This idea is to use the heat of the radiator to help spin the turbobooster, and use the air moved by the turbo to cool off the radiator.

First, change the radiator to a air-tight, pressure-tight heat exchanger.

Second, make sure that the dispacement of the turboexpander is large enough that the air pressure between the engine exhaust manifold and turboexpander is always slightly lower than the pressure between the turbocompressor and throttle.

Third, divert some some of the compressed air from between the turbocompressor and throttle, sending it through the engine coolant heat exchanger, into the turboexpander.
-- goldbb, Dec 29 2008

I understand what you're saying.

The air exiting the turbocompressor is pretty hot anyway, so one wonders how much extra heat (if any) would be picked up by it during its trip through the radiator. (I used to measure about 60°C _downstream_ of the intercooler under hard boost).

Also bear in mind that the air can't leave the radiator any hotter than the coolant within it, which will only be about 100°C. Even if the air entered at half that temperature, you won't get a particularly worthwhile thermal expansion.

Pressure between the exhaust manifold and the turboexpander is probably higher (by necessity) than the pressure at the outlet of the turbocompressor. I make this assumption through observance that both sides of the turbo are roughly the same size, and of course rotate at the same rate.

Finally, why do you want to bleed off boost, only to (through a thermodynamically dubious route) generate a little more boost by way of increased airflow to the turboexpander?

(That's not my bone, by the way).
-- Texticle, Dec 29 2008


Hate to poo on the idea, but generally speaking boost levels are controled by dumping excess exhaust rather than excess pressuized air for reasons regarding flow maps etc. Flaw in your reasoning? The mass of the bypassable air is so small and hot that it would do near nill for your radiator fluid while retaining the high exhaust backpressure (by not wastegating) would easily exceed the tiny drop in coolant temperature. In reality you would cool the combustion chambers better by venting the exhuast (reducing the EGT) against the radiator (heating) then you would by venting the boost (no change in EGT) against the radiator (null)
-- WcW, Dec 29 2008


Would the idea work better if the turbobooster air flow and radiator air flow were isolated from each other?

Use a compression turbine to send air into the heat exchanger / radiator, and an expansion turbine to let this air back into the atmosphere; not linked at all to the turbobooster. Naturally, one would select a compression ratio that optimally cools the radiator. Higher pressure of course leads to both higher temperature (less cooling) and higher air flow (more cooling) so more math is needed than I know, to pick the right pressure.

If we don't make use of the mechanical power produced *at all*, it only serves to remove heat from the engine coolant -- this conserves *some* energy, since we would no longer need to run a radiator fan off of the engine belt. Oh, and it's possible that the heat exchanger could be made smaller and lighter than a regular radiator, saving weight, which is also good.

But it would be nice if the power generated could be put to use somehow ...

The only reason I thought of linking with the turboboost system is that it would save the need for an extra compressor an expander; any better ideas would be appreciated.
-- goldbb, Dec 31 2008


So it's about "improved" cooling, not boost.

The onset air flow to a standard radiator is usually more than adequate for cooling. The fan only comes on when the car has undergone a prolonged period of little or no movement. The fan is driven by an electric motor (rather than a belt) on all modern cars. Your system requires engine load for radiator cooling, which means that in stationary traffic, coolant temperature will get out of control.

Your proposed system is untenable.
-- Texticle, Dec 31 2008


a larger radiator or an electric fan suplimenting the conventional system would be more effective, cheaper, lighter, less likely to fail, more easily maintained. nothing to see here, poeple, no idea here, move along, move along.
-- WcW, Dec 31 2008



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