I read that the velocity of the air is increased at the nozzle guide vanes of a turbine before it actually hits the turbine blades, then compresses, and the process repeats. My question is, what’s the reasoning behind this? The way I’m thinking of it is like this:
Let’s compare compressed air to a sumo wrestler.
And then let’s compare just a normal guy.
If the sumo wrestler (compressed air) runs at you with a somewhat slow speed, he’ll apply a lot of force to you, but if a normal guy runs at you with a much faster speed, you’ll feel a lot of force too. I’m wondering where the logic is behind this, because can’t the same force be applied both as compressed air and sped up air if both mass and velocity contribute to momentum?
Thanks
In: 1
Jet engines work by accelerating gas, which pushes the engine forward. Burning fuel and oxygen creates an enormous volume of hot gas, which expands in whatever direction it can. Directing this gas through a tapered nozzle optimizes its velocity to produce maximum force for a particular volume of gas.
It does’t really matter how fast the air travels prior to ignition. What matters more is how compressed it is, because more compression means more mass available to feed the chemical reaction that generates the gass that actually moves the airplane.
In fact, the process of slowing intake air actually aids compression, which helps the engine produce more thrust.
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