A bifurcation analysis of high-temperature ignition of H{sub 2}-O{sub 2} diffusion flames
- Univ. of California, San Diego, La Jolla, CA (United States). Center for Energy and Combustion Research
- Univ. Politecnica de Madrid (Spain)
The form of the ignition branch for steady, counterflow, hydrogen-oxygen diffusion flames, with dilution permitted in both streams, is investigated for two-step reduced chemistry by methods of bifurcation theory. Attention is restricted to fuel-stream temperatures less than or equal to the oxidizer-stream temperature T{sub {infinity}} and to T{sub {infinity}} larger than or of the order of the crossover temperature {Tc} at which the rates of production and consumption of H atoms are equal. Two types of solutions are identified, a frozen solution that always exists in this kinetic approximation because all rates are proportional to the concentration of the intermediate H atom, and an ignited solution, represented by a branch of the curve giving the maximum H concentration in terms of a Damkoehler number constructed from the strain rate and the rate of the branching step H + O{sub 2} = OH + O. For T{sub {infinity}} > {Tc}, the latter bifurcates from the frozen solution if the Damkoehler number is increased to a critical value. For T{sub {infinity}} larger than a value T{sub s} > {Tc}, the effects of chemical heat release are small, and ignition is always gradual in the sense that the limiting ignited-branch slope is positive (supercritical bifurcation) and there is no S curves. For T{sub {infinity}} in the range {Tc} < T{sub {infinity}} < T{sub s}, the heat release associated with the radical-consumption step causes the limiting ignition-branch slope to become negative (subcritical bifurcation), producing abrupt ignition which leads to an S curve. For values of T{sub {infinity}} below crossover, the ignited branch appears as a C-shaped curve unconnected to the frozen solution. The method of analysis introduced here offers a first step toward analytical description of nonpremixed H{sub 2}-O{sub 2} autoignition.
- OSTI ID:
- 93304
- Report Number(s):
- CONF-940711-; TRN: IM9537%%348
- Resource Relation:
- Conference: 25. international symposium on combustion, Irvine, CA (United States), 31 Jul - 5 Aug 1994; Other Information: PBD: 1994; Related Information: Is Part Of Twenty-fifth symposium (international) on combustion; PB: 1838 p.
- Country of Publication:
- United States
- Language:
- English
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