Setting the equivalence ratio

M-J-Hastings · February 28, 2017, 03:49

Hello,

I am trying to accurately model a non premixed diesel compression-combustion dual stroke.

I understand how to set the mixture fractions in Ansys Setup: in my fuel injection stream: Diesel=1; in my chamber air mixture: n2=0.76, o2=0.23, co2/h20=small.
However, although this ensures the correct mixture fraction ratios in the chamber, it does not ensure the correct mass of oxygen for stoichiometric combustion.
As far as I can see, the only way to set the equivalence ratio is to: set your engine dimensions; calculate the mass of oxygen based on the volume, volume ratio and material properties; tailor your fuel injection profiles such that stoichiometric conditions are achieved.

Is this the only way?

Thank you in advance.

Sent from my SM-J320FN using CFD Online Forum mobile app

LuckyTran · March 2, 2017, 16:13

Yes that is the only way.

Actually, in real life that is how you do it also. The hand of God does not just shove more air into your combustion chamber for you.

February 28, 2017, 03:49	Setting the equivalence ratio	#1
M-J-Hastings New Member Matthew Hastings Join Date: Feb 2017 Location: Southampton Posts: 2 Rep Power: 0	Hello, I am trying to accurately model a non premixed diesel compression-combustion dual stroke. I understand how to set the mixture fractions in Ansys Setup: in my fuel injection stream: Diesel=1; in my chamber air mixture: n2=0.76, o2=0.23, co2/h20=small. However, although this ensures the correct mixture fraction ratios in the chamber, it does not ensure the correct mass of oxygen for stoichiometric combustion. As far as I can see, the only way to set the equivalence ratio is to: set your engine dimensions; calculate the mass of oxygen based on the volume, volume ratio and material properties; tailor your fuel injection profiles such that stoichiometric conditions are achieved. Is this the only way? Thank you in advance. Sent from my SM-J320FN using CFD Online Forum mobile app

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March 2, 2017, 16:13		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,754 Rep Power: 66	Yes that is the only way. Actually, in real life that is how you do it also. The hand of God does not just shove more air into your combustion chamber for you.