28 October 2025, Volume 34 Issue 6
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Journal of Thermal Science. 2025, 34(6): 1965-1977. https://doi.org/10.1007/s11630-025-2155-9This study investigates the direct impact of heat transfer on the thermodynamic performance of Micro Swing Rotor Engines (MSRE) through numerical analysis. To comprehensively address the influence of heat transfer, we employ a refined thermodynamic simulation model, incorporating a regressive correlation formula, and introduce a fluid-thermal weak coupling method to yield practical solutions. The numerical analysis reveals that heat transfer has profound effects on the performance of MSRE. Specifically, the temperature cycling curve experiences significant alterations, resulting in an increase in cycle-residual mass by 72.6% and a decrease in intake mass by 10.55% at a working frequency of 100 Hz. The pressure cycling curve is primarily affected during the compression and expansion processes, leading to a substantial rise in pressure during compression (reaching 1.055 MPa) while the contribution of combustion becomes less noticeable. Consequently, these changes increase engine power consumption during compression by 46.41% and reduce overall engine thermal efficiency by 30.23%. Additionally, an increase of the inner wall temperature by 100 K leads to a linear reduction in engine power by 0.1 kW and thermal efficiency by 0.5%. To mitigate these challenges, we propose practical heat management strategies, such as applying heat insulating coatings. The study underscores the critical roles of heat transfer in MSRE operation and provides insights for optimizing its thermodynamic performance, achieving a potential improvement of up to 54.68% in power output and 12.79% in efficiency.
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Journal of Thermal Science. 2025, 34(6): 1978-1995. https://doi.org/10.1007/s11630-025-2148-8In the micro-clearance of the valves and sealing structures of liquid hydrogen (LH2) storage tanks, bubbles occur due to heat leakage. The sudden rising of pressure causes bubbles to collapse, resulting in pressure and temperature fluctuations that impact the sealing surface and the valve. In this paper, the cryogen cavitation model is modified by considering the thermal effect, surface tension, and viscosity. The bubble collapse inside micro-clearance is investigated by the modified cavitation model and volume of fluid (VOF) method. Transient pressure and temperature at the bubble center during collapse are recorded and evaluated. The effects of micro-clearance height, dimensionless bubble diameter, and bubble vertical position on bubble collapse and bubble morphology are investigated. To reduce the cavitation erosion on the walls, the frequency and time-frequency characteristics of the pressure oscillations induced by bubble collapse are analyzed by Fast Fourier Transform (FFT) and Wavelet Transform (WT). Furthermore, the temperature and pressure field variation and oscillation mechanisms are analyzed by Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD). The analytical results reveal the LH2 bubbles collapse mechanism within the micro-clearance. The results provide a certain extent of reference for optimizing the structure of micro-clearance.
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Journal of Thermal Science. 2025, 34(6): 1996-2008.High temperature and pressure are the main challenges faced in the exploration of deep earth sciences. In order to ensure the safe drilling of high-temperature and high-pressure wells, a thick-walled simulated wellbore device is proposed and its heat transfer characteristics are studied according to the test requirements of pressure bearing exceeds 25 MPa and temperature exceeds 673.15 K. To investigate the dynamic heating process of the fluid within the cylinder, a mathematical model was developed to describe the coupled heat transfer mechanisms. This model incorporates the nonlinear properties of the fluid inside the cylinder. The results reveal that the temperature field distribution during the dynamic coupling heat transfer process is influenced by the electromagnetic induction current and the internal flow within the cylinder. During heating, the liquid transitions from a subcritical to a supercritical state. Buoyancy arising in the heating process affects the temperature distribution within the container and the formation of vortices. Incorporating a cooling system at the top of the container effectively maintains low-temperature operation in the sealing area. Additionally, the study shows that higher currents significantly increase both the final average liquid temperature and the cylinder wall temperature compared to the initial conditions. The proposed model and solution methodology provide a reliable approach for simulating fluid-structure coupled heat transfer in high-temperature, high-pressure well environments, offering a theoretical foundation for designing simulated wellbore heating systems.
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Journal of Thermal Science. 2025, 34(6): 2009-2045. https://doi.org/10.1007/s11630-025-2197-zAs an emerging cooling solution, the technology of using liquid metal as a cooling medium for chips has been the subject of many classic studies. This considerable critical attention stems from the practicality and broad applicability of liquid metal in addressing the thermal management challenges posed by 3D ICs (Three-Dimensional Integrated Circuits). Recognized for its superior heat transfer properties, liquid metal shows significant potential to replace traditional heat transfer fluids. Compared to conventional chip cooling methods, liquid metal-based technologies offer higher heat dissipation efficiency and improved performance. This paper analyses research on liquid metal chip cooling, categorizing the findings into five key areas: cooling medium selection, channel design, drive pump analysis, system performance evaluation methods, and the co-design of liquid metal microfluidic chip heat dissipation systems. The comprehensive review is expected to provide a theoretical reference and technical guidance for liquid metal-based chip cooling technologies.
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Journal of Thermal Science. 2025, 34(6): 2046-2058. https://doi.org/10.1007/s11630-025-2194-2Solar-driven interfacial water evaporation technology offers a zero-carbon, sustainable solution for extracting clean water from seawater and wastewater, presenting an effective strategy to address the global water crisis. This study has employed finite element simulation to investigate the solar interfacial evaporation process, elucidating the interactions between heat, water, and salt during evaporation. Additionally, the internal water channels of the evaporator are optimized and designed using topology optimization techniques. In this project, a cylindrical evaporator model with vertical micropores is developed from carbon-based polymer materials. The impact of pore diameter and spacing on the evaporation rate is analyzed, alongside the effects of thermal conductivity, solar radiation intensity, and ambient wind speed on the evaporator’s performance. Simulations have revealed that with a pore diameter of 20 μm and a spacing of 0.55 mm, the evaporator achieves the highest evaporation rate of 0.91 kg·m–2·h–1. The findings indicate that smaller pore sizes substantially enhance the evaporation rate, while larger pore spacings initially increase, and then decrease the rate. Further optimization involves using 20 μm-diameter round pores and adjusting the cross-sectional shapes of the pores based on topological configurations with a material volume factor of 0.5. The optimized structure demonstrates an evaporation rate of 2.91 kg·m–2·h–1, representing a 219.78% increase over the unoptimized design. These optimized structures and simulation results provide valuable insights for future evaporator designs.
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Journal of Thermal Science. 2025, 34(6): 2059-2071. https://doi.org/10.1007/s11630-025-2202-6Challenges of electronic cooling are becoming increasingly urgent due to the exponential rise in power densities and the non-uniform distribution of heat sources. Vapor chambers utilizing liquid-vapor phase change heat transfer are appealing due to their high performance and potentially low cost. However, heat dissipation performance, depending on the thin film evaporation, is limited by the capillary dry-out of wicking structures. Here, we demonstrate a large-scale vapor chamber enabled by high-performance liquid film boiling mode on the hierarchical mesh-wicking structures for high-power electronics cooling. The composite columns integrating with copper foam and copper powder are patterned in a zoned configuration to promote vapor diffusion and two-phase flow. The effects of the filling rate and cooling water temperature on the vapor flow and liquid film distribution are investigated. The results show that the X-shaped distribution of composite columns in the heat source region promotes the vapor diffusion throughout the vapor chamber, resulting in a thermal resistance of 0.04°C/W at the heat flux of 100 W/cm2 from an area of 775 mm2. The findings provide theoretical guidance for the structure design of high-performance large vapor chambers.
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Journal of Thermal Science. 2025, 34(6): 2072-2086. https://doi.org/10.1007/s11630-025-2195-1The performance of a nanofluid-filtered PV/T system largely depends on the properties of the selected nanofluid. In this study, Fe3O4@SiO2 nanofluid is synthesized via the sol-gel method, and its optical and thermal properties are systematically evaluated. Optical tests show that Fe3O4@SiO2 nanofluid exhibits high transmittance in the 650–1075 nm wavelength range and strong absorbance in the visible spectrum. Thermal stability tests under continuous heating confirm its suitability as an optical filter for PV/T systems. Indoor experiments are conducted to assess the effects of Fe3O4@SiO2 nanofluid on the performance of filtered PV/T systems at varying mass concentrations and optical thicknesses. The results indicate optimal system performance with an optical thickness of 2 cm and a mass concentration of 50×10–6, achieving an MF (merit function) value of 1.802. Subsequently, flow rate experiments are performed to evaluate thermal efficiency and MF across various flow rates. At a flow rate of 6 mL/min, thermal efficiency reaches 79.4%, and the MF value increases to 2.34. Additionally, the Fe3O4@SiO2 nanofluid optical filter significantly reduces the operating temperature of photovoltaic cells. After one hour of illumination, the PV cell temperature decreases by 36.43%, mitigating thermal-induced performance degradation. These findings provide a solid foundation for the optimization and practical application of filtered PV/T systems.
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Journal of Thermal Science. 2025, 34(6): 2087-2103. https://doi.org/10.1007/s11630-025-2089-2Lithium-ion batteries’ safe and effective functioning depends on reliable and precise heat control. In this study, we explore the thermal behaviour of a 48-V, 30-Ah LiCoO2 battery pack utilising an unconventional transient thermal analysis technique with a simplified constant heat-generating formula based on the Bernardi equation. This work assessed the effect of several discharge rates and heat transfer coefficients on thermal performance by modelling temperature distribution and heat dissipation inside the battery pack. Heat transfer coefficients 5 W/(m2·K) for natural air convection, 10 W/(m2·K) for forced convection of air and discharge rates 0.5C, 1C, 1.5C and 2C on thermal performance were investigated using a sensitivity analysis. The results show that forced convection improves temperature distribution and considerably enhances heat dissipation at a discharge rate of 0.5C. However, the study reveals that advanced thermal management techniques are especially vital. Even forced air convection finds it difficult to maintain temperatures within the optimal range at higher discharge rates, thus emphasizing the need to optimise cooling conditions to guarantee thermal stability and prevent hotspots. The findings underline and offer insightful analysis of the relative impact of discharge rates and cooling conditions on lithium-ion battery pack thermal behaviour.
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Journal of Thermal Science. 2025, 34(6): 2104-2122. https://doi.org/10.1007/s11630-025-2178-2Based on flow decomposition, the integrals of the moment of momentum equation, flow equation and energy equation of regenerative hydrogen pumps are established. Among them, the inflow of impeller passage is expressed as the result of outflow and the forces in side channel. Additionally, a new design procedure is developed based on this flow model. Through this procedure, the main geometric parameters of flow passage parts can be obtained from the required pressure rise and flowrate. A parametric study of blade angle and blade number is carried out as a necessary part of the content completion for the design procedure. Based on the flow model, the simulation results of the flow field with different flowrates, rotational speeds, blade angles and blade numbers are analyzed; while the reasons for the variation of efficiency and pressure rise with these parameters are discussed. At the same time, the range of blade angles and blade numbers that are beneficial to performance is summarized.
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Performance Prediction and Parameter Optimization for Asymmetric Proton Exchange Membrane Fuel CellsJournal of Thermal Science. 2025, 34(6): 2123-2139. https://doi.org/10.1007/s11630-025-2141-2Global optimization of fuel cells is a key approach to enhance performance and extend lifespan. Furthermore, the response surface method can provide accurate predictive results with minimal data. This study utilizes the response surface method alongside a two-dimensional agglomerate model to perform numerical simulations of asymmetric proton exchange membrane fuel cells, focusing on thickness and operating parameters. The study analyzes the interactions among parameters and aims to identify optimal values for maximum power density. The structural and operational parameter optimization models have been developed, with average errors of 2.28% and 0.29%, respectively, leading to produce a predictive model with an average error of less than 3% ultimately. The optimized power density increased by 57.4%, with inlet pressure identified as the most influential factor. The asymmetric design enhances gas transport in the porous media region. Among the structural parameters, cathode thickness has a greater impact; while among the operating parameters, pressure exerts the greatest impact on cell performance. The optimal temperature ranges from 333 K to 343 K, with a noticeable marginal effect. Higher relative humidity can enhance power density, and it’s worth noting that cathode humidity is more sensitive to power density than anode humidity. A well-designed asymmetric configuration can enhance the water and thermal management of the fuel cell, leading to improved energy efficiency.
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Journal of Thermal Science. 2025, 34(6): 2140-2153. https://doi.org/10.1007/s11630-025-2177-3The autoignition process of methanol/n-heptane dual-fuel (DF) premixtures is studied in a simplified inflow-outflow configuration using numerical simulations under engine-like conditions. Variations in the initial gas temperatures, inlet velocities, and methanol substitution ratio (MSR) on the low-temperature combustion (LTC) and high-temperature combustion (HTC) of DF mixtures are investigated. The LTC is initiated at the locations close to the inlet. A propagating hot flame front is observed after the formation of the HTC. Both the LTC and HTC are delayed at a high value of the MSR. The negative temperature coefficients (NTC) characteristics are insignificant when the MSR reaches 54% due to the decreased LTC at a low concentration of n-heptane. The ignition delay times (IDTs) for the DF mixtures are prolonged with the increase in the MSR due to the competition of OH between n-heptane and methanol. OH is consumed by the reaction pathway CH3OH+OH=CH2OH+H2O, which inhibits the autoignition of fuel/air mixtures and delays the second-stage ignition of n-heptane. Meanwhile, the longer residence time causes a longer distance between the HTC region and the inlet. Finally, the ignition Damkӧhler number (Daign) defined as the ratio of the residence time to the IDT is introduced to reveal the stabilization process of the DF mixtures. The values of the Daign are all lower than unity at different inlet velocities and MSR, indicating that diffusion plays a critical role for LTC. However, larger values of Daign are observed for the HTC indicating that autoignition dominates the oxidization process.
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Journal of Thermal Science. 2025, 34(6): 2154-2166. https://doi.org/10.1007/s11630-025-2191-5Extreme weather and natural disasters have plagued people for a long time, and ensuring power source provision in such emergency situations is an urgent problem that needs to be solved. Combustion powered thermoelectric generator (CPTEG) is a promising solution to the power supply problem in off-grid areas and under emergency conditions. Adding hydrogen into the fuel is one of the effective ways to reduce carbon dioxide in the context of “Emission Peak” and “Carbon Neutrality”. In this study, the feasibility of the blended propane-hydrogen to power up a CPTEG is investigated, filling a research gap of standalone hydrogen CPTEG with an input power of kilowatt level. The combustion characteristics and the CPTEG performance at different hydrogen ratios (0%‒50%) were investigated, including the combustion temperature, hot-/cold-end temperatures, electric power, thermoelectric efficiency (electric power related to the heat flow rate passing through the thermoelectric module), systematic efficiency, and system effectiveness (EFS). Experimental results showed that the combustion is stable and a blue flame is anchored when the hydrogen ratio is less than 45% under the input power of 800 W, whereas the combustion becomes unstable and a bright yellow flame is detected when the hydrogen ratio exceeds 45%. The hydrogen addition considerably affects the CPTEG performance. The electric power is decreased by 13.0% (3.8 W) under the hydrogen ratio of 45% compared to that generated by burning pure propane when the input power is 800 W. The hydrogen addition impacts the combustion characteristics of CPTEG. The combustion stability has been improved, which is contributed by the reduced coefficient of variation. It is found that the standard deviation (SD) and coefficient of variation (COV) of flame temperature both sharply decreased by 66.8% under the hydrogen ratio of 45%. In addition, the hydrogen addition impact the carbon dioxide in the exhaust gas of CPTEG, and the CO2 concentration decreased by 11.5% under the hydrogen ratio of 45%. Furthermore, the total electric power and thermoelectric efficiency of the developed CPTEG are 32.4 W and 3.24%, respectively.
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Journal of Thermal Science. 2025, 34(6): 2167-2176. https://doi.org/10.1007/s11630-025-2169-3An optical method is developed for determining the sooting limit in premixed burner-stabilized stagnation flame. The impact of a stagnant plate at varying heights above burner (HAB) on the sooting limit is investigated using the method. The method quantifies the soot generation by processing pixel values in the region of interest of flame images. In a series of consecutive conditions from soot-free flame to soot-rich flame, the sooting limit is identified by observing the occurrence of soot formation. Experimental results demonstrate that this method could effectively capture the sooting limit. A comparison of the sooting limit at different HABs reveals that when the HAB is lower than 10 mm, the stagnant plate has an inhibitory effect on soot generation, and the equivalence ratio required for the sooting limit increases as the HAB decreases. When the HAB is higher than 10 mm, the stagnant plate ceases to impact the sooting limit.
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Journal of Thermal Science. 2025, 34(6): 2177-2195. https://doi.org/10.1007/s11630-025-2158-6Pollutant emissions from coal-fired power plants are a significant contributing factor to the increasing environmental issues, making the clean and efficient use of energy crucial in addressing and alleviating these problems. Therefore, this paper proposes a new parabolic trough solar-assisted coal-fired power generation system integrated with waste heat utilization and carbon capture. Based on the principle of energy grade matching and cascade utilization, a portion of the feedwater is directed to drive the carbon capture subsystem and the working medium of the Kalina cycle before being further heated by solar energy. A pulverized coal power generation system is used as the reference system (Case 1); the parabolic trough solar sub-system, Kalina cycle sub-system, and monoethanolamine carbon capture sub-system are respectively integrated with the reference system to form three different new systems of Case 2, Case 3, and Case 4; then a 4E analysis is conducted for these four Cases. The results of this study indicate that these four Cases have system thermal efficiencies of 44.87%, 44.09%, 44.14%, and 43.96% in the power-boosting operation mode, and exergy efficiencies of 44.36%, 43.67%, 43.69%, and 43.52%, respectively. The levelized cost of electricity of Case 1 is 42.62 USD/MWh, and those of Case 2 and Case 3 decrease to 42.15 USD/MWh and 42.16 USD/MWh, respectively; the levelized cost of electricity of Case 4 is 42.67 USD/MWh. The CO2 emission rates of Cases 2–4 are reduced by 11.4 g/kWh, 12.3 g/kWh, and 17.6 g/kWh, respectively, compared to Case 1. This study is expected to offer the possibility of designing solar-assisted coal-fired power generation system with lower carbon emission.
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Journal of Thermal Science. 2025, 34(6): 2196-2203. https://doi.org/10.1007/s11630-025-2192-4The methane concentration in the atmosphere is far lower than that of carbon dioxide, but it is more potent, accounting for 30% of the global greenhouse effect. Although removing atmospheric methane would be an effective way to mitigate climate change, no practical methods have been identified. The enhancement of the oxidative capacity of ecosystems to remove atmospheric methane is a green approach. This paper presents the novel concept of utilizing a solar chimney power plant (SCPP) associated with a solar pond to remove atmospheric methane. In the proposed system, the production of both hydroxyl radicals from ozone photolysis and chlorine atoms from converting Fe (III) to Fe (II) under optimized conditions degrades the atmospheric methane. The results reveal that a 200 MW SCPP associated with a solar pond could eliminate 0.22 million tons of atmospheric methane per year. The construction of 5400 systems worldwide could remove 1.19 billion tons of atmospheric methane per year, achieving the climate goal of a temperature rise of less than 2°C this century. The devices require an investment of about 3.5748×1012 EUR. Although the proposal seems a promising way to mitigate the effects of a warming climate, a comprehensive model must be developed to evaluate its feasibility.
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Journal of Thermal Science. 2025, 34(6): 2204-2209. https://doi.org/10.1007/s11630-025-2166-6Nitrate salts have better thermal stability, low vapour pressure and non-toxic nature compared to synthetic heat transfer oil like Therminol VP-1®. Solar salt, a mixture of 60% NaNO3-40% KNO3 by weight, is finding increased application as a Heat Transfer Fluid (HTF) and Thermal Energy Storage (TES) material in Concentrated Solar Power (CSP) plant. In this research work, two novel salt mixtures are prepared and tested for their melting point, short and long duration thermal stability. The formulation 1 is a ternary salt comprising of 44% KNO3-32% Ca(NO3)2-24% NaNO3, referred to as Base Salt. Formulation 2 is a quinary mixture of 90% Base salt- 5% NaCl-5% KCl, referred to as Base-Chloride. Solar salt, a third formulation, is also tested and compared alongside the novel mixtures. The experiments conclude that the melting point of solar salt is 223°C, Base salt is 135.8°C and Base-Chloride is 142.2°C. When heated at 5°C/min, the decomposition (3% mass loss) of solar salt is observed at 631°C, Base salt at 585°C and Base-Chloride at 589°C. Considering long duration stability, all the three mixtures remain stable till 400°C, when heated at constant temperature for 24 hours. The novel mixtures have significantly lower melting points, thus providing wider operating temperature range compared to solar salt for both heat transfer and energy storage application. Moreover, it is observed that addition of chloride salt as an impurity to a nitrate mixture does not change its operating range significantly.
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Journal of Thermal Science. 2025, 34(6): 2210-2229. https://doi.org/10.1007/s11630-025-2198-yThe rapid commercialization of Phase Change Materials (PCMs) for HVAC applications effectively leverages ambient temperature fluctuations to meet growing energy demands in buildings. This study outlines a systematic approach to passively integrate PCM into building roofs for cooling load reduction. The process involves PCM selection, characterization, analysis of melting front propagation, and thermal performance assessment. Thermal/digital imaging approach tracks the melting front’s propagation, revealing significant natural convection due to heat flux from modules bottom surface. Melting front propagation occurs primarily in one dimension. Two identical roof slab units are fabricated and tested in Rupnagar City, India, for assessing thermal performance, with one unit equipped with PCM (PSU) and the other as a conventional reinforced slab unit (CSU). Various energetic and thermal performance metrics, including Maximum Temperature Reduction (MTR), Operative Temperature Difference (OTD), Heat transfer, electricity cost savings (Esc), Discomfort Hours Reduction (DHR), and Maximum Heat Gain Reduction (MHGR), are evaluated. PCM integration results in a significant MTR of 4°C and a 60% reduction in heat flux compared to the conventional unit. Moreover, the PCM room exhibits an 11.2% and 34.8% enhancement in thermal comfort, as indicated by DHR and MHGR, respectively, compared to the reference unit. In addition, considering heating and cooling spaces, it offers a maximum daily saving of 0.06 USD/(kWh∙m2). These findings highlight PCM’s potential to mitigate temperature fluctuations, enhance thermal comfort, and reduce energy consumption in severe climatic conditions.
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Journal of Thermal Science. 2025, 34(6): 2230-2249. https://doi.org/10.1007/s11630-025-2205-3Recently, using biomass waste to extract levulinic acid (LA) has aroused extensive concerns. This research provides a novel LA preparation system with the use of biomass waste in combination with a coal-fired power plant (CFPP). As a poly-generation system, it not only produces LA, but also generates heat and electricity to self-sustain the energy consumption. Besides, the material balance, thermodynamics and economics of the system are investigated. Findings indicate that the purity of the refined LA can achieve 99.8% and the energy demand per unit mass of LA is 62.14 MW, which is 36.96 MW lower than the same scenario in previous studies. The total energy efficiency and exergy efficiency for the whole process reach 55.16% and 61.36%. Overall, the system will achieve payback of the initial investment in 3.42 years, and the proposal is projected to have a net present value (NPV) of 1.472 203 7×108 USD over its 30-year lifespan.
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Journal of Thermal Science. 2025, 34(6): 2250-2261. https://doi.org/10.1007/s11630-025-2207-1Pressurized oxy-fuel combustion is a potential combustion technology with high efficiency and low-cost CO2 capture capacity. However, there is currently limited research on the basic experimental due to the difficulty of experiments, with the predominant focus residing in low-pressure regimes and a dearth of exploration in high-pressure environments. Since the ignition and devolatilization is as the initial step, contributes significantly to the process of coal combustion, this study examines the ignition and devolatilization characteristics of single bituminous coal and anthracite particles in O2/CO2 condition under pressures of 0.1 to 4 MPa using a visualized high-pressure drop tube furnace (HP-DTF). The dynamic combustion process at this high-pressure environment is captured, facilitating the determination of ignition delay time (IDT) and devolatilization time (DT) of single-particle coal. The results demonstrate that the IDT of coal particles will be lengthened relative to the ambient pressure under the fixed oxygen volume fraction. Bituminous coal and anthracite exhibit homogeneous ignition and heterogeneous ignition respectively. Bituminous coal initially experiences a rapid increase in IDT, followed by a gradual decrease; the drastic change of gas phase properties and the release of volatiles are the main factors leading to the increase of ignition delay, comparing to with 0.1 MPa pressured oxy-fuel combustion. The promotion of volatile ignition occurs as a result of increased oxygen partial pressure and a higher heat transfer coefficient, which leads to the shortening of the subsequent IDT. Also, the devolatilization time of bituminous coal showed a positive correlation with pressure, and the value at 4 MPa is about twice that at atmospheric pressure. In summary, this study of the coal ignition deepens the understanding of flame characteristics in the pressure oxygen combustion, which lays a solid foundation for the future pressured oxy-fuel combustion industrial application.
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Journal of Thermal Science. 2025, 34(6): 2262-2273. https://doi.org/10.1007/s11630-025-2196-0The spray and flow structures generated from the injectors of the lean premixed prevaporized (LPP) combustor are essential to the research and development of modern aero-engines. In this work, we develop an optical model combustor featuring five linearly arranged LPP injectors and a laser diagnostics system based on high-repetition-rate and high-energy pulse lasers to study the spray and flow field characteristics. The effects of varying fuel and airflow rates on the spray cone area and droplet spatial distribution as well as on the mean flow structures and dynamics are experimentally investigated using high-speed particle image velocimetry (PIV), planar laser-induced fluorescence (PLIF), and planar MIE scattering (PMIE). The results demonstrate that the impingement of adjacent sprays is crucial to the formation of the outer recirculation zones (ORZ) among injectors. The fuel-to-air ratio (FAR) has an overall significant effect in controlling the flow and spray characteristics. The combined analysis of the velocity fluctuations and spray reveals that, with increasing FAR, the turbulent intensity diminishes in the shear layer, contributing to an inhibition of the liquid fuel breakup and eventually a deteriorated atomization performance characterized by the denser distribution of large-size droplets in the central recirculation zone.
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Journal of Thermal Science. 2025, 34(6): 2274-2286. https://doi.org/10.1007/s11630-025-2206-2The Dielectric-Barrier-Discharge (DBD) plasma actuator is a highly efficient active flow control device, being widely recognized for its potential applications in boundary layer separation control. While many researchers have explored the practical implementation and performance of DBD plasma actuators in various aerodynamic contexts, the fundamental physical mechanisms governing plasma-induced flow control remain relatively under-explored. The present study utilizes numerical simulation to investigate the plasma-induced flow dynamics around a circular cylinder, whose configuration is selected due to its geometric simplicity and the prominent boundary layer separation that occurs due to its highly curved surface. The flow field is simulated by solving the Unsteady Reynolds Averaged Navier Stokes (URANS) equations while the plasma actuation effect is incorporated through a well-known mathematical model. In this study, two DBD plasma actuators are symmetrically installed on the left and right sides of the cylinder. The ambient air is set to be initially quiescent and the resulting flow field is driven entirely by the plasma. This research makes two primary contributions. First, the flow fields generated under duty-cycle actuation signals are simulated and validated against existing experimental data. Particular attention is given to the generation, evolution and propagation of vortex structures arising from different actuation modes. Second, a detailed analysis is conducted on how a time-varying plasma body force affects the distribution of pressure force, skin friction and momentum transfer.
