Engine exhaust flow rate

[scMechE]

Hello Everybody!

I'm designing an exhaust system for a turbocharged, diesel, 4.4 liters engine. I have the technical data provided by the manufacturer and it states that the engine will produce 505 cfm as the maximum exhaust flow rate. The problem is that it doesn't say if this flow rate is before the turbo or after it.

For turbocharged engines, what flow rate is usually provided by manufacturers? The one before the turbo or the one after it? Where does this value sounds more logical? Before the turbo? After the turbo?

The exhaust gas temperature in manifold is 995ºF.

Thanks in advance!

 

[IceStationZebra]

Without knowing more, I would assume post turbo. Why would the end user need to know what the CFM is pre-turbo? They give you this number to help size the exhaust system. ISZ

 

[dgallup]

Typically flow ratess are given as scfm (at standard conditions, although the definition of standard can vary). In that case, it does not matter where it is measured, the flow will be the same. Conservation of mass and all that.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[MikeHalloran]

Engine manufacturers nearly always give exhaust gas flow data
AFTER the turbo, using
ACTUAL cfm, i.e. volume flow at the stated temperature.

The stated temperature is near the high end of the typical range for temperatures AFTER the turbo for a Diesel. Manifold temperatures, before the turbo, are usually quite a bit higher. The difference is where the turbo gets its energy. ... but manifold numbers are of no interest to an exhaust system designer.

For your first/only unit, you'll want to drill and tap the flange that connects to the turbo, typically two holes x 1/4 NPT so you can insert a pyrometer probe and measure the static (back)pressure at the tube ID.

Engine manufacturers always insist on a backpressure measurement "at" the turbo flange before approving an application, but they rarely provide the pressure tap, I guess to save the cost of a plug.



Mike Halloran
Pembroke Pines, FL, USA

 

[IceStationZebra]

"it does not matter where it is measured, the flow will be the same. Conservation of mass and all that."

I agree about conservation of mass, but if one wanted to get nit picky thete is the potential EGR taking flow before the turbo depending on the emissions equipment fitted. ISZ