将扩压管内有摩阻的稳定流动转化为等效多变过程进行研究,得到了揭示摩擦影响工质状态变化规律的解析表达式.研究发现,有摩阻时扩压管的喉部不是临界截面,而是壅塞截面且马赫数Mc＞1.壅塞截面的马赫数、温度比和压力比都与物性和摩擦有关,扩压管截面积如何变化应根据壅塞参数决定.导出了壅塞马赫数、壅塞温度比和壅塞压力比的计算公式,有效解决了扩压管喉部相关参数计算的关键问题.

The fault current is small when a single-phase earth fault occurs in distribution network, so it is still difficult to diagnose the faults accurately. To improve the identification accuracy of single-phase earth faults in distribution network, a fault pattern and convolutional neural network (CNN) based identification method is proposed in this paper. Firstly, this paper extracts the features of different fault types, and a classifier is constructed to identify the single-phase earth fault with low resistance fault and other faults. Then, the Hilbert-Huang transform (HHT) is used to transform the features of special faults from the time-domain to the frequency domain information. Finally, a CNN based classifier is proposed to distinguish the single-phase earth faults with high fault resistance and intermittent characteristics. To investigate the performance of the proposed identification method, simulations of a distribution grid case are carried out in MATLAB. Compared with artificial neural network (ANN) and k-nearest neighbor (KNN), the simulation results demonstrate that the proposed method can achieve higher accuracy on single-phase earth faults.

Regional cooperative production system based on the gas engine,the operation time of cooling,heating and electricity and loading status are always changing and the working condition of operation is complicated.Therefore,to ensure the effective operation of energy station,it is necessary that carrying out real-time supervision on the running status of energy station,allocating load appropriately for each refrigerating unit,reducing the energy consumption of unit and improving the running economy of the unit.In the paper,we proposed a method of modeling and simulation on the lithium-bromide absorption-type refrigerating machine and compression-type refrigerating machine respectively.The variable working condition of main equipment was analyzed under different loading and environment conditions.Besides,we took the refrigeration cost of the energy station as the optimized objective function,produced the optimal loading of economy when the external conditions and cold loading keeps unchanged.An off-line calculation method was adopted to generate the data documents of the optimized running model in the configuration platform;the running optimization model can calculate the refrigerating capacity of the lithium bromide refrigerant unit and the centrifugal refrigerant unit respectively through fitted equation.

To study the frictional steady flow in nozzle,this kind of flow is transformed to equivalently reversible polytropic process.By this means,the studying result reveals that how friction influences states of working medium.According to our study,the throttle section in nozzle is choke section but critical section and Mach number in choke section is less than 1.The greater the friction is,the smaller the Mach number of choke section is.It is friction that makes Mach number in choke section be less than one and critical section move to the downstream.The greater the friction is,the greater the distance between choke section and critical section is.Choosing convergent nozzle or Laval nozzle depends on choke pressure ratio but critical pressure ratio.Choke pressure ratio is related to characteristics of working medium and frictional dissipation.Calculating formulas about choke Mach number,choke temperature ratio and choke pressure ratio are derived and a vital problem of calculating related parameters of the minimum section in nozzle resolved effectively.

在燃气轮机的区域型联产系统中,由于调节模式和燃料电力价格标准的不统一,使得实际运行会造成大量浪费。为此选型GE LM1600燃气轮机,配备相应的溴化锂吸收式冷暖机和压缩式电制冷机,组成一个区域型能源站,通过建模仿真,分析主要设备的变工况特性,以系统每小时的经济花费为优化目标函数,计算出在不同调节模式和不同燃料电力价格比下的费用特性曲线。结果表明燃料电力价格比是影响系统运行经济性的关键参数,系统调节模式的选择应根据当时的燃料电力价格比作为参考依据。

研究不补燃三压再热式联合循环机组的热力性能优化问题。联合循环的热力性能计算的变量很多,常规的仿真方法对很多参数及过程进行简化处理,使得热力性能仿真的结果不精确且无通用性。提出用LabVIEW组态平台,结合变比热方法,冷却空气的处理等途径,对热力过程及各个部件建立数值分析模型,实现对燃料成分、大气温度、燃气压比参数等对联合循环机组发电效率、发电功率的影响的比对分析。结果表明,在LabVIEW平台上建立的仿真模型符合工程要求,为优化势力系统性能提供了参考。

To support context-aware mobile recommendation, an ontology-based context modeling approach was proposed. We analyzed the framework of the mobile recommender system based on contextual model and suggested designing the model with two-layer structure including an upper ontology layer and a domain ontology layer. The ontologies provides formalizations representing the main entities, including users, objects, contexts, and their interactive relationships in mobile recommendation environments. A specific context ontology model for catering recommendation was developed and a use case of the instantiated context ontology was demonstrated.

A comprehensive overview of the status of lignite predrying technology is given in this study. The practical problems of high energy consumption, high investment and poor safety exist in the lignite drying using the traditional thermal drying, for the reason that the superheated steam drying technology for lignite is put forward. The mechanism experiment research and pilot-scale test research of the super-heated steam drying technology for lignite were carried out, and the results show that the drying efficiency of the super-heated steam is better than the hot air at given conditions, the lignite drying can be accomplished stably and continuously and the drying product can meet the requirement of the industrial application of the lignite fired power plant. A more innovative approach as a new lignite Super-heated steam low-rank Coal Upgrading (SCU) is proposed by Energy Conservation Research Center of Shandong Academy of Sciences. The technical advancement in terms of energysaving and safety among the applied technologies are compared and analyzed, and the results show this technology has the advantages of low energy consumption, high safety and energy saving. To sum up, the exploitation of the super-heated steam drying technology for lignite fired power plant can promote the development of the energy and power industry, and the technology has wide application prospect.

Drying characteristics of sewage sludge were investigated using hot air of a temperature range of 50~80degC and an air velocity range of 0.60~1.48 m/s at a laboratory scale dryer. Several mathematical models available in the literatures were fitted to the experimental data by multiple nonlinear regression analysis. Four statistical parameters: coefficient of determination (R2), reduced chi-square (chi2), root mean square error (RMSE) and mean relative deviation modulus (P) were used to evaluate the fitting of these models to experimental data. The Page model gave the better predictions than others. Then a modified model based on Page model was developed and the new model could fit the drying characteristics of sewage sludge well with R2 over 0.9993 at widely drying conditions.

Objective: To compare the apical sealing ability of different Zinc Oxide-Eugenol(ZOE) based sealers with Ah-Plus sealers.Methods: Sixty premolars with one root canal extracted for orthodontic therapy were divided as follows: number 1,2,3,4 ZOE sealers,Pulp canal sealers,Endomethasone ivory sealers,Ah-Plus sealers,positive group and negative group.Each tooth was obturated with cold lateral condensation.After dyeing in India ink,the extent of apical dye penetration was measured with a stereomicroscope.Results: No statistical differences were observed among these seven groups,but the microleakge of Endomethasone ivory sealers were significantly lager than that of Ah-Plus sealers.Conclusion: In the present experimental conditions,the developed ZOE based root canal sealers have the same apical sealing ability as several other sealers.

In order to improve the economy of thermal power unit cold-end system, considering variable performance of condenser, circulating water pump, variable frequency speed regulation, and driving motor, it is proposed to establish a cold-end optimization model for 600MW super-critical unit based on SIS. The technology of offline calculation, online interpolation is applied to develop the operating optimization software of cold-end, which can reduce computer’s calculating process greatly and is of good stability, real-time performance and practical value.

Using different governing modes in the process of large steam turbine load variations will make the thermal characteristic and force of unit get complicated, especially affect the thermal characteristic and force change of the control stage notability the most. This article researched the governing mode problems of the domestic-type 600 MW steam turbine, analyzed different characteristics in different governing modes of control valve, calculated the control stage blade force in different loads and governing modes, and the blade force variations on the main steam pressure change in the same load, based on large amount of field test data. By calculating and analyzing, we found that, the blade force of sequential valve governing mode is significantly higher than the single valve governing mode in domestic-type 600 MW steam turbine. For the same load, the higher the main steam pressure, the smaller the main steam flow, the greater control stage blade force is. Therefore, in the process of unit actual operation, it should try to avoid the risk of working conditions of control stage blade stress in order to ensure the safety of unit operation when the governing modes are switching or the control valve opening is changing to regulate the load.

Objective: To evaluate the efficacy of two rotary retreatment systems and hand stainless instruments for gutta-percha removal in oval-shaped root canals.Methods: Fourty-five mandibular second premolars with single oval-shaped root canal were prepared with step-back technique and filled with warm vertical compaction technique.The teeth were divided into three groups randomly: ProTaper group,Mtwo group and manual stainless group.The operating time was recorded.Digital subtraction technique and image-proplus 5.0 software were used to measure the percentage of residual filling material.Results: The manual instrumentation resulted in a smaller percentage of residual filling material than other groups,but the mean operating time was significantly longer than other groups.Conclusion: NiTi instrument reduced the operating time,but left more residual filling material within oval shaped root canals.

A newly-designed spot inspection device is developed to meet the higher demand of spot inspection in the electric power enterprises. Both the software and hardware structures of the device are presented, especially the method of infrared temperature measurement and vibration measurement. The spot inspection device is portable, fast, easy to operate, and integrated with data management and temperature and vibration measurement functions. This device will effectively improve the efficiency of spot inspection.

X-ray photoelectron spectroscopy was used to investigate the characteristics and evolution of sulfur (S) in mixtures of bituminous coal and sewage sludge (SS) and their chars during isothermal combustion. Five groups of mixtures with SS content of 0%, 10%, 20%, 30% and 100%, were examined at different burn-off ratios (β) of 0, 30%, 50%, 70% and 100%. The S in the coal mainly exist as the forms of mercaptan (S1), sulfide (S2), thiophene (S3), sulfoxide (S4), sulfone (S5) and sulfate (S6). During the coal combustion process, the content of S1 and S2 decreased, while that of S3 and S5 increased in the early stage and decreased in the late stage. The S4 content increased throughout the entire process of combustion. Small amount of S6 was detected, showing a fluctuated pattern. The trend of S1, S2, S5 and S6 in SS was alike with that in coal, whereas S4 decreased at the end of combustion. The changing process of S3 in SS was opposite to that of coal, while the composition of S in the mixtures resulted from the mixing of coal and SS. The transformation of each functional group during co-combustion were correlated with their transformation characteristics during the mono-combustion of coal and SS, and no obvious interaction was observed, which demonstrated that the coal-origin and SS-origin sulfur in mixtures kept their own characteristics in the combustion. SS may accumulate on the solid surface as α increase, resulting its significant influence on the evolution of each form of S. When α was low, most of the S-contained functional groups presented the characteristics of coal. The percentage of coal-origin functional groups declined as α increased. The transforming trends of most functional groups were similar with that of SS when α reached 30%.

The combustion reaction kinetics of two Chinese straws were investigated by a differential thermal balance , volume fraction of reactive gas was N2: O2 = 80:20 and heating rate was 30degC/min. Reaction of samples were mainly composed volatile and fixed carbon combustion phase, ranges of them were 425 K - 650 K and 650 K - 810 K in round numbers according to TG, DTG and DTA curves. Reaction kinetic parameters were calculated with Coats-Redfern method. Ranges of activation energy in volatile combustion phase were 20 kJ.min -1 or so, fixed carbon combustion phase were different, they were 145 kJ.min -1 and 66 kJ.min -1 . Results showed that the order of reaction of volatile combustion phase and fixed carbon combustion phase were zero and second, respectively. The reaction initial temperatures of two samples ranged from 420 K - 460 K and reaction final temperatures ranged from 780 K - 810 K.

X-ray photoelectron spectroscopy was used to investigate the evolution of oxygen functionalities in blends formed with bituminous and dry sewage sludge during their co-combustion.Five groups blends with different sewage sludge mass ratio were examined,sewage sludge mass ratio was 0,10%,20%,30% and 100%.Char sample with different burn off radio were obtain with a tube furnace reactor,burn off radio of the char sample were 0,30%,50%,70% and 100%.Oxygen functionalities of the samples were studied by using XPS method.Results indicate that content of inorganic oxygen increases while hydroxyl decreases during combustion,the carbonyl content shows a fluctuated pattern,the carboxyl content increases in the early stage and decreases in the terminal stage.These four oxygen functionalities are also detected in sewage sludge,and their transformation is similar with that in bituminous.Oxygen functionalities in coal and sewage sludge keep their own characteristics during co-combustion.Obvious interaction wasn't observed during co-combustion of sewage sludge and coal.

The spot inspection management is a scientific means of equipment management. The spot inspection information management system provides a necessary platform for spot inspection. This paper introduces the construction of the information management system , and it summarizes the functions of the spot inspecting apparatus from four dimensions, then it focuses on the function design of every module in the software, finally it introduces the new functions of the systems.

On the basis of knowing the maintenace items and basic maintenance technological process of thermal pewer equipments in power plants,taking the realization of planned arrangement in maintenance as the purpose,a maintenance management framwork,in which corresponding automatic ajustment can be made according to the variation of actual progress schedule in the project,has been put forward,and the key algorithms in management process of the progress schedule being thoroughly analysed and studied.Finally,taking Visual C++6.0 as basic development means,and comprehensively using design methods,such as data-base,and systematic fundamental class bank etc.,a maintenance management system of the steam turbine has been developed.

The protection device is the assurance for High Temperature Superconducting (HTS) cable's safe operation in power grid. The paper introduces a protection device for HTS cable, which provides both functions of protection and monitoring. In this paper, hardware structure of the protection device and the protection scheme are presented, then a thermal balance model of HTS cable on quench is proposed, with which the over-current limit value and thermal accumulation limit value of HTS cable are determined. In order to study the characteristics of HTS cable system and accumulate commercial operation experience of HTS cable system, the device also offers operation-state record of HTS cable, including all the non-electric signals and electric signals. The data on operation shows that the protection device runs well.