Visualisation research of the flow processes in the outlet chamber–outlet bridge–inlet chamber zone of the gear pumps

This paper is a presentation of the theoretical analysis and visual experimental investigation on flow processes in the inlet chamber, outlet bridge and inlet chamber of the gear pump, commonly known as the trapped volume. In order to achieve that, the size and location of the considered chambers and bridge were determined, and next, the theoretical analysis was carried out. In order to verify the theoretical consideration, an experimental gear pump with transparent (plexi) bodies was designed and built. The pump was tested on a dedicated test stand. The visualisation research conducted for different values of the operational parameters (inlet pressure, temperature, rotational speed) proved the previously carried out theoretical analysis to be correct and, simultaneously, showed that there are areas in the gear pump where the flow processes are seriously disturbed. In order to eliminate the disadvantageous phenomena and processes observed in the pump, a new type of relief grooves was added to the design of the considered area (the solution was developed originally by the authors of this paper), which was consequently theoretically and experimentally examined. The results of both types of the research proved definitely that the application of the relief grooves resulted in a considerable reduction of the negative phenomena and processes in the considered area of the gear pump.