162 lines
4.9 KiB
Python
162 lines
4.9 KiB
Python
# 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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from Cantera import *
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from Cantera.OneD import *
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import math
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###############################################################
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#
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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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################ 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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gas.setState_TPX(tinlet, p, 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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surf_phase.setTemperature(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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surf_phase.advanceCoverages(1.0)
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sim = StagnationFlow(gas = gas, surfchem = surf_phase,
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grid = initial_grid)
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sim.inlet.set(mdot = mdot, T = tinlet, X = comp1)
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sim.surface.set(T = tsurf)
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sim.set(tol = tol_ss, tol_time = tol_ts)
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sim.init()
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sim.showSolution()
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# start with the energy equation on
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sim.set(energy = 'on')
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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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sim.surface.setCoverageEqs('off')
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surf_phase.setMultiplier(0.0);
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gas.setMultiplier(0.0);
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# solve the problem, refining the grid if needed
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sim.solve(loglevel, 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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sim.surface.setCoverageEqs('on')
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for iter in range(6):
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mult = math.pow(10.0,(iter - 5));
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surf_phase.setMultiplier(mult);
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gas.setMultiplier(mult);
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print 'Multiplier = ',mult
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sim.solve(loglevel, refine_grid);
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# At this point, we should have the solution for the hydrogen/air
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# problem.
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sim.showSolution()
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#Now switch the inlet to the methane/air composition.
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sim.inlet.set(X = comp2)
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# set more stringent grid refinement criteria
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sim.setRefineCriteria(100.0, 0.15, 0.2, 0.0)
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# solve the problem for the final time
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sim.solve(loglevel, refine_grid)
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# show the solution
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sim.showSolution()
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# save the solution in XML format. The 'restore' method can be used to restart
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# a simulation from a solution stored in this form.
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sim.save("catcomb.xml", "soln1")
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# save selected solution components in a CSV file for plotting in
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# Excel or MATLAB.
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z = sim.flow.grid()
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T = sim.T()
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u = sim.u()
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V = sim.V()
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f = open('catcomb.csv','w')
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writeCSV(f, ['z (m)', 'u (m/s)', 'V (1/s)', 'T (K)']
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+ list(gas.speciesNames()))
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for n in range(sim.flow.nPoints()):
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sim.setGasState(n)
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writeCSV(f, [z[n], u[n], V[n], T[n]]+list(gas.moleFractions()))
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# write the surface coverages to the CSV file
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cov = sim.coverages()
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names = surf_phase.speciesNames()
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for n in range(len(names)):
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writeCSV(f, [names[n], cov[n]])
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f.close()
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print 'solution saved to catcomb.csv'
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sim.showStats()
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