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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That’s simply thermodynamics.
The carnot efficiency is the maximum possible efficiency you can reach when converting heat to mechanical energy, and that depends on the temperature difference between your hot and cold basin (the energy is “harvested” by making heat flow from hot to cold and forcing it to move mechanical parts on the way).
Imagine it like trying to harvest the energy of a river, you can never harvest all energy because that would stop the river entirely wich prevents new water from reaching you
So since fuel has a specific temperature at wich it burns, and the outside of the car is regular outdoor temperature and is never extremely cold you have a fundamental limit on your efficiency.
And stuff like coal powerplants gets close to that efficiency topping out at ~40% efficiency by using elaborate means like preheating your medium over a dozen stages with exhaust air. (And you can reach over 60% in combined cycle, but that’s basically using a second higher temperature process on top)
In a car you don’t have space for such an elaborate system of pipes, so you lose extra energy by having your exhaust air being hotter than the outside air (wich is all extra energy you didn’t spend on driving).
So the only way to increase efficiency would be a larger engine (with more preheating) or a higher temperature compared to the outside
That’s simply thermodynamics.
The carnot efficiency is the maximum possible efficiency you can reach when converting heat to mechanical energy, and that depends on the temperature difference between your hot and cold basin (the energy is “harvested” by making heat flow from hot to cold and forcing it to move mechanical parts on the way).
Imagine it like trying to harvest the energy of a river, you can never harvest all energy because that would stop the river entirely wich prevents new water from reaching you
So since fuel has a specific temperature at wich it burns, and the outside of the car is regular outdoor temperature and is never extremely cold you have a fundamental limit on your efficiency.
And stuff like coal powerplants gets close to that efficiency topping out at ~40% efficiency by using elaborate means like preheating your medium over a dozen stages with exhaust air. (And you can reach over 60% in combined cycle, but that’s basically using a second higher temperature process on top)
In a car you don’t have space for such an elaborate system of pipes, so you lose extra energy by having your exhaust air being hotter than the outside air (wich is all extra energy you didn’t spend on driving).
So the only way to increase efficiency would be a larger engine (with more preheating) or a higher temperature compared to the outside
Ice engines use small explosions and not heat to turn the crankshaft. The excess heat is just a result of that. You can’t really use that for turning the wheels without having a separate engine that turns heat into movement.
Ice engines use small explosions and not heat to turn the crankshaft. The excess heat is just a result of that. You can’t really use that for turning the wheels without having a separate engine that turns heat into movement.
They’re not. We hit up to 55% efficiency on our slow speed diesels.
To start, heat is what’s going much of the work. You’re heating up gasses, which forces them to try to expand in a limited space, creating pressure.
Ideally you’d want to NOT cool the engine. If the cylinder walls were the same temp as the combustion gasses, you’d have no heat lost into the walls and it would basically all go into expanding the gasses therefore into driving the piston. However, that’s not realistic with modern materials. There has been some research into ceramic engine blocks though.
Car engines are also tiny, you have a lot of surface area for a small combustion volume. Lots of surface area, plus having to cool that surface area, means lots of heat energy lost.
They’re not. We hit up to 55% efficiency on our slow speed diesels.
To start, heat is what’s going much of the work. You’re heating up gasses, which forces them to try to expand in a limited space, creating pressure.
Ideally you’d want to NOT cool the engine. If the cylinder walls were the same temp as the combustion gasses, you’d have no heat lost into the walls and it would basically all go into expanding the gasses therefore into driving the piston. However, that’s not realistic with modern materials. There has been some research into ceramic engine blocks though.
Car engines are also tiny, you have a lot of surface area for a small combustion volume. Lots of surface area, plus having to cool that surface area, means lots of heat energy lost.
There have been proof-of-concept ICE/Steam hybrid cars that inject water to the cylinder on the fourth stroke, which then bursts into steam for another push, but they aren’t realistic for production (injecting water to your cylinders will only f••k up your engine *badly* in a short amount of time).
There have been proof-of-concept ICE/Steam hybrid cars that inject water to the cylinder on the fourth stroke, which then bursts into steam for another push, but they aren’t realistic for production (injecting water to your cylinders will only f••k up your engine *badly* in a short amount of time).
Expanding gas from combustion moves a piston up which then translates to the car moving.
Imagine the piston as a cube, and only one side is able to move when the gas expands. The gas interacts with every wall but only one moves, so only 1/6 (0.17) of the interactions results in motion, the rest result in heat. You can improve the efficiency by changing the pistons dimensions, but you are inherently limited by needing to contain the expanding gas.
The waste heat can be used to warm the car’s interior, and a catalytic converter needs the waste heat to reach its operating temperature.
Expanding gas from combustion moves a piston up which then translates to the car moving.
Imagine the piston as a cube, and only one side is able to move when the gas expands. The gas interacts with every wall but only one moves, so only 1/6 (0.17) of the interactions results in motion, the rest result in heat. You can improve the efficiency by changing the pistons dimensions, but you are inherently limited by needing to contain the expanding gas.
The waste heat can be used to warm the car’s interior, and a catalytic converter needs the waste heat to reach its operating temperature.
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