For the supercritical carbon dioxide (S-CO₂) with heated flow in a horizontal tube, to research the influence of the buoyancy effect on flow and heat transfer characteristics, experiments were conducted on flowing and heating in optical and inner coiled wire tubes under the same condition. Investigations were carried out for the influence of the wall heat flux density and mass velocity on the buoyancy effect, while discussions were given for the influence of the inserted coiled wires on the wall temperature distribution, heat transfer mode, etc. Results show that the temperature stratification caused by the buoyancy effect occurs along the gravity direction during SO₂ horizontal flowing with heating, which leads to the severe wall temperature divergence at the top and bottom, with a maximum wall temperature difference of up to 48 K. The inserted coiled wires in tube can effectively inhibit the temperature stratification caused by the buoyancy effect, while the heat transfer coefficients at the bottom and top are increased by more than 60% and more than 140%, respectively. Based on the validation of experimental results with four heat transfer correlations, it is found that Bishop correlation has the best comprehensive performance.

Steam-water film interfacial energy and mass transfer mechanism of direct contact condensation is the basis for the optimization design of mixing condensers. Taking steam-water film direct contact condensation as the research object, a film interfacial condensation energy and mass transfer model was established based on the volume of fluid (VOF) model. The impact of varying steam and water mass flow rate ranging in 0.002-0.010 kg/s and 0.30-0.83 kg/s respectively, as well as the influence of flow pattern, on the heat exchange of steam-water film direct contact condensation were analyzed. Results show that the heat transfer coefficient increases with the water and steam mass flow rate. The steam mass flow rate has little influence than the water mass flow rate on direct contact condensation. Compared with the parallel flow,cross flow proves to be more favorable for the heat transfer process. Due to the increased interphase force and irregular shape of the water film, the risk of water film breakage increases in the countercurrent flow condition.

To explore the deep peak shaving capacity of coal-fired boilers, the hydrodynamic force and wall temperature characteristics of the water-cooled wall of a supercritical 630 MW boiler were studied. Mathematical models of the hydrodynamic force and wall temperature characteristics were established, and water-cooled wall pressure drop, flow distribution, outlet working substance temperature and wall temperature distribution along the furnace height between 20% and 30% boiler maximum continuous rating (BMCR) loads were analyzed. Results show that, the helical tube sections of the water-cooled wall exhibit small thermal deviation and uniform heat load distribution under 20% and 30% BMCR loads. The outlet steam temperature deviation of the vertical tube sections of the water-cooled wall is large, and the over-temperature is more likely to occur in this area. Under 30% BMCR load, the boiler could operate safely in dry state condition. Under 28.8% BMCR load, the inlet water temperature of the water-cooled wall is 280.0 ℃, and the maximum wall temperature of the water-cooled wall in dry state condition exceeds 450.0 ℃. Under 27.3% BMCR load, the maximum wall temperature of the water-cooled wall in dry state condition exceeds 500.0 ℃, and the boiler should operate in wet state condition or the wall temperature should be reduced by adjusting the inlet water temperature.

Due to the uneven distribution of combustion temperature field in the operation processes of thermal power plants, issues such as over-temperature, tube explosion and flue gas corridor of the furnace heating surfaces may occur. By evaluating the temperature field distribution of the boiler during operation processes, the combustion adjustment can be made to improve the safety, stability and economy of the boiler operation when the operation status can be examined timely. With the boiler of a 660 MW ultra-supercritical power plant as an example, the combustion optimization adjustment test and simulation were carried out. Temperature of heating surfaces and the wall temperature change at the burner were analyzed, and the wind speed and pulverized coal concentration deviations of powder pipes in the pulverizing system, internal and external secondary air volume and intensity of the burner, the adjustment of the direct current air volume, and the wall air in the furnace were measured. Results show that the factors, such as the combination operation modes of different coal mills and the modes of secondary air distribution have a great impact on the boiler operation. In particular, the wall over-temperature, the burner temperature and reducing atmosphere on the heating surface are influenced, which will affect the boiler economic operation. After adjustment, the wall over-temperature phenomenon of the screen superheater, high temperature superheater and high temperature reheater disappears, there is no burnout of burners, and the amount of NO_x generation is also within a reasonable range.

Reheaters are key equipment in nuclear power units used to increase turbine power and reduce component corrosion, and the shell-stream steam axial flow inhomogeneity has a significant impact on efficiency and safety of the units. In this regard, a one-dimensional distribution numerical and simulation model of the reheater was firstly established to verify the steady state and the accuracy of the flow step dynamics under different operating conditions. Considering that the distribution of steam circulating in the reheater had a strong flow inhomogeneity along the tube length, the flow and heat transfer of steam inside and outside reheater tubes were simulated under different flow deviation coefficients. Results show that under the rated condition, the change of circulating steam outlet temperature is inversely proportional to the flow distribution, and as the flow deviation coefficient increases, the temperature distribution becomes more uneven; the outlet enthalpy and dryness of reheat steam in each tube section are less affected, but the probability of subcooling at the outlet of reheat bundle decreases with the increase of flow deviation coefficient. In addition, the low power operation of equipment makes the outlet of reheat bundle more susceptible to subcooling, and the influence of flow inhomogeneity increases.

Aiming at PI^λ controller of fractional order model for hydroturbine system, the steady domains of the governing parameters of k_p and k_i were calculated under different orders of λ based on the boundary between real roots and complex roots. The regular pattern of the domain was analyzed. Bounded by the domain, the specific parameters of k_p and k_i were seeked under the premise of preset for the cross-over frequency ω_c and phase margin φ_m using frequency domain analysis method so as to reach the expected traceability and control robustness of the PI^λ controller of fractional order model. Simulation calculation results show that the control effect of the method is good. Compared with the swarm intelligence solutions based on integrated time and absolute error, it is easy to realize through configuration due to the analytic formula of the method, thus site application can be realized by programmable logic controller (PLC) or distributed control system (DCS).

In order to solve the problems of low speed and low accuracy of rolling bearing fault diagnosis caused by the inconsistent sampling frequency of the accelerometer of mechanical vibration monitoring system, a rolling bearing fault diagnosis method based on variational mode decomposition-multi-strategy tuna swarm optimization-extreme gradient boosting (VMD-MTSO-XGBoost) at wide sampling frequency was proposed. Firstly, the vibration signal was de-noised by wavelet and de-sampled to get the de-noised signal at wide sampling frequency. The de-noised signal at wide sampling frequency was processed by variational mode decomposition (VMD), and the intrinsic mode function (IMF) component index was extracted to form the fault feature vector. Secondly, the Circle chaotic map was used to initialize the tuna swarm optimization (TSO) population to increase the richness and diversity of the initial population. In order to improve the ability of the algorithm to jump out of the local optimum and enhance the ability of the algorithm to explore the whole world, the dimension-by-dimension mutation method was used to disturb the optimal individual position. Finally, the modified tuna swarm optimization (MTSO) algorithm was used to optimize the parameters of extreme gradient boosting (XGBoost), and the rolling bearing fault diagnosis model was established. The proposed fault diagnosis method was validated by the Case Western Reserve University dataset, the German University of Paderborn dataset and the measured dataset. Results show that at wide sampling frequency, the fault diagnosis method presented in this paper can identify rolling bearing faults more efficiently and accurately compared with the other three models.

To enhance the gear fault identification accuracy under variable speed operating conditions, a variable speed gear fault identification method was proposed based on adaptive time-varying comb filtering (ATVCF) and improved arithmetic optimization algorithm (IAOA) for optimizing stack denoising auto encoder (SDAE). Aiming at the noise reduction of vibration signals of variable speed gear, the ATVCF was used to preprocess the data so as to filter out noise components and retain the effective signals. Aiming at the shortcomings of AOA algorithm in global search and local development, cosine regulation factor was introduced for improving the mathematical optimizer acceleration (MOA) function so as to increase the global search ability and local development full optimization ability. Random opposition-based learning (ROBL) was introduced to increase the population diversity of the algorithm, enhancing search ability. In addition, the parameters of IAOA-SDAE model were optimized to ensure fault identification accuracy and stability of the model. The analysis of the vibration test data of the variable speed gears verifies the effectiveness and superiority of the proposed method in the intelligent identification of the variable speed gear fault.

Based on the mature energy technologies, a industrial chain for achieving carbon neutrality in energy industry was presented by complementary integration of new energy generation, electrolytic water hydrogen production, biomass oxygen-enriched combustion, methanol synthesis, methanol reforming and other technologies. The chain can improve renewable energy consumption, achieve zero carbon emission of the whole process, realize long-distance storage and transportation of hydrogen, and reduce dependence on oil. A scenario prediction study was conducted for this industrial chain. From the perspectives of carbon neutral methanol production, oil substitution, carbon emission reduction, carbon neutral methanol production cost, comparative analysis was conducted by setting three influencing factors, such as scale of energy production, energy utilization rate of hydrogen production by electrolytic water, energy utilization rate of methanol synthesis by hydrogen.

The processes of flue gas flow, heat transfer, water vapor condensation, and SO₂ and NO removal of the flue gas condensation method were all numerically simulated. To confirm the impact of the technology on flue gas temperature reduction, flue gas resistance, water vapor condensation, and removal of dust, SO₂ and NO, performance test of the flue gas condensation method was carried out under the rated working condition. Results show that, based on ultra-clean flue gas emission, the flue gas condensation method can effectively remove SO₂, NO, dust, and other pollutants from flue gas in addition to recovering water from flue gas, further enhancing the environmental performance of thermal power plants. Compared with the performance test results, the numerical simulation results of flue gas condenser outlet temperature, water vapor condensation rate, and NO removal rate are basically consistent with the performance test data, and the deviation of flue gas flow pressure loss data is about 9.9%, and the deviation of SO₂ removal rate data is about 14.7%, which are within the acceptable range for engineering.

To address future large-scale uncertainties in long-distance power delivery and safe economic grid connection of new energy, it is necessary to promote the efficient joint operation with new energy and flexible energy storage to meet the channel capacity requirements, while considering the flexible retrofitting of thermal power. Taking a large-scale renewable energy base in northern China as an example and considering the randomness and volatility of wind and solar energy, a multi-energy complementary capacity configuration optimization model was constructed based on the joint probability distribution of wind and solar energy using the Copula function. The improved sparrow search algorithm was used to solve the optimal capacity configuration scheme, and simulation analysis was performed for typical days in summer and winter. The influence of pumped storage power stations with different installed capacities on the volatility of thermal power units, system costs, operating conditions and environmental benefits was compared. Results show that the multi-energy complementary power generation system can both improve operating conditions and enhance the economy of operation, with significant environmental benefits.

An operational optimization method was proposed for coal-fired power plant integrated with carbon capture system considering load following performance. The method was based on a steady-state model and a closed-loop dynamic model of the integrated system. Various performance indexes including fuel costs, maintenance costs, carbon emission penalty costs and power load following deviation penalty costs were considered to optimize the electric and carbon operation output set-points. Results show that the proposed method can reduce the short time-scale power load following deviation penalty cost by 25.86% and the overall system operating cost by 0.57% compared with the conventional methods, achieveing a coordinated and flexible operation of the coal-fired power plant integrated with carbon capture system.

A dynamic model of the combined cooling, heating, and power (CCHP) system of solid oxide fuel cell (SOFC) and micro gas turbine (MGT) coupled with solar energy was established to study the effect of input-side energy fluctuations on the distributed energy system. The effects of direct solar radiation fluctuations on system key parameters were analyzed, and the influence of external load fluctuations on system performance was studied. Results show that, compared to the CCHP system without solar energy coupling, the new system, which uses solar energy to preheat air, reduces fuel consumption by 1%, increases cooling and heating outputs by 17% and 9%, respectively. The integration of trough solar collector (PTC) in the system smooths out the changes in system power generation efficiency with power load and shifts the point of maximum power generation efficiency to the right, which is conducive to increasing the power of the system.

From the perspective of gas turbine blade cooling design, the study and application progresses of data-driven methods of domestic and foreign researchers in recent years was summarized. Three types of data-driven methods including mathematical statistics, machine learing and deep learning were introduced. The advantages of data-driven methods over experimental and numerical simulations were expounded. And the application of data-driven methods was emphatically summarized, mainly including predicition and uncertainty quantification of turbine blade cooling characteristics, improvement of turbulence models in numerical simulation, and data fusion of existing data and knowledge. Based on the current research hotspots and development tendency, further studies focus on data-driven methods in gas turbine blade cooling design were proposed, including exploring the potential of data fusion approches, improving generalization ability, reducing data cost, studying data processing methods, comparing the advantages and disadvantages of different data-driven methods, and developing data-driven approaches for complex cooling designs.

A study was conducted on the modification of SGT5-2000E gas turbine by blending natural gas fuel with hydrogen rich synthesis gas. The blending ability of hydrogen-rich synthesis gas in this type of gas turbine was analyzed, and modification measures were proposed to address technical issues caused by H₂ and CO in hydrogen-rich synthesis gas. The performance parameters of the gas turbine unit before and after blending were compared. Results show that this type of gas turbine can mix up to volume fraction of 50% hydrogen rich synthesis gas. When blending 50% hydrogen rich synthesis gas, the performance parameters of the gas turbine meet the design requirements, and the relevant modifications and improvement measures have achieved the expected results, improving the operational flexibility of this type of gas turbine unit and providing reference for similar blending research.

A turbine with high cycle fatigue failure was used as the simulation model, the coupling method of three-dimensional unsteady flow field and solid vibration response analysis was adopted, the simulation of fault point was carried out. According to the different conditions of turbine expansion ratio and turbine reaction force, the law of aerodynamic load distribution and aerodynamic exciting force caused by aerodynamic state change was compared, at the same time, the relative variation trend of blade vibration stress was obtained. Results show that under unchanged intake conditions, the average exciting force, the amplitude of exciting force and the vibration stress of the blade increase obviously with the increase of the expansion ratio of the turbine. While the turbine reaction force increases, the average aerodynamic exciting force of the blade increases obviously, but the amplitude of the exciting force and the vibration stress have a downward trend.

To investigate the rectification effect of perforated plates in the inlet system of a compressor test rig with sudden expansion flow, four sets of perforated plates were designed. Effects of the porosity in the core region of sudden expansion flow (referred to as central region) and pore distribution on the mixing process between the wake flow of multi-hole orifices and main flow were studied using numerical simulation method. Results show that increasing the porosity of central region leads to insufficient flow distribution at the periphery of plates. When the opening rate of the central region increases to 1.46 times of upstream and downstream cross-sectional area ratio of the sudden expansion, the proportion of flow distribution in the central region reaches 1.88 times of its area ratio. Consequently, the wake vortices near the wall and corner of plenum chamber merge and elongate, whose length reaches 17 to 24 times of the pore spacing. To suppress the increase and elongation of wake vortices near the wall and corner, it is advisable to select the opening ratio in the central area equivalent to the upstream and downstream cross-sectional area ratio of the sudden expansion. Reducing the pore spacing is the most effective method to shorten the length of wake vortices behind the central region.

Influence of hole configuration including cylindrical, fan-shaped and laidback fan-shaped holes on effusion cooling performance under different pressure drops of cooling air was examined using infrared thermal imaging technology. Results show that due to the vortex impact effect, low local cooling efficiency areas appear on the wall surface, which are independent of the hole type. The change in hole type only affects the cooling effect of the wall surface. Increasing the pressure drop of the cooling air can improve the cooling effect, and the area of the low cooling effect zone also decreases accordingly. The difference between the cooling hole shape and the pressure drop of the cooling air causes the movement of the lowest cooling effectiveness position on the wall. As the velocity of cooling air increases, this point moves upstream. In terms of the uniformity, the minimum effectiveness of cylindrical holes is lower by 14.3% to 27.5% than the area-averaged one. The difference between the minimum cooling efficiency of the fan-shaped hole, the expansion hole and the average level is greater, and the uniformity of the cooling effect is worse. The comprehensive cooling efficiency of the expansion hole is the highest, but the uniformity is the worst.