Quote:
Originally Posted by payne171
At some point, common sense has to play a role in your thought process serial. You dismissed a technology based on a few calculations made after reading the article. At least one of the engineers on the project was listed as a doctor; don't you think he is capable of those same calculations? You are talking about maybe gaining one horsepower as being feasible, but a device that can put out 6kw isn't? I am sure it won't put out as much power at light load, but that is fixed with more battery.
Come to think of it, look at your own post. A turbocharger is more efficient than a supercharger because it uses exhaust energy instead of crankshaft energy to power the forced induction. Why does that efficiency difference suddenly disappear when one uses exhaust energy to drive a generator instead of the crankshaft?
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I never said it disappears, I just said I highly doubt 6kW is possible under light load. On the highway your car could be producing as little as 10kW of power (small car, 60mph), what makes you think there is 6kW that can be obtained for free from the exhaust? Consider that at full volumetric efficiency, almost 90% of the available energy in the gas is converted into shaft power by the piston. Energy that isn't there ISN'T THERE. Turbines can NOT capture thermal energy. When I give estimates for efficiency, I use upper bounds, so the percentages that I'm calculating are not just numbers pulled out of my ass, they are a reasonable upper bound for the efficiency. Upper bound, meaning the actual efficiency can't be higher.
Might I also mention, turbochargers can be less efficient than an equivalent shaft driven centrifugal supercharger under some operating conditions, when the turbine is causing excess restriction. Turbochargers were never an efficiency thing, they are an easy way to get more specific power. The reason it's getting popular is downsizing an engine is the easiest way to get part load efficiency improvements, and these typically outweigh the overall efficiency loss of a turbocharger.
It is a fact that the theoretical efficiency of a single stage turbine cannot exceed a certain percentage of the ideal efficiency. When you stick a turbine in the exhaust, the only free energy you can pick up is energy that comes from momentum transfer of the exhaust gas. If you actually go analyze the physics instead of tell me that some engineer or Ph.D. said something, you might get something out of this. You don't need to be an engineer to understand the physics behind an engine. Stop using my supposed lack of credentials to attack my point, it's not doing anyone any good.
I already gave one figure, in F1 they were able to recover 7% more energy at full load. At part load this number invariably goes down.
The technology has a place, it can reduce noise emissions of vehicles, and it can improve efficiency by a small amount under high load circumstances. This is a great thing, but we need something else for part load efficiency improvement.