The deep peak shaving and flexible operation of thermal power units increase the risk of crack faults in the rotors of main and auxiliary equipment, posing a serious threat to the safe and stable operation of the units. According to the established vibration equation of the cracked rotor, the main vibration characteristics of the cracked rotor are summarized. On this basis, combined with the field diagnosis experience, a practical method of identifying the cracked rotor through vibration analysis is proposed, with criteria including continuously climbing fundamental-frequency vibration and ineffective rotor dynamic balance, continuous increase of second harmonic vibration, abnormal Bode curve, and so on. Finally, three cases of rotor crack fault identification in the operation of a steam turbine, a generator and a boiler primary air fan are given to illustrate the practical application process and accuracy of this method.

In view of the problems that conventional fly ash carbon content prediction models are prone to fall into local optimal solution traps and have insufficient generalization ability, based on the boiler hot-state multi-condition tests, 28 key characteristic parameters are selected through data collection, processing, Pearson correlation analysis of variables, and importance ranking, the sparrow search algorithm (SSA) is used to determine the optimal hyper-parameters of the random forest (RF) model, and an SSA-RF prediction model is constructed. The model verification results show that the root-mean-square error of the SSA-RF model in the training set and the test set decreases to 0.010 8 and 0.019 1 respectively, and the coefficient of determination R² increases to 0.999 7 and 0.998 1 respectively, demonstrating the excellent prediction accuracy and generalization ability of the model. Furthermore, the ISSA-RF-SSA algorithm is proposed. The SSA is improved by integrating multiple strategies to achieve global extreme value optimization of combustion parameters. Engineering verification shows that after optimization, the carbon content in fly ash decreased from 2.500% to 1.345%, and the prediction error was only 0.003 percentage points, verifying the accuracy of the model. The research results indicate that the ISSA-RF-SSA method improved by multiple strategies significantly enhances the optimization performance of the algorithm, providing a new idea for the combustion optimization of coal-fired units.

Phosphate ester fire-resistant fluids, serving as hydraulic working medium for the speed regulation system of steam turbines, play a crucial role in the normal operation of steam turbines. Currently, imported products dominate the phosphate ester fire-resistant fluids market for the speed regulation system of steam turbines in domestic power generation units. To break the power industry’s high dependence on imported fire-resistant fluids, it is imperative to develop domestic phosphate ester fire-resistant fluids through independent research and application. Through performance evaluation of various domestic tri-aryl phosphate esters, tri-(dimethylphenyl) phosphate was identified as the optimal choice for domestic fire-resistant fluid development. Via oxidation and adsorption refining processes, the stability of the domestic tri-(dimethylphenyl) phosphate was significantly enhanced, resulting in the successful development of high-performance phosphate ester fire-resistant base oil. After the research on various additives, an optimized additive formulation was established, ultimately producing high-performance phosphate ester fire-resistant fluid that meets the new fluid requirements specified in Guide for Operation and Maintenance of Phosphate Ester Fire-resistant Fluid Used in Power Plant (DL/T 571—2014). Static and dynamic simulated aging tests demonstrated that the domestic phosphate ester fire-resistant fluid exhibits superior anti-aging performance compared to the commercially available alternatives. Following one year of industrial demonstration in power generation units, the fluid maintained new-oil quality standards throughout the application period, with the turbine governing system operating normally.

The optimization design of the first domestically produced full-capacity feedwater pump used for No.9 unit of the Huaneng North Power Dalat Power Plant Phase V expansion project (1×1 000 MW) is introduced. The three-dimensional structural model of the feedwater pump is established by using ANSYS Workbench software, and the thermal stress analysis of the pump body and finite-element calculation of the impeller strength are conducted. Moreover, the trial operation of the turbine-driven feedwater pump unit and optimization suggestions are provided. The feedwater pump runs under various load conditions of the unit, ensuring that the feedwater flow and pump outlet pressure meet the operational requirements, with the temperature and vibration indicators of each bearing in the steam pump unit falling within the excellent range. Based on the performance assessment test data of the feedwater pump, the calculated efficiency is 84.32%, which exceeds the guaranteed efficiency value. The successful application of this domestically produced full-capacity steam feedwater pump unit in a 1 000 MW coal-fired unit can provide experience for planned or newly constructed units and has certain reference value.

Based on the concept of high efficiency of gas turbine variable back pressure operation regulation, a high back pressure gas turbine combined cycle power generation system scheme is proposed, in which a pre-compressor and an expander are set in front and behind the main top cycle respectively to maintain and regulate the gas turbine exhaust pressure. Key parameters of the combined cycle are designed based on the initial parameters of the F-class gas turbine, and the case and characteristic analysis are carried out for the temperature of recirculated gas (divided into two conditions: cooling to normal temperature and not cooling), the main top cycle pressure ratio and the gas turbine back pressure. The results show that, the combined cycle efficiency of the recirculated flue gas cooling is not as high as that of the non-cooled flue gas cooling, which is 58.07% and 58.94% when the turbine back pressure is 0.30 MPa. The exergy loss rate of the main compressor is lower because the exit temperature of the main compressor is higher when the recirculated flue gas temperature is higher. When the gas turbine back pressure is 0.30 MPa, the maximum pressure ratio of the combined cycle system efficiency is 17.0, the corresponding combined cycle efficiency is 58.97%, and the specific work is 563.87 kJ/kg. Considering the specific work comprehensively, the recommended main top pressure ratio is 15.4, and when the turbine back pressure is from 0.03 MPa to 0.35 MPa, the variation range of the combined circulation efficiency under the two conditions is about 56.00%~58.57% and 55.81%~59.12%, respectively, which increases at first and then decreases, and the variation range of the combined efficiency is not large at high back pressure. At the same time, based on the practical engineering application, the design of a single waste heat boiler is considered, and its thermal characteristics and possible flexible, low-cost and efficient utilization of renewable energy are analyzed, which provides a new system scheme reference for the flexible and efficient modern combined cycle with multi-energy complementarities.

The fuel adaptability of a certain type of gas turbine combustion chamber is systematically investigated in response to the characteristics of blast furnace gas composition and its significant fluctuations in its calorific value. By coupling the detailed chemical reaction mechanism with numerical simulation methods, the comprehensive performance characteristics of the gas turbine combustion chamber under different calorific values and composition conditions were obtained, with a focus on analyzing the distribution of temperature and concentration fields and their influencing mechanisms. The results show that, under the same initial conditions and fuel calorific value, as the volume fraction ratio of H₂ to CO in the gas increases, the average temperature at the combustion chamber outlet decreases from 1 769.35 K to 1 710.11 K, the temperature distribution coefficient decreases from 0.044 to 0.016, the NO_x emission concentration at the outlet decreases from 7.56×10^–6 mol/m³ to 1.49×10^–6 mol/m³, and the CO emission concentration decreases from 993.98×10^–6 mol/m³ to 421.95×10^–6 mol/m³, and the combustion efficiency increases from 98.48% to 99.14%. As the volume fraction ratio of CO₂ to N₂ in the gas increases, the average temperature at the combustion chamber outlet decreases from 1 739.30 K to 1 694.99 K, the temperature distribution coefficient fluctuates in the range of 0.032~0.045, the NO_x emission concentration at the outlet decreases from 3.18×10^–6 mol/m³ to 1.39×10^–6 mol/m³, the CO emission concentration increases from 633.73×10^–6 mol/m³ to 832.45×10^–6 mol/m³, and the combustion efficiency decreases from 98.89% to 98.56%. In addition, as the fuel calorific value increases, the average temperature at the combustion chamber outlet significantly increases from 1 587.30 K to 1 862.39 K, the temperature distribution coefficient shows a downward trend, the NO_x emission concentration increases from 0.29×10^–6 mol/m³ to 18.66×10^–6 mol/m³, the CO emission concentration increases from 459.25×10^–6 mol/m³ to 1 030.61×10^–6 mol/m³, and the combustion efficiency decreases from 99.14% to 98.33%. Finally, 20 sets of data are selected for nonlinear surface fitting. For the blast furnace gas with a heat value range of 3~5 MJ/m³, all the the R² values of the fitting formula are greater than 0.90, indicating this formula can provide a theoretical basis for the control of low-heat-value fuels in gas turbine combustion chambers.

The RNG k-ɛ model was used to numerically simulate the flow and heat transfer characteristics of supercritical CH₄-H₂ mixtures in horizontal pipe. The thermal physical properties of the CH₄-H₂ mixtures with hydrogen ratio of 0~30%, as well as the heat transfer process of the CH₄-H₂ mixtures with hydrogen ratio of 0~15% in the horizontal tube were analyzed. The influences of mass flow rate (150~250 kg/(m²·s)) and heat flux density (150~250 kW/m²) on flow and heat transfer of the mixed working fluid with hydrogen ratio of 10% were studied. The results show that when the hydrogen ratio increases from 0 to 30%, the pseudo-critical temperature of the mixed working fluid increases slightly from 190.4 K and then sharply decreases to 181.7 K, and the pseudo-critical pressure increases from 4.3 MPa to 12.3 MPa. With the increase of the hydrogen ratio (0~15%), the heat transfer between the fluid and the wall is strengthened. The increase of mass flow rate strengthens the heat transfer capacity of the mixed working fluid and weakens the heat transfer deterioration caused by buoyancy effect. The increase of heat flux strengthens the heat transfer degree of the wall under the mixed working medium, and weakens the heat transfer degree of the upper wall due to the advanced appearance of the gas-like film. Increasing the mass flow rate and heat flux density can enhance the heat transfer to varying degrees. The research can provide theoretical reference for mixed working medium heat exchangers in hydrogen-doped natural gas transmission and power circulation systems.

Scramjet engines are mainstream power systems for hypersonic vehicles, and it has significant thermal protection demand and power supply demand during the long-time and high-Mach-number flight of hypersonic vehicle. An integrated cooling and power generation system based on supercritical CO₂ Brayton cycle is designed for a certain type of scramjet engine. The characterization model of wall heat source for this scramjet engine is constructed. The influences of key design parameters, such as heat absorption pressure, turbine inlet temperature, heat release pressure, and regeneration degree, on the system thermodynamic performance are investigated, as well as the coupling relationships among various design parameters. The optimal design schemes and performance of the integrated cooling and power generation system are obtained by the multi-parameter collaborative optimization. The thermodynamic advantages of the proposed system are also evaluated by comparing with the conventional system with a simple cycle as the baseline. The results show that the proposed integrated cooling and power generation system can achieve a maximum power generation efficiency of 15.9% and a continuous power supply of 206.2 kW, which exhibits a good potential for actual application. The smaller the pinch temperature difference during the heat absorption process of the engine wall, the more significant the thermal performance advantage of the proposed system compared to the benchmark scheme, and the maximum relative increase in power generation efficiency can reach 9.3%.

The Brayton cycle is widely recognized as a key power cycle in the third-generation solar thermal power generation technology. Leveraging the strengths of artificial neural network methods for importance evaluation and quantitative analysis, this research employs a control variable approach to identify critical parameters, including turbine inlet temperature and compression ratio, from a range of operating parameters. In this method, the significance of parameters increases as the R² value decreases. Notably, when excluding these key parameters, the R² values fall to 0.57 and 0.64, respectively, both are lower than other operating parameters. Furthermore, the quantitative analysis of output power in the Brayton cycle yields exceptional results, achieving an R² value exceeding 0.999. The R² values for thermal efficiency and input heat are 0.992 and 0.988, respectively. Finally, the multi-objective optimization results suggest optimal settings of 500 ℃ for turbine inlet temperature and 2.19 for the compression ratio, corresponding to a thermal efficiency of 46.58%, output power of 100.97 kJ/kg, and input heat of –176.5 kJ/kg. This study offers valuable insights for the operational efficiency and performance assessment of the Brayton cycle in solar thermal power plants.

Based on the design and operational conditions of Guangdong Huaying LNG Terminal and its surrounding industrial environment, a cascade utilization scheme integrating thermodynamic power generation with shallow cold storage was developed. Moreover, key process parameters were modeled and solved using HYSYS software to enhance energy efficiency and maximize cold energy utilization. The results show that, under the condition of minimum daily send-out (228 t/h), the original single-stage thermodynamic cycle coupled with cold storage achieved an annual power generation exceeding 32.83 GW·h while meeting the cooling demand of a 7 500 m³ cold storage facility. The optimized scheme adopts a two-stage thermodynamic cycle with shallow cold storage, via employing a 40% (weight percentage) ethane and 60% (weight percentage) propane mixed working fluid, and elevating heat source temperature, this improved design increased the annual power generation to 62.04 GW·h, and raised the net power output per unit mass of LNG from 17.54(kW·h)/t to 33.02 (kW·h)/t, with estimated annual electricity cost savings of approximately 53.641 million yuan. Although multi-stage heat engine cycles can reduce irreversible losses caused by temperature differences, considering factors such as cost-benefit ratio and operational reliability, the second scheme demonstrates strong engineering feasibility and economic viability by closely aligning with the actual conditions of the Huaying LNG Receiving Terminal. Both cascade utilization designs demonstrate distinct advantages for different development stages of the receiving terminal and different evaluation indicators for LNG cold energy utilization, providing valuable references for post-commissioning cold energy applications.