Docu-mentaThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.http://utils.ciemat.es:802019-11-18T10:30:40Z2019-11-18T10:30:40ZAnalysis of an idealized counter-current microchannel-based reactor to produce hydrogen-rich syngas from methanolFernández-Galisteo, DanielFernández-Tarrazo, EduardoJiménez, CarmenKurdyumov, Vadim N.http://documenta.ciemat.es/handle/123456789/5992019-11-14T10:34:21Z2019-08-08T00:00:00ZTitle: Analysis of an idealized counter-current microchannel-based reactor to produce hydrogen-rich syngas from methanol
Authors: Fernández-Galisteo, Daniel; Fernández-Tarrazo, Eduardo; Jiménez, Carmen; Kurdyumov, Vadim N.
Abstract: In an effort to investigate the suitability of the concept of portable hydrogen production, we examine numerically the combustion of a very rich methanol-air mixture in a micro-gap assembly consisting of multiple counter-current channels of finite length separated by thin solid conducting walls. Within the mathematical framework of the narrow-channel approximation, the problem can be formulated as a one-dimensional model for a single channel with an extra term representing heat transfer from the hot stream products to the fresh reactants in adjacent channels. We show that the heat recirculation enables superadiabatic temperatures inside the reactor and promotes the oxidation of methanol far beyond the conventional rich limit of flammability. The result is a feasible thermal partial oxidation that produces hydrogen without the need for a catalyst. The paper presents an analysis of the model burner performance with detailed gas-phase kinetics in stationary regimes in terms of operating variables such as the equivalence ratio and the gas inflow velocity, and in terms of physical parameters such as the length of the reformer and the conductivity of the wall material. The idealized microreactor predicts maximum hydrogen yield of the order of 60% at equivalence ratios between 3 and 6.2019-08-08T00:00:00ZA one-step reduced mechanism for near-limit hydrogen combustion with general stoichiometryFernández-Galisteo, DanielWeiss, AdamSánchez, Antonio L.Williams, Forman A.http://documenta.ciemat.es/handle/123456789/5982019-11-14T10:28:49Z2019-07-10T00:00:00ZTitle: A one-step reduced mechanism for near-limit hydrogen combustion with general stoichiometry
Authors: Fernández-Galisteo, Daniel; Weiss, Adam; Sánchez, Antonio L.; Williams, Forman A.
Abstract: A one-step reduced mechanism for hydrogen combustion, previously developed for fuel-lean flames, is extended to apply for all equivalence ratios under near-limit conditions by taking into consideration two additional recombination steps that are important under fuel-rich conditions. It is found that the crossover temperature that appears in the cutoff factor is smaller under fuel-rich conditions. Besides improving insights, the results can be beneficial in speeding computations.2019-07-10T00:00:00ZImpact of the gravity field on stability of premixed flames propagating between two closely spaced parallel platesFernández-Galisteo, DanielKurdyumov, Vadim N.http://documenta.ciemat.es/handle/123456789/5972019-11-14T10:24:21Z2018-06-29T00:00:00ZTitle: Impact of the gravity field on stability of premixed flames propagating between two closely spaced parallel plates
Authors: Fernández-Galisteo, Daniel; Kurdyumov, Vadim N.
Abstract: The stability of a planar flame front propagating between two parallel adiabatic plates inclined at an arbitrary angle is investigated in the frame of narrow-channel approximation. It is demonstrated that buoyancy forces can suppress the hydrodynamic (Darrieus–Landau) and cellular (diffusive-thermal) instabilities for sufficiently large value of the gravity parameter for the case of downward-propagating flames. The stability analysis reveals that in the case of oscillatory diffusive-thermal instability, the flame front cannot be stabilized in the similar way. Finally, the stability results are compared satisfactorily with unsteady numerical simulations.2018-06-29T00:00:00ZAnalysis of premixed flame propagation between two closely-spaced parallel platesFernández-Galisteo, DanielVadim N., KurdyumovPaul D., Ronneyhttp://documenta.ciemat.es/handle/123456789/5962019-11-14T10:17:12Z2017-12-22T00:00:00ZTitle: Analysis of premixed flame propagation between two closely-spaced parallel plates
Authors: Fernández-Galisteo, Daniel; Vadim N., Kurdyumov; Paul D., Ronney
Abstract: Motivated by experimental observations on premixed-gas flame propagation in Hele-Shaw cells, this work analyzes quasi-isobaric flame propagation between two adiabatic parallel plates using a simple quasi-2D formulation based on averaging the flow properties across the cell gap. Instabilities associated with thermal expansion, buoyancy, viscosity change across the front and differential diffusion of thermal energy and reactants are investigated with one-step chemistry, constant heat capacity and variable transport coefficients through time-dependent computations of the flame front evolution in large domains. These instabilities are found to induce flame wrinkling which increases flame surface area and thus propagation speeds in ways different from those associated with freely propagating flames. The simulations are compared with experiments in Hele-Shaw cells; very good qualitative and (in some cases) quantitative agreement is found.2017-12-22T00:00:00Z