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1.
《International Journal of Hydrogen Energy》2022,47(19):10747-10761
To obtain the mixing enhancement mechanism of H2–Water combined jets in supersonic crossflows in a combustor with expanded section for rotating detonation ramjet, the flow field shape and spray structure were studied by experimental and numerical methods. The Eulerian–Lagrangian method was used to investigate the diffusion mechanism and H2–Water interaction law of combined jets with different sequences. At the same time, high-speed photography and the schlieren technique were used to capture the flow field. The effects of jet pressure drop, orifice diameter, orifice spacing, incoming Mach number, and other parameters on the penetration depth of water jets were studied. The results of experiment and simulation show that using H2–Water combined jets, the penetration depth of the jet spray can be greatly increased and the jet mixing effect can be significantly improved, which will contribute to the engine's ignition and stable combustion. In the case of pre-water/post-H2, the penetration depth of the hydrogen jet is greater. In the case of pre-H2/post-water, the hydrogen jet raises the water spray mainly by protecting the integrity of the water column. 相似文献
2.
Nicholas Dudalski Ahmed Mohamed Samira Mubareka Ran Bi Chao Zhang Eric Savory 《Indoor air》2020,30(5):966-977
Seasonal influenza epidemics have been responsible for causing increased economic expenditures and many deaths worldwide. Evidence exists to support the claim that the virus can be spread through the air, but the relative significance of airborne transmission has not been well defined. Particle image velocimetry (PIV) and hot-wire anemometry (HWA) measurements were conducted at 1 m away from the mouth of human subjects to develop a model for cough flow behavior at greater distances from the mouth than were studied previously. Biological aerosol sampling was conducted to assess the risk of exposure to airborne viruses. Throughout the investigation, 77 experiments were conducted from 58 different subjects. From these subjects, 21 presented with influenza-like illness. Of these, 12 subjects had laboratory-confirmed respiratory infections. A model was developed for the cough centerline velocity magnitude time history. The experimental results were also used to validate computational fluid dynamics (CFD) models. The peak velocity observed at the cough jet center, averaged across all trials, was 1.2 m/s, and an average jet spread angle of θ = 24° was measured, similar to that of a steady free jet. No differences were observed in the velocity or turbulence characteristics between coughs from sick, convalescent, or healthy participants. 相似文献
3.
Shengyue Gu Shouyang Zhang Fei Liu Wei Li 《Journal of the European Ceramic Society》2018,38(15):5082-5091
Y2Hf2O7 possesses low thermal conductivity and high melting point, which make it promising for a new anti-ablation material. For evaluating the thermal stability and the potential applications of Y2Hf2O7 on anti-ablation protection of C/C composites, Y2Hf2O7 ceramic powder was synthesized by solution combustion method and Y2Hf2O7 coating was prepared on the surface of SiC coated C/C composites using SAPS. Results shown that the coating exhibits good ablation resistance under the heat flux of 2.4?MW/m2 with the linear and mass ablation rates are 0.16?μm?s?1 and ?0.028?mg?s?1, respectively, after ablation for 40?s. With the prolonging of the ablation time, the increasing thermal stress causes the increase of cracks. Moreover, the chemical erosion from SiO2 and the physical volatilization of low temperature molten products aggravate failure of the Y2Hf2O7 coating. 相似文献
4.
针对辛置煤矿10#煤综采工作面煤层自然发火的特点,采用现场实测分析及注胶防灭火的方法,对工作面煤体漏风情况、回采巷道内风流温度、CO及CH4浓度进行了监测,并应用了注胶防灭火的技术。针对工作面煤体内多处漏风严重,应用粉煤灰、高分子胶体注胶技术进行防治后,各监测点风流温度及煤层温度均得到有效降低,保证了工作面安全推进。 相似文献
5.
Supersonic separators (3Ss) are applied in gas separation processes. Two-dimensional simulation is employed to investigate the effect of operational and thermophysical parameters on the shockwave position. In addition, the impact of the cyclonic part and wet outlet geometry is evaluated by proposing four cases. Increasing the length of the cyclonic part exerts positive and negative influences on the performance of the 3S and the pressure recovery coefficient, respectively. The optimum length is determined between 10 and 15 cm. To demonstrate negative effects of wasted air from the wet outlet, its flow has been increased from 3.6 to 8.1 % of the inlet flow. Improved performance of the 3S is obtained by reducing the flow disturbances around the wet outlet and moving the shockwave towards the outlet. 相似文献
6.
《Ceramics International》2020,46(6):7374-7387
Carbon/carbon (C/C) surface micropatterning is a method of modifying the surface into the complete and regular geometry. In this work, we introduce a positive effect on bonding strength between sprayed Ca–P coating and surface micropatterning C/C substrate. Interestingly, C/C substrate coated by Ca–P coating provides textured surface for a new bone ingrowth. The sprayed Ca–P coating is then subjected to microwave-hydrothermal (MH) treatment with the aim of eliminating surface defects and obtaining a uniform purity phase. These objectives were achieved in our previous study by the MH method. The molar ratio of Ca/P in the coatings is nearly close to 1, which is far below that of Ca/P for hydroxyapatite (Ca10(PO4)6(OH)2, HA, 1.67). The purpose of this article is to transform the phases in the sprayed Ca–P coating, which owns the better bioactivity and high corrosion resistance. In order to raise the molar ratio of Ca/P, the coatings are treated under high-temperature (around 700 °C). They are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and a fourier transform infrared spectra (FTIR). The bonding strength (coating/substrate), biological activity and corrosion resistance of the coatings are investigated. The resulting coatings own the different microstructures and phase compositions from the original sprayed Ca–P coating. Especially, results show that the shear strength of the sprayed Ca–P coating deposited on surface micropatterning C/C substrate increases by 61% which is more than that of the coating on non-surface micropatterning C/C substrate. Additionally, high-temperature treated coating presents a good biological activity and an excellent corrosion resistance of current density (1.3078 × 10-6 A/cm2) and potential (−0.17 VSCE). 相似文献
7.
Peter F. Johnson 《Fire Technology》1986,22(1):14-32
A recent fire in a computer center in Canberra, Australia, prompted an investigation of the installed smoke detection system. The opportunity was also taken to evaluate alternate detection equipment in the actual center under operational conditions. One device tested was VESDA, a new highly sensitive smoke detector developed in Australia for clean occupancies such as computer rooms and telephone exchanges. Details of the test program and the effects of high room airflows on all forms of detectors are presented. The effectiveness of VESDA in giving very early warning of fire is demonstrated.
Reference: Peter F. Johnson, Fire Detection in Computer Facilities,Fire Technology, Vol. 22, No. 1, February 1986, p. 14.
Note: This paper is a modified version of a CIRL Major Report No. 251, 1984, prepared for Department of Housing and Construction, Canberra, Australia. 相似文献
8.
本文介绍了某HERMES专营店的空调设计方法。为了使室内获得舒适的温度以及合理的气流组织形式,笔者建立了专营店空调设计的物理几何模型,利用CFD软件对该有限空间的气流场和温度场进行了仿真模拟,并根据仿真结果修正了原有的空调设计方案。专营店的空调正常运行后,笔者又对其运行状况进行了现场测量,并将测量记录的结果与CFD仿真模拟结果进行对比分析,符合性较好。本文的研究可以作为利用CFD软件评估和指导有限空间空调设计的有益尝试。 相似文献
9.
Dispersion characteristics of expiratory aerosols were investigated in an enclosure with two different idealized airflow patterns: the ceiling-return and the unidirectional downward. A multiphase numerical model, which was able to capture the polydispersity and evaporation features of the aerosols, was adopted. Experiments employing optical techniques were conducted in a chamber with downward airflow pattern to measure the dispersion of aerosols. Some of the numerical results were compared with the chamber measurement results. Reasonable agreement was found. Small aerosols (initial size 相似文献
10.
套室内人体热舒适的研究 总被引:2,自引:3,他引:2
借助于通用流场计算软件PHOENICS,在考虑了外界气温、太阳的热辐射条件,家具以及人员等室内微气候影响的情况下,预测了两室一厅套室内气流三维流场和温度场。得到了套室内气流的速度、温度和人体热舒适指数等参数的分布,并经过评定,该套室内的热环境达到了人体的舒适性要求。模拟计算结果对套室的设计及其空调系统的配置具有重要的参考价值,并为套室内人体热舒适的进一步研究和室内空气品质问题的研究奠定了基础。 相似文献