initial import
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Dave Goodwin
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Cantera/matlab/cantera/examples/catcomb.m
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239
Cantera/matlab/cantera/examples/catcomb.m
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% CATCOMB -- Catalytic combustion on platinum.
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%
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% This script solves a catalytic combustion problem. A stagnation flow
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% is set up, with a gas inlet 10 cm from a platinum surface at 900
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% K. The lean, premixed methane/air mixture enters at ~ 6 cm/s (0.06
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% kg/m2/s), and burns catalytically on the platinum surface. Gas-phase
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% chemistry is included too, and has some effect very near the
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% surface.
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%
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% The catalytic combustion mechanism is from Deutschman et al., 26th
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% Symp. (Intl.) on Combustion,1996 pp. 1747-1754
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%
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% On a Mac G4, this example takes about 20 sec.
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%
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help catcomb;
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disp('press any key to start the simulation');
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pause;
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clear all;
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cleanup;
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t0 = cputime; % record the starting time
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% Parameter values are collected here to make it easier to modify
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% them
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p = oneatm; % pressure
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tinlet = 300.0; % inlet temperature
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tsurf = 900.0; % surface temperature
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mdot = 0.06; % kg/m^2/s
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transport = 'Mix'; % transport model
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% We will solve first for a hydrogen/air case to
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% use as the initial estimate for the methane/air case
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% composition of the inlet premixed gas for the hydrogen/air case
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comp1 = 'H2:0.05, O2:0.21, N2:0.78, AR:0.01';
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% composition of the inlet premixed gas for the methane/air case
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comp2 = 'CH4:0.095, O2:0.21, N2:0.78, AR:0.01';
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% the initial grid, in meters. The inlet/surface separation is 10 cm.
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initial_grid = [0.0 0.02 0.04 0.06 0.08 0.1]; % m
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% numerical parameters
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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-4 1.0e-9]; % [rtol atol] for time stepping
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loglevel = 1; % amount of diagnostic output
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% (0 to 5)
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refine_grid = 1; % 1 to enable refinement, 0 to
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% disable
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%%%%%%%%%%%%%%% end of parameter list %%%%%%%%%%%%%%%%%%%%%%
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%%%%%%%%%%%%%%%% create the gas object %%%%%%%%%%%%%%%%%%%%%%%%
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%
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% This object will be used to evaluate all thermodynamic, kinetic,
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% and transport properties
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%
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% The gas phase will be taken from the definition of phase 'gas' in
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% input file 'ptcombust.cti,' which is a stripped-down version of
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% GRI-Mech 3.0.
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gas = importPhase('ptcombust.cti','gas');
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set(gas,'T',tinlet,'P',p,'X',comp1);
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%%%%%%%%%%%%%%%% create the interface object %%%%%%%%%%%%%%%%%%
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%
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% This object will be used to evaluate all surface chemical production
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% rates. It will be created from the interface definition 'Pt_surf'
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% in input file 'ptcombust.cti,' which implements the reaction
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% mechanism of Deutschmann et al., 1995 for catalytic combustion on
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% platinum.
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%
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surf_phase = importInterface('ptcombust.cti','Pt_surf',gas);
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setTemperature(surf_phase, tsurf);
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% integrate the coverage equations in time for 1 s, holding the gas
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% composition fixed to generate a good starting estimate for the
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% coverages.
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advanceCoverages(surf_phase, 1.0);
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% The two objects we just created are independent of the problem
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% type -- they are useful in zero-D simulations, 1-D simulations,
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% etc. Now we turn to creating the objects that are specifically
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% for 1-D simulations. These will be 'stacked' together to create
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% the complete simulation.
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%%%%%%%%%%%%%%%% create the flow object %%%%%%%%%%%%%%%%%%%%%%%
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%
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% The flow object is responsible for evaluating the 1D governing
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% equations for the flow. We will initialize it with the gas
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% object, and assign it the name 'flow'.
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%
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flow = AxisymmetricFlow(gas, 'flow');
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% set some parameters for the flow
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set(flow, 'P', p, 'grid', initial_grid, 'tol', tol_ss, 'tol-time', tol_ts);
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%%%%%%%%%%%%%%% create the inlet %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%
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% The temperature, mass flux, and composition (relative molar) may be
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% specified. This object provides the inlet boundary conditions for
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% the flow equations.
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%
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inlt = Inlet('inlet');
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% set the inlet parameters. Start with comp1 (hydrogen/air)
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set(inlt, 'T', tinlet, 'MassFlux', mdot, 'X', comp1);
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%%%%%%%%%%%%%% create the surface %%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%
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% This object provides the surface boundary conditions for the flow
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% equations. By supplying object surface_phase as an argument, the
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% coverage equations for its surface species will be added to the
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% equation set, and used to compute the surface production rates of
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% the gas-phase species.
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%
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surf = Surface('surface', surf_phase);
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setTemperature(surf,tsurf);
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%%%%%%%%%%%%% create the stack %%%%%%%%%%%%
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%
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% Once the component parts have been created, they can be assembled
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% to create the 1D simulation.
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%
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sim1D = Stack([inlt, flow, surf]);
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% set the initial profiles.
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setProfile(sim1D, 2, {'u', 'V', 'T'}, [0.0 1.0 % z/zmax
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0.06 0.0 % u
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0.0 0.0 % V
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tinlet tsurf]); % T
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names = speciesNames(gas);
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for k = 1:nSpecies(gas)
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y = massFraction(inlt, k);
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setProfile(sim1D, 2, names{k}, [0 1; y y]);
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end
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sim1D
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%setTimeStep(fl, 1.0e-5, [1, 3, 6, 12]);
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%setMaxJacAge(fl, 4, 5);
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%%%%%%%%%%%%% solution %%%%%%%%%%%%%%%%%%%%
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% start with the energy equation on
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enableEnergy(flow);
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% disable the surface coverage equations, and turn off all gas and
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% surface chemistry
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setCoverageEqs(surf, 'off');
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setMultiplier(surf_phase, 0.0);
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setMultiplier(gas, 0.0);
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% solve the problem, refining the grid if needed
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solve(sim1D, 1, refine_grid);
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% now turn on the surface coverage equations, and turn the
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% chemistry on slowly
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setCoverageEqs(surf, 'on');
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for iter=1:6
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mult = 10.0^(iter - 6);
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setMultiplier(surf_phase, mult);
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setMultiplier(gas, mult);
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solve(sim1D, 1, refine_grid);
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end
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% At this point, we should have the solution for the hydrogen/air
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% problem. Now switch the inlet to the methane/air composition.
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set(inlt,'X',comp2);
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% set more stringent grid refinement criteria
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setRefineCriteria(sim1D, 2, 100.0, 0.15, 0.2);
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% solve the problem for the final time
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solve(sim1D, 1, refine_grid);
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% show the solution
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sim1D
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% save the solution
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saveSoln(sim1D,'catcomb.xml','energy',['solution with energy' ...
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' equation']);
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%%%%%%%%%% show statistics %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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writeStats(sim1D);
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elapsed = cputime - t0;
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e = sprintf('Elapsed CPU time: %10.4g',elapsed);
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disp(e);
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%%%%%%%%%% make plots %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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figure(1);
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subplot(3,3,1);
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plotSolution(sim1D, 'flow', 'T');
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title('Temperature [K]');
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subplot(3,3,2);
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plotSolution(sim1D, 'flow', 'u');
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title('Axial Velocity [m/s]');
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subplot(3,3,3);
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plotSolution(sim1D, 'flow', 'V');
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title('Radial Velocity / Radius [1/s]');
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subplot(3,3,4);
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plotSolution(sim1D, 'flow', 'CH4');
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title('CH4 Mass Fraction');
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subplot(3,3,5);
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plotSolution(sim1D, 'flow', 'O2');
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title('O2 Mass Fraction');
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subplot(3,3,6);
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plotSolution(sim1D, 'flow', 'CO');
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title('CO Mass Fraction');
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subplot(3,3,7);
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plotSolution(sim1D, 'flow', 'CO2');
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title('CO2 Mass Fraction');
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subplot(3,3,8);
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plotSolution(sim1D, 'flow', 'H2O');
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title('H2O Mass Fraction');
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subplot(3,3,9);
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plotSolution(sim1D, 'flow', 'H2');
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title('H2 Mass Fraction');
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