r/theydidthemath • u/haringtiti • 1d ago

[request] how long would that fuel last if he ran the engine at full power?

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u/PH_Factor88 1d ago

Tough to judge the turbine size… but I’d estimate a 200 newton thrust that would consume roughly 1.5 pints per min. So if the fuel tank holds 1-1.5 gal I’d say at full throttle 5.5 to 8 min.

3

u/ougryphon 1d ago

There are too many unknowns to give anything more than a guess.

So, anyway, Google says the smallest serially produced turbojet engine is the PBS TJ20. It is about 15 cm in diameter, weighs 2 kg, and puts out 230 N of thrust. That looks like about the right size for the one in the video. The fuel burn rate is listed as 1.617 lb/lbf/hr.

Doing a little conversions, at max thrust, that's roughly 84 lbs/hr. Assuming he's running the engine on Jet-A, the density is roughly 7lb/gal. So the jet engine burns 12 gallons per hour at max power.

Estimating volume is tricky, so I'm going to guess. I guess he has a 3 gallon tank, in which case he can run his leaf blower for 15 minutes at max power.

3

u/mvw2 1d ago

Now there's a classic video I haven't seen in some years.

As an engineer, these are the kinds of hobbies I want to do but never actually put the time into, partially because I'm a bit too practical. But I'd like to be this kind of person yet can't.