Hi all,

This is my first post here. This seems like the most technical car forum I can find so I thought you guys might like this. Its a concept the author calls turbo cooling. The process used is more commonly know as turbo expansion.

http://www.wdlpower.co.uk/downloads/..._TCS_Paper.pdf

 

Interesting.
At first it seems so counterintuitive, but then you realize it'a almost like an air cycle air conditioning system...

 

just a thought on iuntercooling (sorry for taking it off topic) but how about this!

you spin the turbo at higher than wanted levels to get elts say 40psi at the turbo! you run that through an intercooler and get ti down to near abient temp! then you vent the air to the requierd presure! would this work or would you just be spining the ***** out the turbo to get 15psi????

alternativly you could have a closed loop system for the high presure air and then just a take off to feed the engine!! the sudden reduction in presure would reduice temps to below ambient! could this work????

only point out the two above methods coz im trying to figure how rally teams are susposed to be doing it! but the w*nkers wont tell me how! lol

Chris.

 

Interesting read, thanks for the post. I often wondered about something similar to this but it incorporated more items closer to an actual A/C system, but never got off my butt to see if it had ever been done, plus I don't have the engineering background nor do I know anyone that could answer my questions. The closest thing I have seen to it was the intercooling system Ford used on the latest Lightning concept. Thanks again.

Jim C.

 

Thats a great idea... if you just want cold air, but you want power too and youl'l be wasting a lot to get that 40psi.

 

That is kind of the basic principle on how this concept works except this method uses a turbine to recover some of the energy used to boost the pressure over what you need and use that energy to cool the air further. Lotus did build a test engine using this concept with less than encouraging results. I'm not to sure of some of their design choices though. See SAE papers 2003-01-0401 and 2005-01-1853 if you have access to them. A diesel would be a better choice for an initial test engine as they are less sensitive to back pressure.

Lotus is also researching another concept similar to this but using the recovered energy for other things sort of like turbo compunding. http://www.grouplotus.com/eng/track_...&page=25&id=91

You can get 40 psi. You may need multiple compound turbo stages to do so (different than turbo compounding). The question is just a matter of cost vs benefit as far as power is concerned. Running 15 psi is easily achievable. I'm running close to 13 psi of boost now and could get close to 20psi with a single stock turbo but I have a diesel so knock is not an issue(sorry I'm not an LS engine owner, but I like the technical level of this forum).

Conn

 

this is it guys! i want to know how the hell the WRC teams are doing it! lol

if you wanted really cool intakes then you could run this system i have been thinking of!

run a air to air intercooler to get rid of most of the heat! then run it into a water to air cooler fed with iced water like you would in a drag setup! this way you would easly get below ambient temps!

but then you would get heat soak! so you could run the ac system (or a seperate one run of a standalone battery) to cool the water down again! this would work for a few min i would think but then you would have to cool it back down again! but wold give you well below abiemt temps!

Chris.

 

The idea I have been trying to figure out is how to make an absorption cycle refrigeration system that can be pulled around by g-forces and still work. All it would need to run is heat provided from the exhaust system.

http://www.nh3tech.org/absorption.html

 

A small inline two-phase Stirling Cryocooler placed in-line in the coolant system would have the highest efficiency of all the designs presented.

The first stage would utilize thermal energy flow from the engine to the radiator to power a second stage cryocooler, creating a temperature differential. The hot side leading to a conventional radiator, and the cold side directly in the inlet tract.

Done and done.

Overboosting has been used for some time to employ higher-than-normal compression ratios with boost levels for increased power output in classes that place limits on maximum manifold pressure, but don't place limits on fuel capacity. You pay the piper on the PMEP battlefield, though, which is why you need more fuel than one would expect with the added efficiency of compression.

It is employed to raise the static expansion ratio, while keeping the dynamic expansion ratio about the same, which keeps thermal efficiency about the same. The benefit comes from being able to have an earlier EVO event for a given dynamic expansion ratio, which assists both the topside of the PMEP loop, and helps with turbo control, for an ultimate end of increased power output at the expense of more fuel.

 

LS_RX-7 i think i have heard of these Cryocoolers before! do they not requier and elctrical curent across them to work????

could you also give us some links or exsplane how they work???

aslo could you exsplane the overboosting thing??

thanks alot guys thin is really good!

Chris.

 

Stirling engines and associated Stirling cryocoolers do not require any electrical connections to operate. I'm sure advanced designs could be created that utilized electronic controls, but the theory and method of operation do not themselves require electrical current.

I believe you may be thinking of Peltier cooling, which is a solid state device that does require rather copious amounts of electrical current to do anything useful in the automotive world.

Google for Stirling engines, Stirling cryocoolers, and a Ross Yoke, for information on these topics. Information is widely available.

A simple general explanation is that the Stirline Engine is a closed cyle 'air engine'. Air engine referring to the need for a compressible fluid medium to transport the heat. There are multiple mechanical configurations for Stirling engines with varying efficiencies (which range from high to way high), but they all operate on the same principle:

Maintain a difference of temperature, and heat will flow when allowed from the high temperature region to the low temperature region. You can exploit this to make the heat do work on a system. Stirling engines do this very well. Maintain a temperature difference, and a Sitrling engine will maintain a power output.

The really neat thing about Stirling engines is that they operate in reverse. If you forcefully motor the device, it will forcefully pump heat from one side to the other, *creating* and maintaining a temperature differential. One side will get hot, while the other cold.

This is exploited in the medical industry and the science industry for cryogenics.

By putting a small stirling engine in-line in the coolant system, between the coolant outlet of the engine (where its hot) and the radiator (where its cool), you force the heat to do work on its journey through the stirling engine on its way to the radiator. You use this power output of the stirling engine to directly power another phase, used as a cryocooler. The hot side once again goes to the radiator (a special radiator would be needed to keep the flows separated yet compactly spaced) for cooling, and the cold side goes into the inlet tract to absorb heat from the air charge.

You are using waste heat to do your dirty work.

Overboosting is is similar to having shitty heads and low valve lift on a high boost engine, hah. The principle is that if you are limited to say 1Bar of boost by either rules or the temperatures and octane compatibility, you can bend the rules to the max by overboosting: that is, producing say 2Bar of boost at 250degF, and using an intercooler to remove 100degF or more, and then restricting the inlet airflow into the manifold to register as 1Bar, at an even lower temperature.

This works exceedingly well in certain scenarios, though it sounds counterproductive to use a restrictive inlet system. It does have serious issues with the induction half of PMEP, but depending on camshaft profiling and rules limitations, it can mean being able to run an entire point of static compression more than you would be able to otherwise, as well as an entire new method of boost control: make your restrictor a movable throttle blade, so that at 'lower' rpm/boost levels, your throttle restrictor opens to help maintain 'full boost', and as the turbine comes into its efficiency range, the throttle is closed gradually by a progressive controller to stay under the manifold pressure limit, all the while the inlet charge is getting cooler and cooler.

 

so how much energy can these cryocooolrs "move"?????

also is it depended on the temp differance on the working side and cooling side???

also how much does one of thee cost??? lol

Chris.

 

They move an amount of heat energy equal to the total energy put into their operation times their mechanical efficiency times their thermal efficiency, just like any engine. In real world terms, a cryocooler about the size of your A/C system could remove about 70degC or so out of 1600cfm reliably, as long as the major operating conditions were maintained, the most important being maintenence of the 'warm' side at the radiator.

Remember, the cooler creates a temperature differential based on the energy put into it. So if you put x horsepower into it at a certain speed for your engine, it will create say a 100degC temperature differential. What this equates to is an 'equal' deviation (50degC each) on the cold side and hot side from the working fluid.

So what happens if you can't cool the hot side fast enough? It's temperature rises, and for the same hp input you get a higher cold side temperature. To maintain a specific cold side temperature, you would either have to nput more hp into the cooler to create a larger temp differential, or cool the hot side back down to a lower temperature.

 

so if this was used in conjunction with a conventional intercooler that could gettemps to within say 10K of ambient then how much would the cryocooler reduce the inlet temps by???

would this be practial for use in a FI car? or is it all a bit too far out (not saying its not an amazing idea!!!)???

thanks Chris.

 

I still think using the a/c idea is the easiest way to cool intake temps.

A car a/c generally can extract about 40k-50k Btu worth of energy out of the air, which is equivilent to reducing an intake temp from 125°F to around 75°F at 1500cfm, depending on humidity and efficiency of course.

This drop in temp would cost you about 10-15hp (from a/c load), but just increasing air density alone would get you back 5-10hp, you would just be losing energy due to inefficiency of the compressor and condenser coil here. however, this cooler temp would allow for more aggressive timing, AND allow you to run more boost, negating the fact that you have your a/c on by a LOT.

Not to mention, since all of the moisture in the coiling coil is being kept IN the air stream, and not being drained off like in a normal a/c system, you would increase relative humidity a good amount, reducing the likelyhood of detonation.

Plus utilizing an a/c system that is already on your car would make it an easy conversion. Just build an intercooler with tubing routed specially designed for freon flow in/out from your compressor, and youre good to go.

 

How heavy are fuel cells? If they are light enough, perhaps they could be used to power all the electric accessories, like fans, water pumps, radio, etc, and leave the alternator and battery for the more basic functions.

But - you could power a compressor for the AC electrically as well. That way you get the benefit of the powered, never empty intercooler, without the engine drag of a crank driven compressor.

 

using the AC to ool intakes has been tried an tested before! its just isant efficent enough! also you dont get anything for nothing! so the engine you put in to heating the gas isan't going to reduce you inlet temps enough to make up the power!

now if you where to use it while crusing to cool a chargecooler (running along side a intercooler) then you should beable to us the really cold water to get a good benifit for a few min befroe it heats up!

you could run the AC off a second battery that you charge while cruising and then use under WOT! that might work!

the problem is is you have to use a mechanical messure to get the temps below ambient! and thats where you come into problems! eather because the stuff you are using will run out (n2o, meth etc) ro coz it will heat up (ice water and a charge cooler)!

how long would it take a "normal" AC system to get say 20ltr of water down from 293K down to say 278k???????

thanks Chris.

 

Your a/c extracts 800btu/min bud. If you design an insulated intercooler, you WILL lower your iat's by a lot. The cool air wont make the extra hp, it's the fact that you can running better timing, reduce denation, and add extra boost because you have lower iats.

 

The AC intercoolers I have seen (e.g. Ford's prototype) use it to chill a mass of water, then use the water in the cooling core. This way, the system can be charged with surplus coolth (an HVAC Engineer's technical term for the opposite of warmth ) during normal operation, then used to extract far more heat (although only for a short time) than if using only the available AC output.

 

The cooler air likely would make more power by itself as well, both by reducing effective PMEP, and because of the increased density and thus VE, you are able to *burn more fuel* which is where your additional power comes from.

You can't get something from nothing, this is true. But that is not a true description of what's happening here. You are getting something from the additional fuel you are allowing yourself to burn. Whether the engine is artificially boosted, or naturally aspirated, this principle is identical. It's the same reason it gives more power under boost. It's just more noticeable with boost because you get to burn *even more* fuel, making even more power.