摘要:

A technique was developed for direct measurements ofgastemperatures in the range of 2050K-2700K with improved accuracy and reproducibility. The technique utilized the low-emittance of certain pure, metal-oxide fibers whose diameters varied from 60 – 400μm in the experiments. The uncertainty of the technique was limited by the uncertainty in the melting points of the materials, i.e. ±15K. The abrupt increase in the emittance of the fibers upon melting was utilized as indication of reaching a known gas temperature. The accuracy of the technique was confirmed by both the fiber-diameter independence of the results and by the calculated low emittance values of transparent fibers, of order 0.01 al a few degrees below their melting point. This melting-point temperature was approached by increments smaller than 4K, accomplished by controlled increases of reactant flow rates in H2/air or H2/O2flames. As applications, the technique was used (a) for assessing the uncertainty in thermocouple measurements for inferring gas temperatures, and (b) for calibrating an IR camera to measure gas temperatures, thereby demonstrating its capability as an excellent calibration reference.

ISSN:0010-2202    

DOI:10.1080/00102200008947247

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The spectroscopic analysis of the high molecular weight species condensed (CS) and sampled in the soot formation zone of a rich premixed ethylene flame was carried out in the uv-visible and infrared wavelength region.

ISSN:0010-2202    

DOI:10.1080/00102200008947248

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The Mild Combustion is a relatively novel combustion technique characicrized by both an elevated temperature of reactants and an adiabatic flame temperature not higher than 1600K. These features are the results of several technological demands coming form different application fields.

ISSN:0010-2202    

DOI:10.1080/00102200008947249

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The quantitative characterization of sooting flames in terms of soot load and total soot surface area continues to be a major challenge in both fundamental investigations and practical applications. More particularly, a major interest can be found to discriminate the two classes of particulate, namely soot and cenosphere, presents in power generation plants fuelled with heavy fuel oils.

ISSN:0010-2202    

DOI:10.1080/00102200008947250

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The effect of heal treatment on the evolution of reactivity of a highly porous pure synthetic char was studied with the aid of Raman scattering measurements. Two sets of experiments were carried out. A) Samples were oxidized in air at 600°C without heat treatment and Raman spectra were measured as a function of conversion. B) Samples were heat-treated in the range 900-1400 °C, in nitrogen, then characterized by micro-Raman spectroscopy, in the range 800-1800 cm−1, and then oxidized by air at 500 °C and by CO2at 900 °C in a thermogravimetric balance. In all Raman scattering measurements the G and D bands were dominant and a weak “1180 cm−1” band was apparent. The following conclusions can be drawn from results of experiments A and B respectively: A) Throughout reaction with oxygen the most significant changes in reactivity and Raman features occur in the conversion range 0- 30%. This is consistent with previous measurements of thermal resistivity and intrinsic reaction rate. B) Heal treatment up to 900 °C at time duration up to 300 minutes did not show any effect on reactivity. Decrease in reactivity was apparent at and beyond 1200 °C. The characteristics of each of the three Raman bands showed clear correlation with reactivity changes both in air and CO2. These were attributed to morphological (dimensions and ordering) changes in the rearrangement of the carbon network structure, as previously suggested. Interpretation of these changes and their effect on reactivity is proposed.

ISSN:0010-2202    

DOI:10.1080/00102200008947251

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The sound-assisted fluidized bed combustion of powders of tyre derived fuel (TDF) and of a biomass (Robinia Pseudoacacia) has been studied to assess the benefits deriving from the application of an acoustic field on the performance of the combustor. Experiments consisted of steady combustion, either ordinary or sound-assisted, of TDF and Robinia fine particles. High intensity acoustic fields of 120Hz reduce carbon elutriation rates by a factor of about 1.5, increasing the fixed carbon conversion efficiency by 5-8% and 2-3% for TDF and Robinia respectively. Sound frequencies either lower or higher than 120Hz reduce the effectiveness of sound, approaching the performances of ordinary fluidized bed combustors.

ISSN:0010-2202    

DOI:10.1080/00102200008947252

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

An improved version of a combustion-desulfurization model for fluidized bed combustors burning high ash and sulfur content low quality lignite in its own ash with the addition of limestone is presented. The desulfurization model considers sulfur retention by both limestone and ash and is based on first order catalyst deactivation where the kinetics of desulfurization is described by two rate constants; one for the initial surface reaction, the other for the rate of pore plugging or deactivation. The accuracy of the complete model with experimentally determined deactivation rate constants was tested by applying it to a 0.3 MWt AFBC test rig and comparing its predictions with measurements. Comparisons show that (he model produces reasonably accurate predictions of sulfur retention provided that the rate constants are determined experimentally under the fluidized bed combustor operating conditions.

ISSN:0010-2202    

DOI:10.1080/00102200008947253

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Based on the analysis of measured data on flow rates, concentrations and temperatures taken during steady state operation of a lignite-fired 0.3 MW, Atmospheric Fluidized Bed Combustor (AFBC) test rig, radiative exchange in freeboard of the combustor was modeled by using a well-stirred enclosure model in conjunction with Radiosity-Irradiation Method (RIM). Radiative properties of the particle laden combustion gases were calculated by assuming grey radiation behaviour for both particles and gas, and using Leckner's correlations for gas and Mie theory for particles. The accuracy of the model was tested by comparing its predictions with incident radiative heat fluxes measured on the freeboard wall. Comparisons between the incident radiative heat fluxes predicted by the present model and those measured show that this engineering approach can be used with confidence by designers for the particle loadings typically encountered in freeboards of bubbling fluidized bed combustors.

ISSN:0010-2202    

DOI:10.1080/00102200008947254

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A model for predicting radiative heal transfer in coal-fired furnaces is presented. The radiative transfer equation is modelled by the discrete ordinates method for body-fitted coordinates using the S4-approximation. The gas absorption coefficient is determined by a weighled-sum-of-grey-gases model, the radiative properties of coal and ash particles are derived from the specific area and a mean efficiency factor of the particle cloud. The scattering phase function is modelled by the Delta-Edding-ton approximation. The entire radiation model is adopted for vector and parallel computers guaranteeing numerical efficiency. It is tested at an idealized squared combustion chamber with black walls filled by an emitting, absorbing medium with constant absorption coefficient. The computations are carried out on several curvilinear non-orthogonal grids using different boundary conditions. On all grids the computed radiative source terms and wall heat fluxes are in very good agreement with the analytic solution. Furthermore, the model is validated at a coal-fired lest facility. Apart from the near burner region the computed temperature distribution only slightly deviates from the measured values.

ISSN:0010-2202    

DOI:10.1080/00102200008947255

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Three lots of ash from a small bubbling fluidized bed combustor, each made up of three fractions and two lots of ash from a large industrial scale circulating fluidized bed installation were examined. Limestone sorbents were used in both cases. Ash samples were subjected to phase analysis “as received” and after prehydration at ambient conditions and under pressure. Determinations of the proportion of free CaO were also made for selected samples, including some to which a controlled amount of CaO or silica had been added before hydration. When possible, the thermal effect associated with mixing the samples with an excess of water was measured. It was concluded that during the prehydration process CaO can be liberated from Ca-containing coal ash components but it can also be consumed in reactions with silica or silicates. These processes can affect the exothermicity.

ISSN:0010-2202    

DOI:10.1080/00102200008947256

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor