超临界二氧化碳布雷顿循环与铅冷快堆的结合被认为是最为理想的动力循环之一,系统通过中间换热器传递热量,其性能影响着整个发电系统的高效与安全运行.由于超临界二氧化碳和液态铅铋合金(LBE)物理性质和热输运性质差异显著,对称式结构无法匹配两侧工质的换热要求,构建了1种非对称式紧凑式耦合换热器,采用数值模拟方法研究了超临界二氧化碳与液态铅铋合金耦合换热特性.结果表明:提升冷侧流体入口速度会显著增强换热;增加热侧LBE入口速度时,总换热系数先降低后增加;提升换热器冷热流体入口温度,换热器的换热系数先减小后增大,存在最优值;在拟临界区内,强浮力作用会大幅提升冷侧换热,而加速效应则抑制换热.
为加快实现"碳达峰"和"碳中和"目标,国家、地方及行业陆续出台了一系列关于温室气体控制的法律、法规及制度文件.氧化亚氮(N2O)作为一种具有较强温室效应的气体,引起越来越多研究者的重视.总结了国内外N2O研究现状,对比了典型燃煤锅炉N2O排放情况,分析了燃烧过程中N2O的生成机理、影响因素、抑制方法及脱除手段,探讨了燃煤锅炉的N2O减排策略,指出在加强燃煤锅炉N2O相关标准的制订、新技术研发及示范应用工作的同时,还需要对 N2O 的影响因素如加压富氧条件、煤质自身含水率等加深研究,进一步完善抑制与脱除办法.
燃煤循环流化床(CFB)锅炉对污泥进行混燃是一种有效处置污水污泥的方法.在适当的污泥掺烧比例下,污泥与煤混燃不会对电厂生产造成显著不利影响,并且可以使污泥的热值得到合理利用.综述了燃煤CFB锅炉混燃污泥的研究与应用进展,包括煤与污泥混燃过程中污染物的排放和控制、锅炉可靠运行的掺烧比例和污泥干化等情况.分析了混燃湿污泥所带来的运行问题,介绍了采用水煤浆悬浮燃烧技术及富氧燃烧技术对污泥进行处置和利用的情况.指出结合先进烟气净化技术的污泥干化与焚烧综合利用是目前燃煤 CFB 锅炉混燃污泥应用的较为成熟的工艺之一,在对多种污染物进行有效控制的同时,可以避免污泥贮存、干燥、输送过程中产生臭气对环境的影响.相关调查和分析结论可为燃煤CFB锅炉混燃污泥的设计和安全运行提供参考和依据.
风机装备中存在大量螺栓连接结构,螺栓孔一旦出现缺陷,可能导致整个基体断裂,造成重大事故,但目前螺栓孔缺陷检测方法存在漏检和误判的情况.针对该问题,经过调研、理论分析和实物研究,研制出专用工装与探头结合的直射法、扇扫描偏转法2种螺栓孔缺陷检测方法.以风机变桨轴承螺栓孔为研究对象,采用CIVA软件对2种检测方法进行模拟,可检测出矩形模拟裂纹.采用实际变桨轴承螺栓孔加工矩形槽缺陷进行试验,结果表明直射法可实现对螺栓孔裂纹的缺陷检测.研究为螺栓孔的服役状态监控提出了新的方法,有利于保证螺栓连接结构的安全服役.
Aiming at the problem of low prediction accuracy of single power prediction model due to the impact of photovoltaic power fluctuation,a combined photovoltaic power prediction model based on similar day clustering is proposed.Firstly,k-means clustering is selected to divide the original power data into three similar day sample sets of sunny,rainy and cloudy according to different weather types,and the variational mode decomposition(VMD)is used to decompose the similar day samples;Secondly,the convolution neural network is used to optimize the support vector machine(CNN-SVM)and bidirectional short-term and short-term memory(BiLSTM)neural network,respectively,to predict and superimpose the decomposed power data and combine the prediction results with weights,and the grid search algorithm(GS)is used to find the optimal combination weight to improve the performance of the combination prediction model.Finally,the validity of the PV power prediction model proposed in this paper is verified by the one-year measured data of a photovoltaic power station in Australia.The experimental results show that the model proposed in this paper can predict the photovoltaic power well and has strong adaptability no matter what weather type.
To study the thermal hydraulic characteristics of the printed circuit heat exchanger with rhombic fin channels,variations in thermal hydraulic characteristics on the hot and cold sides were analyzed by numerical simulation,with cold side inlet temperature of 313.15～353.15 K and hot side inlet temperature of 553.15～593.15 K.The working medium on the cold side and the hot side were S-CO2 and gaseous CO2 respectively.The comprehensive performance was compared between NACA0030 airfoil fin channels and rhombic fin channels.The results show that when the inlet temperature of S-CO2 increases by 40 K,the total heat transfer decreases by 23.91％,and the pressure drop of hot and cold increases by 29.95％and 11.14％respectively.When the temperature of gaseous CO2 increases by 40 K,the total heat transfer increases by 16.40％,and the pressure drop of hot and cold increases by 9.42％and 7.43％respectively.The inlet temperature of S-CO2 has more obvious influences on the thermal hydraulic characteristics.The printed circuit heat exchanger with rhombic fin channels has less flow resistance and better comprehensive performance.The results have a certain reference significance for the design of printed circuit heat exchangers with discontinuous channels.
For enhancing the film stiffness of supercritical CO2(S-CO2)hydrodynamic dry gas seal and reducing the additional power consumption due to the installation of heater in the seal inlet line,a new structure of S-CO2 hydrostatic-dynamic dry gas seal with the heating of the ring body at the back of the static ring is proposed.Based on the conjugate heat transfer model,the pressure and temperature distribution of dry gas seal were simulated utilizing commercial software Fluent.The steady-state performance and flow field distribution of S-CO2 hydrodynamic seal,hydrostatic seal and hydrostatic-dynamic seal were compared and analyzed,and the flow and heat transfer characteristics and power consumption of S-CO2 hydrostatic-dynamic dry gas seals under different heating modes and heat temperatures were discussed.The results show that the film stiffness of the hydrostatic-dynamic dry gas seal is improved more than doubled compared with the hydrodynamic dry gas seal,while the leakage rate increased significantly by 35％at the same time.The power consumption under ring heating mode is 44％lower than that under direct gas heating mode,leading to better operating economy.It provides a new idea for the structure design and auxiliary system improvement of compressor dry gas seal in S-CO2 power generation system.
The function of query and statistics of data is always the basis of production management and decision-making businesses.According to the results of information construction and applications for many years,the mode,function and performance of data query and statistics still do not satisfy the actual needs.A component for data query and statistics based on supervisory graph software is proposed and developed.Through the design of data path architecture,the optimization of query and statistics mechanism,the developed component has achieved personalized management,lightweight analysis and flexible query of real-time data.The query and statistic component and data link mode developed in this study have been tested and applied in practice.The results show that the function of data query and statistics achieves loose coupling with database.The component can support both the operation modes of C/S and B/S,and provide unified query and statistics of data through supervisory graph from multi-data sources and multi-level organizations.The efficiency of data query and trend query reaches or approaches the level of database native management tools,and is better than that of conventional supervisory information system(SIS)websites.The integration mechanism of data components based on graph with SIS data query and report system is proposed,which helps to reduce the repetitive cost of data use.
A Printed Circuit Heat Exchanger(PCHE),with straight channels and semi-circle cross section,was fabricated and experimental studies on heat transfer and fluid flow were conducted,during which the flow regime was transition flow,water was working fluid,and flow rate of water was various.The results obtained from correlations of macro circular tubes had obvious deviations from the experimental results.Specifically,the f factor obtained from experiments are larger,and the changes of the overall heat transfer coefficient were more complex with various Reynolds number.The heat transfer and flow correlations in transition zone of PCHE was calibrated within corresponding application ranges.In order to obtain the heat transfer correlations,a numerical method was introduced to obtain one-sided average convective heat transfer coefficients under transition flow.The results showed that the average deviations of the overall heat transfer coefficient obtained from average convective heat transfer coefficients was 8.5％comparing to experimental results,while the maximum deviation reached 17.2％.However,in spite of that,a correlation to predicted the overall heat transfer coefficients through average convective ones still can be obtained,and the deviations comparing with experimental results was within 10％.It is recommended that obtaining one-sided average convective heat transfer coefficient with numerical method is feasible especially when it was transition flow in PCHE.
The non-minimum phase plants with unstable zeros exists widely in the process of power production.Because of the non-minimum phase characteristics,the control system should ensure internal stability while completing output tracking,and improve response speed while overcoming the undershoot.The general PID control cannot meet the requirements of engineering applications.An engineering control and tuning method for non-minimum phase plants is proposed in this paper.Firstly,a robust PID controller is designed to ensure the stability of the closed-loop control system and overcome the under shoot of the system.Secondly,design a second-order filter that includes system position error,velocity error,and acceleration error to improve the response speed and dynamic performance of the control system.This method is simple,easy to tune,easy to configure in DCS,and has strong robustness to model uncertainty,which is worth promoting in engineering.
Based on a DC microgrid system coupled with photovoltaic power generation,lithium battery-supercapacitor hybrid energy storage,electrolysistank and hydrogen-burning micro gas turbine,a power allocation strategy that integrates the lithium battery state of charge(SOC)and hydrogen storage tank hydrogen state(LOH)is proposed.A PV-electrolysistank-micro gas turbine DC microgrid system model is constructed.The allocation logic of the power judgment module of the coordination control layer is designed,and three operation modes are given when the residual power exists in the DC network.The power allocation strategy is simulated and verified using MATLAB/Simulink software.The simulation results show that the power allocation strategy of DC microgrid system based on hydrogen energy storage can make the lithium battery charge state gradually converge to a reasonable storage interval and can improve the service life of lithium battery.
The high-performance supercritical CO2 heat exchanger is the key core equipment to realize the efficient and compact S-CO2 Brayton cycle system.S-CO2 has a low heat transfer coefficient in the smooth channel,and seeking high heat transfer performance and low-resistance heat transfer structure is the key to the development of efficient and compact heat exchangers.Five-axis EDM was used to fabricate the straightly ribbed tube,and the heat transfer behaviors of S-CO2 in the four-headed straight rib tube was experimentally studied,the effect of flow parameters on the heat transfer characteristics of the straight rib tube was systematically analyzed,and the difference in the heat transfer performance between the straight rib tube and the smooth tube was quantitatively evaluated.The influence of structural parameters on the enhanced heat transfer and resistance characteristics was studied by numerical simulation method,and the optimal straight rib tube structure was obtained.The results show that increasing the pressure and mass flow rate can reduce the wall temperature,improve the convective heat transfer coefficient,and the average heat transfer capacity of straight rib tube is about 1.96 times that of smooth tube.Compared with smooth tubes,straight ribbed tubes can effectively delay the occurrence of heat transfer deterioration,the ability to delay the occurrence of heat transfer deterioration by using straightly-ribbed tubes is increased by 0.3～1.8 times.When the fixed rib width W=0.5 mm and the rib height H=2.5 mm,the PEC is the best,and the value of PEC is 1.58.However,the fixed rib height is H=0.5 mm,ε=0.33,and PEC of the straightly-ribbed tube is the best,with the value of PEC is 1.22.
With the transformation of the power system to low-carbon,the proportion of new energy installed capacity is increasing year by year,renewable energy power generation has the characteristics of intermittent,the main power generation period and peak power consumption period are misaligned,there is an imbalance between supply and demand,and the demand for flexibility in power balance is intensified,and long-term energy storage power stations have become a magic weapon to solve the problem.According to the development of long-term energy storage technology,the technical characteristics,advantages and current bottlenecks of pumped storage,compressed air,lithium-ion batteries,flow batteries,molten salt heat storage,and hydrogen energy are analyzed,and the typical application projects of the above energy storage technologies are analyzed.Then,the typical scenario applications of energy storage are analyzed from different sides of the power supply side,the power grid side and the user side,and the application comparison of seven energy storage technologies in multiple scenarios such as energy transfer,auxiliary services,black start,and smooth new energy output is expounded.The technical parameters,battery selection,system wiring,energy management and other issues of chemical energy storage demonstration project,heat storage demonstration project and mechanical energy storage demonstration project were summarized and analyzed,and finally the future energy storage power station technology was prospected.
During frequent long-term standby state of gas turbine generator unit,the surface of 08A1 carbon steel of waste heat boiler economizer fin tube will have serious corrosion problems.In this paper,the macroscopic corrosion phenomenon and corrosion rate of 08A1 carbon steel above the critical humidity were studied by the method of hanging piece and electrical resistance probe.The results show that the corrosion rate of 08A1 carbon steel is the fastest in the first 5 days under the constant environment of 20 ℃ and relative humidity of 70％,and the corrosion depth reaches up to 0.85 μm,accounting for 47.7％of the total change in the whole process.However,the most obvious corrosion phenomenon,including the change of weight and the surface corrosion area,occurred from about the 19th to the 25th day.With the relative humidity gradually increasing from the critical humidity of 70％(ambient temperature 20 ℃),the corrosion evaluation indexes of 08A1 carbon steel show a linear upward trend.Nitrogen filling maintenance strategy under long-term standby state was formulated,effectively alleviating the corrosion condition of economizer fin tube of waste heat boiler.
During the operation of SCR flue gas denitrification system in coal-fired units,ammonium bisulfate(ABS)in flue gas causes ash scale slabbing at the cold end of the air preheater and increases the difficulty of purging and cleaning ash.To this end,ABS premixed ash samples were prepared and pressed and heated at different temperatures,and a new test method was designed to compare the changes in compressive strength of the samples and explore the influence law of ABS on the mechanical strength of ash scale.The experimental results showed that:1)ABS premixed ash samples underwent physical agglomeration and chemical reaction during the heating of slabbing at 147-220 ℃,and the compressive strength was increased by about 95.50％at maximum,among which physical agglomeration played a dominant role with about 88％-89％influence and the influence of chemical reaction accounted for about 10％-12％;2)ABS slabbed ash samples under heating at 220-300 ℃,ABS vaporization precipitation rate reached up to 96.43％,the ash sample from the slab state to loose,compressive strength from 195.50％of the blank sample to 110.17％.It is proved that the means of high temperature heating is feasible to reduce the ABS content in the blockage and create conditions for improving blowing and cleaning from the perspective of ash scale.
Combustion monitoring in large industrial furnace can be simplified to a radiation heat transfer problem within the enclosed cavity system,and precise quantification of its boundary radiation characteristic is the basis to carry out follow-up studyon the radiation inverse problem,but the coupled problem of wall radiation and media radiation need to be solved.A Monte Carlo priciple was involved to solve the radiation heat transfer equation in the enclosed cavity,and to decouple the shares of wall radiation and media radiation in the boundary detection information.The influence of temperature distribution and radiation properties on the share of wall radiation were discussed,at last the experiment verifies the feasibility of using the radiation information of boundary detection to retrieve the wall source term.This study will provide a reference to the exploration of physical field detection method of wall surface in industrial furnace.
Driven by the"carbon peaking and carbon neutrality"goal,hydrogen blending and pure hydrogen combustion technology of gas turbines have received widespread attention.Producing"green hydrogen"from renewable energy and applying it for power generation is the development direction of the energy field in the future.However,the fluctuation of hydrogen source will inevitably cause the change of hydrogen blending ratio of hydrogen blended gas turbine fuel.Therefore,the dynamic response characteristics of the gas turbine are studied when the hydrogen blending ratio fluctuates.Taking an F-class heavy-duty gas turbine as the research object,a dynamic model is built by using the modular modeling method to analyze the response characteristics of key parameters of the unit and the safe operation of components when the hydrogen blending ratio fluctuates under different loads.The results show that when the hydrogen blending ratio fluctuates,the turbine inlet temperature(T3)will fluctuate violently,and T3 overtemperature will occur in the high load region,which will lead to the deterioration of the blade working environment and affect the safe operation of the unit.The larger the fluctuation of hydrogen blending ratio and the higher the power output,the more obvious T3 overtemperature phenomenon.However,the fluctuation of hydrogen blending ratio has a relatively small impact on the compressor,and the compressor can still maintain a reasonable surge margin.
Numerical and experimental studies are conducted on convective heat transfer performance of carbon dioxide(S-CO2)flowing in a heated vertical helically coiled tube under supercritical pressure.The influence of flow characteristics and structural characteristics such as heat flux q,mass flow rate G,pitch P,tube inner diameter d,and spiral radius R on heat transfer are discussed,and the sensitivity of each structural parameter is studied quantitatively.A closed-loop S-CO2 test platform was built to conduct experimental research on the convective heat transfer performance of S-CO2 in the helically coiled tube,and the accuracy of the numerical simulation is verified based on the experimental data.Finally,the heat transfer correlation of S-CO2 is fitted.The research has laid foundation for the thermal design method of S-CO2 spiral-wound heat exchanger,and has certain engineering application value for the application and promotion of the spiral-wound S-CO2 heat exchangers in nuclear power and solar thermal power generations.
The exhausted heat losses in the PRC and inefficiency in medium and low heat source applications are significant challenges affecting the application of supercritical carbon dioxide Brayton cycle for renewable energy sources.To achieve efficient utilization,a precooler-free power/cooling combined system with superior heat source adaptability is proposed and analyzed.Integrating with the precooling-heating coupled module and the absorption power/cooling module instead of the PRC,the waste heat from the LTR is completely recovered,moreover,multiple operating modes ensure that the system performance unaffected by ambient temperature and seasonal changes.Parametric studies indicate that the TUR2 inlet temperature,the WHE1 outflow overheat degree,and the hot end temperature difference have significant effects on the Split Ratio,energy outputs,and the coupling relations among modules.Moreover,due to the improvement of irreversibility and the decrease of exergy losses,the three-largest exergy destructions occur in the IHE,the TUR1,and the RET+GEN,which account for 56.1％,6.9％,and 5.2％respectively.Furthermore,the optimized cases exhibit optimal ηthermal,ηexergy,cP,total,and Wnet of 84.2％,74.1％,9.48 dollars/GJ,and 397.4 MW respectively.
Supercritical carbon dioxide cycle has many advantages such as small turbine size,small compressor power consumption and high cycle efficiency.In order to explore the cycle configuration with the highest power generation efficiency after the power generation system of supercritical carbon dioxide cycle coupled gas turbine,four cycle layouts were proposed.The main parameters of the circulating system were optimized by genetic algorithm with the maximum circulating efficiency as the optimization objective.Among the four schemes,the gas turbine/two-turbine supercritical carbon dioxide combined cycle system has the highest cycle efficiency,which is 44.87％.And the dynamic system analysis of the scheme,with the bottom cycle input heat load as the disturbance variable,explore the dynamic response of the system after the step reduction from full load to 90％load,80％load and 70％load respectively.The results show that the response time of parameters near the flue gas heat exchanger is faster and the response time is longer when the shadow of thermal inertia is farther away from the flue gas heat exchanger in the working medium flow.At the same position,the response time of pressure is slightly longer than that of temperature,and the drop range of parameters near the high-temperature turbine is greater than that of the low-temperature turbine.
