Flamespeed calculation in G equation model
 

Hi，

I wanted to use the G equation model to calculate the combustion process of a PFI gasoline engine, but I encountered the following problems：

1. I have imported a laminar flame velocity table into G equation model, why do I need to set at, ap, mt, mp, and dilution species mass fraction to calculate laminar flamespeed?
2. Is the laminar flow flame velocity I calculated using the 0-D simulation sl or sl_ref?
3. I learned that there are two exponents that need to be benchmarked against the experiment, are these two exponents Temperature exponents constant(γ) and Pressure exponents constant(β)?
4. Are Temperature exponent slope(mt) and Pressure exponent slope(mp) used to calculate instantaneous local γ and β? If combustion is carried out at a chemical equivalent ratio, do the values of mt and mp not affect the calculation of the laminar flamespeed?

Thanks for your help.

Hi Hao,

1. if you use the laminar flame speed table those constants are not used for flame speed calculations.

2. the flame speed you calculate using 1D-simulation is sl.

3. you need to benchmark your laminar flame speed against the experiment. Those constants are just curve fitting values.

4. The values of mt and mp are obtained from different correlations and that will affect your calculation of flame speed. You can look into the equations in our manual. If you use a user specified table the laminar flame speed values are read directly.

Hi, Achyuth, thank you for your reply. I want to ask you a new question. I found that the G equation could not simulate the hysteresis period, so in order to make the maximum cylinder pressure the same as the test, I needed to postpone the ignition angle, which caused the cylinder pressure to grow significantly slower before the compression top dead center during the compression stroke, and there was a significant gap from the test cylinder pressure. How can I solve the problem of slower cylinder pressure growth near top dead center?