airplane engine and power/torque curves

[Leonidae]

Since they're relatively low revving engines ( speaking of WWII era fighter engines ), where would they cross, and on what RPM the peak power and peak torque reside?

 

[Greycap]

Shedding some more light for those that don't know the figures we're talking about rev limiters of 2400 rpm (DB601, Hispano 12Y) to 3000 rpm (V-1710, RR Merlin) here. There were exceptions like the Sabre but it was a freak engine anyway.

 

[Boz Mon]

I would think they wouldnt cross because they dont rev to 5252RPM. I'm pretty sure that all piston engine torque/hp curves cross at 5252RPM no matter what.

 

[Keef]

They wouldn't cross. The math always works out to 5252, even if it doesn't rev that high, and even if it might idle above that. If you did the math and plotted points to extend the lines, both curves would meet at a point at 5252.

 

[PAPPACLART]

The lines should never cross, but will only cross if the graph is plotted on different increasments

Practice on a spreadsheet.

Torque x Engine speed / 5252 = Horsepower

Power / Engine speed x 5252 = Torque

 

[wfooshee]

The number is a constant, but changes depending on the units. The 5252 is for Lb-Ft and HP (American-style). If you use watts and newton-meters it's a different number, but still a constant. Watts and newton-meters will draw different curves than HP and lb-ft, but they still cross at the constant RPM, whatever the constant is for your units.

What that tells you about slow-turning engines, (aircraft, trucks, marine, etc.) is that they get big torque numbers compared to their HP numbers.

And if you look at current F1 engines, you see the same thing the other way 'round. Huge HP numbers considering the displacement, but not so big torque numbers. Revs, baby!

 

[Leonidae]

Good to hear. and since these engines developed a lot of hp, I assume that the torque is equally colossal.. after all, we're talking of huge displacements and long stroke engines..