For the analysis of the heat applied to equipment outside the system boundary, the energy utilized was outside the GB/T 10184 standard, and the boiler efficiency calculation could not take advantage of the existing standard. The external heat loss of hot air was divided into two categories: hot air reuse and hot air non-reuse. Based on the GB/T 10184 calculation framework, the calculation methods of these two categories of external heat loss of hot air were proposed. Taking a 350 MW boiler as a practical example, under the same load, continuous operation of hot air external use and shutdown of hot air external use were compared. According to the actual test data and analysis results, the calculation method was used to compare the actual operating conditions. The influence of external loss of hot air on boiler efficiency was analyzed. The results showed that the test results of combustible materials in two working conditions were basically the same. The external loss of hot air in T01 (cold air recovery) was 0.82%, the external loss of hot air (cold air nonrecovery) was 0.13%, and the external loss of hot air in T02 was 0. The measured boiler efficiency in T01 and T02 conditions was 93.10% and 94.00% respectively. The operation of external hot air system reduced the boiler efficiency by about 0.9 percentage point.

To solve the problem of excessive air leakage from the four-compartment air preheater, a four-compartment rotary air preheater of a 1 000 MW power plant is used as the study object to investigate the thermal characteristics, rotor thermal deformation and air leakage of the air preheater, by combining theoretical analysis with numerical simulation. The numerical simulation results show that, for every 1% increase in air leakage rate of the 1 000 MW unit, the heat transfer efficiency of air preheater will be reduced by 1.13%, and the power plant will consume 3 604 tons of standard coal more on average per year. There are large temperature gradients in the axial and circumferential directions inside the air preheater, and most of the corrosion and deposition areas are distributed in the low temperature section. There are large differences in rotor thermal deformation during different operating conditions of the air preheater, and the maximum thermal deformation occurs on the secondary air side. It is necessary to make corresponding adjustments according to the thermal deformation characteristics of different positions of the rotor when setting the sealing system.

Creep rupture is one of the most common failure modes of pipelines used in thermal power plants. Residual life prediction is an effective guarantee to ensure the safety, utilization and benefit maximization of equipment. Based on the creep rupture test data of 2.25Cr-lMo heat-resistant steel in actual service for over 200 000 hours, the selection principle of TTP parameters and its influence on the accuracy of life prediction are analyzed by comprehensively considering the working stress and TTP parameters. The relationship curve family of Z-parameter method is used to characterize the vertical dispersion of pipeline durability data in different power plants. The stress-TTP-reliability curve for evaluating the reliability of life prediction is established, and the relationship between the predicted life of different power plant pipelines and the working state of the unit is obtained. The creep residual life of different power plant samples at 540 ℃/45.26 MPa is 1.725 6×10⁵ h and 3.378 8×10⁵ h respectively, and the predicted reliability reaches 99%, which provide maintenance suggestions for the operation reliability of power plant equipment.

For the purpose of absorbing renewable energy, the coal-fired power units are required to operate flexibly, and the resulting variable operating environment will lead to large nonlinearity and uncertainties of the wet desulphurization process. Particularly, the time delay will make the control even harder. Therefore, in order to achieve a more flexible control structure, a new desulphurization control strategy based on frequency retrofit is proposed. Based on the strategy, a dynamic model is obtained through field experiments. Meanwhile, in order to deal with uncertainty well and achieve safe compensation of uncertainty in the control process, an updated Gaussian process model predictive control method for time-delayed objects is proposed, and the performance of the method is demonstrated by parameter analysis and simulation experiments. Finally, the effectiveness of the proposed control strategy and control method is verified by field application.

The effects of tray parameters on desulfurization efficiency and energy consumption of desulfurization towers are investigated. Through the large-scale hot test platform, the effects of different pore diameters, opening ratio, opening form, weir plate height and different installation positions on desulphurization efficiency and energy consumption are studied. In this paper, the energy consumption efficiency ratio is proposed for the first time as an index to evaluate the operation economy of desulfurization tower. It is found that, under the conditions of experimental platform, when the liquid-gas ratio is not more than 13.6 L/m³, it is economically advantageous to choose sieve plate with medium aperture, high weir board, small opening rate, low-level arrangement, and new aperture design. When the liquid-gas ratio is large than 13.6 L/m³, it is economically advantageous to choose sieve plate with medium aperture, high weir board, large opening rate, high-level arrangement, and new aperture design. The conclusion is of guiding significance for the design and selection of sieve plates for desulfurization and desulfurization towers.

The fault early warning of the coal mill is of great significance to the safe operation of thermal power unit, but the operation of the coal mill has many interference noises and a high degree of coupling, which makes the fault early warning more difficult. Based on this, this paper proposes a fault warning method based on wavelet packet transform (WPT) and Transformer. Firstly, the signal is denoised by the wavelet packet analysis method with adaptive threshold value. Then, the characteristic parameters related to the fault measurement point are selected as input to establish a Transformer coal pulverized prediction model based on the self-attention mechanism. Finally, the kernel density estimation method is used to analyze the prediction deviation and determine the warning threshold. Taking a 660 MW medium-speed coal mill as the research object and using actual data for verification, the experimental results show that the prediction accuracy of the proposed method is higher than that of CNN, LSTM, and CNN+LSTM models, and it can provide early warning of coal mill failures.

The long-term vibration of ZGM133G-I type medium speed coal pulverizers in a power plant causes weld fatigue fracture of the powder delivery pipeline, which results in coal powder leakage, polluting the environment and seriously affecting the operation of the unit. Based on the mechanical vibration analysis and field test of medium-speed coal pulverizers, this paper studies the influence of operating parameters such as loading force, speed of separator and output of coal pulverizers on the vibration of coal pulverizers. The results show that, the vibration of medium-speed coal pulverizers is mainly caused by the mechanical equipment itself and the setting of operating parameters. The size and separator type of coal pulverizers are not the inevitable factors that cause the vibration of coal pulverizers, but the wear and damage of mechanical structure will cause the vibration of coal pulverizers. In order to reduce the vibration of medium-speed coal pulverizers, it is necessary to comprehensively consider the output of coal pulverizers and the fineness of coal powder according to the test results, and reasonably control the loading force, separator speed and output.

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.