Formula for flow rate of gear pump:

Qt= KπD 2m B n×10-6= 2πK D m B n × 10-6 L/min

D - dividing circle diameter, mm; D=mz, mm, z - number of teeth m - modulus m=D/z, mm; B - tooth width, mm; n - rotational speed, r/min; K - correction factor, generally ranging from 1.05 to 1.15.

Flow rate of medium and low pressure gear pump: [take K ≈ 1.06 2 π K=6.66]

Qt= 6.66 Z m2 B n×10-6 L/min

Flow rate of high-pressure gear pump: [take 2 π K=7]

Qt= 7 Z m2 B n×10-6 L/min

Calculate Qt: for standard gears m=De/(Z+2) De - tooth tip circle diameter

For the variable gear m=De/(Z+3)

Factors affecting volumetric efficiency

The impact of plot ratio

1. There are radial clearance (tooth tip clearance), axial clearance (end face clearance), and tooth side clearance in the sealing gap. The axial clearance (end face clearance) of the gear pump has the largest leakage, accounting for 70-80% of the total leakage.

2. Inhalation pressure: When the inhalation pressure decreases, gas is released, and η v decreases

3. Discharge pressure: As the discharge pressure increases, leakage increases and η v decreases

4. Temperature and viscosity: As the oil temperature increases, viscosity decreases, gas precipitates, leakage increases, and η v decreases

5. The speed leakage is not closely related to the speed, but it cannot be too high or too low. If the speed is too high, the centrifugal force of the oil will be strong, making it difficult for the oil to fill the tooth cavity. Vacuum will appear at the tooth root, causing vaporization and affecting suction, resulting in vibration and noise, and a decrease in η v (the maximum speed is limited to below 3000 r/min); The speed is too low and the η v decreases (the speed should be above 200~300 r/min)

The above:Some manifestations of improper use of hydraulic vane pumps