The operating parameters of coal mills directly affect the safety and combustion performance of coal-fired units. Therefore, it is of great significance to carry out real-time monitoring of CO volume fraction at the outlet of coal mills and accordingly have safety early warning based on the monitored data. In this work, the measurement accuracy and detection limit of wavelength modulation direct absorption spectroscopy(WM-DAS) method were verified based on tunable diode laser absorption spectroscopy(TDLAS) and Herriott multi-pass cell. The experimental results showed that the measured CO volume fraction agree very well with the preset values in the range of 1 to 10 μL/L, and the detection limit can be as low as 5.2×10^–3 μL/L(300 s), which suggests the extremely high measurement sensitivity and accuracy of this method. Subsequently, based on this prototype experiment, an on-line monitoring system for the trace CO volume fraction was developed. Then, combined with the high-fidelity pretreatment technology of fuel gas based on the principle of constant-flow dilution, an on-line monitoring system for trace CO volume fraction was developed and applied to the outlet of coal mill of thermal power unit. The on-line CO monitoring and safety warning at the outlet of 5 coal mills of a single thermal power unit were realized by using multi-point alternating measurement strategy. With the monitored CO volume fraction and temperature of the coal mill outlet, the temperature of the primary air is adjusted to improve the boiler efficiency while ensuring safe operation of coal mill.

During signal sampling process of steam turbine digital electric hydraulic control system (DEH) tests, situations that the instrument can not meet the requirements of Nyquist sampling due to the frequency of the primary components is over high may occur. To solve this problem, the envelope of the signal is calculated through Hilbert transform, and the valve closing time is calculated according to the envelope signal. However, the calculation accuracy is limited due to the time interval of the peak points. To improve the calculation accuracy, the undersampled signal is reconstructed, the primary frequency is analyzed by using fast Fourie transform (FFT), and the primary frequency of the signal is determined based on the nature of the frequency domain. On this basis, the initial phase of the AC signals is calculated using the initial value, and the undersampled signals is reconstructed according to the frequency and initial phase. The closing time is calculated according to the difference between the reconstructed and sampled signals based on Akaike information criterion (AIC). In comparison with the Hilbert transform method, the reconstruction method can improve the calculation accuracy. The reconstruction and analysis method can be used in all kinds of undersampled periodic signals, which can make up the shortcomings of hardware in DEH tests.

In view of the frequent failure of power generation equipment under the background of frequent deep peak regulation, flexible operation, energy saving and consumption reduction of thermal power units, a coal mill fault warning method based on multiple state estimation-analytic hierarchy process is proposed. Firstly, based on the characteristic parameters of coal mill Spearman correlation analysis for dimension reduction, equidistant sampling method is used to extract some samples from a large number of coal mill history data memory matrix, after normalization, memory matrix is formed. Then, multi-state estimation algorithm is adopted to calculate the corresponding memory estimated vector according to the memory matrix and the observation vector. The characteristic parameters are given different weights by using analytic hierarchy process (AHP), and the fusion similarity between the observed vector and the estimated vector is calculated, and the fault warning of coal mill is carried out based on the adaptive threshold method. Finally, the actual fault data of a roller medium speed coal mill is taken as an example to verify the effectiveness of the method. The results show that, this method has less misalarm rate and false alarm rate for coal mill fault warning, which can reduce the actual fault probability of coal mill to a certain extent.

The existing GIS disconnector contact state evaluation method is based on the single state characteristic quantity, the reliability of the evaluation result is low, and it is easy to misjudge and erroneous judgment. So a method of GIS disconnector contact state evaluation based on multi-feature fusion was presented. The multi state quantity comprehensive detection experimental platform of 220 kV GIS disconnector was built. And the relationships between the GIS disconnector shell temperature signal, shell vibration signal, partial discharge signal and the contact state of the disconnector were experimentally studied. On this basis, the temperature rise of GIS disconnector shell, the amplitude of shell vibration signal and the discharge amplitude of partial discharge UHF signal were taken as the state characteristic quantities of disconnector, and the contact state evaluation model of disconnector based on support vector machine was established. The test results show that the accuracy of GIS disconnector contact state evaluation method based on multi-feature fusion is the highest, can reach 92.92%.

In order to avoid disrepair and overrepair, improve the reliability and availability of gas turbine, reduce operation and maintenance cost, and ensure its safe, stable, green and efficient operation, a novel approach is proposed for fault diagnosis of gas turbine in power plants under transient operating condition with variable geometry compressor. The mathematical relationship of the influence of the compressor inlet guide vane position on compressor flow and efficiency characteristics is deduced. A high-precision thermodynamic model for the purpose of performance analysis and gas-path fault diagnosis is established. Moreover, the gas path fault diagnosis strategy of power plant gas turbine, which is suitable for transient and variable conditions and includes variable geometry, is proposed. Through actual operation test, it is verified that the proposed method has high diagnostic accuracy and good real-time performance, and the fault identification under transient and variable conditions is realized.

In order to effectively prevent the slagging of a supercritical 650 MW opposed firing boiler, the influence of different coal types on the flue gas temperature at the furnace outlet and the heat load of the boiler was checked by thermodynamic checking calculation, and the influence of the air distribution in the furnace and the cone-expanding angle of the burner on the flue gas dynamic field and flue temperature of the furnace was analyzed by CFD simulation. The results of the thermodynamic checking calculation showed that the boiler and the coal type were not the main reason for slagging. The variable air volume simulation showed that adjusting the ratio of internal and external secondary air could have effect on the dynamic field of flue gas. But in operation, changing the air volume did not solve the slagging problem well. The simulation results pointed out that the heat load of the water wall area could be reduced by reducing the cone-expanding angle of the burner from 45°to 30°, so as to inhibit the slagging. In the actual adjustment, after changing the cone expansion angle of the burner from 45°to 30°and adjusting the air distribution, the slagging situation of the boiler was greatly improved.The calculation results of variable SOFA wind showed that the appropriate reduction of SOFA wind proportion could reduce the flame height and the flue gas outlet temperature. The simulation of variable secondary air rotation showed that the secondary air rotation had a significant influence on the flow field and the slagging risk would significantly increase if the rotation of the burner was not arranged according to designed value. Further adjustments to SOFA wind ratio and secondary wind swirl could be considered in following adjustments.

Based on the dynamic vibration absorber method, analysis on abnormal vibration of vertical condensate pump motor and vibration reduction measures are carried out. According to the vibration characteristics of the condensate pump motor, the design method of power vibration absorption is studied theoretically, and the power vibration absorber is developed and designed and applied to the actual unit. The results show that, the dynamic balancing method has certain limitations in alleviating the vibration exceedance of the condensate pump motor during varying frequency operation, and cannot reduce the vibration amplitude of the condensate pump motor in both directions at the same time. The mass participating in the vibration of the condensate pump system shows a growing change with the increasing additional mass, and the first-order vibration mass at the top of the condensate pump motor is about 6 000 kg (X direction) and 7 000 kg (Y direction). With mass ratio of 2%, 5% and 10%, the maximum vibration amplitude in X direction is reduced by 80%, 83% and 86%, and the maximum vibration amplitude in Y direction is reduced by 68%, 77% and 83%. The dynamic vibration absorber device effectively reduces the vibration in both directions, and the actual reduction of vibration in X and Y directions is about 53% and 66% during the whole frequency operation period. The vibration control method based on the dynamic vibration absorber of the condensate pump motor has an excellent vibration reduction effect.

Frequency conversion condensate pump is easy to produce structural resonance because of insufficient support stiffness of vertical structure and increased working frequency range. According to the problem of excessive vibration in two resonance zones of a 350 MW vertical variable-frequency condensate pump, this paper introduces the principle and influencing factors of structural resonance, the judgment method of vibration fault and the treatment process. Theoretical calculation and actual treatment results show that, when there is unbalance on the shafting, dynamic balancing can effectively reduce the vibration amplitude in the resonance area of the condensate pump. However, when there are multiple resonance zones at the same time and the counterweight schemes corresponding to different resonance zones are contradictory, the dynamic balance mode cannot be considered at the same time. The angle of the counterweight determines the dynamic balance effect. Due to the limitation of the reserved counterweight angle, the rapid change of the vibration phase near the resonance point, inaccurate measurement and other factors, it is difficult to achieve on-site fine dynamic balance. Increasing the support to improve the system stiffness can change the natural frequency of the structure and reduce the vibration amplitude in the resonance area, which is an effective measure to solve the resonance problem. The vibration reduction effect of radial support is better than that of axial support.

The effects of different heat transfer fluid (HTF) parameters on charging and mechanical performance of the thermal energy storage (TES) tank using phase change material (PCM) capsules are studied by employing the fluid-solid coupling calculation. The results show that, with the inlet HTF flow velocity increased from 0.000 7 m/s to 0.000 9 m/s, the total heat storage quantity is basically unchanged, the average charging power increases from 5.33 MW to 6.79 MW, and the peak maximum mechanical stress (MMS) of the tank wall decreases. When the initial cold HTF temperature decreases from 610 K to 530 K, the total heat storage quantity increases, the average charging power increases from 5.29 MW to 6.81 MW, but the peak MMS of the tank wall also increases. With the initial hot HTF temperature increases from 730 K to 810 K, the total heat storage quantity increases obviously, the average charging power increases from 3.81 MW to 7.97 MW, but the peak MMS also increases to 159.6 MPa. Hence, to improve the charging performance of the TES tank, on the premise of ensuring the structural safety of steel wall of the TES tank, the inlet HTF flow velocity and initial hot HTF temperature should be increased properly, and the initial cold HTF temperature should be reduced properly.

Turbine cooling system is one of the cores of modern heavy-duty gas turbines. How to consider the influence of cold gas admixture is one of the first problems to be solved in gas turbine thermodynamic modeling and analysis of the influence of key parameters. With the continuous deepening of overall design of the gas turbine, a more detailed thermal performance calculation model is required to coordinate and match key components and the whole and ensure the final realization of the design performance. A calculation method of step-by-step blending and overall thermal performance of gas turbine based on one-dimensional aerodynamic analysis of turbine is proposed, and a thermal performance model of heavy-duty gas turbine is established. Moreover, the influence and key parameters and thermodynamic performance scheme of G/H class gas turbine is investigated. The analysis shows that, the turbine initial temperature, pressure ratio and cooling air volume are the key parameters affecting the overall thermal performance of the gas turbine, and the three should be coordinated in the overall design. While improving the turbine initial temperature, the minimum cooling air amount required to reach the temperature level should be studied, the optimal pressure ratio should be analyzed, and the iterative calculation and thorough research should be confirmed after combining the component design. The research results can provide a reference for the overall performance design of autonomous heavy-duty gas turbines.