Pressure Pulsation Modeling of an External Gear Pump under Coupled Side-Clearance Leakage and Gear Tooth-Breakage Modulation

Abstract

Pressure pulsation in external gear pumps arises from periodic control-volume variation, intermittent communication between tooth spaces and inlet/outlet chambers, and shaft-rotation modulation of tooth-meshing components. Existing frequency-modulation models describe outlet pressure spectra under nominal conditions but rarely consider compound degradation. This paper develops an analytical model incorporating two physically meaningful fault parameters: a side-clearance parameter representing leakage-path enlargement caused by side plate wear, and a tooth-breakage disturbance parameter representing additional hydraulic excitation from local tooth damage. Within the conventional rotational-frequency modulation framework, the model integrates leakage
dynamics, outlet pressure evolution, rotational harmonics, tooth-meshing harmonics, and modulation effects. Side-plate wear is modeled as leakage-induced amplification of meshing components, whereas tooth breakage is represented by an additional periodic pressure disturbance and phase deviation. The resulting Fourier-series formulation extends the nominal pressure model to compound fault conditions. It shows that side-clearance growth mainly changes the amplitude envelope of meshing harmonics, while tooth breakage affects both amplitude and frequency characteristics. Experimental validation based on pressure-spectrum analysis, harmonic tracking, sideband observation, and model fitting supports the proposed mechanism without relying on unverified operating parameters or artificial diagnostic results.

Conflict of Interest Statement
The authors declare no conflicts of interest.