# CFD Simulations AC2-06

**The confined TECFLAM swirling natural gas burner**

**Application Challenge 2-06** © copyright ERCOFTAC 2004

**Overview of CFD Simulations**

Simulations are available for this test case applying a variety of turbulence models (i.e. standard k,e, RNG k,ε and Reynolds-Stress models) and chemistry models (i.e. finite rate chemistry, flamelet approach, b-PDF, ILDM, and Monte-Carlo-PDF reaction models). The calculations have been carried out by different groups from EKT Darmstadt, EBI Karlsruhe and DLR Stuttgart. These include grid sensitivity studies as well as studies investigating several effects of boundary conditions. Recently LES calculations started at Imperial College.

Most CFD calculations within the TECFLAM project have bee carried out for the swirl number of S=0.8. The TECFLAM test case has also been chosen as a standard flame at the International workshop on measurement and computation of turbulent non-premixed flames (see Proc. 5th Int. workshop on measurement and computation of turbulent non-premixed flames (2000), http://public.ca.sandia.gov/TNF/5thWorkshop/TNF5.html)

**Simulation Case**

**Solution strategy**

Calculations carried out at EKT Darmstadt use a 2-D elliptic finite volume method applying the SIMPLEC pressure correction and a TDMA solver. A Monte-Carlo PDF transport approach with 100 particles per cell was applied in combination with ILDM tables for the chemistry tabulation. Alternatively a b-PDF approach was used also in combination with ILDM chemistry tabulation.

**Computational Domain**

The grid comprises out of 80 axial and 60 radial grid points that are condensed around the reaction zone. Instead of modeling the geometry of the swirler measured profiles at the inlet of the combustion chamber (which is the outlet of the swirl generator) were used.

**Boundary Conditions**

At the wall adiabatic boundary conditions were applied together with wall functions for the turbulence. The outflow was assumed to have parabolic character. For the center-line symmetry boundary conditions were used. For the velocity and also the turbulent quantities at the inlet LDV measurements near the nozzle have been used. The flow rates of fuel and air needed to be adjusted to match the experimental values at h = 1 mm. The dissipation rate was prescribed based on integral length scale.

**Application of Physical Models**

A Monte-Carlo PDF transport approach with 100 particles per cell was applied in combination with ILDM tables for the chemistry tabulation. The information exchange between the flow and the chemistry solver is iterative. Alternatively a b-PDF approach was used also in combination with ILDM chemistry tabulation. Typical calculation times on a DEC alpha-workstation were 10 hours for the b-PDF and 140 hours for the Monte-Carlo PDF approach.

**CFD Results**

Examples for the computational results will be discussed in section in the evaluation section

© copyright ERCOFTAC 2004

Contributors: Stefan Hohmann - MTU Aero Engines

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