Raw water pretreatment can be divided into three stages: coagulation, sedimentation and filtration. The flocculation process directly affects the structure of alum and the turbidity of effluent. At present, the method of measuring the turbidity of the effluent is usually used to control the dosage of coagulant, but due to the time lag, it can not quickly reflect the coagulation effect and adjust the dosage of the feedback. With the rapid development of computer technology, the application of alum image processing technology can realize rapid, accurate and real-time detection of flocs state, so as to control the dosage more accurately and improve the coagulation effect. From the perspective of computer vision technology, this paper summarizes the technical characteristics of alum image acquisition and processing in flocs, introduces the method of real-time tracking and calculating the characteristic parameters of alum structure, such as equivalent particle size, fractal dimension, etc., and some test results are also provided. Through these parameters the best coagulation effect can be judged, which provides the basis for coagulation control and dosing.

The HT700 superalloy was joined by rotational friction welding (RFW) method, and the welded specimens were subjected to post weld heat treatment (PWTH). The microstructural evolution and mechanical properties of the joints were systematically investigated by optical microscopy, scanning electron microscopy, transmission electron microscope, micro-hardness, and tensile tests at both room temperature and 750 ℃. The results show that, the as-welded joint shows three typical zones across the weldline: weld center zone (WCZ), thermomechanically affected zone (TMAZ), and heat affected zone (HAZ), in which the microstructure gradually changes from equiaxed fine grains (WCZ) and deformed coarse grains (TMAZ) to equiaxed grains (HAZ) that are similar to the base material. The dynamic recrystallization and dissolution of strengthening phases have occurred in the WCZ during RFW, in which γ′ strengthening phase dissolves to a larger extent than M23C6 or MC carbides. The microstructure of the as-welded joint including the grain size, shape, and the distribution of precipitates gradually changes from the weldline to the parent alloy. Consequently, the as-welded joints exhibit relatively poor mechanical properties due to the dissolution of γ′ which becomes even worse at 750 ℃ because of the grain-boundary sliding. After PWHT, the as-welded microstructure can be homogenized by grain growth and the re-precipitation of strengthening phases, which is responsible for the remarkable improvement in tensile strength at both room and high temperature after PWHT. And the high-temperature ductility of PWTH joints has been improved to a certain extent. This study gives new insights into the high-quality welding of the HT700 superalloy.

ZnFe₂O₄ oxygen carrier (OC) doped with different additives (Sr, Ce, La and Al) was prepared by sol-gel method to investigate the influence of different additives on performance of the ZnFe₂O₄ oxygen carrier. Chemical looping hydrogen generation (CLHG) experiments were carried out in a fixed bed reactor. It was found that the performance of ZnFe₂O₄ was greatly improved by doping different metals, and the hydrogen production of per unit mass OC from high to low is La>Sr>Al>Ce. The physicochemical properties of different amount of La-doped ZnFe₂O₄ were further analyzed by combining X-ray diffraction, H₂-temperature-programmed reduction, Brunauer-Em-mett-Teller method and other characterization methods. The data indicated that the ZnFe₂O₄ modified by La with 12% mass fraction has the highest reaction activity. La dropping can increase the specific surface area of the OC, reduce the reduction temperature, increase the migration rate of lattice oxygen, promote the formation of oxygen vacancies, and is beneficial to the increase in hydrogen production in the chemical looping process.

To solve the problems of fouling, slagging, and high-temperature corrosion in an ultra supercritical 1 000 MW unit boiler fueled by Zhundong coal, engineering verification test of nano-high-entropy ceramic coating in separated over fire air (SOFA) area of the boiler rear water wall was carried out, based on the coal characteristics, slagging condition and corrosion type of the boiler. Several methods such as macrographic check, scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectrum, friction coefficient and surface energy test were applied to observe the change of nano-high-entropy ceramic coating before and after experiments, thus to reveal the possible slag resistance and corrosion resistance mechanisms of nano-high-entropy ceramic coating. The results show that, the coating remained intact after 11 months’ boiler operation, with no obvious slagging and corrosion pits on the surface and no significantly thinning of the pipe wall. Nano-high-entropy ceramic coating can better solve the problems of fouling, slagging and high-temperature corrosion on the boiler water wall, which provides a guarantee for safe operation of the boiler fueled by Zhundong coal.

Transformer insulating oil will gradually deteriorate during the operation of power equipment, resulting in a significant reduction in the electrical, physical and chemical properties of transformer oil. In this paper, the adsorption phase reaction technology is used to solidify hydrophilic SiO₂ nanoparticles on microcrystalline cellulose (MCC), to prepare modified cellulose dust collector materials with high adsorption performance, to purify and treat dirty transformer oil by combining with electrostatic adsorption technology. For the SiO₂ modified cellulose dust collector material, it can be concluded through the oil purification effect test that, the best preparation condition is dissolution and drying for 12 h, and adding 6 g ethyl orthosilicate (TEOS) as a silicon source. Then, the modified cellulose dust collector material prepared above conditions is placed in the electrostatic oil purification reactor. After synergistically purified by the two methods, the transformer oil’s main operational indicators such as moisture reduces from 32.0 mg/L (the initial value) to 23.5 mg/L or less, and other key indexes including medium loss factor, acid value and volume resistivity have reached the national standard of operational oil. It shows that the electrostatic technology combined with modified cellulose adsorbent material can effectively adsorb the impurity particles in the oil.

Solar power plants can be complementary to other new energy power generation stations, and can also undertake the task of peak modulation and frequency modulation of power grid, which have attracted more and more attentions. In this paper, the dynamic simulation model of thermal storage system and power generation system is built and verified by Apros software. The coordinated control system of solar power plant considering the influence of heat storage is designed, and the maximum variable load rate of the solar power plant in different load intervals is studied. The results show that the proposed coordinated control strategy has a good control effect. Compared with the control without heat storage control, the deviation of main steam pressure with heat storage control reduces from 0.17 MPa to 0.07 MPa. Under the set limit conditions, the maximum load rise rate of 100%THA~75%THA load interval is 11.57%/min, and the maximum load reduction rate is 8.94%/min. The results can provide reference for peak shaving and frequency modulation operation of photothermal power plants.

At present, domestic research on gas control valves or other equipment in gas turbines is still lacking, while most of these researches’ models remain in a single hydraulic valve or a hydraulic cylinder. So this paper uses Simulink/Simscape software to model the entire gas turbine’s gas control valve including the PI controller to the gas pipeline, and conduct simulation analysis for faults such as fixed orifice blockage, wear of the spool valve core and hydraulic oil contamination to discuss their forms and causes. The result shows that, the blockage of the one-sided fixed orifice of the nozzle damper valve, the wear of the slide valve core and the impurities in the hydraulic oil will all cause the valve to respond slowly, or even become clogged and stuck to varying degrees. Finally, for the monitoring of valve data in current power plants some suggestions are thrown out: according to the actual operating conditions, monitoring of the parameters such as the servo valve spool displacement signal and hydraulic cylinder piston displacement can be introduced by using electronic feedback servo valve, to better judge the health status of the valve.

In view of the increasingly serious problem of power grid peak regulation caused by the instability of new energy, combined with the relatively mature photo-coal complementary power generation technology and the multi-heat source combined heating peak shaving system, the light-coal mixed heating power generation system was designed to make the cogeneration unit have a certain peak regulation capacity. Based on the actual operating conditions of the heating unit and the premise of ensuring the heating load, the coupling mode of the solar-assisted dual-engine cogeneration unit was analyzed, and the peak regulation performance of the two-engine was compared before and after coupling. The results show that, a dynamic throttle valve is installed on the pipeline between the condenser outlet and the heat exchanger of the solar collector system, and the operation mode of the auxiliary heating unit of the solar collector system can be changed, which can realize flexible operation of the integrated system of power generation, heating and peak regulation. Among them, the solar thermal collection system is only used for supplementary heating, the peak regulation capacity ratio is 0.76, and the ratio of solar auxiliary double-heating supply before and after peak regulation capacity is 0.55. The No.1 unit which is assisted by solar energy to bear the maximum heating load has the best performance in peak regulation capacity and peak regulation compensation.

Due to the characteristics of the medium transported by medium speed coal mill and the limitations of the inlet pipeline and space, the testing method under cold pure air conditions cannot guarantee the timeliness of the calibration test for the inlet air volume. Under hot conditions, the outlet pipeline of the coal mill was selected as test object for its stable flow field. The dynamic pressure and pulverized coal distribution characteristics of each powder pipe were tested by the equal cross-section grid method. The flow velocity of the air-powder mixture was obtained by the cyclic iterative method. Finally, the inlet air volume of the coal mill was compared and calibrated by the difference between the measured air-powder mixture flow rate, the coal quantity and the design sealing air volume. The practical results show that, on the basis of the same measured original data, the inlet flow rate obtained by the method above is closer to the real value, the accuracy can be improved by about 15 percentage points compared with the calculation results with cold conditions method. This method is simple to test and practical, which can effectively improve the timeliness and accuracy of the inlet air volume calibration results of medium-speed coal mill under hot conditions, and at the same time, it also has a certain guiding role in test of the flow rate of powder-containing gas in similar industrial environments.

To unveil the ultra-low load operating characteristics and performance optimization method of large-scale units burning high moisture lignite, the influences of burners operating scheme under 33%BMCR condition on the coal combustion, heat transfer and NO_x transformation characteristics of a 660 MW unit utility boiler were investigated, based on an established and validated simulation model of coal-fired boiler. The results show that, well-organized flow and combustion field can still be formed inside the furnace under ultra-low load condition, but the overall boiler performance deteriorates evidently, such as obvious decreases in combustion temperature and heat transfer intensity, and increase in NO_x emission at outlet of the furnace. When 4 layers of burners are in-service, continuous lower-middle groups or middle-upper groups of burners should be put into operation, to prevent the significant deteriorations of combustion and heat transfer processes and the significant increase in NO_x emissions. The number of in-service burners layers significantly affects the overall boiler performance. When there are only two layers of burners in-service, the intense coal combustion area is too concentrated, which is not conducive to maintaining a high combustion temperature and heat transfer intensity, and NO_x emissions at the furnace outlet increase at the same time. These findings reveal the influences of burner operating scheme under ultra-low load condition on the overall performance of a 660 MW lignite boiler, which can provide guidance for deep peak shaving operation adjustment and optimization of coal-fired units in the context of large-scale renewable energy power grid connection in the future.

In the context of current energy structure transformation, conventional thermal power would gradually transform into grid source support and system regulation. Coupling with distributed photovoltaic power is an effective attempt for thermal power enterprises to achieve cost reduction and efficiency improvement. However, due to the lack of relevant guidance for the connection of non centralized power sources for the factory use, there is a lack of evaluation strategies and empirical references for system security and stability. For this purpose, taking the thermal photovoltaic complementary energy supply system of a thermal power plant in northwest China as an example, its operating characteristics are analyzed and a technical framework for stability evaluation is provided. In examples of different power units, grid connection levels, and minimum photovoltaic unit layout, application evaluation issues such as static power flow, transient stability, and power quality are discussed. It is calculated that the power consumption reduction efficiency of thermal power units in this case achieves an improvement of 18%~42%. This conclusion has typical reference significance for the application of the power generation technology model of “distributed photovoltaic access to plant use systems” in thermal power plants.

In order to explore the film cooling potential of crater holes, numerical simulations are performed to investigate the film cooling characteristics of equal-section crater hole, concentric elliptical crater hole, and two types of rounded corner crater holes proposed on the basis of these two types of crater holes. Cooling efficiency curves are analyzed for four types of crater holes at blowing ratios of 0.5, 1.0 and 1.5. The results show that, the crater spreading width of crater holes and crater film holes with rounded corners increases, which is beneficial to spreading coverage of the cooling film. After the crater holes are rounded at three blowing ratios, the Coanda effect strengthenes the ability of the cooling jet to adhere to the wall, and the film cooling efficiency in the near-hole region improves significantly. As the blowing ratio increases, the area-averaged film cooling efficiency after the rounded corner treatment increases by 76%, 139% and 155%, respectively, for the equal-section crater hole. The area-averaged film cooling efficiency improves by 18%, 27%, and 29%, respectively, for the concentric-elliptical crater hole with rounded corner compared with that of the concentric-elliptical crater hole.

It is difficult to control NO_x emissions during full load operation of a 660 MW supercritical circulating fluidized bed (CFB) boiler in a certain power plant, and its instantaneous value is prone to exceed the ultra-low emission limit. In addition, the selective non-catalytic reduction (SNCR) system has a high ammonia consumption and severe ammonia escape issues. To solve these problems, on-site experiments on NO_x original emissions, SNCR denitrification efficiency, CO mass concentration and bottom slag combustibles were conducted, and optimization experiments on secondary air volume layout were also performed. It was found that, the original NO_x emissions of the CFB boiler were relatively low, with a maximum of 120 mg/m³ (standard condition) during full load operation and a NO_x mass concentration below 50 mg/m³ during medium and low loads. However, there was a significant deviation in NO_x mass concentration between the front and rear ends of the furnace, and the NO_x in flue gas was mainly generated in front of the furnace. The reason why NO_x emissions are difficult to control is due to the low denitrification efficiency of SNCR and uneven coal feeding in the furnace. The SNCR denitrification efficiency at inlet of the 6 separators was all below 50%, among which the denitrification efficiency of four separators B, C, E, and F was below 40%. Furthermore, according to the distribution of parameters in the furnace depth direction, such as the bed temperature, the content of combustible materials in bottom slag, and the variation of CO mass concentration, it can be determined that the uniformity of coal feeding in the furnace also had a significant effect on the control of NO_x emissions at full load. Currently, the power plant cannot achieve uniform coal feeding without renovation, but the original NO_x generation can be reduced by adjusting the secondary air volume ratio in the depth direction of the furnace, with a reduction of up to 9.77%.

With the increase of various types of cyber-attacks, the security of industrial control systems in energy and power infrastructures has gradually become a focus of attention. Combined with the characteristics of power system, the CNN-LSTM-Attention network intrusion detection algorithm model integrating convolutional neural network (CNN), long and short-term memory (LSTM) neural network and Attention mechanism is proposed. By constructing and collecting the operating state data sets of the pulverizing system of a 600 MW coal-fired unit under three typical operating conditions under cyber-attacks in a laboratory simulation environment, the proposed detection algorithm model is trained and evaluated. The results show that, the proposed intrusion detection algorithm model has the best performance compared with the CNN and LSTM models. The model has the best rating indexes such as accuracy, precision, recall, etc., and the comprehensive evaluation is better than other intrusion detection methods. The intrusion detection algorithm model is highly innovative and practical.

In order to solve the problem of low accuracy of wind power prediction caused by wind speed uncertainty and volatility, this paper proposes a VMD-ISSA-GRU combination model based on variational mode decomposition (VMD), improved sparrow search algorithm (ISSA) and gated recurrent neural network (GRU). Firstly, the center frequency method is used to determine the number of modal components after VMD decomposition, which can effectively avoid over-decomposition or insufficient decomposition. Then, chaotic mapping, nonlinear decreasing weights and a mutation strategy are introduced to improve the sparrow search algorithm to optimize the gated recurrent neural network, and then an ISSA-GRU prediction model is established for each decomposed subsequence. Finally, the predicted value of each subseries is superimposed and the final predicted value is obtained. The experimental results show that, the mean absolute error, mean absolute percentage error and root mean square error of the VMD-ISSA-GRU model are 1.211 8, 1.890 0 and 1.591 6 MW, respectively. Compared with the conventional GRU, long short-term memory (LSTM) neural network, Bi-directional LSTM (BiLSTM) neural network model and other combination models, the prediction accuracy has been significantly improved, which can solve the problem of low prediction accuracy of wind power.

Accurately predicting solar irradiation (SI) is crucial for power scheduling and photovoltaic site selection. With the development of high-performance computing and large-capacity storage devices, data-driven deep learning models have gained widespread attentions in the SI prediction domain. However, the lack of physical interpretability due to the “black-box” nature of deep learning models restricts their credibility in specific scenarios. To enhance the interpretability of the model on the premise of maintaining prediction accuracy and keeping the model structure unchanged, and without increasing computational complexity, a model based on long short-term memory (LSTM) neural network is constructed, demonstrating an 8.07% performance improvement over the conventional neural networks and showing superior outlier handling capabilities. By employing layer-wise relevance propagation (LRP) algorithm, factors influencing the model output are scored from both temporal and spatial dimensions, enhancing the model’s interpretability. The research results indicate that the model possesses good interpretability under the premise of ensuring performance, with historical solar irradiation, time-related features (such as hour, day, week, month), solar altitude information (such as sunrise and sunset times), cloud cover, radiation time, temperature, and dew point temperature being the main factors influencing SI prediction.

In order to realize efficient and accurate detection of the pitch bearing tooth surface of wind turbines in service under the adhesion of high viscosity lubricating grease, profiling array eddy current technology is used to study the effects of different coil arrangement methods and lifting distances on the detection results of bearing tooth surface defects. It can be concluded that, the edge effect range of Z-shaped and composite coil layout is different, and the composite profiling probe is significantly shorter than the Z-shaped probe. By detecting the artificial groove defects of 10.00 mm×0.50 mm×1.00 mm (slot length × slot width × slot depth), it indicates that the lifting distance limits for inner and outer toothed bearings are 1.04 mm and 1.43 mm, respectively. Experimental verification is conducted on the in-service fan bearings under the condition of high viscosity lubricating grease on the surface, and the results of defect size and position detection are accurate, with an error of less than 5%. This provides technical support and new ideas for supervision and inspection of the pitch bearing gear tooth surface in service.