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941.
Qianqing Liang Xuehu Ma Kai Wang Jiang Chun Zhong Lan Tingting Hao Yaxiong Wang 《中国化学工程学报》2019,27(11):2615-2625
In order to reduce or avoid the fluctuations from interface breakup, a meandering microchannel with curved multi-bends (44 turns) is fabricated, and investigations of scaling bubble/slug length in Taylor flow in a rectangular meandering microchannel are systematically conducted. Based on considerable experimental data, quantitative analyses for the influences of two important characteristic times, liquid phase physical properties and aspect ratio are made on the prediction criteria for the bubble/slug length of Taylor flow in a meandering microchannel. A simple principle is suggested to predict the bubble formation period by using the information of Rayleigh time and capillary time for six gas-liquid systems with average deviation of 10.96%. Considering physical properties of the liquid phase and cross-section configuration of the rectangular mcirochannel, revised scaling laws for bubble length are established by introducing Ca, We, Re and W/h whether for the squeezing-driven or shearing-driven of bubble break. In addition, a simple principle in terms of Garstecki-type model and bubble formation period is set-up to predict slug lengths. A total of 107 sets of experimental data are correlated with the meandering microchannel and operating range:0.001 < CaTP < 0.05, 0.06 < WeTP < 9.0, 18 < ReTP < 460 using the bubble/slug length prediction equation from current work. The average deviation between the correlated data and the experimental data for bubble length and slug length is about 9.42% and 9.95%, respectively. 相似文献
942.
943.
基于煤粉燃烧机理,结合骨料烘干工艺,建立了骨料烘干煤粉燃烧器内部场的控制模型,采用Fluent软件模拟煤粉燃烧器内部燃烧状况,考察了一、二、三次风的风速对煤粉燃烧器中心轴线处CO, CO2, NO和SO2浓度的影响。结果表明,在研究的风速范围内,一、二、三次风风速越大燃烧越充分,一、二、三次风风速越小,产生的NO越少;三次风风速为40 m/s时,SO2浓度最低;较合理的控制参数为一次风风速30~35 m/s,二次风风速45~50 m/s,三次风风速30~40 m/s。 相似文献
944.
《International Journal of Hydrogen Energy》2019,44(11):5143-5152
In order to study the harmonic resonance characteristics of single-stage photovoltaic (PV) grid-connected/hydrogen production multi-inverter system, the modal analysis method was used to systematically analyze and discuss the resonance problem. First, a three-phase single-stage photovoltaic grid-connected/hydrogen production system simulation model was established, and hydrogen production from water electrolysis was used as a local load. Secondly, this paper applied a modal analysis method that could determine the system resonance frequency, resonance center and the participation degree of each component by constructing the multi-inverter system node admittance matrix. Finally, the Thevenin equivalent model of multi-inverter system was established based on the modal analysis method. The influence of the number of inverters on the resonance characteristics of the system was studied. Compared with the frequency response analysis of the transfer function, the simulation results verify the correctness and effectiveness of the modal analysis method. 相似文献
945.
《International Journal of Hydrogen Energy》2019,44(11):5454-5461
A regenerative braking energy recovery strategy based on pontryagin's minimum principle (PMP) for Fuel Cell (FC)/Supercapacitor (SC) hybrid power locomotive was proposed in this paper. In the proposed strategy, the dynamic coefficient λ is used in PMP during the traction state of the locomotive, which makes system transient hydrogen consumption minimum. What's more, during locomotives brake state, according to the known parameters of SCs and operation indicators, an optimized braking speed curve can also be obtained which has maximum brake recovery rate. The results are obtained from RT-LAB platform testify that the proposed strategy is able to maximize SC absorption braking energy, and the energy recovery rate improves and maintains SC state of charge (SoC) in a reasonable and safe range, and decreases brake resistors energy consumption in the braking process. 相似文献
946.
《International Journal of Hydrogen Energy》2019,44(55):29224-29234
For gaining further insight into the involvement of the gaseous and electrochemical hydrogen storage properties of CeMg12-type alloys, partial substitution and ball milling were both used to synthesize the nanocrystalline and amorphous CeMg11Ni + x wt.% Ni (x = 100, 200) samples. This research aims at elucidating the functional roles of Ni content and milling time on samples' structure and hydrogen storage performance. X-Ray diffraction and high-resolution transmission electron microscope were used to reveal the micro constructions of alloys. To determine the gaseous hydrogen storage property, Sievert's apparatus and a thermal gravity analysis bonded with a H2 probe were adopted. The dehydrogenation activation energy was computed in the Kissinger method. The electrochemical performances of the as-milled samples were measured through a constant current system. Further researches showed that the electrochemical performance of as-milled samples had been dramatically improved by increasing Ni content. With milling duration lengthens, the gaseous hydrogen absorption capacity, gaseous hydriding rate and high rate discharge capability of samples reached the maximal values, but electrochemical discharge capacity and gaseous dehydriding rate always increased. The dehydrogenation activation energy decrease resulted by improving Ni percent and milling duration was deemed as the cause of the excellent gaseous kinetics of samples. 相似文献
947.
《International Journal of Hydrogen Energy》2019,44(11):5262-5269
Hydrogen energy can be generated by steam methane reforming method, and methane production from coal seams is important to ensure the abundance of hydrogen energy generation. The gaseous compound of hydrogen and carbon production performance analysis is important and pressure transient analysis can be used to analyze the flow characteristics in the development of gaseous compound of hydrogen and carbon in coalbed reservoir. The computational models on vertical wells, vertically fractured wells and horizontal wells have been studied intensively in coalbed reservoir to predict gaseous compound of hydrogen and carbon production behavior. For a thin coalbed methane reservoir, it will be more effective to develop through forming horizontal fractures near the wellbore. However, such model has not been established. To analyze gaseous compound of hydrogen and carbon production performance for horizontal fractures in coalbed methane reservoirs, this paper presents a 3D point-sink model and the corresponding solution is obtained through using Laplace transform and Fourier transform methods. The point-source integral method is used to obtain the general solutions of gaseous compound of hydrogen and carbon flow through horizontal fractures. The pressure transient solution have been compared with numerical simulation to validate its accuracy. Type curves are established to analyze the flow characteristics of gaseous compound of hydrogen and carbon, which can be divided into four regions, i.e., linear flow region, transition flow region, inter-porosity flow region, and radial flow region. The sensitive analysis of the key model parameters on type curves has been conducted. 相似文献
948.
《International Journal of Hydrogen Energy》2019,44(11):5585-5591
The effect of hydrogen on the premixed combustion of low calorific value gas in cylinder was carried out. The engine bench test system was built, and the effects of hydrogen on the pressure in cylinder, the characterization parameters of flame stability, flame shape, combustion cycle variation, flame surface structure and development were studied. The experimental results show that adding hydrogen to low calorific value gas fuels can increase laminar flame propagation rate, increase heat release rate, improve engine volumetric efficiency and reduce engine cycle variation. With the increase of hydrogen fraction, the maximum cylinder pressure of the engine rises, the corresponding crankshaft angle moves forward, and the flame development period and the rapid combustion period of the engine working cycle are reduced. The flame propagation rate of hydrogen blended low calorific value gas is larger, which enhances the strength of the vortex blob in cylinder to some extent. The increase of hydrogen fraction in mixture increases the flame propagation velocity, and enhances the effect of the combustion process on vortex intensity in cylinder, which increasing the effect of vortex blob on the flame surface structure. With the increase of hydrogen fraction, the vortices of the flow field in the cylinder increase, the time of which the flame surface reaches the same fold is in advance, and the flame development period is shortened. 相似文献
949.
《International Journal of Hydrogen Energy》2019,44(55):29371-29379
The paper analyzes the effect of electrolytic hydrogenation on martensite transformation temperatures in binary TiNi alloys. The analysis shows that this effect can be strong or weak depending on the phase state of TiNi. Research data are presented on the diffusivity of hydrogen in binary TiNi alloys in martensite and austenite states. The diffusion coefficient of hydrogen is estimated from its distribution measured by glow discharge spectroscopy in TiNi after hydrogenation. The experimental results about the formation of TiNiH hydride in the martensitic and austenitic state in binary TiNi based alloys are also presented. 相似文献
950.
《International Journal of Hydrogen Energy》2019,44(54):28757-28768
Improved catalytic centres with a minimum mass-loading of expensive platinum (Pt) have been anticipated for various catalytic applications, for instance preferential oxidation (PROX) of carbon monoxide (CO) in the presence of Hydrogen. Here, we report the synthesis of nano-Pt on the surface of copper (Cu) nanoparticles (NPs) supported on γ-Al2O3 (Ptn(Cu)/γ-Al2O3) via galvanic displacement reaction (GDR) for the catalytic CO-PROX reaction. Ptn(Cu)/γ-Al2O3 showed much improved CO-PROX performance compared to that of the as-synthesized Ptl(Cu)/γ-Al2O3 catalyst. Importantly, no significant conversion of hydrogen at a lower temperature range (<200 °C) is observed during the CO-PROX reaction which is one of the essential prerequisites for the CO-PROX reaction. Moreover, Ptn(Cu)/γ-Al2O3 showed the durable, long-term catalytic CO-PROX performance for 120 h. These results infer that realization of nano-Pt on the surface of the Cu NPs holds the promise as the catalytic centres with the minimum mass-loading of Pt for the CO-PROX reaction. 相似文献