Studies on Volumetric Efficiency and Theoretical Delivery of Gear Pumps

概要

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The volumetric efficiency of the gear pumps calculated from the equations which are shown in the past publications gives a value of over 100%. Therefore, the author calculated the theoretical delivery of the pumps with arbitrary shapes of tooth curve in the lengthwise direction, results of which can be used for the calcularion of the efficiency. Furthermore, physical behaviours of fluids which cause differences in theoretical delivery due to both the differences in tooth curve and backlash are clarified. From the experiment, it was found that the cases showing over 100% efficiency were restricted to the pumps having a backlash in the gears. Discussions are made on this phenomenon and the following equation for calculating the volumetric efficiency, η_ν is presented. η_ν=1-(q_1+q_2+q_3+κΔV)/(V_th1) where, V_th1 is the theoretical delivery for the non-backlash pump ; and q_1,q_2 and q_3 are leakages through the gear tip, gear side and backlash respectively ; ΔV is approximately equal to the difference between the two theoretical deliveries V_th1 and V_th2,where V_th2 is the delivery for the pumps having a backlash ; κis a non-dimensional constant and ΔV=0 for the non-backlash pumps.
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