Turbocharging is about energy recovery... why not recover MORE?

[H@xtGSX]

So, I was sitting here at my desk, thinking about a project I have at home the involved the use of a tesla turbine, and had an idea. Maybe one of you with more physics knowledge can tell me if it's feasible.

A turbo is basically converting what would be wasted heat energy into work by having the turbine in the exhaust stream... but there's a hell of a lot of heat generated that is still wasted. What if there were a way to harness more of that heat in reserve, possibly serving as a low rpm boost almost like nitrous?

Here's what I was thinking. The tempatures on the turbine housing and down the downpipe are still hundreds of degrees, and fully capable flash boiling water. Water expands at roughly a 1:1700 liquid to gas ratio, so as steam, just a little water can generate a whole lot of pressure if confined. If you were to wrap the 02 housing and downpipe with something like 1/2" copper pipe (or whatever would be capable of containing 100-150 psi, i haven't looked into that yet) that was hooked to a high pressure needle valve tapped into either the top of the exhaust header shooting straight down the turbine volute, or into the housing itself at an angle towards the turbine, let some water down into the lower pipe until it started to flash, you could theoretically make a way to open that needle valve on demand and blast high pressure steam down the turbine to spool it from low rpm much quicker than normal. At least in my brain, that makes sense. It'd probably keep the turbine a whole lot cleaner too.

The problems I see are past my level of understanding though, so maybe you can help.

First, if you were to set off something like this pre turbo, would it cause so much back pressure it might choke the motor? Or would it travel downstream without trying to expand back into the exhaust manifold?

Second, the potential pressures of flash steam can be extremely high, and a relief system would be necessary even if only a small amount of water was remaining in the heater pipe or you'll have a steam pipe explosion that'd make blowing up a motor seem calm... plus, driving around with a tank of constant high pressure steam seems like a REALLY bad idea, so it'd have to be a short burst resivoir that would be completely relived of pressure after use. How much force/volume would you need in reserve to make it worth while, and could that be contained under the hood? Possibly over or in the space where the ABS is?

Third, shoving that kind of pressure though the turbine at low speed is going to cause some strain, but how much strain can you put on something like a TD05H turbine before you rip the vanes off and blow them into the cat?

Forth, is this just going to cause a massive tempature shift and crack up the header and turbine housing? I heard of an experiment where someone tried to inject high velocity vaporized water into the header in hopes of creating an instant flash of steam pressure. It not only cracked the header, it blew up the nozzle from it flash boiling before clearing the valve...

I'm thinking this would be another way of utilizing the heat being wasted down the pipe, and it sounds logical to me, but I am not sure how one would figure out much force the exhaust and turbine can take without just running it until it blew up and then backing off from that... and that sounds expensive.

 

[ed1380]

After the first sentence my first though was using a fuel injector to spray water right before the turbine housing. Obviously a direct injection fuel injector, because they can take the heat.
It'll save the work of running copper tube and steam everywhere, although I would worry about the water spray increasing the chance of cracking the mainfold.

 

[bostonhatcher]

Sounds good in theory but developing it into a controlled, consistent system is the challenge.

 

[TunaTalon]

Steam flashed at atmospheric pressure is still at atmospheric pressure and not useful for doing any work. It needs to be superheated and contained under pressure to be useful. After extracting work from steam the water is either wasted (limited range) or recovered by condensers(complicated).

Steam power for cars has been under development for a century or so and is still being improved.

To learn more about the properties of water/steam see the steam tables at Properties of Saturated Steam - Pressure in Bar.

The more conventional, but still complicated way to extract more energy from the exhaust stream is multiple turbos with some kind of valving arrangement to allow more turbines in line under heavy load.

 

[Rockyp]

It's not the heat that the turbo uses to spool, it's the air pressures that are shot out of the exhaust causing it to work. With a steam system, a relief valve would not work on low RPM's because that's when the system is at a lower temp. The relief valve would spray as pressure builds. The higher RPMs would heat the water quicker causing the relief valve to spray when you don't need it. It would also bring more humidity in the exhaust and cause quicker wear on your exhaust system and turbo. Also, water can cause some major goo. Think about water on a table after it dries or when you wash your car in the sun. Those water spots would also build on the inside of the turbo potentially causing some problems. Steam isn't the way to go, but there may be another way to use the heat for something efficiently.

 

[Calan]

...and you thought moisture caused cracking problems with manifolds in stock form...

It's not the heat that the turbo uses to spool, it's the air pressures that are shot out of the exhaust causing it to work..

Actually, it is the heat.

 

[T is for TURBO]

You'd be better off using that steam energy for electricity production to power, say, an electric motor(s)?

But that, sir, would be blasphemy.

 

[Rockyp]

Actually, it is the heat.

Take a turbo and place the exhaust housing in a fire. I promise the compressor wheel will not spin. Blow an air compressor into the exhaust side, and the wheels spin. You just made a turbo work with cold air and not heat. It's exhaust flow that causes the spool.

 

[jtmcinder]

Let's rename one of you Charles and the other one Boyle and then say you're both right.

 

[Bud92gsx]

Wouldn't it be easier to and more cost effictive to use nitrous to spool at low rpms..And then shut off, when the turbo naturally builds boost...

Or even set up a twin charging system, using a supercharger to creat more power down low, then it shuts off when the turbo builds boost..

 

[T is for TURBO]

Take a turbo and place the exhaust housing in a fire. I promise the compressor wheel will not spin. Blow an air compressor into the exhaust side, and the wheels spin. You just made a turbo work with cold air and not heat. It's exhaust flow that causes the spool.

What do you thing creates that pressure? *hint* It's the heat

 

[Bud92gsx]

Combustion creates the pressure, and heat since its gasoline powered..But In theory, you could fab a way to make an air compressor spin the turbine, withought any heat...

That would be more of a fun project, than put to any use tho..

 

[Rockyp]

Combustion creates the pressure, and heat since its gasoline powered..But In theory, you could fab a way to make an air compressor spin the turbine, withought any heat...

That would be more of a fun project, than put to any use tho..

Since the turbo compresses the oxygen molecules to cause a bigger bang, I always thought about putting pure oxygen in a Nitrous bottle and spraying that directly into the TB. If you get away from the turbo operation and deal with what can build a more powerful combustion, an air compressor or nitrous bottle could be a good idea.

 

[Bud92gsx]

The air compressor thing..Was just a shop hobby type project...


The nitrous idea, people actually do..

 

[rlacasse1]

It's not the heat that the turbo uses to spool, it's the air pressures that are shot out of the exhaust causing it to work. With a steam system, a relief valve would not work on low RPM's because that's when the system is at a lower temp. The relief valve would spray as pressure builds. The higher RPMs would heat the water quicker causing the relief valve to spray when you don't need it. It would also bring more humidity in the exhaust and cause quicker wear on your exhaust system and turbo. Also, water can cause some major goo. Think about water on a table after it dries or when you wash your car in the sun. Those water spots would also build on the inside of the turbo potentially causing some problems. Steam isn't the way to go, but there may be another way to use the heat for something efficiently.

The air would be nothing without the heat.

 

[Pwrtrip75]

Cold gasses coming from an engine would run a turbo, its not 100% heat that runs it. Heat expands gasses and creates pressure and increases the gas's volume making it that much easier to spin the turbo. Air/gas you can relate to the steam you were discussing.... the hotter it gets the more pressure it makes. Engine exhaust pressure multiplied by the heat pressure make it work much better and flow faster than if it were cold. Cold air has more density and is heavier and would move slower.

You'd be better off designing a system that takes recovered heat from the engine and uses it to drive the alternator or something.. Freeing that parasitic load up from the engine would help some.

 

[viperlp01]

Using that steam to create high pressure(hot) air and decompress it in one of these(Vortex tube - Wikipedia, the free encyclopedia) to make extremely cold air.

 

[EclipticalGS]

Heat energy is both the EGT and the flow of the EG at any given pressure. They work hand in hand your both right. For every 20* increase in IAT, there has to be an increase of roughly 60* of EGT to create the same compressor outlet flow. At least this what I've seen doing research at work. So if @ 60*F IAT you achieve your power level @ 1050*F EGT, to make the same power with 0* EGT, your IAT would have to be -290* F. Good luck with that


The flash steam would probably not contain enough volume to do anything quickly unless it were maybe contained in a boiler or something to build enough pressure

 

[H@xtGSX]

Good... Lots of thinking.

Water flashed prior to the turbo should increase the pressure purely from it's expansion. It would have to be in a closed system while heating, prior to injection, otherwise the energy gained from it's expansion would be lost. The regulator would still maintain a certain level of compression in the system, which should be higher pressure than anything in the manifold, so by that differential would still create a faster spool time. The reason I didn't propose something with an air compressor is because flashing off a few ounces of water to steam on a hot down pipe is low tech. Less that can mechanically fail, and also cheaper to design. I do agree though that compressed air could essentially do the same thing...

... Or we could be really awesome by tapping a spark plug into the header just above the volute and just run REALLY rich, then set that shizznitz off in the pipe! (joking)

Really, this isn't about developing some new product everyone will want. It's just testing a theory of another possible way to increase efficiency. Not many people I know would be willing to test this.

 

[Rockyp]

Ok. He asked for a physics answer. The question was if he could use the heat to cause the turbo to SPOOL quicker using steam. The heat is created in the engine and the piston forces moving air into the manifold and turbo. If the heat was just there and not moving, the turbine would not spin. Newton's first law (the basic law of physics) is "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it." Heat is an element, not a force. While heat may cause the force to be there in an engine, the forces is what hits the turbine causing the spin. So in short, heat indirectly causes a spool, but flowing air directly causes a spool. So heat could be used in a more efficient manner, but not in the efficient spooling of a turbo. If heat is so great in a turbo's use, why do we spend so much money on ways to cool it down?

 

[EclipticalGS]

The Heat Energy made in a combustion engine is made of both the temperature and the flow of the exhaust gasses based on expansion. Heat Energy is what moves a turbine, and there is no such thing as heat energy without heat. More heat, creates more heat energy. Cooling down your EGTs will not make your turbochargers output greater. It will suffer.

The reason we cool down Intake temps is because high intake temps cause;
Detonation/knock
Higher EGTs that crack manifolds (for every 20* increase of iat, EGT increases 60* roughly to achieve same output)
Excessive Compressor heat from higher turbine heat

 

[Calan]

If heat is so great in a turbo's use, why do we spend so much money on ways to cool it down?

Most people try to keep as much heat in the hot side of the turbo as possible...since heat energy is what ultimately drives the turbine.

*****

I don't have the time (or desire) to run any numbers, but my guess is that any energy gained from using steam in the manner described, wouldn't offset the weight of the components required to generate it.

 

[chasedardis]

Heat from the exhaust should be greater than heat from steam. Think about maybe adding a impeller with a one way clutch on the turbine shaft and have it in the center with its own separate steam housing.

 

[H@xtGSX]

At an atomic level, heat causes more rapid movement of atoms, which as they collide with whatever is containing then , like an exhaust pipe, it creates pressure... And the pressure differential between before the turbine and after is what causes that movement/flow of air as it travels from an area of high pressure to low.

 

[tkelly27]

A lot of people don't understand heat energy.

Heat

I had thought it was only change in pressure that causes a turbine to spin, but there is a pretty significant change in temp too.

http://www.dsmtuners.com/forums/tur...t3-divided-turbine-housing.html#post151352137

That guy knows a hell of a lot more than I do. If you take away anything from that, note that the air had to be heated to 400 degrees to prevent the air coming out of the turbine from freezing.

Why do we try to insulate the hot parts of the exhuast? To keep the heat IN them and keep it from getting out into the engine bay. I swear I've seen ceramic coated turbines and manifolds getting better spool, can't find them now.

I think straight O2 is dangerous. I remember seeing somewhere that NO2 packs down to have more O2 for a given volume than straight O2, but don't quote me on that.

As far as steam spooling. I've heard of people using CO2 or NO2 nozzles onto the turbines to spool the turbine. You could make a simple model using energy/power to see if it is feasable. I'd need to go get a book to give you an example. I'm not going to do that.

There are some modern antilag systems that might be useful on the street. I'm going to play with it and hopefully not destroy my 16g.