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91.
回热器是脉管制冷机的关键部件之一,其效率对脉管制冷机性能有很大影响。铅丸是常见的蓄冷材料,通常用于回热器的低温端。本文测试和分析了不同品质的国产铅丸和进口铅丸对单级G-M型脉管制冷机性能的影响。采用额定功率为6.0 kW的压缩机驱动,使用进口铅丸脉管制冷机最低制冷温度达12.9 K,这是当前单级脉管制冷机达到的最低制冷温度;40 K时的最大制冷量为57.4 W。使用国产铅丸最低制冷温度为13.6 K,40 K时的最大制冷量为55.9 W。本文对低温制冷机蓄冷材料选择具有一定的参考价值。 相似文献
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Low-temperature heat capacities and standard molar enthalpy of formation of N-methylnorephedrine C11H17NO(s) 下载免费PDF全文
This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO(s) have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO(s) relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle. 相似文献
95.
Visible and NIR luminescence of nanocrystalline β-Ga2O3:Er prepared by solution combustion synthesis
In this paper we report on facile solution combustion synthesis of erbium doped β-Ga2O3 with urea as fuel. The product was characterized using powder X-ray diffraction and transmission electron microscopy (TEM). X-ray diffraction and TEM showed that the material is nanostructured. Luminescence properties of β-Ga2O3:Er are studied with excitation in near infrared (Nd:YAG laser at 1064 nm) and visible (argon laser at 514.5 nm). A strong NIR emission of Er3+ in the window of minimal optical loss in silica based optical fibers, due to the 4I13/2→4I15/2 transition at 1.55 μm has been observed. Codoping with Yb3+ significantly increases the intensity of that important emission. 相似文献
96.
Based on the state equation of an ideal quantum gas, the regenerative loss of a
Stirling engine cycle working with an ideal quantum gas is calculated. Thermal
efficiency of the cycle is derived. Furthermore, under the condition of quantum
degeneracy, several special thermal efficiencies are discussed. Ratios of thermal
efficiencies versus the temperature ratio and volume ratio of the cycle are made. It
is found that the thermal efficiency of the cycle not only depends on high and low
temperatures but also on maximum and minimum volumes. In a classical gas state
the thermal efficiency of the cycle is equal to that of the Carnot cycle. In an ideal
quantum gas state the thermal efficiency of the cycle is smaller than that of the
Carnot cycle. This will be significant for deeper understanding of the gas Stirling
engine cycle. 相似文献
97.
Umair Ahmed Charles Turquand d’Auzay Masaya Muto Nilanjan Chakraborty Ryoichi Kurose 《Proceedings of the Combustion Institute》2019,37(3):2821-2830
The statistical behaviour of the variances, covariance and gradients of the reaction progress variable (c), and the mixture fraction (ξ) have been analysed in a pulverised coal jet flame using a three-dimensional carrier phase direct numerical simulation (DNS) dataset. It has been observed that the Favre-probability density functions (PDFs) of c and ξ can be parametrised by the standard β function. Furthermore, the log-normal distribution has been found to accurately represent |?c| and |?ξ|. It is also found that ?c and ?ξ remain aligned throughout the flame brush. Finally the joint PDF of |?c| and |?ξ| has been compared with the product of the PDF of |?c| and PDF of |?ξ| extracted from carrier phase DNS, and it has been found that |?c| and |?ξ| are not statistically independent in the case investigated.The bivariate log-normal distributions with and without correlation have also been considered, and the former is found to be in better agreement with the carrier phase DNS data. 相似文献
98.
Meng Zang Chaocheng Zhao Yongqiang Wang Shuiquan Chen 《Journal of Saudi Chemical Society》2019,23(6):645-654
Along with the rapid development of industry, VOCs gradually move into the spotlight, and now become a kind of harmful environmental pollutants that cannot be overlooked. This paper introduces the hazards of VOCs and the common catalytic combustion catalysts, noble metal catalysts and non-noble metal catalysts, for the elimination of VOCs. Perovskite catalysts, as one of the non-noble catalysts, play an important role in the field of catalytic combustion in recent years. According to the classification of elements doping in perovskites, the research achievements in the past five years were analyzed and reviewed. In addition, this paper also analyzes and elaborates the reaction kinetics and QSAR/QSPR models for the introduction of structural properties and reaction mechanisms. 相似文献
99.
Laser absorption spectroscopy (LAS) has been rapidly developed and widely applied to combustion diagnosis in recent decades. As a cost-effective tool for measuring multiple combustion parameters, LAS provides unique properties in terms of accuracy and sensitivity for understanding the reactions and kinetics in reactive flows. Line-of-sight and tomographic LAS techniques have stimulated numerous applications and been proved to be robust for in situ combustion diagnosis in uniform and non-uniform combustion fields, respectively. This review highlights the breakthroughs in the evolution of LAS techniques from the viewpoints of key principles, sensors and instrumentations developed for combustion diagnosis, with particular emphasis on a series of spatially-resolved LAS techniques with their recent applications on obtaining high-fidelity measurement results with minimal intrusion to the practical combustors. Along the way, we note some challenges and requirements for further development of the LAS-based combustion diagnosis. 相似文献
100.
Detailed gas-phase chemical kinetic models are widely used in combustion research, and many new mechanisms for different fuels and reacting conditions are developed each year. Recent works have highlighted the need for error checking when preparing such models, but a useful community tool to perform such analysis is missing. In this work, we present a simple online tool to screen chemical kinetic mechanisms for bimolecular reactions exceeding collision limits. The tool is implemented on a user-friendly website, cloudflame.kaust.edu.sa, and checks three different classes of bimolecular reactions; (ie, pressure independent, pressure-dependent falloff, and pressure-dependent PLOG). In addition, two other online modules are provided to check thermodynamic properties and transport parameters to help kinetic model developers determine the sources of errors for reactions that are not collision limit compliant. Furthermore, issues related to unphysically fast timescales can remain an issue even if all bimolecular reactions are within collision limits. Therefore, we also present a procedure to screen ultrafast reaction timescales using computational singular perturbation. For demonstration purposes only, three versions of the rigorously developed AramcoMech are screened for collision limit compliance and ultrafast timescales, and recommendations are made for improving the models. Larger models for biodiesel surrogates, tetrahydropyran, and gasoline surrogates are also analyzed for exemplary purposes. Numerical simulations with updated kinetic parameters are presented to show improvements in wall-clock time when resolving ultrafast timescales. 相似文献