Search

Copyright of Journal of Aeronautical Materials is the property of Editorial Board of Journal of Aeronautical Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Compared with wall emission, gas thermal radiation is much more complicated because of its nongray and volumetric property. In this paper, a numerical method is established to calculate 3D radiative heat transfer in combustor by modelling radiative transfer as well as nongray radiative properties of combustion gases. Energy exchanges caused by thermal radiation and conduction are calculated and compared in a rectangular combustor, which shows the significant role of thermal radiation in heating fuel-air mixtures and prompting internal combustion reactions. Besides, radiative heat flux on the wall is also quite obvious although a non-contacting flow case, revealing the special challenges for thermal protections brought by radiant energy. Lastly, increasing the working pressure means much more participating species in radiative transfer process and the radiative effects will be also magnified. The numerical method in this paper provides a direct technique to analyze the role of thermal radiation in complex thermochemical reactions while the application case proves the necessity of coupling a high-accuracy radiation model when simulating combustion and flame propagation. [ABSTRACT FROM AUTHOR]

The study included testing the effect of different concentrations methanol and hexane extracts and mixture for both extract of Chlorococcum humicola algae against pathological fungi affecting the gramineae family, particularly wheat crops such as Fusarium graminearum, Aspergillus niger and Alternaria triticina. The study included the collection of nondiatomic dietumal algae samples from different areas within Baghdad, screening and diagnosis, and preparing pure insulation of algae most present in some samples. The study identified 186 species of 67 genera non-diatomic algae in which Chlorophyta prevailed 53%, followed by Cyanophyta 35%, Euglenophyta, Pyrrophyta 4% and the lowest percentages 2% Chrysophyta, Cryptophyta. Some sampling areas were found containing large numbers of species C. humicola so it was isolated, purified and growen in the Chu.13 medium to get a mass of 1.5g of it which extracted by two types of organic solvents using Soxhlet. The results of the study showed that the mixing extract (methanol + hexane) of C. humicola algae showed a more efficient inhibition effect than ketoconazole fungal pesticide (control agent) and other extracts on all species of fungi tested with the highest inhibition zone of 13.67 mm for F. graminearum fungus at the concentration of 32 mg / ml. While ketoconazole's fungal effect for the same fungus was less than 13.0 mm, and showed less inhibition zone than A. niger at 8 mg / ml concentration. Followed by methanol extract, which showed the highest inhibition zone of 11.0 mm for the A. triticina fungus at the concentration of 32 mg/ml, which was higher than the ketoconazole fungal pesticide effect of the same fungus, which recorded a inhibition zone of 8.0 mm. As for hexane extract, it showed less antifungal activity than fungicide and previous extracts, with the highest inhibition zone of 8.0 mm for A. niger at a concentration of 32 mg / ml, which was found to be the same inhibition zone as ketoconazole on A. triticina fungus, while the lowest inhibition zone was 4.67 mm at the concentration of 16 mg / ml on A. niger fungus. [ABSTRACT FROM AUTHOR]

This article analysed the opportunity to implement the recovery of secondary energy resources in an industrial enterprise for the production of special building materials. The inventory of secondary energy resources and the establishment of their characteristics and energy potential is an important step in the energy balance sheet. The use of secondary energy resources, and in this case of flue gas, is one of the most effective ways to increase the use of energy consumed in industrial processes of this type. In this paper, the internal recovery solution of the secondary energy resource identified in the flue gas is analysed for the regenerative preheating of the combustion air. [ABSTRACT FROM AUTHOR]

Radiative heat transfer plays an important role in the chemical reactions in the combustor. The widely used WSGG model proposed by Smith is established for normal pressure, which shows inevitable computational errors when dealing with radiative heat transfer problems at reduced or elevated pressures. In this paper, an improved global model is established to calculate the radiant energy exchanges between combustion gases and combustor chamber walls. Compared with the Smith model, the new model shows better performance in a wide range of pressure regions. The model accuracy is examined by computing the emissivity, radiative heat flux as well as the radiative source of H2O–CO2 gas mixtures at different pressure values. Finally, the radiative heat transfer inside a 3D TBCC(turbine-based combined cycle) engine exhaust system where strong gradients of pressure and temperature exist, is also addressed. The computational results show that the developed model provides approximate results at much less computational costs than the high-precision MSMGFSK-c8 model, which makes it competitive in complicated combustion systems. [ABSTRACT FROM AUTHOR]

Calcium compounds have been known to be important for enhancing aggregation and dewaterability of activated sludge. In this study, the effect of calcium compounds (CaO, Ca(OH)2, CaCl2, CaSO4 and CaCO3, respectively) on sludge dewaterability and calorific value was investigated. Upon addition of CaO, Ca(OH)2, CaCl2, CaSO4 and CaCO3 (112 mg/g dry sludge) into activated sludge, after compressed filtration the moisture content of sludge was found to be 49.7%, 55.7%, 57.1%, 65.3% and 56.5%, respectively. The addition of calcium compounds altered the structure of sludge by CaCO3 and Ca(OH) 2 production, which improved sludge filterability and provided frameworks and water passages during compression. Furthermore, sludge conditioned by CaO addition had better dewaterability than other calcium compounds. The heat generated from the CaO hydration and high pH might damage flocs' structure and improve dewaterability of sludge. Moreover, it was found that excess addition of calcium compounds led to low calorific value in combustion process. The study concluded that CaO is the optimal additive for sludge further dewatering by compressed filtration. [ABSTRACT FROM AUTHOR]

In the context of the optimization of stationary gas turbines, the surface temperatures of the turbine blades have to be measured by a non-contact technique using radiation thermometers during operation of the turbine. Nowadays turbine blades are protected by thermal barrier coatings. The infrared-optical properties of these coatings require the usage of the MIR or LWIR region for non-contact measurement of the surface temperatures. For performing such measurements and for properly analyzing the derived data, the transmission and absorption spectra of the combustion gas mixture within the turbine were determined at the local conditions during operation of the turbine. Therefore, subject of this work is the measurement of the transmission spectra of carbon dioxide and water vapor at high temperatures and high pressures to identify a wavelength range, which is almost free of absorption and emission effects. In order to perform these measurements a Fouriertransform infrared spectrometer in combination with a high temperature and high pressure gas cell was used. The obtained results showed that the wavelength region around 10 μm is nearly free of influence of the combustion gas, even at high temperatures and high pressures. The received data was compared with equivalent HITRANsimulations that matched the measurement results well. Therefore, this wavelength region is available for non-contact temperature measurement. [ABSTRACT FROM AUTHOR]

Thin films of LaO were deposited onto glass substrates by ultrasonic spray pyrolysis. Their structural and morphological properties were characterized by X-ray diffraction, Fourier transform Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photo-electron spectroscopy, Brunauer-Emmett-Teller and optical absorption techniques. The sensor displays superior CO gas sensing performance at a low operating temperature of 498 K. The signal change on exposure to 300 ppm of CO is about 75%, and the signal only drops to 91% after 30 days of operation. [ABSTRACT FROM AUTHOR]

One of the basic methods to improve both the thermal efficiency and power output of a gas turbine is to increase the firing temperature. However, gas turbine blades are easily damaged in harsh high-temperature and high-pressure environments. Therefore, ensuring that the blade temperature remains within the design limits is very important. There are unsolved problems in blade temperature measurement, relating to the emissivity of the blade surface, influences of the combustion gases, and reflections of radiant energy from the surroundings. In this study, the emissivity of blade surfaces has been measured, with errors reduced by a fitting method, influences of the combustion gases have been calculated for different operational conditions, and a reflection model has been built. An iterative computing method is proposed for calculating blade temperatures, and the experimental results show that this method has high precision. [ABSTRACT FROM AUTHOR]

A general correlation has been proposed for the first time for accurate prediction of the acidic combustion gases dew points to mitigate the corrosion potential in pollution control and energy recovery equipments. Acidic combustion gases can cause rapid corrosion when they condense on the surfaces of the heat recovery and flue gas treatment equipments. The most important acidic gases, namely, SO3, SO2, NO2, HCl, and HBr, are considered in this investigation. The presented correlation can be used for accurate prediction of the flue gas acid dew point temperatures over wide ranges of acid and water vapor concentrations in oil and gas industries. [ABSTRACT FROM AUTHOR]

C/SiC composites prepared by chemical vapor infiltration (CVI) were subjected to a stationary loading of 160 MPa in a combustion gas environment with flame temperature of 1300 °C. Lifetime of C/SiC composites in such environment was measured. Microstructures of the composites after the testing were also characterized by SEM. The experimental results indicate the lifetime of C/SiC composites is average 2.3 hours in combustion gas environments. The combustion gas flow accelerates the damage of carbon fibers and the failure of the composites by speeding up the diffusion of gas reactants and products, destroying the layer of SiO on the surface of SiC coating and bringing fused SiO inside the composites. The fracture face of C/SiC is uneven, i e, a flat area close to the windward side and a pulling-out of long fibers near the leeward side, which results from the directionality effect of the combustion gas flow. [ABSTRACT FROM AUTHOR]

The combustion characteristics of wallpaper and the toxicity of gas produced from wallpaper fires were analyzed to evaluate the fire risk of wallpaper used in living spaces. Ash content was measured with a high-temperature electric furnace, and thermal analysis was carried out with thermogravimetric analysis (TGA). Combustion time and smoke concentration were measured with a cone heater and a combustion gas analyzer. The smoke density of samples was measured using the smoke chamber ASTM E 662. Pyrolysis in silk wallpaper began at a lower temperature than the other samples. This means that silk wallpaper can be ignited at a low heat flux and will have a greater fire risk than other kinds of wallpaper. Heat by radiation flux caused silk wallpaper to ignite in the shortest time compared to the other samples, so the time for evacuation in this situation may also be reduced. Silk wallpaper also released the highest carbon monoxide concentration, so the toxicity and harmful effects to consciousness were stronger than any other wallpaper. The smoke densities of silk wallpaper and fire retardant-treated silk wallpaper were very high due to their vinyl coatings. [ABSTRACT FROM AUTHOR]

The thermal formation of dioxins is typical of recent environmental issues relating to metallurgy. To analyze the behavior of these toxic species, computer assisted thermodynamic assessments were extensively carried out. In the homogeneous gas phase equilibria of the C−O−H−Cl system, the formation of dioxins is usually observed below 300–350°C, but is observed at higher temperature under the condition of oxygen deficiency. It has become clear that the presence of enough oxygen and hydrogen, as well as a decrease in chlorine content, would be desirable to prevent dioxin formation. From a strict thermodynamic standpoint, dioxins are meta-stable products observed under the retardation of the carbon deposition reaction which must be very slow at low temperature. The effects of some inhibitors or accelerators on the formation of dioxins are also discussed. [ABSTRACT FROM AUTHOR]

The corrosion behavior of a Nb-modified TiAl intermetallic compound containing 11 at.% Nb in a simulated combustion gas with and without deposits of a NaSO−NaCl mixture was examined at 600-800°C for times up to four days. In the absence of salt deposits the corrosion rates were rather low and increased only slightly with temperature, producing very thin scales of mixed oxides of Ti, Al, and Nb without sulfides. The presence of the salt deposits produced higher weight gains during an initial stage of one to two days at 600 and 700°C, after which the reaction stopped. A more important and longlasting effect was observed instead at 800°C, when the kinetics of hot corrosion became nearly linear. The scales formed by hot corrosion were complex mixtures of various corrosion products at all temperatures and showed a porous outer region containing a mixture of unreacted salts with oxides (mainly TiO), an intermediate region of a mixture of variable composition of oxides of the three metals, and a TiO-rich layer beneath it. At 800°C the scales tended to form a thin, discontinuous AlO-rich layer in the middle and contained an additional innermost region presenting a large concentration of sulfur, very likely as Nb and Ti sulfides. The high rate of hot corrosion at 800°C is attributed to the appearance of sulfides in the inner region of the scale and to a more efficient scale fluxing. [ABSTRACT FROM AUTHOR]

The corrosion behavior of NiAl containing small additions of Ti, Zr, and B in combustion gases both with and without NaSO−NaCl deposits at 600-800°C has been studied for times up to four days. The corrosion of the saltfree NiAl leads to the formation of very thin alumina scales at 600°C but of mixed NiO−AlO scales containing also some sulfur compounds at higher temperatures, while the rate increases with temperature up to 800°C. The presence of the salt deposits considerably accelerates the corrosion rate, especially at 600 and 800°C. The duplex scales formed at 600°C are composed mostly of a mixture of NiO and unreacted salt in the outer layer and of alumina and aluminum sulfide with some nickel compounds in the inner layer. The scales grown at 700°C contain only one layer of complex composition, while those grown at 800°C are similar but have an additional outer layer containing similar amounts of nickel and aluminum. At 600 and 700°C NiSO can be detected also in the salt layer. The samples corroded at 700°C and 800°C also show an Al-depleted zone containing titanium sulfide precipitates at the surface of the alloy. The hot corrosion of NiAl involves a combination of various mechanisms, including fluxing of the oxide scale as well as mixed oxidation-sulfidation attack. At all temperatures NiAl shows poor resistance to hotcorrosion attack as a result of the formation of large amounts of Ni compounds in the scales. [ABSTRACT FROM AUTHOR]