最新刊期
卷 55 ， 期 11 ， 2021
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Numerical Investigation on the Flow and Heat Transfer Characteristics of the Flow-Around Rib Channel
摘要：To further improve the heat transfer performance and reduce the pressure loss in the internal cooling of gas turbine blade, the flow and heat transfer characteristics of six rib structures in the rectangular channel were numerically studied by CFX software under the Reynolds number of 20 000-80 000. The aspect ratio of the rectangular channel was 4:1, and the rib spacing to rib height ratio(p/e)was 10. The results show that the recirculation zone has a great influence on the heat transfer performance downstream of the rib, and weakening the recirculation zone will reduce the heat transfer performance. The flow-around rib can eliminate the heat transfer deterioration area near the bottom of the leading/trailing edge of the solid rib channel, and the square flow-around rib channel has better thermal performance than the circular flow-around rib channel. For the flow-around rib channels, with the decrease of the rib cross-sectional area reduction ratio ψ, the thermal performance of the channel improves, but the friction factor is increased. The square flow-around ribs with large side-lengths obtain the best thermal performance and heat transfer performance among the ribs studied in this paper. Compared with the solid ribs, the area average Nusselt number of the square flow-around ribs with large side-lengths increases by 0.92%-2.73%, and the friction factor in the heating section decreases by 10.89%-11.01%, which makes the thermal performance factor increase by 4.92%-6.75%.关键词：flow-around rib;ribbed channel;heat transfer enhancement;thermal performance;numerical simulation242|6|0更新时间：2025-07-09 - 摘要：To study the heat storage characteristics of a square phase change heat storage unit in the vertical direction, a phase change heat storage experimental rig with visualized phase interface was designed and built independently. Three structures of pure paraffin, metal foam, and fin-metal foam were experimentally explored. In the experiment, a fixed camera was used to shoot the change of phase interface during melting, and thermocouple measuring points were arranged in the heat storage unit to record the temperature change at certain distances from the bottom plate. Results indicated that at the heat source temperature of 70 ℃, the addition of metal foam played a leading role in the effect on the complete melting time. The total melting time of the copper foam group was 56.53% of that of the pure paraffin group. Nevertheless, adding fins had little effect on the total melting time, mainly affected the temperature uniformity in phase change materials. The phase interface of the fin-copper foam group moved with the fin as the center, and the temperature rising rate of the whole heat accumulator increased obviously in the solid-phase heating stage and at the end of phase transition stage.关键词：phase change heat storage;porous media;visualized experiment;solid-liquid phase change113|5|0更新时间：2025-07-09
- 摘要：It is very difficult to detect weak signatures for the early fault diagnosis of aero-engine bearings due to fewer vibration transducers and stronger non-Gaussian noises. Therefore, prior knowledges of latent subcomponents of aero-engine vibration signals are investigated, then the low rank pattern of the fault features in the tailored two-dimensional transformation space and the sparse structure of harmonic interference signals in the frequency domain are revealed. Moreover, the low-rank regularization in spatial domain and the sparse regularization in spectral domain are established. Based on the two regularization priors, a collaborative sparse low-rank model(CSLM)is proposed. The CSLM emphatically exploits structural differences of fault signals and interference signals in different transformation spaces, and further describes these differences in two completely uncoupled spaces, which provides a favorable way to construct highly incoherent dictionaries for sparse decomposition strategy. The simulation results verify that the proposed method can decouple the hidden impulsive features from strong harmonic interferences and noises, and meanwhile reliably discover fault sources. Two aero-engine bearing experiments indicate that the CSLM can effectively detect the fault patterns of aero-engine bearing with spalling area of 1.0 mm2 at running speed up to 18 000 r/min, and reliably identify the weak characteristic information of bearing faults even in the initial stage of an accelerated fatigue life cycle experiment.关键词：aero-engine bearing;fault diagnosis;non-Gaussian noise;sparse optimization;low rank decomposition95|8|0更新时间：2025-07-09
- 摘要：In order to alleviate the economic-environmental contradiction faced by iron and steel enterprises, a multi-objective and multi-period mixed integer nonlinear programming model is proposed for the steam power system(SPS)of iron and steel enterprises, which covers the pollutant emission in the upstream process. On the basis of considering dynamic supply and demand, time-of-use electricity price, and fuel structure, the whole process multi-energy optimal dispatching of SPS in iron and steel enterprises is realized through using the economic index of operating cost and the environmental index established by life cycle assessment method(LCA). The solution and data processing of the model are completed through the interaction between GAMS platform and MATLAB. The simulation results show that the optimization model and method can establish a reasonable load distribution scheme, production scheduling and power grid transaction plan for SPS of iron and steel enterprise, and provide a trade-off between environmental impact and economic cost. Compared with the results without optimization, economic optimization can reduce the operating cost of the system by 3.75%, environmental optimization can reduce the environmental impact of the system by 12.21%. The double-objective trade-off point can reduce the environmental impact by 11.91%, the operating cost by 3.46%, and more economic and environmental benefits are achieved. In a certain range, the increase of coal price can reduce the contradiction between economic and environmental optimization, while the use of blast furnace gas can significantly reduce the operating cost of the whole system, cut down the environmental impact of the whole system to a certain extent, but will increase the emissions of CO2 and NOx from the system. These results may serve as a theoretical basis for reducing economic cost and environmental impact of enterprises, and improving energy conservation and emission reduction.关键词：iron and steel enterprises;steam power system;multi-objective optimization;life cycle assessment;time-of-use electricity price97|4|2更新时间：2025-07-09
- 摘要：In order to explore the pyrolysis characteristics of oxygenated fuels under high temperature and low pressure conditions, ethanol and dimethyl ether(DME)were used as the research objects in shock tubes to conduct the pyrolysis experiment. The concentrations of four pyrolysis products of methane, acetylene, ethylene and formaldehyde in ethanol and dimethyl ether pyrolysis at 1 200-1 700 K and 0.20-0.25 MPa were tested by gas chromatograph. Also, direct relationship graph method was used to establish a detailed, combined and simplified model(DME-Ethanol model), then ROP analysis and sensitivity analysis were performed. The results show that dimethyl ether and ethanol are mainly consumed by the H-abstraction reactions initiated by H and CH3, etc.; the proportion of dimethyl ether consumed by unimolecular dissociation reactions is larger than that of ethanol due to its unique symmetrical structure. More methyl groups increase the reactivity of dimethyl ether pyrolysis. The concentration prediction errors of the DME-Ethanol model for the pyrolysis products are within 10%.关键词：shock tube;ethanol;dimethyl ether;pyrolysis products;chemical kinetics45|4|0更新时间：2025-07-09
- 摘要：To deal with the problem that the current deep multi-view subspace clustering methods lack robustness due to the lack of low-rank representation constraints on the self-representation matrix, we propose a novel deep low-rank multi-view subspace clustering(DLRMSC)method. Based on the deep multi-view subspace clustering algorithm, the self-expression layer is split into two low-rank linear self-expression layers: the commonly shared self-expression layer and the view-specific self-expression layer, which becomes a double-layer self-expression module with low-rank constraint. To make full use of the complementarity of multi-view data, the parameters of the commonly shared self-expression layer are forced to be the same, but the parameters of specific self-expression layer are different. We embed the self-expression module in the middle of the deep auto-encoder of each view, so as to obtain a deep low-rank multi-view subspace clustering model which can be solved by backpropagation. In the training stage, the commonly shared self-expression layer extracts the common information of multi-view data, the view-specific self-expression layer extracts the specific information of each view, and the double-layer self-expression module guarantees low-rank representation constraint. The experimental results on six public datasets show that compared with the deep multi-view subspace clustering algorithm, the clustering accuracy and normalized mutual information(NMI)of this proposed method on six datasets are significantly improved, where the average accuracy is increased by 0.064 and the average NMI is increased by 0.064. The DLRMSC method substantially outperforms the eleven comparative state-of-the-art clustering methods, and its accuracy is increased by 0.097 and NMI is increased by 0.103 at most.关键词：multi-view clustering;subspace clustering;autoencoder;matrix factorization;low-rank representation62|4|0更新时间：2025-07-09
- 摘要：Aiming at the difficulty of quantitatively predicting the sound absorption coefficient of a microstructural foam material through its microstructure size, an SEM method is proposed to establish a simplified unit model of the microstructural aluminum foam. Using this model to simulate the topology of the microstructural aluminum foam, the relationship between the unit's topological characteristics and the key non-acoustic parameters, including static flow resistance, viscous characteristic length, thermal characteristic length, and tortuosity coefficient, can be established. On the basis of the simplified unit model, the open porosity is introduced to clarify the relationship between the porosity and tortuosity of the microstructural foam material. So the accuracy for predicting the sound absorption coefficient of the microstructural aluminum foam is improved. The BK impedance tube is used to measure the sound absorption coefficient of the microstructural aluminum foam specimen, and the experimental measurement results are consistent with the theoretical prediction results. The specimens with a thickness less than 30 mm prepared in this research achieve broad-band and high-efficiency sound absorption, with an average sound absorption coefficient of 0.8 in the 1 100-6 500 Hz frequency band. This research may provide a basis for the design, optimization and preparation of microstructural foam materials with better sound absorption behavior.关键词：microporous foam;sound absorption;simplified sound absorption model;broadband34|4|0更新时间：2025-07-09
- 摘要：In order to obtain the mechanism of catalytic hydrodenitrogenation reaction of quinoline, an important nitrogen-containing substance difficult to degrade in bio-oil, in hydrothermal conditions, the conversion and product distribution of quinoline under the action of Ni-Ru composite metal catalyst were studied. Experimental results showed that: the addition of formic acid induced higher quinoline conversion rate, while adding gaseous hydrogen was more conducive to the formation of denitrification products; aniline and methylaniline were the main ring opening compounds of quinoline piperidine; and 2-hexene and toluene were the main hydrodenitrogenation products. According to the product distribution law, the hydrothermal hydrodenitrogenation reaction network of quinoline was obtained, and it was found that the reaction of quinoline under supercritical water conditions conformed to the first-order reaction rule. The Weisz-Prater formula proved that the reaction of quinoline in supercritical water was not affected by the diffusion of mass transfer resistance. TEM characterization of the catalyst showed that the Ni-Ru bimetallic particles in the prepared catalyst were uniformly distributed on the γ-Al2O3 support, but some active metals agglomerated in hydrothermal conditions.关键词：quinolone;hydrodenitrogenation;catalysis;hydrothermal reaction;kinetics43|5|0更新时间：2025-07-09
- 摘要：A visual testing system for the bubble point pressure of screens is established to investigate the gas-liquid separation performance of screen channel liquid acquisition devices(LADs). The bubble point pressure of Dutch twill screen(DTW)with three woven densities(100×800, 200×600 and 200×1 400)is tested using isopropyl alcohol as working fluid. The influence of the gas pressurization rate on the bubble point pressure is compared and analyzed, and the effective pore diameters of the three screen samples are obtained. Results show that the bubble point pressure shows a good linear decreasing trend with the pressurization rate when the pressurization rate is relatively low. The static bubble point pressures of the three screen samples in isopropyl alcohol obtained by data linear fitting are 1 847.2 Pa, 2 047.2 Pa and 3 371.0 Pa, respectively. With the increase of the pressurization rate, the bubble breakthrough intensity of the screen increases continuously, and gradually changes from local breakthrough with small bubbles to dramatic breakthrough in large screen area. The effective pore diameters of the three screen samples of DTW with woven densities of 100×800, 200×600 and 200×1 400 are about 47.88 μm, 43.20 μm and 26.24 μm, respectively. With the increase of woven density, the effective pore diameter of the screen decreases and the bubble point pressure increases gradually, which reflects stronger barrier property against gas.关键词：gas-liquid separation;liquid acquisition device;metallic screen;bubble point pressure;pressurization rate44|8|0更新时间：2025-07-09
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