Question

1. There is an external gear pump with teeth number z-13, the diameter of the addendum circle De-75 mm, the distance between the center points A-65 mm, gear width B-35 mm, volumetric efficiency ,M-9096, rotating speed n 1500 r/min. Find the flowrate q (/min) of the pump. 2. How does trapping oil problem occur in an external gear pump? How to solve it in design? 3. Analyze the forces acting on the shafts in an external gear pump. What measures can be taken in design when we want to increase the pressure ratings of an external gear pump? 4. Where does the most leakage occur in an external gear pump? What are the commonly used ways in design to improve the volumetric efficiency of a gear pump?

Answer 1

For External gear pump Addendum circle dia, D1 = 75 mm No of teeth z = 13 In gear pump both gears are of same size and centre distance between gears = 2.x radius = diameter [pitch circle dia] pcd = 65 mm module of gear , m = delta/z = PcD/Z = 65/13 = 5 mm In general Addendum of gear = module cm addendum = addendum + clearance = 1.157 times m Therefore total depth = addendum + dedendum = (1 + 1.57) times m Therefore diameter of dedendum circle D1 = Do - (2.157 times 5) = 75 - 5 times 2.157 = 64.215mm Therefore Area enclosed b/w tooth = pi/4 (delta^2 - Delta 1^2) width of teeth = 35mq Therefore volume enclosed , v = pi/4 (P^2 - P1^2) RPM, N = 1500 vpm Therefore Discharge Q = pi/4 (p0^2 - pi^2) times N = pi/4 (75^2 - (64.215^2 times 1500 = 1768834.99 m m ^3 /min Therefore Q = 1.7688 L/Min