Manntis

so someone was discussing how the upcoming RX-7 might use a hydraulic turbo (instead of running off exhaust gasses) and that got me to thinking: does that mean yet another separate hydraulic system on the car? Brakes, steering, clutch - these all have reservoirs, etc.

Instead of adding yet another closed-loop system, why not take advantage of something that's already there? An idea I was tinkering with a few years ago was running a turbo off the coolant already circulating in the engine/rad. Have a valve linked to the throttle pedal so when you floor it, coolant is diverted through the turbo to spin it up and compress air. In theory it'd have less lag, since fluid doesn't compress.

The turbo would still take time to spool but a guy could use a 'leaky valve' so even under medium throttle a portion is diverted through the turbo, making it spin and ready should you tromp on it.

I know this has probably been tried (many of my out-there schemes have) and I'd be interested in hearing about problems encountered.

shm21284

I believe the concept was for electronically controlled turbocharger, not hydraulic. I could be wrong.

I would think that the engine coolant wouldnt be enough pressure to spool a turbo. Engine coolant runs at a mere 15 psi. I would think that you would need at least 100 psi if not more to spool the turbo up quickly. The leaky valve is a good idea. In reality, though, I would opt for an electronically assisted turbocharger (electric motor connected to the turbo with a one way bearing) because it simplifies overly complex hydraulic systems, as well as removing a lot of places for error.

Manntis

IMHO it wouldn't be overly complex - the fluid is already being pumped.

Your PSI point might be falid - but what PSI does exhaust gas provide? Fluid tends to move things far more efficiently than gas (case in point: torque converters)

Yark79

Thats very interesting. I've never heard of a hydraulic turbo. Have car makers ever used one before? Like who? I would be interested to see how something like that would work.

steve84GS TII

Engine oil would be a better medium for propelling a hydraulic turbo.Especially on a rotary since we have high volume and high pressure oil systems in comparison with average piston engines.Plus engine oil is an anti corrosive lubricant which would deter deterioration of the drive turbine,unlike water.Weve all seen a corroded water pump impeler right?
The big difference is that the oil pump is positive displacement,it moves oil with positive force and more effectively lower RPMS.The water pump is centrifugal and while it can flow a good deal of volume since its relatively large,there is very little pressure.Decreasing the orifice size can increase pressure a bit,but too much resistance to flow will just cause the pump to stall out.As an example,try putting you hand over a hairdryer.Its a centrifugal pump also and it doesnt take much to block it off.Itll still run fine,but wont move anything.If it were a positive displacement pump,youd get some pressure build up and/or the drive motor would stallout(deadhead)
The downside to running oil pressure to run the turbo is that there will be a direct parasitic draw on the engine from mechanically pumping up the oil,then using that energy to drive the turbo.Using exhaust gas is nearly parasite free since the gasses are just funneling out the engine anyways.There is a small amount of pumping energy required to push the gasses through the restrictive turbine,but the gains outweigh the losses.And again,the internal combustion engine is a positive displacement pump,so even though gasses are compressible unlike fluids,the gas is being pushed by direct mechanical forces(the rotors),not centrifugally like in say, a jet turbine engine.

Manntis

right - but once the gasses are pushed, they're compressable. Hydraulics are an efficient way of moving force from A to B with little loss of power.

Your point about oil is an excellent one - the side hydraulically powered could be far smaller than an exhaust gas driven turbo.

Your hair dryer analogy is flawed - moving air, which is very compressable, with a weak electric motor isn't the same as a turbine spun by moving fluid. Case in point: hydroelectric dams do a great job of spinning large generators

QuagmireMan

hopefully they will get ride of the oil pan, and they could use a very high pressure oil system to move the turbo.

steve84GS TII

I wasnt using the hairdryer analogy to explain power output,I understand that they arent very strong.My point was that a strictly centrifugal pump(moving gas or fluid) can be deadheaded,stopped from flowing its medium.And while a turbo itself is a centrifugal pump,its driven by a positive displacement pump(the rotors-pistons)
Its far more effecient to drive the turbine off a positive displacement pump,be it the oilpump or engine pistons,than off an easily deadheaded centrifugal pump like the waterpump.I work on hydraulic pumps and motors all day long(tractor mechanic) and Ive yet to ever see a centrifugal hydraulic pump.A gear or piston hydro pump can generate thousands of psi and are used to power some of the largest and heaviest man made things in the world.I also work on various clearwater and trash-sumpwater pumps,some piston and some centrifugal.The piston pumps are near impossible to stop and can move water under extremely large headloads.The cent. pump,even large ones can be blocked off and deadheaded quite easily despite their high volume output,simply because they dont use positive force to move their medium along.

thekyl

A better idea would be to take a small storage tank about 1.5gal and fill it with Oil or some high grade fluid that dosent break donw very fast and hook it to a super modified turbo kinda like a genorator with one of these http://www.jegs.com/cgi-bin/ncommerc...80&prmenbr=361 and then you would be providing lots of PSI that dosent have another link from the stock Oil sump so you dont risk the modified turbo making an oil leak and blowing your engine. This would make the wanted forced power for the compresed air and use the hydrolic oil to force the turbin.

thekyl

yea I like Steve's Analogy

Manntis

Visteon is doing some neat work on electrically driven turbines, but specialising in mass-production European applications featuring small displacement boingers.

There are a few other schemes out there - one features a circular induction motor sandwiched between the two sides of the turbine. The idea is the electric motor spins it up (335 miliseconds to full spool) then the exhaust gasses take over to maintain it - and when not in 'turbo' mode the exhaust gasses spin the CIM to use it as an alternator.

Neat concept, but he ran into problems when trying it in the real world. Apparently no one told him how hot turbos get, and CIM wiring doesn't like that much heat

Steve, there are tons of centrifugal pumps out there moving large volumes of fluid, but your point about deadheading is valid. In this application, however, that could act as a safety feature. After all, why does a centrifugal pump deadhead? If something jams the turbine. Having a turbine that stops when something solid is stuck in it is not neccessarily a bad thing...

The problem I see with the oil method is a possible drop in oil pressure on engagement, depending how the valves are configured and if the closed-off loop is kept full between uses. One wouldn't want a drastic drop in oil pressure just as one is flooring the throttle. It does however solve the nasty corrosion problem nicely.

Ideally I'd love to build a simple little rotary like the 13B in the GSL-SE with a CIM acting as starter motor, alternator, and flywheel all in one. driving all other accessories electrically would free up the engine to power the wheels, and nothing but the wheels - and the CIM can provide takeoff torque, overcoming one of the rotary's achilles heels (low torque) nicely.

steve84GS TII

If you read the "technobabble" section of Sport Compact,there was an article about this very subject a while back.The hydraulic turbo does work and does exist,however the majority of the article was devoted to an even more interesting turbo that has existed in the long-haul trucking industry.
Its the double pass turbo.Basically a twinsnail compressor,it pumps and re-compesses the intake air twice inside a common housing,before delivery it to the engine.More pressure and output from a physically smaller,easier to spin turbo.Really interesting stuff,just a matter of waiting for the "trickle down to the public" effect to occur......

thekyl

Yea you know I asked about a year ago asking if anyone thought that a trucker tubo would be a good idea and lots said no that the 12a or 13b could not genurate enough out gas to effectivly spool up the turbo. well said to say I ditched that project a while ago humm maybe I will look into it now that I kinda have a better understanding of how the Rotories work.

Kentetsu

I always wondered why nobody has tried to reclaim wasted energy for use in a turbo-like device. Take braking for instance; braking = negative acceleration. You are giving away the speed that you've built up, and getting nothing in return other than safety.

For a rough analogy, imagine that your brake pad is replaced with a small wheel to drive a compressor or generator (engaged only for light braking, then pads take over for the serious stuff I guess). Use the drag caused by the gen or compressor to slow you down and you receive energy in return, whether it is compressed air or electricity or whatever. They may be doing something similar to this with electric cars, but I'm not sure.

Anyway, if the biggest killer of turbos is heat, then why must you use a hot source for the power? There must be enough wasted energy that you could pick up a source to run the turbo and reclaim some of it.

Anyway, I'm tired and rambling. Manntis, I'd love to have a few beers with you sometime. I like people who aren't afraid to think along new lines...

steve84GS TII

Actually that process is used in the hybrid gas/electric cars,its called regenerative braking.Basically,when you want to decelerate,some of the potential energy in the moving car spins generators and helps to charge the batteries and slow the vehicle,alongside the regular service brakes.This is oppossed to just having the brakes convert 100% it into heat energy,which is wasted into the atmosphere.

In regard to truck turbos,yes they would be far too big for a rotary and diesel turbos are setup different than gas engines because of their lower RPMS and running characteristics.But the actual function of the twin pass compressor can be utilized by any turbo.Currently its only used on rigs because the trucking industry is the top of the heap when it comes to diesel/turbo tech.Itll just take some time to become availible to the public.

Manntis

*waits for someone to try to create a 'jake brake' for rotaries*

and yes, I'm kidding

steve84GS TII

Heh,heh............
Open ended wastegates are annoying enough, thank you!