Hi guys! I am working on a personal project of designing and analyzing air swirler of combustion chamber in gas turbine engines. I took a research paper as base, and tried to replicate their results using their values in both geometry and CFD analysis so that I can use that as validation for my own work. I would like to highlight that this is a cold flow cfd analysis.

In the first image, the results plotted for axial velocity and axial positions at each point, are from 8 blade axisymmetric vane angle air swirler. Even if we change the number of vanes or change the mass flow rate, the trend of the graph remains almost identical.

In the second image, the results are from the non-axisymmetric vane angle with the same number of blades and other geometric features. But the difference in the values of axial velocity is unfathomable.

The non-axisymmetric model simulation has a completely diverged solution and spiking residuals, due to which the calculations stop and fail, as shown in the third image.

The models used for both the simulations are the Steady-state RANS model for SST and k-ϵ. This was used for the axisymmetric vane angle model, and it gave the expected results but didn't work for the non-axisymmetric model. Then I tried with k-ϵ RNG, realizable, laminar, and Transient. The outcome was the same. The solutions diverge completely and residual spikes. Even adding a sphere of influence at the immediate downstream of the swirler and making fine mesh, which led to me to 1.9 million elements, still was not giving anything close to practical values.

I am still learning ANSYS Fluent analysis. I am still not well versed in understanding the problem and rectifying it. I have a gut feeling that this problem might be because of the non-axisymmetric vane angle, which might have caused the unsteady flow or something along the lines. I hope you guys can help me. Thank you for your time.