Measurement of Pulsating Flowrate from a Gear Pump

Abstract

Oil hydraulic gear pumps are well known for yielding a pulsating flowrate which is theoretically determined by the geometry of gears. In the present paper, we aim to measure actual waveforms of a gear pump output with high-frequency pulsation. The measurement is based on detecting pressure differences kinetically induced by the motion of an oil column, and the accuracy of the method has proven satisfactory in advance of actual use. The findings are as follows : (1) Whether the pulsation impedance for the 1st harmonic at the pump outport is larger or smaller than that for the 2nd harmonic mainly dominates the waveforms of flowrate pulsation. (2) According to whether the impedance for the 1st harmonic is larger or smaller than that for the 2nd harmonic, the 2nd harmonic of pump output becomes larger and the 1st one smaller than the theoretical predictions, or vice versa. (3) This tendency becomes more marked as the line pressure increases.