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Originally posted by Kano
Hrm, I think the mass flowrate would stay the same. As the mass of the fuel (or whatever you are flinging out the back of the engines) increases. The amount by which it can be accelerated by the engines decreases, as the engines extract no more power from a fuel by it being more massive. This rate of slowing should be inversely proportional to the rate the mass of the fuel/reactionary mass is increasing. Thus the flowrate should remain the same?
Originally posted by greenkoolaid
I would think that eventaully you wouldn't even be able to fling the fuel out the back. The weight of the ship and the fuel itself would be so large that the energy from the combustion wouldn't even be able to move either one. I am not sure what would happen, maybe the fuel would simply get blocked up in the rocket.
Originally posted by Kano
A few interesting points. As the mass of the fuel increases, the energy released by it does not increase in line with the mass. There are still the same amount of molecular reactions occuring, thus the same energy being released.
Now the mass of the spent fuel exhaust (and any other reactionary mass we add to the efflux) is increasing, but the energy released by this fuel is not increasing. As such the velocity of the efflux would decrease. However the kinetic energy imparted to the ship would remain the same, as the reactionary mass is larger and larger.
On a side note, I'm not particularly familiar with the engines on the B-52, but I'd imagine that due to aerodynamic factors it is more efficient to have a slower heavier efflux than a faster light one. Hence adding the water to the outflow, the total kinetic energy remains the same.
Originally posted by THENEO
William,
I said everything,
the rest of you said nothing.
Originally posted by Valhall
Okay, first off, have you address any potential increases in enthalpy due to the molecular/atomic increase of the fuel?
Second, the kinetic energy of the eflux increases with the mass == > 1/2 m v^2 < = = no getting around it.
Third, the BUFF had to have water injection because its original engines were under powered for the ultimate take-off weights it experienced...so they increased the mass of the eflux ==>1/2 m v^2
Originally posted by Kano
Regarding the BUFF engines, it seems the water injection assisted in the transfer of the energy from the fuel into kinetic energy for the plane by a much simpler method than I first suspected. When it vapourises it absorbs excess heat in the engine that would otherwise be wasted.
[Edited on 29-11-2003 by Kano]