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Numerical and experimental analyses of methane leakage in shield tunnel

《结构与土木工程前沿（英文）》   页码 1011-1020 doi: 10.1007/s11709-023-0956-z

摘要： Tunnels constructed in gas-bearing strata are affected by the potential leakage of harmful gases, such as methane gas. Based on the basic principles of computational fluid dynamics, a numerical analysis was performed to simulate the ventilation and diffusion of harmful gases in a shield tunnel, and the effect of ventilation airflow speed on the diffusion of harmful gases was evaluated. As the airflow speed increased from 1.8 to 5.4 m/s, the methane emission was diluted, and the methane accumulation was only observed in the area near the methane leakage channels. The influence of increased ventilation airflow velocity was dominant for the ventilation modes with two and four fans. In addition, laboratory tests on methane leakage through segment joints were performed. The results show that the leakage process can be divided into “rapid leakage” and “slight leakage”, depending on the leakage pressure and the state of joint deformation. Based on the numerical and experimental analysis results, a relationship between the safety level and the joint deformation is established, which can be used as guidelines for maintaining utility tunnels.

关键词： shield tunnel     harmful gas leakage     numerical analysis     laboratory test    

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Aggravation of membrane fouling and methane leakage by a three-phase separator in an external anaerobic

Chao Pang, Chunhua He, Zhenhu Hu, Shoujun Yuan, Wei Wang

《环境科学与工程前沿（英文）》 2019年 第13卷 第4期 doi: 10.1007/s11783-019-1131-6

摘要：

The existence of three-phase separator did not affect COD removal in the EAnCMBR.

The existence of three-phase separator aggravated methane leakage of EAnCMBR.

The existence of three-phase separator aggravated membrane fouling rate of EAnCMBR.

Start-up of EAnCMBR equipped three-phase separator was slightly delayed.

关键词： Anaerobic membrane bioreactor     Three-phase separator     Membrane fouling     Methane leakage     Sludge property    

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Dissolved methane in anaerobic effluent: Emission or recovery?

《环境科学与工程前沿（英文）》 2022年 第16卷 第4期 doi: 10.1007/s11783-022-1537-4

摘要： Various anaerobic processes have been explored for the energy-efficient treatment of municipal wastewater. However, dissolved methane in anaerobic effluent appears to be a barrier towards the energy and carbon neutrality of wastewater treatment. Although several dissolved methane recovery methods have been developed, their engineering feasibility and economic viability have not yet been assessed in a holistic manner. In this perspective, we thus intend to offer additional insights into the cost-benefit of dissolved methane recovery against its emission.

关键词： Anaerobic treatment     Municipal wastewater     Dissolved methane     Methane recovery     Carbon emission    

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Effects of leakage and friction on the miniaturization of a Wankel compressor

Yilin ZHANG, Wen WANG

《能源前沿（英文）》 2011年 第5卷 第1期   页码 83-92 doi: 10.1007/s11708-010-0125-7

摘要： This paper presents a numerical simulation of the performance of a meso-scale Wankel compressor and discusses the factors affecting its miniaturization. The discussion is related to the effect of leakage and friction on the design limit (cooling capacity and dimension) of the meso Wankel compressor. In the simulation, the main leakage comes from the gaps between the rotor and the endplates as well as between the seal apex and the cylinder. The largest friction originates from the clearance among the end face of the eccentric shaft, the end faces of the rotor, and the endplates. The decreasing cooling capacity of the meso Wankel compressor increases the proportion of leakage to displacement and causes the coefficient of performance COP and the mechanical efficiency to decrease. The rational design cooling capacity limit for the meso-scale Wankel compressor is approximately 4 W.

关键词： meso-scale     Wankel compressor     leakage     friction    

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Cohesive zone model-based analyses of localized leakage of segmentally lined tunnels

《结构与土木工程前沿（英文）》 2023年 第17卷 第4期   页码 503-521 doi: 10.1007/s11709-023-0927-4

摘要： This paper presents a novel approach for simulating the localized leakage behavior of segmentally lined tunnels based on a cohesive zone model. The proposed approach not only simulates localized leakage at the lining segment, but also captures the hydromechanically coupled seepage behavior at the segmental joints. It is first verified via a tunnel drainage experiment, which reveals its merits over the existing local hydraulic conductivity method. Subsequently, a parametric study is conducted to investigate the effects of the aperture size, stratum permeability, and spatial distribution of drainage holes on the leakage behavior, stratum seepage field, and leakage-induced mechanical response of the tunnel lining. The proposed approach yields more accurate results than the classical local hydraulic conductivity method. Moreover, it is both computationally efficient and stable. Localized leakage leads to reduced local ground pressure, which further induces outward deformation near the leakage point and slight inward deformation at its diametrically opposite side. A localized stress arch spanning across the leakage point is observed, which manifests as the rotation of the principal stresses in the adjacent area. The seepage field depends on both the number and location of the leakage zones. Pseudostatic seepage zones, in which the seepage rate is significantly lower than that of the adjacent area, appear when multiple seepage zones are considered. Finally, the importance of employing the hydromechanical coupled mechanism at the segment joints is highlighted by cases of shallowly buried tunnels subjected to surface loading and pressure tunnels while considering internal water pressure.

关键词： segmentally lined tunnel     localized leakage     cohesive element     hydraulic behavior     numerical modeling    

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Long-term settlement behavior of ground around shield tunnel due to leakage of water in soft deposit

Huaina WU, Yeshuang XU, Shui-long SHEN, Jin-chun CHAI

《结构与土木工程前沿（英文）》 2011年 第5卷 第2期   页码 194-198 doi: 10.1007/s11709-011-0105-y

摘要： The lining of shield tunnel is usually composed of segments, in which the joints, cracks, and the grouting holes (hereafter called lining deficit) exist. During the long-term running, soils and groundwater may leak from these kinds of lining deficit. The leaking of soil and groundwater causes the long-term ground loss around tunnel and thus results in the settlement of ground surface. This paper aims to analyze the impact of the leakage of groundwater through segments on the long-term settlement of ground surface. The adopted analytical method is based on the theory of groundwater seepage by using numerical simulation. The analyzed results show that settlement of ground surface increases gradually with the increase of the leaked volume of tunnel segments. When the leaked volume was unevenly distributed, differential settlement occurred locally. Comparative analysis by changing the leaked volume was conducted. The results reveal that there is a linear relationship between settlement and leaked volume when the leaked volume was controlled within the allowable limit.

关键词： lining deficit     leakage of water     shield tunnel     settlement     soft deposit    

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A building unit decomposition model for energy leakage by infrared thermography image analysis

Yan SU, Fangjun HONG, Lianjie SHU

《能源前沿（英文）》 2020年 第14卷 第4期   页码 901-921 doi: 10.1007/s11708-020-0679-y

摘要： A quantitative energy leakage model was developed based on the thermography image data measured for both external and internal building surfaces. The infrared thermography images of both surfaces of doors, windows, and walls of an office building in the Hengqin Campus of University of Macao were taken at various times in a day for four seasons. The transient heat flux for sample units were obtained based on measurements of the seasonal transient local temperature differences and calculations of the effective thermal conductivity from the multiple-layer porous medium conduction model. Effects of construction unit types, orientations, and seasons were quantitatively investigated with unit transient orientation index factors. The corresponding electric energy consumption was calculated based on the air conditioning system coefficient of performance of heat pump and refrigerator cycles for different seasons. The model was validated by comparing to the electric meter records of energy consumption of the air conditioning system. The uncertainties of the predicted total building energy leakage are about 14.7%, 12.8%, 12.4%, and 15.8% for the four seasons, respectively. The differences between the predicted electric consumption and meter values are less than 13.4% and 5.4% for summer and winter, respectively. The typical daily thermal energy leakage value in winter is the highest among the four seasons. However, the daily electric energy consumption by the air conditioning system in summer and autumn is higher than that in winter. The present decomposition model for energy leakage is expected to provide a practical tool for quantitative analysis of energy leakage of buildings.

关键词： heat conductivity     heat coefficient     heat &fllig     ux     infrared thermography     thermal image    

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USING NUTRITIONAL STRATEGIES TO MITIGATE RUMINAL METHANE EMISSIONS FROM RUMINANTS

《农业科学与工程前沿（英文）》 2023年 第10卷 第3期   页码 390-402 doi: 10.15302/J-FASE-2023504

摘要：

● Microbial fermentation in the rumen is a main source of methane emissions.

关键词： nutritional strategy     mitigation     microbe     methane     ruminant    

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Acid Orange 7 degradation using methane as the sole carbon source and electron donor

《环境科学与工程前沿（英文）》 2022年 第16卷 第3期 doi: 10.1007/s11783-021-1468-5

摘要：

• AO7 degradation was coupled with anaerobic methane oxidation.

关键词： Azo dyes     AO7 degradation     Anaerobic methane oxidation     Microbial community     ANME-2d    

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Variation characteristics of atmospheric methane and carbon dioxide in summertime at a coastal site in

《环境科学与工程前沿（英文）》 2022年 第16卷 第11期 doi: 10.1007/s11783-022-1574-z

摘要：

● Diurnal patterns of CH4 and CO2 are clearly extracted using EEMD.

关键词： Methane     Carbon dioxide     Diurnal pattern     Ensemble empirical mode decomposition     South China Sea     Sea breeze    

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Enhanced methane production during long-term UASB operation at high organic loads as enabled by the immobilized

《环境科学与工程前沿（英文）》 2022年 第16卷 第6期 doi: 10.1007/s11783-021-1505-4

摘要：

• Fungi enable the constant UASB operation even at OLR of 25.0 kg/(m3×d).

关键词： Anaerobic digestion     Fungi     Methane production     High OLR     Microbial community    

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propionate-oxidizing microflora and its bioaugmentation on anaerobic wastewater treatment for enhancing methane

Chong Liu, Jianzheng Li, Shuo Wang, Loring Nies

《环境科学与工程前沿（英文）》 2016年 第10卷 第4期 doi: 10.1007/s11783-016-0856-8

摘要： Syntrophic propionate-oxidizing microflora B83 was enriched from anaerobic sludge. The bioaugmentation of microflora B83 were evaluated from wastewater treatment. Methane yield and COD removal were enhanced by bioaugmentation of microflora B83. Hydrogen-producing acetogensis was a rate-limiting step in methane fermentation. Methane fermentation process can be restricted and even destroyed by the accumulation of propionate because it is the most difficult to be anaerobically oxidized among the volatile fatty acids produced by acetogenesis. To enhance anaerobic wastewater treatment process for methane production and COD removal, a syntrophic propionate-oxidizing microflora B83 was obtained from an anaerobic activated sludge by enrichment with propionate. The inoculation of microflora B83, with a 1:9 ratio of bacteria number to that of the activated sludge, could enhance the methane production from glucose by 2.5 times. With the same inoculation dosage of the microflora B83, COD removal in organic wastewater treatment process was improved from 75.6% to 86.6%, while the specific methane production by COD removal was increased by 2.7 times. Hydrogen-producing acetogenesis appeared to be a rate-limiting step in methane fermentation, and the enhancement of hydrogen-producing acetogens in the anaerobic wastewater treatment process had improved not only the hydrogen-producing acetogenesis but also the acidogenesis and methanogenesis.

关键词： Anaerobic wastewater treatment     Methane production     Hydrogen-producing acetogenesis     Methanogenesis     Rate-limiting step     Bioaugmentation    

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Progress in developing an innovative lean burn catalytic turbine technology for fugitive methane mitigation

Shi SU, Xinxiang YU

《能源前沿（英文）》 2011年 第5卷 第2期   页码 229-235 doi: 10.1007/s11708-011-0147-9

摘要： Approximately 2.8 × 10 m of methane is emitted per year to the atmosphere from coal mining activities around the world. Mitigation and utilization of the fugitive coal mine methane is very difficult because its concentration is very low and varies from 0.1% to1%, and the methane is contained in a large air flow rate of 150–400 m /s. This paper overviews existing and developing technologies for the mitigation and utilization of the fugitive mine methane, and then presents research progress in developing an innovative lean burn catalytic turbine technology for fugitive methane mitigation and utilization. This turbine system can be powered with about 1% methane in air.

关键词： coal mine methane     mitigation and utilization     lean burn gas turbine     catalytic combustion    

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Transient process of methane-oxygen diffusion flame-street establishment in a microchannel

《能源前沿（英文）》 2022年 第16卷 第6期   页码 988-999 doi: 10.1007/s11708-021-0755-y

摘要： “Flame-street” is an interesting diffusion flame behavior in which a series of flame-segments is separately distributed along the mixing layer in a narrow channel. This experimental phenomenon was experimentally and numerically investigated with the focus on the steady-state, thermo-chemical flame structures in previous literature. In the present paper, the dynamic formation process of a methane-oxygen diffusion flame-street structure was simulated with a reacting flow solver developed based on the open-source framework OpenFOAM. By imposing a certain amount of ignition-energy near the channel outlet, a reaction-kernel was formed and bifurcated. Subsequently, three separate flames were consecutively generated from this kernel and propagated within the channel. The whole process was completed within 15 ms and all the discrete flames were eventually in a steady-state. Interestingly, different propagation features were observed for the three flame segments: The leading flame experienced a flame shape/type change from a tribrachial structure in its fast-propagating phase to a long, trailing diffusion tail after being anchored to the inlet. The successive flame had a much lower propagation speed, keeping its two wing-like (fuel-lean premixed and fuel-rich premixed) structure while moving toward its stabilization location, which was approximately in the middle of the channel. The last flame, after the ignition source was turned-off, was immediately convected a bit downstream, and eventually featured a similar two-branch-like structure as the second one. Moreover, chemical insights for the premixed and diffusion branches of the leading flame were also provided with the change of significance of some key elementary reactions focused on, in order to attain a detailed profiling of the flame-type transition. This paper is a first-ever one discussing the transient formation of flame-streets in literature and is believed to be useful for obtaining a comprehensive understanding of this unique flame characteristics from a dynamic point of view.

关键词： micro-combustion     flame-street     diffusion flame     mixing layer     flame propagation speed    

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ALKALINE PRETREATMENT AND AIR MIXING FOR IMPROVEMENT OF METHANE PRODUCTION FROM ANAEROBIC CO-DIGESTION

《农业科学与工程前沿（英文）》 2023年 第10卷 第3期   页码 424-436 doi: 10.15302/J-FASE-2023506

摘要：

● Integration of alkaline pretreatment and air mixing for co-digestion was validated.

关键词： sodium hydroxide     air injection     cumulative methane yield     kinetic modeling analysis     digestate    

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标题 作者 时间 类型 操作

Numerical and experimental analyses of methane leakage in shield tunnel

期刊论文

Aggravation of membrane fouling and methane leakage by a three-phase separator in an external anaerobic

Chao Pang, Chunhua He, Zhenhu Hu, Shoujun Yuan, Wei Wang

期刊论文

Dissolved methane in anaerobic effluent: Emission or recovery?

期刊论文

Effects of leakage and friction on the miniaturization of a Wankel compressor

Yilin ZHANG, Wen WANG

期刊论文

Cohesive zone model-based analyses of localized leakage of segmentally lined tunnels

期刊论文

Long-term settlement behavior of ground around shield tunnel due to leakage of water in soft deposit

Huaina WU, Yeshuang XU, Shui-long SHEN, Jin-chun CHAI

期刊论文

A building unit decomposition model for energy leakage by infrared thermography image analysis

Yan SU, Fangjun HONG, Lianjie SHU

期刊论文

USING NUTRITIONAL STRATEGIES TO MITIGATE RUMINAL METHANE EMISSIONS FROM RUMINANTS

期刊论文

Acid Orange 7 degradation using methane as the sole carbon source and electron donor

期刊论文

Variation characteristics of atmospheric methane and carbon dioxide in summertime at a coastal site in

期刊论文

Enhanced methane production during long-term UASB operation at high organic loads as enabled by the immobilized

期刊论文

propionate-oxidizing microflora and its bioaugmentation on anaerobic wastewater treatment for enhancing methane

Chong Liu, Jianzheng Li, Shuo Wang, Loring Nies

期刊论文

Progress in developing an innovative lean burn catalytic turbine technology for fugitive methane mitigation

Shi SU, Xinxiang YU

期刊论文

Transient process of methane-oxygen diffusion flame-street establishment in a microchannel

期刊论文

ALKALINE PRETREATMENT AND AIR MIXING FOR IMPROVEMENT OF METHANE PRODUCTION FROM ANAEROBIC CO-DIGESTION

期刊论文