The gerotor pump is a rotary positive displacement pump that moves fluid using the rotary motion of the pumping elements.
The name of the gerotor pump comes from the generator rotor.
Gerotor pumps are similar in operation to traditional internal gear pumps but swap the position of the drive and driven gears.
The number of teeth in internal gear is one less than the number of teeth in the outer gear.
Generally, the internal gear of this pump is the rotor or the driver gear and the external gear is the outer or driven gear. But in some cases outer gear is used as driver gear such as applications like gear train lubrication applications (transmissions, axles etc).
The gerotor pump is efficient, compact, and quiet. The simple design, with few moving parts, is ideal for a wide variety of applications including hot cooking oil filtration and automotive applications like fuels, lube oils, and transmission fluids.
The first gerotor was developed by Mayron F.Hill in 1921. Gerotor pumps are used in various industries and are produced in various shapes and sizes for various purposes.
Parts Of Gerotor Pump:
1) Inner Rotor:
It is the inner rotor of the two rotor present. This rotor has teeth on the outer circumference.
2) Outer Rotor:
It is the outer rotor of the two rotor present. This rotor has teeth in the inner circumference. It is also known as an idler.
It is the outer cover of the pump which encapsulates the rotors.
4) Inlet Port:
It is part of the pump from which the fluid enters the pump. It is also known as Suction Port.
5) Outlet Port: Or Discharge Port:
It is part of the pump from which the fluid leaves the pump. It is also known as the Discharge Port.
Working Of Gerotor Pump:
Both rotors are in constant mesh with each other and both rotate continuously.
If there are n number of rotors in the inner rotor, there will be n+1 number of rotors in the outer rotor.
The inner rotor is a little off-center i.e center of the inner rotor is at some distance from the center of the outer rotor.
One tooth of the inner rotor is in complete mesh with one tooth of the outer rotor and there is a gap between the other teeth of the inner rotor and the teeth of the outer rotor.
As the pump rotates, these gaps expand on the inlet side and contract on the outlet side.
When the rotor starts rotating, the volume of the space between the teeth of the outer and inner rotor changes in each step i.e volume of each partition change continuously.
When we see in a clockwise or anti-clockwise direction the volume of the gap between the two teeth of the inner and outer rotor first decreases and then increases and again decreases.
When the rotors start rotating, a gap is created near the inlet of the pump due to which a low-pressure zone is created between the two rotors near the inlet.
A suction effect is caused due to the low-pressure zone created and fluid is sucked through the inlet and enters the gap between the inner and outer rotor and hence enters into the pump.
Then as the rotor rotates further, the gap between the teeth of the two rotors increases, and the gap is filled with fluid.
When the volume of the gap reaches a maximum, it then starts decreasing. As the volume decreases, the volume of fluid inside the pump decreases and the pressure of the fluid decreases due to compression.
The teeth of the inner rotor are always in contact with the teeth of the outer rotor. They have a close tolerance with each other. So, when fluid enters a chamber in gerotor pump it remains in that chamber while the volume increases and decreases and does not leak into another chamber. Hence, the backward flow of fluid is not possible in gerotor pump. The liquid continues to travel through the pump, between the teeth of the gear-within-a-gear principle.
As the fluid is sealed in a chamber and cannot go forward or backward out of the chamber. So, the seal forces the liquid out of the pump through the discharge port.
We get a uniform flow using the gerotor pump and the flow rate of the fluid by this pump is constant.
Advantages of Gerotor Pump:
1) It is a very high-speed pump.
2) The operation of this pump is very silent and does not create much noise.
3) This pump operates well in both directions.
4) This pump is very good at handling high-viscosity fluid.
5) It provides constant and even discharge regardless of a pressure condition.
6) It has only two moving parts.
7) It has only one surfing box.
Disadvantages Of Gerotor Pump:
1) This pump has lower pressure capacities compared to other pumps and hence cannot be used when high pressure is required.
2) It cannot be used to pump fluids that contain abrasive particles.
3) These pumps have fixed clearances.
4) There is overhung load on shaft bearings.
5) These pumps have limited flow rate ranges and cannot be used in applications that require high flow rates.
6) No solid particles are allowed as solid particles can damage the pump.
Applications Of Gerotor Pump:
Gerotor pumps are used to pump the following:
* Light fuel oils.
* Lube Oils
* Cooking Oils
* Hydraulic Fluid
* It is used in oil pumps and fuel pumps
* It is also used in high-speed gas compressors.
* It is used to deliver lubricating oil to machinery components such as gears, bearings, and other moving parts.
* It is also used to transfer viscous food products like honey, chocolate, and syrup.
Construction materials of Gerotor Pump:
Head and casing: Cast iron.
Shaft seal: Lip seals, component mechanical seals
Precautions on using Gerotor Pump:
1) Keep the working fluid clean as the shaft bearings are lubricated with the same fluid that is pumped.
2) The manufacturer datasheet should be checked properly for the maximum side load that can be applied on the drive