Self-recirculation casing treatment can significantly improve the aerodynamic performance of the supercritical carbon dioxide centrifugal impeller in small flow rate region, but the improvement is not obvious near the large flow rate region. Therefore, the coupling effect between the self-recirculation casing treatment and the key parameter of the impeller is considered, and the coupling optimization of the casing treatment geometry and the impeller blade sweep angle is carried out to achieve a comprehensive improvement of the impeller performance. After the coupling optimization, the efficiency of the impeller is increased by 3.51%, 2.60% and 4.43% respectively under the large flow rate condition, the design condition and the small flow rate condition. The mechanisms of the coupling optimization for stability and efficiency enhancements are as follows. Under the large flow rate condition, the flow incidence angle of impeller is improved, the subcritical zone inside the impeller is reduced, then the condensation is suppressed and the flow capacity of the impeller is improved. Under the design condition, the recirculation flow of casing treatment is increased, more low-energy fluid near the shroud tip is removed, and the flow field structure downstream of the impeller is improved. Under the small flow rate condition, the internal blockage of the impeller is effectively reduced, the flow stability of the impeller is enhanced, and the mixing loss caused by the recirculation flow is improved, so the impeller efficiency is improved.

Combustion monitoring in large industrial furnace can be simplified to a radiation heat transfer problem within the enclosed cavity system, and precise quantification of its boundary radiation characteristic is the basis to carry out follow-up studyon the radiation inverse problem, but the coupled problem of wall radiation and media radiation need to be solved. A Monte Carlo priciple was involved to solve the radiation heat transfer equation in the enclosed cavity, and to decouple the shares of wall radiation and media radiation in the boundary detection information. The influence of temperature distribution and radiation properties on the share of wall radiation were discussed, at last the experiment verifies the feasibility of using the radiation information of boundary detection to retrieve the wall source term. This study will provide a reference to the exploration of physical field detection method of wall surface in industrial furnace.

The function of query and statistics of data is always the basis of production management and decision-making businesses. According to the results of information construction and applications for many years, the mode, function and performance of data query and statistics still do not satisfy the actual needs. A component for data query and statistics based on supervisory graph software is proposed and developed. Through the design of data path architecture, the optimization of query and statistics mechanism, the developed component has achieved personalized management, lightweight analysis and flexible query of real-time data. The query and statistic component and data link mode developed in this study have been tested and applied in practice. The results show that the function of data query and statistics achieves loose coupling with database. The component can support both the operation modes of C/S and B/S, and provide unified query and statistics of data through supervisory graph from multi-data sources and multi-level organizations. The efficiency of data query and trend query reaches or approaches the level of database native management tools, and is better than that of conventional supervisory information system (SIS) websites. The integration mechanism of data components based on graph with SIS data query and report system is proposed, which helps to reduce the repetitive cost of data use.

The exhausted heat losses in the PRC and inefficiency in medium and low heat source applications are significant challenges affecting the application of supercritical carbon dioxide Brayton cycle for renewable energy sources. To achieve efficient utilization, a precooler-free power/cooling combined system with superior heat source adaptability is proposed and analyzed. Integrating with the precooling-heating coupled module and the absorption power/cooling module instead of the PRC, the waste heat from the LTR is completely recovered, moreover, multiple operating modes ensure that the system performance unaffected by ambient temperature and seasonal changes. Parametric studies indicate that the TUR2 inlet temperature, the WHE1 outflow overheat degree, and the hot end temperature difference have significant effects on the Split Ratio, energy outputs, and the coupling relations among modules. Moreover, due to the improvement of irreversibility and the decrease of exergy losses, the three-largest exergy destructions occur in the IHE, the TUR1, and the RET+GEN, which account for 56.1%, 6.9%, and 5.2% respectively. Furthermore, the optimized cases exhibit optimal η_thermal, η_exergy, c_P,total, and W_net of 84.2%, 74.1%, 9.48 dollars/GJ, and 397.4 MW respectively.

Supercritical carbon dioxide cycle has many advantages such as small turbine size, small compressor power consumption and high cycle efficiency. In order to explore the cycle configuration with the highest power generation efficiency after the power generation system of supercritical carbon dioxide cycle coupled gas turbine, four cycle layouts were proposed. The main parameters of the circulating system were optimized by genetic algorithm with the maximum circulating efficiency as the optimization objective. Among the four schemes, the gas turbine/two-turbine supercritical carbon dioxide combined cycle system has the highest cycle efficiency, which is 44.87%. And the dynamic system analysis of the scheme, with the bottom cycle input heat load as the disturbance variable, explore the dynamic response of the system after the step reduction from full load to 90% load, 80% load and 70% load respectively. The results show that the response time of parameters near the flue gas heat exchanger is faster and the response time is longer when the shadow of thermal inertia is farther away from the flue gas heat exchanger in the working medium flow. At the same position, the response time of pressure is slightly longer than that of temperature, and the drop range of parameters near the high-temperature turbine is greater than that of the low-temperature turbine.

Driven by the “carbon peaking and carbon neutrality” goal, hydrogen blending and pure hydrogen combustion technology of gas turbines have received widespread attention. Producing “green hydrogen” from renewable energy and applying it for power generation is the development direction of the energy field in the future. However, the fluctuation of hydrogen source will inevitably cause the change of hydrogen blending ratio of hydrogen blended gas turbine fuel. Therefore, the dynamic response characteristics of the gas turbine are studied when the hydrogen blending ratio fluctuates. Taking an F-class heavy-duty gas turbine as the research object, a dynamic model is built by using the modular modeling method to analyze the response characteristics of key parameters of the unit and the safe operation of components when the hydrogen blending ratio fluctuates under different loads. The results show that when the hydrogen blending ratio fluctuates, the turbine inlet temperature (T₃) will fluctuate violently, and T₃ overtemperature will occur in the high load region, which will lead to the deterioration of the blade working environment and affect the safe operation of the unit. The larger the fluctuation of hydrogen blending ratio and the higher the power output, the more obvious T₃ overtemperature phenomenon. However, the fluctuation of hydrogen blending ratio has a relatively small impact on the compressor, and the compressor can still maintain a reasonable surge margin.

For enhancing the film stiffness of supercritical CO₂ (S-CO₂) hydrodynamic dry gas seal and reducing the additional power consumption due to the installation of heater in the seal inlet line, a new structure of S-CO₂ hydrostatic-dynamic dry gas seal with the heating of the ring body at the back of the static ring is proposed. Based on the conjugate heat transfer model, the pressure and temperature distribution of dry gas seal were simulated utilizing commercial software Fluent. The steady-state performance and flow field distribution of S-CO₂ hydrodynamic seal, hydrostatic seal and hydrostatic-dynamic seal were compared and analyzed, and the flow and heat transfer characteristics and power consumption of S-CO₂ hydrostatic-dynamic dry gas seals under different heating modes and heat temperatures were discussed. The results show that the film stiffness of the hydrostatic-dynamic dry gas seal is improved more than doubled compared with the hydrodynamic dry gas seal, while the leakage rate increased significantly by 35% at the same time. The power consumption under ring heating mode is 44% lower than that under direct gas heating mode, leading to better operating economy. It provides a new idea for the structure design and auxiliary system improvement of compressor dry gas seal in S-CO₂ power generation system.

The traditional waste heat valve control technology is mainly divided into two methods, mechanism modeling and data-driven. However, in practical applications, the former is difficult to accurately describe due to the complex mechanism. The latter requires high data quality and full working condition samples, which is difficult to meet in a short time. Aiming at the above problems, a fusion-driven optimization method for waste heat valve control is proposed. Firstly, the mechanism knowledge and data knowledge are fused to construct a knowledge graph model based on fuzzy sets, and the valve opening knowledge is materialized. Secondly, the LSTM valve opening optimization model based on time protection mechanism is established, and the time protection mechanism algorithm is proposed to determine the optimal adjustment frequency of the valve. Finally, the recommended valve opening is obtained by knowledge reasoning. Through experimental analysis and verification, this method integrates qualitative knowledge such as waste heat recovery mechanism and quantitative knowledge such as equipment operation data. While improving the safety of equipment, the probability of generating high-temperature saturated steam enthalpy is increased by 94%, and the average daily increase is 8 640 kJ, which realizes the intelligent decision of waste heat recovery valve opening.

The Shockley-Queisser (SQ) limit sets an upper limit on the efficiency of conventional semiconductor photovoltaic devices. A thermophotovoltaic system (consisting of a heat source, a spectrally selective emitter and low bandgap photovoltaic cell) can work as an alternative to break this theoretical efficiency limit. To further improve the power generation efficiency of thermophotovoltaic (TPV) systems, an emitter with a multilayer cross structure based on metamaterials was designed in this work. Through optimization of its geometric size, the emitter demonstrates an excellent narrow-band emission spectrum. This effectively reduces the loss of low-energy photons below the bandgap of PV cells and avoids the absorption of high-energy photons that exacerbate lattice vibrations to cause thermal losses. Its application to TPV systems enables a perfect match with In_0.69Ga_0.31As cells with a bandgap of 0.6 eV. Detailed theoretical calculations of this TPV system show that the power generation efficiency can exceed the Shockley-Queisser (SQ) limit (41%) at 1 117 ℃, and will be further improved as the emitter temperature increases. When the temperature reaches 2 000 K, the efficiency is as high as 46.75%. Additionally, the narrowband emitter shows good angular insensitivity in the range of 0~60 degrees.

The floating platform undergoes six degrees-of-freedom of motion in the marine environment, making the flow field around the blade fluctuate drastically, and the changing flow field will have a huge impact on the dynamic response of the blade. A two-way fluid-structure interaction simulation of the NREL 5 MW wind turbine was carried out using the CFD-CSD coupling method. Based on this, the UDF technique introduced the floating platform motion to study the blade deformation and the overall torque and thrust changes under the surge, pitch, and yaw motion. The results show that the three typical platform motions of the surge, pitch, and yaw make the blade deformation amplitude increase, and the increase of flapwise and torsional deformation is more significant than that of edgewise deformation; the surge motion has the greatest influence on the blade deformation and aerodynamic performance, the maximum change range of torsional deformation can reach 70%, the peak values of the torque and thrust are increased by 30.51% and 11.75% respectively; the pitch and yaw motions reduce the average torque and thrust.