A Novel Solution for a Variable Delivery Flow External Gear Pump for Low Pressure Applications
This study describes an innovative design concept to enable dynamic variable delivery flow control of external spur gear pumps for low and medium pressure applications. The basic principle used to obtain flow variation relies on a variable timing concept previously demonstrated in literature. This principle permits to vary the flow within a certain range, without introducing additional sources of power loss. Previous work proved the applicability of the proposed concept in a pressure compensated design of external gear pump for high pressure applications. This concept took advantage of the pressure differential acting on the slider, which is the internal element able to perform the flow regulation. In this paper, a solution that permits to achieve balance of the pressure forces acting on the slider is proposed. This solution permits to reduce the actuation forces, thus enabling the usage of multiple actuation technologies. An electronic control system is implemented in the prototype to achieve accurate delivery flow control. The proposed solution is cost effective, it consists of a limited number of parts, and it is suitable for pumps without pressure compensation, i.e. for low or intermediate pressures. This work details the aspects of the pump design, which was performed by using a multi-objective algorithm that maximizes the flow operating range and at the same time the pump. The optimum design could achieve a flow variation of about 31% in simulations and this was also demonstrated in actual experiments on a prototype realized within this research. The proposed design can impact several of the current applications of external gear pumps, introducing the additional “flow on demand” capability.
Vacca, Purdue University.
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