FSAE Motor Cooling System & Test Cart
Background:
In the Fall of 2019, the Northeastern University Formula SAE Electric team was trying to build a car to compete in their first competition as a club in the spring of 2020. This club centers around designing, building, and racing a small formula style car in an autocross style environment. There are a large number of mechanisms and subsystems required for this, so some of them were semi-outsourced to Capstone groups (senior design project groups) to speed up the process. My group and I designed and tested the cooling system for the electric motor that drove the car.
Skills Utilized:
Fluid system design - sized pump to accommodate pressure drop across radiator, motor, tubing, etc.
LabView - recorded and displayed temperature and pressure data across time to measure performance of each iteration of the system.
Sensor selection/calibration - sensors were selected with the appropriate range, precision, voltage, and price. They were then calibrated to ensure the data we collected was accurate.
Technical writing - since this was a Capstone project, we created presentations and reports detailing our findings in a concise and technically accurate way. This project in particular taught me a good balance between providing ample information and being concise.
Keep scrolling for a more in depth look at the project.
Design Objectives
The design must:
Keep the motor within its desired operating temperature range throughout the course of a race
Be reliable enough to need minimal maintenance, as our whole capstone design team was graduating and would not be able to support
Must be flexible enough in geometry to allow installation in a yet to be determined car configuration
Constraints
The cooling system must keep the 100 kW motor within its desired operating temperature range (<~50°C)
The system must run off a 12 V car battery
The system must be mountable to the chassis without being unnecessarily unbalanced or drag inducing
The lack of complex manufacturing ability within the timeframe ruled out any custom radiators, meaning they must be COTS
A 3D modeled representation of the radiator’s desired placement on the then-existing chassis. Additional components such as the pump would be located under the radiator.
Approach
The main challenge of designing this system was choosing the right components that would do the job we needed in the most efficient way. A pump, radiator, and fan combo were selected to fit the chassis and meet the cooling requirements while still being as light as possible.
•Developed test cart to quickly evaluate different radiators, pumps, and fans
•Included pressure and temperature sensors before and after the radiator to measure pressure and temperature drop
•Utilized a computer power supply to supply 12V to both the pump and the fan(s) and 5V to the thermocouples
•LabView and a SensorDAQ were used to capture data from the thermocouples over time and plot the rise in temperature as the heating elements provided an approximation of the motor’s potential waste heat
Two pressure gauges (left), a flow meter (right), and two thermocouples (hidden) were utilized to track the data of each test across its duration. This was done by manually checking the pressure gauges (which did not change significantly over the course of the test) and collecting temperature over time data using the SensorDAQ (upper right). A typical computer power supply was used to provide the required power for both the pump and the fan on the radiator.
Results
The system performed well under lab conditions. We found a suitable combination of components that would cool the motor while still being light and compact. Below you can see a PDF of our presentation poster, which has some testing result graphs that show the system in different conditions.
Unfortunately, at this point, the car was in no condition to do any testing on. There were too many unfinished subsystems to be able to test our cooling system on any meaningful scale. In another stroke of bad luck, development halted shortly after due to the beginning of the COVID-19 outbreak.
Lessons Learned
The biggest takeaway from this project for me was a functional knowledge of how simple fluid systems work. Dealing with issues such as leaks, cavitation, flow restrictions and head loss, and galvanic corrosion all are something I only had a tangential understanding of before starting this project. Being able to find some values of the system through the use of fluid mechanics knowledge and being able to see those calculations be reflected in our actual product was an eye opening experience for me as well.