New thermoelectric generator converts vehicle exhaust heat into electricity, boosting fuel efficiency
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If they only have something to bump off of in a limited number of directions, they’ll take off in the other direction. (For instance, in a rocket engine, we make a lot of molecules really, really hot and then surround them with barriers in every direction except the one we want them to zoom out in.)
I'm sorry, but this is also wrong too when related to your description of the heat requirement part.
We don't make a rocket engine hot to make it work. It becomes hot as a byproduct of what we really want which is liquid/solid fuel and oxygen in liquid/solid form, which take up very little space. We make them take up a LOT of space and by becoming high speed expanding gases. We aim these gases which take up a lot more space (and are moving very fast) out the back of the rocket in a desired redirection to take advantage of Newton's Third Law of Motion. The "hot" happens because its the fastest/easiest way to change the liquids/solids into a gas is by ignition/fire.
There's examples of engines/thrusters that are room temperature or even crazy cold that produce thrust to move a vehicle. There are toy rockets that work on pressurized room temperature water, 3rd law physics still applies here. There's also nitrogen thrusters which operate at -50°C. There are even ion thrusters that get as cold as -100°C.
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It's pretty much like billiards. They just bounce. Different chemicals (types of molecule) are different phases at different temperatures e.g. nitrogen is a gas at room temp, water is liquid. Stuff that's a gas at room temp just has less bonding forces (and often mass) than liquids or solids. So they don't take as much heat to go fast. There's a lot of heat even at room temp, and even at -40deg. The temperature for nitrogen to sit in one place is -210C or -346F.
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The turbo does indeed increase exhaust pressure, and therefore extracts some work from the crank but it’s extracting significantly more from the high pressure of the expanded hot gas.
I'll admit I'm at the edge of my knowledge here, but are you saying that if we were increasing the pressure in the cylinder from, say pure nitrogen (or another inert), instead of atmosphere (which contains oxygen), and we kept the same amount of fuel from natural aspiration, we're still get the majority of the benefit of turbocharging even overcoming the parasitic portion of extra energy needed during the compression cycle and the exhaust cycle against the turbocharger impeller?
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OMG they’ve actually introduced the 2025 Turboencapulator.
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The exhaust gases get pushed
The "pushing" (exhaust stroke) isn't particularly relevant.
When the valves close at the beginning of the compression stroke, the pressure in the cylinder is atmospheric: zero psig. The valves don't open until the piston has risen (compression) and fallen (power) again. Without combustion, the pressure at the time the exhaust valves open is again at atmospheric. The gasses were compressed, and re-expanded.
With combustion, the pressure at the bottom of the stroke is substantially higher than atmospheric: the combustion event has radically increased the pressure of those gasses. At the end of the power stroke, just before the exhaust valves open, the pressure inside the cylinder is still extremely high.
It is the expansion of those gasses - not the "pushing" of those gasses - that drives the turbo.
I think it might be beneficial to think about the next evolution in aircraft propulsion. The turbocharger operates by expanding gasses through a power turbine, and using that energy to drive a compressor turbine. Remove the cylinders and pistons from the path, carefully tune those turbines, and you have a turbojet.
If the pistons are "pushing" the turbocharger, the turbojet would be impossible. It is the expansion of the gasses, not the displacement of the pistons, that drives the turbocharger.
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It being a diesel, it didn't need to fire sparks though.
That's cheating
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No. The heat of combustion increases the gas temperature. But this temperature increase is relative to the mass of the gas. The heat is relative to fuel/oxygen mass combusted. (Combustion energy + Ideal gas law)
Add mass without adding combustion, you get lower pressure and temperature out. So you get less boost from the turbo and make more work for the compression cycle.
The major point of the turbo is to use wasted heat to add more oxygen by packing more air in. So it's a bit of an odd question to answer. The point is there's a lot of energy wasted in a naturally aspirated engine's exhaust. Turbos mostly use that wasted energy, and not power from the crank.
Oh yeah, the turbo is going to have an efficiency ratio for converting exhaust pressure into boost. So that added backpressure on the exhaust is going to be offset in the intake stroke by that ratio. Not important to the point, hat a tidbit. These things are so complicated lol.
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This concept isn't new either. Factories have been using very similar methods to use the heat of the exhaust gasses to power the sensors and whatnot on top of their smoke stacks for some time now, for example.
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MGU-H works very well, and they're only getting rid of it in 2026. Mainly to keep new upcoming F1 engine manufacturers happy as they don't have experience in MGU-H systems.
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even overcoming the parasitic portion of extra energy needed during the compression cycle and the exhaust cycle against the turbocharger impeller?
Let's assume the contrary. Let's assume it can't. Let's assume the turbocharger is a net drag on the engine, and any gains are only from enabling the engine to burn more fuel. If this is all true, then the turbocharger should not be able to function without the reciprocating engine. Without the "push" from the pistons during the exhaust stroke, the turbo shouldn't be able to turn.
If we can show that the turbo can not only spin without the piston engine, but that additional energy can be harvested, we will have disproven this assumption.
So, let's get rid of the pistons. Plumb the intake manifold directly to the exhaust manifold. We have one combined intake/exhaust manifold. We stick a couple spark plugs into that manifold and turn it into a combustion chamber.
Now we have air passing through a compressor turbine, into a combustion chamber and then through an exhaust turbine. Sound familiar?
Engineers discovered that some turbos were capable of producing more power than the engines they were attached to. They discovered that the reciprocating engine was a drag on the turbo.
That discovery gave us the jet engine.
