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21.
N. E. Ermolin 《Combustion, Explosion, and Shock Waves》2007,43(5):549-561
To verify the adequacy of various models of heat release in ammonium dinitramide flame to real processes, chemical processes
in products of thermal decomposition at a pressure of 10 torr and in ammonium dinitramide [ADN; NH4N(NO2)2] flame at a pressure of 0.4 to 60 atm are numerically simulated. The calculations are performed on the basis of a detailed
kinetic mechanism and boundary conditions correlated with experimental data, thermodynamic properties, and chemical composition
of ADN. The kinetic mechanism includes submechanisms that describe high-temperature chemical processes in NH3/N2O/NO/NO2/HNO2/HNO3 and NH3/HN(NO2)2 mixtures, and the global stages of aerosol decomposition. Based on calculated and experimental data, the role of dinitraminic
acid HN(NO2)2, aerosols, and ADN vapor in heat release in the ADN flame zone adjacent to the burning surface is estimated. The calculations
predict that the main source of heat release in the cold flame zone at p ≥ 3 atm is dinitraminic acid incoming through the channel of dissociative evaporation ADNliq → NH3 + HN(NO2)2 from the burning surface. In the high-temperature flame zone, heat release is caused by the reaction that occurs in the NH3/N2O/NO/NO2/HNO2/HNO3 mixture. At moderate pressures, the high-temperature and low-temperature zones are separated by an induction zone. The stage
governing production of the OH radical, which plays an important role in combustion, in the induction zone is the reaction
HNO3 + M → OH + NO2 + M. Because of a high activation energy of the stage, small temperature perturbations in the induction zone at low pressures
lead to a finite change in the stand-off distance between the high-temperature flame zone and the burning surface. Therefore,
small temperature perturbations in the induction zone, which are caused by admixtures in the sample or by heat transfer between
the reacting gas and the ambient medium, may be responsible for disagreement between various experimental data and between
experimental and calculated data on the stand-off distance between the high-temperature flame zone and the burning surface.
In numerical calculations, the position of the high-temperature zone is effectively controlled by varying rate constants of
elementary stages within admissible limits.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 64–76, September–October, 2007. 相似文献
22.
Chemical and Isotopic Tracer Evaluation of Water Mixing and Evaporation in a Dammed Texas River During Drought 下载免费PDF全文
The interaction between drought and river regulation is monitored to better understand river flow mixing, evaporation and surface‐groundwater exchange in changing regional climates and in increasingly regulated waterways. This study compared Brazos River stable isotope (δ18O and δD) and electrical conductivity values with reservoir, creek and aquifer samples in the Brazos watershed, the largest watershed in Texas. The combination of tributaries, rainfall and the Brazos River Alluvium Aquifer, on the one hand, and the Lake Whitney reservoir, on the other hand, represent endmembers of dilute run‐off water and evaporated saline water, respectively. A simple isotope mixing model that uses monthly river discharge, Lake Whitney discharge, historical monthly precipitation δ18O and pan evaporation accurately reconstructs river δ18O (±0.5‰ on average). Data and isotope balance modelling support continued evaporation of 18O‐enriched Lake Whitney water as it flows downstream, although the most evaporation took place in Lake Whitney. The difference between river and precipitation δ18O, or Δ18ORIV‐PPT, here a measurement of degree of evaporation, ranged from ?0.1‰ for a small creek, to 1.7‰ for the Brazos River, to at least 2.7‰ in Lake Whitney. This study indicates that drought in regulated rivers may enhance reservoir discharge dominance in river flows during peak drought conditions when combined run‐off and baseflow dominance would be expected in a similar undammed river. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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24.
详细介绍了烧碱蒸发自动控制模型尤其是浓度数学模型建立的原理和具体方法,并指出了在实际运行中应注意的问题,使出料质量分数能平稳地控制在30.0%-30.5%之间。根据现有的浓碱冷却流程,制定了科学合理的浓碱冷却和冷却系统冲洗控制方案。 相似文献
25.
In this paper, Cu, Al and Ni were plated on the AB5–5 mass% LaMg3 composite hydrogen storage alloy using a vacuum evaporation plating method. The phase structure and the electrochemical properties were investigated. The X-ray diffraction (XRD) analysis shows that the phase structure is not changed obviously after the plating Cu, Al and Ni on the composites. The electrochemical tests show that maximum discharge capacity, high rate dischargeability (HRD), dischargeability at low temperature and cyclic stability was improved by vacuum evaporation plating Cu, Al and Ni. Maximum of discharge capacity of the AB5–5 mass% LaMg3 composite alloy plating Ni can reach 351 mAh/g, which is 3.5% higher than that of the untreated. HRD at Id = 1200 mA/g of the composite alloy plating Cu is 45.0% of that at 60 mA/g, which is 20.4% higher than the untreated. Discharge capacity of the composite alloy plating Cu at low temperature 233 K is 205 mAh/g, which is 57.3% of that at 298 K, and it is much higher than 36.8% of the untreated composites. The discharge capacity retention of the composite alloy plating Al after 200 cycles is 7.8% higher than the untreated. 相似文献
26.
The evaporative heat transfer of the non-boiling annular two-phase flow of air-water in a small vertical tube with uniform wall heat flux was studied both theoretically and experimentally. A simplified two-phase flow boundary layer model was used to calculate the thickness of the water film attached to the wall, and from the liquid film thickness the evaporative heat transfer coefficients of the annular two-phase flow were obtained. Theoretical equations and semi-theoretical equations were proposed for predicting the evaporative heat transfer of the annular two-phase flow of air-water in a small vertical tube. The semi-theoretical prediction agrees well with the experimental data. The mechanism of the heat transfer enhancement is the evaporation of the thin liquid film attached on the wall. 相似文献
28.
釜式再沸器壳侧循环流动与管束传热的分格模型 总被引:4,自引:0,他引:4
通过对管束壳侧循环流动沸腾传热的分析,提出了管束沸腾传热的薄层蒸发传热增强贡献的计算公式,建立了釜式再沸器壳侧循环流动与管束传热的分格模型,利用此模型,对管束传热系数及循环流速进行了模拟计算。验证结果表明,由本模型计算所得管束沸腾传热系数与实验结果吻合较好。 相似文献
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30.
根据碱回收蒸发工段的工艺特点和控制要求,设计了S7-300PLC控制系统.详细说明了控制系统的硬件组成、软件程序设计,工程实际运行表明,该系统控制效果良好,具有较好的经济价值. 相似文献