Session: 8.4 - Turbomachinery

Paper Number: 155239

155239 - Two-Sided Feed Analysis in Gerotor Pumps to Enhance Filling Performance 

Abstract: 

In the context of CO₂ emissions reduction, internal combustion engines are being replaced by electric motors in various applications. In the hydraulic fluid power field, there is a shift from variable displacement pumps driven by diesel engines to fixed displacement pumps, typically gear types, driven by variable-speed electric motors. Furthermore, to improve efficiency of multi-actuator fluid power circuits, there is a preference, where possible, to transition from a centralized hydraulic architecture to one where each actuator is fed by a dedicated pump, thereby eliminating the need for flow control valves. These new architectures require the pump to operate at significantly higher speeds than in traditional circuits. The main issue that arises when increasing the pump speed is the incomplete filling of the chambers, especially if, due to layout constraints, it is not possible to boost the pump. Incomplete filling not only limits the delivered flow rate but also causes a significant increase in pressure fluctuations at the outlet and in noise levels. In the case of gear pumps, it is well known that supplying the variable volume chambers from both sides of the rotors helps improve filling. However, the effectiveness of dual feeding is also influenced by the arrival point and orientation of the inlet duct, as well as by the allocation of the available space on both sides of the rotors. The analysis of the optimal configuration can only be carried out using 3D CFD models, as it is necessary to take into account the shape and spatial orientation of the different fluid volumes. In this paper, starting from a validated model of a gerotor lubrication pump from a previous study, various inlet port placements are analyzed in the case of dual-sided feeding. In particular, two different positions of the inlet duct are studied when it is axially aligned with the shaft, and three positions are examined when it is in a radial position. Additionally, in this second case, the influence of the axial positioning of the rotors relative to the available space in the housing is also studied, analyzing scenarios where the space on both sides is equal versus those where one side is favored. The findings indicate that axial feeding outperforms radial feeding, with optimal performance achieved when the duct is aligned with the variable volume chambers. For radial feeding, a perfectly symmetrical configuration is preferable; however, slightly asymmetrical setups yield comparable outcomes. Conversely, highly asymmetrical designs, while superior to single-side feeding, fail to fully leverage the benefits of dual-side feeding. This research is not exhaustive, as additional geometric variations remain unexplored, but it demonstrates that, under high-speed operating conditions, CFD-based optimization of the suction volume can significantly enhance volumetric efficiency by several percentage points.

Presenting Author: Massimo Rundo Politecnico di Torino

Presenting Author Biography: Massimo Rundo received his MSc degree in mechanical engineering from the Politecnico di Torino, Italy, in 1996. After graduation, he worked as a visiting researcher, and later as a research fellow, at the Fluid Power Research Laboratory of the Politecnico di Torino, contributing to extensive research projects on positive displacement pumps. In 2005 he joined the faculty at the Department of Energy as assistant professor. He is currently an associate professor of fluid power. His research activity is primarily focused on modelling, simulation and testing of fluid power components and systems.