- 學位論文
正齒輪泵內氣穴與齒輪外形效應的數值探討
Numerical investigation of cavitation and gear shape effects of gear pumps
摘要
本研究討論外接正齒輪泵內流場特性，研究轉速、出口壓力、齒數、齒形及氣穴模式對流率、壓力及氣穴的影響。使用CFD模擬軟體進行二維流場分析，為了模擬真實嚙合情形，計算封閉齒輪嚙合點，擷取移動觀測點壓力，取得困油區內部壓力之變化。比較10齒與14齒齒輪泵模擬結果，探討齒數對齒輪泵之影響。再將14齒齒輪泵之齒輪削減100μm得到新齒形，可使嚙合區域面積增加35%，觀察嚙合區域面積增加對困油壓力的影響。模擬結果顯示，在出口錶壓0MPa時，單轉排量不受轉速影響。出口錶壓4MPa時，轉速越高，可提高齒輪泵自吸能力。相同運轉條件時，10齒齒輪泵流率脈動係數大於14齒齒輪泵，且10齒齒輪泵自吸能力優於14齒齒輪泵。在增加嚙合區域面積35%後，原、新齒形在相同出口壓力及轉速時，困油壓力峰值可以減少80%。氣穴常發生在吸入口，在高轉速及低出口壓力時，較容易產生氣穴。
並列摘要
The internal flow-field of an external spur gear pump is numerically studied. The influence of rotational speed, outlet pressure, teeth number and shape of the gear and cavitation model on the flow rate, pressure distribution and cavitation occurrence are revealed. The computational fluid dynamic software ANSYS Fluent is used to analyze the two dimensional hydrodynamic characteristics of the gear pump. The contact points of gear pair are calculated to obtain pulsating trapped pressure within the trapped area. Firstly, the influence of number of teeth on gear pump is investigated by the comparison of the results between 10 and 14 teeth gear pump. Then, the gear shape of 14 teeth gear is modified by cutting 100μm from thickness. The tapped area of new gear shape rises by 35%. The results show that the displacement of single rotation is not affected by the rotational speed with 0MPa outlet pressure. The self-priming capacity increases as the rotational speed increases with 4MPa outlet pressure. With the same outlet-pressure and rotational speed, Pressure fluctuating coefficient of 10 teeth gear pump is greater than that of 14 teeth gear pump. The behavior of the self-priming capacity is the same. Under the same operating conditions, the peak pressure of trapped area decreased by 80%. With a high rotational speed and a low outlet pressure, cavitation is often observed around the suction port.