Designing an Electric Ducted Fan
How I spent a month trying to design an EDF
With time on my hands thanks to classes ending for the summer, I wanted to try my hand at a simple yet rewarding personal project. My interests always lie within propulsion technology, and the most accessible of that to me was the EDF. My design team, MachWorks, had some small electric motors lying around that I wanted to play with. This actually spawned as a side note of wanting to play with the larger motors we have, but still.
V1
To start, I simply want to make a fan that could be placed on the front of the motor. Initial considerations were to make something that could work but likely won’t and also won’t damage the motor. Verson 1 of the fan was bad. It didn’t product much thrust, drew a ton of power, and was loud. The blades themselves had a simple symmetric profile and were angled at about 45deg. I immediately wanted to improve the design to see if I couldn’t get more thrust out of the small motor.
V2
V2 used proper airfoils, although they were still angled poorly. I spent some time utilizing my knowledge from my recent class on aerodyanmics and compressibility to find the best possible angle for the airfoils. This was done by plotting the coefficient of lift (Cl) against the coefficient of drag (Cd). I also improved the inlet cooling geometry as the motor was getting quite hot during some longer runs.
The fan, while being significanly better than V1, was still not great. I made the change to have two airfoil profiles, one at the root and one at the tip. My thought was to have an airfoil optimized for each the root and tip angles. This turned out to perform much better than the previous designs. Changes were also made to the inlet cooling section.
V3
V3 included making the housing of the fan better. The initial design was mostly eyeballed but I took the time to properly size and dimension things. I also make an aerospike to place at the rear of the fan in hopes of smoothing airflow past the fan. This seemed to work nicely.
V4
V4 included a complete redesign as I had realized a lot of my initial design philosophy was flawed. The main issue was the motor I was using was far too small for such a large fan (100mm diameter). I start from scratched, used new airfoils, made the whole thing smaller and most importantly made the fan lighter. This meant removing all the cooling geometry as it wasn’t performing as well as I had planned. I also make the blades thinner by reducing the tip size. This helped immensely as the fan was quieter and could run longer without heating up. It also produced the most amount of thrust of any of my designs. That being said it was still a long-shot from commericial options.
My plan for this project started off as tinkering and evolved into several designs. There was a time during development where I had considered designing my own aircraft to put the fan on, but other commitments drew my attention. I would still like to make my own plane, and make this fan better, but other projects that I am working on have proven more enjoyable and more fruitful.