AN ANALYTIC THERMODYNAMIC MODEL FOR HYDRAULIC RESISTANCES BASED ON CFD FLOW PARAMETERS

Authors

  • Christian von Grabe RWTH Aachen University, Institute for Fluid Power Drives and Controls (IFAS), Steinbachstr. 53, 52074 Aachen, Germany
  • Christian Riedel RWTH Aachen University, Institute for Fluid Power Drives and Controls (IFAS), Steinbachstr. 53, 52074 Aachen, Germany
  • Christian Stammen RWTH Aachen University, Institute for Fluid Power Drives and Controls (IFAS), Steinbachstr. 53, 52074 Aachen, Germany
  • Hubertus Murrenhoff RWTH Aachen University, Institute for Fluid Power Drives and Controls (IFAS), Steinbachstr. 53, 52074 Aachen, Germany

Keywords:

lumped parameter, thermo-hydraulic simulation, hydraulic resistance, orifice, throttle, cavitation, CFD

Abstract

This article illustrates the development of an analytic lumped parameter thermo-hydraulic model for a wide range of hydraulic resistance geometries based on mass flow. The relevant flow parameters such as the contraction coefficient in case of laminar flow separation are derived from CFD simulations. Furthermore, the consideration of cavitation effects can be included. State of the art in lumped parameter simulations of hydraulic circuits utilise volume-flow based equations like the orifice equation, which is extended for a wide variety of geometries and flow conditions including the transition from laminar to turbulent flow by adjusting the discharge coefficient based on empirical equations or lookup tables. The same situation persists for laminar flow description. In this case the Hagen-Poiseuille equation is often used in conjunction with correction factors based on the Reynolds number to regard the transition of laminar to turbulent flow. However, in practical applications the use of different equations for various flow conditions and geometries is cumbersome. Furthermore, in the widely used volume based flow description, the absolute pressure dependency of mass flow due to density changes and critical flow at which cavitation occurs is not accounted for until now. Without consideration of these influences a mass conservative modelling and thus high model precision is not possible. The overall goal of the proposed model is to increase accuracy of hydraulic system simulation tools and to support usability by simplifying parameterisation on basis of dimensions available from data sheets. The results of this study are obtained analytically as well as empirically by means of CFD simulations. Moreover, a large number of performed simulations support the understanding of fundamental effects in hydraulic resistance flow.

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Author Biographies

Christian von Grabe, RWTH Aachen University, Institute for Fluid Power Drives and Controls (IFAS), Steinbachstr. 53, 52074 Aachen, Germany

Christian von Grabe Dipl.-Ing. Christian von Grabe studied Mechanical Engineering at RWTH Aachen University. Since 2010 he is a member of the scientific staff at the Institute for Fluid Power Drives & Controls (IFAS) at RWTH Aachen University.

Christian Riedel, RWTH Aachen University, Institute for Fluid Power Drives and Controls (IFAS), Steinbachstr. 53, 52074 Aachen, Germany

Christian Riedel Dipl.-Ing. Dipl.-Wirt.-Ing. Christian Riedel is project manager at GHH Fahrzeuge in Gelsenkirchen since 2011. Between 2007 and 2011 he was a member of the scientific staff at the Institute for Fluid Power Drives & Controls (IFAS) at RWTH Aachen University. He studied Mechanical Engineering at RWTH Aachen University and Tsinghua University, Beijing..

Christian Stammen, RWTH Aachen University, Institute for Fluid Power Drives and Controls (IFAS), Steinbachstr. 53, 52074 Aachen, Germany

Christian Stammen PD Dr.-Ing. Christian Stammen is director of Research & Development at Fluitroncs GmbH, Krefeld. From 2001 till 2008 he worked at the Institute for Fluid Power Drives & Controls (IFAS) at RWTH Aachen University after his studies in mechanical engineering and earned his Doctorate (2005) and State Doctorate degree (2009) there.

Hubertus Murrenhoff, RWTH Aachen University, Institute for Fluid Power Drives and Controls (IFAS), Steinbachstr. 53, 52074 Aachen, Germany

Hubertus Murrenhoff Univ.-Prof. Dr.-Ing. Hubertus Murrenhoff is director of the Institute for Fluid Power Drives & Controls (IFAS) at RWTH Aachen University. Main research interests cover hydraulics and pneumatics including components, systems, controls, simulation programs and the applications of fluid power in mobile and stationary equipment.

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Published

2018-12-30

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