The accident of steam generator tube rupture (SGTR) is one of the key scientific issues in the safety analysis of lead-cooled fast reactors (LFRs). It could lead to leakage of high-pressure steam and water into the molten metal and endanger the safe operation of the reactor. Due to the limited direct research on wet steam jets submerged in molten lead-bismuth eutectic (LBE), a transient numerical model was set up to investigate the multi-phase flow process with a complex heat and mass transfer mechanism. Only one flow pattern was found for the studied conditions, and it was similar to the continuous-jets in the superheated steam-LBE jets, and the jet parameters were larger for the wet steam-LBE jets, where the jet bubble volume could be a maximum of 3.27 times larger. The liquid water in the jets was found to evaporate quickly near the nozzle area, leaving only a small amount of liquid after the nozzle. And there were a water core area and a steam layer area along the radial direction. Besides, the sensible heat of the jet itself was found to contribute to a considerable proportion of the overall phase change heat, which could take up as high as 49.4%. Both initial and quasi-back-attack pressure shocks were observed, but the convergent-divergent pseudo-nozzle theory was not applicable under low pressures, due to the compressibility and density differences of the steam brought by the large content of liquid water.

The clean and low-carbon utilization of coal resources is a crucial aspect of energy transition for coal-rich countries. A substantial amount of CO2 generated from conventional coal utilization patterns can be effectively utilized by producing green hydrogen from renewable energy, providing a pathway to both carbon mitigation and efficient resource utilization. Furthermore, integrated energy systems represent an effective option for realizing synergistic complementarity and proximity absorption of heterogeneous energy sources. Therefore, a coal-based integrated energy system was devised. The CO2 from coal combustion is combined with hydrogen from renewable energy to synthesize methanol and methane. Methane is then combusted to supply external energy, while methanol simultaneously enables chemical carbon sequestration and can be sold as a byproduct, thereby achieving efficient and low-carbon utilization of the resources. The feasibility and operational performance of the system were further analyzed. The system can simultaneously achieve the clean and low-carbon utilization of coal and enable the joint supply of multiple energy products. The life-cycle carbon emission factors for power, heating, and cooling are 488.38 g/kWh, 49.61 kg/GJ, and 66.15 kg/GJ, respectively, and the system achieves net-zero emissions for methanol production, demonstrating its prominent carbon mitigation capability. The levelized cost of energy of the system is 154.52 $/MWh. Furthermore, the influence of technological development and energy policies on system evolution was discussed, with the levelized cost of energy projected to fall to 82.01 $/MWh by 2050. This study supports the low-carbon energy transition in coal-rich countries and provides a new perspective for the clean and low-carbon utilization of regional coal resources.

With the increasing penetration of renewable energy into power systems, coal-fired units are increasingly expected to respond rapidly to load variations. However, large and continuous load changes often lead to significant steam temperature fluctuations, threatening the safe and stable operation of the units. To address this issue, an improved adaptive fuzzy control system is proposed by incorporating the energy supply-demand deviation of the heating surfaces into the fuzzy control framework. The energy supply-demand deviation is utilized to dynamically adjust the fuzzy universe of discourse, enabling adaptive adjustment of the controller sensitivity according to the transient thermal state of the boiler. The proposed method is evaluated using a dynamic model of a 1000 MW coal-fired unit. The results show that the proposed control method effectively mitigates steam temperature fluctuations. In different load-up transient processes, the deviation range of the live steam temperature is reduced by an average of 1.7 °C, the cumulative error is decreased by an average of 33.0%, and the adjustment time is shortened by an average of 989 s. Meanwhile, in different load-down transient processes, the deviation range of the live steam temperature is reduced by an average of 2.1 °C, the cumulative error is decreased by an average of 26.2%, and the adjustment time is shortened by an average of 742 s. The proposed control method achieves more stable steam temperature regulation and provides an effective solution for improving steam temperature regulation in coal-fired units.

When a spacecraft executes missions within the solar system, the space background temperature of its heat radiation varies with its position. Nuclear power systems, offering high specific impulse and continuous energy output, are attractive for a broad spectrum of space applications, ranging from deep-space probes to longduration. To mitigate the risk of freezing in the cold-end heat pipes caused by a drop in the radiative environment temperature during operation of a spacecraft, a dynamic model integrating the reactor core, the Brayton cycle, and water heat pipe radiators was developed on the Simulink platform. By setting different space background temperatures (4 K to 230 K), the variation of the minimum operating temperature of the heat pipes with space background temperature was investigated, and the hazards of heat pipe freezing to the system were analyzed. A control strategy was proposed to counteract the freezing problem by regulating reactivity, helium-xenon circulation flow rate, and NaK flow rate in the system. The results show that freezing begins to occur in the heat pipes when the space background temperature drops to 160 K, and the proportion of frozen heat pipes increases sharply in the range of 160 K to 70 K. After implementing the control system, while ensuring that no freezing occurs in the cold-end heat pipes, the turbine inlet temperature fluctuation can be confined within 0.2 K and the fluctuation in power generation can be limited to within 0.74% when the space background temperature decreases. This significantly enhances the operational safety of space nuclear power systems during on-orbit operation.

In large-scale energy system engineering practices involving vapour jet condensation technology, the structure of the vapour jet is mainly based on circular-tube peripheral multi-hole structures, and the vapour condensation pressure oscillation is crucial to the safe operation of related equipment. Therefore, an experimental study was conducted to investigate the condensation pressure oscillation characteristics of the peripheral multi-hole vapour jet under experimental conditions where n = 3 and 5, I = 1.1-2.0, G = 150-400 kg m-2 & sdot;s-1, pvapour = 0.125-0.320 MPa and tw = 20-75 degrees C. The results show that the condensation pressure oscillation dominant frequency of the peripheral multi-hole vapour jet is primarily caused by the periodic collapse of vapour bubbles and the cyclic expansion and contraction of vapour plumes. The pressure oscillation dominant frequency decreases with increasing hole number and first increases and then stabilises as the hole pitch grows. The pressure oscillation intensity increases with the number of holes and first increases and then decreases as the hole pitch grows. At small hole pitches, bonding between adjacent jets weakens the condensation heat transfer between vapour and water, resulting in a lower pressure oscillation dominant frequency and pressure oscillation intensity. As the hole pitch increases, adjacent jets begin to separate, which enhances condensation heat transfer and causes the pressure oscillation dominant frequency to rise. At the same time, relative disturbance and collisions between the adjacent jets intensify, leading to an increase in pressure oscillation intensity. With further increases in hole pitch, the adjacent jets become fully separated and no longer interfere with each other, allowing vapour to condense independently and be stable in each jet. In addition, based on these findings, a dimensionless arc length ratio was proposed to represent the influence of hole number, and an empirical correlation was established, showing deviations of-18% to +25% from the experimental results, with an R2 of 0.83 and an RMSE of

The fluoride-salt-cooled high-temperature reactor (FHR) coupled with the SCO2 Brayton cycle (SCBC) system is a highly promising energy and power system. Therefore, in this study, the operational flexibility of the FHR-SCBC system is investigated. The load variation rate under the inventory control strategy is studied, using the temperature change rate as a constraint. The results show that significant changes in the thermophysical properties of SCO2 in the low-temperature recuperator (LTR) limit the flexibility of the system. In the load variation range from 100 % FP to 50 % FP, the maximum load reduction rate and maximum load increase rate are both 3 % FP/ min. To address the issues of low load variation rate and large temperature fluctuations, split ratio (SR) control and reactor cold leg temperature control are proposed. The maximum load reduction rate is increased by 9 % FP/ min, and the maximum load increase rate is increased by 8 % FP/min. On this basis, further investigations are conducted for load variation ranges and multiple temperature change rate constraints. It is observed that the flexibility of the system decreases significantly under low-load conditions.

The air Brayton cycle is distinguished by its high efficiency, flexible start-up and shutdown capabilities, and environmental friendliness—attributes that render it a suitable energy conversion system for mobile small-scale reactors. As a core component of this cycle, the air turbine plays a critical role in system performance. Given that mobile small-scale reactors operate under dynamically varying conditions, the fatigue damage of air turbines is crucial for safeguarding the safe operation of the entire cycle system. This study establishes a thermo-fluid-structure coupling and fatigue life analysis workflow based on the ANSYS platform, and investigates the effects of variable load rate and inlet temperature change rate on the fatigue damage of an air centrifugal turbine during its load transition from 75% to 100% of the design power. The results indicate that when the load rate is 12.5%Pe·min-1, the fatigue damage from a single load-transient process reaches a maximum of 2.25×10-6. When the inlet temperature change rate is 12 K·min-1, the fatigue damage from a single temperature-change process reaches a maximum of 2.119×10-6. Both the variable load rate and inlet temperature change rate exhibit a positive correlation with the fatigue damage of centrifugal air turbines.

Condensation-induced water hammer (CIWH) is a transient and potentially damaging phenomenon that is commonly encountered in phase-change thermal systems. Abrupt changes in pipe cross-sectional geometry are critical factors that influence the onset and severity of CIWH. By using a one-dimensional simulation code with an improved abrupt area change model, this study investigates the behavior of CIWH in pipelines that experience abrupt cross-sectional area changes. Results demonstrate that abrupt pipe expansion delays CIWH initiation, and the severity of CIWH intensifies due to vapor layer formation. Notably, the expansion ratio that corresponds to the pressure peak increases from 1.027 to 1.110 with rising flow rates. Abrupt pipe contraction exerts a negligible influence on CIWH initiation. However, once the contraction ratio exceeds a critical threshold, the formation of new isolated vapor bubble during liquid column reflux leads to CIWH with significantly larger-amplitude pressure oscillation. The contraction ratio that causes the pressure surge increases from 0.890 to 0.973 with rising flow rates. Furthermore, a momentum theorem-based theoretical formula that incorporates the pipe diameter abrupt change ratios is developed to predict the magnitude of CIWH. These findings provide critical insights into CIWH mitigation strategies for pipeline systems undergoing abrupt geometrical transitions.

Enhancing operational flexibility has emerged as a pivotal technical requirement in the transformation and modernization of coal-fired power plants. Among the various subsystems, the pulverizing system constitutes a primary factor constraining overall unit flexibility. Under transient load fluctuations, conventional PID control strategies frequently encounter limitations. Such systems often lack the responsiveness required to adapt effectively to rapid variations in outlet parameters. To address these challenges, a data-mechanism hybrid model of the pulverizing system was established. Based on the model, this study attempted to employ the advanced control algorithms to improve pulverizing system performance. Specifically, the effectiveness of a deep reinforcement learning (DRL)-compensated fuel control framework was evaluated, and the utilization of the deep deterministic policy gradient (DDPG) algorithm with additive compensation was proposed. The results showed significant improvements in control accuracy due to the capability of data representation and intelligent decision-making. Compared to the PID control system, the mean absolute error (MAE) of pulverized coal output using DDPG algorithm was reduced by 18%, while the MAE of unit power output decreased by 22%. The performance of the dynamic matrix control (DMC) algorithm was evaluated for the coupled regulation of mill hot and cold air valves. Relative to the PID control system, the multi-parameter DMC strategy significantly reduced the overshoot of the mill outlet temperature by 24% and the response time by 38%. Furthermore, the response time of the primary air flow rate was reduced by 18%, and the response time for suspended coal storage within the suspension zone decreased by 22%. In conclusion, the control strategy significantly strengthens the control performance of the pulverizing system and attains a notable enhancement in the operational flexibility of the coal-fired power plant.

Driven by the “dual carbon” strategic goals, the coal mining industry, characterized by high energy consumption and emissions, was faced with a severe challenge of green and low-carbon transition. To fully utilize associated resources within the mining area, such as coal mine methane, mine water, and waste heat from ventilation air, and to effectively consume local renewable energy, a multi-objective capacity configuration optimization method was proposed for a multi-energy complementary integrated energy system. A system architecture including photovoltaics, wind power, a gas internal combustion engine, heat pumps, and energy storage was constructed. A multi-objective model was then established with the goals of minimizing annual total cost, life-cycle carbon emissions, and maximizing energy utilization rate. The Mixed-Integer Linear Programming (MILP) method was used to generate a Pareto optimal set. Subsequently, the Entropy-TOPSIS method was applied to select a balanced solution. The impacts of resource uncertainty and reliability on the optimal configuration were quantitatively analyzed by constructing multiple fluctuation scenarios and a 48-hour islanded operation scenario. The results indicate that a significant conflict exists among the optimization objectives. The lowest annual cost (91.938 5 million CNY) is achieved by the economical optimal solution, but its carbon emissions are the highest (83 600 tons) and its energy utilization rate is only 83.59%. In the environmental optimal solution, carbon emissions are minimized to 63 800 tons through large-scale configuration of photovoltaics and energy storage, but its cost is high. The highest energy utilization rate (95.38%) is reached by the energy-efficiency optimal solution, but its economic cost is also the greatest. Through the balanced solution selected by multi-objective decision-making, a significant 11.7% reduction in carbon emissions is achieved with only an 8.8% increase in cost compared to the economical optimal solution. Simultaneously, the energy utilization rate is increased to 89.35%. An effective trade-off among the economic, environmental, and energy efficiency goals is thereby achieved.

To enhance the power enhancement potential of coal-fired power plants (CFPPs) under high renewable energy penetration, a novel integrated configuration combining molten salt thermal energy storage (MSTES) and steam ejector-assisted heat release is proposed in this study to improve the overall performance of the discharging system. Unlike previous studies focused on charging-stage optimization or direct steam reinjection, this work investigates the thermodynamic and economic performance of ejector-assisted MSTES discharge under different steam source matching and reinjection strategies. A thermodynamic simulation model was established for a 350 MW supercritical CFPP. Four ejector-assisted schemes and three reference schemes without steam ejectors were designed to examine the influences of steam source matching strategies and steam reinjection locations on power enhancement potential, thermodynamic characteristics, and economic performance. The results indicate that the system performance is highly sensitive to steam source parameters and reinjection locations. Among the investigated schemes, the scheme in which high-pressure extraction steam entrains molten-salt-generated steam and the mixed steam is reinjected into the governing stage of the intermediate-pressure turbine (IPT) delivers the largest power output increment of 19.71 MW, corresponding to a power output variation ratio of 5.63%THA, and also exhibits the best economic performance, with the shortest payback period of 1.57 years. By contrast, among the investigated schemes, the reference scheme with direct reinjection into the IPT inlet attains the highest system thermal efficiency and exergy efficiency, reaching 50.07% and 40.47%, respectively. Overall, the introduction of a steam ejector does not necessarily improve the integrated system performance; its effectiveness depends on the coordinated matching of steam source parameters and steam reinjection locations. The results provide useful guidance for the design and optimization of MSTES discharge-stage integration in CFPPs.

In lead-cooled fast reactors, steam generator tube rupture could lead to the discharge of high-pressure steam/water into lead or lead-bismuth eutectic (LBE) and result in several risks to the reactor's safe operation. Due to the differences in the physical properties of LBE and water and limited research in the steam-LBE jet flow, a compressible multi-phase numerical model was set up and used for the investigation of the submerged steam jet in LBE. The jet phase interface evolution pattern was found to be different under different inlet pressures, and the jet structure could travel to neighboring structures in a short time. Moreover, during the initial jet process, there was an initial pressure shock that might have an impact to nozzle itself and close structures along the jet direction. In addition, the (quasi-)back-attack phenomena were both observed, and a pseudo-nozzle structure was found to be responsible for the different patterns of the two phenomena. Those phenomena also brought pressure shock to the tube end, and the condition with an intermediate inlet pressure caused the fiercest pressure shock. Meanwhile, the wave structure at the phase interface was found to be resulted by strong shear flow.

Floating nuclear power plants (FNPPs) operating in ocean environments are continuously subjected to waveinduced rolling motions, which can strongly modify the condensation performance of the PCCS, particularly when non-condensable gases (NCGs) accumulate in the containment. In this work, a numerical framework is established to analyze film-wise condensation of steam-air mixtures on subcooled walls under rolling motion. The model couples an Eulerian description of the condensate film with diffusion-boundary-layer treatment of the gas phase, enabling detailed resolution of coupled momentum, heat, and mass transfer near the interface. Parametric simulations are carried out to examine the influence of roll amplitude and period, bulk gas-mixture velocity, and air mass fraction on the local and overall heat transfer behaviour. The results demonstrate that the rolling motion can substantially intensify condensation relative to stationary conditions. Under representative operating parameters, the CHTC increases from 447 W/(m2 center dot K) in the static case to more than 778 W/(m2 center dot K) with rolling, and the enhancement becomes stronger for larger rolling amplitudes and shorter periods. A nonmonotonic dependence on gas-mixture velocity is identified, with maximum enhancement occurring at intermediate flow rates. Increasing air mass fraction, however, markedly attenuates this benefit. These findings offer quantitative guidance for the design and safety evaluation of PCCSs on FNPPs under realistic marine motions.

Due to the change of working load caused by peak shaving and frequency modulation in power plants, the traditional fixed ejector cannot meet the requirements of high-performance operation under variable load conditions. However, the adjustable ejector with spindle has problems such as the length of the spindle is too long, and the anti-vibration measures are not in place. The spindle vibrates and deflects during the operation of the ejector. In this research, the influence of the structure deviation of the spindle on the ejector performance is evaluated by numerical simulation. The results show that the spindle of the adjustable ejector can obtain the maximum secondary fluid mass flow by controlling the primary fluid. Under different operating conditions, the entrainment ratio of the adjustable ejector is improved by 114.7% compared with that of the fixed ejector. The structural deviation will reduce the entrainment ratio and anti-back pressure capability, and the ejector will change from the critical mode to the sub-critical mode. The deviation between the spindle and the primary nozzle will change the flow field inside the primary nozzle, thus affecting the primary fluid ejection direction and the entrainment ratio.

The air-Brayton cycle has the characteristics of safety and high efficiency, which can be used as an energy conversion system for mobile small reactors. The air turbine is one of the key components in the cycle system, and improving its performance is of great significance. In this paper, an artificial neural network model combined with a genetic algorithm was used to optimize the rotor of an air centrifugal turbine with axial thrust and efficiency as the objective. The results show that the artificial neural network model can fit the CFD numerical simulation results well, with a coefficient of determination larger than 0.97. Then, after optimizing the artificial neural network model with a genetic algorithm, the total -total efficiency of the air centrifugal turbine was improved by 1.479 %, while the axial thrust was reduced by 1.07 %.

The integration of molten salt heat storage offers a promising solution for enhancing the operational flexibility of coal-fired power plants. In this study, a predictive control system was developed for the molten salt charging process. The aim of the control system was to adapt promptly to variations in unit load while maintaining precise control of the molten salt temperature. The research begins with the design of heat transfer equipment specifically tailored to meet the requirements of peak load regulation. Subsequently, a dynamic model of a thermal power unit integrated with a molten salt heat storage system is established to analyze the transient characteristics of the charging process. To optimize system performance, a multi-model dynamic matrix predictive control strategy is proposed, facilitating the coordinated regulation of heat storage extraction steam and molten salt flow rates. Performance evaluations indicate maximum control deviations of 0.64 MW in load and 0.85 degrees C in molten salt temperature, alongside a 27.56-s reduction in load regulation time. These findings highlight that the proposed control system significantly enhances system stability and response speed, demonstrating its potential for practical engineering applications.

In the pressure relief system of nuclear power plants, through multi-hole spargers, steam is blown off into subcooled water in the form of multi-hole steam jets. The flow pattern and heat transfer (HT) characteristics of multi-hole steam jets might differ greatly from single-hole steam jets, significantly affecting the system's performance. Thus, the transient flow pattern and HT characteristics of multi-hole steam jets were investigated, and how rolling motion affects the heat transfer characteristics was also investigated. Besides, forces acting on the steam volume were investigated for steam jets under different conditions, and the HT characteristics were explored from the perspective of force analysis. Compared with single-hole steam jets, the heat transfer coefficient (HTC) of multi-hole steam jets was significantly lowered, and the steam plume penetration length and phase interface area were much larger. Besides, the increase in hole number might advance the transition of the flow regime. Under rolling conditions, the HTC was larger but did not vary much with the rolling parameters. The dominant forces were different for different situations, and the weaker effect of rolling motion on steam jets in the condensation oscillation regime may result from smaller inertial force compared with steam jets in the chugging regime.

With the high penetration of renewable energy sources in China's power system, coal-fired power plants (CFPPs) fundamentally guarantee power supply and regulate power sources operating in load cycling and peak shaving. This paper established a dynamic model of the ultra-supercritical coal-fired power generation unit system to explore the potential of the ramp-up flexibility of CFPPs under deep peak shaving conditions. The load cycling rate is limited in low-load operation, and the fundamental reason lies in insufficient heat transfer capacity inside the boiler. Therefore, we propose a sliding temperature control strategy to improve the insufficient heat transfer capacity under low-load conditions and enhance the unit's flexibility from 30 % to 50 % Pe during the ramp-up process. The research results show that by adjusting the sliding temperature strategy, the boiler's operational stability and heat transfer performance are effectively improved, thereby enhancing the ability of CFPP to adjust the load rapidly. Step disturbances in feed water and coal feeding are carried out to test the performance of CFPP with four Schemes. With the sliding temperature Scheme, the necessary time to reach a new steady state is shortened by 15.33 %-21.22 %, and the maximum load cycling rate increased from 2.27 % to 3.37 % Pe min-1.

The swift advancement of renewable energy demands greater flexibility and enhanced peak-shaving capabilities from coal-fired power plants (CFPPs). Molten salt thermal energy storage (MSTES) is considered a potential solution. In this study, a CFPP integrated steam and flue gas stepwise/staged heating MSTES system is proposed. The proportion of steam heat energy allocated to the molten salt and feed water is adjusted. The thermodynamic and economic performance of two configurations under different thermal load distribution ratios are compared and studied. Results show that, under the same molten salt thermal load distribution ratio, the stepwise configuration achieves an average energy storage density that is 2.53 kWh/m3 greater than the staged configuration. Furthermore, it demonstrates a 3.82 % improvement in average denitration efficiency and a 1.28 MW reduction in average charging exergy loss. Economic analysis reveals that the integrated system performs best when the molten salt thermal load distribution ratio is minimized. At this time, the stepwise configuration demonstrates a 9.3 % lower life cycle cost, a 9 % lower equivalence levelized cost of electricity, and a 9.5 % lower equivalence levelized cost of thermal storage compared to the staged configuration.