Unloading flow calculation of gear micropump affecting instantaneous flow

In one meshing cycle of [S1, S4], only the volume change rate DV of trapped oil compression in Fig. 1 [S1, S2] flows into the volumetric extrusion area of E1, O1, N, O2, E2 from the unloading slot at the end of the output chamber, except that part of it flows out to the input cavity through the axial gap. Then QGK should be:

At the same time, according to the classical calculation method of orifice flow, there are:


C – discharge coefficient

NR is the number of unloading grooves at both ends of the oil trap. NR = 1 indicates that only one end is provided with unloading grooves, and NR = 2 indicates that both ends are provided with unloading grooves

The calculation of ar – unloading area qgz can be approximated by the flow formula of parallel plate gap. The length of the gap in [S1, S3] and (S3, S4) is simplified by 0.5 BG, BG. Then:


CZ — axial gap value

μ – medium viscosity

PI, Po — inlet and outlet pressure