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• A numerical model for the analysis of the compensation mechanism of an aerospace fuel delivery pump is presented. • Coupled fluid and structural effects in lubricating gaps are considered in the analysis. • Effect of frictional forces is shown to create a hysteresis effect on the bearing motion. • Experimental measurements are performed to validate the findings of the numerical model. External gear pumps (EGPs) are one of the most common choices in aerospace engines as a fuel delivery pump. These units usually include a pressure compensation system that defines the lubricating gap at the lateral side of the gears. This lubricating interface is a critical design aspect, which strongly affects the reliability as well as the mechanical and volumetric efficiencies of the pump. Major challenges in designing these lubricating gaps in aero engine fuel pumps, include high operating speeds, delivery pressures and low viscosity of the working fluids. Virtual prototyping methods present a fast and efficient design tool and have the potential to improve the EGP's reliability and efficiency. This paper presents a study on the pressure compensation system of a fuel delivery EGP and shows how the presence of frictional forces opposing the motion of the compensating element significantly affect the lubricating performance of the unit. The presence of these frictional forces produces an effect of hysteresis on the axial balance system, so that the lubricating gaps that develop within the pump at a certain operating condition depend on the previous operating state. This effect was captured in an experimental setup purposely developed for this study at Rolls-Royce. Within this work, this behavior was also reproduced numerically, through a coupled fluid structure interaction – elastohydrodynamic (EHD) model that includes the modeling of these frictional forces. After detailing the implementation of the lateral gap model, this paper presents measurements from carefully conducted experiments which correlate with the simulated predictions of the influence of frictional forces on the performance of a reference EGP design under study. [ABSTRACT FROM AUTHOR]

External gear pumps are one of the most commonly used types of positive displacement machines in high pressure hydraulic control systems, fuel-injection and fuel transport systems. Despite many merits of the traditional external gear pump design with involute teeth, the significant flow non-uniformity intrinsic of such design is considered to be a detrimental aspect, since it causes undesired noise emissions and mechanical vibrations. A disruptive concept of continuous-contact helical gear pumps (CCHGP) was proposed and successfully commercialized in the recent past. Such concept was proven to have clear advantages in terms of noise emissions. However, a clear interpretation of the displacing action and the transient features of the delivery flow was never addressed in past literature. This paper addresses this gap by first discussing the family of gear profiles suitable for implementing the CCHGP design. Subsequently, an analysis on the kinematic flow ripple is given, showing how such design concept can reduce or even eliminate the kinematic flow pulsations. The paper also presents a numerical approach for modelling the operation of CCHGPs, starting from the modeling of the geometric features necessary for a fluid dynamic analysis based on a lumped parameter approach. For model validation purposes, a commercial CCHGP was tested at the authors’ research center, and the simulation results were compared against the experiments, to show the level of accuracy of the model, as well as it potentials for future design studies. [ABSTRACT FROM AUTHOR]

External Gear Pumps are used in various industries to pump non-Newtonian viscoelastic fluids like plastics, paints, inks, etc. For both design and analysis purposes, it is often a matter of interest to understand the features of the displacing action realized by meshing of the gears and the description of the behavior of the leakages for this kind of pumps. However, very limited work can be found in literature about methodologies suitable to model such phenomena. This article describes the technique of modelling external gear pumps that operate with non-Newtonian fluids. In particular, it explains how the displacing action of the unit can be modelled using a lumped parameter approach which involves dividing fluid domain into several control volumes and internal flow connections. This work is built upon the HYGESim simulation tool, conceived by the authors’ research team in the last decade, which is for the first time extended for the simulation of non-Newtonian fluids. The article also describes several comparisons between simulation results and experimental data obtained from numerous experiments performed for validation of the presented methodology. Finally, operation of external gear pump with fluids having different viscosity characteristics is discussed. [ABSTRACT FROM AUTHOR]

• A fully coupled multi-domain multi-physics dynamic system is presented. • Three components of the loadings are explained and analyzed in detail. • The patterns of 3D transient loadings and dynamics are discussed with simulation results. • A design routine for the axial balancing mechanism of helical gear pumps is provided. • The pattern of wear seen from experiments can be replicated by the wear model. This paper presents a multi-domain dynamic simulation model for continuous-contact helical gear pumps, which is an unconventional hydraulic pump design that is capable of canceling its kinematic flowrate variation. In this model, the fluid dynamics (in its lumped-element representation) are fully coupled in a closed feedback loop with other physical domains, including critical tribological interfaces, 3D dynamic loadings on the solid parts, dynamics, and micro-vibrations of the rotors. The model is compared to the analytical derivation and experimental measurements to prove its validity. The model can be used to provide predictive simulations for existing designs, or as a tool to optimize the design to provide better hydrostatic balancing for future iterations of hydraulic pump designs. [ABSTRACT FROM AUTHOR]

• A novel model for curve-constricted leakage flows in hydraulic gear pumps is presented. • The flow model is applicable over a wide range of flow regimes including localized cavitation. • The model is developed in dimensionless form based on sets of CFD simulations. • Model validation is achieved through experiments conducted on a custom test apparatus. The internal leakage flows in external gear and gerotor pumps are often represented by flow through curved constrictions. The nature of this flow can vary from laminar to turbulent and the flow can experience localized cavitation too. In the current literature, there is a scarcity of techniques for accurately modelling such curve-constricted flows which limits the accuracy of the current simulation tools for gear pumps. This paper presents a novel flow model for curve-constricted geometries that is applicable over a wide range of flow regimes including localized cavitation. Using a dimensionless form, the proposed model characterizes the constriction flow velocity as the function of the constriction shape, the pressure difference, and a properly defined cavitation indicator. The functional relationships between these dimensionless parameters are developed based on CFD simulations. The flow model is validated by the means of several experiments conducted on a custom test apparatus. The model presented in this paper can be incorporated in the lumped parameter simulation tools widely used for modelling gear pumps, improving their accuracy in predicting the internal leakages. Consequently, this model will also aid the development of novel energy efficient gear pump designs, where such leakages are kept to a minimum. [ABSTRACT FROM AUTHOR]