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.

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).

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.

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.

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.

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.

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 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 ℃.