14 Replies Latest reply on Dec 7, 2015 1:29 AM by Prabhu Prakash

    Centrifugal Pump analysis

    Prabhu Prakash

      Dear all,

           I have a doubt in analysis of Centrifugal Pump analysis procedure. I have used the following Boundary Conditions.

                Inlet - Pressure opening (101325 Pa) (Pressure potential is not checked in)

                Outlet - Volume flow rate (4m^3 / hr) (Relative to Rotating frame is checked in)

                Wall - casing (stator)

                Rotating Region - 2880 RPM

       

      My goals are: Total Pressure @ outlet and Torque on Impeller along the axis of rotation.

       

      Are my BC and Goals are correct or do I need to change the BC. My output for this BC should be 4.5 bar pressure (45 head in terms of MWC), because this output is achieved by practical pump testing. This pump is a positive suction pump used in food industries. Can you please help me, I am not getting the desired output. what steps should i follow in Calculation Control options. The required output flow rate and its corresponding head is given in the attached image along with Boundary Conditions. What kind of mesh should i follow. Should I go for Local mesh.

      I have attached the steps which i used for my analysis. Kindly look over it and guide me for correct procedure.a.PNG

      b.PNG

      c.PNG 

         d.PNG

      e.PNG

      f.PNG

      1.PNG2.PNG3.PNG4.PNG

       

      5.PNG

       

      For the above settings, i got the following output, but it's not matching for the available datas.

       

      6.PNG

        • Re: Centrifugal Pump analysis
          Rudolf Van den Berg

          Hi Prabhu

           

          I will try and assist you, I am new do this, but learned a lot the past month where I also did a centrifugal pump.

           

          Firslty I will use this local region (sliding) option which is used for rotating bodies.

          Also keep in mind that this is then a time based setup, set the time to 1sec, longer time = longer calculation

          You have to then specify the rotating region by creating a rotating domain.

           

          secondly I will do a surface control to get the torque of the impeller (I assume that is what you want).

          Then select the whole impeller for the surface.

           

           

          then I will also change my time step to manual which will change your calculation time significantly.

           

          For the initial mesh, select a gap size and also select a wall thickness.

          gap size = minimum gap size the fluid are going to pass through

          Wall thickness = thickness of blades (usually)

           

           

          Hope this helps.

           

          Kind regards

            • Re: Centrifugal Pump analysis
              Prabhu Prakash

              Hi Berg.

                   I will try a trial with the steps as you said. Are my Inlet and Outlet conditions are correct...

                   Inlet is Pressure opening

                   Outlet is Volume flow rate

               

              actually i have to crosscheck the following readings which are taken in physical tests.

               

              flow.png

              my inlet pipe is 5 times the suction dia and outlet pipe is 10 times the delivery dia.... Also in Calculation control options > finishing > finish conditions - what are the criterion should I select.

            • Re: Centrifugal Pump analysis
              Prabhu Prakash

              Dear all,

                  

                   Will the solver settings make impact on the results. I mean if I change the travels from auto to manual and give 5 or 6, and if I change the refinement to 3 from 0, what will be the effects. Image have been attached for reference.

               

              solver settings.PNG

               

                   Also during some trials, after completing the solving process, my flow through pump from inlet doesn't reach the impeller region. i.e., the flow stops at the inlet. what can be the possible reasons and remedy....

                • Re: Centrifugal Pump analysis
                  Andrei Popov

                  Don't use any of those settings if you don't understand what they do.

                  Use only iterations or physical time limit. Or you can use goals convergence if your problem is steady state.

                  Disable travels and refinements for now.

                  The travels impose how many domain travels are required for a perturbation to propagate from inlet to outlet, like a shock wave for example, which is not your case.

                  Refinements will do as many mesh refinements required but you don't need that.

                  What you need to do is set the mesh in the mesh menu using narrow channels setting to minimum 5 elements per channel and mesh refinement to 3 or 4, depending on your basic mesh size. refinement 3 means the basic mesh will be divided maximum in 2^3 = 8 times which will give the minimum element size, so make sure the minimum element size x 5 elements per channel is enough to cover your channels.

                  Then cut the domain with a cut plot set the body transparency to 0.5 and see how the mesh is looking inside, it may be that your rotating body that defines the rotating region to be enabled as a solid so you need to disable that solid body to let the software know that the region is fluid volume.

                  Right click on input data in the flow tree, Component Control, highlight whichever part you want to "deactivate" and click the button to the right that says "disable"