EGR composition

shahrbanoo · January 6, 2014, 09:34

Hi..
what does it mean when we give EGR composition 1?

kschi · January 10, 2014, 07:09

Hi,
composition 1 means that the O2 is fully burnt (equi. ratio=1) and only CO2, H2O and N2 inside the domain is initialised.

With composition 1.1 you would have unburnt fuel because the "combustion before" is rich (equi=1.1). Composition 0.8 would mean that you would have also unburned O2 (equi=0.8, lean combustion) inside the domain.

br

shahrbanoo · January 14, 2014, 14:02

thanks for your response
but EGR composition cannot be more than 1

kschi · January 15, 2014, 02:13

It can be more than 1 because it is not the mass fraction! This is defined with "EGR mass fraction".
Composition is related to the species which are initalised (or at the boundary condition), as already mentioned the initalised EGR can have unburnt O2 or unburnet fuel or all is burnt (composition=1, equi ratio of the mixture which the EGR is based on is 1).

cfdvenkatesh · May 16, 2014, 13:24

Dear kschi,
You are correct about kschi. But I remember seeing somewhere in the FIRE manual, that we cannot model rich EGR ( that is EGR with unburned fuel). FIRE always assumes that EGR doesn't contain fuel. IF we have to model Rich EGR we should use general transport model. Have you tried to simulate rich EGR with standard transport model.

January 6, 2014, 09:34	EGR composition	#1
shahrbanoo Member shahrbanoo Join Date: Mar 2013 Posts: 63 Rep Power: 13	Hi.. what does it mean when we give EGR composition 1?

January 10, 2014, 07:09		#2
kschi New Member Join Date: Jul 2012 Posts: 7 Rep Power: 13	Hi, composition 1 means that the O2 is fully burnt (equi. ratio=1) and only CO2, H2O and N2 inside the domain is initialised. With composition 1.1 you would have unburnt fuel because the "combustion before" is rich (equi=1.1). Composition 0.8 would mean that you would have also unburned O2 (equi=0.8, lean combustion) inside the domain. br turaj likes this.

May 16, 2014, 13:24		#5
cfdvenkatesh New Member Venkatesh V Join Date: Sep 2009 Posts: 24 Rep Power: 16	Dear kschi, You are correct about kschi. But I remember seeing somewhere in the FIRE manual, that we cannot model rich EGR ( that is EGR with unburned fuel). FIRE always assumes that EGR doesn't contain fuel. IF we have to model Rich EGR we should use general transport model. Have you tried to simulate rich EGR with standard transport model. turaj likes this.

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January 14, 2014, 14:02		#3
shahrbanoo Member shahrbanoo Join Date: Mar 2013 Posts: 63 Rep Power: 13	thanks for your response but EGR composition cannot be more than 1

January 15, 2014, 02:13		#4
kschi New Member Join Date: Jul 2012 Posts: 7 Rep Power: 13	It can be more than 1 because it is not the mass fraction! This is defined with "EGR mass fraction". Composition is related to the species which are initalised (or at the boundary condition), as already mentioned the initalised EGR can have unburnt O2 or unburnet fuel or all is burnt (composition=1, equi ratio of the mixture which the EGR is based on is 1).