Gear Pump Designs
Project Background

In 2018, while exploring the world of gears, which have a huge range of applications in nearly every aspect of daily life, I was reminded of the water pump fabrication project that I worked on in 2016. The overlap between that project and my gear research was that a single group of students chose to construct a “gear pump” instead of an impeller pump, nearly every other team working on that project, including mine, chose to build. I was previously unfamiliar with the concept and it intrigued me especially because that group’s prototype performed so well.

There exist today many versions of gear pumps, each with its own set of drawbacks and strengths. The three main pumps that I am interested in are internal, external and cycloidal gear pumps. Internal are constructed with an internal ring spur gear with a smaller spur pinion inside of it that mesh together and force the fluid to travel in a circular motion and be squeezed out at the end of the circle. They rotate at different rates because of their different number of teeth and have different central axes in order to mesh. In combination with a spacer that prevents fluid backflow, these two gears, which rotate in the same direction, pull fluid from one side to the other, and then expel the fluid as the gears attempt to compress it while approaching their contact region.

When dealing with incompressible fluids, this effect can be leveraged to produce a consistent and powerful head pressure but can lack in the area of flowrate when compared to traditional impeller pumps. External gear pumps function similarly but instead feature two external spur gears within a cavity meshing and rotating. The synchronized motion of the gears generates a net directional flow in one direction around the outside of the cavity and an opposing net flow in the middle. However, the fluid flow through the center Is largely inhibited again by the meshing of the gears, allowing the pump to function with a much larger net flow around the outside and barely any backflow through the meshing teeth.

I find cycloidal gears quite interesting and have recently discovered just how much there is left to learn about them and other real-world applications of cycloidal geometry. The two main places that I have heard of cycloidal pump use are in hospitals for fluid pumping, I assume because it is a far less turbulent alternative for impeller pumps and does not easily experience cavitation, (or the creation of air pockets), and large oil pumps. Cycloids, trochoids and involutes have been the most interesting and educational rabbit hole that I have fallen down for a long time. Their wealth of unique properties have me convinced that we are still not done discovering practical real-world applications for them, and I am excited to work towards discovering such opportunities.

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