question about ambient pressure in chamber in fuel spray

- April 11, 2022 at 9:06 am
  
  jjlee
  Subscriber
  
  Hi. I'm doing simulation using Fluent 2020 R2 about fuel spray with reference
  [A comprehensive study of effects of mixing and chemical kinetic models on predictions of n-heptane jet ignitions with the PDF method]
  the data and conditions are based on Sandia Engine combustion network [https://ecn.sandia.gov/ecn-data-search/]
  In the paper above, the 2d symmetry geometry was used
- April 11, 2022 at 10:31 am
  
  Rob
  Ansys Employee
  
  Are you trying to model the injector nozzle or the combustion chamber? The spray injections use the pressure etc to determine droplet sizes and speed, the pressure doesn't otherwise do anything to the solution. Also check the spray models are available in 2d, I'm sure some require a 3d model.
- April 12, 2022 at 8:35 am
  
  jjlee
  Subscriber
  
  Thank you for your comment
  Based on your comment I'm trying to model the combustion chamber using fluent DPM atomizer (pressure-swirl atomizer).
  Plus, I want to ask about your comment "The spray injections use the pressure etc to determine droplet sizes and speed, the pressure doesn't otherwise do anything to the solution".
  Does that mean the 'pressure injection properties' in DPM atomizer doesn't do anything to the solution in spray behavior except droplet sizes and speed?
  
  And I really appreciate if you let me know how to set 'ambient pressure' inside chamber.
  I want to investigate the spray behavior that spray becomes shorter as pressure inside chamber increases!!
- April 12, 2022 at 9:00 am
  
  Rob
  Ansys Employee
  
  Re the spray, read the section of the manual covering the injection types. The spray nozzles are correlations from (I think) diesel and have been in the software since about Fluent 4.
  If the chamber pressure is high, you'll have two effects. The first is the dP from the nozzle is lower, so that will alter the spray characteristics. The second is the fluid (gas) density will be significantly higher, and that'll tend to increase the drag on the droplets. To increase the pressure you just need to either increase the operating pressure or the outlet pressure, but remember to alter the fluid density!
- April 12, 2022 at 1:09 pm
  
  jjlee
  Subscriber
  
  Thank you for your answer!
  I think I can do it thanks to your comment.
  Have a good day :)

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