Dome Temperature Research Articles

Study on High Temperature Air Combustion of Hot Blast Stove

NOx is the major technical barrier to increase hot blast temperature and prolong campaign life of hot blast stove (HBS) at present. In order to restrain the amount of NOx formation during combustion process in the HBS, the paper studies and analyses the generation mechanism of NOx production, and calculates NOx generation rate and amount in HBS by means of thermodynamic generation model. A new dome combustion stove is developed based on high temperature air combustion (HTAC) technology. A comparison on the combustion process and characteristic of conventional HBS and HTAC HBS is performed by application of CFD numerical simulation model. Temperature and concentration field distribution, flame shape and NOx concentration distribution of two kinds of stove are calculated. The result shows quite symmetrical HTAC stove temperature field distribution. Under the same dome temperature, NOx generation is 80ppm only, reduced by approximate 76% in comparison with conventional stove. HTAC HBS can obtain higher temperature, energy-saving, emission-reducing, and decrease NOx emission efficiently, as well as realize long campaign life of HBS.

Influence of Operation Parameters on Dome Temperature of COREX Melter Gasifier

Statistical analysis and theoretical calculation have been carried out to study the parameters affecting dome temperature of COREX melter gasifier by using actual plant data. The relationship between parameters and dome temperature has been realized qualitatively and quantitatively. It is found that the dome temperature is influenced significantly by metallization, fuel rate, coal rate, coke rate, and oxygen volume. High volatile matter and low moisture coal are beneficial to maintaining dome temperature. Regression analysis was carried out and equations have been developed to predict and regulate dome temperature.

Study and Design on High Temperature Air Combustion of Hot Blast Stove

During Hot Blast Stove (HBS) combustion, NOxforms rapidly when the flame temperature above 1420°C. In order to restrain the amount of NOxformation during combustion of HBS, the formation mechanism of NOxis investigated, and the NOxformation rate and amount in HBS are calculated by means of thermodynamic model. A new type of dome combustion HBS is developed based on high temperature air combustion (HTAC) technology. A comparison on the combustion process and characteristic of conventional HBS and HTAC HBS is performed by application of Computational Fluid Dynamics (CFD) simulation model. Temperature and concentration distribution, flame shape and NOxconcentration distribution of two kinds of stove are calculated. The result shows quite symmetrical HTAC stove temperature distribution. Under the same dome temperature, NOxamount is 80ppm only, reduced by approximate 76% in comparison with conventional stove.

红外共形整流罩热噪声分析与修正

When the optical dome of aerobat is initially subjected to aerodynamic flight conditions, the temperature of front surface rises rapidly. The thermal optical dome produces a sharp increase in background radiance on the focal plane detector, which can mask the target signal and decrease the ability of target tracking. Infrared conformal dome has demonstrated its capabilities as a prominent technique for supersonic aero thermal radiation effect. Aero thermal radiation effect of conformal infrared dome is described. The thermal noises of conformal dome are measured by infrared blackbody when dome temperature decreases from 460 K to 320 K. Quadratic surface as noise correction model decided by dualistic nolinear regression analysis is introduced, and the coefficient of determination of quadratic surface fitting is 0.8683. The mean signal noise ratio of the image is increased to 13.7 dB after noise correction by noise correction model. The signal noise ratio of infrared image increases 6.5 dB after noise correction. The result can meet the precision requirement of target tracking system and provide partial evidence for optics system optimization.

Thermochemical Wear of Refractory Linings Associated With Gas Firing in Metallurgical Plants

The present paper deals with the corrosive interaction between the atmosphere and the refractory lining as well as in one case the steel shell for two industrial facilities. In one of the following cases a magnesia carbon lining is partly decarburized by the atmosphere during preheating of a steel ladle. In the other case, the flue gas from blast furnace gas heating of a hot blast stove causes a nitric attack on the cold side of the refractory lining at the steel shell. Investigation of these mechanisms rely on computational fluid dynamics (CFD) simulations which quantify the flow and temperature field as well as the species transport during heat release from the gas combustion in both plants. Furthermore, the heat exchange between hot gas and refractory is estimated and thereby associated chemical reactions with/within the refractory material. In both CFD case studies a non‐premixed approach was applied to model the combustion process and to characterize the flue gas composition. The follow‐up reactions with refractory lining and the steel casing are discussed specifically for each case. The calculated oxygen content in flue gas during ladle preheating is estimated to 15%vol. The maximum heat transfer between hot gas and refractory takes place in the bottom region of the ladle due to convection. The radiative heat exchange plays the most important role in the zone of magnesia‐carbon lining. Within the investigation of carbon burnout kinetics limiting factors like diffusion and mass transfer coefficient of oxygen were defined and (partially) determined. The NO formation during the blast stove heating period strongly depends on the dome temperature which is an important blast process control value. Calculated NO emission loads showed promising agreement with real plant data and literature trends.

Numerical Simulation on Temperature Field of Long Narrow Confined Space Fire under Negative Pressure Ventilation Condition

In this paper, the geometric model, combustion model and the initial and boundary conditions were determined by the actual long narrow confined space. The variation of the temperature field at different time were studied, the temperature distribution law of long narrow confined space were simulated by detection points, which including the dome temperature variation at different time, and the temperature distribution law in the horizontal and vertical direction, the law of temperature distribution in the three directions were studied when the simulation was 120s. The study provided reference for evacuation and rescuing of long narrow confined space fire under the negative pressure ventilation condition.

Accounting for the Solar Radiation Influence on Downward Longwave Irradiance Measurements by Pyrgeometers

Abstract Measurements of broadband downward longwave (LW) irradiance are carried out at Lampedusa, Italy, in the Mediterranean, jointly with solar irradiance, since 2004 using shaded and unshaded Eppley Precision Infrared Radiometers (PIRs) and Kipp & Zonen CGR4 pyrgeometers. The calibrations of the different pyrgeometers are traceable to the Physikalisch-Meteorologisches Observatorium Davos World Radiation Center (PMOD/WRC). Nighttime measurements from intercalibrated pyrgeometers agree within ±2 W m−2. The performance of the pyrgeometers when operated unshaded has been analyzed by comparison with shaded instruments. For the PIR, the nonhomogeneous dome temperature in cloud-free conditions produces differences in LW irradiance within ±4 W m−2, depending on the time of the day and the season. The effect of the LW fraction of solar radiation reaching the sensor and a possible shortwave leakage of the dome interference filter produces differences between shaded and unshaded pyrgeometers during daytime. In cloud-free conditions, the unshaded PIR overestimates the LW irradiance measured by a shaded PIR by up to 10 W m−2, and by up to 12 W m−2 compared to a shaded CGR4. Conversely, the unshaded CGR4 LW irradiances agree with those of a shaded PIR within the measurements’ uncertainties. An empirical formula to correct the solar effect of the PIR has been derived. Applying this correction, the average LW irradiance overestimate for cloud-free conditions decreases from 3.8 ± 1.8 to 0.0 ± 1.3 W m−2 in spring, and from 3.2 ± 1.7 to 0.0 ± 1.3 W m−2 in summer. Thus, LW irradiance from an unshaded PIR can be derived within about ±2 W m−2 of a shaded PIR.

A novel nonintrusive method to resolve the thermal dome effect of pyranometers: Instrumentation and observational basis

A new method for improving the ground‐based pyranometer measurements of solar irradiance has been employed during the East Asian Study of Tropospheric Aerosols and Impact on Regional Climate field experiment, Asian Monsoon Year in China in 2008. Depending on the temperature difference between its detector and domes, a pyranometer's thermal dome effect (TDE) can vary from a few W m−2 at night to over tens of W m−2 during daytime. Yet in traditional calibration procedures only a single calibration constant is determined, and consequently TDE is misrepresented. None of the methods that have been documented in the literature can capture TDE nonintrusively using the same instrument. For example, although adding a temperature sensor to the detector assembly is straightforward, attaching any sensor on a dome is intrusive and will affect its overall optical and physical properties. Furthermore, in response to the solar elevation and atmospheric variables, the dome temperature distribution is both dynamic and uneven, which makes it exceedingly difficult for locating a representative point on the dome for measuring TDE. However, the effective‐dome‐temperature is proportional to the pressure of the air trapped between the outer and the inner domes; therefore with a minor modification to a pyranometer, we can utilize the ideal gas law to gauge TDE without affecting the domes. Pyranometers can become climate‐quality instruments once their TDE are nonintrusively determined.

An Application of Neural Network Technique to Correct the Dome Temperature Effects on Pyrgeometer Measurements

Abstract This work describes an application of a multilayer perceptron neural network technique to correct dome emission effects on longwave atmospheric radiation measurements carried out using an Eppley Precision Infrared Radiometer (PIR) pyrgeometer. It is shown that approximately 7-month-long measurements of dome and case temperatures and meteorological variables available in regular surface stations (global solar radiation, air temperature, and air relative humidity) are enough to train the neural network algorithm and correct the observed longwave radiation for dome temperature effects in surface stations with climates similar to that of the city of São Paulo, Brazil. The network was trained using data from 15 October 2003 to 7 January 2004 and verified using data, not present during the network-training period, from 8 January to 30 April 2004. The longwave radiation values generated by the neural network technique were very similar to the values obtained by Fairall et al., assumed here as the reference approach to correct dome emission effects in PIR pyrgeometers. Compared to the empirical approach the neural network technique is less limited to sensor type and time of day (allows nighttime corrections).

A Field Intercomparison Technique to Improve the Relative Accuracy of Longwave Radiation Measurements and an Evaluation of CASES-99 Pyrgeometer Data Quality

Abstract Techniques for improving the relative accuracy of longwave radiation measurements by a set of pyrgeometers [the Eppley Laboratory Precision Infrared Radiometer (Model PIR)] are presented using 10 PIRs from the 1999 Cooperative Atmosphere–Surface Exchange Study (CASES-99). The least squares–based optimization technique uses a field intercomparison (i.e., a time period during which all the PIRs were upward looking and set up side by side) to determine a set of optimization coefficients for each PIR. For the 10 CASES-99 PIRs, the optimization technique improved the standard deviation of the difference of downwelling irradiance between the PIRs from ±0.75 to ±0.4 W m−2 (for nighttime data). In addition to presenting the optimization method, various PIR data quality checks are outlined and applied to the PIR data. Based on these quality checks, the measured case and dome temperatures of the CASES-99 PIRs were all reasonable. Using the 10 CASES-99 PIRs, simple estimates of the average nighttime net rad...

Cation Composition Control of MOCVD ( Ba , Sr ) TiO3 Thin Films along the Capacitor Hole

The variations in the cation concentration ratio of metallorganic chemically vapor deposited (MOCVD) (BSTO) and (STO) thin films along a capacitor hole with a diameter of 0.15 μm were investigated. Even under deposition conditions that would produce cation-stoichiometric films on a nonpatterned wafer, the and Sr/Ti ratios varied remarkably along the depth direction of the hole when the usual shower-head-type chemical vapor deposition chambers were used. The Sr/Ti ratios increased or decreased depending on the wafer temperature, the flow rate, and the types of precursors. When a new dome-type chamber was adopted and the dome temperature was 450°C, completely conformal composition and thickness step coverages were obtained at a wafer temperature of 420°C on the 0.15 μm capacitor hole pattern. The variation in the composition and thickness step coverages were interpreted in terms of the variation in the sticking coefficients of the precursors according to the various deposition conditions and types of precursors and chambers. © 2002 The Electrochemical Society. All rights reserved.

Testing of propane/isobutane mixture in domestic refrigerators

The performance of a propane/isobutane (R290/R600a) mixture was examined for domestic refrigerators. A thermodynamic cycle analysis indicated that the propane/isobutane mixture in the composition range of 0.2 to 0.6 mass fraction of propane yields an increase in the coefficient of performance (COP) of up to 2.3% as compared to CFC12. For the actual tests, two commercial refrigerators of 299 and 465 l were used. For both units, all refrigeration components remained the same throughout the tests, except that the length of the capillary tube and amount of charge were changed for the mixture. Each refrigerator was fully instrumented with more than 20 thermocouples, two pressure transducers, and a digital watt/watt-h meter. For each unit, both ‘energy consumption test’ and ‘no load pull-down test’ were conducted under the same condition. The experimental results obtained with the same compressor indicated that the propane/isobutane mixture at 0.6 mass fraction of propane has a 3–4% higher energy efficiency and a somewhat faster cooling rate than CFC12. The mixture showed a shorter compressor on-time and lower compressor dome temperatures than CFC12. In conclusion, the proposed hydrocarbon mixture seems to be an appropriate long term candidate to replace CFC12/HFC134a from the viewpoint of energy conservation requiring minimal changes in the existing refrigerators.

An Integrated Surface Radiation Measurement System

Abstract An integrated surface radiation measurement system has been developed to measure the surface radiation exchange flux. The system employs upward- and downward-looking Eppley pyrgeometers and pyranometers to separately measure four components: downwelling and upwelling, as well as short- and longwave atmospheric radiation. Additional thermisters, installed by Eppley Laboratories, give a more accurate measurement of dome temperature, and the analog battery-powered thermopile temperature compensation circuit is replaced with a voltage-standard circuit. This circuit also serves to produce accurate thermisters excitation. All the parameters of the pyrgeometers, including the output of the thermopile, the temperature of the upper surface of thermopile, and the dome and the case temperatures, are monitored directly. This allows corrections to be made for the thermal emission of the thermopile and a realistic Stefan–Boltzmann calculation to correct for the solar heating of the pyrgeometer dome. The signal...

Determination of Longwave Heat Flux at the Air-Sea Interface Using Measurements from Buoy Platforms

Abstract A theory for pyrgeometer operation is utilized for determining downwelling longwave radiation. Errors in downwelling longwave radiation measurements are due to differences in pyrgeometer body and dome temperatures compared to that of the atmosphere. Additionally, incident shortwave radiation fluxes may be important. Using the present theory along with laboratory and field observations, it appears that downwelling longwave heat fluxes can be measured with errors less than 6 W m−2. Longwave heat flux observations from surface buoys deployed in four different oceanic regions suggest that 1) incoming longwave measurements from buoys are repeatable, 2) uncertainties in radiometer calibration are significant and systematic, and 3) pyrgeometers are affected by direct and indirect solar heating. A hybrid measurement method for the determination of net longwave heat flux at the air-sea interface is described. The authors recommend improvement in calibration procedures as well as development of a radiomete...

Deformation and hydraulic resistance of a regenerative heat exchanger poured checkerwork

A method of calculation of the creep deformation and hydraulic resistance of a poured checkerwork making it possible to take into consideration the basic features of cyclic operation of a regenerative heat exchanger has been developed and used on an IBM type computer. The method is designed for use in determination of the quality characteristics of a poured checkerwork [11] and calculation of the increase in hydraulic resistance of a poured checkerwork of a regenerative heat exchanger as the result of the simultaneous action of more than one factor [2]. The influence of a number of operational and design factors on the operation of an actual hot-blast stove with a poured checkerwork at Kosogorsk Metallurgical Plant was analyzed. It was established that in the increase in hydraulic resistance in the stoves of Kosogorsk Metallurgical Plant in service for a year with a dome temperature of 1500°C the share caused by deformation of the checkerwork is about 1/5 of the combined influence of all reasons for the increase in resistance. With a further increase in dome temperature to 1550 and 1600°C the influence of deformation of the spheres on checkerwork resistance will be the most significant reason for the increase in resistance of all of the remaining ones. As the result an increase in total checkerwork resistance during a year of service at 1550°C of another 30–40 % in comparison with that observed in operation with a dome temperature of 1500°C may be expected. Operation at tdome=1600°C accelerates the increase in resistance by 1.5–2 times in comparison with operation with tdome= 1500°C. Taking into consideration the last determinations the undesirability of service of the hot-blast stove block with a poured checkerwork at Kosogorsk Metallurgical Plant with tdome=1600°C and the doubtfulness of long service of the stoves at tdome=1550°C must be concluded.

Pointing, Tracking, Guiding, and Dome Seeing at the AAT

AbstractThe Anglo-Australian Telescope (AAT), though based on the design for the Kitt Peak and Cerro Tololo 4 metre telescopes, differs in many significant respects. E.g. its declination axis is offset from the polar axis and its polar axis structure is much stiffer. Also the computer was, from the outset, more closely integrated with the telescope drive and control than was previous practice. The sound structural design, good gearing, and accurate mirror supports, together with thorough computer calibration, allowed the AAT to set new standards in pointing by the time it was fully operational in 1975. Good pointing saves time in acquisition, greatly aids day time observing, and leads to good blind tracking. Currently, calibrations covering the whole observable sky give rms radial residuals very near 2 arc sec. Blind tracking errors are generally within ± 1 arc sec for 1 hour or more and natural frequency oscillations less than 0.1 arc sec peak to peak. Better tracking is, of course, available using the offset autoguiders, which employ image dissectors and function on stars to about 15m. Intensified SEC Videcon television cameras are used for acquisition and for guiding with light reflected from spectrograph slit jaws.Initially, the AAT seeing suffered from poor matching of inside and outside air temperatures because the intended active cooling of dome air was cut from the installation to save funds, leaving an inadequate capacity for forced ventilation. Correlation of observed seeing with dome temperature excess indicated degradation of about 1/2 arc sec/°C. In 1980 the forced ventilation was upgraded to change the dome air in less than 4 minutes, with optional flow direction, upwards (exhausting out the observing aperture) or downwards. Measurements of seeing within the dome, but with the dome open, now show degradations typically 0.4 and 0.6 arc sec diameter with upwards and downwards ventilation respectively. Stellar seeing measurements, including routine observations in which the ventilation direction was alternated nightly, have also indicated superiority of the upwards flow. Taking advantage of this, filters can now be installed on the air supply to keep the optics cleaner.

Performance of fused silica as a filter in a wide field-of-view earth radiation budget radiometer

An analysis of the thermal response of a fused silica hemispherical dome filter in a wide field-of-view (WFOV) shortwave radiometer for obtaining earth radiation budget measurements is presented. The impact of the filter thermal response on the dc detector (a thermopile) and on the resulting measurement uncertainty is evaluated. It is shown that the hemispherical filter material maintains neither a uniform nor constant temperature distribution as it responds to changes in the radiation emitted from earth. Accurate determination of terrestrial shortwave irradiance requires knowledge of the dome filter thermal response because the thermopile responds to changes in the dome temperature as well as the shortwave scene. Data are presented that show that variations in the dome temperature distribution from calibration conditions can result in a measurement uncertainty of several W/m(2) if not properly accounted for in the interpretation f the measurement. Design approaches, ground calibration, and data reduction techniques that can reduce this measurement uncertainty by an order of magnitude are presented.

Pyrgeometer measurements from aircraft

An Eppley Laboratory pyrgeometer was tested in several different modes of operation to determine its ability to measure infrared irradiance from an aircraft platform. During the initial tests, the instrument output varied by 30–40 W m−2 as the incident solar irradiance or air flow over the KRS-5 dome changed. The long pass filter (the KRS-5 dome) was found to be opaque to radiation of wavelengths shorter than 3.6 μ. Hence, the fluctuations described above may be attributed to changes in the temperature of the filter. The pyrgeometer output was studied as a function of the incident infrared irradiance and the temperature difference between the sensor surface and the KRS-5 dome. Laboratory tests verified this dependence and showed that by utilizing the thermopile cold junction and dome temperatures, infrared irradiances may be measured with a precision of ± 1.7 W m−2. Although not the original intent of this research, it is shown that the KRS-5 shielded pyranometer may be used to measure infrared irradiance with a precision of ± 2 W m−2 in a ground station installation. However, in order to realize the precision value mentioned above, two precautions must be taken. First, the temperature of the KRS-5 dome must be monitored; and second, the entire instrument should have sufficient air flow over it to minimize temperature differences between the KRS-5 dome and the thermopile cold junction. The pyrgeometer was also mounted in an upward-looking configuration on an aircraft platform and measurements were made at constant pressure levels under clear sky conditions to approximate a constant irradiance. It was found that the intense flow over the instrument minimized the effect of the solar heating of the dome. Infrared irradiances measured on a day/night flight comparison differed by an average difference of 3.5 W m−2. rms deviations about the mean value at any level were less than ± 2.5 W m−2. Observed downward irradiance divergences differed from values calculated using a radiative transfer model by less than 0.3 W m−2 mb−1. The ventilation, however, did not eliminate the sink-dome temperature differences because the temperature response of the thermopile heat sink is an order of magnitude slower than that of the KRS-5 dome; therefore, horizontal fluctuations of air temperature or abrupt changes of altitude result in erroneous output values. An attempt was made to determine an empirical correction for air temperature fluctuations from the aircraft air temperature data. No general correction factor relating temperature and output changes could be determined. However, individual applications of such an empirical relationship did reduce rms deviations of the output to less than 2 W m−2.

Alkali Attack on Blast Furnace Stove Refractories

Investigations were made on premature failure of refractories of Blast Furnace Stove. It was found that holes of the checkers were clogged due to dust accumulation. Brick surface became glazed and top few courses of t bricks were completely vitrified and deformed.Samples were collected from different zones of the stove and laboratory investigations were made. The chemical analysis and the fusion point of dust and glazed portion of brick, indicated that high dust content of blast furnace gas and prolonged dome temperature of 1250°C and the chocking of the holes were the factors that caused failure of refractories of the stove. It is suggested that for longer life of refractories the gas should be cleaner. If the temperature of the stove is required to be raised in order to increase the temperature of hot blast, the top few feet of checkers, combustion chamber walls and dome should be relined with high alumina refractories.

Aberrations and Field Errors of the SprouI 24-inch Objective.

view Abstract Citations (8) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Aberrations and Field Errors of the SprouI 24-inch Objective. Ianna, Philip A. Abstract On-axis and off-axis Hartmann tests, using 103a-G plates and a Wratten minus blue (No. 12) filter, have been made to investigate the aberrations of the Sproul 24-inch obj ective as a function of the cooling of the lens and the position of the telescope. The tests show considerable variation in the lens during the course of a night. Longitudinal spherical aberration is positive and may be as large as seven times the Rayleigh criterion (0.7-mm difference in focus between the marginal and paraxial rays) at the beginning of the night. It normally decreases to within the Rayleigh criterion in about six hours, and even becomes negative in the morning hours if the dome temperature remains constant. Primary coma and astigmatism also vary with the state of temperature adjustment of the objective. The astigmatic difference remains less than 2 mm. Coma varies from slightly negative to positive values producing a comatic flare of the order of 0.5 mm in the corners of the field. Both off-axis aberrations ten4 to be large when the spherical aberration is large. Plates taken through a coarse-wire obj ective grating show a magnitude-coma scale effect of -0.00008 *~0.00001 (p.e.) per magnitude at full aperture, and -0.000015 t0.00001 at 12-inch aperture. Direct plates show that a reduction of aperture to 12 in. is accompanied by a decrease of scale of 0.0005. There is some evidence of slight flexure effects. Publication: The Astronomical Journal Pub Date: June 1962 DOI: 10.1086/108711 Bibcode: 1962AJ.....67..273I full text sources ADS |