In order to study the corrosion behaviors of candidate materials for superheater of supercritical boilers in high-temperature flue gas environment, three austenitic heat-resistant steels including S31042, S31035 and C-HRA-5 were exposed to laboratorial simulated coal-fired flue gas for hot corrosion tests. The tests were carried out at 650, 675, 700 and 725 ℃. On the sample surface, there were three conditions including no coating, coating with real coal ash, and coating with corrosive simulated coal ash. The test duration was 500 h. The corrosion kinetic curves of the three materials were obtained through experimental research, and corrosion behaviors of the material were analyzed by XRD, SEM and EDS. Moreover, corrosion resistance of the three materials was compared. The results indicated that, the three materials had excellent resistance to oxidation and corrosion under the conditions of no coating and coating with real coal ash. Under the condition of coating with corrosive simulated coal ash, the material corrosion intensifies and the corrosion products are layered. The temperature effect was different under different coating conditions. S31042 had the best corrosion resistance, and the corrosion resistance of S31035 and C-HRA-5 materials was comparable.

Large-scale grid connection of new energy power generation makes cogeneration units need flexible operation to smooth out the fluctuation brought by new energy access. In order to meet the control requirements of flexible operation of the unit and the safety of the unit operation, a flexible control strategy for cogeneration units based on flexibility evaluation is designed. Firstly, according to the response characteristics of electrical load, thermal load and throttle pressure of the unit, a calculation method of flexibility evaluation indexes which can represent the load adaptability and operation safety of the unit are proposed, and these indexes are used as the basis for selecting the optimal flexibility factors. Then, the influence of flexibility factor on the system performance under a single working condition is simulated. Finally, on the basis of determining the optimal flexibility factors under different working conditions, the adaptive flexibility factors that changing with working conditions are designed and applied to the flexible control. The simulation results show that, the control strategy can not only achieve a better control effect when the unit runs under large-scale conditions change, but also achieve a better control for the unit after the low-pressure cylinder is cut off, which can meet the control requirements of flexible operation of the unit and ensure the safety of the unit operation..

Voltage transformer (TV) interturn short circuit at generator outlet will cause unbalanced voltage in system, resulting in zero sequence stator ground fault protection of generator fundamental. The external characteristics of TV fault are of great significance to stable operation of the unit. In order to understand the external characteristics of TV fault, based on Maxwell and Simplorer software, a field circuit direct coupling finite element model for the electromagnetic conversion process of single-phase voltage transformer is established, which can realize data exchange between field circuits at each calculation step. In view of the large number of turns of TV primary winding, which is difficult to model directly, winding grouping technology is proposed. An experimental platform is designed and built to verify the accuracy of the simulation model. Based on the calculation results of finite element eigenvalues, the electrical and magnetic eigenvalues of TV in different operating states are analyzed, and the analytical model of TV inter turn fault based on winding grouping technology is further given. The simulation results show that, the TV turn-to-turn fault model is accurate and effective in analyzing the primary current, circulating current and other fault characteristic quantities.

As a nondestructive testing method, magnetic particle testing is widely used in power industry. The comprehensive sensitivity of the magnetic particle detection can be tested by A1 standard shims. However, at present, the evaluation of the clarity of magnetic trace on standard shims still depends on subjective judgment of the tester. In order to eliminate the subjective factors in the evaluation, this paper proposes a standard magnetic trace evaluation method based on machine vision. Based on Python programming language and OpenCV function library, the initial obtained magnetic trace is processed by image correction, magnetic trace extraction, quantitative analysis and evaluation using computer program. On this basis, the influence of the thickness of non-magnetic layer on the comprehensive sensitivity of magnetic particle detection is investigated using this method. It is shown that the magnetic trace evaluation method based on machine vision is more objective and accurate than the conventional manual evaluation.

As a clean and efficient power generation technology, solar thermal complementary combined cycle power generation (ISCC) system is concerned widely. By taking the ISCC system containing three-pressure reheat combined cycle and trough solar field as the research object, and based on the conventional trough ISCC system (using solar energy to replace the high pressure evaporator (system 1)), two new trough ISCC system are presented, namely using solar heat collection field to replace the high and medium pressure evaporators simultaneously (system 2), and using solar heat collection field to replace the high, immediate and low pressure evaporators simultaneously (system 3). Moreover, the dynamic performances of the above three ISCC systems are analyzed under the operation condition of typical day. The results show that, with proper operation strategy presented above, the three systems can not only realize safe and stable operation, but also reduce the impact of solar energy varies on the ISCC system output power. Under the operation condition of typical day, the second type of ISCC system (system 2) has better thermal performance.

Blade fractures and cracks occurred on low pressure second last stage moving blade of a steam turbine before and after the blade optimization. In order to find out the cause of this type blade failures and prevent subsequent reoccurrence, the blade failure, operating parameters and historical records were checked, and the materials and fractures of some failed blades were analyzed through physical and chemical inspection. Moreover, the centrifugal stress of the blade and the vibration characteristics of the gear train before and after optimization were numerically analyzed by finite element method. The results show that, the blade fracture is a high peripheral fatigue fracture. Before optimization, the main reason for cracks and fractures at the connection transition between the top of the inner cambered surface and the shroud on the steam outlet side of the blade is that the blade has a large torsional recovery under working conditions, resulting in severe compression of the shroud, and stress concentration and fatigue damage occur at the connection transition between the top of the inner cambered surface and the shroud on the steam outlet side. The unreasonable design of blade root structure is the main factor for high cycle fatigue cracking of blade root, while the vibration of the sixth pitch diameter of the first stage of blade impeller system falling into the "3-coincide point" resonance area is the secondary factor for blade failure. After optimization, the main reason for the fracture is the unreasonable design of the blade root structure, and the vibration of the eleventh pitch diameter of the second stage of the blade impeller system falling into the "3-point" resonance area is the secondary factor causing the blade root failure.

To solve the problem of low recognition accuracy of transformer insulation oil gas fault diagnosis, the slime mold algorithm (SMA) is improved by the reverse learning strategy to form the improved slime mold algorithm (ISMA), thus to improve the global optimization ability and optimize the support vector machine (SVM). An ISMA-SVM optimized fault diagnosis model is established, and the sample set is used for learning and training. The diagnosis and recoginition results are compared with that of the greywolf algorithm (GWO-SVM) and the particle swarm optimization (PSO-SVM), it shows that the accuracy of the ISMA-SVM fault diagnosis and recognition is 93.3%, which is 6.66 and 10.66 percentage points higher than that of the GWO-SVM and PSO-SVM, respectively.

Welding of dissimilar steels is a widely used connection method for super-heater tubes of boilers in power plants. Taking the TP304H/T22 dissimilar steel welded joint with backing plate at the superheater outlet of a thermal power unit as the research object, the formation mechanism and influence of cracks in the welded joint are analyzed through macro measurement, microstructure analysis, EDS energy spectrum detection and tensile test. The results show that, the differences in thermal expansion coefficients of the three substrates and stress concentration are the cause of the cracks of the dissimilar steel weld with backing plate and crack propagation in nickel base weld filler. The weld is the weak link in room temperature tension, while the fusion line and base metal are the fracture parts in high temperature tension.

In order to realize zero liquid discharge, a power plant treated circulating wastewater by the combination process of two stage softening and clarification, media filtration, ultrafiltration, nanofiltration (NF) and reverse osmosis (RO), and treated terminal wastewater by the combination process of chemical softening, tubular microfiltration (MF), NF, seawater desalination reverse osmosis, electrodialysis (ED) and evaporative crystallization. After the above measures were taken for 1 year, insufficient NF output was found in the circulating wastewater treatment system, and serious MF membrane organic fouling and ED silicon scaling was observed in the terminal wastewater treatment system. Thus, the causes of the membrane fouling was analyzed and the desulfurization process water was optimized to reduce the chemical oxygen demand (COD) of desulfurization wastewater from the source. Moreover, the MF operation mode was optimized, so as to slow down the MF organic pollution phenomenon. In addition, the RO concentrated water of circulating water treatment mode was adjusted, and the total silicon mass concentration was reduced to less than 1 mg/L before being fed into the ED equipment, to solve the problem of the ED silicon scaling.