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Fuel variability effect on flickering frequency of diffusion flames

Jizhao LI, Yang ZHANG

《能源前沿（英文）》 2009年 第3卷 第2期   页码 134-140 doi: 10.1007/s11708-009-0034-9

摘要： It is known that fuel variability of different gas suppliers may cause combustion instability in a gas turbine combustor. Mechanisms that control the time scale of the heat release oscillations and acoustic pressure perturbations are both physical and chemical in nature, and thus can be influenced by changes in fuel composition. The intent of this study is to investigate the fuel variability on the flickering frequency of diffusion flames in the hope of understanding some of the fundamental aspects of fuel variability effect on the dynamics of combustion. Experiments were conducted at atmospheric pressure with a matrix of methane and propane blends. An optical fibre system was applied to capture simultaneously the flame flickering at two different light frequencies (430 nm and 516 nm), which provided a means of comparing the chemistry change. It was found that the low frequency oscillation of flow and flame structures depended only weakly on the exit velocities of the fuel, while ambient conditions had a significant effect on flickering frequencies and spectrum. The results of using CH and C H as test fuels at different flow rates showed very little variations, with peak frequencies at 11-13 Hz. When the jet flame was not disturbed, harmonics to at least the third mode were obtained in most of these cases. However, the cases which included CH /C H splits of 90/10, 85/15 and 80/20 by volume showed that unstable flickering frequencies and flame harmonics were not observed. When a mixture of methane/propane at a ratio of 1:1 was used the peak flickering frequency was around 6 Hz, and slight disturbance in the environment would cause the harmonics to disappear. Mechanisms thought to produce changes in the dynamic response and frequency harmonics were discussed.

关键词： fuel variability     flickering frequency     diffusion flames     dynamics of combustion    

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Soil spatial variability impact on the behavior of a reinforced earth wall

Adam HAMROUNI, Daniel DIAS, Badreddine SBARTAI

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 518-531 doi: 10.1007/s11709-020-0611-x

摘要： This article presents the soil spatial variability effect on the performance of a reinforced earth wall. The serviceability limit state is considered in the analysis. Both cases of isotropic and anisotropic non-normal random fields are implemented for the soil properties. The Karhunen-Loève expansion method is used for the discretization of the random field. Numerical finite difference models are considered as deterministic models. The Monte Carlo simulation technique is used to obtain the deformation response variability of the reinforced soil retaining wall. The influences of the spatial variability response of the geotechnical system in terms of horizontal facing displacement is presented and discussed. The results obtained show that the spatial variability has an important influence on the facing horizontal displacement as well as on the failure probability.

关键词： reinforced earth wall     geosynthetic     random field     spatial variability     Monte Carlo simulation    

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Treatment, residual chlorine and season as factors affecting variability of trihalomethanes in small

Roberta DYCK,Geneviève COOL,Manuel RODRIGUEZ,Rehan SADIQ

《环境科学与工程前沿（英文）》 2015年 第9卷 第1期   页码 171-179 doi: 10.1007/s11783-014-0750-1

摘要： Seasonal variability in source water can lead to challenges for drinking water providers related to operational optimization and process control in treatment facilities. The objective of this study is to investigate seasonal variability of water quality in municipal small water systems (<3000 residents) supplied by surface waters. Residual chlorine and trihalomethanes (THM) were measured over seven years (2003–2009). Comparisons are made within each system over time, as well as between systems according to the type of their treatment technologies. THM concentrations are generally higher in the summer and autumn. The seasonal variability was generally more pronounced in systems using chlorination plus additional treatment. Chloroform, total THM (TTHM) and residual chlorine concentrations were generally lower in systems using chlorination plus additional treatment. Conversely, brominated THM concentrations were higher in systems using additional treatment. Residual chlorine was highest in the winter and lowest in the spring and summer. Seasonal variations were most pronounced for residual chlorine in systems with additional treatment. There was generally poor correlation between THM concentrations and concentrations of residual chlorine. Further study with these data will be beneficial in finding determinants and indicators for both quantity and variability of disinfection byproducts and other water quality parameters.

关键词： drinking water     residual chlorine     seasonal variability     small municipal systems     treatment technologies     trihalomethanes    

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Quantifying and mapping spatial variability of Shanghai household carbon footprints

Shangguang YANG,Chunlan WANG,Kevin LO,Mark WANG,Lin LIU

《能源前沿（英文）》 2015年 第9卷 第1期   页码 115-124 doi: 10.1007/s11708-015-0348-8

摘要： Understanding the spatial variability of household carbon emissions is necessary for formulating sustainable and low-carbon energy policy. However, data on household carbon emissions is limited in China, the world’s largest greenhouse gases emitter. This study quantifies and maps household carbon emissions in Shanghai using a city-wide household survey. The findings reveal substantial spatial variability in household carbon emissions, especially in transport-related emissions. Low emission clusters are founded in Hongkou, Xuhui, Luwan, Jinshan, and Fengxian. High emission clusters are located in Jiading and Pudong. Overall, the spatial pattern of household carbon emissions in Shanghai is donut-shaped: lowest in the urban core, increasing in the surrounding suburban areas, and declining again in the urban fringe and rural regions. The household emissions are correlated with a number of housing and socioeconomic factors, including car ownership, type of dwelling, size of dwelling, age of dwelling, and income. The findings underscore the importance of a localized approach to low-carbon policy-making and implementation.

关键词： household carbon emissions     spatial variability     energy policy     Shanghai     China    

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Distribution and temporal variability of the solar resource at a site in south-east Norway

Muyiwa S. ADARAMOLA

《能源前沿（英文）》 2016年 第10卷 第4期   页码 375-381 doi: 10.1007/s11708-016-0426-6

摘要： Globally, solar energy is expected to play a significant role in the changing face of energy economies in the near future. However, the variability of this resource has been the main barrier for solar energy development in most locations around the world. This paper investigated the distribution and variability of solar radiation using the a 10-year (2006 to 2015) data collected at Sørås meteorological station located at latitude 59° 39′ N and longitude 10° 47′E, about 93.3 m above sea level (about 30 km from Oslo), in south-eastern part of Norway. It is found that on annual basis, the total number of days with a global solar radiation of less than 1 kWh/(m ·d) is 120 days while the total number of days with an expected global solar radiation greater than 3 kWh/(m ·d) is 156 days (42.74%) per year. The potential energy output from a horizontally placed solar collector in these 156 days is approximately 75% of the estimated annual energy output. In addition, it is found that the inter-annual coefficient of variation of the global solar radiation is 4.28%, while that of diffuse radiation is 4.96%.

关键词： coefficient of variation     global solar radiation     diffuse ratio     albedo     PV energy systems    

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Shallow foundation response variability due to soil and model parameter uncertainty

Prishati RAYCHOWDHURY,Sumit JINDAL

《结构与土木工程前沿（英文）》 2014年 第8卷 第3期   页码 237-251 doi: 10.1007/s11709-014-0242-1

摘要： Geotechnical uncertainties may play crucial role in response prediction of a structure with substantial soil-foundation-structure-interaction (SFSI) effects. Since the behavior of a soil-foundation system may significantly alter the response of the structure supported by it, and consequently several design decisions, it is extremely important to identify and characterize the relevant parameters. Moreover, the modeling approach and the parameters required for the modeling are also critically important for the response prediction. The present work intends to investigate the effect of soil and model parameter uncertainty on the response of shallow foundation-structure systems resting on dry dense sand. The SFSI is modeled using a beam-on-nonlinear-winkler-foundation (BNWF) concept, where soil beneath the foundation is assumed to be an assembly of discrete, nonlinear elements composed of springs, dashpots and gap elements. The sensitivity of both soil and model input parameters on shallow foundation responses are investigated using first-order second-moment (FOSM) analysis and Monte Carlo simulation through Latin hypercube sampling technique. It has been observed that the degree of accuracy in predicting the responses of the shallow foundation is highly sensitive soil parameters, such as friction angle, Poisson’s ratio and shear modulus, rather than model parameters, such as stiffness intensity ratio and spring spacing; indicating the importance of proper characterization of soil parameters for reliable soil-foundation response analysis.

关键词： shallow foun dation     sensitivity analysis     centrifuge data     first-order-second-moment (FOSM) method     parameter uncertainty    

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Quantification of emission variability for off-road equipment in China based on real-world measurements

《环境科学与工程前沿（英文）》 2022年 第16卷 第2期 doi: 10.1007/s11783-021-1455-x

摘要：

• Emissions from 53 in-use diesel-fueled off-road equipment were measured.

关键词： Off-road equipment     Portable emission measurement system (PEMS)     Real-world emissions     Diesel engine    

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Variability of waste copper slag concrete and its effect on the seismic safety of reinforced concrete

《结构与土木工程前沿（英文）》 2022年 第16卷 第1期   页码 117-130 doi: 10.1007/s11709-021-0788-7

摘要： Proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built environment. Although numerous studies on waste copper slag concrete can be found in the published literature, no research has focused on the structural application of this type of concrete. In particular, the variability in the strength properties of waste copper slag concrete, which is required for various structural applications, such as limit state design formulation, reliability-based structural analysis, etc., has so far not attracted the attention of researchers. This paper quantifies the uncertainty associated with the compressive-, flexural- and split tensile strength of hardened concrete with different dosages of waste copper slag as fine aggregate. Best-fit probability distribution models are proposed based on statistical analyses of strength data generated from laboratory experiments. In addition, the paper presents a reliability-based seismic risk assessment of a typical waste copper slag incorporated reinforced concrete framed building, considering the proposed distribution model. The results show that waste copper slag can be safely used for seismic resistant structures as it results in an identical probability of failure and dispersion in the drift demand when compared with a conventional concrete building made of natural sand.

关键词： waste copper slag     quantification of variability     goodness-of-fit test     seismic risk assessment     PSDM    

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The effect of texture and irrigation on the soil moisture vertical-temporal variability in an urban artificial

Xiaofeng ZHANG,Xu ZHANG,Guanghe LI

《环境科学与工程前沿（英文）》 2015年 第9卷 第2期   页码 269-278 doi: 10.1007/s11783-014-0672-y

摘要： Soil moisture variability in natural landscapes has been widely studied; however, less attention has been paid to its variability in the urban landscapes with respect to the possible influence of texture stratification and irrigation management. Therefore, a case study was carried out in the Beijing Olympic Forest Park to continuously monitor the soil in three typical profiles from 26 April to 11 November 2010. The texture stratification significantly affected the vertical distribution of moisture in the non-irrigated profile where moisture was mostly below field capacity. In the profile where irrigation was sufficient to maintain moisture above field capacity, gravity flow led to increased moisture with depth and thus eliminated the influence of texture. In the non-irrigated sites, the upper layer (above 80 cm) exhibited long-term moisture persistence with the time scale approximating the average rainfall interval. However, a coarse-textured layer weakened the influence of rainfall, and a fine-textured layer weakened the influence of evapotranspiration, both of which resulted in random noise-like moisture series in the deeper layers. At the irrigated site, frequent irrigation neutralized the influence of evapotranspiration in the upper layer (above 60 cm) and overshadowed the influence of rainfall in the deeper layer. As a result, the moisture level in the upper layer also behaved as a random noise-like series; whereas due to deep transpiration, the moisture of the deep layer had a persistence time-scale longer than a month, consistent with characteristic time-scales found for deep transpiration.

关键词： moisture vertical distribution     moisture temporal variation     texture stratification     irrigation     meteorological forcing     urban landscape    

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Combustion and emissions of RP-3 jet fuel and diesel fuel in a single-cylinder diesel engine

《能源前沿（英文）》 2023年 第17卷 第5期   页码 664-677 doi: 10.1007/s11708-021-0787-3

摘要： The combustion characteristics and emission behaviors of RP-3 jet fuel were studied and compared to commercial diesel fuel in a single-cylinder compression ignition (CI) engine. Engine operational parameters, including engine load (0.6, 0.7, and 0.8 MPa indicating the mean effective pressure (IMEP)), the exhaust gas recirculation (EGR) rate (0%, 10%, 20%, and 30%), and the fuel injection timing (−20, −15, −10, and −5 ° crank angle (CA) after top dead center (ATDC)) were adjusted to evaluate the engine performances of RP-3 jet fuel under changed operation conditions. In comparison to diesel fuel, RP-3 jet fuel shows a retarded heat release and lagged combustion phase, which is more obvious under heavy EGR rate conditions. In addition, the higher premixed combustion fraction of RP-3 jet fuel leads to a higher first-stage heat release peak than diesel fuel under all testing conditions. As a result, RP-3 jet fuel features a longer ignition delay (ID) time, a shorter combustion duration (CD), and an earlier CA50 than diesel fuel. The experimental results manifest that RP-3 jet fuel has a slightly lower indicated thermal efficiency (ITE) compared to diesel fuel, but the ITE difference becomes less noticeable under large EGR rate conditions. Compared with diesel fuel, the nitrogen oxides (NOx) emissions of RP-3 jet fuel are higher while its soot emissions are lower. The NOx emissions of RP-3 can be effectively reduced with the increased EGR rate and delayed injection timing.

关键词： RP-3 jet fuel     diesel     engine     combustion     emissions    

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Impacts of methanol fuel on vehicular emissions: A review

《环境科学与工程前沿（英文）》 2022年 第16卷 第9期 doi: 10.1007/s11783-022-1553-4

摘要：

● Methanol effectively reduces CO, HC, CO2, PM, and PN emissions of gasoline vehicles.

关键词： Methanol fuel     Vehicular emission     Emission reduction     Cleaner fuel     Gasoline substitute    

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极区海洋碳池变化性和脆弱性及其探测工程技术

陈立奇

《中国工程科学》 2009年 第11卷 第10期   页码 79-85

摘要：

利用中国南极考察和北极科学考察在南大洋和西北冰洋开展的连续围绕大气和表层海水pCO2及其相关参数观测和海气CO2通量评估，阐述南大洋和西北冰洋碳池的年际变化性，分析探讨其脆弱性，并展望了极区海洋碳池探测工程技术。

关键词： 碳循环     变化性和脆弱性     南大洋     西北冰洋     探测工程技术    

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Failure mode investigation of fuel cell for vehicle application

Zhongjun HOU, Renfang WANG, Keyong WANG, Weiyu SHI, Danming XING, Hongchun JIANG

《能源前沿（英文）》 2017年 第11卷 第3期   页码 318-325 doi: 10.1007/s11708-017-0488-0

摘要： The durability of proton exchange membrane fuel cells (PEMFCs) has been posing a key technical challenge to commercial spread of fuel cell vehicles (FCVs). To improve the durability, it is necessary to optimize the fuel cell system (FCS) design against failure modes. The fuel cell durability research method at FCS scale was exhibited, and the failure modes of fuel cell were experimentally investigated in this paper. It is found that the fuel cell dry operation, start/stop cycle and gas diffusion layer (GDL) flooding are typical failure modes of fuel cells. After the modifications against the failure modes, the durability of FCSs is improved to over 3000 h step by step.

关键词： proton exchange membrane fuel cell (PEMFC)     fuel cell system (FCS)     durability     failure mode     fuel cell vehicle (FCV)     carbon corrosion     water management    

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Numerical investigation of the effects of fuel spray type on the interaction of fuel spray and hot porous

ZHAO Zhiguo, XIE Maozhao

《能源前沿（英文）》 2008年 第2卷 第1期   页码 59-65 doi: 10.1007/s11708-008-0022-5

摘要： The interaction between two types of fuel spray and a hot porous medium is studied numerically by using an improved version of KIVA-3V code. The improved KIVA-3V code is incorporated with an impingement model, a heat transfer model and a linearized instability sheet atomization (LISA) model to model the hollow cone spray. An evaporating fuel spray impingement on a hot plane surface was simulated under conditions of experiments performed by Senda to validate the reasonability of the KIVA-3V code. The numerical results conform well with experimental data for spray radius in the liquid and the vapor phases. Computational results on the interaction of two types of the fuel spray and the hot porous medium show that the fuel spray can be split, which provides conditions for quick evaporation of fuel droplets and mixing of fuel vapor with air. The possibility of fuel droplets from hollow cone spray crossing the porous medium reduces compared with that from solid cone spray, with the same initial kinetic energy of fuel droplets in both injection types.

关键词： improved version     impingement     atomization     hollow     radius    

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Recent advances in cathode electrocatalysts for PEM fuel cells

Junliang ZHANG

《能源前沿（英文）》 2011年 第5卷 第2期   页码 137-148 doi: 10.1007/s11708-011-0153-y

摘要： Great progress has been made in the past two decades in the development of the electrocatalysts for proton exchange membrane fuel cells (PEMFCs). This review article is focused on recent advances made in the kinetic-activity improvement on platinum- (Pt-) based cathode electrocatalysts for the oxygen reduction reaction (ORR). The origin of the limited ORR activity of Pt catalysts is discussed, followed by a review on the development of Pt alloy catalysts, Pt monolayer catalysts, and shape- and facet-controlled Pt-alloy nanocrystal catalysts. Mechanistic understanding is reviewed as well on the factors contributing to the enhanced ORR activity of these catalysts. Finally, future directions for PEMFC catalyst research are proposed.

关键词： proton exchange membrane fuel cells (PEMFCs)     cathode electrocatalysts     platinum     oxygen reduction reaction (ORR)    

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标题 作者 时间 类型 操作

Fuel variability effect on flickering frequency of diffusion flames

Jizhao LI, Yang ZHANG

期刊论文

Soil spatial variability impact on the behavior of a reinforced earth wall

Adam HAMROUNI, Daniel DIAS, Badreddine SBARTAI

期刊论文

Treatment, residual chlorine and season as factors affecting variability of trihalomethanes in small

Roberta DYCK,Geneviève COOL,Manuel RODRIGUEZ,Rehan SADIQ

期刊论文

Quantifying and mapping spatial variability of Shanghai household carbon footprints

Shangguang YANG,Chunlan WANG,Kevin LO,Mark WANG,Lin LIU

期刊论文

Distribution and temporal variability of the solar resource at a site in south-east Norway

Muyiwa S. ADARAMOLA

期刊论文

Shallow foundation response variability due to soil and model parameter uncertainty

Prishati RAYCHOWDHURY,Sumit JINDAL

期刊论文

Quantification of emission variability for off-road equipment in China based on real-world measurements

期刊论文

Variability of waste copper slag concrete and its effect on the seismic safety of reinforced concrete

期刊论文

The effect of texture and irrigation on the soil moisture vertical-temporal variability in an urban artificial

Xiaofeng ZHANG,Xu ZHANG,Guanghe LI

期刊论文

Combustion and emissions of RP-3 jet fuel and diesel fuel in a single-cylinder diesel engine

期刊论文

Impacts of methanol fuel on vehicular emissions: A review

期刊论文

极区海洋碳池变化性和脆弱性及其探测工程技术

陈立奇

期刊论文

Failure mode investigation of fuel cell for vehicle application

Zhongjun HOU, Renfang WANG, Keyong WANG, Weiyu SHI, Danming XING, Hongchun JIANG

期刊论文

Numerical investigation of the effects of fuel spray type on the interaction of fuel spray and hot porous

ZHAO Zhiguo, XIE Maozhao

期刊论文

Recent advances in cathode electrocatalysts for PEM fuel cells

Junliang ZHANG

期刊论文