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 is1.58. 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.

Self-recirculation casing treatment can significantly improve the aerodynamic performance of the supercritical carbon dioxide centrifugal impeller in small flow rate region, but the improvement is not obvious near the large flow rate region. Therefore, the coupling effect between the self-recirculation casing treatment and the key parameter of the impeller is considered, and the coupling optimization of the casing treatment geometry and the impeller blade sweep angle is carried out to achieve a comprehensive improvement of the impeller performance. After the coupling optimization, the efficiency of the impeller is increased by 3.51%, 2.60% and 4.43% respectively under the large flow rate condition, the design condition and the small flow rate condition. The mechanisms of the coupling optimization for stability and efficiency enhancements are as follows. Under the large flow rate condition, the flow incidence angle of impeller is improved, the subcritical zone inside the impeller is reduced, then the condensation is suppressed and the flow capacity of the impeller is improved. Under the design condition, the recirculation flow of casing treatment is increased, more low-energy fluid near the shroud tip is removed, and the flow field structure downstream of the impeller is improved. Under the small flow rate condition, the internal blockage of the impeller is effectively reduced, the flow stability of the impeller is enhanced, and the mixing loss caused by the recirculation flow is improved, so the impeller efficiency is improved.

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.

The carbon dioxide (CO₂) Brayton cycle system is compact, efficient and flexible, and has a good application prospect in the third generation photothermal system and the fourth generation nuclear power system. The deterioration of CO₂ heat transfer affects the safe operation of the unit. In order to study the deterioration of CO₂ heat transfer in the vertical riser, a CO₂ heat transfer characteristic system is established for experimental research, and the CO₂ heat transfer characteristics under subcritical and supercritical conditions are compared. The influence of thermal parameters on the deterioration of CO₂ heat transfer is obtained, and the prediction correlation of CO₂ critical heat flux is established. The predicted value is in good agreement with the experimental value (error ±30%). It is found that the peak value of wall temperature is higher when CO₂ heat transfer deteriorates at subcritical pressure. Far away from the critical pressure and increasing the mass flow rate are conducive to restraining the occurrence of heat transfer deterioration.

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.

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.

A comparative analysis between simulation and test with roughness is carried out for a supercritical carbon dioxide (S-CO₂) axial turbine with different operating conditions, focusing on the roughness impact of the turbine performance. The results show that the numerical calculation method of wall roughness is able to assess the performance of the turbine at different load conditions accurately. Compared with test result, the maximum efficiency error is 1.82 percentage point. Wall roughness degrades the overall performance of the turbine, with a maximum efficiency drop of 2.8 percentage point at Ra1.6 roughness level during the five working condition, and the turbine stage roughness has a more obvious effect on the turbine performance. In addition, the more severe of wall roughness, the greater reduction of turbine efficiency. In non-design operating conditions, the efficiency drops by 11.6 percentage point at Ra6.3 roughness level. The wall roughness exacerbates flow separation of pressure surface, causing greater friction losses and serious affecting of turbine performance. The research can provide technical support for the design and performance simulation of S-CO₂ axial turbines.

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.

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 η_thermal, η_exergy, c_P,total, and W_net of 84.2%, 74.1%, 9.48 dollars/GJ, and 397.4 MW respectively.

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.

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.

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 optimal scheduling and economy of new energy hydrogen production systems are closely related to hydrogen production efficiency. Aiming at the problem of low hydrogen production efficiency in existing new energy hydrogen production systems, this paper proposes a control strategy for new energy hydrogen production systems based on particle swarm optimization (PSO). Firstly, based on the polymer electrolyte membrane (PEM) electrolytic cell model, the relationship between the operating point of the electrolytic cell and the hydrogen production efficiency is analyzed. Secondly, a hydrogen production system operation control method based on particle swarm optimization algorithm is proposed to improve the hydrogen production efficiency of the hydrogen production system. Furthermore, an optimal scheduling model for new energy hydrogen production systems considering the efficiency of system hydrogen production was established, and particle swarm optimization algorithm was also used to solve the optimal hydrogen production power. Finally, through simulation analysis of actual power grid operation data, it is proved that the proposed control strategy can effectively improve the hydrogen production capacity and system revenue compared to traditional startup and shutdown strategies, providing a theoretical basis for the large-scale application of hydrogen production systems in power grids.

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.

Test for large-size wind turbine rotor under static and rotating conditions have been carried out for rotor dynamic characteristis. Based on experimental modal and operational deflection shape, firstly this test obtained modal data using LMS TEST.Lab system by calculating FRFs and curve fitting. Secondly the resonate speed was obtained according to the vibration sweep test. Then modal parameters were analyzed through operational deflection shape test under the resonate speed. The results show that the resonate frequency under rotating condition is different from the resonate frequency under the static condition. And the modal shape of rotor under rotating condition is travelling wave while it is standing wave under static condition. In conclusion, the integral stiffness is decreased when the rotor is rotating which results in the decrease of the resonate frequency, the modal shape turns to be the travelling wave resulting from the rotating magnetic force. This research results can offer a reference and guidance for rotor dynamics evaluation, simulation model modification and parameter input, and optimization design of rotor structure .

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.

To solve the problems of uneven distribution of NO_x concentration at the outlet and excessive ammonia escape in the actual SCR operation of power plants, the SCR DeNO_x reactor was simulated numerically and a new ammonia injection optimization method for dual control of ammonia slip and nitrogen oxides emission was proposed. Taking the SCR DeNO_x system of a 660 MW unit as an example, a numerical model of visual flow field and DeNO_x reaction was established, and the change of the partitioned outlet NO_x concentration, ammonia slip and partitioned DeNO_x efficiency under different total ammonia nitrogen ratios were analyzed and compared. The results show that the relationship between partitioned DeNO_x efficiency, outlet NO_x and ammonia concentration, with the partitioned ammonia-nitrogen ratio is a two-parts linear relation separated by an inflection point, and the inflection point occurs when partitioned ammonia-nitrogen ratio is about 1.15. On this basis, the present study proposes a new optimization method for ammonia/nitrogen dual control optimization based on the combination of piecewise fitting function and optimization matrix equation. It is predicted that the 660 MW unit by using 5 zones and 42 nozzles for ammonia injection regulation, and the optimized total ammonia injection volume will decrease by 7.2% at the best compared with the uniform ammonia injection working condition. Relative standard deviation of outlet NO_x concentration and ammonia slip volume will decrease to 9.4% and 4.2% respectively, and the outlet uniformity will be significantly improved, and there is no locally over DeNO_x phenomenon.

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.

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.

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.

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.

During frequent long-term standby state of gas turbine generator unit, the surface of 08Al 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 08Al 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 08Al 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 08Al 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.

This paper proposes a multi-parameter collaborative monitoring system and method for degassed hydrogen conductivity based on the combination of double water membrane degassed method and electric regeneration ion exchange technology, which can quickly measure a number of key water quality indicators such as conductivity, hydrogen conductivity, degassed hydrogen conductivity and pH. It can make comprehensive evaluation of water quality, guide thermal equipment shutdown and startup. And it can adjust normal operating water conditions. It has a great significance for ensuring water vapor quality and thermal equipment corrosion, salt accumulation and scale formation. Double water membrane degassing technology is used to measure degassed hydrogen conductivity, which can effectively remove CO₂ from water. On this basis, a method of calibration degassed hydrogen conductivity measured by standard solution is proposed, so that the accuracy of the measured value can be effectively evaluated. This method has been applied to typical gas combined cycle units and heating units for on-site supervision. It proves that the method has high measurement accuracy, can quickly and comprehensively evaluate water vapor quality, and it can assist in solving various technical problems on site. Therefore, it has strong popularization and application value.