Laxfreak3557

Not sure if anyone has posted this video yet, i thought it to be an interesting concept. What do you guys think? I'd love to see the rotary become the main economical engine in the automotive industry!

http://www.youtube.com/watch?v=iy_Jd5kewbM

RacerXtreme7

iTrader: (2)

Been disscussed, SEARCH. Doesn't seem anyone has tried it on a rotary, its WAY over kill and complex, it's really meant for high boost application (drag/tractor pulling). The Supra guys seem to be raving about it though, but they can't spool up BIG turbo's as fast as a rotary can.

~Mike..........

RX-Heven

iTrader: (1)

Turbo compounding and compound turbo engines are different.

A compound turbo engine is one whose turbo feeds compressed air into another turbo to feed the engine. A "chain" of turbos feeding one another and then the engine essentially. This is what the Supra guys have accomplished recently.

Turbo compounding is a method of using the wasted exhaust from the engine (with or without an existing conventional turbo) to feed a turbine that provides additional mechanical force directly to the e-shaft/crankshaft.

Laxfreak3557

From the information given in the video it seemed to me that the turbo compounding system works much like the kers system seen on formula one cars, except it uses a turbine to put power directly back into the crank shaft instead of an electrical motor and battery. Turbo compounding has nothing to do with intake boost pressure. The turbine isn't driving a compressor wheel, it's connected directly to the crank via a geared reduction so how does high boost pressure have anything to do with this topic? The whole point of using the rotary for this idea is because of it's strong exhaust pulses and lack of exhaust valves as described in the video.

The complexity of the system would be well worth it (in my opinion) if it helped to place the rotary engine in front of the economy piston engine designs. Plus how hard would it be to simply take the compressor housing off a turbocharger, connect the turbine to a gearing mechanism (maybe like one on a supercharger) and then back into the pulley sytem on the front of the engine? I see it sort of like a backwards centrifugal supercharger connected to the exhaust. does that make sense?

I could be completely wrong though.

the video talks directly about the rotary at aroun 5:30

P.S. i did search and the only thread i found was back in 2002, but i'll take a look at it again and see what's in it.

Starfox07

Wow, this seems like it would be reasonably simple to do and be safer than turbocharging too. Oh the ideas that have yet to be fully realized (the rotary itself?? )

Laxfreak3557

exactly my point. considerably more horsepower without an increase in combustion chamber pressure. I'm glad i'm not the only one that thinks it could be fairly simple. And about the rotary not being realized, i think this has the potential to open alot of people's eyes to the rotary engine.

Chaotic_FC

i think it needs to be done. all somebody has to do is bolt their turbo to a shaft that is geared onto the flywheel. If nobody does it soon, i may have to.

Starfox07

My brother is starting graduate school in mechanical engineering...I told him to write his thesis over it.

Starfox07

It would have to be geared just right, otherwise I imagine you would create enormous back pressure and LOSE power and efficiency.

Chaotic_FC

well, that would be part of the experimentation.

patman

iTrader: (3)

it would be almost impossible to make this work... the problem is that the power curve of a turbine does not match the power curve of an IC engine very well...so you would have to design the turbine and gearing such that it adds power at a certain narrow range of load/rpm. In that range it would work great, but everywhere else it would either not do much or it would actually cost you power and efficiency.

It makes a lot more sense just to use the turbo in a conventional manner, which increases the efficiency of the engine at throughout its operating envelope. If you are trying to capture exhaust energy left over after the conventional turbo, it would be more advantageous to either use a second turbine to drive an alternator so that it isnt constrained to a specific speed, or capture the waste heat in a different way.

Starfox07

I was thinking the same thing. But you could also use a CVT transmission to keep it at optimum speed.

Laxfreak3557

yea, it definitely makes more sense in say an airplane application where you set your motor at 75% power at cruise and keep it there almost the whole flight.

but hey who knows maybe with some r&d it could be made to work well on an automotive engine.

rotarygod

iTrader: (1)

No one would be willing to do it properly as everyone considers a turbo or a supercharger as a power boosting device not an efficiency increasing device. That may sound contradictory but understand the context that I am referring to them in. The use of a turbo/supercharger system in this case is not being used for an ultimate power gain. It is being used primarily to recover wasted energy so less fuel is used. If someone were to build one, people would complain that it didn't get more than 200 hp and would completely ignore the mileage benefits citing highly scientific reasons like "I don't think it was worth the effort" or "what a waste of a good turbo/supercharger". The short answer is that no one has done it because most people don't understand that a turbo doesn't have to be a power adder.

The very first turbocharger was basically a turbo compound setup. There was a compressor wheel that was crank driven which makes you think supercharger (turbos were once called turbo superchargers) but there was also an exhaust wheel that was also crank driven as an energy recovery device. Later on it was realized that you could put these 2 wheels on the same shaft and have them spin solely from the exhaust gasses which was developed into the modern turbocharger. The modern jet engine was also born from this setup.

patman

iTrader: (3)

Not everyone...look at the VW 1.8T for example. Maybe in aftermarket you are right, but fuel prices are starting to rise again, I think some backyard mechanics are going to start looking for efficiency rather than power.

Wouldnt you agree though that for a given power level it would be much more efficient to run a turbo in the conventional manner (designed properly so it runs in its efficiency range, not all these people who have hugely oversized turbos) than it would to attempt to gear the turbine down and mechanically apply the torque?

Starfox07

It is hard to agree on something that has never really been done before. I think this is something that deserves a bit more attention.

Laxfreak3557

I just remembered another detail that might be able to help with broading the effectiveness of the turbine. In WWII two engines i know of, the rolls-royce merlin (i.e. P-51 and Spitfire) and the damiler benz db600 series (i.e. BF109) used two speed superchargers, basically a gearbox on the supercharger, to widen the powerband on those engines.

Maybe technology such as this could be applied to a turbo compounding system to more closely match the turbines power curve to the i.c. engines power curve. Any suggestions?

Starfox07

Yeah, like I said a few posts ago. A small CVT (continuously variable transmission) would be just about ideal. They are much simpler than you might think and can be packaged into small areas. I'm actually somewhat surprised they haven't taken off in supercharger applications yet.



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Laxfreak3557

I like this idea too! i never really knew how a cvt worked and this does seem like it would be a great idea. It appears that someone could easily machine there own cvt? I don't know much of anything about milling but it looks like some time on a lathe could make the main parts. I do have one question though is a cvt self controlling, meaning that the rollers adjust automatically or do you have to have a seperate sytem that would control them. It seems that to always be at optimum effeciency you would need some sort of control device? If that makes sense

Starfox07

I think you could have it on a centrifugal system where as the RPM's increase, centrifugal force forces the pulleys apart/together. It would be much easier and probably more beneficial, however, to write a simple control program with an actuator and run it electrically/hydraulically.

patman

iTrader: (3)

they are usually centrifugal, the problem is that they are not very efficient, so you lose a good deal of power

Starfox07

Only one way to find out. Somebody with fab skills needs to do this.

BLUE TII

iTrader: (9)

Instead of complex turbine to engine mechanical drive train, it would be much better to just make the car a parallel gas/electric hybrid and use a high rpm generator/alternator on the turbine.

We have room to replace the starter with a much larger constantly engaged motor and no need to take the compressor off the turbo, just run a shaft off the front nut to the high speed generator/alternator through a curved turbo inlet duct with support bearings in the tube wall.

I looked into this a many years ago and the turbine driven high speed generator/alternator is patented already


You could even use the turbine's generator/alternator as a motor to spool the turbo up.

nillahcaz

iTrader: (2)

they slapped a unit for a 54.86L twin speed supercharged engine on a 2L.


ok..... wow thats good stuff.

So on when properly fit to an engine it gave 5% boost in economy, I get 21mpg mixed driving. I'm up to 22.05 mpg and added a lot of new parts that all have hot exhaust gas in them. So there will be loss due to the cast turbine hosing and all the internal parts and heat management to keep the intake temps down.
As far as making something like this out of a off the shelf turbo..... you will need to remove the compressor as it takes power to compress air and asking any hot side to push 5-12 PSI boost and still expect any thing to be left is more than hopes and dreams. It is not odd to have a turbo spin 200k rpm. not 11k like he says in the vid, but a full TWO HUNDRED THOUSAND rpm. making any transmission that can have a input that fast will not be cheap, and all transmissions will eat some power. Now the good news is as you gear stuff to spin slower you gain torque so by the time you get it down to be optimal output at about 2000-2500 rpm crank speed for highway cruising it may make some power.

there are lots of neat ideas out there but all engines are not the same. you cant say it works on a LS1 so it will work on a rotary same for aircraft engines and auto engines.

Starfox07

I did not think of the high rpm problem. That would wreck a CVT in seconds.

How about going with a turbine such as the one proposed in the video, but having a wastegate as well, so it doesn't build up excess pressure. It would reach an equilibrium backpressure, open the wastegate, and maintain the equilibrium all the way to redline. It would be sort of a self-regulating thing. It would also make alllll kinds of cool noises.

Orrr having a regular turbocharger feed pressurized air into another turbine attached to the engine. That way there would be no mechanical linkage and it would reduce back-pressure/drag incurred by the other methods.

So many ways to solve problems.