The experimental study was carried out on the emission characteristics of nitrogen oxide in a 0.3MW circulating fluidized bed as well as analysis of the formation and destruction mechanism of nitrogen oxide. Several v...
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The experimental study was carried out on the emission characteristics of nitrogen oxide in a 0.3MW circulating fluidized bed as well as analysis of the formation and destruction mechanism of nitrogen oxide. Several variables associated with the combustion system were investigated in the experiment, which include bed temperature, excess air, primary-to-secondary air ratio, and coal species. It is found that the NOx emissions decrease along the height of the furnace, while the N2O emissions increase continuously. More NOx emissions and less N2O emissions are generated as the bed temperature increases. It is also illustrated that an increase of air stoichiometry leads to a significant NOx increase and an obvious N2O increase. And air staging is proved to be an effective way to control the nitrogen oxide emissions in the fluid bed. Besides, it is also shown in the experiment that the concentration of NOx and N2O is higher during the combustion of anthracite than that during the combustion of bituminous.
The lattice Boltzmann method (LBM), a mesoscopic method between the molecular dynamics method and the conventional numerical methods, has been developed into a very efficient numerical alternative in the past two deca...
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The lattice Boltzmann method (LBM), a mesoscopic method between the molecular dynamics method and the conventional numerical methods, has been developed into a very efficient numerical alternative in the past two decades. Unlike conventional numerical methods, the kinetic theory based LBM simulates fluid flows by tracking the evolution of the particle distribution function, and then accumulates the distribution to obtain macroscopic averaged properties. In this article we review some work on LBM applications in engineering thermophysics: (1) brief introduction to the development of the LBM; (2) fundamental theory of LBM including the Boltzmann equation, Maxwell distribution function, Boltzmann-BGK equation, and the lattice Boltzmann-BGK equation; (3) lattice Boltzmann models for compressible flows and non-equilibrium gas flows, bounce back-specular-reflection boundary scheme for microscale gaseous flows, the mass modified outlet boundary scheme for fully developed flows, and an implicit-explicit finite-difference-based LBM; and (4) applications of the LBM to oscillating flow, compressible flow, porous media flow, non-equilibrium flow, and gas resonant oscillating flow.
The experimental study was carried out on the air-staged combustion of different coal in a 1 MW W-shaped furnace. The combustion process occurred in two zones: the pre-stage combustion zone and the primary combustion ...
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The experimental study was carried out on the air-staged combustion of different coal in a 1 MW W-shaped furnace. The combustion process occurred in two zones: the pre-stage combustion zone and the primary combustion zone. A variable SR was introduced to represent the air stoichiometric ratio in the pre-stage combustion zone. It is found that as SR decreases in the test range, the flame penetration depth is lengthened, and the temperature at the exit of the furnace decreases. Meanwhile, the maximum temperature in the central of the furnace first increases and then decreases, whereas the combustible loss and nitrogen oxides (NOx) emissions first decrease and then increase. The value of SR corresponding to the optimal combustion performance is 0.67 for lean coal and 0.65 for anthracite. Besides, it is also indicated that the effects of air-staging method are more significant on the lean coal than that on the anthracite.
Gasification of peanut shell, sawdust and straw in supercritical or subcritical water has been studied in a batch reactor with the presence of a series of Raney-Ni and its mixture with ZnCl2 or Ca(OH)2. The main gas p...
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Gasification of peanut shell, sawdust and straw in supercritical or subcritical water has been studied in a batch reactor with the presence of a series of Raney-Ni and its mixture with ZnCl2 or Ca(OH)2. The main gas products were hydrogen, methane, carbon dioxide, and a small amount of carbon monoxide. Different types of Raney-Ni, containing different metal components such as Fe, Mo or Cr, have different influences on the gasification yield and hydrogen selectivity. The catalysis effect can be improved obviously by adding ZnCl2 or Ca(OH)2 Increasing the reaction temperature or adding ZnCl2 and Ca(OH)2 could improve the mass of H2 in gas products and reduce the mass of CH4 and CO2 at the same time. The possible mechanism is that ZnCl2 can decompose the biomass particle by accelerating cellulose hydrolyzation in high-temperature water, increasing more specific surface to admit catalysts, while Ca(OH)2 can absorb CO2 to produce CaCO3 deposit, which can drop out from the reactant system, and which will drive the reaction to get more hydrogen. With respect to the biomass conversion to gas product and selectivity of H2 at low temperature, the series of Raney-Ni has shown many advantages over other catalysts; thus, this kind of catalyst has great potential to be utilized in the hydrogen industry for the gasification of biomass.
Turbulent bubbly mixing layer was experimentally investigated by PIV and analyzed by using the swirling strength method. The velocity ratio between high speed and low speed was 4:1 and the Reynolds number based on the...
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A one-dimensional and two-dimensional combined computational model (1-D and 2-DCC model) was set up to simulate the performances of the basic type, orifice type and double inlet type pulse tube refrigerators (PTRs). T...
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A one-dimensional and two-dimensional combined computational model (1-D and 2-DCC model) was set up to simulate the performances of the basic type, orifice type and double inlet type pulse tube refrigerators (PTRs). The Darcy-Brinkman-Forchheimer model and the thermally non-equilibrium model were adopted to depict the flow and heat transfer in the regenerator which was modeled by taking the mesh as a porous medium. Parameter communicating algorithms were defined to calculate velocity and temperature at the junctions between the 1-D and 2-D computational regions. Then the simulation codes for the whole PTRs were developed. The working process and complex flow phenomena such as velocity and temperature annular effects and DC flow in PTRs were revealed. The results show that a close loop in the PTR can be formed by using a double-inlet valve which leads to the occurrence of DC flow. For the case studied, the DC flow rate accounts for 4.66% of the total mass flow rate under the present parameters and working conditions.
The scale inhibition and removal processes by electronic water treatment were investigated in this study. The results show that the treatment of scale inhibition with 7.0V can be used first for the water with the hard...
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The scale inhibition and removal processes by electronic water treatment were investigated in this study. The results show that the treatment of scale inhibition with 7.0V can be used first for the water with the hardness over 300 mgL-1(CaCO3), and then the treatment of scale removal with 5.0V can be applied when the water hardness decreases to less than 130 mgL-1(CaCO3). With the present energy-saving approach, more than 90 percent of the scale ions can be removed after treatment and no obvious scale will decompose on the surface of the heat exchanger. The SEM figures depict that the crystal morphology of scale is affected by the electronic water treatment. The crystal morphology of scale with and without the electronic water treatment is calcite and aragonite, respectively.
In present paper a three dimensional discrete vortex filament method is proposed to simulate unsteady incompressible vortical flows, through which the interaction of two coaxial vortex rings was studied. First the pro...
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In present paper a three dimensional discrete vortex filament method is proposed to simulate unsteady incompressible vortical flows, through which the interaction of two coaxial vortex rings was studied. First the process of head-on collision of two circular rings was reproduced and compared with experimental result. The good agreement between numerical work and experiment verified our model. Then the motion of single elliptic ring was studied and a fit expression was given, through which the axis-switching period of single elliptic ring can be calculate effectively. At last the head-on collision and leapfrogging process of two coaxial elliptic rings was studied respectively. For the case of head-on collision of two elliptic rings, the shape of new generated ring was similar but larger than initial elliptic ring. While for case of two elliptic rings moving in same direction, the axis-switching process of elliptic ring is accompanied with the leapfrogging process.
For efficiently cooling electronic components, the flow boiling heat transfer performance of FC-72 on micro-pin-finned silicon chips were studied. Two kinds of micro-pin-fins were used, which have the same fin thickne...
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For efficiently cooling electronic components, the flow boiling heat transfer performance of FC-72 on micro-pin-finned silicon chips were studied. Two kinds of micro-pin-fins were used, which have the same fin thickness of 30m but different fin heights of 60 and 120m, respectively. The boiling heat transfer performance was much better for the micro-pin-fined surfaces than that for a smooth surface, and increased with increasing fin height. The critical heat flux increased with fluid velocity and subcooling, and the wall temperatures at the critical heat flux for micro-pin-finned chips were less than the upper temperature limit for the normal operation of electronic components, 85C.
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