29 January 2026, Volume 47 Issue 2

    

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  Analysis on Dynamic Response Characteristics of a 660 MW Ultra-supercritical Coal-fired Power Generation Unit During Wet State Operation

  LIU Zefeng, FAN Mengyang, YI Wencong, WANG Chaoyang, LIU Ming, YAN Junjie

  Journal of Engineering Thermophysics. 2026, 47(2): 371-379.

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  The main technical challenges for ultra-supercritical coal-fired power plants in low-load flexible operation are the long state conversion time between dry and wet state, and the unclear safety boundary for wet state operation. In this paper, a dynamic model of the wide-load operation of a ultra-supercritical coal-fired power generation unit and a water wall temperature analysis model were established. The dynamic response characteristics and the water wall temperature distribution after the boundary conditions change during wet state operation were discussed. The results show that when the water wall recirculation water flow increases by 20%, the economizer inlet water temperature will increase by 9.7°C, the under-enthalpy of the work medium entering the water wall will decrease, and the maximum wall temperature of the water wall will increase by 16.9°C. When the boiler fuel supply rate increases by 5.0%, the separator outlet temperature will increase by 4.2°C, the unit output power will increase by 4.1 MW, and the quality of the steam/water will increase. Under the limitation of wall overtemperature, the orderly utilization of heat storage in the recirculation system is conducive to achieving smooth, flexible, and safe state conversion during low-load operation.
  
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  Research on Coupling Characteristics of Compressed CO₂ Energy Storage and Carbon Capture Coal-fired Unit

  HU Dongzi, ZHAO Mingzhi, ZHU Yilin, XU Yujie, SHEN Guoqing, CHEN Haisheng

  Journal of Engineering Thermophysics. 2026, 47(2): 380-390.

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  Compressed Carbon Dioxide Energy Storage (CCES) technology has attracted much attention due to its advantages of large scale, environmental friendliness and easy coupling of carbon capture systems. In this paper, a new system for coupling compressed CO₂ energy storage and carbon capture coal-fired units is proposed. The system uses CO₂ captured by coal-fired units as the working fluid of CCES system, and realizes the deep coupling of carbon capture coal-fired units and CCES system through the comprehensive utilization of heat energy. In this paper, the thermodynamic model of the coupling system is built, and the thermodynamic characteristics of the system are analyzed to obtain the optimal coupling mode of the CCES system and the carbon capture coal-fired unit. The results show that compared with the carbon capture coal-fired unit, the thermal performance optimization effect of the coupling system increases with the increase of the energy storage and release time ratio. When the energy storage and release time ratio is 2.16, compared with the carbon capture coal-fired unit, the thermal efficiency and exergy efficiency of the coupling system increase by 0.45% and 0.37% respectively, and the coal consumption decreases by 24.9 g/kWh. The energy storage efficiency of the CCES system is 70.7%. This study is of great significance for the development of CO₂ energy storage technology and the realization of dual-carbon goals.
  
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  Molecular Dynamics Study of Vapor-Liquid Interface in the CH₄-C₂H₆-CO₂ System Containing Azeotropes

  LIU Junming, LIN Wensheng

  Journal of Engineering Thermophysics. 2026, 47(2): 391-398.

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  The low-temperature distillation separation technology utilizes the boiling point differences of various hydrocarbon components in associated gases to gradually condense and separate light hydrocarbons into products. This process is essentially a complex coupled phenomenon of fluid flow, heat transfer, and mass transfer, which becomes even more intricate when azeotropic phenomena are involved. This study employs molecular dynamics simulation to investigate the vapor-liquid interfacial characteristics of the CH₄-C₂H₆-CO₂ ternary mixture at low temperatures. Initially, different molecular force field models were used to construct the initial vapor-liquid interface, and the accuracy of the models was validated. Subsequently, the behavior of the ternary mixture at various temperatures was simulated to analyze the density distribution, stress distribution, and azeotropic phenomena at the vapor-liquid interface. The results indicate that C₂H₆-CO₂ forms a binary azeotropic mixture under specific conditions, and temperature variations significantly affect the structure and characteristics of the vapor-liquid interface. This research provides an important microscopic perspective for understanding vapor-liquid interfacial phenomena in low-temperature distillation and offers a theoretical basis for optimizing related separation processes. 
  
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  Configuration Modeling and Analysis of Storage System in Mobile Hydrogen Refueling Station for Trains

  FENG Luoyi, CAI Liming, XU Hanlin, XIE Xing

  Journal of Engineering Thermophysics. 2026, 47(2): 399-411.

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  With the technological advancement of hydrogen trains around the world, the continuous breakthrough in the demand for long range has increased the difficulty of matching the design of hydrogen refueling stations. Mobile hydrogen refueling stations meet the operational requirements of trains well due to its maneuverability, but requiring the integration of all components within a specified enclosed space. Reducing the volume of the storage system is of importance for mobile hydrogen refueling stations to lower its cost, increase the hydrogen utilization rate, and decrease the footprint. In this work, the configuration modeling and analysis of the storage system for mobile hydrogen refueling stations oriented to trains are carried out. Firstly, the number of pressure divisions and switching points of the station storage system are optimized, and a 7-division average pressure multi-division strategy is proposed. A thermodynamic model is established from the station side to the vehicle side, then the refueling process of the proposed multi-division strategy is simulated under different number of refueling guns. The results show that: 1) with the increase of the number of pressure divisions, the volume of the storage system decreases, and the average pressure multi-division strategy corresponds to a smaller volume; 2) the mass flow rate increases with the number of refueling guns increases, leading to a shorter refueling duration, higher peak temperature and precooling peak power, lower refueling mass and precooling specific energy consumption. Considering the refueling time and precooling power consumption, the optimized configuration to meet the target refueling mass (500 kg) and duration (30 min) is a 7-division average pressure multi-division strategy with parallel refueling of 4-guns. This study provides an reference for the design of hydrogen refueling stations for trains.
  
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  Thermodynamic Performance and Economic Analysis of Molten Salt Energy Storage Integration in Subcritical Coal-fired Power Units

  QI Yanchao, HONG Wenpeng

  Journal of Engineering Thermophysics. 2026, 47(2): 412-425.

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  With the growing penetration of renewable energy in power grids, enhancing operational flexibility of existing coal-fired units becomes crucial for grid stability. This study proposes a novel molten salt energy storage integration scheme using combined main steam and reheat steam extraction in a 315 MW subcritical coal-fired unit, developing three distinct thermal storage configurations: steam cycle return to condenser, low-pressure cylinder operation, and steam ejector-driven exhaust heat utilization. A comprehensive thermodynamic evaluation based on energy and exergy analysis reveals that the MR-C-a system (combined storage/release operation) achieves optimal performance with 16.19% peak-shaving depth, attaining 50.92% cycle efficiency and 482.198 g/kWh comprehensive coal consumption. Exergy analysis identifies the storage/release subsystem as the critical efficiency determinant, with MR-C-a demonstrating superior exergy efficiency of 37.866%. Parametric studies indicate that elevating the high-temperature storage tank (R1) operating temperature significantly enhances system exergy efficiency. Economic analysis shows a 9.22-year payback period, with peakshaving duration exhibiting greater impact on investment recovery than discount rate. This research provides theoretical foundations and engineering insights for deep peak-shaving retrofits in coal-fired power plants.
  
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  Optimization Study on the Performance of Plate-layer AER Devices Based on Nanofluid

  CHU Zhaoping, HAN Hua, ZOU Yongqing, CHEN Hao

  Journal of Engineering Thermophysics. 2026, 47(2): 426-436.

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  Electrocaloric refrigeration, as a novel solid-state refrigeration technology, is widely used in chip cooling and other fields. This study investigates a parallel plate active electrocaloric regenerator (AER) using nanofluid as the heat transfer medium, characterizing its geometric features with the flow-solid ratio and focusing on the effects of cycle period and structural parameters on device performance.The results indicate the existence of an optimal cycle period (τ ), an optimal number of electrocaloric material layers (N_EC), and an optimal flow-solid ratio (κ). The best switching of the electric field occurs when the heat transfer reaches approximately two-thirds of the maximum possible heat transfer (τ = 9 s). Under the same cycle period, the maximum refrigeration capacity (8.49 W) is achieved at N_EC = 10 layers, with a COP of 6.91. When the channel height is fixed, for κ > 0.3, the improvement in PVDF thermal conductivity cannot compensate for the decline in adiabatic temperature change, leading to reduced cooling capacity. With a fixed material thickness, increasing κ enhances the heat exchange area; however, excessive κ fails to compensate for the decline in convective heat transfer intensity, with the maximum refrigeration capacity (4.72 W) occurring at κ = 0.525. Material thickness has a more significant impact on COP than channel height. Properly matching the electrocaloric effect with thermal conductivity can improve device performance.
  
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  Optimization Design of Wind-solar-ground-storage Distributed Energy System Based on Particle Swarm Optimization Algorithm

  REN Qianru, SUN Xiangyu, MENG Jianlong, CAI Chang, LIU Qian, ZHONG Xiaohui, LI Qing’an

  Journal of Engineering Thermophysics. 2026, 47(2): 437-443.

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  With the proposal of the “double carbon” goal, the efficient utilization of renewable energy such as wind energy, solar energy and geothermal energy is an important part of the transformation and upgrading of the energy system. In this paper, a wind-solar-ground-storage distributed energy system with wind-to-heat unit, photovoltaic-thermal integration, shallow geothermal utilization and heat storage device as the core is constructed. Based on the particle swarm optimization algorithm, the whole life cycle cost is taken as the objective function, including construction cost, operation and maintenance cost and energy purchase cost, and the capacity optimization configuration of key components is carried out. Finally, the optimal life cycle cost is 91.781306 million CNY. The system can effectively improve the utilization efficiency of renewable energy, reduce the overall economic cost of the energy system, and provide a new technical path for clean heating. 
  
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  Research on Transonic Non-equilibrium Condensation Flow and Shock Wave Characteristics of H₂O/CO₂ Mixed Gas

  SHI Haibo, HAN Xu, YAO Bochuan, WU Xuwei, LI qi, HAN Zhonghe

  Journal of Engineering Thermophysics. 2026, 47(2): 444-450.

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  The supercritical water gasification hydrogen production cycle power generation system is an innovative clean coal utilization technology. Under supercritical conditions, coal is ultimately converted into a H₂O/CO₂ gas mixture that enters the turbine for power generation. However, non-equilibrium condensation of water vapor occurs in the final turbine stage, leading to blade water erosion accompanied by complex shock wave phenomena. Based on current domestic and international research progress, this study employs an MS nozzle as the research object to numerically investigate the condensation flow characteristics of H₂O/CO₂ mixtures. The effects of CO₂ mass fraction and backpressure variations on flow parameter distributions and shock wave morphology are systematically analysed. Key findings include: the addition of CO₂ significantly alters the condensation characteristics of the working fluid. When the CO₂ mass fraction increases from 0 to 0.4, the condensation zone shifts toward the outlet, accompanied by a 5.24 K decrease in outlet temperature and a 2.28% reduction in liquid phase mass fraction; elevated backpressure drives aerodynamic shock waves upstream, while condensation-induced shock waves remain positionally stable, when aerodynamic shocks overlap the condensation zone, the nucleation rate approaches zero; under constant backpressure conditions, increasing CO₂ concentration does not alter shock wave positions but markedly enhances shock wave intensity.
  
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  Research on the Overflow Flow Field Characteristics for the Multi-stage Shaft Seal of Steam Turbine Under Different Operational Conditions

  WAN Hongting, YANG Zhi, ZHAO Tian, Yang Junjun, Fan Siyi, PENG Shuxuan, FU Jinglun

  Journal of Engineering Thermophysics. 2026, 47(2): 451-465.

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  The shaft seal of the steam turbine is a key component of the steam turbine, in flexible operating conditions, studying its flow field characteristics under different working conditions having a great significance to improve the performance of the equipment, ensure the safe operation and reduce the energy consumption. The three-dimensional flow in the multi-stage shaft seals for high and middle pressure turbine under different operational conditions were numerically investigated in this paper. The flow coefficients under different pressure ratios were calculated from numerical simulation results. The influence of the pressure ratio and the structure on the leakage and flow field of the shaft seal were analyzed. Results showed that with the increasing of the pressure ratio, the leakage of the shaft seal to the main stream pipe became larger. The coupling of the first stage shaft seal with lower sealing performance and the second and the third stage with higher sealing performance helped to reduce the percentage of steam flowing to the shaft-end heater, improving the heat exchange efficiency. With the increase of the pressure ratio from seal inlet to outlet, the flow patterns in the three stages shaft seal were slimily, but the local peak values of Mach number at sealing clearance, the strength and size of the vortex in the shaft seal raise. For the same structural design, the impact of energy dissipation caused by vortex intensity on the leakage of the shaft seal was less significant than that of pressure ratio; Under the condition of high pressure ratio, the staggered structure of double short tooth and boss could reduce the flow coefficient of the middle pressure first stage shaft seal by 1.5%. While under the condition of low pressure ratio, increasing the number of long teeth could reduce the flow coefficient of the high pressure second and third stage shaft seals by about 27.36% and 10.56%. In order to quickly evaluate the leakage of the shaft seals under any pressure ratio, the relationships between the flow coefficients, overflow of high and middle pressure shaft seals and pressure ratio were found out, which could predict the leakage and overflow exactly. 
  
  
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  Effect of the Medium Memperature on the Performance of the Space Liquid-cooled Circulating Pump

  AN Dongsen, HAO Kaiyuan

  Journal of Engineering Thermophysics. 2026, 47(2): 466-475.

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  The space liquid-cooled circulating pump usually works in a complicated temperature environment. The physical properties of the circulating medium are different at different temperatures, which has a great influence on the performance of the pump. Taking a liquid-cooled circulating pump with perfluorotriethylamine as the research object, the operation of the pump at different temperatures was numerically calculated. The results show that the main frequency amplitude of the power and pressure pulsation increases greatly with the decrease of the temperature and the decrease of the pump head and efficiency. The effect of low temperature on the performance of the pump is more serious. Compared with that of the pump at −40°C, the head and efficiency are reduced by 10% and 35% respectively, the power is increased by 53%, and the main frequency amplitude of the volute pressure pulsation is increased by 34% on average. According to the analysis of flow characteristics, low temperature makes the viscosity of the medium increase, the viscosity of the impeller decrease, the flow loss in the pump and the wear power of the rotor wall increase, which results in the decrease of the lift and efficiency. The increase of main frequency amplitude of low-temperature pressure pulsation is related to the strong vortex structure.
  
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  Analysis of the Influence of Turbulence Models on Gas-liquid Flow Characteristics in Rotodynamic Pump

  LI Huichuang, ZHANG Yi, TANG Yiping, ZHU Jianzhong, ZHANG Wenwu, YAO Zhifeng, WANG Fujun

  Journal of Engineering Thermophysics. 2026, 47(2): 476-482.

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  To explore the influence of different turbulence models on gas-liquid flow characteristics in rotodynamic pump, an axial-flow rotodynamic pump was chosen as the research object. Four turbulence models, namely k-ε, RNG k-ε, Baseline k-ω, and SST k-ω, were used to conduct numerical simulations of the gas-liquid flow in the rotodynamic pump under four inlet gas volume fraction conditions (5%, 9%, 12%, and 15%). The results show that the SST k-ω turbulence model demonstrates better agreement with experimental data in predicting both the pressurization and gas distribution within the rotodynamic pump However, the Baseline k-ω, k-ε, and RNG k-ε turbulence models have significant errors in predicting pressurization under high inlet gas volume fraction condition. Moreover, the k-ε and RNG k-ε turbulence models overestimate the gas volume fraction at the guide vane inlet. Therefore, the SST k-ω turbulence model is recommended for numerical simulation of the gas-liquid flow in rotodynamic pump.
  
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  Research on Structural Response of Ultra-long Flexible Wind Turbine Blades Based on Equivalent Plate

  LIAO Weiliang, ZHANG Mingming, FENG Yu, XU Nuo, WEI Yi

  Journal of Engineering Thermophysics. 2026, 47(2): 483-491.

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  For the structural response prediction of ultra-large, hundred-meter-scale flexible wind turbine blades, an equivalent plate model based on the blade section chord line is proposed to describe the wind turbine blade. Based on this equivalent plate model, research is conducted on the equivalence of aerodynamic loads and structural deformations. An equivalent aerodynamic force chordwise distribution calculation method is developed based on Blade Element Momentum theory. Structurally, the blade’s thickness, density, and stiffness distributions are characterized using multiple sectional feature parameters. This approach significantly reduces computational complexity and degrees of freedom while ensuring the accuracy of the global dynamic characteristics of the model. The results demonstrate that the equivalent aerodynamic loads and equivalent structural responses exhibit high accuracy in validation comparisons, making this method suitable for static and dynamic response analysis of wind turbine blades. This provides a novel computational framework for studying the dynamic response of hundred-meter-scale wind turbine blades.
  
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  Molecular Dynamics Simulation of Thermal Properties of Aviation Kerosene JP-10

  WEN Mingrui, WANG Shuai, JIN Hanhui, FAN Jianren

  Journal of Engineering Thermophysics. 2026, 47(2): 492-497.

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  Fuel performance is the key factor in determining the effectiveness of propulsion systems for long-distance and high-thrust applications. Due to extreme temperatures and pressures in practical engineering applications, it is difficult to obtain the thermal and physical property parameters of domestic aviation kerosene JP-10 through experiments, which limits its use in aerospace fields. To address this, this study uses molecular dynamics simulations to investigate the effects of different time steps (0.1 fs and 1 fs) and different force fields (GAFF2 and OPLS) on the dynamic viscosity and thermal conductivity of JP-10 under conditions of 300 K and 1.48 MPa. The results show that, considering both the computational cost and error, using the OPLS force field with a time step of 1 fs is more suitable for describing the property changes of JP-10. This provides technical support for the study of atomized combustion of energetic particle gel fuels. 
  
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  Bubble Formation, Liquid Block-leakage and CO₂ Mass Transfer in Rectangular Straight Channels

  LIU Ye, JIA Li, DANG Chao, SUN Xiaozhe

  Journal of Engineering Thermophysics. 2026, 47(2): 498-503.

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  Carbon capture technology is an effective strategy to reduce greenhouse gas emissions. In this study, a high-speed camera system was used to investigate the process of absorption of CO₂ in a mixed gas by an ethanolamine within a small-scale rectangular straight channel. The flow characteristics of Taylor bubbles and the quantitative analysis of liquid leakage flow were explored, aiming to discover the mass transfer characteristics of CO₂ absorption process in a small-scale rectangular straight channel. The concept of volume correction factor was proposed. The leakage degree of leakage flow when the liquid flow rate increases was quantitatively analyzed. The effects of different monoethanolamine solution concentrations (3%, 5%, 10%) and liquid flow rates (15∼70 mL·min⁻¹) on leakage flow were investigated. The results indicated that during the gas-liquid flow process, appropriate leakage flow promoted the absorption and mass transfer of CO₂. Additionally, an increase in bubble travel velocity was found to enhance the concentration gradient surrounding the bubble, thereby promoting mass transfer between the gas and liquid phases.
  
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  Analysis of Gas-liquid Two-phase Flow and Heat Transfer Performance in Gravity Heat Pipes With Different Liquid Filling Ratios

  GUO Hao, CHEN Jiangbo, NIE Tingting, WANG Zhiming, WANG Tieying, LI Xueqiang, LIU Shengchun, JI Xianbing

  Journal of Engineering Thermophysics. 2026, 47(2): 504-511.

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  The effects of filling ratios and tilt angles on the gas-liquid two-phase flow and heat transfer performance in gravity heat pipes was investigated in this article. The gas-liquid two-phase flow inside the heat pipe was observed using visualization. The liquid filling ratios range from 23% to 69% in the experiment, with tilt angles at θ = 90°, 60°, and 30°. The results indicate that geyser boiling is more likely to occur at low heating powers and high liquid filling ratios. At low heating powers, geyser boiling can enhance the evaporation and condensation heat transfer. However, it exhibits a suppressive effect at high heating powers. After reaching the entrainment limit, temperature rise is observed when the filling ratio is 23%. For φ = 46% case, long-term temperature fluctuations and a continuous decline of the heat transfer coefficient are noted. However, when the filling ratio reach 69%, oscillations of the working fluid occur internally, leading to instability in the operation of the gravity heat pipe.
  
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  High-resolution CFD-DEM Simulation of Biomass Fast Pyrolysis Based on Direct Solving Transport and Reaction Process Inside Thermally-thick Particles

  WANG Kui, REN Guanlong, XU Ji, GE Wei, XIONG Qingang

  Journal of Engineering Thermophysics. 2026, 47(2): 512-520.

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  The precise modeling of the transfer and reaction process in the thermally-thick particles is an attractive and difficult problem in the computational fluid dynamics (CFD) simulation of biomass fast pyrolysis. To solve this problem, a transfer and reaction model was constructed in which multiple shells were directly solved in spherical particles. The discrete element method (DEM) was used to simulate the biomass fast pyrolysis process in bubbling beds with high precision. The experimental data of pyrolysis of single thermally-thick biomass particles and biomass pyrolysis of lab-scale bubbling bed verified the accuracy of the direct solution of the intra-particle transfer and reaction model and explored the characteristics of biomass pyrolysis of lab-scale bubbling bed and the influence of operating conditions. The results show that the accuracy of the CFD-DEM simulation of biomass fast pyrolysis can be significantly improved through the direct solution of the thermallythick particles transfer and reaction model, as it can describe the significant difference in the pyrolysis degree caused by the significant temperature gradient in the thermally-thick particles. In the study of the influence of operating conditions on the biomass fast pyrolysis in the bubbling bed, it is found that the tar yield of biomass particle pyrolysis first increases and then decreases with the increase of temperature, and the optimal pyrolysis temperature is 773 K. The results of the pyrolysis of different kinds of biomass show that the tar yield increases slightly with the increase of cellulose composition, and the tar yield of pure cellulose pyrolysis is the highest.
  
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  Hydrodynamic Interactions During Side-by-side Bubbles Evolution Process Based on CFD-DEM in a Wet Particle Fluidized Bed

  TANG Tianqi, SUN Shanshan, HE Yurong

  Journal of Engineering Thermophysics. 2026, 47(2): 521-527.

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  Bubble is a typical mesoscale structure, and has attracted more and more attention due to its various meso-scale structure evolution. In many industrial processes, bubbles are also important in promoting mixing, heat, and mass transfer rates. In this work, interaction between two bubbles and evolution processes are analyzed from macro, meso scales by numerical simulation. An interesting phenomenon of two bubble interaction and collapsing is found. Two bubbles rise with different growth rate, although two bubble are injected and generated at the same time. This phenomenon agrees with the experimental results (Physical Review Fluids, 2019, 4(3): 034303). The left bubble inhibits and squeezes the right bubble, which results in the right bubble moving upwards faster with a higher bubble shape ratio. With an increase of liquid content, bubble evolution processes are inhibited, and the bubble size, shape and growth rate are reduced and become more irregular.
  
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  Experimental Investigation on the Flow and Heat Transfer in Pseudocritical Region of SCO₂ in Microchannel Heat Exchanger With Serpentine Channel

  CHEN Zhentao, WANG Xiaomu, BAI Bofeng

  Journal of Engineering Thermophysics. 2026, 47(2): 528-538.

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  Supercritical carbon dioxide (SCO₂) has a drastic change of thermophysical properties in the pseudocritical region, which significantly affects the flow heat transfer performance. This study experimentally investigated the flow heat transfer characteristics of SCO₂ within a microchannel heat exchanger with serpentine channel at temperature range of 308.15∼473.15 K, pressure range of 7.4∼9.6 MPa, and Re range of 11200∼70000. It is found that when T_b/T_pc of SCO₂ is between 1∼1.08, the drastic change of thermophysical properties leads to the rapid increase of the heat transfer coefficient and drag factor, and the heat transfer coefficient reaches the maximum value near the T_b/T_pc of 1. The flow and heat transfer prediction model established by regression fitting to the experimental results has a prediction error of ±25%. In contrast, the artificial neural network method can effectively consider the nonlinear variation of thermophysical properties, the prediction error of trained Nu is less than ±10%, and 98% of the prediction error of trained f is less than ±15%, which significantly improves the prediction accuracy of the model.
  
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  Cryogenic Condensation Characteristic Research of Nitrogen Transonic Expansion in Nozzle

  WANG Xiaoyi, WANG Yuanjing, LI Yuchen, LIU Fengxiao, LIU Dawei, ZHAO Hongli, NIU Lu

  Journal of Engineering Thermophysics. 2026, 47(2): 539-550.

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  For cryogenic spontaneous condensation occurrence under increasing Reynolds number in aerodynamic experiments for modern aircraft, a novel ground cryogenic high-speed experimental apparatus is applied to conduct experimental and CFD research of non-equilibrium condensation flow in a Laval nozzle, and reliable experimental results are provided for accurate prediction method establishment. In experimental research, pressure measurement distribution on nozzle wall surface under total temperature range of 97.5∼105 K are obtained, and “condensation shock” is figured out by compared with the pressure distribution of the no condensation case. Then, nucleation models of CNT (Classic Nucleation Model) and CNT-K (Kantrowitz correction) are applied in our numerical work, and the results shows that CNT-K model with nucleation correlation factor f = 0.22 agrees with experiment data well.
  
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  Numerical Simulation Study on Continuous Ortho-para Hydrogen Conversion in a Printed Circuit Heat Exchanger

  LAI Jiajia, TENG Junjie, WANG Kai

  Journal of Engineering Thermophysics. 2026, 47(2): 551-560.

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  The Printed Circuit Heat Exchanger (PCHE), distinguished by its superior heat transfer efficiency, excellent pressure loading capacity and extended lifespan, demonstrates significant potential for hydrogen liquefaction. This study employs numerical simulations to investigate the thermalhydraulic and the continuous ortho-para hydrogen conversion performance in a semi-circular straight channel PCHE filled with catalysts in the temperature range of 30∼40 K. The analysis particularly focuses on the effects of mass flow rates and operating pressures on the catalytic conversion side. Key findings show that with a hot-side Reynolds number of 461, the temperature difference between the hot stream outlet and the cold steam is less than 1 K while the para-hydrogen fraction exceeds 90%, indicating the feasibility of continuous ortho-para hydrogen conversion with a PCHE filled with catalysts. The abrupt thermophysical property variations of hydrogen near the pseudo-critical temperature region are shown to degrade thermal performance on the catalytic side. Parametric analyses reveal that reducing the hot-side Reynolds number from 1212 to 606 at 2.1 MPa enhances the Performance Evaluation Criteria (PEC) by 59.8% and the conversion efficiency (η_CON) by 2.37%. Furthermore, increasing the hot-side operating pressure from 2.1 MPa to 8 MPa under a fixed mass flow rate corresponding to a Reynolds number of 606 at 2.1 MPa elevates PEC by 104% and η_CON by 2.01%. These results imply the pronounced sensitivity of PCHE performance to both the mass flow rate and operating pressure.
  
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  Deformation Characteristics of Compound Droplets in a Microfluidic Chip

  XUE Yifan, YANG Jiawang, HE Yongqing, YANG Wei, ZHU Hengxuan, DU Hongxian, WANG Jin

  Journal of Engineering Thermophysics. 2026, 47(2): 561-567.

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  The deformation characteristics of compound droplets in microfluidic chips are of great reference value for research on cell screening and drug delivery. In this paper, a viscous droplet and viscous cell model are established. The VOF method is adopted to study the compound droplet’s inlet pressure, shear force, and other parameters when extruded through a narrow channel in a microchannel with a low Weber number to derive the kinetic properties of the compound droplet during transport. Results show that when the Weber number is high, the stability of compound droplets decreases, which is not conducive to the recovery of the initial state after passing through the narrow channel When the Weber number is too low, the cell deflection is intensified, resulting in direct contact between the cells and the carrier fluid, which leads to the fragmentation of the compound droplets.
  
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  Numerical Study and SVR Prediction on Heat Transfer Characteristics of Pebble Beds With Internal Heat Sources

  WANG Mouhao, BU Shanshan, ZHOU Bing, GONG Baoping, LI Zhenzhong, CHEN Deqi

  Journal of Engineering Thermophysics. 2026, 47(2): 568-577.

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  Pebble beds, as an important form of packed bed, serve as an ideal platform for heat and mass transfer between solid media and fluid working substances. Previous studies by the authors have shown that traditional heat transfer correlational models have limitations in predicting the heat transfer characteristics of pebble beds with internal heat sources. In this paper, based on our previous research, the heat transfer characteristics of fusion breeder pebble bed with internal heat sources are studied by numerical simulation and Support Vector Regression (SVR) machine learning method. The results indicate that local non-equilibrium thermal effects within the breeder pebble bed can be neglected, but the heating effect of the particles with internal heat sources significantly influences the properties of helium gas. Incorporating the property changes of helium into the proposed SVR model, the maximum prediction deviation for the heat transfer coefficient of the pebble bed is within 3%, showing superior prediction accuracy compared to traditional models (which exceed 54% in maximum prediction deviation). This work provides a reference for the design and evaluation of pebble beds with internal heat sources.
  
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  The Impact of Gradually Expanding Three-Dimensional Wavy Channels on Water and Gas Transport and Performance in PEMFCs

  WU Wei, LI Wenhao, DU Changqing

  Journal of Engineering Thermophysics. 2026, 47(2): 578-587.

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  The shape of the cathode flow channel has a significant impact on the gas distribution, drainage performance of the microporous layer, and output performance of proton exchange membrane fuel cell. In this study, a three-dimensional non-isothermal two-phase flow model was developed to investigate the influence of expanding flow channels and three-dimensional wavy flow channel structures on the output performance of fuel cell. A dual enhancement scheme for an expanding three-dimensional wavy flow channel was proposed. The study also explored the effects of this channel structure on the diffusion and transport of reaction gases inside the PEMFC, the elimination of liquid water in the microporous layer, and the output performance. The results indicate that both expanding flow channels and three-dimensional wavy flow channels can enhance the output performance of the fuel cell, with maximum power density increases of 4% and 1.13%, respectively. The dual-enhanced expanding three-dimensional wavy flow channel not only promotes oxygen diffusion transport but also improves the ability to eliminate liquid water, resulting in a maximum 4.6% enhancement in drainage performance. This enhances the output characteristics of the cell, with a maximum power density increase of 4.04%.
  
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  Numerical Investigation of CO₂ Catalytic Conversion in Tubular Reactor

  LIU Jianchen, DAI Xiaoye, SHI Lin

  Journal of Engineering Thermophysics. 2026, 47(2): 588-596.

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  This study employed a numerical simulation approach to investigate the catalytic conversion process of CO₂ in a tubular reactor. The effects of inlet gas temperature, wall temperature, inlet velocity, and reactor diameter on reaction conversion efficiency and CO₂ reaction throughput were systematically analyzed. The results demonstrate that, with the exception of inlet gas temperature, wall temperature, inlet velocity, and reactor diameter significantly influence the conversion efficiency. Specifically, higher wall temperatures, lower inlet velocities, and smaller reactor diameters were found to enhance conversion rate. However, lower inlet velocities and smaller diameters led to a reduction in the CO₂ reaction rate per unit time. These findings highlight the necessity of balancing conversion efficiency with reaction throughput during reactor design optimization to achieve optimal operational performance. The study provides critical insights for parameter selection and performance enhancement in tubular reactor systems for CO₂ catalytic processes. 
  
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  Boiling Heat Transfer Characteristics of HFE-7100 in Silicon-based Distributed Jet Microchannel

  LIU Jinya, WU Huiying, HUA Xia, LIU Zhenyu

  Journal of Engineering Thermophysics. 2026, 47(2): 597-604.

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  The silicon-based distributed jet microchannel heat sink integrated with micro-heater and temperature detectors is constructed in this paper for achieving high heat flux chip-level cooling. The flow boiling heat transfer characteristics in the jet microchannel at different jet velocities (0.86∼2.58 m·s⁻¹) and inlet subcoolings (21∼41°C) are experimentally investigated using HFE-7100 as the working fluid. The results reveal that: the critical heat flux (CHF) and coefficient of performance (COP) of the jet microchannel are as high as 463 W·cm⁻² and 2205 respectively, while the pressure drop does not exceed 44.4 kPa. Increasing the jet velocity and inlet subcooling can increase CHF, but will delay the onset of nucleate boiling (ONB). With the increase of jet velocity, the heat transfer coefficient and pressure drop increase, and the effective thermal resistance decreases. With the increase of inlet subcooling, the curves of the heat transfer coefficient, pressure drop, and effective thermal resistance move to the right.
  
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  Rational Design of Nucleotide-Derived Catalysts Based on ZIF-8 for Enhanced Oxygen Reduction Performance

  WANG Jiapeng, SONG Bingye, ZHANG Mengfan, DU Zexuan

  Journal of Engineering Thermophysics. 2026, 47(2): 605-610.

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  The high cost of platinum-based carbon (Pt/C) catalysts for the oxygen reduction reaction (ORR) remains a major obstacle to the commercialization of fuel cells. In this work, a novel metal-free nitrogen-doped carbon (N/C) catalyst was developed as an alternative to conventional Pt/C. During the synthesis, the controlled dissociation of cobalamin (vitamin B12) was employed to generate 5,6-dimethylbenzimidazolyl nucleoside phosphate, which subsequently participated in a co-precipitation reaction with zinc nitrate and 2-methylimidazole. Thereby, the nucleation kinetics of ZIF-8 can be significantly accelerated, successfully yielding N-ZIF-8 precursor with abundant surface functional groups and a controlled particle size less than 100 nm. After the pyrolysis process, a N-doped carbon (N/C) catalyst with enriched pore structures and enhanced oxygen reduction reaction (ORR) active site density can be obtained. Electrochemical characterization revealed that the as-prepared N/C catalyst exhibited an exceptional ORR activity in 0.1 mol/L alkaline electrolyte, matching state-of-the-art Pt/C benchmarks with an onset potential of 1.135 V (vs. RHE), a half-wave potential of 0.808 V (vs. RHE) and a limiting current density of −5.58 mA·cm⁻².
  
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  Research on Regulation of Thermal Conductivity in Semiconductor Materials by Phonon’s Wave Effect

  LI Weikang, XU Jiaxuan, HUANG Xiaoyu, NI Yuxiang, BAO Hua

  Journal of Engineering Thermophysics. 2026, 47(2): 611-617.

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  Thermoelectric materials have garnered significant attention due to their great potential in waste heat recovery and addressing energy challenges. Reducing the thermal conductivity of semiconductor materials is one of the most critical approaches to enhancing the efficiency of thermoelectric materials. Phonon resonance and phonon localization are two commonly used methods to regulate material’s thermal conductivity through phonon’s wave effect. This paper proposes a computational method for isolating the contubution of wave effect from thermal conductivity. Using the phonon Boltzmann transport equation and non-equilibrium molecular dynamics simulations, our result demonstrates that phonon resonance and phonon localization can be simultaneously introduced to further reduce the thermal conductivity of silicon-germanium superlattice nanowires, thereby providing valuable insights for the design of thermoelectric materials. 
  
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  Machine Learning-based Study on Coking Characteristics in Fuel Heat Exchangers for Aero-engines

  JIANG Tao, LI Mingjia

  Journal of Engineering Thermophysics. 2026, 47(2): 618-624.

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  Fuel-air heat exchangers in aero-engines face coking risks under high-temperature conditions, compromising their cooling performance. To investigate the influence of fuel coking on the thermal performance of heat exchangers and enable refined design, this study employs three machine learning algorithms to develop a coking rate prediction model for RP-3 aviation fuel. A computational model is established to characterize the evolution of coke deposit thickness along the channel in heat exchange units. The impact of fuel coking on flow and heat transfer characteristics is revealed, and the heat exchanger performance and coking behavior under various operating conditions is analyzed. Measures to reduce the coking rate are proposed. The results show that after 10 hours of operation, wall coking increases thermal resistance on the fuel side by approximately 3.7%. When mass flow rate increases from 0.03 kg·s⁻¹ to 0.05 kg·s⁻¹, the total coke deposition decreases by 27.8%. 
  
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  Molecular Dynamics Simulation of the scCO₂ Nanochannel Enhanced Oil Recovery Process

  GUO Xianglin, YANG Wenzhe1, 2 TAO Junyu1, 2 CAO Jingheng, LI Xiaoyin, XIA Xiaoyu, WANG Lei, WANG Zhiguo, JIANG Lanlan, LIU Yu, SONG Yongchen

  Journal of Engineering Thermophysics. 2026, 47(2): 625-631.

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  This paper studies the microscopic mechanism of supercritical carbon dioxide (scCO₂) displacing decane in nanopores by using molecular dynamics simulation methods. By constructing quartz nanopores, the displacement behavior of scCO₂, the transport characteristics of decane, and the influence of injection pressure were analyzed. The results show that within the injection pressure range of 55 to 65 MPa, CO₂ and decane become miscible, effectively stripping decane molecules from the pore walls, with a maximum recovery rate of over 99%. As the injection pressure increases, the decane diffusion coefficient during the displacement stage increases from 1.37×10⁻⁸ m²/s to 2.77×10⁻⁸ m²/s, significantly reducing the displacement time by 42%, while the diffusion coefficient in the initial stage remains relatively stable. The diffusion of decane causes a backward flow phenomenon, and the higher the injection pressure, the more significant the backward flow, increasing from 4.4% to 6.7%. The research indicates that scCO₂ has a high efficiency in displacing decane, and appropriately increasing the injection pressure can accelerate the displacement process, but excessively high pressure will lead to an intensified backward flow.
  
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  Experimental Study on Photothermal Conversion and Thermal Energy Storage Performance of Reversible Thermochromic Composite Phase Change Materials

  YANG Peng, ZHANG Chaocheng, HUANG Kun, ZHANG Guangtong, LIU Chenzhen, RAO Zhonghao

  Journal of Engineering Thermophysics. 2026, 47(2): 632-644.

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  This study prepared thermochromic composite phase change materials (RT-CPCMs) using 7-anilino-3-diethylamino-6-methylfluoran (ODB-1) as the color former, 2,2-bis (4-hydroxyphenyl) propane (BPA) as the color developer, and docosanol as the solvent. The effects of different material ratios on the phase change temperature, latent heat of phase change, optical properties, thermal conductivity, and stability of RT-CPCMs were systematically investigated. Results revealed that RT-CPCMs exhibited a temperature-dependent color transition characteristic of “black → dark gray →colorless transparent” with increasing temperature. In the visible light region, RT-CPCMs demonstrated broad spectral absorption capacity. The phase change enthalpy of RT-CPCMs increased with the mass fraction of docosanol, exceeding 204.57 J/g. Compared to pure docosanol, the photothermal conversion efficiencies of C14, C24, and C34 in RT-CPCMs were enhanced by 104%, 126%, and 154%, respectively. After 500 thermal cycles, the phase change enthalpy decay rates of these samples were 1.02%, 1.03%, and 0.70%, indicating excellent thermal stability.
  
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  Experimental Study on Dynamic Response of R134a Flow Boiling Heat Transfer in Multiple Microchannels Heat Sinks

  MA Xiang, HU Chengyu, YANG Xiaoping, ZHANG Yonghai, WEI Jinjia

  Journal of Engineering Thermophysics. 2026, 47(2): 645-652.

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  This paper conducts an in-depth study on the dynamic characteristics of boiling heat transfer of multiple microchannels heat sinks under multi-heat source scenarios. Using R134a as the working fluid, the multiple microchannels heat sink system under different mass fluxes was tested. The heat sink contains 41 microchannels with a hydraulic diameter of 0.55 mm. The steadystate and transient characteristics of boiling heat transfer of the multiple microchannels heat sinks were explored and compared with the single microchannel heat sink. The results show that the boiling heat transfer coefficient curve of the multiple microchannels heat sink is similar to that of the single microchannel heat sink. Due to the differentiated heat input, the flow rate and pressure drop in the multiple microchannels vary dynamically, resulting in a decrease in the maximum heat flux of the multiple microchannels by up to 30%, and a flow non-uniformity of up to 63%. The greater the power density, the greater the degree of flow non-uniformity. The research results have important reference significance for the efficient and stable operation of multi-heat source electronic devices.
  
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  Numerical Simulation of Heat Transfer Characteristics of Liquid Droplet on a Superheated Surface

  ZHANG Jinyang, XIONG Ping, JIANG Qifeng, ZHOU Linglan, YANG Shihao, ZHANG Shuyue

  Journal of Engineering Thermophysics. 2026, 47(2): 653-660.

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  In order to study the heat and mass transfer of water droplet impacting on a superheated surface, the mechanism of impact velocity and surface temperature on the heat transfer characteristics of droplet is analyzed based on the Volume of Fluid (VOF) method and evaporation model. The results show that increasing the droplet impact velocity can enhance the heat transfer effect, and the average heat flux and average pressure at the bottom surface are showing proportional growth with impact velocity. In addition, elevated surface temperature induces a transition in boiling regimes from nucleate boiling to film boiling, and the distribution of heat flux at the bottom surface shows that the heat flux is large in the edge region and small in the center region, which indicates that the center region at the bottom has more vapor convergence, and the existence of the vapor layer greatly influences the heat transfer efficiency.
  
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  Numerical Study on Combustion and NO_x Formation Characteristics of Hydrogen-air Flame in a Coaxial Dual Swirl Burner

  LAI Zhengxin, SONG Wenyan, WANG Qiuyin, WANG Sen

  Journal of Engineering Thermophysics. 2026, 47(2): 661-675.

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  A numerical study of swirling hydrogen flame structure, chemical reaction and nitrogen oxides formation characteristics in HYLON coaxial dual swirl burner is presented. Turbulent combustion modeling is performed by using finite-rate chemistry transport approach and flamelet tabulation approach, in combination with detailed chemical kinetic scheme for H₂ oxidation. The results indicate that the global flame structure is determined by swirl jets and flow recirculation as the hydrogen flame takes a M-shape reaction layer consisting of two distinct flame branches with different chemical characteristic and stabilization regime. The shear reaction layer evolves in a relatively high velocity region between hydrogen and air streams with vigorous combustion processes. Whereas the central reaction layer evolves in a relatively low velocity region and lies in central recirculation zone. Chemical reaction in central reaction layer is significantly weaker than that in shear reaction layer. It is found that the NO formation is strongly affected by the swirling flame structure. The thermal mechanism is found to be the dominant reaction pathway for NO formation in central reaction layer. Whereas in shear reaction layer, the effect of N₂O mechanism and NNH mechanism becomes comparable with that of thermal mechanism. The N₂O pathway and NNH pathway are found to be important for the preliminary conversion of NO in the vicinity of shear flame front.
  
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  Effect of Injection Timing and Rotating Speed on Combustion in an Ammonia/Hydrogen Rotary Engine

  LI Pengzhen, QIN Miaoxin, WANG Yiyang, FAN Baowei, PAN Jianfeng

  Journal of Engineering Thermophysics. 2026, 47(2): 676-683.

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  Ammonia/hydrogen blending fuel engine is one of the effective solutions to realize carbon-zero emission of internal combustion engine. In this paper, an accurate three-dimensional model of rotary engine is established for the in-cylinder working process of ammonia/hydrogen blending fuel rotary engine and experimental validation is carried out. On this basis, the effects of injection timing and rotating speed on engine combustion and emission are analyzed. The results show that with the ammonia/hydrogen fuel injection timing from 470 °CA before the top dead center to 390 °CA before the top dead center, the mean pressure in-cylinder firstly increases and then decreases, and the hysteresis period and combustion duration firstly shortens and then lengthens, and the peak in-cylinder pressure is the highest when the injection timing is 430 °CA before the top dead center, which is 1.47 MPa, the hysteresis period is the shortest, which is 5.72 °CA, and the combustion duration is 58.85 °CA. Further, as the rotating speed increases from 600 r/min to 3000 r/min, the peak pressure first increases and then decreases, and the peak pressure reaches the highest at 1800 r/min, which is 1.53 MPa. For the ammonia/hydrogen blending fuel rotary engine, the power performance and economic performance in the range of rotating speeds from 1500 r/min to 1800 r/min are significantly improved.
  
  
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  A Study on Bio-fuel Production by Organic Solvothermal Catalytic Liquefaction

  LIU Yu, WANG Haocheng, LUO Chuanhai, SUN Hongyu, YE Jinghao, YAN Mi

  Journal of Engineering Thermophysics. 2026, 47(2): 684-689.

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  Organic solvothermal liquefaction can directly convert kitchen waste into bio-oil without pre-drying. This study examined the effects of Fe-Ni bimetallic catalysts with varying Fe loading on the distribution of liquefaction products derived from kitchen waste, as well as the nitrogen and sulfur balance and the upgrading of bio-oil. The results indicate that the introduction of a Fe-Ni bimetallic catalyst is beneficial to the hydrodeoxygenation and denitrification processes of bio-oil. Under the catalysis of 6Fe-10Ni/Al₂O₃, a bio-oil yield of 53.10%, hydrocarbon content of 13.52%, and ester content of 60.86% were achieved.
  
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  Non-premixed Combustion Experiment of Biomass Gasification Gas and Natural Gas

  FANG Haodong, ZHANG Han, ZHANG Xiong, FAN Zewei, LUO Zixue, ZHANG Shihong

  Journal of Engineering Thermophysics. 2026, 47(2): 690-697.

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  Biomass gasification gas is gradually being widely applied in traditional industries as a substitute for fossil energy. However, existing burners cannot meet the requirements for co-firing biomass gasification gas with natural gas. This paper proposes a non-premixed burner for co-firing biomass gasification gas and natural gas. The effects of different burner loads (P), excess air coefficients (α), and biomass gasification gas blending ratios on flame structure, pollutant emission performance, and flame lift distance of the burner were investigated. The results show that the optimal α and mixing ratio are 1.4 and 40%, respectively. The NO emission concentration is 12.7 mg/m³, and the flame lift distance is reduced from 22.5 mm to 4.1 mm compared to pure natural gas combustion.
  
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  Lateral Flame Spread Over Thermally Thin Material Under Forced Flow and Sub-atmospheric Pressures

  LI Zhonghua, MA Yuxuan, HU Longhua

  Journal of Engineering Thermophysics. 2026, 47(2): 698-705.

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  Experiments were carried out in a combustion wind tunnel to investigate the lateral flame spread behavior of thermally thin material under forced flow and low pressures. The flame spread rate and gas-phase thermal length were measured, with flow speed ranging from 0 cm/s to 50 cm/s and ambient pressure ranging from 50 kPa to 100 kPa. The results show that the flame spread rate initially increases and then decreases with increasing flow speed (at 80∼100 kPa) or remains unchanged (at 50∼70 kPa), while it increases monotonically with pressure. Furthermore, a convective heat transfer coefficient coupling natural and forced convection was proposed. The flame convective heat flux and the ratio of upper and lower surface heat fluxes were calculated utilizing the experimental data, showing good agreement with experimental results. The dominant role of lower surface flame heat flux in lateral flame spread over thermal thin material was revealed. 
  
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  Experimental Study on Reducing CO/NOx by Adjusting Quartz Sand Bed Material With Porous Alumina Ball During Smoldering Process of High-Moisture Sludge

  MA Lun, QIAO Yu, HUANG Jingchun, ZHANG Cheng

  Journal of Engineering Thermophysics. 2026, 47(2): 706-712.

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  The sludge smoldering technology is a novel disposal method for the high-moisture and low-calorific value sludge. However, the relatively high CO and NO_x concentrations in the smoldering flue gas increase the flue gas purification cost. This work proposes to regulate traditional quartz sand bed material by using porous alumina balls, CO oxidation and NO_x reduction are promoted through the porous confinement effect of alumina ball. The studied results show that the smoldering propagation velocity and the reaction temperature gradually decrease as the proportion of porous alumina balls in the bed material medium increases from 0% to 15%, and significantly decrease as further increasing to 20%. When the proportion of porous alumina balls is controlled within 15%, the unburnout content in the smoldering ash can be maintained within 5%. Owning to the porous confinement effect, porous alumina ball can significantly reduce the concentrations of CO and NO_x in smoldering flue gas. Comprehensively considering, it is recommended that the proportion of porous alumina balls should not exceed 15%, which not only can maintain excellent smoldering reaction characteristics and reduce carbon content in the residual, but also can significantly reduce the CO/NO_x concentration in flue gas.
  
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  Investigation of Swirling Spray Flame Synthesis of Yttrium-Magnesium Composite Nanopowders and Fabrication of Infrared Transparent Ceramics

  LEI Shuting, ZHANG Yiyang, FANG Zhu, JIN Xing, LI Shuiqing

  Journal of Engineering Thermophysics. 2026, 47(2): 713-721.

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  Y₂O₃-MgO composite ceramics are promising candidates for the next-generation infrared transmittance window materials due to their ability to maintain low infrared emissivity and exhibit excellent optical and mechanical properties at high temperatures. In this paper, we investigate the process of swirling spray flame synthesis of Y₂O₃-MgO nanoparticles, demonstrating that cubicphase Y₂O₃-MgO nanoparticles with a narrow particle size distribution and homogeneous mixing can be successfully synthesized by adding equivalent 2-ethylhexanoic acid (EHA) and adjusting the precursor concentration. The solid solubility limit of MgO in Y₂O₃ is further explored, showing that spray flame synthesis can extend MgO solubility in Y₂O₃ to 70%(mol), which is 10 times higher than that of the conventional phase diagram (≈7%). Finally, infrared transparent ceramics with a transmittance as high as 83.8% were fabricated using solid solution nanoparticles with uniform particle size by spray flame synthesis.
  
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  Research on Ignition Performance of Premixed Staged Low Emission Combustor

  ZHANG Shanjun, ZHENG Longxi, REN Tongtong, MA Hongyu

  Journal of Engineering Thermophysics. 2026, 47(2): 722-729.

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  An experimental study was conducted on a can combustor under ambient temperature and pressure condition to investigate the influence of combustor inlet air velocity, igniter position and ratio of pilot fuel on lean and rich ignition performance of premixed staged low emission combustor for aero-engines and gas turbine, and the reason was investigated by CFD numerical simulation. The experimental results show that with increment of combustor inlet air velocity, combustor equivalence ratio of lean ignition increases, and change trend of lean ignition performance on different igniter position keeps the same, but that of rich ignition performance is different. With increment of distance of igniter to liner dome, change trend of lean and rich ignition performance is different under the condition of different inlet air velocity. The influence of igniter position on combustor lean and rich ignition performance is little at low inlet air velocity. With increment of distance of igniter, the scope of equivalence ratio of lean and rich ignition decreases at high inlet air velocity. With increment of ratio of pilot fuel, combustor equivalence ratio of lean ignition decreases at low inlet air velocity, the influence weakens little by little. The influence of ratio of pilot fuel on combustor lean ignition performance is very little at high inlet air velocity.
  
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  Study on the Effect of Ammonium Bisulfate on Fly Ash Deposition in Air Preheater

  SU Yunda, QING Mengxia, ZHOU Shengbo, LIU Liang, LI Xin’ao, XIANG Jun

  Journal of Engineering Thermophysics. 2026, 47(2): 730-739.

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  The generation and deposition of ammonium bisulfate (ABS) has been identified as a key factor contributing to the exacerbation of air preheater clogging in coal-fired power plants. This issue compromises the safe and economical operation of these facilities and has significant environmental implications. The present study aims to investigate the impact of various parameters on fly ash deposition, focusing on the role of ABS deposition amount (ash-sulfur ratio), temperature, and the composition of fly ash. The findings indicate that molten ABS within the fly ash increases with a decrease in the ash-sulfur ratio, leading to an escalation in fly ash deposition grades. Furthermore, an increase in temperature from 175◦C to 270◦C results in a substantial enhancement of fly ash deposition grades, particularly at an ABS deposition ratio of 55%. The preferential reaction order of fly ash components with ABS was SrO > CaO > MgO > K₂O > Na₂O > Fe₂O₃ > Al₂O₃, and the fly ash deposition was effectively alleviated when the mass fractions of CaO, MgO, and Na₂O in the fly ash were increased to 15%, 4%, and 4%, respectively.