CORA3

CORA3 is a finite-difference computer program for predicting fluid flow, heat-transfer and combustion in three-dimensional combustion equipment. Examples are: gas, liquid, solid fuel fired funaces, gas-turbine combustors, chemical reactors, mixers, rocket motors, etc. CORA3 can handle both steady and unsteady three-dimensional flows.

CORA3, in its basic form, solves three momentum equations:-

• the mass-conservation equations for fuel and matter without discrimination;
• the thermal-energy equation; the transport equations for turbulence energy and its dissipation rate; and
• the three equations for the radiant flux sums in the axial, radial and circumferential directions.

CORA3 therefore predicts the three-dimensional fields of:-

• axial velocity component
• radial velocity component
• circumferential (swirl) velocity
• component
• pressure
• temperature
• composition variables (two)
• turbulence characteristics (two)
• radiation characteristics (three)

If any of these variables are not significant, for example if radiation is to be ignored, the relevant equations are easily eradicated.

The space co-ordinates of CORA3 are either Cartesian (x,y and z), or else cylindrical (x, r and q). CORA3 uses a fixed-grid system, evaluating variables at locations of fixed x, y and z (or x, r and q). These locations are arranged on a rectangular or cylindrical grid, the spacing of which may be non-uniform.

The boundaries of the domain of integration can be arbitrary; this means that they need not conform to a rectangular or cylindrical shape, but may exhibit inclinations, curves, etc.

Input Requirements

The user of CORA3 specifies the following:-

• Geometrical shape of the combustion equipment including details such as:

  (i) length;
  (ii) cross-sectional dimensions;
  (iii) location and size of entry ports for fuel and air;
  (iv) location of size of exit port;
  (v) size and location of baffles, if any.

• A set of thermodynamic, transport, chemical-kinetic and radiative properties of fluids such as specific heat, density, viscosity, diffusivity, heat of reaction, emissivity, etc. These quantities may be specified as constant or as a function of local thermodynamic properties.
• Information regarding dependent variables at the boundary of the integration domain, such as:-
  • 
    (i)mass flow rates, velocity components, and fluid properties such as p, T, r, m and e at those parts of the boundary where the fluid enters;

    
    (ii) prescription of temperature or heat flux at the walls;

    
    (iii) fluid condition at the exit boundary, such as pressure.

Output Requirements

CORA3 is provided with several modes of expressing output:-

• Distributions of all relevant quantities such as temperature, fuel mass fractions, etc, by tables of values, by contour plots generated by the line printer or by other graphical output devices.
• Velocity distributions by way of vector plots.
• Heat transfer to the walls, heat content and temperature of exhaust gases and thermal efficiency of the equipment, as tables of numbers.
• Convergence-monitoring information if required.

wbs