| Summary: | 碩士 === 國立虎尾科技大學 === 機械設計工程系碩士班 === 106 === Gear pumps use spur gear pair to achieve the requirement of pumping and transmission, because spur gears are easy to obtain like gear shaving which is relatively low cost in gear manufacturing. However, there is a space between the gear tip and the root of the mating gear. This unmeshing space causes the fluid trapped which disturbs the pumping pressure and makes noise when the pump works. The traditional solutions of the fluid trapped is to make two grooves for suction and back flows near by the fluid-trapped area of the gear pairs on their front and back sides the grooves guide the trapped fluid back to the input side. Despite the solution is successful by it still impacts the output flow and decreases the operation efficiency. In this thesis, we proposed the mathematical models of two full-meshing helical gear pumps. The first gear pump is a conventional shape with involute which is generated by a rack with straight side and full-rounded at the tip and root. The second one is generated by a rack with a 3rd order polynomial curve profile. By adjusting of tooth height coefficient the space that traps the fluid will be eliminated. We also propose a method for calculating the flow rate of the full-meshing gear pumps. Finally, we simulate the proposed model by CFD software. The pressure variation of proposed models is better than the traditional one and the results are illustrated in numerical examples. Furthermore, we also analyzed the pressure variation of different gear tooth widths which directly effects the axial contact ratio of the helical gear pairs. We analyze the case of the axial contact ratio which are less, equal and lager then 1, respectivelly.
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