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  • To build a better hybrid... Maybe?

    My mind was working overtime the other day and once again it started chewing on what's on allot of peoples minds nowadays - efficiency of vehicles,

    I normally always get fixated on either the exhaust waste heat or the exhaust combustion, (they are not "one and the same")
    the waste heat could be used to run some kind of sterling type apparatus - or maybe some kind of steam powered deal, but either adds a plethora of complexities in then having to either carry water (that will freeze in the winter) and or another type of engine and all it's complexities...

    Just not practical,

    So I end up back at the exhaust combustion --- This is what drives your typical turbo-charger - it's gasses still expanding, it's gasses still being burnt, therefore -
    In order to properly understand the turbo charger one has to look at the exhaust between the cylinder head (backside of the exhaust valve) and the turbine for what it is - a secondary combustion cycle. Turbo's do not operate on heat - they operate on pressure, therefore expansion is needed between this space - therefore fuel needs to be burnt in this area and is, Like iv stated before - it's part of doing business with the IC piston engine and having to crack the exhaust valve open even though the combustion stroke is still going on - keep in mind this stuff is happening real fast and we have to get the chamber cleaned out in order to properly introduce the next charge...

    The reason why im so adamant about getting this point across is to spare myself all the "over unity" BS that most kneejerk hillbillies are going to be salivating to write... so please spare yourself the embarrassment, there is no "over unity" here, there is real work being done with fuel that would otherwise be used to just heat up a cat...

    Typically in a turbo charged engine we use this energy to spin another turbine to compress air and pack in another half a atmosphere into an engine for better performance --- this is no small task, and it's testimony to just how powerful turbo chargers really are,
    in many ways it's a great design --- turbines are actually a very small package - are now very trouble free and can easily outlast the engine itself, and using one turbine to drive another allows for great tractability...

    So what if we were to just use this wasted energy direct and instead of using it to compress the intake charge we used it to put power back into the system in the name of efficiency - we could leave the engine's stock compression ratio alone, and just route the power back to the crankshaft, of course it's not going to be any "huge gain" like what typical turbochargers do by effecting the intake charge - and in fact its going to be just a teeny fraction, but remember - this is not about power - it's about efficiency, and extra work is being done with otherwise wasted fuel.

    Im convinced that the reason we have not seen any attempts at this is due to it being impractical mechanically - there's no real way to harness those kind of RPM's and reduce them and have them be load sensitive and be able to spool up and on and on, It would take a small CVT transmission in itself - crazy,,, this is beyond just waste gate control, this is complicated...

    But it's not complicated if you enter the hybrid, the turbine could be linked to a computer controlled gen/alt --- this in turn (no pun intended) could be utilized to put power back into the system AS the car is being driven in both city and highway conditions...
    A little high rpm generator - a long shaft that keeps it away from the heat - a computer controlling the perfect ratio's of gen/alt drag and waste gate control...

    here's what you most likely end up with, an engine that's just as powerful (a price has to be paid in exhaust restriction) yet it's overall CFM is reduced - this equates directly to increased efficiency...

    So imagine not just synergy drive rewarding you when your stopping for that stop sign, imagine your batteries being charged slightly when your taking off from it too,
    I know - I know, one more piece of crap to go wrong, but it's a hybrid - why stop now...
    Talk amongst yourselves --- I have to work today so spankings will be given out sometime later...

  • #2
    Not over unity and quite well tested and understood, most notable example was the Wright turbo compound aero engines where, if I recall correctly, the power output of the exhaust turbines was coupled to the crankshaft by some hydraulic system.

    For use in a car, and I suggest this might even be practical for a home shop project, the output of a turbo alternator could be used to electrically drive ancilliary loads that would otherwise be driven by the crankshaft, for example air conditioner compressor, coolant pump, oil pump and all vehicle electrical loads leaving crankshaft power available to actually propel the vehicle.

    The challenge is an alternator that could be spun at turbine RPM, maybe some variation of a Faraday Disk?
    Last edited by The Artful Bodger; 05-18-2012, 08:03 AM.

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    • #3
      The Napier Nomad (two stroke diesel) was an extreme example of this type of engine. Running more than 60 years ago and producing in excess of 3000 hp. The engine had great promise, but by that time the turbo prop had developed so rapidly that the complexity of the approach did not make commercial sense.
      Bill

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      • #4
        Any extraction of energy from the exhaust has to be considered carefully.....

        In the first place, exhaust "friction" lessens the amount of air that can be inducted into the cylinder...because the exhaust hasn't exited yet...... that primarily affects ultimate power capability, but since the piston etc friction is reasonably constant, less power per cylinder would mean that much less efficiency.

        if "X" amount of energy is released by fuel, and you remove energy in one place, there is less that can be removed elsewhere, it is a balance. A turbocharger packs more air in, (or fuel mix) and offsets its added exhaust friction by increasing engine power. Power, again, which isn't the main issue, but power per cylinder might be.

        The energy in the exhaust is in several forms.

        First, of course, it is hot. That is hard to extract effectively, but a stirling engine could indeed run a generator, for instance, as you note. With suitable electronics, the generator voltage would be relatively unimportant, the output could be anything.

        Then also it is pressurized, and that can be used in a turbine running a generator, or other utilization equipment.

        Thirdly, it has mass and is flowing, which again can be used in a turbine.

        The CVT approach is probably a complete non-starter due to complexity and friction resulting.

        Electricity is a sort of universal conversion, which can be used as-is to take a load off the alternator, or can run a motor to do anything required, from aiding propulsion to whatever. Efficiency can be quite high, so extra conversions need not be a barrier.

        But, the exhaust energy extraction has to be a net gain...... it is easy to get energy from it, but harder to prevent that from subtracting from the other useful power.

        Thing of it is, the turbine/turbocharger is about the simplest possible way to utilize the energy. And it directly offers a substantial power gain. One way that can be a benefit for efficiency is to allow use of a smaller engine for equal performance.

        Bearing in mind your total and unconditional condemnation of all hybrids, the ability to use a smaller engine with lower losses (because it is utilized at a higher percent loading most of the time) and still get higher demand power due to supercharging should be attractive in comparison to any sort of electric assist hybrid, etc.

        However, one big efficiency gain is to turn off the engine.... when it isn't required. That probably will be far more effective in increasing "global" efficiency for most cars driven in traffic than any amount of pure engine efficiency gains.

        Nobody really CARES about the energy efficiency of the engine directly. What people care about is how much fuel they have to put in to accomplish the task they want to do.

        That task is generally to get from "A" to "B"..... with some side points of doing so "in a stylish car that says I am rich and important" that are an issue for to some of the "self-appointed nobility" who insist on driving "statement cars" such as BMW, Lexus, Daimler, or perhaps Audi.

        So, the important thing is not isolated efficiency, but overall efficiency, usually measured as distance vs fuel (MPG, LPM, etc). That is not 100% an engine efficiency issue, although that is a component of it.
        Last edited by J Tiers; 05-18-2012, 09:33 AM.
        1601

        Keep eye on ball.
        Hashim Khan

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        • #5
          What about using the exhaust to make steam to power a steam engine?
          Andy

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          • #6
            I work in automotive electrical devices, so I get to see some of the attempts and theories that automotive engineers discuss and investigate. JTiers touched upon conversion of exhaust to electrical energy. The simple method is a multitude of thermocouples wired in series exposed to the hot exhaust gases. Each thermocouple contributes its current at millivolt levels to lighten the electrical load on the alternator, or at least power some of the "conveniences" in the vehicle. Efficient? Cost effective?

            I remember the Corvair (bad idea) and VW (not as bad, but...) waste heat cabin heaters...

            A comment about the carping I hear about the low efficiency of the internal combustion engine: What out there is better? What better fits our infastructure? What other technology can perform better in all climates and driving conditions. The IC engine, (and petroleum fuel) for all its shortcomings, has proven to be the most versatile power source we have.

            If we had it to do over, what historically would have been better?
            Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
            ~Practitioner of the Electromechanical Arts~

            Comment


            • #7
              Originally posted by Weston Bye
              A comment about the carping I hear about the low efficiency of the internal combustion engine: What out there is better? What better fits our infastructure? What other technology can perform better in all climates and driving conditions. The IC engine, (and petroleum fuel) for all its shortcomings, has proven to be the most versatile power source we have.

              If we had it to do over, what historically would have been better?
              Nothing,it was all sorted out in the marketplace a hundred years ago.People fail to remember we had attempts at steam and electric autos back then and probably a few others as well,I seem to remember one attempt at a Horse on a treadmill,but gasoline won out simply because it was the best choice.

              Our politicians should remember we can't just legislate new technology,if they did remember that it would save us a lot of money.

              Any new technology intended to replace an existing one has to deliver the same or better performance and at the same or reduced cost for it to be accepted by the marketplace.

              When was the last time any of us purchased by choice a product that delivered less and cost us more?
              I just need one more tool,just one!

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              • #8
                The reason that doing as you describe (mechanically operating other components off a turbo) is done in very RARE cases and not in automotive applications is bc doing so in such an application would lead to an efficiency loss. Basically, you lose more power doing so than if you simply mechanically drive it, unless the engine and turbo are operating in such a narrow operating envelope (think stationary engine) as to make it feasible.
                "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."

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                • #9
                  Just for giggles look here............ 100mpg

                  http://afstrinity.com/

                  Comment


                  • #10
                    Not to hijack the thread but improvements in vehicle efficiency needn't be to the engine. Back in the 1960's I drove a Saab which had free wheeling - when the accelerator was released, sprag clutches on each axle released and the car coasted with the engine idling. It took practice to get used to it, one needed to plan ahead farther for stops (something that still affects my driving). And when picking up RPMs after coasting down a hill one had to do so gently to avoid a thump. One could lock free wheeling out but doing so cut gas mileage by about 20%. Engaging reverse automatically locked it out, else you wouldn't be able to back up

                    It seems like if the computer controls on today's cars could be tweaked to minimize emissions at idle then this would be a simple way to get more efficiency. Of course, cruise control was uncommon in that era so that could be an issue now.

                    John

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                    • #11
                      I know electric cars have been tried in various ways for over 100yrs.
                      Here's a 1909 Baker electric car that still operates:

                      http://www.youtube.com/watch?v=O9vC3S8MJPY

                      Comment


                      • #12
                        I haven't read it all but I didn't think that a turbo uses what would otherwise be wasted energy. I thought the engine/turbo system was designed to ensure some enegy is left over in order to drive the turbo.

                        I think your first thought of finding a way to effectively use the waste heat would be more productive.

                        Just a passing thought
                        Phil

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                        • #13
                          Today's fuel-injected cars cut off the injectors when coasting with no throttle input. The transistion back to fuel input is so smooth the the driver never feels it.

                          Most of the hybrids utilize Atkinson cycle valve timing which makes the engine more efficient as well as reducing the cylinder pressure when the exhaust valve opens to near atmospheric. This doesn't leave any energy to operate a turbo-charger or any other exhaust energy recovery device worth it's cost and weight.

                          RWO

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                          • #14
                            Originally posted by dlsinak
                            Just for giggles look here............ 100mpg

                            http://afstrinity.com/
                            That is some of the most inventive math I've seen in a while.

                            from that web site:
                            "150 Miles Per Gallon. Mileage is based on a typical week of driving: 40 miles, 6 days per week and 100 miles on one day each week. The first 40 of every day are electric and gasoline is used for longer distances."

                            So it actually gets about 44 MPG after the first 40 miles.

                            Personally, that is not a really bad result, but no better than other plug in hybrids. Of course, they make a lot of assumptions, such as $7 a week for electricity at $0.06 per kWh. I pay $.33 for mine. And that 40 miles on battery is at city speeds ( under 25 MPH) , not freeway where it will (according to their charts) be closer to 20 miles.

                            When the batteries are proven to be as good as in my current hybrid ( 10 years of use as of next month) I'll probably switch to a plug in hybrid if my commute remains as wild as it is now.

                            Back on topic:

                            I like the idea of a turbo driven generator. The question in my mind is...

                            It will decrease engine efficiency a little to run a turbine. How much power does it take to spin the turbine unloaded in a conventional engine? I know a supercharger will suck many HP to run the blowers. How many HP does a gas engine lose due to the increased back- pressure of a turbo?

                            Logically, if there is no increased back pressure there is no energy available to do work. My car, at freeway speeds is pumping 30 Cuft per minute at a fairly low pressure. ( 1.7 liter 4 cyl at 2k rpm)

                            I've heard that if you clog up the muffler (remember 'GlasPac' mufflers?) your engine performance went down the drain. Adding enough back pressure to extract 20 HP to turn a generator seems like it would be a similar situation.

                            Dan
                            At the end of the project, there is a profound difference between spare parts and extra parts.

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                            • #15
                              Originally posted by A.K. Boomer

                              So I end up back at the exhaust combustion --- This is what drives your typical turbo-charger - it's gasses still expanding, it's gasses still being burnt, therefore -
                              In order to properly understand the turbo charger one has to look at the exhaust between the cylinder head (backside of the exhaust valve) and the turbine for what it is - a secondary combustion cycle. Turbo's do not operate on heat - they operate on pressure, therefore expansion is needed between this space - therefore fuel needs to be burnt in this area and is, Like iv stated before - it's part of doing business with the IC piston engine and having to crack the exhaust valve open even though the combustion stroke is still going on - keep in mind this stuff is happening real fast and we have to get the chamber cleaned out in order to properly introduce the next charge...
                              Did we all miss this part?

                              Or do we all just disagree with it??

                              Dave

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