I read that a massive portion of usable energy is wasted and turned to heat instead of being used to turn the crankshaft — would there be like any way of reducing the heat/cooling the engine so you could get 50-70% thermal efficiency?
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Oh I gotchu.
So ICE’s rely on combusting to operate, and this combustion generates heat as its primary output mechanism. That’s in fact the thing we’re taking advantage of.
Pistons get pushed because the air inside of the space rapidly expands in the heat, generating the pushing motion we use to propel us forward. The goal of the thing is to make heat.
So actually we want the heat in the first place!
The issue is, and probably what you’re referring to, is that the heat doesn’t all go to expand the air inside the piston – some of it gets lost to the block and surrounding area. Most of it goes out the tailpipe after being used once (assuming no turbo).
We can cool the block sure! But that’s not really making the engine more efficient, that’s just increasing the thermal load of the material since it being colder just means it can absorb more heat before melting. If we also cool it actively using some sort of coolant than we need a water pump to circulate that coolant, which you attach to the crankshaft; which means that you’re wasting more energy generated to cool the system.
Now you can build the engine out of a material that’s more insulative; but then the issue is that your block will melt quite quickly. You want the cold (relatively speaking to you and I it’s still very hot) to keep the thing going. If you imagine a fictional exercise where you’re able to lose no heat in a piston, it won’t be long before the inside becomes as hot as the surface of the sun. And there’s no known material that could support that.
Turbo chargers are an interesting way to increase thermal efficiency though! They use the hot air generated to passively spin a turbine that allows you to take in more air that further increases the combustion!
Unfortunately at the end of the day burning things for fuel just isn’t all that great. Electric vehicles are far better about this because their primary mechanism isn’t heat, but electromagnetism!
An electric motor works by sending a current through a magnetic; rapidly switching its polarity enough to spin with quite a bit of force. It’s wildly simple and far more efficiency than directly generating heat for fuel!
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