值班燃料比对环管型燃烧室内NO_x生成特性影响

采用数值模拟对环管型燃烧室内NO_x生成规律进行了研究。通过改变值班燃料比获得燃烧室内流场、温度场以及热力型NO_x生成速率的分布。结果表明:随着值班燃料比的增大,中心轴线附近轴向速度有所上升,其他区域速度变化不大;值班火焰温度上升,中心轴线附近高温区范围扩大,高温明显促进了热力型NO_x的生成,其高速率范围基本与高温区重合。因此,在值班燃料比为4.0%~5.5%时,减小值班燃料比有利于降低出口NO_x排放质量浓度。

环管型燃烧室喷雾燃烧DES模拟

为研究燃气轮机燃烧室内复杂的两相三维湍流燃烧问题,采用基于Realizable k-ε模型的分离涡模拟(DES)方法对环管型燃烧室进行喷雾燃烧数值模拟。数值模拟结果表明:DES模拟在燃烧区发挥出大涡模拟(LES)的作用,能获取结构复杂的流场、温度场和涡量场,其对流场内涡结构的捕捉和分辨能力明显强于传统的RANS(雷诺时均N-S方法)模拟。与实验数据对比发现,DES模拟所得燃烧产物含量和燃烧室出口温度分布更符合。因此,DES方法可用于复杂形状燃烧室的燃烧数值模拟,能够避免RANS模型对湍流脉动进行平均处理导致耗散过大、抹平涡结构的缺点,从而可获取更准确的计算结果。

环管型燃烧室横截面积变化对燃烧及NO_x生成的影响

采用数值模拟方法研究了环管型燃烧室横截面积变化对燃烧室燃烧、流动及燃烧室NO_x生成及排放的影响规律。分析表明:在环管型燃烧室主喷嘴出口形成主回流区,凸台区域形成外部回流区,外部回流区范围较小;随着横截面积增大,主回流区范围增大,温度峰值和高温区范围均有所减小;增大横截面积使得比面积热强度随之减小,燃烧室内温度水平逐渐下降,热力型NO_x生成速率降低,燃烧室出口NO_x排放量下降。

环管型燃烧室火焰筒壁温气热耦合数值模拟

针对某型燃气轮机运行时回流式环管型燃烧室的火焰筒常发生烧蚀和裂纹,需获取其火焰筒壁温分布特点,进行分析以提出改进措施.全面考虑固体导热和辐射传热、气体与固体间的对流换热以及火焰和燃气的辐射,对燃烧室进行三维气热耦合数值模拟计算,获取流场、温度场以及壁温分布信息,并结合实验验证了三维气热耦合数值模拟能够较有效预测火焰筒壁温分布.由模拟结果知该型火焰筒壁温未超过设计值1 223K,但在联焰管与筒体连接处以及多个主燃孔处的温度较高、温度梯度较大,需要对这些部位的冷却方案进行改进.

当量比对环管型燃烧室内NO_x生成特性影响的研究

采用数值模拟方法研究了当量比对环管型燃烧室内燃烧及NOx生成特性的影响,分析了不同当量比时燃烧室内流场、温度场、热力型NOx生成速率分布、出口温度分布系数（OTDF）及出口NOx浓度的变化。模拟过程中,保持空气量不变,通过调整入口甲烷量来改变当量比。研究表明：增大当量比,燃烧室内燃烧反应速率加快,轴向速度升高,高温区域沿径向扩张,其范围明显扩大,热力型NOx生成速率加快,其高速率范围与高温区域重合,出口NOx浓度上升,而OTDF始终处于合理范围内。因此,在当量比为0.48-0.54范围内,适当降低当量比有利于控制出口NOx浓度。

U型环管反应器吊装防失稳施工技术探讨

U型环管反应器结构长细比达55:1,且结构中具有多处薄壁型膨胀节,单片吊装过程中极易产生柔性挠曲变形,吊装风险较大,因此采取合理的吊装防失稳措施尤为关键。本文结合金能化学45万吨/年高性能聚丙烯装置PPⅡ项目中2台环管反应器吊装施工,详细介绍了其防失稳吊装的施工方法,对类似工程项目具有一定参考价值。

旋流数对某环管型燃烧室内燃烧及NO_x生成特性的影响

采用数值模拟的方法对主喷嘴不同旋流数下某重型燃气轮机环管型燃烧室内流场、温度场和热力型NO_x生成规律进行分析。结果表明:燃烧室内主喷嘴出口形成主回流区,根部贴近壁面处形成外部回流区;值班喷嘴出口处形成中心回流区;值班喷嘴出口扩散火焰区域与外部回流区温度较高,热力型NO_x生成速率明显加快;旋流数增大,主回流区范围增大,外部回流区范围减小,中心回流区消失;燃烧峰值温度略有降低,高温区范围明显减小,热力型NO_x生成速率降低;适当增大主喷嘴旋流数有利于控制NO_x排放。

Meta-analysis and systematic review of colorectal endoscopic mucosal resection

AIM:To evaluate the proportion of successful complete cure en-bloc resections of large colorectal polyps achieved by endoscopic mucosal resection(EMR). METHODS:Studies using the EMR technique to resect large colorectal polyps were selected.Successful complete cure en-bloc resection was defined as one piece margin-free polyp resection.Articles were searched for in Medline,Pubmed,and the Cochrane Control Trial Registry,among other sources. RESULTS:An initial search identified 2620 reference articles,from which 429 relevant articles were selected and reviewed.Data was extracted from 25 studies(n =5221)which met the inclusion criteria.All the studies used snares to perform EMR.Pooled proportion of en-bloc resections using a random effect model was 62.85%(95%CI:51.50-73.52).The pooled proportion for complete cure en-bloc resections using a random effect model was 58.66%(95%CI:47.14-69.71).With higher patient load(>200 patients),this complete cure en-bloc resection rate improves from 44.19%(95%CI: 24.31-65.09)to 69.17%(95%CI:51.11-84.61). CONCLUSION:EMR is an effective technique for the resection of large colorectal polyps and offers an alternative to surgery.

Experimental investigation on flow properties of cemented paste backfill through L-pipe and loop-pipe tests

With the gradual depletion of available ore at shallow depth,deep mines have been widely operated around the world and therefore need a longer distance to transport the backfill to the underground stope.In this case,the determination of pressure drop is more important in the pipeline transportation system design.As the pilot loop systems require a large amount of capital and manual investment,even its results are reliable,there is an urgent need to find an alternative simple and cost-saving method to determine the pressure drop.Hence,laboratory L-pipe and a pilot-loop tests were employed to study the flow properties of cemented paste backfill cured at various solid and binder content.The results indicate that the L-pipe test presented a similar trend to the loop test,but the L-pipe was characterized by higher pressure drop values for various solid and cement contents.As cement content increased beyond 0%,the paste in the L-pipe showed a slighter difference in pressure drop evolution compared to the paste in the loop-pipe.These results suggest that the simple L-pipe is a workable substitute for semi-industrial loop tests and can provide guidance for designing practical CPB pipeline systems in deep mines.

Numerical method and model for calculating thermal storage time for an annular tube with phase change material

For calculating the thermal storage time for an annular tube with phase change material （PCM）, a novel method is proposed. The method is suitable for either low-temperature PCM or high-temperature PCM whose initial temperature is near the melting point. The deviation fit is smaller than 8% when the time is below 2x104 s. Comparison between the predictions and the reported experimental data of thermal storage time at same conditions is investigated and good agreements have been got. Based on this method, the performance of the thermal storage unit and the role of natural convection are also investigated. Results show a linear relation between the maximum amount of stored heat and thermal storage time, and their ratio increases with the height of the thermal storage unit. As the thickness of the cavity increases, natural convection plays an increasingly important role in promoting the melting behavior of paraffin. When the thickness of the cavity is small, natural convection restrains the melting behavior of paraffin.

Application of a Neural Network Technique for Prediction of the Water Quality Index in the Dong Nai River, Vietnam

Recent trends in environmental management of water resource have enlarged the demand for predicting techniques that can provide reliable, efficient and accurate water quality. In this case study, the authors applied the Artificial Neural Networks （ANN） to estimate the water quality index on the Dong Nai River flowing through Dong Nai and Binh Duong provinces. The information and data including 10 water quality parameters of the Dong Nai River at 23 monitoring stations were collected during the recorded time period from 2010 to 2014 to build water quality prediction models. The results of the study demonstrated that the Water Quality Index （WQI） forecasted with GRNN was very significant and had high correlation coefficient （R2 = 0.974 and p = 0.0） compared to the real values of the WQI. Moreover, the ANN models provided better predicted values than the multiple regression models did.

A Framework of Environmental Modelling and Information Sharing for Urban Air Pollution Control and Management

More effective environmental pollution control and management are needed due to the increasing environ-mental impacts from a range of human activities and the growing public demands for a better living environment. Urban air pollution is a serious environmental issue that poses adverse impacts on the health of people and the environment in most metropolitan areas. In this paper,we propose a geoinformatics augmented framework of environmental modelling and information sharing for supporting effective urban air pollution control and management. This framework is out-lined in terms of its key components and processes including: 1) an integrated,adaptive network of sensors for envi-ronmental monitoring; 2) a set of distributed,interoperable databases for data management; 3) a set of intelligent,robust algorithms and models for environmental modelling; 4) a set of flexible,efficient user interfaces for data access and in-formation sharing; and 5) a reliable,high capacity,high performance computing and communication infrastructure for integrating and supporting other framework components and processes.

Eco-budget-A Model of Urban Environmental Management

In this paper, a new model of urban environmental resource management is introduced. The article analyzes the gap between urban environmental management and the management of economy and human resources. The significance, the key points, the implementation procedures, and steps of eco-budget cycle are discussed.

The Experience of Setting up a New Learning Environment Model in Management Education： Challenges and Frustrations

The aim of this paper is to describe and to reflect on the experience of the authors in setting up a new model of learning environment in management education in a University in Brazil, which was initially called Management Practice Laboratory （MPL）. The MPL environment was conceived as a physical and conceptual space where students could learn and practice the principles and techniques of working in organizations in its three levels operational, tactical, and strategic. The foundations of the project come from social constructivist perspective on learning, from experiential learning literature and from researches that call for a new epistemological ground in management learning. In this paper, the authors will stress some challenges and frustrations with the project since these could be helpful to those interested in similar initiatives. Due to limited space, only two challenges will be stressed： （1） the construction of legitimacy for the project; and （2） the persistent dissonance between theory and practice. The authors conclude that there is room for innovation in the way management is taught and learned in universities since one shows courage to overcome the challenges and frustrations one will certainly deal with

The Impact of Large-Scale Reclamation on Hydro-Dynamic Environment--A Case Study of Xinghua Bay

A hydro-dynamic model is established on basis of MIKE21 FM to simulate the hydro-dynamic characteristics of Xinghua Bay and investigate the influence of reclamation project on the tidal elevation and tidal currents. Tidal elevation data was obtained at the six tide gauge stations around the Xinghua Bay, and another six current stations were established to observe the tidal current velocity and direction. Validation shows that the model-simulated tidal elevation and tidal currents agree well with observations made at different stations. Predictions are made according to the reclamation project proposed in the regional marine planning of Hanjiang Industrial Park around the port in Putian City. The variations of hydro-dynamic factors, such as tide, current velocity and direction and tidal influx are obtained, and the adverse effect of reclamation on marine environment is discussed. It is shown that the tidal level inside the Xinghua Bay during high tide decreases after the reclamation project is completed. The tidal currents during flooding tide generally decrease in the southeast of the reclamation region, with the maximum decreasing amplitude reaching 0.44 m s^(-1). On the other hand, the tidal currents during flooding tide increase around the southeast and southwest corners of the reclamation region. The tidal currents during ebb tide increase around the southeast and southwest corners of the reclamation region, with the maximum increasing amplitude attaining 0.18 m s^(-1). The results in this paper can give some guidance for the marine environment management and the effective utilization of land in Putian.

Empirical research on drive mechanism of firms' environmental management

Firms’transformation from passive envrionmental management to active environmental management is thekey to solving environmental problems. This paper empirically studies the impact of environmental management incen-tives on environmental management through model construction. Based on the data and reality of China, we can build aconcept model of environmental management driving mechanism, and put forward theoretical hypothesis that can betested: take the 13 environmental management behaviors (EMBs) as substitute of the comprehensiveness, introducecounting variables, and use NB model, Possion Model and Ordered Probit model the regression analysis. The theory andmethods brought forward in this paper will provide references for firms in China to further implement voluntaryenvironmental management, and offer advises and countermeasures for leaders to implement environmental manage-ment effectively.

Heat Transfer and Flow Analysis in Loop Heat Pipe with Multiple Evaporators Using Network Model

Thermal performance of a loop heat pipe with two evaporators and two condensers was examined using a lumped network model analysis. Thermosyphon-type vertical loop heat pipe and capillary-pump-type horizontal loop heat pipe were calculated by examining the change of heating rate of two evaporators. Calculation results showed that the vapor and liquid flow rates in the loop heat pipe and the thermal conductance of the heat pipe changed significantly depending on the distribution ratio of the heating rate of the multiple evaporators. The thermal performance of the vertical loop heat pipe with two evaporators was also examined and experimental results of flow direction and thermal conductance of the heat pipe agreed with the analytical results. The lumped network model analysis is therefore considered accurate and preferable for the practical design of a loop heat pipe with multiple evaporators.

Fundamental Study of a Loop-Tube-Type Thermoacoustic Heating System

This paper proposes a loop-tube type thermoacoustic heating system without any moving parts based on the thermoacoustic effect. In a thermoacoustic heating system, the supplied sound is converted to heat and the heating point is heated. A thermoacoustic heating system differs from a thermoacoustic cooling system： The location of the reference temperature section at the heat pump is upside down. The authors construct a prototype ofthermoacoustic heating system. The experimental results show that the heating point reaches 100 ~C. It must be emphasized that, using this simple and inexpensive thermoacoustic heating system, noise, waste heat and unused heat are useful as a renewable energy source.

Comparison of Different Solutions for Blocking Diode Applications in a Photovoltaic Panel under Varying Ambient Conditions

We characterized a crystalline silicon based mini-module under varying ambient conditions, developed a PSPICE model for this panel, including temperature and irradiation dependence and applied this model to the simulation of the impact of a blocking diode under different shadowing conditions. Different blocking diodes were examined, like germanium and silicon homojunction diodes and silicon Schottky diodes and compared to ＂intelligent＂ diodes, consisting of operational amplifiers with MOSFET switches. The simulations indicate a strongly reduced power loss in a panel integrating the new ＂intelligent＂ blocking diodes even when compared to silicon Schottky diodes, as the best performing traditional blocking diodes.

Key technologies of precision demolition blasting of ultra-long urban viaduct in complicated surroundings

The key technologies of precision blasting were put forward based on the characteristics of urban via- duct blasting demolition in complicated surroundings. Initial bending instability mechanics model of reinforcing steel bar frame of blasting fragmented pier and sequenced collapsed dynamic model were established for quanti- tative blasting design. Technologies of water pressure blasting were applied in multi-cell box girder fragmenta- tion. The detonating network of non-electric duplication crossover was adopted for the safety and reliability of ultra-long delay. The rationality of blasting scheme and parameters were validated by physical model test. Harm- ful effects were forecasted and controlled by integrated protective technologies. Specialization, cooperation, pre- cision, execution （SCPE） project management method was put forward for precision management. The key tech- nologies of precision demolition blasting can provide reference for similar proiects.