Encyclopaedia Index

Contents

  1. Exemplification
  2. Trivial Decomposition Reaction in 2D Flow
  3. Trivial Thermal Diffusion Cases in 1D/2D
  4. Transient Constant Pressure Reaction in 0D
  5. Plug Flow Reactor Case in 1D
  6. Laminar Premixed Flame in 1D

8. Exemplification

A number of Q1 files for exemplary cases are supplied with the CHEMKIN interface in the CHMLIB library. These cases are accessed by way of the CHEMICAL REACTION EXAMPLES menu panel or by SEELIB(C) and LOAD(C...) when using the SATELLITE in interactive mode.

Some of the cases supplied are nearly trivial and seek only to demonstrate the way settings are made, and the veracity of the solutions obtained. The cases provided are listed below and followed by some brief descriptions:

Case C209: H2 Decomposition Reaction in 1D Flow

A reactant, named H2 for convenience, flows into the solution domain at the WEST end and decomposes into H atoms. The reaction is specified in the file

with a constant reaction rate.

8.2 Trivial Decomposition Reaction in 2D Flow

So far as the chemistry is concerned these cases are the same as for the previous case. There are blockages created using either porosities or solid (>100) values of the PRPS variable, and it is the interaction of blockages with the CHEMKIN interface that these case are intended to demonstrate.

8.3 Trivial Thermal Diffusion Cases in 1D/2D

There is no reaction, but a temperature gradient and a source of H2 in N2 is supplied. In the 1D case the thermal diffusion flux opposes or supports the convective mass-flux depending upon the sign of the temperature gradient leading to steeper or shallower concentration gradients. In the 2D case there is also a temperature gradient in the cross-flow direction leading to the establishment of a cross-flow concentration gradient. The gas components are specified in the file

8.4 Transient Constant Pressure Reaction in 0D

This case is a realisation of the CONP case supplied with CHEMKIN as an example. A mixture of H2, O2, and N2 at 1000 K is allowed to react without heat losses at constant pressure.

The PHOENICS case requires many more time-steps than appear in the output quoted in the CHEMKIN manual partly because the VODE solve, used in CONP takes internal time-steps, and partly because the VODE algorithm is of higher temporal order of accuracy. The case is set up so that a run of AUTOPLOT, with an AUTOPLOT USE file U containing

will produce a series of plots of the time evolution of the system.

8.5 Plug Flow Reactor Case in 1D

The base version supplied has 2 cells and appears in three variants; y-direction, z-direction elliptic, and z-direction parabolic.

Each of these variants may be solved using the built-in PHOENICS solver, or the implicit PBP algorithm. The superiority of the implicit PBP algorithm is clearly seen if a comparison is made.

The base cases duplicate the example case supplied with the CHEMKIN PSR application, and a comparison of the solution for cell 1 with the PSR solution shows good agreement.

8.6 Laminar Premixed Flame in 1D

This case is supplied in two versions; a y-direction and a z-direction case. An expanding grid in two parts is used to provide fine resolution in the region of steep variable gradients close to the burner, and to allow a coarse resolution of the long post-flame "tail" in which equilibrium is achieved relatively slowly by recombination of H-atoms.

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