Supercritical water coal gasification for hydrogen production is a clean and efficient power generation technology. Based on entropy generation theory, numerical investigation on the non-equilibrium condensation flow of an H₂O/CO₂ mixed working fluid in the final-stage cascade is conducted. The losses are quantified by identifying regions within the cascade where different types of losses occur and calculating the entropy generation in each region. The mechanisms behind the impact of back pressure and CO₂ mass fraction in the mixed fluid changes on various losses and entropy generation sources are analyzed. The effects of these parameters on the loss distribution are explored, including a detailed description of how shock waves influence wake losses and the entropy generation distribution within the boundary layer. The results show that wall losses, wake losses, and boundary layer losses consistently account for over 90% of the total losses under different operating conditions. The main sources of entropy generation are wall dissipation, direct dissipation, and turbulence dissipation. When the back pressure increases by 5.03 kPa, the total loss decreases by 31.73%. However, when the CO₂ mass fraction in the mixed fluid increases by 40%, the total loss increases by 4.71%. The variation in turbulent dissipation entropy generation within the wake loss is the primary cause of the total loss change and is closely linked to the velocity gradients in the flow field. This study offers significant insights for the loss analysis of the wet steam region in mixed medium steam turbines and for aerodynamic optimization.

Carnot battery (CB) is an energy storage technology with the advantages of high energy storage density and low investment cost. The single-stage heat pump of basic Carnot battery have a low coefficient of performance (COP) under high energy storage density conditions, resulting in a phenomenon of high quality but low utilization of heat. In order to solve this problem, a CB using cascaded heat pump (CHP) and supercritical organic Rankine cycle (ORC) is proposed. Through modeling and analysis, the optimal combination of CHP-CB working fluids is obtained, and the effects of waste heat source temperature, high and low temperature heat storage tank temperature, CHP intermediate temperature on system COP, energy conversion efficiency, energy storage density (E_D) and system exergy loss are discussed. The results show that under high energy density conditions, the COP of the CHP-CB is about 23.5% and 26.9% higher than that of the basic CB when the temperature of the low-temperature storage tank is 50 ℃ and 32 ℃, respeetively. When the temperature of the low-temperature storage tank is 30 ℃, the energy conversion efficiency of the CHP-CB can reach 63.11%. The E_D can reach 13.9 kW·h/m³ when the temperature difference between the high- and low-temperature storage tank is 93 ℃, and cascade heating for the heat storage working fluid can be realized.

Improving the flexibility of coal-fired power generation units is of great significance for ensuring the reliable and stable operation of the power grid. The heat and mass transfer process in the CFB boiler furnace is investigated deeply. It is found that when the load changes, the air volume entering the furnace responds rapidly, driving the change of the particle suspension density in the dilute phase zone, thus triggers the rapid change of the convective heat transfer coefficient and the total heat flux. Different from pulverized coal-fired boilers, the average furnace temperature of the CFB boiler changes little with load. During the load change process, although the heat storage capacity is large, the thermal inertia is not fully manifested, and it does not have a negative impact on the load change rate. Therefore, the load adjustment process of the CFB boiler is based on the rapid response of the heat transfer coefficient under near constant temperature conditions, which is essentially different from the load-changing mechanism of the pulverized coal-fired boiler. In addition, a considerable amount of unburned carbon in the bed material can serve as a potential fuel supply source when the load increases. When the oxygen supply is increased, the combustion rate can be rapidly improved. Combined with the heat storage of bed materials and castable, the CFB boiler can be regarded as having a built-in “energy storage” function, providing long-term energy support for load adjustment. Measures such as reducing the average bed material size, decreasing the feeding coal size, and adding powdered-coal and circulating ash can further increase the load-changing rate of the CFB boiler. The test results on a 300 MW subcritical CFB boiler unit show that the load increasing and decreasing rate can reach 4%~9%Pe/min, approaching the load-changing capability of a gas turbine unit. The research demonstrates that the CFB boiler has the potential for rapid load change in principle and will play a more crucial role in the new power system dominated by renewable energy sources.

In order to solve the technical problem that the cooling margin of the cylindrical hole is insufficient at low blowing ratios and the cold flow is separated from the wall at high blowing ratios, based on the tip-covered vortex generator (TCVG), a new type of vortex generator (VG) is proposed, which is called tile-shaped vortex generator (TVG). The conventional cylindrical hole and the cylindrical hole with TVG are numerically simulated. The results show that the film cooling efficiency of the cylindrical hole with TVG is 200% higher than that of the conventional cylindrical hole. Moreover, it solves the problem that the cold flow of the conventional cylindrical film hole will separate from the wall at high blowing ratios. With the increase of TVG width, the film cooling efficiency increases, and tends to be stable when the width reaches twice the film hole diameter. With the increase of TVG height, the suppression effect of TVG on cold flow is weakened, and there is an uncooled gap in the near-field area at high blowing ratios, and the film cooling efficiency shows a downward trend. The expansion angle of TVG has little effect on the film cooling effect, and the optimal expansion angle is 7.5°.

The first stage blades of a heavy-duty gas turbine compressor are newly independently developed and designed, which use the advanced 3D modeling technology to design high-performance blade profiles. It is necessary to master the blades’ vibration characteristics to verify the reliability of the blades. The finite element method was used to analyze the vibration frequency of the blades under dynamic frequency testing conditions and actual operating conditions. Meanwhile, the radio telemetry technology has been introduced to verify the dynamic frequency of the blade. The dispersion effects caused by blade material and processing tolerances, as well as assembly tolerances were also considered. The results indicate that the theoretical analysis of blade vibration is consistent with the test characteristics, with a deviation of no more than 1.2%. The theoretical frequency avoidance margin of compressor blades under operating conditions can meet the deviation between numerical analysis methods and experimental testing methods, as well as the frequency influence caused by material, processing, and assembly factors, and still have a large safety margin. The research results provide guidance for the development of gas turbine compressor blades, as well as the upgrading, improvement, and vibration monitoring of blades throughout their entire lifecycle.

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.