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During cruise and under modest load, turbocharged systems are wasting power through exhaust restriction with only nominal gains in overall performance. Likewise with onboard electrical generation systems, the mechanical charging subsystem is wasting power by continuous rotation without any gain after
electrical storage subsystem is fully charged (alternator, belt and pully subsystem).
The cool side output shaft (compressor side) of most modern turbocharged systems has enough surplus rotary power to drive the electrical charging subsystem (alternator). Since modern internal combustion engines use belts and pullies to drive the electrical charging subsystems, overall:
The net power output would be enhanced by driving the alternator (electrical power charging subsystem) from the compressor output shaft of the turbocharger.
This would also apply to the combustion engine systems under maximum load (maximum acceleration in the case of race cars) as it is generally accepted that the belt and pully driven alternators drag as much as 30 horsepower from a combustion engine, even when the batteries are charged. The inefficiencies of the belts and pullies are eliminated. The inefficiencies of the modestly loaded turbocharged system are improved in the overall net power generated.
Additional features / advantages:
Savings in parts count and manufacturing costs (lower bearing count, eliminated belts and pullies, etc.).
Reduction in size and weight of the overall system and
if coupled with "one wire" alternator subsystems, further savings may be realized.
Alternator may be cooled via airflow in the induction system.
Gains in reliability through reduced lateral loading of alternator bearings.
Engineering considerations:
A redesigning of the alternator for much higher RPM of the turbocharger ... possibly using a simple rotating magnet close to the centerline of rotation with fixed pickup coils (ala magneto).
Any modest reduction in performance of the turbocharger through reduced airflow boost during heavy loading (maximum acceleration) might be offset by maintaining RPM for the next demand cycle (flywheel effect of the more massive rotating turbocharger parts with added alternator rotor).
(copyrights retained by the author. patents may be applied for.)
Similar idea
http://www.halfbake...tromagnetic_20turbo
Includes links to similar pre-baked solutions. The Turbodyne Dynacharger sounds almost exactly like this idea, though they don't replace the alternator entirely. [scad mientist, Oct 04 2004, last modified Oct 05 2004]
[link]
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Easier to clutch these things, no? Then they can be disconnected when not in use. |
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/30 horsepower from a combustion engine, even when the batteries are charged/ |
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If that number is correct then it would be worth a great deal of trouble to overcome it. I don’t have the data either but I can’t believe the 30. |
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I love this idea! In fact it's so good that I wonder why
nobody's thought of it before. I hate worrying about
belts. One suggestion: I think you should have a more
descriptive
title. Something like
"Turbocharger-driven Alternator" would be better. |
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This is partially baked with electrically assisted turbochargers for some diesel applications, when not needed, the electric assist motor functions as a low output alternater. Unfortunatly, there are several problems with this, beginning with the hugely increased turbo lag induced by adding more mass to the turbine. This is not offset by mainting RPM for the next load cycle because when the throttle is closed, far less air can be moved through the induction system due to the butterfly closing. This stalls the turbine, and can potentially split hoses and pop intercoolers if the turbine continues to spin. This is why performance cars use a bypass valve. There are solutions, but extra mass attached to the turbine is ALWAYS bad. At startup, the charging loads placed on the alternator, especially in cold weather, are fairly high. This doesn't normally matter, but if the turbo would have to be sized very carefully so that the exhaust produced during startup would be enough to overcome the inertia of the turbine, the alternator, and the provide the extra torque required to drive the alternator fast enough to charge. Solutions are possible, but the extra complexity and extremely reduced life of the alternator due to high temperatures make this somewhat nonfeasable, especially since fairly good results can be had by simply changing the ratios of the crank and alternator pulleys. Sorry for the length. |
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Austere apathy- I'm not a car expert so this might be
naive, but doesn't Exhaust Gas Recirculation already solve
most of the problems you cite? |
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To the best of my knowledge, exhaust gas recirculation, or EGR, exists purely for emissions reasons, and is actually detrimental to performance. If I recall correctly, it allows for both heating of the intake manifold in carbuerated cars, and reburning of a certain percentage of exhaust, and is in no way related to either the turbocharger or the alternator. |
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I think this is a great idea fasteddie!+ Get a patent today, and cut me in for the following improvements ;) |
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The problems austere_apathy mentions could probably be overcome using the following: |
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Buffer the alternator with a small bank of ultracapacitors. This would serve two purposes. |
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(1) When a spike in electrical demand from the car's systems presents itself, the capacitors would briefly supply it while the turbine spooled up to meet the average power level needed. This isn't too important, as a the battery should really serve this need! (unless your system has no battery~~) |
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(2) For turbo-lag under demand for power to the wheels, the ultracapacitors would serve their most important purpose - supplying electrical power to the turbine.
In this case the turbine-alternator would become a very powerful electrical motor for a brief instant. The electric energy stored in the capacitors would allow the turbine to experience virtually no lag, and allow it to spool-up even faster than a conventional turbine. So turbine inertia is no longer an issue.
During this phase, if you really needed as much power as possible, the baked idea of an alternator cut-out (?) would be also used. |
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I'd also like to mention that excessive alternator current draw at start up is hardly a problem worth discussing as it is so easily remedied with a smarter electrical system. By that I literally mean a smarter system - one that is computer managed in much the same way that our modern fuel and emission systems are. The computer could decide how much power to ask the battery for, how much to load the turbine, and what data should be sent to the fuel system computer to strike an overall balance. This suggestion should be used in today's cars anyway IMHO. |
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High temperature, short life alternator - nope. Engineering problem to be easily solved.
This turbine-alternator should last much longer than its mechanically driven brethren, due to the vast simplification. Aircraft use high frequency alternators, so the technology isn't new. |
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I can't see a downside to this idea as it removes complexity and improves efficiency. Using ultracapacitors in combination with an electrically boosted turbine will make it superior to conventional turbines, and that'd be the icing on the cake. |
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Good idea, the inertia in the Car industry however woiuld limit take up, check the number of models that an alternator fits chances are they use the minimum number of sizes they can. |
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now look at the number of models that have turbos. |
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This idea reminds me how much I'd like to have a "dingy" (broadly stated, a component for under the hood that contained a car's electrical generation and management devices and interconnections) that mounts on an engine shaft. It would ideally be simple to install or replace, mounted on a few bolts, and would contain the engine computer, alternator, a/c compressor, and egr/sensor vacuum manifold. I doubt it would be larger than the component parts now layed about the engine and I sure appreciate the shaft/balancer tie-in as opposed to belt drive. + for general agreement. |
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at the detroit autoshow, mazda had a demo turbo-rotary, powered by hydrogen, and the turbo was electric motor supported to elimate lag but also possibly do as you suggest |
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Exhaust Gas Recirculation does help emissions systems, but I read that it also can lessen or eliminate turbo-lag. The idea is that the volume of exhaust stays constant regardless of engine power. Therefore the turbo speed stays constant. |
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Even supposing we get over the turbo lag, and the heat issues, there are two major issues remaining. The first is that there isn't a whole lot of extra energy that can be extracted from the turbocharger. You are already getting all you can with the extra horsepower that the boost allows you to use. If you try to take more energy from the turbo, you will have less energy available to the engine as air pressure. Simple thermodynamics. The second is that a turbocharger is an extremely precise piece of machinery, 18,000 RPM, with clearances much finer than most places in your engine. Alternators are nowhere near that precise. The cost of engineering and building a turbo with two extra oil fed bearings and an alternator that is balanced well enough to spin anywhere close to that RPM would be extremly prohibitive to say the least. |
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How do they do bearings in current turbochargers? (yeah... why don't I just look it up?) But they're pretty small; they could probably be held up with air bearings. |
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I was gonna say how bad this idea is but then it just dawned on me. Don't use the turbo to add boost to the engine, but spin another turbine that is the new alternator. With a waste-gate on the exhaust (as is normal) set to open at low boost - 2-3psi - and a blow off valve between the 2 turbines to stop the alternator turbine slowing when the throttle is lifted. Or you could use the turbo to boost the engine and have a waste-gate set to open almost immediately but only let a small amount of air out (you would still need another waste gate)and the exhaust (from the little waste gate)is then piped to another turbine like above on its way back to the rest of the exhaust flow. But for all the complexity ............... I had to run off at this point before...... the cost of 1 turbo is enough to make it not practical for most people, expecting people to pay the cost of 2, one of which would need to be made from some very special parts is just getting silly. |
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Its more practical to keep the alternator |
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