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The Effect of Varying Magnetic Field Gradient on Combustion Dynamic
Abstract
The focus of the recent experimental research is to provide control of
the combustion dynamics and complex measurements (flame temperature,
heat production rate, and composition of polluting emissions) for
pelletized wood biomass using a non-uniform magnetic field that produces
magnetic force interacting with magnetic moment of paramagnetic oxygen.
The experimental results have shown that a gradient magnetic field
provides enhanced mixing of the flame compounds by increasing combustion
efficiency and enhancing the burnout of volatiles.
... There are many reasons for that: wood fuel has different moisture content and heating value, combustion efficiency is not as high if comparing with natural gas (Arena et al. 2010;Demirbas 2004;Vassilev et al. 2010). reference to this paper should be made as follows: Suzdalenko, V.;Gedrovics, M. 2014. Environmental effect of cofiring and magnetic field on wood pellets combustion, Journal of Environmental Engineering and Landscape Management 22 (02) The aim of recent research is to study wood pellets combustion improvement possibilities by using different regulation possibilities: ...
... The results of previous investigations (Zake et al. 2010;Suzdalenko et al. 2011) confirm that effects of interaction between flame and inhomogeneous magnetic field can be used in order to achieve additional impact on the combustion process. The effect is based on transfer of paramagnetic oxygen towards the gradient caused by the magnetic field gradient. ...
The aim of the recent research is to provide stable, controllable and effective wood pellets combustion with minimum emissions. Two possibilities were chosen, investigated and analysed: wood pellets co-firing with propane-butane mixture and the use of a permanent magnet. The special pilot device was constructed in the laboratory of Heat and Mass Transfer in Institute of Physics. Two types of experiments were conducted: combustion with propane-butane supply (0.9 kW up to 1.27 kW) of wood pellets with different moisture content (W = 8%, 15%, 20% and 25%); combustion of wood pellets with applied magnetic field by using the permanent magnet, an propane-butane supply also was used. The main conclusion of the research is that co-firing and magnetic field can be used as an instrument to provide more effective burnout of volatiles and cleaner heat production.
First published online: 19 Mar 2014
When burning fossil fuels and renewable energy resources, greenhouse
emissions (GHG) are emitted into the atmosphere. One of the options to
reduce GHG emissions is to apply a magnetic field. The effect of a
gradient magnetic field on the gasification of renewable fuel and the
combustion of volatiles by applying the field to the bottom part of the
swirl flame with recirculation is studied for the conditions of
field-enhanced reverse heat and mass transfer of paramagnetic flame
species up to the layer of wood pellets. The aim of research to
investigate the magnetic field effect on swirling flame dynamics for the
conditions of self-sustaining wood fuel combustion and by cofiring with
propane flow.
Three commercially available biomass fuels, made of natural and waste wood, were fed in a pilot scale bubbling fluidized bed gasifier having an internal diameter of 0.381 m and a maximum feeding capacity of 100 kg/h. The experimental runs were carried out at about 850°C and under values of the equivalence ratio between 0.20 and 0.30. The fluidized bed was generally made of natural olivine even though some runs utilized beds of dolomite or quartz sand. Measurements taken during each run include the gas composition, the content of tar in the syngas, the mass flow rate and composition of entrained fines collected at the cyclone and the characterization of bed material. The results indicate that the air gasification process is technically feasible with all the biomass tested. The olivine as tar removal bed catalyst provides for different results with waste and natural biomass fuels.
Magnetic field effect on combustion dynamics of the swirling flame flow is studied experimentally with the aim to obtain a cleaner and more effective combustion of a renewable fuel (wood pellets), providing a joint research of magnetic field effects on the swirling flame velocity field formation, processes of heat/mass transfer and combustion of volatiles at different stages of wood fuel burnout. The magnetic field effect on the swirling flame flow formation and combustion of volatiles is also studied experimentally using a pilotscale experimental device consisting of a wood fuel gasifier, water-cooled sections of the combustor with diagnostic sections between them for measuring the swirling flame velocity, temperature and composition field formation as well as the field effect on the heat production rate. The results show that the magnetic field effect on combustion dynamics must be related to the field-induced mass transfer of paramagnetic flame species (oxygen, nitrogen oxide) in the field direction, depending on magnetic force acting on the swirling flow field. Because of the magnetic field-induced magnetic force action, local variations of the flame velocity, temperature and composition fields are detected and discussed. The results show that the magnetic field effect on the swirling flame flow can be used as a tool to ensure a more effective burnout of volatiles and a cleaner heat energy production.
Since biomass is the only carbon-based renewable fuel, its application becomes more and more important for climate protection. Among the thermochemical conversion technologies (i.e., combustion, gasification, and pyrolysis), combustion is the only proven technology for heat and power production. Biomass combustion systems are available in the size range from a few kW up to more than 100 MW. The efficiency for heat production is considerably high and heat from biomass is economically feasible. Commercial power production is based on steam cycles. The specific cost and efficiency of steam plants is interesting at large scale applications. Hence co-combustion of biomass with coal is promising, as it combines high efficiency with reasonable transport distances for the biomass. However, biomass combustion is related to significant pollutant formation and hence needs to be improved. To develop measures for emission reduction, the specific fuel properties need to be considered. It is shown that pollutant formation occurs due to two reasons: (1) Incomplete combustion can lead to high emissions of unburnt pollutants such as CO, soot, and PAH. Although improvements to reduce these emissions have been achieved by optimized furnace design including modeling, there is still a relevant potential of further optimization. (2) Pollutants such as NOX and particles are formed as a result of fuel constituents such as N, K, Cl, Ca, Na, Mg, P, and S. Hence biomass furnaces exhibit relatively high emissions of NOX and submicron particles. Air staging and fuel staging have been developed as primary measures for NOX reduction that offer a potential of 50% to 80% reduction. Primary measures for particle reduction are not yet safely known. However, a new approach with extensively reduced primary air is presented that may lead to new furnace designs with reduced particle emissions. Furthermore, assisting efforts for optimized plant operation are needed to guarantee low emissions and high efficiency under real-world conditions.
An experimental investigation on the behavior of a lifted diffusion flame with a central methane jet and a surrounding air co-flow is presented. Different regimes of flame stability are described from an anchored flame to a stable lifted flame which is destabilized before extinction. In a second part, the influence of a magnetic field on the diffusion flame is studied. The experimental results show that the lift-off height of the flame is decreased in presence of the magnetic gradient. These effects are attributed to the magnetic force which develops on air via its action on the paramagnetic oxygen.
The behavior of gas flow in air has been demonstrated visually under gradient magnetic fields in the range 0–40 T/m under 0–1.5 T. The magnetic behavior depended on the concentration of oxygen. Pure oxygen or nitrogen mixed oxygen (≳30%) was observed to be attracted by a magnetic field and act like a magnetic fluid where the magnetic effect on the gas was comparable to that of normal diffusion. In contrast, nitrogen gas escaped from magnetic fields of high intensities, and no magnetic field effect was observed for the flow of air. These phenomena were explained by the difference between the force acting on the gas and that acting on the air surrounding it under gradient magnetic fields. The magnetic force increased with increasing concentration of oxygen. This explanation can be also applicable to the escape of flames from magnetic fields of relatively high intensity or the magnetic quenching of flames inside a pair of columnar poles.
The effect of magnetic field on OH radical distribution in a hydrogen-oxygen diffusion flame was experimentally and numerically investigated to explore the possibility of combustion control by magnetic force. In experiments, a coaxial type of burner was set between the magnet pieces. Two-dimensional (2D) cross-section distributions of OH* chemiluminescence intensity and OH fluorescence intensity were obtained with spectroscopic techniques using a CCD camera and a Planar Laser-Induced Fluorescence (PLIF) system, respectively. It was clearly seen that the high-density regions of OH* and OH radicals axisymmetrically migrated toward the central axis of the flame due to the influence of the magnetic field. In numerical simulations, such a phenomenon was qualitatively reproduced by solving the equations of reactive gas dynamics and magnetism. As a result, it was found that the magnetic force does not directly and selectively induce the diffusion velocity (the relative velocity) of OH itself. Alternatively, the magnetic force acting on O2, whose mass density and magnetic susceptibility are much larger than those of other chemical species, causes the change in the mean velocity (the mass-average velocity) of mixture gas to transport the OH radical distribution indirectly and passively.
Magnetic fields impact combustion processes in a manner analogous to that of buoyancy, i.e., as a body force. It is well known that in a terrestrial environment buoyancy is one of the principal transport mechanisms associated with diffusion flame behavior. Unfortunately, in a terrestrial environment it is difficult if not impossible to isolate flame behavior due magnetic fields from the behavior associated with buoyancy. A micro-, or reduced, gravity environment is ideally suited for studying the impact of magnetic fields on diffusion flames due to the decreased impact of buoyancy on flame behavior.
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