Giselle Onofre
Projects
Air Engine
Thermal Fluid Science 2019

Skills: CAD Modeling, Machining

At Rowan University, I took a 6 credit course called Thermal Fluid Sciences. It is a combination of three courses: Heat Transfer, Thermodynamics, and Fluid Dynamics. A portion of this class is dedicated to practicum. My practicum team and I were tasked to build an air engine with the following requirements:
  • Should reach at least 1000 RPM
  • Must displace 50+/-3cc of air per output shaft revolution
  • The cost of outsourced materials should be no greater than $60
  • The engine should be able to run for at least one minute
  • The engine must connect to the compressed air source through 1/4' plastic tubing
Flower Render
Research and Design Phase
The air engine was designed to be a challenging project from the start. As my professors described it "You'll be designing an air engine before you know any of the thermo and fluid concepts behind it". My team and I researched various air engine designs and I reached out to former students about their designs and what worked for them. After a week of research, we settled on a double acting scotch yoke design on the advice of my former classmate Caio. In my research, I also consistently came across former students on the importance of adjustable timing, so to account for this in our design we created a timing wheel to ensure that our high pressure air would be acting at the necessary up and down strokes.
Flower Art
Flower Art
Flower Art
SolidWorks Modeling, Assembly, and Drawings
After getting a conceptual design down, we transferred this into a CAD model. We made an assembly from all of our parts to ensure we achieved proper timing between the valve and power assembly. We made drawings for every part we planned to machine and included instructions on how we would machine the part so we didn't go into machining aspect of this project blind. This also gave us a clear idea of the tolerance level we wanted to achieve with each part and how we would go about it.
Flower Render
Final Results
Unfortunately, due to the limited number of machines available to the teams and the breakdown of the university's waterjet we didn't get the chance to complete power testing in the spring semester. As far as improvements go, if we had more machines available to us, we would have redone our spool valve piston. For our valve assembly, the attachment point between our spool valve piston and our sliding yoke wasn't secure. This part was made mainly on the lathe from Delrin and took us about a week to make due to the tolerancing, and its complicated geometry made it a difficult milling process. We were nearly successful up until we reached the final machining process on the arbor press. One side of our piston sheared off when we were press fitting dowel pins. Nevertheless, our air engine was the most successful one for our year. We achieved a maximum rpm of 2940 and at the time it was the 2nd highest RPM record of all time(we've since been surpassed by newer teams). After this project, my professor told us that we could all stop considering ourselves engineering students and consider ourselves engineers instead.
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