Exhaust gas volumetric flow rate

[alibabaaaa]

Does anyone have an indication of the exhaust gas volumetric flow rate of diesel engines?

I read in this graph:

http://www.sokken.co.jp/files/products/AirFlowmeters/modal_JE05-1.PNG

from this webpage:

http://www.sokken.co.jp/en/flow/201011/entry3.html

that for a 4L diesel engine, the maximum volumetric flow rate is 5m3/min which is 83.3L/sec.

This seems quite huge, does anyone have any indication for a diesel engine eg 2L?
I know it depends on temperature, but I am after an indicative number.

 

[BrianPetersen]

The maximum intake mass flow rate will be pretty easily estimated based on the displacement, RPM, and intake temperature and pressure. Obviously the exhaust mass flow rate will be the intake mass flow rate plus the fuel flow rate, which is small by comparison and for this purpose can be neglected. (With respect to the intake temperature and pressure ... watch out for forced induction ... most diesels nowadays are turbocharged ... just make sure you account for it correctly.)

The exhaust volume flow rate will be strongly dependent on temperature, and that will be strongly dependent on engine load and on how far down the exhaust pipe that you care about the number ...

P V = n R T

 

[SomptingGuy]

If you are doing simple (mass conservation) hand calcs, you'll need to account for the EGR rate too.

Steve

 

[RodRico]

Just to added to BrianPetersen's and SomtingGuy's spot-on responses, note that the PV=nRT calculation (which is the one you want to use when estimating volumetric flow) is heavily influenced by volumetric efficiency, compression ratio, and air/fuel ratio as well... volumetric efficiency dictates how much air mass is actually present in the cylinder, compression ratio dictates the initial temperature of combustion, and the fuel load dictates how much heat is released into the air during combustion.

 

[SwinnyGG]

You can get rough estimates by calculating backward from rated power. EGTs are known within a relatively small range, which would give you volumetric flow rate at the port. As others have stated as you move downstream the mass flow rate will not change but temperature drop will change the volumetric flow rate accordingly.

 

[JayMaechtlen]

ok, how would egr change mass flow rate?



Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[SwinnyGG]

EGR removes exhaust gas from the stream and sends it somewhere other than out the exhaust.

So if your measurement point is upstream of the EGR valve, mass flow rate does not change. If you're measuring downstream of the EGR valve, MFR changes based on EGR opening.

 

[RodRico]

Jay,

Per Wikipedia, "In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. This dilutes the O2 in the incoming air stream and provides gases inert to combustion to act as absorbents of combustion heat to reduce peak in-cylinder temperatures. NOx is produced in a narrow band of high cylinder temperatures and pressures."

Obviously, the exhaust gas is relatively hot relative to normal intake charge, and so it reduces intake mass. Furthermore, reduction in O2 means there must be a corresponding reduction in fuel load, and that too reduces mass. Your original question, however, related to volumetric flow rate, and the whole point of EGR is to reduce combustion temperature by absorbing some of the heat and reducing the amount of fuel/O2 charge, and this temperature reduction reduces exhaust gas volume.

Rod