charge air for engines 2

[dkm0038]

I am studying a design for test engine facility and would like help and inputs on the charge air cooling system.

The heat load was given as 150Kw and that is about it. I am wondering if there is a standard temperature drop used charge air in engines and if the air is typically compressed at all?

Any help would be appreciated.

 

[MikeHalloran]

The phrase "charge air cooler" usually refers to an air-to-air heat exchanger that uses ambient air to cool the combustion air that's just been compressed and heated by a turbocharger. It usually looks a lot like a radiator, and is typically positioned immediately in front of the regular coolant radiator, and uses the same fan.

The temperature drop on the charge air side is 'whatever you can get'. The temperature rise on the atmospheric side needs to be limited so that it doesn't cause problems for the radiator... say 10F if memory serves. Wait; it gets worse; the pressure drop on the air side also has to be limited, again so as to not interfere with the radiator's function.

The CAC is normally part of the engine 'package', so you may be talking about something else... perhaps a cooler to standardize the ambient air used in the test?



Mike Halloran
Pembroke Pines, FL, USA

 

[dkm0038]

These are going to be air cooled units but it is for stationary test engines, the one i mentioned above (150Kw) is for a 13 Liter desiel engine and is designed to opperate at 100F ambient air temp.

Is there any rule of thumb if one knows the engine and heat load to get a rough estimate of the in and out temperature of the charge air??

 

[ivymike]

what brand of engine?

 

[MikeHalloran]

If the CAC is sized right and working right, you hope to get the charge air temp at its exit down to ~130F, from approx ~300F at the turbo exit.

But don't listen to me. Your Diesel's dealer should be able to bury you in information.



Mike Halloran
Pembroke Pines, FL, USA

 

[dkm0038]

I don't know the specific brand, they will switch engines regularl, but the general size will remain the same. It is being designed for the worst case senioro of 100F ambient air and a size of 150Kw

 

[MikeHalloran]

Well then, find out who _thinks_ he's getting the business soon, and ask him, or all of them, for information.



Mike Halloran
Pembroke Pines, FL, USA

 

[Bribyk]

The sizing sounds about right to me. An 18L 425 bhp natural gas engine running ~1 bar of boost rejects about 46 kW from the charge air to the cooling water (air to water exchanger). A diesel's going to be running more boost than this (probably about double this) and the heat rejection should roughly double as well. If you're in doubt buy the next larger size/rating of charge air cooler, it never hurts to have too much cooling especially for future projects or when the exchanger starts to foul.

Mike's numbers seem pretty good to me as well.

 

[dkm0038]

Are the coolers for charge air usually liquid cooled (coolant or water glycol mix)?

 

[Bribyk]

Depends on the engine and application. Stationary and marine engines typically use a separate water/glycol circuit to transfer heat away from the air charge (this circuit is sometimes also used to cool the oil).

Automotive/mobile engines typically use air-to-air exchangers because they're lighter, have less parts and the cooling medium/driving force is "free" and easily accessible.

A 13L diesel sounds like you're testing truck engines to me, which are mostly air-to-air cooled. If you're engine dyno testing these, the easiest method is to put an air-to-water charge air cooler, instead of air-to-air, so you can regulate the temperature better and don't need a huge fan. If they're on a chassis dyno the huge fan is easiest.

 

[MikeHalloran]

The CAC (air cooled), or intercooler (liquid cooled) or aftercooler (liquid cooled, same thing) are part of the engine _package_, which is what gets certified.

It shouldn't even be mentioned in a test facility spec.. except that the heat load is added to the wastewater stream for marine units, or to the ventilation exhaust for mobile units, or to either one for stationary units. That's probably why they didn't tell you much.





Mike Halloran
Pembroke Pines, FL, USA

 

[Bribyk]

It sounds like a dyno manufacturer has put together a package for the OP and he's checking that they've sized everything properly.

"Heat rejection to aftercooler (kW)" is a common specification given by stationary engine manufacturer's but it is for sizing exchangers and/or systems that use the waste heat, not a conformance check specification. I'll have to check ISO 3046 though...