The accurate measurement of solar absorber coating absorption is of great significance to the evaluation and optimization of the absorber performance. At present, the experimental researches of absorber coating absorption are mostly limited to the flat metal substrate. By taking the cylindrical tube of tower solar molten salt absorber, two widely used measurement methods for testing the absorption of curved surface coatings are proposed. The equipment preparation of Blu-Tack method is simple but the operation is complex, and the equipment preparation of diffuse reflection box method is complex but the operation is simple. The two methods isolate the interference of ambient light during the measurement process, and obtain the measured absorption of various coatings attached to the surface of plate and tube. The fitting curve is then established by the corresponding relationship between the absorption of different coatings on the plate and tube, so as to modify the measured data to obtain the absorption of the absorber tube coating. The results show that, the accuracy of the fitting curve R²≥0.995, the maximum relative error is 13.39% when the absorption of 2.5 cm diameter tube is measured directly under unshaded conditions, and the relative error reduces to 0.27% and 0.45% by using Blu-Tack method and diffuse reflection box method, respectively. The difference of the relative error of each point of the two methods is less than 0.30%. The greater the coating absorption, the less the influence of each factor on the measurement results. In the test method of Blu-Tack, the larger the tube diameter, the smaller the measured absorption.

In recent years, numerous incidents of harmonic resonance accidents involving new energy power stations have occurred both domestically and internationally. The frequency scanning method, characterized by its simplicity of operation and clear physical significance, has been widely employed in engineering for the assessment of system resonance. When establishing electromagnetic transient simulation models for large-scale new energy power stations and conducting frequency scans, it is common to substitute a single or multiple generators for the actual power station to reduce modeling complexity. However, the applicability of this approach in addressing high-frequency harmonic resonance issues has not been effectively revealed. To address this gap, this study takes a large-scale photovoltaic power station as an example and employs a bottom-up modeling approach to establish a detailed impedance model for the photovoltaic power station. Building upon this, a dynamic equivalent model is developed using the principle of equal power loss. The two models are then thoroughly compared and analyzed based on actual field station parameters. The research findings indicate that the series impedance of the collector lines has a minimal effect on the harmonic model. As a result, the study proposes a simplified dynamic equivalent model replacing the π-type circuit with a ground capacitor. The results demonstrate that the equivalent model established through the equal power loss method accurately reflects the harmonic resonance characteristics of the photovoltaic power station. Additionally, the model neglecting the inductance of the collector lines proves applicable for analyzing the mid-to-low frequency harmonic resonance in photovoltaic power stations.

An organic Rankine cycle (ORC) unit is designed through thermodynamic analysis and equipment type selection under geothermal conditions. Then, this unit is simulated to study its dynamic operating characteristics and investigate the influences of four parameters, such as heat source temperature, mass flow rate, cooling water temperature and working fluid mass flow rate, on key operating parameters and performance of the ORC unit. The results show that, the output performance of the unit is primarily affected by the cooling water temperature. An increase of 10 ℃ in the heat and cold source temperatures results in a decrease of 16% and an increase of 7% in the output power, respectively. The increased heat source temperature and mass flow rate will make the degree of superheat, evaporating pressure and shaft work increase significantly, and the system thermal efficiency decrease slightly. However, the effect of increasing heat source temperature and mass flow rate on the heat transfer of the cold side is limited, that on the hot side heat transfer is also neglectable, so the vapor superheat and evaporating pressure remains constant. Compared with the change of cold and heat source parameters, the change of working fluid mass flow rate has the lowest overshoot of parameters during dynamic operation of the unit, and the unit can reach the next steady state rapidly.

A new kilowatt-class methane reforming hydrogen production reactor is designed, using solid oxide fuel cell exhaust gas for heat supply. The system can make full use of the waste heat and combustible components in the exhaust gas to form a compact and efficient natural gas power generation system. Computational fluid dynamics was used to numerically simulate the combustion and reforming reactions in the reactor. The results show that the solid oxide fuel cell anode and cathode exhaust gases can be stably burned in the reactor to form a high-temperature flame of 1 486 ℃ to provide heat for the methane steam reforming reaction. In the reaction tube, the concentrations of H₂O and CH₄ continue to decrease along the way. Due to excess water vapor, the H₂O volume concentration at the outlet is 35%, the hydrogen concentration volume fraction is 45%, and the methane conversion rate reaches 90%. Nickel catalyst has a high thermal conductivity, so the temperature difference between the inside and outside of the reaction tube is less than 15 ℃. At the same time, experimental research was used to obtain data such as temperature, methane concentration and methane conversion rate in the reactor. The simulation results were compared to verify the accuracy of the numerical simulation.

The health status of gearbox directly affects the power generation of wind turbine. In order to achieve early warning of gearbox fault status in engineering practice, a K-means clustering algorithm based on improved lion swarm optimization was proposed. The supervision mechanism and the sine and cosine optimization algorithm considering nonlinear weights are introduced into the lion swarm algorithm, and then the optimized lion swarm algorithm is used to iterate the lion king position. By selecting the optimal solution as the clustering center of the K-means algorithm, the problem of strong dependence of conventional clustering algorithms on the selection of initial clustering centers is solved. The UCI data are selected for comparative verification of the algorithm, and the results show that, the K-means clustering algorithm based on the improved lion swarm optimization has achieved a better improvement in classification accuracy and stability. This algorithm is then applied to comparative test of gearbox vibration acceleration effective value for four wind turbines of the same type in a wind farm. It is found that the distribution of classification centers determined by this algorithm is consistent with the actual operating status of the gearbox, and agrees well with the vibration energy distribution corresponding to different states of the gearbox specified in the standard, indicating that the algorithm can realize early fault warning of wind turbine gearbox.

The mathematical and physical models of different semicircular channels are established, and the accuracy of the numerical models is verified by comparing with the experimental data. The thermal and hydraulic heat transfer performance of supercritical carbon dioxide (S-CO₂) in uniform cross-section semicircular tube, diverging tube and converging tube is studied, and the influence of different channels and pressures on the thermal and hydraulic performance of S-CO₂ in a semi-circular tube with variable cross-section is calculated and analyzed. The results show that, compared with the uniform cross-section semicircular tube, the diverging tube deteriorates heat transfer, the converging tube enhances heat transfer. The overall heat transfer coefficient of converging semicircular tube with the inlet and outlet radius ratio of 1.0:0.5 increases by 39.93%, and the maximum evaluation factor PEC of flow heat transfer comprehensive performance is 1.346. When the pressure is closer to the critical pressure or the heat flux is low, the heat transfer performance is higher. Finally, the reason why the converging tube with variable cross-section can enhance heat transfer is explained from the perspective of field coordination and turbulent kinetic energy distribution. The research results can provide new ideas and theoretical guidance for the design and optimization of coolers in S-CO₂ circulation system.

To address the mismatch between electricity supply and demand caused by the intermittency and fluctuation of renewable energy sources, a combined cycle energy storage and power generation system incorporating a closed supercritical carbon dioxide (S-CO₂) cycle and a high-temperature heat pump is proposed, which is an innovative exploration of the Carnot battery form. Through energy exchange via molten salt heat storage and water cold storage devices, this system efficiently integrates the heating process of the heat pump cycle with power generation process of the S-CO₂ cycle, which achieves a favorable round-trip efficiency for the energy storage power generation system. Simulations are performed to calculate the typical operational parameters and thermodynamic performance of the combined cycle, and to analyze the influence of main parameters of the S-CO₂ cycle on the overall efficiency of the system. The results indicate that, increasing the inlet temperature of the expander aids in enhancing the overall cycle efficiency, achieving an optimal electrical-to-electrical efficiency of 62.8%, while reducing the demand for heat storage molten salt. Elevating the inlet gas parameters of the main compressor will lead the system efficiency to reach a peak value, beyond which the overall cycle efficiency no longer increases. The optimal bypass ratio for the main recompressor is 0.35, which allows the system to achieve optimal efficiency. The optimal operating conditions of the S-CO₂ cycle system are identified, offering an electrical-to-electrical efficiency that is 7.98% higher than a reversible Brayton system under the same conditions.

The gas cooler, as an essential heat exchange device in Brayton cycle system, has a significant influence on structural compactness and operational efficiency of the cycle system. The performance and influencing factors of a cross flow printed circuit heat exchanger (PCHE)-plate-fin gas cooler are analyzed. A calculation model is established for this type of heat exchanger, and a MATLAB program is written to verify its reliability. Based on this, the coolers are designed, and the power density is above 1 MW/m³, indicating the cooler is compact heat exchanger. Moreover, the design and performance analysis of the heat exchanger are carried out under varying working conditions, and the change law of the pressure drop and heat transfer performance of the gas cooler with the inlet state of the circulating working medium and cooling air is given. The pressure drop and heat transfer performance are compared when the working medium of the Brayton cycle is supercritical carbon dioxide, nitrogen and air. The results show that, the change of cold and hot fluid mass flow has the most obvious influence on the heat transfer performance. The research has reference significance for the design and operation of Brayton circulating air cooling heat exchangers.

The increasing volume of sewage sludge production in China has created an urgent need for its harmless and resourceful treatment. This paper aims to tackle this issue by adopting a novel strategy that integrates coal-fired power plants with a sewage sludge drying system, in this method, the sludge will be co-fired after being dried. By taking a typical supercritical 660 MW unit as the research object, the influences of moisture content (10%, 20%, 35%, 50%, and 65%) and blending ratio (2%, 4%, 6%, 8%, and 10%) of the dried sludge on parameters such as flue gas temperature, boiler efficiency, net power generation efficiency, equivalent net efficiency of sewage sludge power generation and equivalent net efficiency of dried sludge power generation are investigated through thermodynamic calculation of the boiler and comprehensive thermodynamic and economic analysis of the entire system under THA condition. The results indicate that, when the moisture content of the dried sludge exceeds 50%, it leads to parameter deterioration, and this trend intensifies with an increase in the blending ratio. Considering all factors, it is recommended to maintain the moisture content of the dried sludge at 50% or below, and if it exceeds this value, the blending ratio should be limited to less than 4%. Blending sludge leads to a reduction in the exergy efficiency of the system, which is mainly due to the increasing exergy losses in the boiler and drying equipment. Moreover, the study reveals that the optimal economic performance is achieved when blending the sludge with moisture content of 20% and blending ratio of 10%, in this case the dynamic payback period is only 4.02 years.

The coupling of coal-fired units with molten salt electric heater systems can significantly improve their frequency regulation and peak shaving capabilities. On the basis of Modelica language, a dynamic model of the molten salt electric heater is established and the experimental verification is completed, it reveals the dynamic characteristics of the molten salt electric heater under the disturbance of molten salt flow rate and unit AGC load. A temperature control method of “feedforward+PID” regulation is proposed based on its dynamic characteristics, and the characteristics of electrical load and thermal parameter changes during AGC regulation of coal-fired units assisted by molten salt electric heaters are calculated and analyzed. The results indicate that, configuring a 10 MW molten salt electric heater can increase the AGC variable load rate of a 660 MW coal-fired unit by 340%, and the proposed control method can maintain the stability of thermal parameters of the electric heater.

The anti-freezing operation parameters of indirect air-cooled finned bundle are insufficient at present. To solve this problem, this research firstly concludes the anti-freezing model of finned tube bundle, including the thermal equilibration equations, water side and air side transport equations, as well as anti-freezing constrains. Secondly, based on the co-current and counter-current air-cooled finned tube bundles, the critical anti-freezing characteristics and margin are analyzed. Then, the critical values are discovered for finned tube bundles with middle inlet, left inlet and side inlet patterns. The research shows that, as the ambient temperature or inlet water temperature reduces, as well as the ambient wind increases, the critical anti-freezing water flow rate ascends. Besides, when the inlet water temperature decreases, the wind effects get intensified. The anti-freezing performance of counter-current finned tube bundle is inferior to that of the co-current type, meanwhile the difference becomes expanded if the wind increases or water inlet temperature decreases. The effects of inlet water temperature elevation on anti-freezing margin can be classified into three levels, which are termed as obvious range (0 ℃, 10 ℃], slow range (10 ℃, 20 ℃], and stable range (20 ℃, 40 ℃]. Therefore, power plants should not always increase the water flow rate for anti-freezing operation. The air-cooled finned tube bundle with middle inlet pattern has better anti-freezing performance than others, so it’s suggested preferentially for coal-fired or nuclear power plants. This research may provide guidelines of anti-freezing operation for dry-cooling power stations in China.

Flue gas flow is one of the key factors affecting the accuracy of carbon monitoring, and the complex flow field environment with uneven velocity distribution and changing with unit load is the main factor impeding the accurate measurement of flue gas flow. By taking a chimney inlet flue of a 660 MW unit in a power plant as the research object, the influence of the number of points and the layout of the process on measurement accuracy of the flowmeter with four different measurement principles was compared and analyzed based on numerical simulation results of the flue gas flow field. The results show that, the multipoint Pitot tube flowmeter has better adaptability to the complex flow field environment compared with the matrix flowmeter. When the number of measuring points is 28, the deviation of the matrix flowmeter is 1.54 times that of the multipoint Pitot tube flowmeter. The measurement accuracy of the light scintillation flowmeter is greatly affected by the elevation of the installation position, with the maximum deviation being 23.3 times the minimum deviation. This indicates that the light scintillation flowmeter has poor adaptability to complex flow field environments. The ultrasonic flowmeter can be installed obliquely and in multiple channels, with a more flexible and varied process layout, significantly improving its adaptability to complex flow fields. The dual-channel arrangement can control the deviation within ± 1.5%. The research results provide important theoretical basis and data support for the selection of flow meter equipment and process design, and have important theoretical research and engineering application value.

In 2021, China launched its national carbon market. To enhance the accuracy of carbon trading, it is essential that carbon emission data are measurable, reportable, and verifiable. Against this backdrop, online monitoring systems for flue gas have gained significant attentions as a method of quantifying carbon emissions. The basis for the effective work of continuous emission monitoring systems is the accurate measurement of flue gas flow. However, the challenge in accurately measuring flue gas flow rates is significantly heightened by the large size of power plant chimneys and the complexity of the gas flow characteristics within them. This paper focuses on analyzing the current research status of Pitot tube flowmeters and ultrasonic flowmeters in large-scale duct flow measurement, and provides a detailed introduction to gas flow measurement technologies for large-scale ducts. Additionally, it introduces an independent flow measurement method, namely the tracer gas dilution method, and discusses its current development and potential as a flow calibration method.

The existing thermal power flexibility renovation plan is difficult to eliminate the thermal system life loss and unit safety operation risks caused by frequent and rapid load changes. In order to effectively ensure the safety, economy, and health of thermal power units participating in grid peak shaving, a full capacity and long life peak shaving technology scheme for thermal power units based on the coupling of solid oxide electrolysis cell hydrogen production technology (SOEC) and burner local oxygen enriched combustion technology (OEC) is proposed and constructed. Taking an ultra supercritical 1 000 MW secondary reheat unit as an example, energy efficiency calculation is conducted on the SOEC-OEC system participating in power grid peak shaving at a depth of 70%~100%, and the results are compared with that of the conventional alkaline water electrolysis hydrogen production (ALK) system. The results show that, the energy efficiency of the extraction electrolysis hydrogen production system in SOEC-OEC is as high as 49.86%, which is about 26.40% higher than that of the ALK system. The oxygen enriched combustion system can reduce the boiler exhaust gas by up to 23.7%, reduce the unit coal consumption by 2.83 g/(kW·h), and reduce the carbon emissions by about 2.82 t/h. In addition, the SOEC-OEC system can also bring excess peak shaving subsidy benefits, hydrogen sales revenue, oxygen enrichment and coal saving and carbon reduction revenue, as well as equipment life extension benefits to the unit, fully ensuring the economic efficiency, safety, and environmental protection of the thermal power peak shaving process.

Responding to the urgent needs of clean and efficient utilization of coal under the background of national “carbon peaking and carbon neutrality”, the pulverized coal preheating combustion technology has been developed in industrial boilers, power plant boilers and other fields. In this technology, pulverized coal is modified at high temperature in a fluidized preheating burner, then the preheated fuel enters the furnace for graded air distribution combustion, thus high efficiency and low NO_x combustion of pulverized coal is realized. Moreover, technical verification was carried out on a 60 t/h pulverized coal boiler, which adopts two preheating burners with side wall hedge arrangement, and one preheating burner is designed with thermal power of 26 MW. Using bituminous coal as raw material, the operation and NO_x emission properties of the boiler at 10%~100% operating loads were studied experimentally, and the results showed that, the boiler operated stably and well at each load, it achieved stable operation of 10% ultra-low load without any auxiliary means. The preheating burners had reasonable operating parameters and stable circulation state, which can meet the requirements of wide load operation of the boiler. The combustion efficiency of the boiler at each operating load were all above 97%, the thermal efficiency of the boiler were above 85% at 10% and 20% operating load, and above 90% at 30% and above operating load. By adjusting the air distribution, the original NO_x mass emission of the boiler at each operating load can be controlled lower than 50 mg/m³ (φ(O₂)=9%). The successful demonstration of the 60 t/h pulverized coal preheating combustion boiler provides important support for the development and application of clean, efficient and flexible combustion technology of pulverized coal.

Aiming at solving the problem of complex and uneven flow field inside the coal pulverizer, a complete model of medium-speed coal pulverizer was established. The CFD software was used to solve the internal flow equation of the coal pulverizer. Moreover, DPM iteration was used to obtain particle flow parameters, and the internal flow of the medium-speed coal pulverizer and distribution characteristics of outlet air-powder at different rotation speeds of dynamic classifier were explored. The results showed that, the distribution characteristics of primary air at four pulverizer outlets were good and consistent with the test results. When the powder diameter was small, the powder mass flow deviation at four pulverizer outlets was small, and the fluctuation was not obvious with the increase of the rotation speed of the dynamic classifier. With the increase of powder diameter, the motion trajectory of powder showed a wall adherent motion, and the powder mass flow deviation at four pulverizer outlets gradually increased. Furthermore, for coal particles with large diameters, with the increase of the rotation speed of the dynamic classifier, the powder mass flow deviation at four pulverizer outlets gradually decreased.

Aiming at the lack of fault samples of power equipment, this paper proposes a dry-type air-core reactor condition assessment method based on belief rule base. By building a test platform for the electrical and temperature rise characteristics of dry-type air-core reactors under multiple working conditions, a data sample set of reactor active power and the temperature rise rate of the hottest point is obtained under different operating conditions. A reactor condition assessment model based on belief rule base and evidential reasoning is established. In order to reduce the influence of expert subjectivity on the prediction results of the state assessment model, a belief rule base optimization method is proposed, and the evidential reasoning algorithm is used to convert the input feature information of the reactor into the output state level. The evaluation model was tested by test data, and the results verified the validity and accuracy of the dry-type air-core reactor condition assessment method based on small training samples.

In electric power ancillary service market, coal-fired thermal power units are facing new opportunities and challenges in participating in frequency regulation auxiliary services. During operation of large-capacity (ultra) supercritical coal-fired unit boilers, the energy storage is limited and the AGC frequency regulation response performance are difficult to adapt to the increasing frequency regulation demand of the ancillary service market. To solve these problems, the influence of different energy states of grid and source on frequency regulation is analyzed, and a self-adaptive frequency regulation control strategy based on grid-source operation state is designed. This strategy is based on the boiler energy storage state and the grid frequency regulation demand, and can adaptively undertake the AGC frequency regulation task in the frequency regulation ancillary service market. It fully exerts the frequency regulation potential of the unit, and is beneficial to fast energy balance and parameter recovery stability of the unit itself, which realizes the grid-source goal coordination of the safe and stable operation of the unit and the improvement of the comprehensive frequency regulation performance index of the unit.

In order to study the microstructure properties of different regions of welding heat affected zone (HAZ) of 1 000 MPa grade ultra-high strength steel, the samples of test steel at different peak temperatures of thermal cycle were prepared by welding thermal simulation technique, and the impact toughness of different regions of HAZ was studied through Charpy impact tests. The results showed that, in the subcritical region of HAZ (SCHAZ), the intercritical region of HAZ (ICHAZ) and the fine-grained region of HAZ (FGHAZ), the samples had relatively high impact absorption energy, crack propagation energy and dynamic impact toughness, and a large area of fiber region and shear lip formed on the fracture surface. Toughness dimples of different sizes can be seen at the microscopic level. The samples had good impact toughness. In the coarse-grained region of HAZ (CGHAZ), all impact data of the samples sharply decreased, and the fracture showed a macroscopic brittle fracture, almost all of which are radiological regions. At the microscopic level, it showed quasi cleavage fracture characteristics, indicating that the resistance to crack propagation decreased, and the time for stable propagation decreased after crack initiation, and the instability propagation was fast. The impact toughness of the samples deteriorated, and the CGHAZ region was a ductile valley region in HAZ. The results showed that the coarse grains and the coarse M-A island were the main causes of embrittlement in the CGHAZ region. The conclusion lays a theoretical foundation for the selection, development and engineering application of 1 000 MPa grade ultra-high strength steel in hydropower projects.