Opposed-flow diffusion flame

This example uses the CounterFlowDiffusionFlame object to solve an opposed-flow diffusion flame for Ethane in Air. This example is the same as the diffusion_flame.py example without radiation.

Requires: cantera >= 3.2.0

Tags: Matlab combustion 1D flow strained flame diffusion flame plotting

Problem Definition

tic  % total running time of the script
help diffusion_flame

runtime = cputime;  % Record the starting time

Set parameter values

p = OneAtm;  % Pressure
tin = 300.0;  % Inlet temperature
mdot_o = 0.72;  % Air mass flux, kg/m^2/s
mdot_f = 0.24;  % Fuel mass flux, kg/m^2/s
transport = 'mixture-averaged';  % Transport model

Set-up initial grid, loglevel, tolerances. Enable/Disable grid refinement

width = 0.02;
nz = 11;

tol_ss = {1.0e-5, 1.0e-9};  % {rtol atol} for steady-state problem
tol_ts = {1.0e-3, 1.0e-9};  % {rtol atol} for time stepping
logLevel = 1;  % Amount of diagnostic output (0 to 5)
refineGrid = 1;  % 1 to enable refinement, 0 to disable

Create the gas object for the fuel and oxidizer streams

This object will be used to evaluate all thermodynamic, kinetic, and transport properties.

gas = Solution('gri30.yaml', 'gri30', transport);
oxcomp = 'O2:0.21, N2:0.78';  % Air composition
fuelcomp = 'C2H6:1';  % Fuel composition

Set up the flow object

For this problem, the AxisymmetricFlow model is needed. Set the state of the flow as the fuel gas object. This is arbitrary and is only used to initialize the flow object. Set the grid to the initial grid defined prior, same for the tolerances.

flow = AxisymmetricFlow(gas, 'flow');
flow.P = p;
flow.setupUniformGrid(nz, width, 0.0);
flow.setSteadyTolerances(tol_ss{:}, 'default');
flow.setTransientTolerances(tol_ts{:}, 'default');

Create the fuel and oxidizer inlet steams

Specify the temperature, mass flux, and composition correspondingly.

% Set the fuel inlet.
gas.TPX = {tin, p, fuelcomp};
inlet_f = Inlet(gas, 'fuel_inlet');
inlet_f.massFlux = mdot_f;

% Set the oxidizer inlet.
gas.TPX = {tin, p, oxcomp};
inlet_o = Inlet(gas, 'air_inlet');
inlet_o.massFlux = mdot_o;

Create the flame object

Once the inlets have been created, they can be assembled to create the flame object. The object CounterFlowDiffusionFlame sets up the initial guess for the solution using a Burke-Schumann flame. The input parameters are: fuel inlet object, flow object, oxidizer inlet object, and, optionally, the name of the oxidizer species.

fl = CounterFlowDiffusionFlame(inlet_f, flow, inlet_o);

Solution

Solve with fixed temperature profile

Grid refinement is turned off for this process in this example. To turn grid refinement on, change 0 to 1 for last input is solve function.

fl.solve(logLevel, 0);

Enable the energy equation

The energy equation will now be solved to compute the temperature profile. We also tighten the grid refinement criteria to get an accurate final solution. The explanation of the setRefineCriteria function is located on cantera.org in the Matlab User’s Guide and can be accessed by help setRefineCriteria.

flow.energyEnabled = true;
flow.setRefineCriteria(200.0, 0.1, 0.2);
fl.solve(logLevel, refineGrid);

Show statistics and display results

Show statistics of solution and elapsed time

fl.writeStats;
elapsed = cputime - runtime;
e = sprintf('Elapsed CPU time: %10.4g', elapsed);
disp(e);
toc

%%
% Make a single plot showing temperature and mass fraction of select
% species along axial distance from fuel inlet to air inlet.

figure(1);
subplot(2, 3, 1);
plotSolution(flow, 'T', 'Temperature [K]');
subplot(2, 3, 2);
plotSolution(flow, 'velocity', 'Axial Velocity [m/s]');
subplot(2, 3, 3);
plotSolution(flow, 'O2', 'O2 Mass Fraction');
subplot(2, 3, 4);
plotSolution(flow, 'H2O', 'H2O Mass Fraction');
subplot(2, 3, 5);
plotSolution(flow, 'C2H6', 'C2H6 Mass Fraction');
subplot(2, 3, 6);
plotSolution(flow, 'CO2', 'CO2 Mass Fraction');

Plotting Utility

function plotSolution(domain, component, titleStr)
    % Utility for plotting a specific solution component
    z = domain.grid;
    x = domain.values(component);
    plot(z, x);
    xlabel('z (m)');
    ylabel(component);
    title(titleStr);
end