Theoretical analysis for variable delivery flow external gear machines based on asymmetric gears

Abstract

This paper presents an analytical approach for the analysis of a new working concept for variable delivery external gear machines. The proposed design principle encompasses all the advantages of conventional fixed displacement external gear machines, along with a simple mechanism to change the displaced flow per shaft revolution. The variation in the displaced flow is achieved by realizing a variable timing for the connections of each tooth space volume (volume between two adjacent teeth of the gears) with the inlet and outlet. This is achieved through a movable slider placed at the gear lateral sides. The position of the slider determines the amount of flow displaced by the unit per revolution. Analytical expressions which define the range of percentage variation in flow displacement that can be achieved based on a generic asymmetric design of the gears are presented. The paper presents a detailed analytical derivation for geometric displacement, flow delivered at the outlet and shaft torque required during operation as well as flow non-uniformity/pulsation. The analytical expressions were compared with proof of concept test. Experimental results were in line with the analytical prediction and show a 32% variation in displacement. These positive results show promising potentials for the working of a new concept for variable delivery external gear machine.