The heat transfer between a porous ceramic radiant burner (PCRB) and a target environment was studied. The black aluminum pot (BAP) and white aluminum pot (WAP) with an emissivity of 0.72 and 0.22 ...were experimentally used to obtain the temperature distribution and thermal efficiency of a burner. Under the same heat load, the porous ceramic plate (PCP) of WAP is 79~90 °C higher than BAP, but the measured thermal efficiency of BAP is 15~20% higher than WAP. A heat transfer model for PCRB and pots was established based on the radiant and convection heat transfer theories. This model is applicable to common infrared radiant burners. The heat gain type of the pot was analyzed quantitively, with a relative error of less than 7%. The influence of the pot surface emissivity on the burner and heat transfer change of the pot was discussed, and the solid radiation heat gain of BAP is approximately double that of BAP under the same heat load. For PCRBs whose main heat is from radiation, the pot with a high surface emissivity can achieve better radiation utilization to improve thermal efficiency.
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The anti-corrosion inhibition effect of itraconazole on copper (Cu) in 0.5 M H₂SO₄ is observed with variety of experimental methods, including electrochemical measurement, surface morphology ...analysis, and theoretical calculations. These experimental results all confirm that itraconazole exhibits excellent anti-corrosion performance in the certain temperatures range (298 K⁻313 K) for copper in sulfuric acid solution. In addition, corresponding adsorption isothermal models were used to fit the adsorption behavior of itraconazole on the copper surface. The results show that the Langmuir adsorption model agrees best with the experimental results. The adsorption of itraconazole on the copper surface belongs to chemical and physical adsorption.
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Porous media combustion has significant advantages of high thermal efficiency and low pollution emissions. However, the flow state in the porous media will affect the reaction rate. In order to ...increase the rate of chemical reactions, the fluid flow resistance in the porous media must be reduced. The pressure drop test of SiC foam ceramics was carried out. By changing the pore density of the experimental materials, the pressure drop characteristics of SiC foam ceramic are tested and analyzed. Based on the classical Ergun equation, a semi-empirical formula for calculating the pressure drop gradient of SiC foam ceramics with the airflow velocity is proposed. The two constants in the formula are calculated by measurement, and the applicability of the formula is verified. This formula can quickly analyze the pressure drop characteristics of SiC foam ceramic materials. The accurate measurement of pressure drop is helpful to determine the rated pressure of the head of foam ceramic burner and reduce the investment of front-end fans in industrial burners.
This paper makes a comparative study on the normal diffusion flame (NDF) and inverse diffusion flame (IDF) characteristics of dimethyl ether (DME) in microgravitational spherical diffusion flame ...geometry by simulations with detailed fuel chemistry and a transport model. It is found that there always existed two combustion modes (i.e., hot flame and cool flame) in either NDF or IDF condition. The combustion progress of hot flames was controlled by diffusive mixing, while that of cool flames was controlled by low-temperature competing kinetics. The cool-flame structure dynamics were far away from the chemical equilibrium. The low-temperature branching rate of DME was positively dependent on the oxygen level, while its termination rate was enhanced with the increasing temperature. Being rather distinct from the NDF counterpart, DME IDFs had the oxygen-enriched combustion feature in either hot- or cool-flame condition. Furthermore, DME hot-flame extinction was induced by thermal radiative loss, while the cool-flame extinction was induced especially by the decrease of the low-temperature branching rate. Compared with hot NDFs, it would be of less effectiveness to control the hot IDF combustion process by positive measures. However, combustion in the latter configuration was much more stable than the former. In either NDF or IDF geometry, the cool-flame chemistry could help to extend the fuel flammability range considerably, and the two-reaction-zone structure of cool flame was responsible for cool-flame stability. In addition, the IDFs had much better ignition performance than the NDF counterpart.
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Biogas production efficiency fluctuates with climate variations and agricultural arrangements, which pose a limiting factor upon its single supply to end users via a regional exclusive network, ...especially in peak demand. In this paper, an appropriate methodology to address the contradiction between biogas supply and demand is proposed. Methane conditioned by the addition of air is described, and can be a supplementary energy injected into a biogas distribution network. To accomplish the mixing process and also inject the exhaust mixture into the distribution system, a mixer–ejector was introduced and integrated into the biogas grid. Finally, the fundamental combustion behaviors of mixed gases were estimated through the analysis of flame appearance, contamination emissions, and the flame stability region. The results showed that the methane/air mixture with a mixing ratio ranging from 49/51 to 53/47 could interchange biogas commendably, and good combustion behavior was obtained on a typical biogas-burning appliance.
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The flame front area is an important parameter to quantify the heat release rate. However, the limitations imposed by the measuring instruments and the measurement methodologies make it difficult to ...determine the flame front position in an image. This work introduces a method to detect and optimize the flame front boundary. A high‐speed camera was employed to continuously capture the flame images. By setting appropriate intensity thresholds, the impact noise can be eliminated from the image and the flame front boundary can be determined. The binary diagram of the image was morphologically processed to obtain the normalized area fluctuations of the flame front in a temporally resolved manner. Two flame types and combustion regimes were studied. A LABVIEW‐based program was used for the synchronous triggering of the camera, the photomultiplier, and the microphones. The normalized area and photomultiplier output signals of a multiple flame burner obtained within the same period were compared and combined with the spectrum information from the microphone in the cavity. The trend charts were investigated in terms of the Pearson correlation coefficient. The results showed a strong correlation, thereby verifying the feasibility of this method.
This work introduces a method to detect and optimize the flame front boundary. A high‐speed camera was employed to continuously capture the flame images. By setting appropriate intensity thresholds, the impact noise can be eliminated from the image and the flame front boundary can be determined.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•Electrochemical test data indicate PFD can exhibit distinguished anti-corrosion ability for Cu in H2SO4.•XPS provided strong evidence for the existence of inhibition film on the Cu ...surface via CuN bond.•Theoretical calculations show that PFD has small energy gap value and large dipole moment value.
Papain freeze dried (PFD) was used as a novel, eco-friendly and efficient inhibitor for copper corrosion in H2SO4 medium via experimental and theoretical calculation methods. These test methods include classical weight loss experiment, electrochemical measurements, surface morphology researches, and theoretical calculations. The data of weight loss experiment proves that with the increase of temperature, PFD still exhibits excellent anti-corrosion performance. The corrosion inhibition efficiency of PFD can still be maintained at about 95% at 313 K. The results of electrochemical experiments indicate that PFD is the mixed-type inhibitor that can simultaneously restrain the reaction of anode and cathode. Both the impedance experiment results and polarization experiment data show that the corrosion inhibition efficiency of PFD exceeds 95%. The atomic force microscope (AFM) and scanning electron microscope (SEM) test results intuitively show the excellent inhibition performance of PFD. The X-ray photoelectron spectroscopy (XPS) experimental data demonstrated the formation of NCu bond, indicating that PFD can effectively separate the corrosive medium by chemical adsorption on the copper surface. Molecular dynamics simulations (MDS) manifest that PFD can adsorption on the Cu (1 1 1) surface via the parallel pattern. Besides, the adsorption process of PFD on copper surface obey the Langmuir mono-layer adsorption.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Flame extinction is one of the most essential critical flame features in combustion because of its relevance to combustion safety, efficiency, and pollutant emissions. In this paper, detailed ...simulations were conducted to investigate the effect of H2 addition on dimethyl ether spherical diffusion flame in microgravitational condition, in terms of flame structure, flammability, and extinction mechanism. The mole fraction of H2 in the fuel mixture was varied from 0 to 15% by 5% in increment. The chemical explosive mode analysis (CEMA) method was employed to reveal the controlling physicochemical processes in extinction. The results show that the cool flame in microgravitational diffusive geometry had the “double-reaction-zone” structure which consisted of rich and lean reaction segments, while the hot flame featured the “single-reaction-zone” structure. We found that the existence of “double-reaction-zone” was responsible for the stable self-sustained cool flame because the lean zone merged with the rich zone when the cool flame was close to extinction. Additionally, the effect of H2 addition on the cool flame was distinctively different from that of the hot flame. Both hot- and cool-flame flammability limits were significantly extended because of H2 addition but for different reasons. Besides, for each H2 addition case, the chemical explosive mode eigenvalues with the complex number appeared in the near-extinction zone, which implies the oscillation nature of flame in this zone which may induce extinction before the steady-state extinction turning point on the S-curve. Furthermore, as revealed by CEMA analysis, contributions of the most dominated species for extinction changed significantly with varying H2 additions, while contributions of the key reactions for extinction at varying H2 additions were basically identical.
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Natural gas pipelines play a key role in the transmission and distribution of natural gas, and reliable optimization of the pipeline network can lead to safe and guaranteed gas transmission to ...individuals with minimum risk loss and effective cost. Therefore, we developed an improved layout optimization procedure and applied a new prediction method, the fuzzy comprehensive evaluation method, which is based on entropy weight and backpropagation (BP) neural network (NN). We used it to comprehensively calculate risk loss cost to achieve improved layout during the planning stage and used it to determine the initial risk loss cost. We verified the procedure using a genetic algorithm (GA) for two different layouts, one of which is the improved optimum layout and the other the conventional optimal layout. Finally, the optimized results of four different layouts were determined and the total cost of the new layout is 9.79% and 8.49% less than that of the two conventional layouts. This shows that the new prediction method of risk loss cost provides an efficient and effective means of synchronizing risk loss cost and total cost during the layout planning stage for natural gas transmission network.
•An improved layout optimization procedure is developed during the planning stage.•The fuzzy comprehensive evaluation method for risk loss cost is firstly introduced.•The risk loss cost is predicted by utilizing BPnetwork algorithm.•An efficient verification method is proposed by employing GA.
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Natural gas pipelines play a key role in the transmission and distribution of natural gas, and reliable optimization of the pipeline network can lead to safe and guaranteed gas transmission to ...individuals with minimum risk loss and effective cost. Therefore, we developed an improved layout optimization procedure and applied a new prediction method, the fuzzy comprehensive evaluation method, which is based on entropy weight and backpropagation (BP) neural network (NN). We used it to comprehensively calculate risk loss cost to achieve improved layout during the planning stage and used it to determine the initial risk loss cost. We verified the procedure using a genetic algorithm (GA) for two different layouts, one of which is the improved optimum layout and the other the conventional optimal layout. Finally, the optimized results of four different layouts were determined and the total cost of the new layout is 9.79% and 8.49% less than that of the two conventional layouts. This shows that the new prediction method of risk loss cost provides an efficient and effective means of synchronizing risk loss cost and total cost during the layout planning stage for natural gas transmission network.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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