43bd96b5ba
The CounterFlowDiffusionFlame (CFDF) code is able to perform more general cases of npflame_init for multiple species fuel and oxidizer streams. The stoichiometric mixture fraction in the CFDF code uses the Bilger definition of mixture fraction, using the conservation of elements C, H, and O. This method is used in the python module, but not the MATLAB npflame_init function. Also, the CFDF code uses the fuel stream density to calculate the fuel stream velocity and the oxidizer stream density to calculate the oxidizer stream velocity, where as the npflame_init code uses the fuel density for both velocity calculations. The elementMassFraction code is a MATLAB version of the python function: elemental_mass_fraction, which is needed to run the CFDF code. Update the diffflame.m example to use the more general CFDF function since the input parameters are different than the npflame_init function. This example is the same as the diffusion_flame.py sample in the Python module.
129 lines
5.4 KiB
Matlab
129 lines
5.4 KiB
Matlab
% DIFFFLAME - An opposed-flow diffusion flame.
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% This example uses the CounterFlowDiffusionFlame function to solve an
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% opposed-flow diffusion flame for Ethane in Air. This example is the same
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% as the diffusion_flame.py example without radiation.
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%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%
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runtime = cputime; % Record the starting time
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Parameter values of inlet streams
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%
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p = oneatm; % Pressure
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tin = 300.0; % Inlet temperature
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mdot_o = 0.72; % Air mass flux, kg/m^2/s
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mdot_f = 0.24; % Fuel mass flux, kg/m^2/s
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rxnmech = 'gri30.xml'; % Reaction mechanism file
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transport = 'Mix'; % Transport model
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% NOTE: Transport model needed if mechanism file does not have transport
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% properties.
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Set-up initial grid, loglevel, tolerances. Enable/Disable grid
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% refinement.
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%
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initial_grid = 0.02*[0.0 0.2 0.4 0.6 0.8 1.0]; % Units: m
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tol_ss = [1.0e-5 1.0e-9]; % [rtol atol] for steady-state problem
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tol_ts = [1.0e-3 1.0e-9]; % [rtol atol] for time stepping
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loglevel = 1; % Amount of diagnostic output (0 to 5)
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refine_grid = 1; % 1 to enable refinement, 0 to disable
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Create the gas objects for the fuel and oxidizer streams. These objects
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% will be used to evaluate all thermodynamic, kinetic, and transport
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% properties.
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%
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fuel = GRI30('Mix');
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ox = GRI30('Mix');
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oxcomp = 'O2:0.21, N2:0.78'; % Air composition
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fuelcomp = 'C2H6:1'; % Fuel composition
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% Set each gas mixture state with the corresponding composition.
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set(fuel,'T', tin, 'P', p, 'X', fuelcomp);
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set(ox,'T',tin,'P',p,'X', oxcomp);
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Set-up the flow object. For this problem, the AxisymmetricFlow model is
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% needed. Set the state of the flow as the fuel gas object. This is
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% arbitrary and is only used to initialize the flow object. Set the grid to
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% the initial grid defined prior, same for the tolerances.
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%
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f = AxisymmetricFlow(fuel,'flow');
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set(f, 'P', p, 'grid', initial_grid);
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set(f, 'tol', tol_ss, 'tol-time', tol_ts);
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Create the fuel and oxidizer inlet steams. Specify the temperature, mass
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% flux, and composition correspondingly.
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%
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% Set the oxidizer inlet.
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inlet_o = Inlet('air_inlet');
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set(inlet_o, 'T', tin, 'MassFlux', mdot_o, 'X', oxcomp);
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%
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% Set the fuel inlet.
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inlet_f = Inlet('fuel_inlet');
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set(inlet_f, 'T', tin, 'MassFlux', mdot_f, 'X', fuelcomp);
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Once the inlets have been created, they can be assembled
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% to create the flame object. Function CounterFlorDiffusionFlame
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% (in Cantera/1D) sets up the initial guess for the solution using a
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% Burke-Schumann flame. The input parameters are: fuel inlet object, flow
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% object, oxidizer inlet object, fuel gas object, oxidizer gas object, and
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% the name of the oxidizer species as in character format.
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%
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fl = CounterFlowDiffusionFlame(inlet_f, f, inlet_o, fuel, ox, 'O2');
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Solve with fixed temperature profile first. Grid refinement is turned off
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% for this process in this example. To turn grid refinement on, change 0 to
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% 1 for last input is solve function.
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%
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solve(fl, loglevel, 0);
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Enable the energy equation. The energy equation will now be solved to
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% compute the temperature profile. We also tighten the grid refinement
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% criteria to get an accurate final solution. The explanation of the
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% setRefineCriteria function is located on cantera.org in the Matlab User's
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% Guide and can be accessed by help setRefineCriteria
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%
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enableEnergy(f);
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setRefineCriteria(fl, 2, 200.0, 0.1, 0.2);
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solve(fl, loglevel, refine_grid);
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saveSoln(fl,'c2h6.xml','energy',['solution with energy equation']);
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Show statistics of solution and elapsed time.
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%
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writeStats(fl);
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elapsed = cputime - runtime;
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e = sprintf('Elapsed CPU time: %10.4g',elapsed);
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disp(e);
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Make a single plot showing temperature and mass fraction of select
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% species along axial distance from fuel inlet to air inlet.
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%
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z = grid(fl, 'flow'); % Get grid points of flow
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spec = speciesNames(fuel); % Get species names in gas
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T = solution(fl, 'flow', 'T'); % Get temperature solution
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for i = 1:length(spec)
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% Get mass fraction of all species from solution
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y(i,:) = solution(fl, 'flow', spec{i});
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end
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j = speciesIndex(fuel, 'O2'); % Get index of O2 in gas object
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k = speciesIndex(fuel, 'H2O'); % Get index of H2O in gas object
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l = speciesIndex(fuel, 'C2H6'); % Get index of C2H6 in gas object
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m = speciesIndex(fuel, 'CO2'); % Get index of CO2 in gas object
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clf;
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yyaxis left
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plot(z,T)
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xlabel('z (m)');
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ylabel('Temperature (K)');
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yyaxis right
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plot(z,y(j,:),'r',z,y(k,:),'g',z,y(l,:),'m',z,y(m,:),'b');
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ylabel('Mass Fraction');
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legend('T','O2','H2O','C2H6','CO2');
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