5 Replies Latest reply on Feb 14, 2011 4:15 PM by David Harrold

    Flow simulation of a Mixer

    Jegan Cheng

      Hi everyone,

                    Im a  doin internal flow simulation of an air fuel mixer in which two fluids(air and methane) mixes together in a venturi type mixer.

      I didnt find any tutorial regarding fluid mixing in SW. I face problems in setting up the boundary conditions for this case.

      Also, how to create lids for non-planar surfacace since i need to close the 12 methane inlets as ahown in the attachments below

      Looking for solution.....it will be very much appreciated if anyone can guide me.

      Thank You

        • Re: Flow simulation of a Mixer
          Rich Bayless

          Hello,

           

          you may want to extend the inlets and the outlet by at least 4 or 5 diameters.  In particular, I'd add the piping that feeds the 12 methane inlets. Join the 12 methane inlets to form an inlet manifold, so you will end with only one methane inlet.  I'd start the methane piping right after the gas valve, splitting the piping as needed to feed the 12 holes in the venturi throat.

           

          As you noted, you must use planar faces to add lids, so that's another reason to extend the methane piping.

           

          Once your model has two inlets and one outlet, then simply apply the desired incoming mass flows to the gas inlet and to the air inlet, and set the outlet to environmental pressure.

           

          Hope this helps,  Rich.

            • Re: Flow simulation of a Mixer
              Jegan Cheng

              Hello Rich,

                        Thank u very much for the assistance....ive overcomed that problem!! i managed to close all the opennings as u said.

              Now, i would like to find out the Air Fuel ratio( which is simply the mass flow rate of air divided by the mass flow rate of methane) at outlet.

              I only able to get the mass flow rate(from surface parameters) of the mixture at outlet...is there any option to find out the mass flow rate for air and methane seperately as my main objective is to find out the A/F ratio ??

                • Re: Flow simulation of a Mixer
                  Rich Bayless

                  Hello,

                   

                  How you set up each boundary condition should depend on your upstream and downstream equipment.

                   

                  For example, if you have fan pushing air into the mixer and a gas pressure regulator valve pushing methane into the mixer, and the outlet is to atmosphere, then specify an inlet pressure at the methane inlet and an inlet pressure at the air inlet, environment pressure at the outlet and let Flow Sim calculate the mass flows.

                   

                  Or, if you have an exhaust fan pulling the gases through the mixer, and a gas pressure regulator valve feeding methane, then set enviroment pressure at the air inlet, gas pressure at the methane inlet, and negative pressure at the exit of the mixer.

                   

                  In either case, use surface parameters to find out the mass flow at each inlet, which will give you the air/fuel ratio of the model.

                   

                  Add a surface plot of concentration at the outlet, to visualize the mixing of the two components.

                   

                  Hope this helps,  Rich.

                    • Re: Flow simulation of a Mixer
                      Jegan Cheng

                      hello Rich,

                                    Thank you once again!!

                      You mean i just need to get the mass flow rate of air and methane at their respective inlet.Then, compute AF Ratio from that?? If that the case, i think i got it Rich...By the way,  i would like to view the gas mixing as in the figure(attachment),i can view similar to that using trajectories but the mixing process is not obvious..

                      What else the option available to view my result such way??