Quote:
Originally Posted by drgondog
So, at 1kt/hr Thrust is near maximum?, at 2Kts the thrust is coming down and at 300kts it is at minimum?
|
In my presentation I used constant efficiency but in real life the efficiency decrease to near zero when the speed is reaching zero and in the other end of scale mach effects start to decrease efficiency as well.
In practice highest thrust is reached at speeds where the plane becomes airborne. Above that thrust start to decrease depending on efficiency and speed (and compressibility).
Quote:
Originally Posted by drgondog
Power is basically constant, Thrust (Force along positive horizontal axis exerted on the stsyem by the engine/propeller combination) is basically constant for this system from V=0 kts and V= 300kts and every velocity in between.
|
Only the first part about power is true, the rest does not hold water at all.
We know that power is the work divided with time:
W = S/t
Where W is power and S is work and t is time.
And further Work is Force multiplied with distance.
S = T * d
So power can be written:
W = (T*d)/t
And therefore the force can be calculated
T = (W*t)/d
And further
T = W/(d/t)
And d/t, distance per time is same as speed V so
T = W/V
And again Power can be also calculated as
W = T*V
In other words, if we assume constant power, the force must decrease when the speed increase.