The discussion revolves around calculating the power output of the Lockheed Martin F-35 Lightning II's engine, specifically focusing on the complexities of measuring power in jet engines compared to internal combustion engines. Participants explore the implications of thrust specifications and the challenges in defining power in different contexts, including theoretical and practical considerations.
Participants express differing views on the applicability and usefulness of measuring power in jet engines compared to internal combustion engines. There is no consensus on a definitive method for calculating or defining power in this context.
Limitations include the dependence on specific definitions of power and thrust, as well as the unresolved nature of how to measure power in a hybrid engine system like that of the F-35.
A jet is internal combustion too, but I think you are referring to engines like car engines: they have an output shaft. They output mechanical work.koolinoor said:How come internal combustion engines have power specified?
What about when the Mustang is sitting still on the hill and revving the engine against the clutch to hold still?And this one also, has Force specified, but no power. It doesn't make sense. I mean, I get the fact, that 99% of the chemical energy is probably just wasted, compared to more effective dynamics, but still.. Ford Mustang's engine's power is 157 kW either its going up or down the hill..
Force and shaft output power are easily measured.Where do they get these numbers?
It isn't that it is difficult, it is that it is not applicable.And why is it so difficult to come up with one for this case?
No, it isn't absurd. But it may not be terribly useful either. Again, consider the Mustang hovering on a hill with its clutch. What is the power output of the car? The engine? Does it matter?koolinoor said:say F-35 weights 15 tons * 9,8 its ~ 147 kN..
more or less similar amount.
and the oxygen molecules potential energy is what forces the emission of gas from the turbofan to lift the plain.
then if the plane moves upward 1m/s, can You say, that the power is 147 kW?
its absurd, isn't it?
That would be another way, yes. If you knew the airflow volume, velocity and pressure you could figure out its power. But that answer will be different from one based on the speed of the plane. So which one do you think is more useful/relevant?but say it wouldn't be an open system, but the gas is output to a barrel. what would be the power then?
is there any way of figuring that out?
It can be, it's just not necessarily all that useful.If the shaft output power can be measured, why can't the turbofan output power be measured?