Hydraulic Pump Performance and Dynamics

Hydraulic pumps lie at the heart of fluid power systems, converting mechanical energy into pressurised flow for applications ranging from industrial machinery to mobile equipment. Performance evaluation typically centres on volumetric efficiency, mechanical efficiency and overall energy conversion, while dynamic characteristics encompass pressure pulsations, flow ripple and noise generation. Recent advances have focused on high-speed operation and power-dense designs, which present challenges in terms of seal leakage, churning losses, cavitation and thermal management. A combination of lumped-parameter models, computational fluid dynamics and experimental test rigs has deepened understanding of internal flow phenomena, enabling more accurate prediction of efficiency losses and dynamic responses. Improved insights into component interactions and fluid-structure coupling are guiding novel design optimisation and material selection, with the aim of reducing energy consumption and extending service life under demanding operating conditions.

Research from Nature Portfolio

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Research from all publishers

Studies on churning losses in high-speed two-dimensional piston pumps have combined mathematical modelling, computational simulation and test-rig measurements to isolate the torque contributions of rotating parts immersed in hydraulic fluid. Results indicate a marked increase in churning torque beyond critical speeds, driven by the transition from laminar to turbulent regimes and the onset of cavitation, with deviations between model and experiment growing at speeds above 8 000 rpm. Complementary work on mechanical efficiency of high-speed two-dimensional piston pumps has developed an analytical framework that accounts for viscous shear and stirring losses, as well as rolling friction between guiding elements. Experimental validation under varying load pressures revealed that rolling friction coefficients change with pressure, leading to divergence between predicted and observed efficiencies at high loads. Investigations into oil film characteristics of ultra-high-pressure axial piston pumps have mapped oil film thickness and pressure distribution under loads up to 70 MPa. Finite-volume solutions of the Reynolds equation show minimum film thicknesses approaching 2–3 µm, identifying critical clearance thresholds and guiding improved piston–cylinder gap design for enhanced volumetric efficiency and reduced wear.

Hydraulic Pump Performance and Dynamics publication trend

The graph below shows the total number of articles in hydraulic pump performance and dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Volumetric efficiency: The ratio of actual flow delivered to the theoretical displacement volume, reflecting internal leakage and compressibility effects.

Mechanical efficiency: The ratio of hydraulic power output to the input power, accounting for frictional and churning losses within moving components.

Churning losses: Energy losses due to the viscous drag of rotating parts moving through the hydraulic fluid, often scaling non-linearly with speed and influenced by fluid turbulence.

Cavitation: The formation and collapse of vapour cavities within low-pressure zones, which reduces effective delivery flow rate and can cause surface damage.

Oil film thickness: The minimum separation distance between sliding or rotating elements maintained by a continuous fluid film, critical for preventing asperity contact and minimising wear.

References

1. Numerical and experimental study on the churning losses of 2D high-speed piston pumps. Engineering Applications of Computational Fluid Mechanics (2020).
2. Research on the Mechanical Efficiency of High-Speed 2D Piston Pumps. Processes (2020).
3. Study on Oil Film Characteristics of Piston-Cylinder Pair of Ultra-High Pressure Axial Piston Pump. Processes (2020).