Gear pump is a common positive displacement pump, and its working principle is based on a pair of meshing gears. The working principle of a gear pump is mainly based on the change and movement of the working volume formed between the pump cylinder and the meshing gears to transport liquid or increase its pressure.
Structural composition
A gear pump usually consists of two gears (a driving gear and a driven gear), a pump body, front and rear covers and other components. The axles of the two gears are respectively installed in the bearing holes on the two pump covers, and the driving gear shaft extends out of the pump body and is driven to rotate by a motor or other external drive mechanism.
The pump body and the front and rear covers together form two closed spaces, which are separated by the meshing line of the gears and serve as the suction chamber and the discharge chamber respectively.
Working process
Suction process: When the gears start to rotate, the spatial volume of the gear disengagement side (i.e., the suction chamber) gradually increases, forming a low-pressure area. At this time, the liquid is sucked into the pump chamber through the inlet pipe to fill the increased space.
Discharge process: As the gears continue to rotate, the spatial volume of the gear meshing side (i.e., the discharge chamber) gradually decreases, and the pressure increases. Under the action of pressure, the liquid is pushed out of the pump chamber and discharged from the system through the outlet pipe.
Seal and pressure
The meshing of the gears ensures the sealing of the pump chamber, so that the liquid is pushed in the pump chamber without leaking into the gap of the meshing gears.
The discharge pressure of the gear pump depends entirely on the size of the resistance at the pump outlet. If there are dampers (such as filters or restrictors) at the outlet, the pump will push the liquid through these dampers and maintain a constant flow until it reaches the mechanical limit of the weakest component in the device.
Flow and speed
The flow rate of the gear pump is directly related to the speed. With the uninterrupted rotation of the drive shaft, the pump will discharge the fluid continuously.
However, due to the small amount of fluid loss inside the pump body (used to lubricate the bearings and both sides of the gears), the pump cannot operate at 100% efficiency. But for most applications, its efficiency is still very high, usually reaching 93%~98%.
Precautions
Gear pumps may generate flow and pressure pulsations and noise during operation. These phenomena may be affected by the design and manufacturing accuracy of the pump and the working conditions.
In order to improve the performance of the gear pump and extend its service life, regular maintenance and care are required, including checking the wear of seals and bearings and replacing damaged parts.
The advantages of gear pumps are simple and compact structure, small size, light weight, good processability, low price, strong self-priming, insensitive to oil contamination, wide speed range, ability to withstand impact loads, easy maintenance, and reliable operation.
The disadvantages of gear pumps are unbalanced radial force, large flow pulsation, high noise, low efficiency, poor interchangeability of parts, difficult to repair after wear, and cannot be used as variable pumps.
Gear pumps are widely used in occasions where liquid transportation and pressurization are required, such as hydraulic systems, fuel systems, lubricating oil systems, etc. In these systems, gear pumps can effectively transport liquids from low-pressure areas to high-pressure areas to meet the working requirements of the system.
