Flywheel design. Inertia dyno for 745 KW engine.

[berko1]

Hello again,

I am currently designing a flywheel for a 745 KW engine inertia dyno.

Basically my design requirements are so:

Max RPM: 530 RPM (=55.5 rad/s)
Flywheel Diameter: 1.7 meters
Time needed to accelerate: 60 second (to max rpm)

I need help determining the mass of the flywheel.

My calculations and way:

Power=745 KW

ΔE=P*t=745*60=44700 KJ

Inertia for a solid disc (flywheel) = 0.5*m*r^2

Energy in flywheel = 0.5* (0.5*m*r^2)*ω^2

Isolate the mass:

m= (4*Energy) / (r^2* ω^2)= (4*44700) / (0.85^2*55.5^2) = 80 tons.

80 tons seems way off, I've gone over my calcs a few times and haven't found my problem.

I appreciate any assistance!

 

[mfb]

45MJ is a lot, and 530 RPM is slow.

Cross-check: 1/4*m*v^2 = E where v is the velocity at 1.7m/2 radius:
1/4*80000kg*(1.7m*55.5/s)^2=44.5MJ

Your result looks correct.

Do you want 745kW over one minute, or maybe a lower charging power and 745kW over less than a minute to discharge?

 

[berko1]

mfb:

Thank you for your reply, i guess that these are the facts and i'll have to face them and consider "bending" some requirements.