The main technical optimization principles of the Ansaldo AE94.3A EVO2+ gas turbine-generator set was introduced. A comparative technical analysis was conducted to explain the energy-saving and economic benefits of the unit, while the localization application of the AE94.3A EVO2+ gas turbine-generator set and accessories was discussed. Results show that, the energy saving, emission reduction, and economic benefits improvement of the AE94.3A EVO2+ gas turbine-generator set are remarkable. Due to some of the gas turbine components are domestically designed and manufactured, and the maintenance of the gas turbine has also achieved full independence, the overall cost of the entire units over the whole life cycle is significantly reduced.

In order to solve the rotor winding in-ter-turn short circuit in a turbine generator, an online diagnosis method based on multivariate state estimation technique (MSET) was proposed. The state matrix was built by using sliding window and Euclidean distance. The exciting current and reactive power calculation models were constructed based on MSET. According to the average value of the relative deviation or residual value between the operating value and the calculated value of the generator, an online diagnosis method for rotor winding in-ter-turn short circuit fault was constructed, and the operation data of a steam turbine generator was used for verification. Results show that, the proposed online diagnosis method is feasible, which meets the requirements of rotor winding in-ter-turn short circuit fault diagnosis, and reduces the probability of fault misjudgment.

The steam turbine shaft gland system of high temperature gas cooled reactor demonstration project (HTR-PM) was introduced. The causes of shaft gland steam supply failure were analyzed, and three solutions were put forward: residual steam of steam generator and pipe supply shaft gland, auxiliary electric boiler to shaft gland steam supply pipe transformation, high temperature air supply shaft gland. The three solutions were compared, while their advantages and disadvantages in cost, reliability and operation limitation were analyzed. Results show that above three solutions are feasible. The research results provide a reference for solving the problem of shaft gland steam supply failure of HTR-PM steam turbine.

Off-line washing of compressor can eliminate the scale deterioration and improve the unit performance, and the off-line washing period has a significant impact on power plant operation income. An economic analysis method and model of gas turbine off-line washing period was presented. The average washing cost of period was taken as the optimization index, and the optimal off-line washing period was proposed. Based on the model, the optimal off-line washing period of the unit in Hainan Province was calculated, and the sensitivity of each boundary condition was analyzed. Results show that, the optimal off-line washing period for the unit is approximately 740 h, which can increase the profit by 84 000-180 000 yuan per year compared with the actual operation of 550 and 1 200 h. Factors such as fuel price, on-grid price, and compressor scaling rate all have significant impacts on the optimal washing period. The model has been applied in power plant, and the research results can provide a reference for the off-line washing period decision of other gas turbine power plant compressor.

Taking two typical F-class gas-steam combined cycle units of GE 9FA and Mitsubishi M701F as the research objects, a thermal model of gas-steam combined cycle with inlet gas heating design was established, and a simulation calculation for the thermal performance of unit was carried out. A univariate analysis was conducted on the effects of the environmental temperature, heating temperature rise, and unit load on the unit performance, while a comparative analysis was conducted on the improvement of inlet gas heating efficiencies of two types of units under different unit loads. After which, the optimal intake parameters under different unit loads were given. Results show that, under the same inlet gas heating condition, the efficiency improvement of 9FA unit is higher than that of M701F unit, and the unit combined cycle efficiency increases with the increase of heating temperature rise. Under the same heating temperature rise condition, the optimal environmental temperature for inlet gas of 9FA unit is higher than that of M701F unit. Research results have important reference significance for the application of inlet gas heating technology in F-class gas-steam combined cycle units.

Taking a wind turbine generator set (WTGS) with abnormal noise as the research object, vibration pulse signals generated during operation were obtained through using a dual-channel vibration detection instrument, and analyses were conducted according to the sequence of signal transmission based on simple sound localization method. A comparison between the vibration frequency of abnormal noise and the oscillation frequency of tower was carried out, and the source of abnormal vibration was investigated by vibration tests. Through comprehensive analysis and test for vibration, it is finally confirmed that the exact vibration source with abnormal noise is at the tower bottom of WTGS. The fault has been found successfully with simple sound localization method, and this can provide a practical and feasible technical way for the design optimization and operation stability improvement of WTGS.

To solve the problem of the cracking failure of the fillet weld at extended side wall outlet header in an ultra-supercritical boiler of a power plant, comprehensive analyses were conducted on the cracking failure reasons of the fillet weld from the aspects of material chemical composition, microstructure, hardness tests and service condition, while optimization measures were synthetically proposed based on welding process, heat treatment process and weld form. Results show that, the header material is 12Cr1MoVG, and the chemical composition, microstructure and hardness of the leaked header fillet weld all can meet the requirements of standards. The complex additive effects of welding residual stress and service stress result in the cracking failure. The service time can be prolonged by adopting the optimization measure of reducing the concentrated stress in fillet weld. This can provide an important reference for the daily supervision and quality control of similar boiler tubes in power plants.

In addressing six failure cases involving non-critical pressure metal components in coal-fired generating units and gas-steam combined cycle units of power system, the failure cases were analyzed through a combination of macroscopic observation, material analysis, microstructure analysis, and mechanical property analysis with the service environment of the units. Results show that, the failure locations of components are often found at stress concentrations with abrupt sectional changes, and the main causes for failure are identified as external environmental corrosion and fatigue damage. Misuse of material or inadequate control of production process leads to poor microstructure quality and a decrease in overall macroscopic mechanical properties and accelerates component failure. As non-critical pressure components of the shaft, auxiliary bolts or other equipment in generator sets are not given adequate technical supervision and management attention, leading to significant issues such as the misuse of materials or inferior material quality.

For a gas-steam combined cycle unit with long-term shutdown and standby, the flow resistance of flue gas was increased by the tarnishing of rear heating surface finned tube with outer helical fins in the waste heat boiler, which further leaded to the abnormal start-up of the gas turbine. Researches were conducted on the influence of the surface tarnishing status of finned tube on the flow resistance characteristics through on-site data monitoring, numerical simulation, and experiment in a small test bench. Results show that, the flow resistances of No.5 and No.6 models in the waste heat boiler rear flue increase significantly. The main reason of the increase of flow resistance is not the rust accumulation in leeward side of the finned tube, but the increase of rust thickness in both sides. After the rust removal, the flow resistance characteristics can be improved with the thinner fins and the enlarged cross-sectional area, and which are better than those of new finned tubes.

For the No.3 bearing with large amplitude vibration in a 25 MW turbine generator, the problem of abnormal vibration was not be solved after maintaining in several times, which resulted in the shutdown of the turbo-generator set. Through analyses on the operation parameter, vibration spectrum, bearing structure and maintenance process of the turbine generator, it is confirmed that the main reason of large amplitude vibration is the change of centering, which is caused by the friction between the sinking generator rotor and the shaft seal and oil shield with the loosening of support system due to the false connection of the supporting bracket at bearing bottom. By means of optimizing the centering adjustment process for rotor and adjusting the assembling clearance for bearing, the vibration amplitude of No.3 bearing is reduced significantly, which can guarantee the safety and stability of the unit operation. The reasonable maintaining and assembling method for rotor is vitally important for the reliable operation of turbine generator.

Boiler water circulating pump (BCP), as the core equipment of the start-up system of ultra-supercritical boiler, plays an obvious role in the unit start-stop efficiency, regulation characteristics and low-load safety, and can better adapt to the needs of deep peak regulation of power grid. Through the comparison of domestic and imported BCP in terms of price, delivery and quality guarantee period, domestic BCP has obvious advantages. With the increase of domestic demand for peak regulation of thermal generating units and the promotion of power generation equipment localization, the market demand for domestic BCP has become increasingly prominent. At present, there is still a gap between domestic BCP and imported products in application performance, but with the expansion of market demand, it has a certain development prospect.

For two types of advanced and efficient impulse blade profiles (LH, LL blade profiles) in steam turbines, analyses were conducted on the multi-stage air-medium stage test and numerical simulation, so as to research the overall performance difference between the two types of impulse blade profiles in real stage environment. Results show that, the simulation values of air flow rate with two types of impulse blade profiles basically coincide with the test values, while the LH blade profile has a higher through-flow efficiency. In addition,the simulation values of the optimal speed ratios of two types of impulse blade profiles are both higher than the test values. Finally, with the increase of the speed ratio at the root, the reaction degree at the root of the through-flow stage gradually increases, and the simulation value of reaction degree is higher than the test value. The design concept of LH blade profile is more reasonable than that of LL blade profile, and the effect of performance improvement can satisfy the expectation. Research results may provide an important reference for the engineering application of LH blade profile.

For a thermal power unit, analyses were conducted on the main influence factors of each system in steam turbine on the economy under deep peak regulation condition, and researches were emphatically carried out for the operation economy of steam turbine-driven feedwater system and steam distribution system. The differences of unit operation economies with different steam sources for steam turbine-driven feedwater pump were calculated and analyzed based on EBSILON modelling platform, the operation economy indexes of the unit under different main steam pressure conditions were quantitatively calculated, and the influence of the adjustment of the butterfly valve in interconnecting pipe on the economy was analyzed. Results show that, the economy of the fourth stage steam as the steam source is better than that of cold reheated steam, and the steam turbine heat rate would be increased by 123.7146.5 kJ/(kW·h) when adjusting the steam admission of steam turbine-driven feedwater pump with the butterfly valve in interconnecting pipe. The unit operation economy can be improved by the appropriate decrease of main steam pressure under deep peak regulation condition.

For the defect of insufficient control ability of energy storage battery when participating in primary frequency modulation of thermal power generating unit, an adaptive comprehensive control method was proposed to optimize energy storage battery output based on primary frequency modulation characteristics and the state of charge (SOC) of energy storage battery. By analyzing the frequency modulation characteristics of the power grid, the virtual inertia control was improved to get the virtual negative inertia control. In the early stage of frequency modulation, the energy storage battery output was mainly based on droop control and supplemented by inertial control. In the frequency recovery period, it was mainly based on the inertial control and supplemented by droop control. In order to optimize the power output of energy storage battery, an adjustment strategy of adaptive output coefficient was set based on logistic function to maintain a good state of SOC. Taking a typical single region power grid as an example, a MATLAB/Simulink simulation model was built to verify the proposed adaptive comprehensive control method, Results show that, the control strategy can reduce the frequency deviation quickly and effectively, and make the power system quickly recover to steady state value of primary frequency modulation frequency.

For a boiler high temperature reheater with long term service after 46 000 hours in a 660 MW ultra-supercritical unit, researches were conducted on the microstructure and mechanical properties of the leaked TP310HCbN steel tube by means of metallography test, scanning electron microscopy, tensile property test and impact property test. Results show that, the aging grade of the leaked TP310HCbN steel tube microstructure after long term service at high temperature is 3-4, and the tube material presents a serious embrittlement property with a large mount of carbide precipitating at the grain boundary, which result in the insufficient toughness of the tube material. A large number of micro-cracks are formed on the surface of outer tube by impacting, after which, the tube cracks gradually expand and eventually lead to leakage with the increase of service time.

For a coal-fired power plant chimney with a height of 210 m and an outlet diameter of 7 m, the diffusion process of water vapor in the environment was calculated based on Ansys Fluent software to analyze the impact of different factors on the diffusion of plume. Results show that, the increase of ambient temperature and the decrease of flue gas temperature and humidity can significantly reduce the volume of plume. Wind speed and flue gas velocity have a minor impact on the volume of plume, while affecting the vertical and horizontal distribution of the plume. The increase of wind speed causes water vapor to diffuse to a greater distance at lower altitudes with higher concentration. The increase of flue gas velocity promotes the droplet diffusion in the vertical direction.

In order to analyze the influence of the gap between the rotary air preheater grid plate and the heat exchange component on the exhaust gas temperature, for a 330 MW power station boiler rotary air preheater, two models of equal resistance and equal flow velocity were established to calculate the exhaust gas temperature with different gaps between the grid plate and the component, while the exhaust gas temperatures of the air preheater with different gap values were obtained. Results showed that, when the gap value is less than 6 mm, the influence on exhaust gas temperature is slight, and when the gap is more than 12 mm, the influence on exhaust gas temperature is greater. Through a comparison between calculation results and actual operation parameters, the maximum relative deviation of exhaust gas temperature is 2.73%, which verifies the accuracy of the proposed calculation methods.

Through on-site simulation frequency disturbance tests and real frequency disturbance tests of the power grid, the primary frequency control performance of new energy stations in East China receiving-end power grid was tested. Results showed that the new energy stations can ensure sufficient reserve power through active power reserve function, so as to meet the requirements of primary frequency control of the power grid, while the frequency control characteristics of photovoltaic power plants are better than those of wind farms in terms of rapid response, stability and power contribution. Research results can provide a reference for setting differentiated parameters between wind farms and photovoltaic power plants in East China power grid.

The impeller root groove of nuclear steam turbine is a stress corrosion susceptible part, which should be subjected to nondestructive testing periodically. However, in actual testing, the impeller root groove is tested in an environment with complex structure and restricted space, and the testing results are difficult to reflect the real situation of the root groove surface. Therefore, an ultrasonic phased array inspection scheme was proposed for the inspection of the impeller root groove of nuclear steam turbine. The impeller-root body specimen with artificial defects was processed according to 1∶1, and the test equipment and sweeping method were determined by CIVA simulation platform. Meanwhile, the defects were detected for four times on the specimen. Experimental results show that the scheme can identify all artificial defects and realize the localization and quantification of defects, while which has a high detection accuracy and feasibility. The safe operation of nuclear steam turbine can be effectively ensured with this technology.

There were problems such as reduced unit efficiency, blocked air preheater and excessive ammonia escape during deep peak regulation in the ultra-clean emission process of a 300 MW thermal power generating unit. The cold and hot state mapping test was carried to evaluate and diagnose the inlet flow field and the NO_x concentration in outlet section of the selective catalytic reduction (SCR) denitrification system, and the application scheme for the efficient operation of the system was proposed. Computational fluid dynamics (CFD) software was used for numerical simulation, and the solution was demonstrated by cold state physical model. The results of engineering practice application show that, the collaborative optimization can achieve a good flue gas flow distribution and maintain a low pressure drop in the denitrification system. The velocity relative standard deviation of the catalyst inlet in the first layer is reduced to 10.79%, the total pressure drop of the denitrification system is less than 600 Pa, and the net coal consumption is reduced by 0.3 g/(kW·h), which has better energy saving and emission reduction benefits.

The control mode of the high-pressure bypass control valve and the automatic switching mode of its adjustment object were studied under the condition of steam turbine tripping without boiler shutdown of a supercritical double-extraction back-pressure heating unit. Multistage pulse control technology was used to realize the full stroke control of the high-pressure bypass control valve. Results show that,the steam turbine trip signal is used to automatically trigger the adjusting object switcher of high-pressure bypass control valve, which can realize the non-disturbance switching of the main steam and the reheat steam as the steam supply source. At the same time, the steam turbine trip signal is used to trigger the rapid load reduction of the boiler, which can realize the overall safe and stable operation of the unit. This research realizes the function of stable steam supply of the unit under the condition of steam turbine tripping and boiler operating.

In order to improve the accuracy and stability of feature extraction of the core high temperature region of boiler flame, a method of extracting the contour of flame core high temperature region based on Mask R-CNN (mask region-based convolutional neural network) was proposed in combination with the flame characteristics of tangential-fired boiler. About 10 000 frames of historical operational flame images from the industrial flame monitoring system of a 330 MW coal-fired boiler were used for modelling, and the flame images of uploading conditions were processed and verified online. Results show that, the accuracy of core high temperature region detection based on Mask R-CNN model reaches 92.35%, which has higher stability than traditional threshold segmentation method and edge detection method. The Mask R-CNN model can better adapt to the characteristics of the fluctuation and rapid change of the pulsating flame when the load changes, and the contour edge is less affected by other regions, which is conducive to the extraction and calculation of the flame geometry and distribution characteristics for the contour of the flame core high temperature region.

In order to reduce the transportation costs and meet the requirements of hoisting assembly and transportation, the large plate girders of 660 MW and above boilers generally need to be designed in blocks manner in height and length directions to form a segmented superposed beam, while high-strength bolts are applied to the connection in height and length directions. Taking a specific engineering of a 660 MW boiler in Guizhou Province as the research example, based on GB 50017—2017 Standard for Design of Steel Structures in China and ANSI/AISC 360-16 Specification for Structural Steel Buildings (LRFD method) in America, design methods for the flange splicing, web splicing, and laminated surface splicing connections of the segmented superposed beam were presented. For high-strength bolts used in segmented connections, the single bolt bearing capacity calculated by American standard is relatively greater, and there is less demand for the number of bolts, while Chinese standard tends to be more safe. For the plates used for segmented connections, the stress coefficients calculated by American standard are lower than those calculated by Chinese standard. For the design of large plate girder segmentation, the safety levels of above two standards are basically the same, while the Chinese standard is slightly more conservative. Research results provide a reference for the connection design of segmented superposed beam of boiler steel structures.

Taking a PG9351FA gas turbine combined cycle unit as the research object, the unit model was established based on Thermoflex software. The performance of unit under full load and constant load conditions was calculated respectively, and the key parameters of the system were analysed. Results show that, compared with the full load condition and the constant load condition, the increase of ambient temperature has the same effect on the efficiencies of steam turbine, waste heat boiler and combined cycle, but the difference on the efficiency of gas turbine is significant. When the combined cycle unit is operating under constant load condition, a suitable low-grade heat source can be used to improve the inlet air temperature of the gas turbine, so as to improve the efficiency of the gas turbine. At the same time, the back pressure of steam turbine can be reduced to improve the performance of steam turbine by cold end optimization and other measures.

In view of the low power generation efficiency of refuse-fired generators set with mid-temperature and mid-pressure, the quality and efficiency improvement measures such as upgrading main steam parameters, adding reheat cycle and waste heat recovery and utilization device were researched. A 15 MW refuse-fired generators set was selected to analyse, according to mid-temperature and sub-high pressure scheme and mid-temperature, sub-high pressure and reheating scheme respectively, the performance parameters and economic benefit after transformation were analysed. Results show that, after the application of mid-temperature and sub-high pressure technology scheme, the mass of boiler heating surface increases by 9%, the power generation efficiency increases by 1.52 percentage points, the waste power generation increases by 43 kW·h/t, the transformation cost is about 20.05 million yuan, the cost of pipes replacement increases by 6.57 million yuan, the internal rate of return is 17.47%, and the investment payback time is 6.31 years. After the application of mid-temperature, sub-high pressure and reheating technology scheme, the mass of boiler heating surface increases by 24%, the power generation efficiency increases by 2.35 percentage points, the waste power generation increases by 64 kW·h/t, the transformation cost is 24.90 million yuan, the cost of pipes replacement increases by 13.63 million yuan, the internal rate of return is 21.53%, and the investment payback time is 5.15 years. The research results can provide some reference for the application of reconstruction engineering for refuse-fired generators set with mid-temperature and mid-pressure.

Based on the investigation and analysis of the imported hydraulic actuator of gas fuel control valve in gas turbine, and combined with considerable experience in use and design, a 100% domestically produced hydraulic actuator for gas turbine gas fuel control valve has been newly developed. The principle design of the hydraulic actuator of gas fuel control valve was emphatically introduced, and the frequency response of the hydraulic actuator was simulated and analysed by building a simulation model. After which, the reliability verification and multiple performance tests were carried out for the hydraulic actuator with an established test system. Simulation and test results indicate that, the performance of the domestically produced hydraulic actuator for gas turbine gas fuel control valve is superior to that of the imported actuator in many aspects. The successful development of hydraulic actuator sample for gas turbine gas fuel control valve has broken through the localization problem.

To investigate the influence of random variables, such as structural dimensions, material property parameters, and temperatures, on the equivalent stress of steam turbine rotor during material preparation, processing, installation and operation, taking the high pressure rotor in a 300 MW class steam turbine as the research object, the time and location of the maximum equivalent stress during cold start-up was obtained by calculating with finite element method. Meanwhile, combined with the randomness of variables, the relationship between the rotor maximum equivalent stress and the random variables was fitted with both of polynomial response surface method and support vector regression (SVR) response surface method, and analyses and comparisons were conducted on the fitting effects of above two methods. Additionally, the reliability of rotor equivalent stress and the sensitivity of various random variables during cold start-up process were investigated by Monte Carlo simulation method, while the sensitivity index order of six random variables including rotor radius, was determined. Results reveal that the fitting effect of SVR response surface method is better than that of polynomial response surface method, and the strength reliability indexes of above two response surface methods for the cold start-up curves are 96.99% and 94.16%, respectively. Among the six random variables, the elastic modulus of rotor material is identified as having the most significant impact on the equivalent stress of steam turbine rotor.

The spiral tube of the water wall of a supercritical boiler was leaked in many places. After sampling the leakage tube, the macroscopic examination, chemical composition, metallographic structure and tensile properties were analysed. Results show that, the original leakage point is located in the fusion zone of the water wall tube fin weld, which is caused by a large number of welding defects in the fin weld. The leakage of steam water blows adjacent pipe. The adjacent pipe appears multiple secondary leakage points, and the medium flow rate in adjacent pipe is reduced, resulting in short-term overheating in the downstream area of the secondary leakage points. It is recommended that the welding quality of fin welds should be strictly controlled and checked.

The no load commissioning test should be conducted on an industrial back pressure steam turbine after manufacturing stage according to technology agreement, while there is a distinct difference between the commissioning tests of back pressure and condensing steam turbines from the aspects of process and scheme. Combined with an actual application, researches were carried out for the process and scheme of no load commissioning test of the back pressure steam turbine, and key and difficult points of actual commissioning test were analysed. This may serve as a reference for the no load commissioning test in similar back pressure steam turbines.

Adiabatic compressed air energy storage system has the characteristics of large capacity, long-term performance, safety, stability, and flexibility. In this type of energy storage system, the heat exchangers, as key components, have particularly important impact on system efficiency. Therefore, by establishing an adiabatic compressed air energy storage thermal system model, the impact of heat exchanger final temperature difference and air side pressure drop on system efficiency was analysed, and the cost of heat exchangers was comprehensively evaluated. Results show that, the increase of the upper final temperature difference of heat exchangers can lead to a decrease in system efficiency, and the lower final temperature difference should be matched with the upper final temperature difference in practical engineering design. Compared to high-pressure heat exchangers, the air side pressure drop of low-pressure heat exchangers has a greater impact on system efficiency. The smaller the final temperature difference and pressure drop of the heat exchangers, the higher the system efficiency, but the higher the equipment cost. Therefore, there is an optimal combination of final temperature difference and pressure drop to minimize the cost of the heat exchangers while meeting the system efficiency requirements.

To address the issue of large heat absorption deviation between the left and right of the high-temperature superheater in a 660 MW boiler, an initial attempt was made to apply the self-correcting method used in another boiler of the same power plant. This involved studying the relationship between the damper opening deviation of the separated overfire air (SOFA) and steam temperature deviation. When this approach did not achieve the expected results, the failure causes were further analysed. By coupling the SOFA damper horizontal swinging angle and opening deviation, the relationship between these factors and the steam temperature deviation on the left and right of the boiler was established successfully. Results show that, adjusting the SOFA damper horizontal swinging angle can effectively change the thrust distribution on the left and right of the furnace incircle. Adjusting the opening of SOFA dampers on the upper three layers, it is found that when the opening of the left dampers increases and the opening of the right dampers decreases, the heat absorption increases on the left side and decreases on the right side, which makes the steam temperature deviation between the two sides of the superheater decrease firstly and then stabilize gradually with the adjustment of SOFA damper opening deviation. The implementation of the self-correcting optimization control system, which couples the SOFA damper horizontal swinging angle and opening deviation, successfully achieves self-correcting control of the boiler steam temperature.

In response to the problems existing in the original deep coupled waste heat utilization system of a 660 MW coal-fired unit, the reasons for the failure to achieve the design goals of the system were analysed. Four optimization and renovation schemes were strategically adopted, including the optimization of bypass flue, the optimization of water intake position for condensate heat exchanger, the optimization of recirculation pipeline and adding a water side bypass for the flue gas cooler. The final optimization and renovation effect was calculated and analysed in detail. Results show that, after the optimization, the proportion of bypass flue gas volume increases to 13.5%, the inlet water temperature of the condensate heat exchanger can be stabilized at 70 ℃ for a long time, and the steam consumption of the auxiliary steam heat exchanger is basically reduced to 0. After optimization, the system is put into operation to reduce the net coal consumption rate of the unit by 2.73 g/(kW·h).

The method of statistical analysis for the reliability of nuclear power units was proposed, and the meaning and computational formula for five reliability characteristic quantities of nuclear power units were introduced. The weighted arithmetic means of reliability characteristic quantities of nuclear power units were presented, while following items of 1 000 MW class nuclear power units in China and America from 2008 to 2022 were given, namely the statistic results of reliability, the calculation results of weighted arithmetic means of reliability characteristic quantities, and the change curves of reliability characteristic quantities. Results show that, for 1 000 MW class nuclear power units in China, the availability, reliability and maintainability in general, all present a trend of increase, while the equivalent availability factor of 1 000 MW class nuclear power units from 2008 to 2022 in China is 1.81 percentage points higher than that in America.

To meet the requirements of increasingly stringent standards for nitrogen oxides (NO_x) emission, the lean-premixed combustion mode is widely applied in heavy-duty gas turbines for power generation. With the application of this technology, the flame temperature can be reduced, so as to decrease the NO_x emission. To verify the combustion mode control system in an F-class heavy-duty gas turbine, based on the mechanism model of simplified chemical reaction for natural gas combustion, a network module library for chemical reactor was established, and a simulation research was conducted on the switching process of combustion mode. Based on the modelling technology of Simulink model diagram, a dynamic modelling for the dramatic changing process such as ignition and burn out is realized. Through simulating, it is verified that the established model can accurately reflect the influence of flow distribution ratios of different fuel nozzles on the combustion temperature and emission component, while the real-time simulation with a lower computational expense for combustion mode switching can be realized.

For a heat and power cogeneration unit, analyses were conducted on energy efficiency characteristics based on adaptive multi-level filtering fuzzy C-means (FCM) algorithm with the optimal clustering number. Through improving the traditional clustering algorithm, an adaptive optimal clustering method was proposed based on multi-level strict screening mechanism, so as to obtain the energy efficiency characteristics of unit under different load conditions. The curves of unit operation characteristics were fitted by least squares method, while comparisons and analyses were carried out based on the surfaces of unit operation energy efficiency characteristics from Newton interpolation algorithm. Results show that, the unit performances have certain differences with different external constraints. From the surfaces of energy efficiency characteristics, the difference between the energy efficiency characteristics of two units under different loads and the load condition with a better operation performance of each unit can be visually displayed. Under the condition of 225 MW electric load and 72.5-88.5 t/h heat load (heat-supply steam mass flow rate), the net coal consumption rate of No.1 unit is higher than that of No.2 unit, and with the increase of heat load, the difference in coal consumption rate firstly increases and then decreases. Therefore, No.2 unit can be prioritized to operate under low load condition.

In a continuous feeding fixed bed furnace, researches were conducted on the influence of simulated rural solids with different component proportions on the producing characteristics of pyrolysis gas and tar. Experimental results show that, compared with single component, the pyrolysis of rural solid waste with mixed components is more conducive to promoting the sufficient cracking of materials, reducing the tar production, and improving the cold gas efficiency (CGE) when the pyrolysis temperature is 800 ℃. The pyrolysis with mixed components can reduce the content of O element and corrosivity of tar, while the presence of chlorine-containing substance (polyvinyl chloride in this paper) could effectively promote the decomposition of functional groups containing N or S element in pyrolysis tar, which ensures that tar has a higher heat value and a better stability. The pyrolysis with mixed components is effective in reducing heterocyclic and alicyclic compounds in tar, but the proportion change of chain compounds and aromatic compounds is related to the component proportions of simulated rural solid waste.

For a wind power tower barrel manufacturing project, a research was conducted on the flux-cored arc welding with CO₂ gas shielding (FCAW) process of Q420NE thick plate butt joint for door frame of wind power tower barrel, and the Q420NE thick plate welding procedure was evaluated. Additionally, through solid wire control group experiments, the influence of different shielding gases on the solid wire gas shieled welding was analysed. Results show that, the FCAW process meets the welding procedure requirements for Q420NE thick plate and can be used for the tower barrel door frame welding. For solid wire gas shielded welding, the type of shielding gas has a significant impact on the welding of Q420NE steel, and welding Q420NE steel with pure CO₂ gas cannot ensure that the weld meets the technical requirements.

By using optical microscopy (OM), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), and multi-phase separation technology, a research was conducted on the precipitates along grain boundary of HT700T alloy tubes after thermal exposure. Results show that, the precipitates along grain boundary under etching condition appear as flocculent clusters, which are significantly different from precipitates within grain. The precipitates along grain boundary has already appeared after thermal exposure at 500 ℃, while the quantity of precipitates increases with an increase of temperature, reaching a peak value at around 750 ℃, and then gradually decreases until completely dissolving and disappearing at 1 000 ℃. The precipitates along grain boundary are composed of Cr-rich phase, γ' phase, and γ matrix phase, and the volume fraction of γ' phase in grain boundary micro region is higher than that within grain. Through observing different regions in the creep rupture specimen at a high temperature of 700 ℃, no evidence has been found that the precipitates along grain boundary promote the creep cracking of sample, but the stress has a certain effect on promoting the precipitation along grain boundary.

At present, selective catalytic reduction (SCR) is widely used for flue gas denitration in coal-fired power plants. SCR reactor is the main equipment for flue gas denitration treatment, and its design scheme directly affects the flue gas denitration performance. The SCR reactor is subjected to various loads and effects during operation, and the conventional design usually adopts a conservative frame form, which has limitations in material utilization and stress performance. In order to achieve high-performance design of SCR reactor structure, the stress characteristics and structural scheme were studied, and the key technical solutions such as structural spatial layout and section optimization, structural stiffness improvement, thermal stress and expansion deformation control, internal pressure control, and ash deposition prevention measures were formed. A new type of SCR reactor structure was designed. Results show that, the new type of SCR reactor structure is reasonably arranged, the height of the catalyst layer beam can be reduced by about 50%, and the total steel consumption can be saved by about 20%. At the same time, finite element simulation analysis shows that the structure has good stress performance and safety performance. The new type of SCR reactor has been applied in many projects, effectively controlling the nitrogen oxides (NO_x) emission from power plants and generating significant benefits.

A 1 000 MW ultra-supercritical double reheat unit experienced an abnormal drop in control (EH) oil pressure during a valve activity test (ATT), which led to the closure of all turbine control valves, triggering the generator reverse power protection and causing the unit to trip. The causes of the accident were analysed, and the treatment suggestions and subsequent preventive measures were put forward based on the working principle of the oil motor and the control valve anti-jamming logic in the logic of the digital electrohydraulic control system (DEH). Results show that, by strictly controlling the quality of EH oil, optimizing the test process, and enhancing the inspection of logic configurations, the turbine trip caused by ATT can be effectively avoided. The research results have a certain reference significance for the commissioning and operation of similar types of units.