27 December 2024, Volume 46 Issue 1

    

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  Management Review of Engineering Thermophysics and Energy Utilization Discipline of National Natural Science Foundation of China in 2024#br#

  GUAN Yonggang, ZHOU Tian, WANG Hui, FAN Aoran, WANG Lei

  Journal of Engineering Thermophysics. 2025, 46(1): 1-7.

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  The application, screening, evaluation and funding of National Natural Science Foundation of China programs in Engineering Thermophysics and Energy Utilization Discipline in 2024 are summarized and statistically analyzed. The strategic research, funding proposals in the field of energy and power under the carbon peaking and carbon neutrality goals are introduced. The outstanding achievements funded by the discipline in 2024 and future work in 2025 are introduced as well.
  
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  Chemical Reinjection Gas Turbine Cycle System and Thermodynamic Performance Analysis

  HUANG Yupeng, SU Bosheng, WANG Yilin, HUANG Zhi, YUAN Shuo, HUANG Qiteng

  Journal of Engineering Thermophysics. 2025, 46(1): 8-19.

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  Aiming at the problems of low power generation efficiency and water high consumption in the chemical recuperated gas turbine cycle, a chemical reinjection gas turbine cycle is proposed in this study. It is proposed that part of the flue gas in the gas turbine was put back into the reactor, the reaction of methane self-reforming reaction, and realize the efficient transformation of methane conversion rate. The technology features fully realize the effect of improving the quality of gas turbine flue gas waste heat, and improving the circulation work. Through the improvement of the fuel energy conversion process and the optimization of the heat transfer process of the system, the power generation efficiency of the new system is increased by 9.12% compared with that of the chemical heat recovery system at the design point, the performance of the power generation of lower pressure ratio and high gas turbine inlet temperature is better. The economic analysis shows that the economic payback period of the system is 2.3 years, which has good economic benefits. 
  
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  Dynamic Modeling and Uncertainty Analysis of District Heating System

  LIN Xiaojie, MAO Yihui, ZHONG Wei

  Journal of Engineering Thermophysics. 2025, 46(1): 20-26.

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  District heating system is one of the important carriers for coordinating renewable energy and traditional energy and realizing flexible consumption of renewable energy. Considering the impact of the uncertainty of renewable energy output and user cluster heat load on the dynamic transportation process of district heating network, it is necessary to quantitatively analyze the uncertain variables on both sides of the source and load and the dynamic characteristics of the heating network. This paper first established a dynamic transportation model of the heating network to solve its heat loss and transmission delay characteristics. Secondly, the Gram-Chalier A algorithm was applied to calculate the probability distribution semi-analytical expression of the thermal power of the source and load nodes of the system, and Bayesian credible inference method was used to calculate the fluctuation interval of node thermal power. This paper selected a secondary heating network in Beijing for model accuracy validation and case analysis. The system has 90 nodes and 109 pipes. The results show that the proposed model and algorithm can effectively quantify the fluctuation interval of nodes’ thermal power.
  
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  Analytical Model in Porous Medium for Coupling Mechanism of Heat Transfer Process Analysis in Quick Freezer

  YANG Yong, CHEN Baojun, LI Guangfu, ZHANG Shuai, LIU Jintian, LI Wenfei, KONG Shining, ZHANG Zhao, LIU Hong, SHEN Shengqiang

  Journal of Engineering Thermophysics. 2025, 46(1): 27-34.

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  Entransy analytical model of heat transfer process in stacked porous medium is built, and a new utilization efficiency of Entransy is proposed, meanwhile wave function and field function characteristics of Entransy are found. Based on the model, coupling the cooling curve, surface temperature of cooling products in porous medium, internal temperature gradient, convective heat transfer coefficient along quick freezer, entransy dissipation rate during cooling process are predicted for the first time. Mesoscale characteristics of coupled heat transfer for conduction, convection and radiation in heat transfer process in porous medium have been found. Results show that, volume scale of internal heat transfer core and temperature gradient control heat flux and convective heat transfer coefficient on surface, and wavy characteristics of internal temperature difference decreasing rate affect tendency of heat flux convective heat transfer coefficient. Temperature change trend can be predicted accurately based on along heat transfer coefficient. Porous medium can enhance heat transfer, and scaling factor of heat transfer coefficient without and within porous medium is about 0.6, meanwhile radiation and convection have field synergy characteristics.
  
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  Design and Analysis of Parabolic Trough Solar Concentration and Nano-fluid Beam Splitting PVT System

  WANG Gang, ZHANG Zhen, JIANG Tieliu

  Journal of Engineering Thermophysics. 2025, 46(1): 35-41.

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  In this paper, a new solar photovoltaic/thermal system with parabolic trough concentrator and indium tin oxide/ethylene glycol nano-fluid beam splitting is proposed. Indium tin oxide/ethylene glycol nano-fluid is prepared and tested. The results show that the absorptivity and transmittance of the indium tin oxide nano-fluid are 30.9% and 69.1% in the full wavelength range. The optical behavior of the photovoltaic/thermal system is studied and the overall optical efficiency of the system is 89.38%. When the sun tracking error is less than 0.2 ̊, the photovoltaic/thermal system can have an overall optical efficiency which is greater than 84.14%. The operation performance analysis reveal that the photoelectric efficiency of the photovoltaic subsystem is 29.1%, and the overall photoelectric conversion and thermal efficiencies of the photovoltaic/thermal system are 19.1% and 19%. The thermal efficiency of the system can be improved by increasing the inlet indium tin oxide nano-fluid velocity, or by reducing the inlet indium tin oxide nano-fluid temperature and external convectional heat transfer coefficient.
  
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  Thermodynamic Analysis on the Afterburning-type Compressed Air Energy Storage System Integrated With Molten Salt Thermal Storage

  ZHAO Chaocheng, LIU Ming, NI Guangtao, YAN Junjie

  Journal of Engineering Thermophysics. 2025, 46(1): 42-50.

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  Energy storage is the key technique to establish the new-type power system and achieve the dual carbon goal, and the compressed air energy storage is a highly promising option for largescale long-term energy storage. In this study, an afterburning-type compressed air energy storage system integrated with molten salt thermal storage was proposed, and thermodynamic models of the proposed system were developed. Then, influences of key parameters on system performance under different power loads were evaluated. The analysis results show that the four operation modes of the system can meet four power load demands, i.e., the high power load demand, the medium-high power load demand, the medium-low power load demand, and the low power load demand. Among them, the output power corresponding to high power load demand is 1573.93 kW, and the output power corresponding to low power load demand is 350.15 kW. The roundtrip efficiency of operation mode with low power load is the highest of 69.87%.
  
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  Tracer Characteristic Analysis of Nitrogen Droplets Spontaneously Condensed in a Cryogenic Wind Tunnel

  HOU Jiaxin, GAO Rong, ZHANG Wei, XIE Junlong, ZHANG Xiaoqing, CHEN Jianye

  Journal of Engineering Thermophysics. 2025, 46(1): 51-56.

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  Application of non-intrusive measurement technique in transonic cryogenic wind tunnels is confined to the lack of suitable tracer particles. The present study explored the feasibility of utilizing spontaneous condensing nitrogen droplets as tracer particles. A numerical model of nitrogen non-equilibrium condensation was established. The non-equilibrium condensation process of nitrogen droplets was investigated. Further, droplet tracer characteristic was carried out by combining Stokes number, response time, and droplet evaporation rate. The results showed that spontaneous condensing nitrogen droplets can be controlled in quantities and size and can show good tracer ability. This paper offers a novel and viable approach to addressing the lack of tracer particles in cryogenic wind tunnels and establishes a theoretical framework for optimizing the tracer characteristic of liquid nitrogen droplets.
  
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  Optimization of Air-side Friction and Heat Transfer Performance of Micro-bare-tube Heat Exchangers With Bundle Diameters Varying Gradually

  GONG Zhenguo, ZHOU Wenjie, CAI Bowen, WANG Xin

  Journal of Engineering Thermophysics. 2025, 46(1): 57-67.

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  In this paper, a finless micro-bare-tube heat exchanger with tube bundle diameter varying gradually in the range of 0.4 ∼ 1.0 mm is proposed. The air-side friction and heat transfer performance of micro-bare-tube heat exchangers with bundle diameters varying gradually were studied by CFD simulation. By using the relevant empirical formula and NSGA-II algorithm, the multiobjective optimization of the dynamic friction factor f and heat transfer performance factor j was carried out, and the optimal structural parameters of the micro-bare-tube heat exchanger with varied pipe diameter were determined. When the longitudinal tube wall spacing is 0.214 mm, the transverse tube wall spacing is 1.127 mm, and the tube bundle diameter is 0.876 mm, 0.746 mm, 0.697 mm and 0.550 mm from outside to inside, the heat transfer performance factor j reaches the maximum value of 0.04169, and the flow friction factor f reaches the minimum value of 0.01270. Compared with the equal-diameter finless micro-bare-tube heat exchanger, the new structure not only reduces the pressure drop, improves the heat transfer efficiency, but also saves the amount of metal manufacturing materials and refrigerant charge.
  
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  An Adaptive CO₂ Heat Pump Across Full Operating Conditions for Space Heating

  HE Yujia, SHAO Liangliang, CAO Xiang, ZHANG Chunlu

  Journal of Engineering Thermophysics. 2025, 46(1): 68-71.

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  CO₂ heat pumps demonstrate excellent low-temperature heating capability and environmental friendliness. However, a single-mode CO₂ heat pump faces challenges in adapting to diverse operating conditions in space heating. To address this issue, this paper proposes a self-adaptive CO₂ heat pump capable of operating under all conditions, focusing on the following two aspects. The first involves cycle integration, enabling the system to switch between a mechanically-subcooled transcritical CO₂ cycle and a superheat-recovered cascade cycle. Next is the heat exchange matching. By splitting and rearranging the heat exchangers, the system achieves multi-stage heating to enhance the uniformity of the temperature field. Through simulations, adaptive switching strategies are established for variable operating conditions, providing guidance for practical operation. Finally, the overall seasonal efficiency of the new system is shown to improve by 1.9% to 17.7% compared to the existing system.
  
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  The Investigation of Unsteady Flow Mechanism in a Transonic Axial Compressor

  LANG Jinhua, KANG Jiacheng, AN Guangyao, ZHANG Lei

  Journal of Engineering Thermophysics. 2025, 46(1): 72-82.

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  In order to investigate the unsteady flow mechanism in the tip region of the axial compressor, a numerical simulation study was carried out to investigate the unsteady evolutionary characteristics of the tip leakage flow field. It was discovered that the dominant frequency of the unsteady flow at the blade tip region was 1863.3 Hz, and the tip leakage vortex formed at the leading edge of the suction surface broke down in one oscillation phase and formed a new vortex structure. Due to the combined effect of the differential pressure between the suction surface and the pressure surface and the leading edge excitation shock wave, the vortex structure gradually moved to the leading edge of the adjacent blades, and during this cross-cycle evolution, the vortex structure appeared to be maintained for about 1/9th of a cycle. In the subsequent cycle, the vortex structure formed by the tip leakage vortex breakdown dissipated while interacting with the broken vortex to form a blockage region in the passage. Along with the influence of the excitation shock wave, this blockage region exacerbated the generation of the “leading edge overflow”phenomenon. It was also hypothesized that the tip leakage vortex breakdown due to vortex wave interference was the key factor in the flow unsteadiness. After the tip leakage vortex broke down, a new vortex structure was formed at the leading edge of the adjacent blade, and a series of evolutionary processes occurred over time, which was the main cause of the unsteady flow in the blade tip region. 
  
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  Optimal Design of Proton Exchange Membrane Fuel Cell Ejector

  ZHANG Dibo, SHI Liuliu, ZHANG Wenjie

  Journal of Engineering Thermophysics. 2025, 46(1): 83-91.

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  The performance of the PEMFC ejector is influenced by the dimensions of the structure, and there are serious deviations from the design points in the solutions obtained according to the mainstream design methods. Firstly, the initial design of the ejector is based on Соколов’s method and the parameters to be optimised are determined. Secondly, the initial sample points are selected in the design space using the LHS and the response values of the sample points are obtained by CFD. Subsequently, the radial basis function surrogate model is constructed and hyper-parameter tuning is performed to improve the model performance. Then the current surrogate model is optimised by the particle swarm optimisation algorithm to obtain the possible optimal solution of the original optimisation problem. In the optimization process, the internal sample points are gradually added and the surrogate model is updated to improve the approximation accuracy of the surrogate model in the vicinity of the global optimal solution. Finally, a sensitivity analysis is performed on the optimization parameters. The results show that the performance of the ejector at the optimal design point is improved by 22.5%, the nozzle outlet diameter, mixing chamber inlet diameter and the distance between the nozzle and the mixing chamber inlet have a significant impact on the performance of the ejector.
  
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  Research on Wind Turbine Blade Damage Detection Based on Image Recognition Technology

  XING Yi, SONG Li, LIU Bo, CHEN Yongyan, JIAO Xiaofeng, FENG Boyu

  Journal of Engineering Thermophysics. 2025, 46(1): 92-97.

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  The wind turbine is affected by the harsh environment, and the blade surface is prone to damage. Aiming at the problems of small damage size and variable shape and style, this paper proposes a lightweight wind turbine blade surface damage detection algorithm based on improved YOLOv5. According to the characteristics that the basic network is sensitive to the deviation of small target position detection, the two loss measurement methods of NWD and IOU are combined. At the same time, in order to reduce network complexity and improve network performance, multidimensional dynamic convolution ODConv is integrated into the YOLOv5 model backbone network. The experimental results show that the computational complexity of the improved network is reduced by 45%, and the average accuracy of the algorithm is improved by 8.3%, which can better identify the surface damage of wind turbine blades.
  
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  Experimental Study on the Effect of Air Conditioner External Pipeline on Compressor Vibration

  ZHANG Hongtao, WU Junhong, PAN Xi, XIE Junlong

  Journal of Engineering Thermophysics. 2025, 46(1): 98-103.

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  The compressor is the core component of an air conditioner, and its vibration characteristics play a key role in improving the reliability of the compressor. In order to clarify the effect of the fixing method of air conditioner external pipeline on the compressor’s vibration characteristics, this paper carried out some experimental research on it. Two variable factors, including the location of the constraints and the number of constraints on the air conditioner external pipeline, were taken into account; the vibration acceleration in different directions at each test point of the compressor was recorded during the test at an operating frequency of 30 Hz∼90 Hz. The results of the test show that a moderate increase in the distance between the restraining position and the outdoor unit can lead to a better realization of compressor vibration reduction; Increasing the number of constraints achieves little vibration reduction in the axial direction at the compressor position, but will increases the radial vibration acceleration at the motor position considerably.
  
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  Total Three-dimensional Analysis of Mixing Loss due to Film Cooling in the Suction Surface of Turbine Guide Vane

  WANG Chenfeng, LI Guoqing, BAI Xiaohui, LI Nianqiang, ZHANG Yanfeng, LU Xingen

  Journal of Engineering Thermophysics. 2025, 46(1): 104-113.

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  A total three-dimensional method for calculating mixing loss is proposed in response to the problem that existing methods for evaluating the mixing loss of film cooling cannot accurately calculate the loss between mainstream and coolant in the area affected by passage secondary flow. Film holes with different compound angles are set in the suction surface based on HS1A turbine guide vane. Under the premise of meeting the requirements from film cooling effectiveness, the loss mechanism is analyzed by controlling the mainstream and coolant parameters. Different models are analyzed by using the entropy creation of mixing as the basis for loss evaluation. The results show that film cooling effectiveness is improved by arranging subregional compound angle holes with entropy creation of mixing increasing. And the loss of film deflection caused by passage secondary flow and film detachment can be reduced by setting compound angles.
  
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  Investigation on Operation Characteristics of Rotating Detonation Engine With Cavity

  ZHOU Jianping, SONG Feilong, WU Yun, GUO Shanguang, KANG Jinhui, CHEN Qi

  Journal of Engineering Thermophysics. 2025, 46(1): 114-119.

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  The effect of convergent nozzle on the operation characteristics of rotating detonation engine with cavity is investigated. The cross-correlation algorithm is applied to identify the propagation mode of detonation wave, and the stability parameters of detonation wave propagation are defined according to the loop delay of the auto-correlation. The total pressure at the combustor outlet is calculated by the average static pressure and Mach number, and then the total pressure recovery coefficient is obtained. With the decrease of nozzle outlet area, the lower boundary of detonable equivalent ratio will decrease. The stability of detonation wave propagation is less affected by the nozzle. The reduction of the nozzle outlet area is beneficial to increasing the velocity of detonation wave and the total pressure recovery coefficient of rotating detonation engine.
  
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  Effect of Rocket Thrust Chamber Gas Film Holes on Cooling Characteristics

  YU Ningning, WANG Zhongwei, ZHANG Hai

  Journal of Engineering Thermophysics. 2025, 46(1): 120-126.

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  The effect of adjusting the air film holes on the cooling characteristics of a particular type of rocket thrust chamber is analyzed with a numerical simulation method. The cooling effect is compared under fixed blowing volume conditions, and the effects of changing the outlet diameter (b/S = 0.446, 0.594, 0.743), the outlet angle (β=30°, 40°, and 60°), and the number of holes (Ni=200, 300, 400) are investigated with respect to the state of the jet flow and the cooling effect. The findings demonstrate that variations in the quantity of gas film holes and outlet structural characteristics affect both the jet flow condition and the regularity of the gas film. To a certain extent, modifications can be made to enhance the cooling effect based on the benchmark hole structure.
  
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  A Research Based on a Scheme of Ring Calibration of Seven-hole Probe and an Interpolant Method Using Neural Network

  XIN Jianchi, WU Huayin, LU Huawei, TIAN Zhitao, LIU Jun

  Journal of Engineering Thermophysics. 2025, 46(1): 127-137.

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  In this thesis, a calibration test method of circular distribution of measuring points is adopted, and the calibration data are obtained by experiments in subsonic wind tunnel. On the basis of the existing seven-hole probe calibration and interpolation research, a neural network fitting and interpolation method is developed and the whale optimization algorithm is used to optimize the hyperparameter. The optimized neural network interpolation method is compared with the traditional polynomial interpolation and linear interpolation methods. The results show that the calibration test method of circular distribution of measuring points can simplify the calibration test of seven-hole probe and obtain reliable calibration data. The angle error of polynomial interpolation is higher than 0.5°, the angle error of linear interpolation is less than 0.3°, and the interpolation accuracy of unoptimized neural network is lower, and the angle error of some points exceeds 1°. Comparatively speaking, the optimized neural network interpolation algorithm has more advantages: the interpolation accuracy is the highest, and the angle error is within 0.2°. The Mach number error is within 0.8%, and the total pressure error is within 1.08%.
  
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  Investion of Flow Heat Transfer Characteristics in a Rotating Labyrinth Seal

  YANG Shaoyun, LUO Lei, DU Wei, WANG Songtao

  Journal of Engineering Thermophysics. 2025, 46(1): 138-143.

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  The straight-through labyrinth seal is an effective and simple sealing technology which is widely used in gas turbines. In this paper, the effect of rotation on the flow heat transfer in a straight-through labyrinth sealing structure is investigated using numerical simulations. All results are obtained at Reynolds numbers of 6000, 10000 and 15000. The results show that the increase in rotational speed reduces the vortex losses and throttling losses in the labyrinth seal channel, which leads to the increase in the discharge coefficient. With the increase of rotational speed, the heat transfer at the tip wall is enhanced while the heat transfer at the tooth cavity is weakened.
  
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  Study on the Wall-Approaching Film Formation Characteristics of Water Injection in a Single-Screw Steam Compressor

  DAI Zeyu, WANG Zengli

  Journal of Engineering Thermophysics. 2025, 46(1): 144-150.

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  To realize reasonable control of the water injection parameters for a single-screw steam compressor, a three-dimensional single screw groove model was established, the numerical simulation of the wall-approaching film formation process of injected water along the wet compression process was carried out, the coverage area of the effective water film formed by the injected cooling water inside the compression channel, as well as the influence laws of the key parameters such as water injection mass flow rate, velocity, angle, and screw rotor rotational speed were analyzed. The results indicate that the injection mass flow rate has the greatest impact on the coverage area of the effective water film with a maximum increase of 6.77×10⁻⁴ m². Within the selected parameter range in the study, the respective increases in the coverage area of the effective water film caused by these factors are 59.85%、50.68% and 47.79% compared to the increase caused by the injection mass flow rate. 
  
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  Effect of Divider Structure on Boiling Heat Transfer Performance of Manifold Microchannels

  WANG Jin, ZHANG Borui, HE Yurong

  Journal of Engineering Thermophysics. 2025, 46(1): 151-157.

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  Manifold microchannels have lower pressure drop and higher heat transfer efficiencies than traditional microchannels, and combining the manifold microchannel heat transfer method with the boiling heat transfer method will further enhance the heat transfer performance of the device. In this study, high thermal conductivity diamond was used as the microchannel substrate, and computational fluid dynamics was utilized to investigate how the flow and boiling heat transfer performance of the device is affected by the outlet/inlet width ratio of the manifold microchannel and the ratio of the manifold size to the total size of the microchannel. The findings indicate that the device’s integrated heat transfer performance will be enhanced by a manifold microchannel outlet/inlet ratio larger than 1; the greater outlet/inlet ratio, the easier the bubbles in the microchannels break up and detach, and the better heat transfer performance.
  
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  The Investigation of RM Instability of Particles Driven by a Perturbed Shock Wave

  LI Linfei, JIN Tai, ZOU Liyong, LUO Kun, FAN Jianren

  Journal of Engineering Thermophysics. 2025, 46(1): 158-163.

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  The Richtmyer-Meshkov instability of perturbed shock waves, generated by a planar shock wave passing around a cylinder, interacting with N₂/SF₆ light and heavy gas interfaces has been numerically investigated, from which the effect of particles with different sizes in SF₆ on the development of RM instability is explored. The results indicate that, for particles of all three different sizes (5 μm, 20 μm, and 50 μm), the time and location of the interaction between the reflected shock wave and the light/heavy gas interface vary. The interface evolution of the 50 μm particles is more fully-developed, with a higher degree of turbulence in the late stage. Comparing the development of vortex structures formed by the interaction of the reflected shock wave and the interface, numerous spikes and bubble structures are formed in SF₆ gas. The legs of the spike undergo KH instability, eventually transitioning into turbulence. Due to the small inertia, the 5 μm particles follow the carrier fluid motion more quickly, evolving into spike/bubble structures in the late stage. In contrast, the 50 μm particles, with greater particle inertia, manifest substantial differences in motion from the fluid, exhibiting significant differences in spatial distribution from the unstable development of the gas interface.
  
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  Study on the Migration Characteristics of Two/Three Particles in Porous Media Based on LBM-IBM-DEM

  SHEN Xiaoyou, ZHU Kangning, FO Bing, CAI Jie, XI Jianfei, GU Zhongzhu

  Journal of Engineering Thermophysics. 2025, 46(1): 164-169.

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  In this paper, in order to construct a numerical simulation model, the liquid-phase flow field is solved by the lattice Boltzmann method, in which IBM and DEM are used to describe the force, motion, collision and trajectory tracking of the fine particles in Lagrangian coordinates, and the mutual interference between the fine particles is investigated by simulating the migration of double/triple particles in the porous medium, and the results show that the migration of the fine particles in porous medium is affected by the interference of other fine particles, and the interference depends on the fluid within the medium. The results show that the migration of fine particles within a porous medium is influenced by other fine particles, which is dependent on the fluid within the medium, and that when one fine particle is clogged, the pressure distribution is readjusted to affect the migration of other fine particles, while the presence of other fine particles can facilitate or hinder the migration of fine particles within the porous medium.
  
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  Experimental Investigation on Optimization of Heat Rejection Power of Open Natural Circulation System

  LIU Feng, SUN Zhongning, MENG Zhaoming, ZHANG Jiahui, ZHANG Shengnan

  Journal of Engineering Thermophysics. 2025, 46(1): 170-176.

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  The passive containment cooling system of HPR1000 adopts an open natural circulation system to extract the residual heat generated in the accident. In order to optimize the heat rejection performance of the natural circulation system, based on a large-scale open natural circulation experimental facility, this study carried out an optimization experiment of heat rejection power under low pressure conditions, and analyzed the effects of two methods of gas injection in the ascending section and water tank precipitation level on the heat rejection power. Experimental results show that the two methods can increase the heat rejection power of the system and effectively enhance the stability of natural circulation. The gas injection in the ascending section of the loop has a significantly stronger effect on the increase of the gas content than flashing. The water tank precipitation level can make the loop state gradually tends to stabilize flashing, and the heat rejection power can be increased by about 86% compared with the prototype. Under the improved scheme of the combined use of water tank precipitation level and gas injection, the heat rejection power of the system can be increased up to 2.2 times that of the prototype.
  
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  Investigation of Drag Force on the Particle Moving Towards a Planar Wall in the Free Molecule Regime

  DING Yu, SHAN Qingru, ZHANG Kexue, WANG Jun, XIA Guodong

  Journal of Engineering Thermophysics. 2025, 46(1): 177-182.

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  In this paper, based on the method of gas kinetic theory, the formulas for the drag force of the spherical particle moving in the near-wall region are obtained in the free molecular regime respectively. The results show that there is no near-wall effect when the gas-wall reflection is specular. When the particle moves parallel to the planar wall with diffuse scatterings, the force on the particle in the direction parallel to the planar wall is the drag force and in the direction perpendicular to the planar wall is the near-wall force. At higher wall temperatures, the particle is repelled by the wall effect, while at lower wall temperatures, the particle can move towards close to the wall. When the particle moves perpendicular to the wall, the force on the near-wall particle is the resultant force of the drag force and the near-wall force.
  
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  Numerical Simulation of Flow and Mass Transfer in Removing Indoor CO₂ Using Hollow Fiber Membrane Contactor

  XU Zhiqiang, ZHANG Lizhi

  Journal of Engineering Thermophysics. 2025, 46(1): 183-192.

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  In this study, the process of CO₂ removal by a hollow fiber membrane contactor (HFMC) is investigated numerically. In the HFMC, the absorbent solution (potassium lysine solution) flows through the fiber bundle, while the air flows on the shell side. The hollow fiber membrane contactor consists of staggered cylindrical fiber tubes with equal longitudinal and horizontal pitches. This study investigates the flow and mass transfer process of air and absorbing liquid inside the HFMC systematically by computational fluid dynamics methodology. After experimental validation, the model is used to calculate the friction factors and Sherwood numbers for various operating conditions on the shell side. Besides, the new correlations for predicting friction factor and Sherwood number are proposed as reference to the designs of membrane modules. This work is crucial for simplifying performance evaluation and scale-up design for the membrane module. 
  
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  Research on Reconstruction of Thermal Characteristic Parameters Based on the Random Walk Method

  ZHU Zeyu, LI Jialu, ZHANG Zhixiang, GAO Baohai, REN Yatao, QI Hong

  Journal of Engineering Thermophysics. 2025, 46(1): 193-200.

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  With the continuous development of the aerospace industry, the importance of temperature control for spacecraft is becoming increasingly prominent, especially in obtaining external heat flow data during on-orbit flight. Based on the Monte Carlo random walk method, the inverse analysis of thermal characteristic parameters are investigated for a 2-D rectangular domain using the Covariance Matrix Adaptive Evolution Strategy. The inversion of wall temperature and thermal conductivity are investigated by considering various positions, quantities of temperature, and distributions of internal heat sources within the domain. Errors of 0%, 1%, and 3% are individually applied, and the average runtime is subjected to statistical analysis. The results indicate that for a computational domain with 10 measurement points, better inversion results can be achieved when known point temperatures are closer to the boundary and there are three measurement points, and the internal heat source distribution does not affect the inversion results.
  
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  Research on Thermal Rectification Method and Flexible Load Regulation in RCC-PCM Enclosure Structures

  CHEN Long, XU Guoying, HU Xuanyu, YIN Yonggao

  Journal of Engineering Thermophysics. 2025, 46(1): 201-209.

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  The thermal performance of envelope enclosure is vital for efficient HVAC systems in civil, industrial and telecom buildings. A thermal rectification method based on radiant cooling coating (RCC) and phase change material (PCM) composite enclosure structure is proposed. By using the high reflection of solar radiation and infrared emission heat dissipation on the surface of RCC, as well as the peak clipping and delay effect of PCM on heat flow, the double thermal barrier and peak load flexible adjustment are realized. Based on the self-made phase change plate, the thermal performance experiment and simulation of RCC-PCM structure were carried out. The results show that: compared to the conventional EPS structure, summer tests demonstrate RCCPCM extends peak lag by 3.3 hours, accompanied by a 56.3% reduction in the temperature differential between the inner surface and inner air. Simulations indicate that on a typical day in July, the peak flux of inner surface decreases by 60.3%, with a 62.1% average heat flux reduction during the daytime. Nighttime, 86.8% of PCM-stored heat dissipates outward, representing an approximation of the ”thermal diode” rectifying characteristic of unidirectional heat flow throughout the day. This enclosure suits comprehensive performance adjustment of insulation, heat dissipation, and peak heat  load in various outdoor environments, and has excellent energy saving and carbon reduction potential.
  
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  Biodegradable and Biocompatible MgO Nanoparticles as Antioxidants for Cryopreservation to Mitigate Oxidative and Mechanical Damage

  WANG Xiaohong, RAO Wei

  Journal of Engineering Thermophysics. 2025, 46(1): 210-216.

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  The common damages to cells during cryopreservation are ice crystal mechanical damage or oxidative stress damage caused by low temperatures. These damages are typically prevented by adding antifreeze protective agents or antioxidants, respectively. However, there is a lack of research focus on efficiently reducing these both types of damage simultaneously. In this paper, a green, safe, and biodegradable material, magnesium oxide, was used as a protective agent to inhibit cellular cryoprotection and oxidative damage. By regulating the heat and mass transfer of magnesium oxide within cells, it was confirmed that the magnesium oxide nanoparticles enhanced heat transfer and act as antioxidants from both biological and thermophysical perspective. This property could help to reduce oxidative and mechanical damage during cellular cryopreservation and enhance the effectiveness of DMSO-free cryopreservation. This work is expected to provide new ideas for the research of magnesium oxide materials in the field of cryopreservation.
  
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  Efficient Dynamic Simulation Algorithm for Thermal Systems Based on Frequency Domain Analysis

  LI Hang, TENG Runhang, ZHAO Tian, CHEN Qun

  Journal of Engineering Thermophysics. 2025, 46(1): 217-225.

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  Efficient and accurate dynamic simulation of heat exchangers is crucial for the dynamic analysis of thermal systems. However, conventional finite difference/volume methods based on temporal and spatial discretization struggle to balance the accuracy and speed of simulation, thus hindering the dynamic performance analysis of thermal systems. In this paper, we propose an efficient algorithm for dynamic simulation of thermal systems in the frequency domain. By utilizing Fourier transform, the frequency domain control equations of heat exchangers within the system are derived and decomposed into initial-disturbance components, which are then analyzed and numerically solved separately before being superimposed to obtain the system’s dynamic response. Compared to finite difference methods, the proposed algorithm achieves a reduction in computation time by approximately one order of magnitude while ensuring accuracy (deviation < 0.3 K).
  
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  Quantum Corrections to Molecular Simulations of Heat Capacities of Attached Ice Layers

  WANG Shichun, ZHOU Leping

  Journal of Engineering Thermophysics. 2025, 46(1): 226-231.

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  A molecular dynamics approach is used to simulate ice layers of different thicknesses attached to copper plates. The calculated heat capacities are quantum corrected. The results demonstrate that the heat capacities of the attached ice layers are considerably higher than that of the bulk ice within a specific range of ice thickness (H). It reaches a maximum value at H=5a (3.5715 nm), where a is the lattice constant of the ice crystals in the z direction. Adsorption and quasi-liquid layers are observed to form at the ice-copper and ice-vacuum interfaces. The peak of the radial distribution function is found to be the largest at H=5a. The self-diffusion coefficient of the ice layers is the largest at H=6a, with a notable enhancement observed at H=5a as well. The present study indicates that these factors exert a significant influence on the heat capacities of attached ice layers.
  
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  Study of Cavitation Characteristics and Optimal Design of Hydraulically Suspended Micro-pump

  HAN Jiacheng, XUE Song, ZUO Huaiyu, XING Guanying, HONG Tao, HU Run, LUO Xiaobing

  Journal of Engineering Thermophysics. 2025, 46(1): 232-238.

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  In this paper, CFD numerical simulation and orthogonal experimental design are used to study the cavitation characteristics and optimise the anti-cavitation performance of the self-developed hydrodynamic suspension micro-pump. Through numerical simulation to get the cavitation characteristic curve of the micro-pump and the cavitation flow characteristics of different cavitation number analysis, selected impeller inlet diameter, vane thickness, suction chamber diameter, volute height of the base circle of the four factors for orthogonal test optimisation, the results show that the suction chamber diameter of the comprehensive performance of the micro-pump has a more significant impact. Simulation found that the increase of suction chamber diameter can make the vertical section of the vortex area significantly reduced; experiments measured after the optimisation of the prototype head increased by 5.20%, the critical cavitation number reduced by 59.6%.
  
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  Fluid Flow and Heat Transfer Characteristics of the Plate-Fin Heat Exchanger With Serrated Pyramid Fins

  ZHANG Ling, YANG Jing, LIN Zhimin, XIONG Shuaichao, ZHANG Yongheng, WANG Liangbi

  Journal of Engineering Thermophysics. 2025, 46(1): 239-250.

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  Based on the coupling model of heat transfer, the flow and heat transfer characteristics in the channel of serrated plate-fin heat exchanger with pyramidal fins are numerically investigated. By using the dimensionless parameter Se to quantify the intensity of secondary flow, the average and local characteristics of flow and heat transfer in the channel of the plate-fin heat exchanger with serrated pyramidal fins were analyzed and compared with those of the plain fins. The influences of the fin’s structure parameters and the pyramid’s structure parameters on the channel’s flow and heat transfer characteristics is also analyzed. The results reveal that pyramidal roughness elements can effectively enhance the intensity of secondary flow in the plate fin channel, thereby enhancing the convective heat transfer capacity on the surface of the plate-fin heat exchanger. Within the range of the parameters studied, as the height of the pyramid H_p = 0.65 mm, the length of the pyramid L_p = 1.25 mm, and the width of the pyramid W_p = 0.844 mm, the serrated plate-fin heat exchanger with the pyramidal fins obtained the optimal overall heat transfer performance. The correlation between average Nusselt number Nu_m and the intensity of secondary flow Se is a power function, which shows that the secondary flow generated by the serrated pyramidal fins plays a crucial role in improving the convective heat transfer capacity of the plate-fin heat exchanger.
  
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  Numerical Study of Fuel Flow and Heat Transfer Characteristics for a Serpentine Multiport Flat Tube

  LI Yu, WANG Xiangqin, LIU Dongyang, MIN Jingchun

  Journal of Engineering Thermophysics. 2025, 46(1): 251-260.

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  The air-fuel heat exchanger used in an aero-engine has to work under the operating condition of high temperature and large temperature difference, and when the fuel flows through the heat exchanger its temperature will change significantly. In this paper, the fuel flow and heat transfer in a serpentine multiport flat tube are studied numerically, and the effects of fuel property variability, tube wall temperature and fuel entering velocity are investigated. The serpentine multiport flat tube contains 6 tube paths, and each flat tube holds 3 round holes, with the flat tubes being connected by a manifold with baffles. The results show that the distributions of the fuel flowrate, pressure drop and convective heat transfer coefficient in the three channels of each flat tube are similar, and they all increase along the direction away from the tube entrance. As compared to the constant fuel property case, the variable fuel property case yields a larger heat transfer coefficient, a higher fuel temperature, and a lower pressure drop. With increasing fuel inlet velocity, the non-uniformity of the fuel flowrate distribution becomes more obvious, whereas the influences of fuel variable properties and wall temperature on such a distribution are relatively weak.
  
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  Ballistic Thermal Transport at Sub-10 nm Laser-Induced Hot Spots in GaN Crystal

  HUANG Dezhao, SUN Qiangsheng, ZHANG Hongkai, HUANG Xiaona, XU Shen, YUE Yanan

  Journal of Engineering Thermophysics. 2025, 46(1): 261-268.

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  Gallium nitride (GaN) is a typical wide-bandgap semiconductor with a critical role in a wide range of electronic applications. Ballistic thermal transport at nanoscale hotspots will greatly reduce the performance of a device when its characteristic length reaches the nanometer scale, due to heat dissipation. In this work, we developed a tip-enhanced Raman thermometry approach to study ballistic thermal transport within the range of 10 nm in GaN, simultaneously achieving laser heating and measuring the local temperature. The Raman results showed that the temperature increase from an Au-coated tip-focused hotspot was up to two times higher (40 K) than that in a bare tip-focused region (20 K). To further investigate the possible mechanisms behind this temperature difference, we performed electromagnetic simulations to generate a highly focused heating field, and observed a highly localized optical penetration, within a range of 10 nm. The phonon mean free path (MFP) of the GaN substrate could thus be determined by comparing the numerical simulation results with the experimentally measured temperature increase which was in good agreement with the average MFP weighted by the mode-specific thermal conductivity, as calculated from first-principles simulations. Our results demonstrate that the phonon MFP of a material can be rapidly predicted through a combination of experiments and simulations, which can find wide application in the thermal management of GaN-based electronics.
  
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  Study on Heat and Mass Transfer of a New Form of Heat Recovery Air Gap Membrane Distillation

  GUO Xinrui, MA Feng, WU Jiangbo, LIU Shujun, AN Zhoujian, DU Xiaoze

  Journal of Engineering Thermophysics. 2025, 46(1): 269-275.

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  The treatment of industrial wastewater and the acquisition of fresh water resources are currently an important topic. Membrane distillation is new technology with many significant advantages such as low operation temperature, normal pressure operation, and high water quality. In this paper, a numerical simulation of direct contact membrane distillation is carried out, and the influence of feed inlet temperature, feed inlet concentration, membrane pore diameter on flow field and temperature field distribution is analyzed compared with experiments. A new form of heat recovery air gap membrane distillation is proposed for high heat loss direct contact membrane distillation structure. The new module can maintain the air gap temperature, strengthen condensation, and increase the permeation flux while recovering part of the latent heat of condensation. At the same time, the heat and mass transfer process of the new form of heat recovery air gap membrane distillation module are analyzed. Moreover, low grade energy and membrane distillation system are coupled. The coupled system can utilize factory waste heat, solar energy, geothermal energy as heat source, which can decrease the energy consumption effectively.
  
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  Holistic Optimization of the Distributed Energy Systems Considering Nonlinear Characteristics

  XU Ronghong, ZHAO Tian, LÜ Hongkun, GUO Xutao, MA Huan, GOU Xing, CHEN Qun

  Journal of Engineering Thermophysics. 2025, 46(1): 276-285.

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  The coupling of multi-energy transportation and conversion processes in distributed integrated energy systems is highly nonlinear, posing challenges for detailed modeling and analysis. This study presents a comprehensive mathematical model of the system based on the heat current model, incorporating power system load flow constraints. It fully considers the nonlinear characteristics of multi-energy transportation and conversion within the system. Furthermore, an iterative optimization algorithm, employing the idea of divide and conquer, is proposed to achieve efficient and robust operation optimization of the system. The results demonstrate that the optimized model presented in this study provides more accurate results. Neglecting the nonlinear heat transfer constraints leads to a relative error of up to 36.7% in the heating capacity of the electric heating device, while neglecting the bus voltage constraints results in a relative error of up to 57.3% in the real-time heat storage capacity of the thermal storage device.
  
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  Solving and Analysis of Steady-Flamelet Equation Under Trans/Supercritical Conditions

  CAO Hanzhang, LÜ Yu, HAN Wang, FU Qingfei, YANG Lijun

  Journal of Engineering Thermophysics. 2025, 46(1): 286-299.

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  In this paper, based on the FlameMaster program, a trans/supercritical calculation function package is developed to solve the steady-flamelet equation under trans/supercritical conditions. Firstly, a trans/supercritical combustion model is constructed to explain the thermodynamic behavior of the transcritical fluid deviating from the ideal gas in the “pseudo-boiling” region through the cubic real fluid state equation, and the parameters such as thermodynamic properties and transport properties are modified by the real fluid effect. Then, the above model is implanted into FlameMaster and the relevant numerical methods are adjusted to ensure the stable convergence of the solver. Finally, the modified FlameMaster program was verified by a typical working condition example. On this basis, taking the trans/supercritical LOX/GH2 flame as an example, some important details and results in the process of model implementation are studied, including the difference between the results obtained by using different real fluid state equations, the deviation between the real fluid model and the ideal gas model, and the influence of grid algorithm factors on the calculation results, and the influence of different condition parameters on the flame structure is further studied by using the phase diagram method.
  
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  Study on Ignition and Combustion Characteristics of Gliding Arc Plasma Combustion Dome

  ZHANG Lei, YU Jinlu, ZHAO Bingbing, ZHANG Dengcheng, WANG Xiaomin, HU Yaji

  Journal of Engineering Thermophysics. 2025, 46(1): 300-309.

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  To verify the effectiveness of ignition and combustion support at the head of a gliding arc plasma combustion dome, a single dome swirl combustion experimental platform was established. The ignition and combustion characteristics of gliding arc plasma combustion dome were studied, with a focus on analyzing the influence of the gliding arc plasma on the ignition process, ignition/extinction boundary, and combustion reaction zone. Research has shown that gliding arc plasma ignition has changed the ignition and combustion process of traditional combustion chambers, expanding the stable combustion range of the combustion chamber. The ignition boundary can be widened up to 36.7%, and the extinction boundary can be widened up to 83.4%; The gliding arc plasma assisted combustion increases the area of the combustion reaction zone, reduces fragments in the reaction zone, and increases the combustion opening angle.
  
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  Simulation of Porous Media Combustion Considering Morphology: Effect of Cell Structure and Porous Material

  LI Liang, ZHANG Ruifang, ZHANG Yang, ZHANG Hai

  Journal of Engineering Thermophysics. 2025, 46(1): 310-318.

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  Porous media combustion can improve the burning rate and flame stability, achieve stable flame in ultra-lean/rich conditions, and expand the flammability limit. Based on the assumption of homogeneous porous media, a combustion model considering multiple porous media morphological features is established, and the combustion characteristics in porous media with different structural and material parameters are calculated. The results show that five parameters, namely, porosity, mean pore diameter, tortuosity, material thermal conductivity and emissivity, affect the combustion state in porous media by influencing the gas-solid heat transfer, thermal conductivity and radiation processes. Due to the effect of radiation, the pore structure has a more significant effect on the combustion rate compared to the material parameters, smaller pore diameter and higher tortuosity will improve the gas-solid heat transfer process and enhance the burning rate, while overly intense gas-solid heat transfer will enhance the radiative heat loss, and lead to combustion instability and quenching in porous media. The trend of the cell structure and porous material influence on the porous media combustion characteristics obtained from the model calculations is consistent with the experimental results.
  
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  Investigation of the Ignition Characteristics for Biomass Single Particles Under Ammonia-doped Atmospheres

  CHEN Chenlin, WANG Zhihua, WANG Xiaobo, HE Yong, WENG Wubin

  Journal of Engineering Thermophysics. 2025, 46(1): 319-325.

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  Based on CH* chemiluminescence signal images, the ignition characteristics of biomass single particles during the combustion processes in normal and ammonia-doped conditions were systematically investigated. The effects of various parameters including biomass fuel type, ammonia doping, oxygen content in the background gas and the particle size of biomass on the ignition delay time for biomass fuels were studied. The results revealed that the devolatilization process and combustion reaction rate of biomass particles were significantly accelerated. The ignition delay times of corn straw and wheat straw particles were shortened and the combustion intensities were enhanced. Increasing the oxygen content of background flue gas and decreasing the particle size could accelerate the ignition processes of biomass fuels.
  
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  Converging Curve for Shockwave Enhancement in Chemical Shock Tube

  BAI Shijie, LI Shilong, LIANG Xingyu, WANG Kun

  Journal of Engineering Thermophysics. 2025, 46(1): 326-335.

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  The intensity (pressure) of the reflected shock and its duration (test time) are the two main indicators of the performance of chemical shock tubes. Convergence curves are capable of creating stronger shock under the same initial conditions. However, they may bring in pressure peaks after the reflected excitation that cannot be maintained at a constant level. The main objective of the present study is to construct convergence curves suitable for use in chemical shock tubes with a constant pressure region after reflecting the excitation wave and a waveform distribution with less curvature. Firstly, based on the principles of gas dynamics and excitation wave dynamics, mathematical models with eight different convergence profiles were established. Secondly, a twodimensional model of the shock tube with different convergence curves is constructed. Finally, the waveform distribution of the internal wave system of different chemical shock tubes was investigated, and the change rule of test time and pressure value after the reflected shock wave was revealed. Results show that the convergence curve based on shock dynamics with an inclination angle of 2° forms a longer pressure constant zone after reflected shock wave and the waveform curvature is minimum.
  
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  Catalytic Performance of Ni/SSZ-13 Catalyst Doped With Transition Metal for CO₂ Methanation

  HUANG Jun, YANG Yingju, LIU Jing, BAI Hongcun

  Journal of Engineering Thermophysics. 2025, 46(1): 336-341.

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  Based on hydrogen production from water electrolysis, the synthesis of CH₄ through CO₂ thermal catalytic reduction is an ideal conversion pathway. In order to develop high-performance CO₂ methanation catalysts, Ni/SSZ-13 catalysts doped with transition metals (Mn, Fe, Co, Cu, Zn) were prepared by co-impregnation method, and the effects of transition metals doping on the methanation performance of the catalysts were investigated. The results show that Mn-Ni/SSZ-13 catalyst shows the best CO₂ methanation performance, and Mn doping can maximize the performance of Ni/SSZ-13 catalyst. CO₂ conversion and CH₄ selectivity of Mn-Ni/SSZ-13 catalyst are 84.62% and 98.02% when the mass fraction of Mn doping is 2%, respectively. Zn or Cu doping enhances the CO selectivity of CO₂ methanation, which is beneficial to the reverse water gas shift reaction.