Earth sleeve

[JohnW2]

I never realised earth sleeving was so complex...

Indeed. I think this has to be one of the most extreme examples I've seen of 'tangential discussions', even in this forum!

Kind Regards, John

 

[EFLImpudence]

Thanks for confirming - that is, of course, what I've been suggesting all along.

So - not so much confirmation as agreement with your view.



The fact is that:
Cool air contains more oxygen than the same volume of hot air.
This is true whether the air is compressed or not.

Can you please find an authoritative article which states that the main or primary purpose of an intercooler is to prevent detonation rather than increase the density?

 

[Nozzle]

There's a whole lot of words in there, so I'll try to respond intuitively as I can answering what I think you're getting at (though I'm not super expert in fluid dynamics....). Take a pair of turbos or superchargers, rated exactly the same, running on two identical engines. The only difference being one has an intercooler and the other does not.

The one with the intercooler is cooling AND collapsing the air, and in doing so, if it were a fixed volume, would be creating a lower pressure. But it's not a fixed volume, though the air pressure is still trying to collapse, but up-stream of said collapsing air pocket is the 'charger. Now though, the charger, in one engine is increasing air pressure from say 1atms to 2 atmos. The other is increasing air pressure from 1atms to 1.9atms, so it can flow more. And that extra flow is the name of the game.

And there's a whole load more words!

Nozzle

 

[EFLImpudence]

That doesn't make sense.

 

[Nozzle]

That doesn't make sense.

Which bit(s)?

Nozzle

 

[JohnW2]

So - not so much confirmation as agreement with your view.

Fair enough.

The fact is that: Cool air contains more oxygen than the same volume of hot air. This is true whether the air is compressed or not.

Indeed, provided that the pressure (whether atmospheric or otherwise) is the same in both cases. The question we are debating is that of the conditions required to cool the air (hence increasing density) without there being a corresponding reduction in pressure.

Can you please find an authoritative article which states that the main or primary purpose of an intercooler is to prevent detonation rather than increase the density?

I thouigh that I more-or-less had, but I'll see if I can do better.

Kind Regards, John

 

[EFLImpudence]

The one with the intercooler is cooling AND collapsing the air, and in doing so, if it were a fixed volume, would be creating a lower pressure. But it's not a fixed volume, though the air pressure is still trying to collapse, but up-stream of said collapsing air pocket is the 'charger.

Yes.

Now though, the charger, in one engine is increasing air pressure from say 1atms to 2 atmos. The other is increasing air pressure from 1atms to 1.9atms,

Surely it will continue charging until 2atmos is reached.

so it can flow more.

Why/how will it flow more at a reduced pressure?

And that extra flow is the name of the game.

If that were the case then logically surely it would flow better at 1.8 or even 1.0atmos.

Obviously the flow will be greater at higher pressure and be even better with increased oxygen because of lower temperature and increased density.

 

[EFLImpudence]

Indeed, provided that the pressure (whether atmospheric or otherwise) is the same in both cases. The question we are debating is that of the conditions required to cool the air (hence increasing density) without there being a corresponding reduction in pressure.

As above, because the turbo is still charging.

I thouigh that I more-or-less had, but I'll see if I can do better.

I'm sorry if I have missed a link.

 

[Nozzle]

Yes.


Surely it will continue charging until 2atmos is reached.

Why/how will it flow more at a reduced pressure?

If that were the case then logically surely it would flow better at 1.8 or even 1.0atmos.

Obviously the flow will be greater at higher pressure and be even better with increased oxygen because of lower temperature and increased density.

It will flow more at reduced pressure (on the discharge side) of the turbo becuase there is less "back pressure" that the turbo is working against. (Different story for a positive displacement super charger though). It's the equivalent of a centrifugal pump running against a close discharge valve (Max manifold pressure but bugger all flow, suction and discharge pressures will be the same). The opposite extreme is with a turbo running with a whacking great hole in the manifold, the pressure on the discharge side is at the minimum, but the flow is the max it can be as it's easy to push air through the breach. (indeed, this is why a dump valve might be fitted to keep the impeller at a high speed).

The engine demands, and is supplied, more air by dropping the pressure in the lnlet manifold by sucking in more charge - the turbo is trying to maintain the pressure high but it will drop and keep doing so as more charge is consumed.

Nozzle

 

[Mikefromlondon]

The fact is that:
Cool air contains more oxygen than the same volume of hot air.
This is true whether the air is compressed or not.

I am not sure if I can bring myself to agree with your facts without mentioning under what conditions, as I explained earlier, if you trap some air in a canister and seal it, then no matter whether the temperature of the whole can is hot or cold, the density of air trapped within that can will be constant, its density won't change when it is any colder, because it will still contain same number of molecules of air, unless you want to tell me that when it gets very very cold then all the atoms and molecules of air condense and fall to the bottom of the can and leaving vacuum on top, then one might see some light in your statement of fact.
To do this we will need a glass jar and trap some air and put it in a deep freezer to see if the air inside condenses to liquid. Pressure regulating valve ensures targeted pressure is available at the inlet manifold, within a given RPM range, the density of air should remain constant as well since to maintain pressure steady more air is pumped in, that means any tendency of density to lower is curtailed by more mass of air arriving thus maintaining steady density.

2nd point I made and you negated it was that in a turbo charged car, turbo compressor is pushing air into the manifold all the time within a given engine speed range, so any loss of pressure due to cooling by an intercooler gets replenished by more air forced in to compensate, loss of pressure, so a steady pressure is mintained, and so like in my example of a closed lid can, if you take two cans and in one you put normal atmospehric pressure (air) and in another you put 2x atm, now you got two jars where one with higher pressure has more density.

As for dynamics of a turbo charging, it is no different to a voltage regulator, a voltage regulator regulates precise voltage irrespective of temperature varaition and load, its job is to supply current within its designed range of operation, same way a turbo charging system will maintain a certain amount of pressure at the inlet manifold irrespective of cooling or not cooling, because pressure is regulated by a pressure regulating valve, known as a dump valve, where a minimum pressure is maintained within a certain RPM range, obviously turbos don't boost pressure when engines are revving below about 2000RPM, and at higher end they may boost too much so excess pressure is discahrged via a dump valve or allowed to recirculate back into the compressor or discharged to atmosphere.

So no matter how much cooling is being done to the incoming compressed air, if it cools down too much, the pressure will drop, if pressure drops then more air will be forced or pumped in to maintain pressure, so when pressure is kept constant, then density should not change, even through cooling by an intercooler, its final pressure at the manifold is maintained to a minimum required amount and topped up as and when necessary or if it gets too much, it gets discharged if throttle valve is closed and the engine does not require much when idling or when decelerating.

It is beginning to do my head in just a little, I think I will soon need a new head gasket soon!

 

[EFLImpudence]

I am not sure if I can bring myself to agree with your facts without mentioning under what conditions, as I explained earlier, if you trap some air in a canister and seal it, then no matter whether the temperature of the whole can is hot or cold, the density of air trapped within that can will be constant, its density won't change when it is any colder, because it will still contain same number of molecules of air, unless you want to tell me that when it gets very very cold then all the atoms and molecules of air condense and fall to the bottom of the can and leaving vacuum on top, then one might see some light in your statement of fact.To do this we will need a glass jar and trap some air and put it in a deep freezer to see if the air inside condenses to liquid. Pressure regulating valve ensures targeted pressure is available at the inlet manifold, within a given RPM range, the density of air should remain constant as well since to maintain pressure steady more air is pumped in, that means any tendency of density to lower is curtailed by more mass of air arriving thus maintaining steady density.

Air (and nearly everything else) contracts when it is cooled.
Because you have put it in a sealed container does not alter this.
Are you confusing density with mass.

2nd point I made and you negated it was that in a turbo charged car, turbo compressor is pushing air into the manifold all the time within a given engine speed range, so any loss of pressure due to cooling by an intercooler gets replenished by more air forced in to compensate, loss of pressure, so a steady pressure is mintained, and so like in my example of a closed lid can, if you take two cans and in one you put normal atmospehric pressure (air) and in another you put 2x atm, now you got two jars where one with higher pressure has more density.

I thought I was the only one NOT saying that.

As for dynamics of a turbo charging, it is no different to a voltage regulator, a voltage regulator regulates precise voltage irrespective of temperature varaition and load, its job is to supply current within its designed range of operation, same way a turbo charging system will maintain a certain amount of pressure at the inlet manifold irrespective of cooling or not cooling, because pressure is regulated by a pressure regulating valve, known as a dump valve, where a minimum pressure is maintained within a certain RPM range,

Yes, but if the air is cooler it will contain more oxygen by volume.

So no matter how much cooling is being done to the incoming compressed air, if it cools down too much, the pressure will drop, if pressure drops then more air will be forced or pumped in to maintain pressure, so when pressure is kept constant, then density should not change, even through cooling by an intercooler,

That's where you are going wrong, then; are you thinking of mass again?

 

[Nozzle]

That's not right ELI, I'm sorry you need to re-think your mental model. The air will only contract if the sealed rigid container lets it. The pressure will drop, yes - but contraction only follows if the container collapses. If it's a balloon, the balloon will shrink and expand accordingly such that the pressures inside and out match.

Nozzle

 

[JohnW2]

Air (and nearly everything else) contracts when it is cooled.

Eh, that's surely untrue as a generalisation? Gas in a sealed container will always fill that container, regardless of anything (provided it remains as gas), and therefore cannot 'contract' or 'expand' (i.e. change in volume).

Kind Regards, John
Edit: too slow again!

 

[EFLImpudence]

That's not right ELI, I'm sorry you need to re-think your mental model. The air will only contract if the sealed rigid container lets it. The pressure will drop, yes - but contraction only follows if the container collapses. If it's a balloon, the balloon will shrink and expand accordingly such that the pressures inside and out match.

Ok. that's a fair comment but if sufficient cooling and contraction the container will collapse.


These sealed containers are only confusing the engine comparisons where there is no sealed container.

 

[Mikefromlondon]

We are doing good, the title of this thread should now be changed to Turbo charging with and without Intercooler.
earth sleeving is the main reason why we ended ended up here!

Any ways, efli, i found this article in Wikipedia, which seems to agree with what you have said, so perhaps you could trubo boost your argument and back it up with this article extract:
Intercooling[edit]
Main article: Intercooler
An unavoidable side-effect of forced induction is that compressing air raises its temperature.[1]:70 As a result, the charge density is reduced and the cylinders receive less air than the system’s boost pressure prescribes. The risk of detonation, or "knock", greatly increases. These drawbacks are countered by charge-air cooling, which passes the air leaving the turbocharger or supercharger through a heat exchanger typically called an intercooler. This is done by cooling the charge air with an ambient flow of either air (air-air intercooler) or liquid (liquid-to-air intercooler). The charge air density is increased and the temperature is reduced. In this way an intercooler can greatly increase the ability to run higher absolute compression ratios and take full advantage of using compressors in series. The only drawbacks of intercooling are the intercooler's size (typically close to the size of a radiator), and the associated plumbing and piping.

Water injection[edit]