Originally Posted by
Halcyon66
Strange that a 80 N turbine can produce 130 N running a fan. Considering the losses and running two turbine wheels and then some planetary gearbox or the like for the fan takeoff. Yet you are somehow able to almost double the original turbine core output.
I am assuming the TF-200 would have something to do with the inlet diameter, then if that is that case to get 130 N you would need around ~ 10K W of power to the fan just off the top of my head.
Pretty sure your going to get a lot less than that from a 66 core.
Regards,
You're forgetting turbines are not 100% efficient; much of the kinetic energy is lost as heat.Let's say you have a turbojet and a turbofan that produce equal thrust. The energy needed to get the smaller mass of air going faster (turbojet) is greater than the energy needed to increase the speed of the larger mass of air (turbofan).
Think of it this way. Momentum is mass times velocity. Kinetic energy is 1/2 mass times velocity squared. So kinetic energy is 1/2 momentum times velocity. For the same momentum (the same thrust) your energy goes up in proportion to velocity. You are wasting more energy (and more fuel) just using a jet engine. Of course, there are trade-offs. The jet engine is simpler and cheaper and smaller for the same thrust. But it uses more fuel to produce the same amount of thrust.
This is why no modern full size aircraft relies on turbojets, because they're terribly inefficient compared to turbofans and produce much less thrust per unit of fuel.