# Calculation scavenging profile from 2 stroke engine simulation

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 October 24, 2017, 02:38 Calculation scavenging profile from 2 stroke engine simulation #1 New Member   Hyojeong Lee Join Date: Sep 2016 Posts: 8 Rep Power: 3 Hi, I'm trying to calculate Scavenging profile from the result of gas combustion simulation of 2 stroke engine. I want to use the profile for GT 1-D simulation. GT explains Scavenging profile as follows: Scavenging The following two attributes establish the scavenging profile. (Scavenging profile: the relationship between the cylinder residual ratio and the exhaust residual ratio during the period when both the intake and exhaust valves are open.) - Cylinder Residual Ratio : Array of instantaneous cylinder residual from 0.0 to 1.0. The cylinder residual ratio is defined as the ratio of the burned mass in the cylinder to the total mass in the cylinder. A value of 0.0 indicates that the whole contents of the cylinder are fresh air and unburned fuel. A value of 1.0 indicates that the whole contents of the cylinder are burned gases. - Exhaust Residual Ratio : Array of instantaneous exhaust residual ratios corresponding to Cylinder Residual Ratio. The exhaust residual ratio is the ratio of the mass of burned gases exiting the cylinder to the total mass exiting the cylinder. The problem is that both the fresh air and the burned gas includes N2 and O2. From the *.out file I can find the mass of all species in the cylinder and exiting the cylinder. But I don't know where N2 and O2 belong. Is it possible to distinguish N2, O2 of the fresh air and N2, O2 of the burned gas(I believe the burned gas means all gas existing in the cylinder before opening of the intake and exhaust valves.) or not in CONVERGE simulation. Thanks in advance for any help!

October 24, 2017, 05:53
#2
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Tobias
Join Date: May 2016
Location: Germany
Posts: 158
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Quote:
 Originally Posted by hebe2u. Is it possible to distinguish N2, O2 of the fresh air and N2, O2 of the burned gas
You could work with passives, so all incoming fresh air is marked with a passive called "Air" for example, and from initialization you add a passive to the burned gas called "EGR".

What is your burned gas O2 content?
Alternativly you can calculate the N2 mass belonging to your air (23.3 O2/66.7 N2) with the help of the present O2 mass in the cylinder. Then the rest would be real burned gas (no O2).

 November 2, 2017, 04:40 #3 New Member   Chris Pounds Join Date: May 2015 Posts: 21 Rep Power: 4 Hi, Are you still looking for help with this problem? I have a solution but it will take a while to write.

 November 7, 2017, 17:23 #4 Member     Tristan Burton Join Date: Sep 2017 Posts: 79 Rep Power: 2 Hyojeong, When I calculated scavenging schedules from CONVERGE data in the past, I used passives as described in some of the other posts here. Fill the cylinder with a passive named exhaust set to 1 just before EPO, then monitor the mass of exhaust in the cylinder during blowdown and scavenging (divide it by total mass to get cylinder residual ratio). Also, turn on inter-region flow rate reporting to get the mass flow rate of the exhaust passive at the ports (divide by total mass flow rate to get exhaust residual ratio). You'll have to decide how you want to handle back flow across the ports, if it occurs. Best regards, Tristan __________________ Tristan Burton Senior Principal Engineer CONVERGECFD

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