Intake temperature turbocharged engine

[HAD]

Hi all,

I am involved in developing a engine that is for drag racing use this will be turbo charged. What I would like to know is, is there a limit in regards to how low a air intake temperature that can be safely used. I ask this as we are looking at using a intercooler setup with a outer skin so the heat transfer area would be in a liquid nitrogen bath. I have seen similar system where they use CO2 as the coolant, but this requires a outlet for the gas to exit after the transition from liquid to gas.

Any help would be greatly appreciated.

John

 

[Warpspeed]

I have never seen it done, but my guess is that the inside of the intercooler might quickly ice up and restrict flow once the temperature drops below freezing point.

 

[sreid]

There is probably some lower limit to the air charge inlet temperature but you are not likely to reach it. Turbo charged aircraft engines can suck in some pretty cold air at altitude. Water vapour can be precipitated out of the air with a pre-cooler before the turbocharger.

Nitrogen gas will still need to be vented.

 

[Lou Scannon]

My guess is that optimum performance will occur, due to increasing size and mass of the liquid nitrogen intercooling system, at a point that is before problems are encountered from the air becoming too cold.

 

[patprimmer]

Once you get below freezing, icing can be a problem.

Air at altitude is already cold is dry.

Air at ground level that is cooled suddenly is still wet and forms ice.

Also, although you increase the mass of oxygen in the charge by cooling, there comes a point where it becomes difficult to get good vaporisation of the fuel. That is why they typically use petrol as the supplementary fuel in NOS injected methanol fuelled motors rather than just adding extra methanol as the supplementary fuel.

I can't put an actual figure on it, but I would think that about 3 to 5 deg C might work well, or say 35 F

Regards
pat pprimmer@acay.com.au
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[HAD]

Thanks for the feedback guys.

This will be used at sea level as it is in Perth, West Australia, also the humidity is usually faily low.

From what I can gather then something like the cryo-cooler (CO2) would be the way to go as yes this will not subject the air to essentially super cooling and minimise icing of the internal baffles of the core. The other option would be water/methanol injection to stop icing.

Any further comments on this ?

John

 

[turbomotor]

I did some work with LN2 precooled air and a centrifugal compressor. The pressure ratio follows delta T / T1, so you may be pleasantly surprised at the increase in pressure ratio you get with precooled air. (Required work follows Cp-delta T, so you can get a lot more pressure ratio (boost) for a given amount of shaft work supplied to the compressor.)

The work I did was in a lab (dry air), but the device flew as part of a larger system (into the stratosphere, again dry air).

Since that time, I have also contemplated precooling as a means to get a high boost level for a motorsports application.

I think that most of the comments are spot-on. Icing of the precooler may be a difficult problem.

Dick