Development and analysis of performance characteristics of a new type of external gear pump using curvilinear involute gears

Today, external gear pumps are widely used in the industry due to their easy production, low production cost, easy integration into hydraulic systems, ability to operate at high pressures, transmitting fluids with high viscosity, and wide speed range. In addition, the noise level of the pump, the formation of cavitation caused by the sudden pressure drop at the pump inlet, the wear of the pump elements over time, as well as the reverse flow formation caused by the wear, have been a disadvantage for this type of pumps by reducing the pump performance and life. In order to eliminate such disadvantages, researchers have carried out many studies and these studies are still continuing. In this thesis, the use of curvilinear involute gears, whose efficiency has been proven by studies in the literature but not used for external gear pumps, were investigated. In this context, reference involute profile and asymmetrical involute profile gears were redesigned as curvilinear evolvent profiles with different radii of curvature (R90-135-180-225). New types of external gear pump designs were developed, CFD analysis were performed, validation experiments were carried out and pump components were manufactured. In addition, for the AISI 5140 material used in the manufacture of gears, machinability tests were carried out under different cooling/lubrication conditions and the machinability metrics were improved. As a result of the study, the gear pump designed with a profile tooth with a radius of curvature of R180, the hydraulic operating performance (volumetric efficiency, flow fluctuation and cavitation) was improved compared to the pump used as the reference gear pump with involute gear. In addition, significant improvements were achieved in the machinability metrics of AISI 5140 material by using liquid nitrogen, which is not widely used in the industry, for machinability tests under cooling/lubrication conditions.