The supercritical carbon dioxide (S-CO₂) cycle power generation technology has become an epoch-making and revolutionary frontier technology in the field of thermal power generation because of its own technical advantages. Due to the very harsh working environment, S-CO₂ is easy to cause corrosion problems of equipment materials. In order to ensure the safe and effective operation of S-CO₂ system, the range of working medium parameters and candidate materials of the system’s key equipment are introduced. The current research status of corrosion behavior of metal materials in S-CO₂ environment are then reviewed. The corrosion mechanism in S-CO₂ carbon environment is elaborated in detail. The influences of temperature, pressure, impurities, flow rate and material composition on S-CO₂ corrosion process are summarized. Meanwhile, the research progress of S-CO₂ corrosion prevention and control technology is introduced. Finally, the shortcomings of existing research and the main direction of future research wereare summarized, so as to provide scientific basis for the safe operation of S-CO₂ recycling system in China.

The blockage and burst failure of steam tubes caused by exfoliated oxide scales is the major risk faced by supercritical boiler in thermal power generations. With the development of advanced ultra-supercritical thermal power technology, especially, more severe oxidation scale problems will carry over into the higher steam parameters thermal power plants. High temperature coating technology shows a new research methods and approaches in solving exfoliated oxide scale problems. It can not only satisfy the performance requirements of heat resistant steel to high temperature steam oxidation resistant in harsh service environment, but also release the temperature limit of currently used heat-resistant steels due to its inadequate oxidation resistance, which has great application potential in the energy sector. The R&D plans of steam oxidation resistant coatings for steam flow parts of ultra-supercritical thermal power units in the EU, the United States and China are briefly described. The current research progress in preparation and service performance of these coatings is emphatically introduced. The basic research and engineering application issues restricting the large-scale application of aluminide coatings in thermal power units are proposed. And the application prospect of high temperature aluminide coating technology for complex heat-resistant steel tubes of ultra-supercritical power plant boiler is prospected.

A concentrated downcomer stub of a boiler drum with 13MnNiMoR steel in a power plant, which was replaced due to cracks and non-metallic inclusions after 14 years in service, was dissected, and the behavior characteristics and influence of the non-metallic inclusion were analyzed through chemical composition analysis, mechanical property testing, microstructure and defect morphology observation. The results show that under service load, non-metallic inclusions become crack sources and microcracks by means of self cracking, interface separation from matrix or hole formation at the end, and microcracks converge to form macro cracks. When tensile and impact tests on the serviced materials, the area without inclusions was cracked and expanded in plastic mode. While innon-metallic inclusions area, the cracks nucleated with non-metallic inclusions and expanded in a brittle mode, resulting in a significant reduction in the strength and plastic toughness of the materials compared with that before service.

The synergy of fireside corrosion and stress is one of the challenges for austenitic steels used in modern fossil-fuel power plants during their service process. The creep rupture tests of Super 304H steel are carried out under static air and fireside corrosion environment at 650 ℃. The stress range is set at 200 to 300 MPa. The creep rupture life and microstructure evolution of different samples were studied. The results show that creep rupture life of Super 304H steel in corrosion condition decreases significantly, compared with that in static air. The rupture life decreases more seriously as the stress decreases, up to 83% at 200 MPa. The complete and continuous corrosion products scale is damaged by fireside corrosion, including the occurrence of cracks and spallation of these surface products. The formation of internal sulfide in the matrix caused by fireside corrosion leads to the deterioration of grain boundaries. Then it tends to crack along grain boundaries during creep rupture tests to accelerate the accumulation of creep damage. The surface of matrix undergoes recrystallization upon to the combination of high temperature and stress due to the loss of alloy elements caused by corrosion/oxidation. The formation of these fine recrystallized grains is unfavorable to creep properties of metals. The ferrite transformation also occurs in the same area during the cooling process after creep tests. Fireside corrosion increases the width of recrystallized grains area, thus expands its influence on the creep rupture life of the alloy. The fireside corrosion accelerates the creep rupture of Super 304H steel by promoting its corrosion process and the microstructure evolution.

The static corrosion behavior of 316L stainless steel and 347 stainless steel at 500 ℃ in Solar Salt (60%NaNO₃ + 40%KNO₃) was investigated via static corrosion test. Corrosion kinetic curves of 316L stainless steel and 347 stainless steel in molten salts at 500 ℃ were obtained through measuring the weight changes of the specimens at each time intervals. XRD and ICP-MS were employed to characterize the phase and component of molten nitrate salts; XRD, SEM/EDS were used to characterize the morphology, composition and microstructure of the corrosion products on the surface and the cross section of corroded specimens. Finally, combining the changes of molten salt and stainless steels, the corrosion mechanism of 316L stainless steel and 347 stainless steel in Solar Salt was discussed respectively. Results showed that the corrosion behavior of 347 SS in Solar Salt at 500 ℃ was characterized by mass gain. As time goes on, the trend of 316L stainless steel increased first and then decreased, while the trend of 347 stainless steel was on the increase. SEM/EDS showed that 347 stainless steel was more likely to be oxidized, while the chromium element in 347 was prone to dissolve, comparing to 316L stainless steel is better stability in Solar Salt, that is, 316L stainless steel is more corrosion resistant.

In recent years, thermal power units have frequently participated in peak shaving to build a new type of power system with new energy as the theme. Accidents of pipeline weld cracking and failure often occur. The welds on both sides of the intersection between the pipeline behind the intermediate pressure bypass valve and the condenser casing frequently crack. The opening area of the muffler pipeline also frequently crack. The heat transfer process from the pipeline behind the medium pressure bypass valve to the condenser muffler is studied by using the finite element method，The distribution of thermal stress under normal and peak shaving conditions was compared. To investigate the causes of the problem, a comprehensive calculation model for the medium pressure bypass pipeline is first established to obtain the distribution of primary and secondary stresses in the pipeline under normal working conditions, as well as the displacement and bearing values of each node. The finite element method is used to study the heat conduction process from the local medium pressure bypass valve to the condenser silencer pipeline. The thermal stress distribution under normal and peak shaving conditions is studied. The results indicate that under peak shaving conditions, the poor atomization effect of the nozzle results in severe water entrainment in the steam, The temperature difference between the pipeline behind the bypass valve and the pipeline of the condenser muffler is larger and repeated operation and shutdown of the desuper heating water cause thermal fatigue fracture of the weld seam and the opening area.

The growing complexity observed in the structures of cast aluminum fittings has posed significant challenges to conventional non-destructive testing techniques, rendering them inadequate in fulfilling the requirements for swift on-site inspection of irregularly shaped cast aluminum fittings. Consequently, an ultrasonic testing method based on flexible phased array probes was proposed. Firstly, a dynamic focusing algorithm for flexible phased array ultrasonic probes was introduced, and the basic simulation theory of CIVA multi-technique software platform was analyzed. Then, the dynamic focusing algorithm used to achieve deflection and focusing of ultrasonic beam was verified by simulation with CIVA, and the parameters of the flexible phased array ultrasonic probes were optimized through simulation. Finally, the effectiveness and feasibility of the testing method were verified through the inspection of typical cast aluminum fittings. The results show that phased array ultrasonic testing technology based on flexible array probes can meet the requirements of outgoing quality control and on-site rapid inspection of cast aluminum fittings with irregular shape.

The recompression carbon dioxide Brayton cycle has the advantages of simple structure and high cycle efficiency. However, the recompression cycle faces the problems of large boiler pressure drop, high cooling wall temperature and difficult waste heat utilization when applied to coal-fired power plants. The partial cooling carbon dioxide cycle can effectively alleviate the above problems when integrated with coal-fired boilers by virtue of its own circulation characteristics. A thermal calculation program for a 600 MW coal-fired power generation system with partial cooling carbon dioxide cycle is written using MATLAB. Firstly, the effect of single parameter variation on the thermodynamic performance of the system is investigated. The results show that the system efficiency is highest when the main compressor inlet pressure and temperature are near the critical point; the system efficiency drops suddenly when the pre-compressor works near the critical point; the system efficiency is highest when the split ratio and reheat pressure are 0.35 and 17 MPa, respectively. The particle swarm optimization is applied to the partial cooling cycle, and the results show that the partial cooling cycle can achieve the efficiency close to that of the recompression cycle under the suitable design parameters. Compared with the recompression cycle, the mass flow rate of the partial cooling cycle decreased by 17.46% and the boiler inlet temperature decreased from 462.45 ℃ to 429.39 ℃.

The Shockley-Queisser (SQ) limit sets an upper limit on the efficiency of conventional semiconductor photovoltaic devices. A thermophotovoltaic system (consisting of a heat source, a spectrally selective emitter and low bandgap photovoltaic cell) can work as an alternative to break this theoretical efficiency limit. To further improve the power generation efficiency of thermophotovoltaic (TPV) systems, an emitter with a multilayer cross structure based on metamaterials was designed in this work. Through optimization of its geometric size, the emitter demonstrates an excellent narrow-band emission spectrum. This effectively reduces the loss of low-energy photons below the bandgap of PV cells and avoids the absorption of high-energy photons that exacerbate lattice vibrations to cause thermal losses. Its application to TPV systems enables a perfect match with In_0.69Ga_0.31As cells with a bandgap of 0.6 eV. Detailed theoretical calculations of this TPV system show that the power generation efficiency can exceed the Shockley-Queisser (SQ) limit (41%) at 1 117 ℃, and will be further improved as the emitter temperature increases. When the temperature reaches 2 000 K, the efficiency is as high as 46.75%. Additionally, the narrowband emitter shows good angular insensitivity in the range of 0~60 degrees.

In order to reduce the cost of fuel procurement, a power plant plans to burn economical coal with low calorific value, such as carbon 3500 and Shenhun 4500.The quality characteristics of the coal to be blended deviate from the coal currently used, which affects the safety, economy and environmental protection of the boiler operation.Through coal quality analysis, laboratory test, theoretical analysis and calculation, on-site pulverizing system optimization test, economic coal blending test and operation parameter optimization test, the technology of economic coal blending combustion of boiler is studiedsystematically .The research results show that the low grindability and serious wear characteristics of the carbon 3500 lead to its poor adaptability to the pulverizing system and the boiler, and the comprehensive power supply cost of the unit increases after blending combustion.The fuel characteristics of Shenhun 4500 are close to the main coal types of the power plant, the operation performance of large proportion of mixed burning boilers is good, the comprehensive power supply cost of the unit is reduced, and the economic benefits are significant.It is suggested that the power plant can determine Shenhun 4500 as an economic coal for long-term combustion.This study can provide reference for power plants with similar demand for mixed combustion.

In order to monitor the condition of the heat recovery steam generator (HRSG) and to ensure the healthy operation of the HRSG, the three-pressure main steam temperature and pressure prediction model was established by using the data from the healthy operation of HRSG and combining the three methods of principle component analysis (PCA), sparrow search algorithm (SSA) and long short-term memory (LSTM). PCA was used to reduce the input parameters of the model from 22 to 9 dimensions, and taking the reheat steam temperature prediction model as an example, it was concluded that the model with PCA dimensionality reduction reduced the hyperparameter optimization time by 11.3% compared with the model without PCA dimensionality reduction. Compared with the model without SSA, the value of coefficients of determination of these models is significantly improved, mean absolute error and root mean square error are significantly reduced, and the alarm threshold of the main steam temperature HRSG is determined according to the distribution of absolute error. Therefore, the condition monitoring model of HRSG based on PCA-SSA-LSTM has short training time and high prediction accuracy, and the model provides theoretical basis and technical support for fault monitoring and diagnosis of HRSG in gas turbine combined cycle power plants.

According to GB/T10184—2015, the calculation model of blast furnace gas boiler efficiency is constructed, and the calculation method of blast furnace gas boiler efficiency is analyzed. The results show that the calculation methods of gas moisture content and low-level calorific value are different due to the difference of gas benchmarks.Three methods for solving the excess air coefficient, actual flue gas volume and CO₂ content in the flue gas are proposed for blast furnace gas boilers, and a correction method for exhaust gas temperature of blast furnace gas boilers with gas heaters is proposed;The calculation of some formulas in the GB/T10184—2015 needs to be further discussed, and appropriate modifications can be made.

A new combined cooling, heating and power system is proposed based on solar photovoltaic, wind power, ground-source heat pump and energy storage unit (WSSH-CCHP) to improve the efficient utilization of renewable energy resources and the entire system energy efficiency. The comprehensive evaluation indexes are developed by using the analytic hierarchy process to account for the system performance of energy efficiency, economy and environment. The mixed integer linear programming (MILP) algorithm is employed to perform the optimization on the selection of equipment types, capacity allocation and system operation stratagem. A case study on an energy center in Jinan city is conducted to explore the optimal performance and operation characteristics of WSSH-CCHP. The obtained results indicate that the proposed system comprehensive performance is much better than the separate production system, which provide useful information for the development of CCHP system with wind-solar-storage and heat pump and the study on its integrated optimization and operation characteristics.

Under the background of the goal of “carbon peak and carbon neutrality”, environmental protection requirements are becoming increasingly stringent, and methanol as a recognized high-efficiency, clean and low-carbon fuel has received more and more attention. In order to analyze the feasibility of methanol for boiler fuel, a comprehensive evaluation model of methanol, coal, diesel and natural gas as boiler fuel was established, and the four indicators of energy saving, environmental protection, economy and sociality were considered through analytic hierarchy process (AHP) and entropy weight method (EWM), and comprehensive evaluation was carried out under five scenarios with different importance of each index. The following conclusions are drawn: the energy saving of methanol is better than that of other fuels, the environmental protection and economy are comparable to natural gas, and the social aspect is second only to coal, which is 3.2 times that of diesel and 2.2 times that of natural gas; in terms of importance, environmental factors first, economic factors and energy-saving factors second, social factors are the weakest importance (scenario 3); the comprehensive evaluation score of methanol as boiler fuel is 0.318 6, which has great advantages compared with natural gas (0.292 9), coal (0.232 4) and diesel (0.156 1).

Aiming at the problem that it is difficult to accurately and timely measure the inlet NOx concentration in the denitrification system of selective catalytic reduction (SCR) in thermal power plants, due to the excessive factors affecting the inlet NO_x concentration and the large delay and inertia of the system, the Max-Relevance and Min-Redundancy (mRMR) combined with Bayesian optimization (BO) algorithm is proposed, optimize the dynamic soft measurement model of NO_x concentration at the inlet of the SCR denitration system of the stacking ensemble model. Aiming at the problem of reduced prediction accuracy of static single model and asynchronous timing of auxiliary variables and inlet NOx concentration in the process of dynamic NO_x generation, the mRMR-BO combined with model was used to screen the auxiliary variables, Copula Entropy (CE) determined the delay of auxiliary variables, the BO combined with model determined the order of auxiliary variables, and TCN and LASSO were integrated by Stacking method. The auxiliary variables containing delay time and order information were used to construct a dynamic stacking ensemble soft measurement model, and the simulation results showed that the root mean square error, average absolute error, and average absolute percentage error of the integrated model compared with TCN and LASSO single networks were the smallest. Compared with the static ensemble model, the dynamic ensemble model has higher prediction accuracy and can achieve accurate soft measurement of the inlet NO_x concentration.

Aiming at the problems of pollution and high carbon emissions caused by island dependence on diesel energy supply, an islanded integrated energy system multi-objective planning optimization method considering carbon emission was proposed. Based on the construction of equipment model, the annual operation of the system was simulated hourly considering the influence of the climate fluctuation on the output of renewable energy devices, the life cycle costs and life cycle carbon dioxide emissions was taken as the optimization objectives, the multi-objective planning optimization model of islanded integrated energy system was constructed by combining with non-dominated sorting genetic algorithm II, the weighted arithmetic averaging operator was used to make decisions on the optimization results. An island area in Yantai was taken as an example, the influence of typical day and annual hourly data as input on planning results, the influence of investment changes in renewable energy devices and natural gas prices, as as well as wind power and photovoltaic installed capacity and battery capacity on optimization objectives were analyzed. By multi-objective planning optimization of the study area, the optimal capacity of each device under different target weights was obtained. The results showed that the configuration of renewable energy and battery can reduce the life cycle carbon dioxide emissions by 26.95% -55.96%. But when the life cycle carbon dioxide emissions weight was increased from 0.6 to 1, the carbon dioxide emissions were reduced by increasing the battery capacity. At this time, life cycle costs increased by 210.13% and life cycle carbon dioxide emissions only decreased by 8.59%. The proposed island integrated energy system planning method provides a reference for decision makers to balance low carbon cost and energy supply economy when planning islanded low carbon IES.

Taking a million kilowatt nuclear power half speed steam turbine generator set as the research object, a dynamic model of spring foundation bearing rotor is established by using the rotor dynamics professional analysis software ARMD. The dynamic characteristics of the shafting are obtained through dynamic calculation and analysis. The accuracy of the calculation model is verified by the coincidence of the field measured critical speed of the shafting and the calculated value. On this basis, the vibration response caused by the thermal imbalance of the seal pad of the generator is calculated. It is found that the vibration changes are mainly concentrated at the rotor of the generator, and the thermal imbalance of the seal pad is only the direct influence factor of the vibration fluctuation of the shaft system, but not the root cause. At the same time, the oil film stress of the seal pad under different operating conditions is analyzed, and it is found that the axial inclination has the greatest impact on the stress of the seal pad. Therefore, the processing and installation process shall be ensured during the maintenance and adjustment of the unit to prevent the shaft system deflection during the operation of the seal pad.

In the actual operation status of dry-type air-core reactor, the focus and difficulty of the fault diagnosis method is to reduce the false alarm rate and the missing alarm rate. About it, this paper proposes a weighted Naïve Bayes state evaluation method for a dry-type air-core reactor. First, a simulation model of a reactor inter-turn short circuit fault is established using multi-physical field coupling, and the effectiveness of the simulation method is validated by constructing a reactor operation test platform. Second, simulation and analysis of reactor current amplitude, current harmonics, impedance angle, and hot spot temperature under multiple operating conditions are performed to obtain the reactor’s normal and known fault sample sets. Finally, a weighted Naïve Bayes state evaluation model is developed using multi-state feature quantities. The example demonstrates that this method is effective for reactor operation state recognition and classification because it has high classification accuracy and requires fewer training samples.

The hybrid gas foil thrust bearings have excellent performance, but few studies have been reported on them. In this regard, a model of this bearings is proposed and a numerical research is carried out for the static and elasto-hydrodynamic characteristics. Based on MATLAB software, a steady fluid-structure interaction method was proposed for the numerical prediction of hybrid gas foil thrust bearings. The foil deformation, static load and frictional torque were calculated and analyzed at various rotating speeds, supply gas pressures and locations of air supply holes. The influences of operating parameters and locations of air supply holes on the static performance of hybrid gas foil thrust bearings were presented. The results show that: increasing the gas pressure has a small effect on the frictional torque, but increases the axial load of the bearing, and increasing the speed will lead to a significant increase in the frictional torque of the bearing. The location of the gas supply hole arrangement has a large effect on the static characteristics of the hybrid gas foil thrust bearings, so the location arrangement should be reasonably selected. The priority is given to the arrangement of the gas supply hole in the tilted area on the basis of meeting the bearing load requirements. The conclusions are of guidance for the design and application of hybrid gas foil thrust bearings.

Taking the gas fuel control valve of gas turbine as the research object, based on the computational fluid dynamics method, the flow field distribution and flow change rule of the gas fuel control valve under the actual operating conditions are studied, and the flow characteristic curve of the valve is fitted. The results show that the mass flow of the control valve at the same opening has nothing to do with the change of the pressure behind the valve, and is in a blocked flow state when the pressure in front of the valve is 2.650 MPa and the pressure ratio behind the valve to that in front of the valve is 0.49~0.78; Under the same pressure ratio, the discharge coefficient is approximately linear with the opening, which is consistent with the actual requirements of the project; There is a linear correlation between the flow coefficient and throat area. By optimizing the valve core profile, the linear curve of throat area with opening is improved, and the linearity of the flow characteristic curve is improved.

During the low load operation of coal-fired units, the SCR denitration catalyst may be deactivated by ammonium bisulfate (ABS). The experimental tests are carried out on this phenomenon and the results show that: 1) with the flue gas temperature below the ABS condensation temperature, the catalyst will be deactivated due to the gradual deposition of ABS in the micropores. The ABS condensation temperature is inversely proportional to the micropore diameter, and the ABS concentration is positively related to the product of NH₃ and SO₃ concentrations in the flue gas; 2) the micropores with pore diameters of 2~20 nm are still the main structure of wide temperature denitration catalyst as well as the conventional catalysts, which cannot change its fate of ABS deactivation under low load; 3) the physical reversibility of catalyst ABS deactivation makes “combination of prevention and treatment” still the fundamental method to solve the ABS problem.

The traditional waste heat valve control technology is mainly divided into two methods, mechanism modeling and data-driven. However, in practical applications, the former is difficult to accurately describe due to the complex mechanism. The latter requires high data quality and full working condition samples, which is difficult to meet in a short time. Aiming at the above problems, a fusion-driven optimization method for waste heat valve control is proposed. Firstly, the mechanism knowledge and data knowledge are fused to construct a knowledge graph model based on fuzzy sets, and the valve opening knowledge is materialized. Secondly, the LSTM valve opening optimization model based on time protection mechanism is established, and the time protection mechanism algorithm is proposed to determine the optimal adjustment frequency of the valve. Finally, the recommended valve opening is obtained by knowledge reasoning. Through experimental analysis and verification, this method integrates qualitative knowledge such as waste heat recovery mechanism and quantitative knowledge such as equipment operation data. While improving the safety of equipment, the probability of generating high-temperature saturated steam enthalpy is increased by 94%, and the average daily increase is 8 640 kJ, which realizes the intelligent decision of waste heat recovery valve opening.

The floating platform undergoes six degrees-of-freedom of motion in the marine environment, making the flow field around the blade fluctuate drastically, and the changing flow field will have a huge impact on the dynamic response of the blade. A two-way fluid-structure interaction simulation of the NREL 5 MW wind turbine was carried out using the CFD-CSD coupling method. Based on this, the UDF technique introduced the floating platform motion to study the blade deformation and the overall torque and thrust changes under the surge, pitch, and yaw motion. The results show that the three typical platform motions of the surge, pitch, and yaw make the blade deformation amplitude increase, and the increase of flapwise and torsional deformation is more significant than that of edgewise deformation; the surge motion has the greatest influence on the blade deformation and aerodynamic performance, the maximum change range of torsional deformation can reach 70%, the peak values of the torque and thrust are increased by 30.51% and 11.75% respectively; the pitch and yaw motions reduce the average torque and thrust.