When I was a kid (perhaps around 14), I designed a gas turbine engine for cars using a pair of roots blowers for turbines. The ideas was that the rear blower would have a larger displacement than the front blower (the way turbines actually are).
I theorized that it could be a low rpm gas turbine because the roots blower can work at automotive speeds (that’s why they work on dragsters and tractor pullers). I was concerned about the rear blower since I knew that it would be at exhaust temperature. I suspect this is the big problem for all gas turbines. You need a compressor that can withstand high temperatures and still be efficient.
I also theorized that it would be have any vibration compared to a piston engine. Also fewer moving parts.
I also figured it could have more power since it could also run at higher rpms for more extreme applications. Perhaps could run slower than a piston engine too. All that was just conjecture but to be frank, I’m still a little curious.
I never tried to make one but it dawned on my when I saw this that there may other blower types that are easier to make than a roots.
Here’s the traditional roots blower that I had in my actual design:I noticed that the gear program I got from Matthias Wendel can make a roots blower too. I suspect it’s past the limit for his program but I didn’t try and change any angles and stuff. I think the roots blowers I was looking at had three lobes. It may be fun to actually make a blower to generate vacuum. I wonder if I could get a quieter vacuum pump with a roots.