AN INNOVATIVE WORKING CONCEPT FOR VARIABLE DELIVERY FLOW EXTERNAL GEAR MACHINE

An innovative and unique working concept for variable delivery external gear machines (VD-EGMs) is presented in this study. The proposed design not only encompasses all the well-known and important advantages of traditional external gear machines but also introduces a feature for varying the displacement (flow delivered per unit revolution). The novel principle of achieving variable displacement in EGMs is based on the variable timing of the connections of the displacement chambers/tooth space volumes (TSVs) with the inlet/outlet ports. The timing variation is obtained by the addition of a simple element (called a “slider”) within the lateral bushings. The position of the slider determines the amount of flow displaced per unit revolution. Starting from the geometry of the design and the proposed concept, analytical expressions for predicting displacement variation, flow rate and input shaft torque were derived. With this working principle, the range of variation of the displacement can be significantly increased by modifying the gear profiles. Therefore, in this work, novel gears with asymmetric teeth profile are designed with the help of a novel tool developed particularly for this process. However, due to the inherent nature of the displacing action of the EGM due to the meshing of the gears, it is not possible to achieve a full flow variation from 0%-100%. Therefore, to maximize the range of flow variation while considering all the other important performance features of the machine to be maintained at an optimum, a multi-objective genetic algorithm based optimization method is used to identify the optimal design of gears and grooves in the lateral bushings. The performance of the desig

A Flow Control System for a Novel Concept of Variable Delivery External Gear Pump

This paper describes a novel concept for a low cost variable delivery external gear pump (VD-EGP). The proposed VD-EGP is based on the realization of a variable timing for the connections of the internal displacement chambers with the inlet and outlet ports. With respect to a standard EGP, an additional element (slider) is used along with asymmetric gears to realize the variable timing principle. Previously performed tests confirmed the validity of the concept, for a design capable of varing the flow in the 65%-100% range. Although the VD-EGP concept is suitable for various flow control system typologies (manual, electro-actuated, hydraulically flow- or pressure- compensated), this paper particularly details the design and the test results for a prototype that includes both a manual flow control system and a pressure compensator. Flow vs pressure and volumetric efficiency curves are discussed along with transient (outlet flow fluctuation) features of the VD-EGP

A novel optimization methodology for designing external gear machines

The aim of this research is to propose a novel design methodology for identifying the optimal design of external spur gear machines. Due to the existence of complex inter-dependencies between design parameters and the performance of the machine, presently their designs are extensively based on empirical procedures, with limited recourse to simulations. In this research the problem of optimizing the volumetric performance, minimizing internal cavitation, pressure peaks and noise emissions has been addressed by means of a multi-objective optimization algorithm that optimizes the most important components of the external gear machines. The performance of the particular design configuration of the machine was accurately predicted using the simulation tool HYGESim (HYdraulic GEar machines Simulator), providentially modified within the research. The optimization problem has been described in terms of design variables, design constraints, objective functions and optimization strategies that permit the determination of feasible designs that optimizes the performance of the unit. The design methodology was successfully applied for two different design solutions, specifically for high pressure and low pressure applications. The optimal designs for both these applications were identified and their improvements in performance were compared with existing commercial design. Qualitative trends representing the different mutual inter-relationships between the design variables that influence the performance of the machine were also characterized

A Flow Control System for a Novel Concept of Variable Delivery External Gear Pump

This paper describes a novel concept for a low cost variable delivery external gear pump (VD-EGP). The proposed VD-EGP is based on the realization of a variable timing for the connections of the internal displacement chambers with the inlet and outlet ports. With respect to a standard EGP, an additional element (slider) is used along with asymmetric gears to realize the variable timing principle. Previously performed tests confirmed the validity of the concept, for a design capable of varing the flow in the 65%-100% range. Although the VD-EGP concept is suitable for various flow control system typologies (manual, electro-actuated, hydraulically flow- or pressure- compensated), this paper particularly details the design and the test results for a prototype that includes both a manual flow control system and a pressure compensator. Flow vs pressure and volumetric efficiency curves are discussed along with transient (outlet flow fluctuation) features of the VD-EGP