An experimental and numerical investigation of homogeneous ignition in catalytically stabilized combustion of hydrogen/air mixtures over platinum
Section snippets
Nomenclature
- b
Channel half-height, Fig. 1
- cp
Specific heat at constant pressure
- Ck
Concentration of gas-phase species
- Dkl
Multicomponent diffusion coefficient, Eq. 7
- DkT
Species thermal diffusion coefficient, Eq. 7
- Dkm
Mixture-average species diffusion coefficient, Eq. 8
- Dk
Effective species diffusion coefficient, Eq. 12
- E
Activation energy
- h
Total enthalpy, Eq. 4
- hko
Chemical enthalpy of gas-phase species, Eq. 9
- Jk
Heterogeneous molar flux of gas-phase species
- k
Reaction rate coefficient
- Kc
Reaction equilibrium constant
- Kg
Total
Burner geometry and flow conditions
A catalytic burner especially suited for H2/air CST has been built, using design concepts based on our earlier, smaller-size CH4/air reactor [12]. The combustor (see Fig. 1) consisted of two horizontal Si[SiC] ceramic plates, 300 mm long (L), 110-mm wide and 10-mm thick. Four rectangular (4 × 4 × 7 mm3) ceramic spacers were positioned at the plate corners to maintain a constant plate separation of 7 mm (2b). Both Si[SiC] plates were bevelled at their edges to accommodate two quartz windows
Governing equations and boundary conditions
The governing equations for a steady, laminar reactive flow with homogeneous and heterogeneous chemical reactions are, in their elliptic 2-D Cartesian form, as follows:
Continuity equation:
Momentum equations:
Energy equation:
Gas phase species equations:
Experimental results
The measured surface temperature distributions are depicted in Fig. 4. The profiles of Fig. 4 extend up to 250 mm (the range of interest for the present computations) and have been constructed by curve-fitting through the individual thermocouple measurements; the particular type of curve-fit did not influence the predicted homogeneous ignition characteristics. The suppression of the high entry temperatures (compare with Fig. 2) was evident: all profiles peaked at distances x ≥ 100 mm. In
Conclusions
The catalytically stabilized combustion of lean H2/air mixtures was investigated numerically and experimentally at atmospheric pressure in laminar channel-flow configurations. Measured homogeneous ignition distances (xig) were compared against numerical predictions using a 2-D elliptic fluid mechanical model with multicomponent transport and elementary hetero/homogeneous reaction schemes; four different homogeneous and three heterogeneous schemes were tested. The following are the key
Acknowledgements
Support for this work was provided by the Swiss Federal Office of Energy (BFE) under contract No. 59048 and Alstom Power Technology of Switzerland.
References (48)
- et al.
Catalysis Today
(1999) - et al.
Catalysis Today
(2000) - et al.
Catalysis Today
(1994) - et al.
Proc. Combustion Institute
(1996) - et al.
J. Catalysis
(1991) - et al.
Surface Science
(1997) - et al.
Proc. Combustion Institute
(2000) - et al.
Combust. Flame
(1999) - et al.
Proc. Combustion Institute
(1998) - et al.
Combust. Flame
(1999)
Proc. Combustion Institute
Proc. Combustion Institute
Prog. Energy Combust. Sci
Combust. Flame
Combust. Flame
Catalysis Today
Catalysis Today
Chemical Engineering J
Catalysis Today
Combust. Flame
Proc. Combustion Institute
Surface Sci
AIChE
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