Why not use an oxidizer on jet engines, wouldn’t it provide better efficiency/power output?
In: Engineering
My thought was, even if only for part of the flight, on a commercial airliner, they could get more miles per volume of fuel consumed, even temporarily, with an oxidizer.
No.
For starters, it would involve carrying the oxidizer along with you, rather than grabbing it from outside the craft. Oxidizer regardless of form is going to weigh quite a lot.
The compression and expansion of the air is also driving the engine. With rockets it’s only the combustion.
This is why rockets only last for minutes, whereas jets can fly for many hours.
Because carrying thousands of liters of an oxidizer is worse than using the oxygen in the air which is already present and is easily usable in every conceivable way. Why would you make a plane larger and heavier (thus requiring even more fuel) just to carry something that’s already all around you and you can use? It’s like bringing a bathtub full of water with you to a pool. Why are you gonna lug all that water to the pool? The pool already has all the water in it.
Because carrying thousands of pounds of liquid oxygen would cause the craft to have to be significantly larger and use more fuel because of that. It would also make the thing more of a moving bomb.
The air to fuel ratio for jet engines from what I gather is around 60:1 so it would take A LOT of oxidizer.
It would not improve efficiency. In fact, you’d roughly halve your efficiency. This is because you need twice as much ‘fuel’ to get the same energy. Also, your engines are definitely going to melt. Lastly, power output is not at all the limiting factor on jet engines. We can make some wicked powerful engines, but they aren’t as efficient. Typically low-bypass turbofans or turbojets provide radically more power than the high-bypass engines you’re probably used to seeing, but they ‘waste’ most of that energy by yeeting their exhaust way faster than they have to. They become more efficient at higher speeds, as they *have* to yeet their exhaust faster, but at higher speeds drag becomes more of a problem. As such, jet engine power output is currently very well optimized for efficiency.
Increased complexity and increased weight of the engine and fueling systems. The tradeoff just isn’t worth it, particularly considering the atmosphere already provides plenty of oxidizer.
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