/1.3241771 ◽

1981 ◽

Vol 103 (4) ◽

pp. 576-576

Author(s):

C. Samuel Martin ◽

H. Medlarz ◽

D. C. Wiggert ◽

C. Brennen

Keyword(s):

Cavitation Inception ◽

Spool Valves

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Design and Testing of a Linear-Driven Electro-Hydrostatic Actuator

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4044474 ◽

2019 ◽

Vol 141 (12) ◽

Cited By ~ 2

Author(s):

Zimeng Wang ◽

Zongxia Jiao ◽

Xinglu Li

Keyword(s):

Flow Rate ◽

Rate Equation ◽

High Frequency ◽

Reciprocating Motion ◽

Series Of Experiments ◽

Spool Valves ◽

Design And Testing

Abstract This paper presents a novel hydrostatic actuator, which is named as linear-driven electro-hydrostatic actuator (LEHA). In an LEHA, the actuator is driven by a novel collaborative rectification pump (CRP), which incorporates two miniature cylinders and two spool valves. Specifically, the CRP is driven by two linear oscillating motors, which are designed and optimized to generate reciprocating motion at high frequency with adequate stroke. CRP offers a highly novel linear fluid pump with flexibility in bi-directionally driving. In this paper, schematic of LEHA is first presented and its kinematic flow rate equation is derived. Then the design of CRP, linear oscillating motor, as well as the whole LEHA prototype is introduced. Performance of the LEHA is demonstrated through a series of experiments and simulation, and analysis of the results is also included.

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