On the Volumetric Loss Caused by Incomplete Filling with Undissolved Gas in Positive Displacement Pumps: Lumped Parameter Modeling, CFD Comparisons, and Experimental Validations

Authors

  • Dinghao Pan Maha Fluid Power Research Center, Purdue University, IN, USA
  • Andrea Vacca Maha Fluid Power Research Center, Purdue University, IN, USA
  • Venkata Harish Babu Manne Simerics Inc, MI, USA
  • Daniel Gysling CorVera LLC, CT, USA

DOI:

https://doi.org/10.13052/ijfp1439-9776.2622

Keywords:

Incomplete filling of positive displacement pump, undissolved gas measurement, lumped parameter pump model, 1st-order air-release cavitation, equivalent total air, CFD study of pipe transient air releasee

Abstract

The analysis of the incomplete filling behavior of positive displacement machines requires considerations of the air content within the fluid and its dependency with the suction conditions, which are often associated with high uncertainties. This study contributes to this topic by experimentally studying the incomplete filling behavior of a positive displacement pump and presenting a hybrid modeling method for predicting it. The experimental study involved an original pump testing setup able to measure the gas volume fraction by interpreting the sound wave transmission behavior. Experimental results show that under same sub-atmospheric pump inlet pressure, low-speed operation can enhance the incomplete filling. This behavior is found related to the transient air release process in the line connecting the upstream pressure restriction location (which regulates the sub-atmosphere line pressure) to the pump, which is an effect often neglected in similar analyses on positive displacement machines that neglects the effect of the suction line. Based on the experimental study, a hybrid modeling method for predicting the volumetric losses caused by incomplete filling is proposed, where (i) the amount of undissolved gas in the hydraulic circuit upstream the pump is evaluated by a 1st-order gas release formulation, and (ii) the pump volumetric loss due to incomplete filling is simulated with a lumped volume-based pump model (LP pump model) with an gas-equilibrium fluid model with an equivalent total gas determined from step (i). The 1st-order gas release prediction approach was validated by CFD results of sub-atmospheric pipe flows, for a range of gas-release 1st-order time constants. Using a time constant of 8 s and total air of 6 %, the 1st-order formulation was also validated with experiments. The volumetric loss predicted by the LP pump model were found to agree with the measured pump volumetric efficiency at different operating conditions. The proposed hybrid approach presents a useful simulation tool for studying the incomplete filling of positive displacement pumps with sub-atmospheric inlet pressures, with consideration concerning the layout of the suction circuit.

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Author Biographies

Dinghao Pan, Maha Fluid Power Research Center, Purdue University, IN, USA

Dinghao Pan, PhD., is currently a research scientist at Maha Fluid Power Research Center at Purdue University. He graduated with his PhD from Purdue University in 2024 with the research focus of developing multi-physics coupled simulation models and numerical methodologies for compensated crescent-type internal gear pumps and external gear pumps. His research interest also involves reduced order tribology modeling and external gear pump modeling.

Andrea Vacca, Maha Fluid Power Research Center, Purdue University, IN, USA

Andrea Vacca, PhD, is the Maha Fluid Power Faculty Chair and director of the Maha Fluid Power Research Center at Purdue University. The focus of Andrea’s research activities has been fluid power since the beginning of his professional career in early 2000s. Significant research contributions range from modeling techniques for fluid power systems and components, new designs for pumps, as well as principles for enhanced performance of hydraulic control systems.

Venkata Harish Babu Manne, Simerics Inc, MI, USA

Venkata Harish Babu Manne, PhD., holds PhD from the Maha Fluid Power Research Center at Purdue University, specializing in Fluid Power, Tribology, and Computational Fluid Dynamics (CFD). With a strong background in research and numerical modeling, Harish has published in Mechanical Systems and Signal Processing and Tribology Transactions. Currently, he is a Project Engineer at Simerics Inc. in Novi, MI, where he applies advanced CFD techniques to solve complex engineering challenges.

Daniel Gysling, CorVera LLC, CT, USA

Daniel Gysling, PhD., is founder and CEO of CorVera, LLC, a company with a charter to improve the measurement of liquids with entrained gas. Daniel’s technical expertise is in the areas of fluid dynamics and structural dynamics. Daniel holds BS in Aerospace Engineering from The Pennsylvania State University, and a PhD in Aeronautics and Astronautics from the Massachusetts Institute of Technology.

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Published

2025-07-13

How to Cite

Pan, D. ., Vacca, A. ., Manne, V. H. B. ., & Gysling, D. . (2025). On the Volumetric Loss Caused by Incomplete Filling with Undissolved Gas in Positive Displacement Pumps: Lumped Parameter Modeling, CFD Comparisons, and Experimental Validations. International Journal of Fluid Power, 26(02), 129–162. https://doi.org/10.13052/ijfp1439-9776.2622

Issue

2025: Vol 26 Iss 2

Section

Maha Fluid Power 2024