[Fadzli]

Hi all,

I'm currently investigating soot particles from engine combustion. There are 3 soot models available in Converge; Hiroyasu (no soot size result), Method of Moment (average soot size) and Sectional Method (size in PSDF). Using Sectional Method as most advance model, there are results of soot size distribution (PSDF) along crank angle, but I'm not so sure what does it means since PSDF is unitless.
For example, for soot size of 1 nm, during 0 CA, the PSDF was 45. So I'm not sure what is the value of 45 means? So anyone can help me what is PSDF actually mean? Or how can I calculate the average soot size during 0 CA?

[xieshengbai]

Hi,

The mathematical definition of PSDF in CONVERGE is d(N)/d(log(dp))/N, where N is the number density (mol/m^3) and dp is the soot diameter. If you integrate the PSDF from size 0 to infinity the result will be 1.0. Therefore the value of PSDF indicates how much percentage of soot for particular soot size, calculated based on number density.

The average soot size for each cell can be calculated based on soot number density and volume fraction. In CONVERGE it can be output in post file with keyword soot_size.

Please let me know if there is any confusion.

Originally Posted by Fadzli

Hi all,

I'm currently investigating soot particles from engine combustion. There are 3 soot models available in Converge; Hiroyasu (no soot size result), Method of Moment (average soot size) and Sectional Method (size in PSDF). Using Sectional Method as most advance model, there are results of soot size distribution (PSDF) along crank angle, but I'm not so sure what does it means since PSDF is unitless.
For example, for soot size of 1 nm, during 0 CA, the PSDF was 45. So I'm not sure what is the value of 45 means? So anyone can help me what is PSDF actually mean? Or how can I calculate the average soot size during 0 CA?

[Fadzli]

Thanks xieshengbai for the clarification...
For simple understanding, is that the value of PSDF=45 means that 45%..? If so, I tried to accumulate all the PSDF1 to PSDF20 (20 bins in my case) during certain crank angle, but the value is not 100%. Or maybe I misunderstood something...?

[xieshengbai]

It is not simply summing up. Note that the function is d(N)/d(log(dp))/N. You need to integrate with log(dp).

Originally Posted by Fadzli

Thanks xieshengbai for the clarification...
For simple understanding, is that the value of PSDF=45 means that 45%..? If so, I tried to accumulate all the PSDF1 to PSDF20 (20 bins in my case) during certain crank angle, but the value is not 100%. Or maybe I misunderstood something...?

[Fadzli]

Originally Posted by xieshengbai

Hi,

The mathematical definition of PSDF in CONVERGE is d(N)/d(log(dp))/N, where N is the number density (mol/m^3) and dp is the soot diameter. If you integrate the PSDF from size 0 to infinity the result will be 1.0. Therefore the value of PSDF indicates how much percentage of soot for particular soot size, calculated based on number density.

The average soot size for each cell can be calculated based on soot number density and volume fraction. In CONVERGE it can be output in post file with keyword soot_size.

Please let me know if there is any confusion.

Thanks xieshengbai,

Do you mind to give one simple example how to calculate PSDF using the equation given...?

Also can you explain how to calculate the average soot size for each cell using soot number density and volume fraction...? Any equation to applied?

I'm sorry for these questions as I'm not quite familiar with the PSDF and still new in CONVERGE.
Thanks in advance..