附件24.4 Hydraulic pumps transform mechanical energy (M.n)into hydraulic energy (P.Q)which is transmitted to the actuator of hydraulic system.As a result of the torque loss due to mechanical friction between the components with relative motion(the value expressed by the Mechanical efficiency n.m)and the leakage in the high-pressure chamber(the value expressed by the Volumetric efficiency nv),Output power must be less than input power of the pump.The overall efficiency n is the ratio of the output power P0 to the input power Pi.n=Po /Pi =n m*n v*n h =n m*n v It's more difficult to determine the value of(n.M)directly,so we could generally measure n v and n,and then calculate(n.m) Table 5-1 Project Title rated nominal volumetricoverall Pendulate pressure lisplacemen t effic ciency efficiency kgf/cm2 kgf/cm2 single-acting <=10 >=80 >=65 vane 16 >=88 >=78 hydraulic 63 25-32 >=90 >=80 pump with 40~125 >=92 >=81 fixed =160 =93 82 delivery 3.Flow-pressure characteristics of hydraulic pump Determine the experimental flow rate of the hydraulic pump under difference pressures and then draw the curve of flow-pressure characteristics Q=f1(P).The leakage in the high-pressure chamber leads to the loss of flow rate.The lower the oil viscosity is,the higher the pressure is and the greater the leakage is.We can read out the value of pressure from pressure meter and read out the value of flow rate from oval wheel flow meter which has the measuring range at 101ml/min or 100ml/min (1)Flow rate without load:if the outlet pressure is beyond zero,the practical flow rate is less than the theoretical flow rate due to the existence of the flow rate leakage,but when the outlet pressure is zero or there is no pressure differential between the inlet and 9附件 24.4 9 Hydraulic pumps transform mechanical energy (M.n) into hydraulic energy (P.Q)which is transmitted to the actuator of hydraulic system .As a result of the torque loss due to mechanical friction between the components with relative motion ( the value expressed by the Mechanical efficiency η.m)and the leakage in the high-pressure chamber(the value expressed by the Volumetric efficiency ηv), Output power must be less than input power of the pump .The overall efficiency η is the ratio of the output power P0 to the input power Pi , η=Po /Pi =η m *η v *η h =η m *η v It’s more difficult to determine the value of (η. M) directly, so we could generally measure η v and η, and then calculate (η.m) Table 5-1 Project Title rated pressure kgf/cm 2 nominal displacement volumetric efficiency % ml/r overall efficiency % Pendulate kgf/cm 2 <=10 >=80 >=65 16 >=88 >=78 25～32 >=90 >=80 40～125 >=92 >=81 single-acting vane hydraulic pump with fixed delivery 63 >=160 >=93 >=82 ±2 3. Flow –pressure characteristics of hydraulic pump Determine the experimental flow rate of the hydraulic pump under difference pressures and then draw the curve of flow –pressure characteristics Q = f 1 (P).The leakage in the high-pressure chamber leads to the loss of flow rate. The lower the oil viscosity is, the higher the pressure is and the greater the leakage is. We can read out the value of pressure from pressure meter and read out the value of flow rate from oval wheel flow meter which has the measuring range at 101ml／min or 100ml／min. (1)Flow rate without load: if the outlet pressure is beyond zero, the practical flow rate is less than the theoretical flow rate due to the existence of the flow rate leakage, but when the outlet pressure is zero or there is no pressure differential between the inlet and