Regarding tube burst issue of boiler superheater tube bundle during service, a full three-dimensional modeling and structured mesh discretization of the final stage superheater tube screen of a power plant boiler were carried out based on supercomputing platform. The Reynolds average Navier-Stokes simulation method and Lagrangian two-phase coupling model were used to systematically simulate the steam flow characteristics and oxide scale particle accumulation behavior inside the superheater tube screen. Effect of load change and oxide scale particle exfoliation on the steam flow distribution of the superheater tube screen was explored. Results show that the steam flow rate of the tube bundle with throttle holes is 5.63%-11.23% lower than that of other normal tube bundles without considering the thermal deviation on the flue gas side. The maximum flow rate deviation of the same tube screen reaches 6.3%, and locates in coiled tube bundle (tube bundle 17). The difference in steam flow velocity at the outlet of different tube bundles of the same tube screen under four load conditions ranges from 10.3% to 11.7%, which can lead to significant difference in the power of transporting oxide scale particles in different tube bundles. When the particle size increases from 500 μm to 2 000 μm under different conditions of oxide scale exfoliation in tube bundles, the probability of particle accumulation increases by 15% to 20%. Both of the maximum positive and negative deviation of flow rate for each tube bundle on the same tube screen exceed 6.6% under the condition of simultaneous exfoliation of oxide scale in the four tube bundles, which should be considered in the superheater design process.

To address the issue of large steam temperature deviation at the vertical water-wall outlet of a 1 000 MW ultra-supercritical double-tangential circular boiler under low load operation, the water wall was equivalent to a flow network system, and a mathematical model for hydrodynamic calculation was developed. Using the measurement data of the experimental furnace under 400 MW load, the actual heat absorption deviation distribution in the furnace was repeatedly back-calculated and iteratively calculated, and the precision of the model was validated. Through analysis, the asynchronous dry-wet state transition during low-load operation was revealed to be the cause of the outlet steam temperature deviation, and relevant operation countermeasures were proposed. Two throttle adjustment schemes were designed, hydrodynamic characteristics after throttle orifice adjustment were calculated, and the flow instability was checked. The results show that with the two adjustment schemes, the outlet steam temperature is more uniform, the outlet steam temperature deviation is reduced, and no flow instability occurs. After adopting the second throttle adjustment scheme, the overall outlet steam temperature of the four walls is more uniform, and the improvement effect on the outlet steam temperature deviation of the four walls is better.

A numerical simulation was conducted on the outlet velocity deviations of air-powder pipelines for different coal mills of a 1 000 MW ultra-supercritical once through boiler using computational fluid dynamics software. The influence of pipeline layout on the outlet velocity deviations was analyzed, and the effect of coal particle size, air-coal ratio and inlet air temperature on the outlet velocity deviations in air-powder pipelines was investigated. Results show that longer pipelines exhibit higher along-route losses compared to shorter ones, resulting in outlet velocity deviations. Moreover, as coal particle size distribution becomes more dispersed, internal flow disturbances in air-powder pipelines increase, leading to escalating along-route losses and decreasing outlet velocity deviations. Decreases in air-coal ratio and inlet air temperature also increase coal concentration in the pipeline, further enhancing along-route losses and reducing outlet velocity deviations.

Targeting ash deposits on the platen superheater of a 660 MW boiler firing Xinjiang high-alkali coal, a high-temperature visual imaging system was established to acquire real-time ash deposition images. Ash deposition images were preprocessed through grayscale conversion, grayscale linearization, and Gaussian filtering, and quantitatively evaluated via peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM). An enhanced image dataset was constructed through image augmentation techniques. Leveraging the correlation between deposit thickness and thermal resistance, a convolutional neural network (CNN)-based monitoring model was developed for ash deposit identification. Results show that the CNN method achieves effective real-time monitoring of ash deposit status on operating platen superheaters, with accuracy, recall, and F_score reaching 98.8%, 98.2%, and 98.8% respectively.

To address the issue of unbalanced air-powder distribution in primary air ducts at the outlet of coal mills in a direct-fired pulverizing system, based on cold and hot-state air velocity balancing tests in primary air ducts, numerical simulations were conducted on the two-phase flow of air and powder in medium-speed coal mills and primary air ducts of a 700 MW supercritical coal-fired power unit. The influence of uneven air-powder distribution inside the coal mill and inherent resistance differences in the ducts on air-powder distribution at the outlet were studied, and the balancing performance of adjustable orifices was investigated. Results show that asymmetric entry of primary air into the coal mill causes unbalanced air-powder distribution in four zones corresponding to the primary air ducts before the separator during actual operation. The maximum relative deviation in air volume distribution is 7.8%, and the maximum relative deviation in powder volume distribution is 23%. When air-powder distribution before the separator is uniform, the maximum relative deviations in hot-state air and powder distribution are 11.26% and 9.12%, respectively. When air-powder distribution is uneven, these deviations become 11.14% and 16.78%, respectively. Inherent resistance differences in the ducts are the primary cause of air volume deviations, while the combined effect of uneven coal powder distribution inside the mill and inherent duct resistance differences leads to powder volume distribution deviations in the outlet primary air ducts. Without an effective powder distributor installed in front of the primary air ducts, adjustable orifices have limited ability to balance powder volume distribution in the outlet ducts, making it difficult to achieve simultaneous balance of air and powder distribution.

Taking a large wet cooling tower of a 1 000 MW unit as the research object, a 3D numerical calculation model of the three-zone synergistic efficiency enhancement pattern was established based on partition water distribution, non-equidistant fillings layout and dry-wet hybrid rain zone, and the accuracy of model was validated. Meanwhile, researches were emphatically conducted on the effect of the three-zone synergistic efficiency enhancement pattern on the thermal and resistance performance of the wet cooling tower under variable operating conditions. Results show that the thermal and resistance performance of the three-zone synergistic cooling tower is significantly superior to that of the conventional cooling tower under variable operating conditions. Within the study range of circulating water flow rate, tower inlet water temperature, air dry-bulb temperature and air humidity, after adopting the three-zone synergistic efficiency enhancement pattern, the water temperature drop is increased by 0.63-0.72 K on average, the cooling efficiency is increased by 3.66-4.11 percentage points on average, the Merkel number is increased by 0.16-0.20 on average, and the ventilation rate is increased by 10.54%-10.91% on average.

The differentiation patterns of pulverized-coal minerals into fly ash and bottom ash in power plant boilers were investigated using heavy liquid float-sink separation. By separating the pulverized coal, fly ash, and bottom ash into density fractions of 1.3-2.4 g/cm³, X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM) were used to analyze the composition and morphology of each density sub sample, and the generation of liquid phase at different temperatures was calculated. Results show that pulverized-coal particle density is ≥1.3 g/cm³, and the yield of particles with density of 1.5-<1.8 g/cm³ is as high as 40.3%. The density of fly ash is concentrated at ≥1.7 g/cm³, with a density component content of up to 37.7% for densities ≥2.4 g/cm³. Bottom ash particles lies mostly in 2.1-<2.4 g/cm³. In boilers, coal minerals first form varying-sized ash particles based on their states, where particles below 10 μm become fly ash, those above 50 μm settle as bottom ash, and those between 10 and 50 μm may collide. Fusible ones in this intermediate size range coalesce and grow into bottom ash.

To address the issue of stray radiation signals interfering with measurement accuracy in radiation thermometry of gas turbine combustors, a physical model was established that accounts for emissivity, high-temperature residual wall reflections, and high-temperature gas absorption/radiation. An error correction model for determining true temperatures was subsequently developed. Quantitative sensitivity indexes of model input parameters were analyzed across three distinct operational bands of an infrared thermal imager. Results show that even in spectral bands with high gas transmittance, gas influence remains non-negligible. Neglecting gas effects causes maximum relative errors of 9.7% and 5.5% for short-wave infrared (SWIR) and mid-wave infrared (MWIR) imagers, respectively. Sensitivity indexes of input parameters vary across operational bands. Parameters with lower sensitivity indexes can tolerate greater measurement uncertainties, whereas those with higher indexes require precise measurement.

Current research primarily employs size or shape optimization to enhance the thermo-fluidic per-formance of conventional cylindrical pin-fin cooling systems. However, topology optimization methods can more comprehensively unlock the potential of pin-fin cooling. This study implements level set-based topology optimization on cylindrical pin-fin configurations to improve heat transfer and pressure loss characteristics in cooling channels. Results show that the optimized flow-disruption elements evolve into droplet-shaped structures downstream of pin-fins. These bio-inspired geometries accelerate flow velocity along the streamwise direction while suppressing low-velocity wake regions. Consequently, the Nusselt number demonstrates a monotonic increasing trend along the flow path, and the optimized configuration achieves peak heat transfer intensity with minimal pressure penalty, yielding the best thermo-hydraulic performance.

Supercritical carbon dioxide (S-CO₂) cycle has advantages as high efficiency, compact structure, and short working fluid flow path, and can meet the requirements of rapid peak regulation and deep grid peak regulation in power grid. However, in practical applications, the performance and stability of the S-CO₂ cycle largely depend on the mechanical properties, corrosion resistance and oxidation resistance of superalloy materials. Firstly, the material selection of high-temperature heat exchanger for the S-CO₂ cycle was introduced. Secondly, the morphology characteristics of the oxide films of ferritic-martensitic alloys and austenitic stainless steels in the S-CO₂ environment were introduced, and the experimental research methods for oxide film failure were analyzed. Finally, the prediction model for the failure of oxide film was introduced. Results show that the material selection criteria for the S-H₂O cycle may also be applicable to the S-CO₂ cycle system under similar temperatures and pressures. Alloy heat exchangers in S-CO₂ environments will undergo oxidation-carbonization reactions. The carbonization phenomenon occurring at the oxide film/alloy interface will aggravate the failure of the oxide film.

Special-shaped heat exchange tubes have received extensive attention in the research field of heat exchangers due to their performance advantages such as low flow resistance and good heat transfer efficiency. In order to assist better application of special-shaped tubes in engineering field, numerical simulation method was used to simulate wet gas condensation heat exchange flow field outside the tubes of elliptical tubes, semi elliptical tubes, and flat tubes with six different ellipticities within a certain range of inlet parameters. The variation law of the external condensation heat transfer performance of the special-shaped tube with ellipticity was analyzed by using such parameters as the comprehensive performance parameter J_F and the moisture evolution coefficient ζ. Then, attempts were made to apply three kinds of special-shaped tubes with an ellipticity of 0.5 respectively to a certain circular tube flue gas condenser, and the heat and mass transfer performance of the special-shaped tube flue gas condenser was obtained based on the numerical simulation results. Results show that the comprehensive performance of the three types of special-shaped tube flue gas condensers is better than that of the circular tube flue gas condenser. Among them, the J_F value of the semi elliptical tube flue gas condenser is 10.95% higher than that of the circular tube flue gas condenser, and the ζ is 6.04% higher. Its condensation heat transfer performance is the best.

High-temperature characteristics of CaO grain cluster system were studied by using molecular dynamics (ReaxFF-MD) simulation method of the ReaxFF reaction force field. Influence mechanisms of temperature and H₂O and CO₂ atmospheres on the CaO grain agglomeration process were explored, and sintering mechanism of CaO was revealed by tracking the evolution of grain boundary structure and chemical bond changes. Results show that at high temperatures, CaO microcrystals form structurally ordered polycrystals through crystal surface contact, and then form clusters through "contact neck". The contact neck gradually grows under the action of material flow migration, and the clusters are sintered into structurally disordered nanoparticles. Increasing the temperature can accelerate the migration of CaO cells and atoms, promote the integration of the cells, change the grain accumulation state and the clusters tend to be spherical, and intensify the sintering. The atmosphere of H₂O and CO₂ has little influence on the accumulation state of CaO cells after agglomeration and sintering. Compared with CO₂ atmosphere, H₂O has little influence on the agglomeration rate of CaO cells. Temperature is the key factor determining the agglomeration and sintering of CaO microcrystals. When H₂O, CO₂ and CaO microcrystalline clusters come into contact, chemical reactions are highly likely to occur. And the hydrogen ions generated by the dissociation of H₂O continuously combine with lattice oxygen and diffuse into the interior of the clusters, affecting the structure of the cluster and resisting agglomeration. While CO₂ is adsorbed on the surface of CaO, reducing the surface energy. At the same time, its products hinder the bonding of CaO microcrystals and slow down the sintering process.

In order to enhance the flexibility and voltage stability of wind farms facing external uncertainties, a multi-scenario reactive voltage optimization control strategy based on self-adaptive model predictive control (MPC) was proposed. A reactive voltage prediction model was established using sensitivity matrices, and scenario segmentation was conducted based on evaluation criteria derived from short-term wind speed forecasts. The control objective was to minimize voltage deviations and active power losses at multiple time points within the prediction horizon. Adaptive adjustment of weight ratios in various scenarios facilitated rolling optimization. Crawfish optimization algorithm (COA) was employed to solve the optimization model and derive reactive power optimization schedules. Feedback correction based on optimization results and prediction errors was implemented. Simulation was conducted using a wind farm in the "Three-North" regions of China. Results show that compared with traditional open-loop control and MPC, the proposed strategy reduces daily average voltage deviations by 82.46% and 67.74%, respectively, validating the feasibility and effectiveness of this control strategy.

In order to improve the efficiency of solar PV/T systems, baffle plates and swirl devices were added to the cooling channels of an air-cooled PV/T system to enhance heat transfer. A numerical model was established, and the influence of air flow resistance was comprehensively considered. The effects of such factors as mass flow rate, number of baffle plates, swirl intensity on the actual electrical efficiency and comprehensive efficiency of PV/T systems were analyzed. Results show that with the increase of the mass flow rate of the cooling air, both electrical efficiency and thermal efficiency gradually increase, but the increase rate decreases. When the mass flow rate increases from 0.01 kg/s to 0.05 kg/s, the electrical efficiency rises by approximately 0.65 percentage rates.The actual electrical efficiency and the actual comprehensive efficiency of the PV/T system first increase and then decrease with the increase of the air mass flow rate. When the air mass flow rate is 0.02 kg/s and 0.04 kg/s, the actual electrical efficiency and the actual comprehensive efficiency reach the maximum values respectively. Adding a swirl fan to the channel chamber can effectively improve the comprehensive efficiency of the system. When the swirl intensity is 3, the overall efficiency of the PV/T system can reach 79.09%. Under the same swirl intensity, the lifting effect of swirl on low inlet mass flow systems is more obvious compared with that under a high mass flow.

To address the technical challenges of deep participation of coal-fired power plants in grid peak shaving, coupled energy storage systems can effectively improve the operational flexibility of the units. Two solutions for coal-fired power plant coupled with liquid carbon dioxide energy storage system driven by an electric motor or by a steam turbine were proposed, respectively, and the optimal solution was selected through comparative analysis. In addition, peak shaving performance analysis, exergy analysis and economic analysis were conducted on the optimal coupled system. Results show that the coupled solution driven by steam turbine has better performance, with the system round-trip efficiency of 61.85%, and the peak shaving depths of charging and discharging processes are 9.57% and 6.14%, respectively. The exergy efficiency of the optimal solution is 76.61%, the dynamic investment payback period is 5.01 a, and the net present value is 21.053 2 million yuan.

To obtain the influence of feed water flow rate, coal supply flow rate and other parameters on the load cycling capacity of the subcritical unit, a dynamic thermal system model was established and verified by taking a 300 MW unit as an example. Under 75% load working conditions, the change trends of drum pressure and temperature, main steam pressure and temperature, and unit power generation in the thermal system were studied after the feed water flow rate was reduced by 2.5%-10.0% and the coal supply flow rate was increased by 2.5%-10.0%, and the temporal and spatial distribution characteristics of heat storage in the thermal system were obtained. Results show that when the feed water flow rate decreases or the coal supply flow rate increases, the drum water level drops, the steam production of the evaporation system increases rapidly, and the output power of the unit increases. In the subcritical unit, the heat storage of the drum boiler accounts for more than 90% of the entire thermal system. Taking the lowest drum water level of 100 mm as the safe operation boundary, the total heat storage of the thermal system decreases by a maximum of 9.2 GJ when the feed water flow rate decreases, and decreases by a maximum of 9.4 GJ when the coal supply flow rate increases. During the evolution of the heat storage of each part, the heat storage in the drum has the largest change amplitude, and the heat storage change accounts for about one-third of the total heat storage, which has the potential to increase the load cycling rate by 1.85%/min.

In order to consume more renewable energy, thermal power units have been operating under wide load condition for a long time, and the frequent load changes have caused some difficulties in superheated steam temperature control. Taking the superheated steam temperature of a 1 000 MW ultra-supercritical unit as a research object, the differences of its dynamic characteristics under different loads were analyzed. Meanwhile, an observer-based proportional-integral-derivative (OB-PID) control structure was proposed to enhance the stability of superheated steam temperature of the unit in wide load operation, which was characterized by multi-model and nonlinearity. Simulation results show that, compared with the conventional PID control, OB-PID control not only can maintain better tracking performance, but also can improve the disturbance rejection performance and robustness of the system. In addition, OB-PID control has an extremely simple structure, and the improvement based on PID framework does not add additional signal measurement points, which has a great potential application in flexibility retrofit of thermal power units.

The dynamic simulation model for a closed air Brayton cycle system was established to analyze the dynamic response characteristics of the inventory control method under variable load processes with different storage tank volumes. The study comparatively investigated the system dynamic response patterns during load reduction process using bypass control, inventory control, and combined bypass-inventory control strategies. Results show that the storage tank volume constrains the maximum load adjustment depth of inventory control, where larger tank volume enables greater load variation range. Under 75% and 50% load targets, the combined control strategy achieves faster load reduction rate of 18.71% and 16.57% respectively compared to inventory control, while achieving higher cycle efficiency of 20.81% and 37.66% respectively compared to bypass control. Bypass-inventory combined strategy exhibits excellent load tracking capability, effectively enhances both efficiency and flexibility of load reduction regulation and achieves complementary advantages of different control approaches.

In order to solve the problem of low prediction accuracy of traditional modeling methods in establishing a prediction model for the main steam temperature (MST) of incinerators, a waste incinerator MST prediction method based on improved gray relevance analysis (IGRA) and convolutional-long short-term memory (CNN-LSTM) neural network was proposed. Firstly, DCS variables with high correlation degree with MST were selected by IGRA. Secondly, principal component analysis (PCA) was applied to extract principal component features containing most of the information of the incinerator combustion image. Then, based on IGRA and particle swarm optimization (PSO) algorithms, the delay between DCS parameters and the MST was estimated and compensated. Finally, a CNN-LSTM model with the input of time series matrix composed of DCS variables and image features was constructed to predict the change trend of MST in the next 6 minutes. Results show that compared with the existing MST prediction model, the proposed model reduces the mean absolute error M_AE by 13.07%, reduces the root mean square error R_MSE by 13.89%, and improves the determination coefficient R² by 13.08%.

In order to improve the accuracy of predicting gearbox oil temperature by using supervisory control and data acquisition (SCADA) with multivariate long time series, and solve the problem of inconsistent data distribution caused by different wind power generation units under different operating environments, a method for gearbox condition monitoring was proposed based on multi-branch time series prediction and transfer learning. Firstly, the original sequence was formed by filtering input parameters with extreme gradient boosting (XGBoost) algorithm, so as to obtain the seasonal and trend sequence through decomposing. Secondly, the feature extraction module of seasonal and trend sequence was proposed to obtain the feature of seasonal and trend sequence, which was fused with the feature sequence processed by Informer model and then input into the multi-layer perceptron to map into the final prediction value, so as to construct the proposed multi-branch time series prediction network (MBFN). Finally, the health index of gearbox was constructed by using transfer learning combined with one-class support vector machine (OCSVM) model and sliding window, so as to complete the condition monitoring of gearbox. Experimental results show that the MBFN from proposed model has significantly improved the prediction accuracy of oil temperature, which is better than the conventional time series prediction model. Meanwhile, the adopted migration strategy can adapt to the distribution of different data with less data, so as to realize the condition monitoring of gearbox, while the proposed model can issue the gearbox fault warning with 18.9 days in advance.

In response to the national "dual carbon" policy, so as to reduce carbon dioxide emissions from coal-fired power plants, the co-combustion of coal and ammonia has received widespread attention. Based on molecular dynamic simulation, researches were conducted on the changes in the types and quantities of coal-ammonia pre-pyrolysis products at different temperatures, and the migration pathways of nitrogen element during pre-pyrolysis and combustion processes, so as to obtain the influence mechanism of pre-pyrolysis temperature on NO_x emissions. Results show that, the increase of pre-pyrolysis temperature leads to the decrease of NO_x emissions during combustion. Due to the increased temperature can enhance the interactions between coal and ammonia during pre-pyrolysis, the production of CN and HCN increases with the increase of pre-pyrolysis temperature, and the conversion of hydrogen atoms in coal into H₂ is promoted by the interactions between coal and ammonia. Meanwhile, the increase of pre-pyrolysis temperature can promote the pyrolysis of NH₃ to produce N₂, reducing the nitrogen sources available for NO_x formation. The reduction in NH₃ content decreases the generation of HNO, thereby lowering NO_x emissions. Additionally, the increase of pre-pyrolysis temperature can promote the production of H₂. The presence of H₂, on the one hand, can consume a large amount of O₂, reducing the formation of NO_x during combustion, on the other hand, can accelerate the conversion of HNO to N₂, thus reducing the generation of NO from HNO decomposition.

To enhance the operational flexibility of coal-fired power plants, a molten salt thermal energy storage system that utilizes electric heaters for heat storage and an additional steam turbine for heat release, including heat release schemes A (additional steam turbine exhaust entering the condenser) and B (additional steam turbine exhaust entering the deaerator), were designed. The thermodynamic performance of the integrated system was analyzed based on a 660 MW supercritical coal-fired power plant (CFPP) case study. Results show that in scheme B, the maximum net output power increment of the CFPP is 9.67% of the rated load, while in scheme A, the net output power increment of the CFPP is 11.04% of the rated load. Under the condition of maximum boiler feedwater split mass flow rate, the total energy efficiency of schemes A and B decreases from 43.61% to 43.05% and 42.81%, respectively, while their total energy efficiencies could increase from 42.83% to 44.90% and 44.47%, respectively. When boiler feedwater split mass flow rate is less than 60 kg/s, the equivalent round-trip efficiency of scheme B is higher than that of scheme A, with a maximum value of 48.47%.