# tg04 - MODELING A COMBUSTION CHAMBER(3-D 4 MODELING A...

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MODELING A COMBUSTION CHAMBER (3-D) © Fluent Inc., Sep-04 4-1 4. MODELING A COMBUSTION CHAMBER (3-D) In this tutorial, you will create the geometry for a burner using a top-down geometry con- struction method in GAMBIT (creating a volume using solids). You will then mesh the burner geometry with an unstructured hexahedral mesh. In this tutorial you will learn how to: Move a volume Subtract one volume from another Shade a volume Intersect two volumes Blend the edges of a volume Create a volume using the sweep face option Prepare the mesh to be read into FLUENT 5/6 4.1 Prerequisites This tutorial assumes that you have worked through Tutorial 1 and you are consequently familiar with the GAMBIT interface.

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Problem Description MODELING A COMBUSTION CHAMBER (3-D) 4-2 © Fluent Inc., Sep-04 4.2 Problem Description The problem to be considered is shown schematically in Figure 4-1. The geometry consists of a simplified fuel injection nozzle that feeds into a combustion chamber. You will only model one quarter of the burner geometry in this tutorial, because of the symmetry of the geometry. The nozzle consists of two concentric pipes with radii of 4 units and 10 units respectively. The edges of the combustion chamber are blended on the wall next to the nozzle. 10 20 30 40 20 12 4 Figure 4-1: Problem specification
MODELING A COMBUSTION CHAMBER (3-D) Strategy © Fluent Inc., Sep-04 4-3 4.3 Strategy In this tutorial, you will create a combustion chamber geometry using the “top-down” construction method. You will create volumes (in this case, bricks and cylinders) and use Boolean operations to unite, intersect, and subtract these volumes to obtain the basic geometry. Finally, using the “blend” command, you will round off some edges to complete the geometry creation. For this model, it is not possible to simply pick the geometry and mesh the entire domain with hexahedral elements, because the Cooper tool (which you will be using in this tutorial) requires two groups of faces, one group topologically parallel to a sweep path, and the other group topologically perpendicular. However, the rounded (blended) edges fit in neither group. See the GAMBIT Modeling Guide for a more detailed description of the Cooper tool. You need to decompose the geometry into portions that can be meshed using the Cooper tool. There are several ways to decompose geometry in GAMBIT. In this example, you will use a method whereby portions of the volume around the blend are split off from the main volume. A detailed description of the decomposition strategy for the combustion chamber is given below. Note that there are several faces in the geometry for which the default meshing scheme is the Pave scheme; most of these faces are perpendicular to the z direction. There are also geometrical protrusions in the z direction, so this should be chosen as the main direction for the Cooper meshing scheme. To make this possible, the paved faces in the x and y directions (the two symmetry planes in the geometry shown in Figure 4-2) must be changed to use the Submap or Map meshing scheme.

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## This note was uploaded on 01/13/2011 for the course MECHANICAL ME:5208 taught by Professor P.k.lele during the Spring '10 term at Jadavpur University.

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tg04 - MODELING A COMBUSTION CHAMBER(3-D 4 MODELING A...

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