STAR-CD is a general purpose CFD toolkit that is both easy to use and flexible in its application. It allows users to perform wide ranging investigations into their specific area of fluid dynamics. However, industrial users often need to move beyond their current field of expertise in order to conduct more complex or ground breaking analyses. For these occasions CD-adapco’s consultancy group is here to help you take the first step towards extending your CFD horizons. One such industrial case study is described below.

Part of the Department of Environment’s, Food and Rural Affairs strategy for waste management is to recycle and recover energy and materials within waste. With this in mind Compact Power has developed a new advanced thermal conversion technology for a wide range of wastes using pyrolysis, gasification and high temperature oxidation. The technology recovers energy while minimizing emissions.

Compact Power looked to use CD-adapco’s expertise in combustion modeling and flexible geometry generation in designing the thermal oxidizer. The aim of the project was to investigate this design by providing analysis of the residence time and flow characteristics inside the thermal oxidizer. A residence time of 2 seconds at high temperatures is required to ensure destruction of pollutant gases and any particulate residue. Comparisons were made for a series of parametric studies, namely; - variation of the number, size and orientation of gas and oxidizer inlets - changes to the volumetric flux of fuel to oxidizer ratio.

Meshes for STAR-CD can be created using a number of methods. Given the need for flexible geometry generation, the appropriate choice in this case was for a macro-driven meshing process using PROSTAR. Initially, this required additional preparation time, but the time saving during the parametric adjustment stage more than made up for this. Once written, the macro with the parameter changes incor-porated simply needed re-reading into PROSTAR to create the new geometry.

The pyrolysis and gasification process yields a complex range of short-chained hydrocarbons and other simple molecules. A compound analysis of the fuel was provided, and this was used to generate unique relationships between each species concentration and the mixture fraction, based upon a chemical equilibrium assumption. Com bustion was accounted for using the PPDF model and the CHEMKIN database supplied the polynomial rep-resentations for specific heat of all included species.

Simulations provided useful insight into the flow and combustion characteristics. The residence time was shown to be in excess of the design criterion. The exhaust temperature was predicted to within 5 %. Additionally, design changes such as adjustment of the volumetric flux of fuel to oxidizer ratio and alterations of the fuel inlet orientation were used to distribute peak temperatures more evenly within the thermal oxidizer.

Compact Power have taken advantage of the expertise within CD-adapco's consultancy group, and they have in turn been provided with an in-depth analysis of their thermal oxidizer. This has aided the development of their unique technology.

For further details of consultancy at CD-adapco, please contact, either: consultancy@de.cd-adapco.com or +44 (0)20 7471 6200 in Europe and starinfo@us.cd-adapco.com or +1 631 549 2300 in the Americas.