I’m reading though the Rolls-Royce jet engine book and it states:
“With Vjet fixed at Mach 1, the new term for pressure thrust allows thrust to be increased by raising exit pressure”
My question is: If velocity can no longer be increased (this is in a choked scenario), then how can an increase in exit pressure increase the thrust? I see how this works in the equation, but it just seems rather counter-intuitive. I thought an increase in pressure meant a decrease in velocity? It also then says that by running the engine hotter, the speed of sound can be increased. So Mach 1 is no longer really 1234.8 km/h?
Another question I have, is that if Vjet (exhaust) is fixed at Mach 1, how is the exit pressure meant to increase? Hasn’t the critical pressure ratio already been reached?
Thanks
In: 2
For every action there’s an equal and opposite reaction. Thrust is a product of mass not pressure. If you’re pushing tons of air backwards very fast you get pushed forwards. You can push a miniscule amount of air backwards at the same speed and pressure but you’re not going anywhere.
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