An investigation of the impact of pump deformations on circumferential gap height as a factor influencing volumetric efficiency of external gear pumps

Gear pumps are widely used in transport machines not only in hydraulic drive systems, but also in lubrication and fuel systems. A positive displacement pump converts mechanical energy into pressure energy stored in the liquid, which it transports to the hydraulic cylinder or motor. The efficiency of this process depends on the efficiency of the system components, including the efficiency of the pump, which depends on the amount of internal leakage through the gaps between the high and low pressure sides. The larger the gaps, the lower the volumetric efficiency. This article presents an investigations of impact of pump deformations on circumferential gap height. The article presents a three-dimensional model of an external gear pump using Finite Element Method (FEM) during operating conditions. The model reflects pumping operation at discharge pressures up to 32 MPa and it was validated against strain measurements of pump casing. The simulation results indicate that the pump casing becomes deformed due to pressure, causing a significant increase in the height of the circumferential gap. The increase of the discharge pressure from 8 to 32 MPa causes more than twofold local increase in the height of the circumferential gap. The obtained results indicate that for the correct modelling of the flow generated by gear pumps, it is necessary to consider the change in the size of the gaps resulting from the deformation of the pump

Acoustic tests of type KPF1 high-pressure external gear pumps

This article presents the results of testing the sound pressure level and sound power level of the experimental 3PW-KPF1-24-40-2-776 high-pressure gear pump. Acoustic tests were conducted in an reverberation chamber. The results of the acoustic power tests indicate good acoustic parameters of the tested high-pressure unit

Durability tests of prototype gear pumps with reduced flow ripple

This article presents the results of a durability test of a prototype low-pulsation pump. Hydraulic measurements conducted during the test enabled visualisation of the behaviour of the unit in working conditions. The test was conducted according to a strict factory standard, which states that pump performance parameters cannot decrease by more than 8% during durability testing. The material presented in this publication is the result of a study within the project entitled The development of innovative gear pumps with a reduced level of acoustic emission. The solution developed as part of the project has been successfully implemented for a series of gear pumps consisting of twenty-two units. Among other awards, the product won the Gold Medal at the 10th International Fair of Pneumatics, Hydraulics, Drives and Controls, Kielce 2017

Kompensacje promieniowe w pompach o zazębieniu wewnętrznym

Podstawową zaletą pomp zębatych o zazębieniu wewnętrznym w stosunku do pomp o zazębieniu zewnętrznym jest niższa emisja hałasu, mniejszy współczynnik nierównomierności wydajności oraz bardziej zwarta konstrukcja. Wynika to z płynnej współpracy koła o uzębieniu wewnętrznym oraz koła o uzębieniu zewnętrznym. Uszczelnienie w punkcie styku współpracujących kół na zwiększonym obwodzie kół stykających się z przestrzeniami ssawnymi i tłocznymi prowadzi do zmniejszenia strat napełniania podczas zasysania cieczy... [Wprowadzenie

Development tendencies of clearance compensation methods in internal gear pumps

Contemporary gear pumps, although their design has been under development for over four centuries, keep being modernized and improved. The work presents an analysis of design solutions, taking into account their operational features. The analysis included units with internal mesh. Emphasis was put on the problem of ensuring high values of volumetric efficiency by minimizing leakage in the widest possible range of loads while maintaining the highest possible hydraulic and mechanical efficiency of the displacement unit. Increasing the volumetric efficiency of positive displacement pumps is an important factor in the pursuit of increase in working pressures in hydrostatic systems. An important factor in production of pumps is cost of their production, which often leads to possibility of introducing additional modifications in the pump structure. Often changes made to the materials used in construction of pumps, allow reduction in their mass or sensitivity to the action of the transported liquid. The paper indicates the developed and proprietary solutions in this area and presents the results of experimental research

Application of the Methodology of Multi-Valued Logic Trees with Weighting Factors in the Optimization of a Proportional Valve

Hydraulic valves are used to determine the set values of hydraulic quantities (flow rate, pressure, or pressure difference) in a hydraulic system or its part. This is achieved through the appropriate throttling of the stream flowing through the valve, which is automatically set by the operator (e.g., opening the throttle valve). The procedures for determining its static and dynamic properties were described using the example of modeling a two-stage proportional relief valve. Subsequently, the importance of the design and operational parameters was determined using multi-valued logic trees. Modeling began with the determination of equations describing the flow and movement of moving parts in a valve. Based on the equations, a numerical model was then created, e.g., in the Matlab/Simulink environment (R2020b). The static characteristics were obtained as the result of a model analysis of slow changes in the flow rate through the valve. Various coefficients of logical products have not been taken into account in the separable and common minimization processes of multi-valued logic equation systems in any available literature. The results of the model tests can be used to optimize several types of hydraulic valve constructions

Modelling and Experimental Verification of the Interaction in a Hydraulic Directional Control Valve Spool Pair

This study examined the impact of mechanical oscillation on a hydraulic directional control valve. Particular attention was paid to the oscillating movement of the spool of the hydraulic directional control valve resulting from this impact. Different models of fluid and mixed friction were considered. The models analysed accounted for the relative movement of the directional control valve body and the fact that it is kinematically excited by external mechanical oscillations. It was observed that the mixed friction model, where the frictional force is considered to be the sum of molecular forces acting in micro-areas of contact and drag forces in the fluid, was the best for describing the movement of the spool for a specific spool oscillation frequency. This model yielded significantly more consistency between the simulated and experimental results than the classic fluid friction model