2014 intercooling

[wuzak]

The intercooler reduces the temperature of the air exiting the compressor and entering the combustion chambers. That means lower temperature on the entry to the turbine, which means lower thermal efficiency.

This is so wrong. Compressing cooler air requires less work, just get back to your TD text books, you've got your channels crossed - time for a concept review.

Where did I say different?

[wuzak]

The intercooler reduces the temperature of the air exiting the compressor and entering the combustion chambers. That means lower temperature on the entry to the turbine, which means lower thermal efficiency.

No an intercooler is not before a turbine. It is always between compression stages.

I never said the intercooling was before the turbine. The fact remains that if you have intercooling in multi-stage compressor the output air will be cooler.

This can be recovered by using reheat - burning a little more fuel in the exhaust and running it through a second turbine.

Nope. I've done some turbo machinery theory many years ago, reheat is not for recovery. It's simply to raise the pre combustion temperatures. You can still use reheat on a system with no intercooler.

Ok, so recovery was the wrong word to use there.

And/Or regeneration. Regeneration is taking the waste heat from the exhaust and using it to increase the air temperature after the compressor. This results in higher temperatures at the turbine or less fuel required to reach the same temperature.

What higher temperature does is reduce the amount of heat needed to be added by the fuel.

Which is part of what I said. I also said that with the same amount of fuel the temperature can be raised higher, which is OK so long as your turbine section can handle the extra temperature.

Intercooling between compressor sets (high and low pressure, rather than every individual stage) does lower the compressor work required, but does not increase the overall efficiency of the turbine.

You are trying to back out of the discussion now by muddling the discussion. Why are talking about efficiency of the turbine, when you were orginally talking about thermal efficiency?
The turbine efficency is fixed.

Is it really? By what? Its geometry?

In any case I was talking of the gas turbine, which is the entire engine.

It is also irrelevent for most reciprocating turbo engines. Intercooling in turbo engines really is aftercoling, since in most cases there is only one stage of compression. It is added to keep the intake air at a temperature that won't induce detonation in the engine.

Let me reveal a secret to you.

first stage of compression: compressor (compressing air right?)

second stage of compression: piston (still compressing air correct?)

You know what i'm going to do to increase the efficiency? I'm going to put an intercooler between those 2 stages of compression on that piston engine, so that the pistons have more mass of air to compress.


There are 2 stages of compression in all turbo charged piston engines. I hope this clears things up for you.

Whetever Ringo. Intercooling is not used to reduce compression forces in a trubocharged reciprocating piston engine. It may have some small effect in that, but it is primarily for preventing detonation.

[timbo]

It's not black and white. The compression work is reduced, not the thermal efficiency.

It shows in black in white that thermal efficiency is reduced. There is even an example in calculations. Basically it reduces area in an area in S-T diagram which is thermal efficiency.

It can be shown thermodynamically why intercooling between compression stages increase efficiency.

So please do.

There are implications of Brayton vs Otto cycle, but overall the thermal efficiency is proportional between combustion (heater) and exhaust (refrigirator) temperatures, so I don't see how intercooling may improve that.

[xpensive]

Let's see now, what does an intercooler do...yes here it is, removes energy and increases drag internally and xternally!

This Drake-Offenhauser 2.65 turbo yielded 1100 hp at 120 inches of Mercury, 3.0 Bar boost, and no intercooler back in 1972;

[wuzak]

Let's see now, what does an intercooler do...yes here it is, removes energy and increases drag internally and xternally!

This Drake-Offenhauser 2.65 turbo yielded 1100 hp at 120 inches of Mercury, 3.0 Bar boost, and no intercooler back in 1972;

http://www.tsrfcars.com/images/1972_eag ... %20029.JPG

Was the fuel Methanol back then? Does methanol have a higher octane rating than petrol?

Was ADI (water injection used)?

Where was the fuel injected? Looks to be after the turbo, which would provide some charge cooling.

[FW17]

Let's see now, what does an intercooler do...yes here it is, removes energy and increases drag internally and xternally!

This Drake-Offenhauser 2.65 turbo yielded 1100 hp at 120 inches of Mercury, 3.0 Bar boost, and no intercooler back in 1972;

http://www.tsrfcars.com/images/1972_eag ... %20029.JPG

That is good, but what was the fuel consumption?

[thisisatest]

ive always understood that turbocharged cars running on alcohol do not need an intercooler as the alcohol itself cools it a great deal. that Offy is running alcohol, correct? it's an indy racer?

[neilbah]

which in turn is about avoiding knock/pre detonation and improving volumetric efficiency ,hopefully not at the cost of pressure. anyhow shouldnt it be aftercooler?

[xpensive]

Yes they ran on methanol in USAC at the time and injection was obviously at the individual inlets, as can be seen in the image,
but I simply don't think that intercoolers or water-injection was even thought of at the time.

In 1973, the Porsche 917-30 turbo ran qualifying in CanAm with 2.7 Bar boost, 1500 Hp, on gasoline without intercoolers;

[rjsa]

The intercooler reduces the temperature of the air exiting the compressor and entering the combustion chambers. That means lower temperature on the entry to the turbine, which means lower thermal efficiency.

This is so wrong. Compressing cooler air requires less work, just get back to your TD text books, you've got your channels crossed - time for a concept review.

Where did I say different?

You seem to be looking at a turbocharger and applying the brayton cycle to it and it's not right, you need to look at the efficience of the otto cycle, and there cooler intake air is a good thing.

[FW17]

Yes they ran on methanol in USAC at the time and injection was obviously at the individual inlets, as can be seen in the image,
but I simply don't think that intercoolers or water-injection was even thought of at the time.

In 1973, the Porsche 917-30 turbo ran qualifying in CanAm with 2.7 Bar boost, 1500 Hp, on gasoline without intercoolers;

http://www.sportscardigest.com/wp-conte ... Engine.jpg

http://www.autowp.ru/pictures/porsche/9 ... yder_8.jpg

CanAm was not a series in terms of development race and importance to efficiency in every aspect. At CanAm Porsche had no competition and could what they wanted.

A couple of years down the line Porsche entered F1 with with Mclaren their turbo engines were running intercoolers, efficiency was paramount even when fuel was unlimted.

[wuzak]

You seem to be looking at a turbocharger and applying the brayton cycle to it and it's not right, you need to look at the efficience of the otto cycle, and there cooler intake air is a good thing.

I was doing nothing of the sort.

[rjsa]

You seem to be looking at a turbocharger and applying the brayton cycle to it and it's not right, you need to look at the efficience of the otto cycle, and there cooler intake air is a good thing.

I was doing nothing of the sort.

So just tell me how lower exhaust temperature in an otto cycle is direct indication of lower thermal efficiency of said cycle.

[timbo]

So just tell me how lower exhaust temperature in an otto cycle is direct indication of lower thermal efficiency of said cycle.

Intercooling does nothing to exhaust temperature.

[xpensive]

...
CanAm was not a series in terms of development race and importance to efficiency in every aspect. At CanAm Porsche had no competition and could what they wanted.

A couple of years down the line Porsche entered F1 with with Mclaren their turbo engines were running intercoolers, efficiency was paramount even when fuel was unlimted.

Oh I see, had no idea...