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Experimental And Numerical Investigations Of The Premixed Gases Combustion In Porous Media

Posted on:2009-02-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:H JiangFull Text:PDF
GTID:1102360242495806Subject:Engineering Thermal Physics
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Combustion of premixed gases in porous media is a novel combustion technology. Heat exchanged between solid matrix and gases, resulting in superadiabatic combustion temperature, which greatly improved combustion stability, significantly broaden the flammabilities, and effectively controlled pollution emissions. Studying of combustion mechanism and flame characteristics in porous media can be contributed to the design and development of porous media burners. In this paper, the combustion characteristics in porous media were studied by both experimental measurements and numerical simulation.The experimental facility was designed and set up to research propane/air premixed combustion in an inert packed bed. The effects of different operation conditions on flame structures and combustion stabilities were experimented. The un-stabilized combustion wave propagation was simply investigated and analyzed. The numerical simulation of the combustion in porous media used one-dimension steady laminar reacting model with the interphase convective heat change and dispersion effects, the detailed mechanism and two-flux radiative transfer equation. The experimental and simulation results showed that combustion in porous media can achieve superadiabatic combustion temperature, improve flame speed and reduce pollution emissions.Combustion in two-layer porous media burner was studied experimentally and numerically. The flame structure, the flame propagation and stability, the emissions and the radiative output efficiency burner were analyzed. The results have shown that two-layer porous media burner has broader lean flammabilities. The radiative output efficiency can be influenced by controlling the flame position, and lean-fuel low-velocity combustion can effectively improve the radiative output efficiency.Rich combustion of methane/air in two-layer porous media burner was simulated using one-dimension model. It was concluded that, rich combustion in porous media can also achieve superadiabatic temperature. H2 product is quite rich after combustion, so rich combustion can be used to hydrogen production. H2 conversion efficiency is strongly dependent on the equivalence ratio, when suitable equivalence ratio is the key to improve conversion efficiency. CFD software FLUENT 6.2 was used to simulation propane/air premixed combustion in packed bed with user-defined scalars and user-defined functions. Two-dimensional stabilized model and simple reaction mechanism were adopted. It is concluded that, because of the wall viscosity and wall heat loss, the flame structure, velocity and density et al in porous medium presents a 2D structure obviously, so it is significant to consider the effects of wall in actual porous medium burner designing.Porous media burner with heat regenerator and heat exchanger was designed and set up. The effects of heat regenerator on combustion temperature, lean limit and pollution emission were experimentally studied. The results have shown that, heat recycle can effectively improve combustion temperature, broad lean limit. A lean limit of propane/air combustion with the equivalence ratio of 0.31 was achieved when flow speed was 42cm/s. And the burner thermal efficiency achieved 42% at the equivalence ratio of 0.67.Mini-burner with porous media was studied. Porous media combustion was organized in a 2 cm diameter and 2 cm long cylindrical cavity, which has broadly ignition and combustion ranges. Parameters were measured such as temperatures and pressures. A stable micro-thrust was achieved when the burner was combined with a mini-nozzle.
Keywords/Search Tags:porous media, superadiabatic temperature, porous burner, lean flammability, pollution emission, radiative output efficiency, micro-scale combustion, combustion propulsion system
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