Stability Analysis of Spools with Imperfect Sealing Gap Geometries

  • Rituraj Rituraj Institute of Machine Design and Hydraulic Drives, Johannes Kepler University, Linz, Austria
  • Rudolf Scheidl Institute of Machine Design and Hydraulic Drives, Johannes Kepler University, Linz, Austria
Keywords: spool valves, sealing gap, Rayleigh-Ritz method, Reynolds equation

Abstract

Spools in hydraulic valves are prone to sticking caused by unbalanced lateral forces due to geometric imperfections of their sealing lands. This sticking problem can be related to the stability of the coaxial spool position. Numerical methods are commonly used to study this behaviour. However, since several parameters can influence the spool stability, parametric studies become significantly computationally expensive and graphical analysis of the numerical results in multidimensional parameter space becomes difficult.

To overcome this difficulty, in this work, an analytical approach for studying the stability characteristics of the spool valve is presented. A Rayleigh-Ritz method is used for solving the Reynolds equation in an approximate way in order to determine an analytical expression for the lateral force on the sealing lands. This analytical expression allows stability analysis of the spool via analytical means which finally results in the expression of critical axial velocity which demarcates the regions of stable behaviour. Simplicity of the expression allows an immediate insight into the role of design parameters in the stability of the spool. To verify the analytical model, a numerical model for spool dynamics is developed in this work and the numerical results are found to match the analytical model in terms of the stability behaviour of the spool.

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Author Biographies

Rituraj Rituraj, Institute of Machine Design and Hydraulic Drives, Johannes Kepler University, Linz, Austria

Rituraj Rituraj received his B.Tech. degree from IIT Guwahati, India in 2013 and his Ph.D. degree from Purdue University, USA in 2020. During his direct-Ph.D. at Maha Fluid Power Research Center, he worked on numerical modelling of External Gear Machines. Currently, he is a postdoctoral researcher at Institute of Machine Design and Hydraulic Drives in JKU, Austria. His research interests include numerical and experimental study of hydraulic components and systems.

Rudolf Scheidl, Institute of Machine Design and Hydraulic Drives, Johannes Kepler University, Linz, Austria

Rudolf Scheidl received his M.Sc. of Mechanical Engineering and Doctor of Engineering Sciences degrees at Vienna University of Technology. He has research and development experience in agricultural machinery (Epple Buxbaum Werke), continuous casting technology (Voest-Alpine Industrieanlagenbau) and paper mills (Voith). Since 1990, he is a full Professor of Mechanical Engineering at Johannes Kepler University, Austria. His research topics include hydraulic drive technology and mechatronic design.

References

B. Winkler, G. Mikota, R. Scheidl, B. Manhartsgruber, Modeling and simulation of the elasto-hydrodynamic behavior of sealing gaps, Aust. J. Mech. Eng. 2 (2005) 65–72. https://doi.org/10.1080/14484846.2005.11464481.

T.-J. Park, Y.-G. Hwang, Effect of Groove Sectional Shape on the Lubrication Characteristics of Hydraulic Spool Valve, Tribol. Online. 5 (2010) 239–244. https://doi.org/10.2474/trol.5.239.

S.H. Hong, K.W. Kim, A new type groove for hydraulic spool valve, Tribol. Int. 103 (2016) 629–640. https://doi.org/10.1016/j.triboint.2016.07.009.

D.C. Sweeney, Preliminary investigation of hydraulic lock, Engineering. 172 (1951) 513–516.

Blackburn, J. F., G. Reethof, J.L. Shearer, Fluid Power Control, MIT Press-John Wiley, New York, 1960.

H.E. Merritt, Hydraulic Control Systems, John Wiley & Sons, Inc., New York, 1967.

T.J. Viersma, Analysis, synthesis, and design of hydraulic servosystems and pipelines, Elsevier, Amsterdam, 1980.

B.J. Hamrock, S.R. Schmid, B.O. Jacobson, Fundamentals of fluid film lubrication, CRC Press, 2004.

M. Borghi, Hydraulic locking-in spool-type valves: Tapered clearances analysis, Proc. Inst. Mech. Eng. Part I J. Syst. Control Eng. 215 (2001) 157–168. https://doi.org/10.1243/0959651011540941.

M. Milani, Designing hydraulic locking balancing grooves, Proc. Inst. Mech. Eng. Part I J. Syst. Control Eng. 215 (2001) 453–465. https://doi.org/10.1177/095965180121500503.

R. Scheidl, M. Resch, M. Scherrer, P. Zagar, An approximate, closed form solution of sealing gap induced lateral forces for imperfect sealing land geometries, in: Int. Sci. Tech. Conf. NSHP 2020, Wrocław, Poland, 2020.

T. Zheng, S. Yang, Z. Xiao, W. Zhang, A ritz model of unsteady oil-film forces for nonlinear dynamic rotor-bearing system, J. Appl. Mech. Trans. ASME. 71 (2004) 219–224. https://doi.org/10.1115/1.1640369.

Published
2021-02-06
Section
NSHP2020

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