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- Bäckström, Daniel, 1985, et al.
(författare)
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Gas temperature and radiative heat transfer in oxy-fuel flames
- 2012
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Ingår i: The 37th International Technical Conference on Clean Coal & Fuel Systems, Clearwater USA, 3-7/6-2012. - 9780932066374
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work presents measurements of the gas temperature, including fluctuations, and its influence on the radiative heat transfer in oxy-fuel flames. The measurements were carried out in the Chalmers 100 kW oxy-fuel test unit. The in-furnace gas temperature was measured by a suction pyrometer and by an optical system based on FTIR-spectroscopy. The radiation intensity was measured by a Narrow Angle Radiometer and the gas radiation was calculated with a Statistical Narrow Band model. The overall agreement between the two temperature measurement techniques was good. The optical system showed a lower temperature than the suction pyrometer in the low velocity regions of the furnace, a difference which is likely to be an effect of the purge gas added in the optical probe. The measured temperature fluctuations were evaluated by modeling of the gas radiation. The influence from the measured fluctuations on the radiative heat transfer shows no effect of turbulence-radiation interaction. However, by comparing with temperature fluctuations in other flames it can be seen that the fluctuations measured here are relatively small. Further research is needed to clarify to which extent the applied methods can account for the turbulence-radiation interaction in the investigated flame.
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- Johansson, Robert, 1977, et al.
(författare)
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Influence of ash particles on radiative heat transfer in air- and oxy-fired conditions
- 2012
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Ingår i: 37th Clean Coal Conference, Clearwater Florida.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work focuses on thermal radiation in oxy-fired conditions. Both gas and particle radiation is modeled in an axi-symmetric cross section of a cylindrical furnace and the influence of ash and its properties is investigated. Coal and ash particles are treated separately and their properties are calculated according to the Mie-theory. For the gas radiation, a Statistical-Narrow-Band (SNB) model is applied. The intensity field is calculated according to the discrete transfer method and scattering is assumed to be isotropic. Calculations are done on spectral basis, solving one intensity equation for each narrow band, to account for the spectral nature of the gases and the ash particles. The investigated cases cover both air-and oxy-fired conditions and the properties of the combustion gas are based on measured data from a lignite flame in Chalmers 100 kW rig. Temperatures and particle profiles are chosen to represent different sections of a boiler and gas concentrations corresponding to both dry and wet flue gas recycling are examined.
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- Johansson, Robert, 1977, et al.
(författare)
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THE INFLUENCE OF PARTICLE AND GASEOUS RADIATION IN OXY-FUEL COMBUSTION
- 2011
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Ingår i: The 36th International Technical Conference on Clean Coal & Fuel Systems, Clearwater USA, 5-9/6 2011.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work focuses on radiation in oxy-fired conditions. Both gas and particle radiation is modeled in an axi-symmetric cross section of a cylinder and differences between air- and oxy-firing are investigated. The particle radiation is modeled by empirical correlations accounting for spectral properties of coal particles and scattering of the particles is assumed to be isotropic. For the gas radiation, a Statistical-Narrow-Band (SNB) model is applied as reference. Included in the analysis is also a non-gray or banded formulation of the Weighted-Sum-of-Gray-Gases (WSGG) model and grey approximations. The investigated cases cover both air-and oxy-fired conditions and the properties of the combustion gas are based on measured data from a lignite flame in Chalmers 100 kW rig. Wall fluxes and the radiative source term along the cylinder diameter are compared to evaluate differences in the radiative heat transfer between air- and oxy-fuel combustion. Special emphasis is put on the load and distribution of particles, with both in-flame conditions as well as furnace exit conditions being examined. The different approximations for gaseous radiation are evaluated to quantify the errors they result in when they are applied in conditions with a high particle load.
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