Have you ever wondered how much potential energy from fuel is lost in gas-powered vehicles? Surprisingly, traditional combustion engines only use about
Your explanation about where the energy comes from with turbochargers sounds wrong to me.
When exhaust gas passes through a turbocharger,
You’re skipping a crucial step here. The exhaust gases get pushed through input of the exhaust gas impeller on the turbocharger by the movement of a piston in the engine during the exhaust cycle. This “work” isn’t free. Its energy that comes from the other pistons on their combustion cycle. If there is more resistance on the exhaust coming out of the engine (which there is to drive the turbocharger impeller), that energy must be added (robbed) by the energy at the crankshaft that ultimately powers the wheels.
The extra boost of power we experience in an engine from using a turbocharger is that the turbocharger allows more oxygen to be put into the combustion chambers (and the engine puts more fuel in at the same time). The extra energy is from burning - - more fuel in the same period of time than without turbocharging. The fuel is the source of the energy, the turbocharger isn’t recovering any energy.
The article is covering technology is actually recovering energy turning heat (thermal energy) back into electricity (electrical energy).
The exhaust gases are at a high pressure after combustion due to combustion heat. 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. It’s not “free” because it’s energy that is usually just wasted in a naturally aspirated engine. There are many examples of engine configurations where a turbo is used to boost efficiency by reducing displacement.
There were systems on old aircraft engines which used exhaust power recovery turbines geared directly to the crank. Those wouldn’t physically function under your concept.
The increase in manifold pressure doesn’t just increase oxygen in the cylinder. It also increases the manifold pressure, or the total mass of gases. The increase of oxygen does allow for more fuel and total energy in the ignition event but the extra inert gas also expands when heated. So both play a factor in increasing mean effective pressure, and therefore energy output per cycle (power).
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?
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.
Your explanation about where the energy comes from with turbochargers sounds wrong to me.
You’re skipping a crucial step here. The exhaust gases get pushed through input of the exhaust gas impeller on the turbocharger by the movement of a piston in the engine during the exhaust cycle. This “work” isn’t free. Its energy that comes from the other pistons on their combustion cycle. If there is more resistance on the exhaust coming out of the engine (which there is to drive the turbocharger impeller), that energy must be added (robbed) by the energy at the crankshaft that ultimately powers the wheels.
The extra boost of power we experience in an engine from using a turbocharger is that the turbocharger allows more oxygen to be put into the combustion chambers (and the engine puts more fuel in at the same time). The extra energy is from burning - - more fuel in the same period of time than without turbocharging. The fuel is the source of the energy, the turbocharger isn’t recovering any energy.
The article is covering technology is actually recovering energy turning heat (thermal energy) back into electricity (electrical energy).
The exhaust gases are at a high pressure after combustion due to combustion heat. 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. It’s not “free” because it’s energy that is usually just wasted in a naturally aspirated engine. There are many examples of engine configurations where a turbo is used to boost efficiency by reducing displacement.
There were systems on old aircraft engines which used exhaust power recovery turbines geared directly to the crank. Those wouldn’t physically function under your concept.
The increase in manifold pressure doesn’t just increase oxygen in the cylinder. It also increases the manifold pressure, or the total mass of gases. The increase of oxygen does allow for more fuel and total energy in the ignition event but the extra inert gas also expands when heated. So both play a factor in increasing mean effective pressure, and therefore energy output per cycle (power).
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?
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.