As 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.

The absorption cycle is a promising technology for harnessing low-temperature heat, playing a crucial role in achieving the objectives of carbon peaking and carbon neutrality. As a significant element in distributed energy systems, the absorption cycle can utilize various types of low-grade heat to fulfill cooling, heating, and electrical energy demands. Therefore, it can be employed in diverse settings to unleash its substantial energy-saving potential. However, the widespread adoption of the absorption cycle is limited to specific scenarios. Hence, further efforts are needed to enhance its technological maturity, gain societal acceptance, and expand its application scope. Focusing on the utilization of different low-grade heat, this paper provides an overview of significant advancements in the application research of various absorption cycles, such as the absorption refrigeration cycle, absorption heat pump, absorption heat transformer, and the absorption power cycle. According to current research, absorption cycles play a critical role in energy conservation and reducing carbon dioxide emissions. They can be applied to waste heat recovery, heating, drying, energy storage, seawater desalination, refrigeration, dehumidification, and power generation, leading to substantial economic benefits. The paper also outlines the primary challenges in the current application of the absorption cycle and discusses its future development direction. Ultimately, this paper serves as a reference for the application research of the absorption cycle and aims to maximize its potential in achieving global carbon neutrality.

Recent research and development on ramjet and supersonic combustion ramjet (scramjet) engines is concerned with producing greater thrust, higher speed, or lower emission. This is most likely driven by the fact that supersonic/hypersonic propulsion systems have a broad range of applications in military sectors. The performances of such supersonic/hypersonic propulsion systems depend on a series of physical and thermodynamic parameters, such as the fuel types, flight conditions, geometries and sizes of the engines, engine inlet pressure/velocity. As a propulsion system, a stable and efficient combustion is desirable. However, self-excited large-amplitude combustion oscillations (also known as combustion instabilities) have been observed in liquid- and solid-propellant ramjet and scramjet engines, which may be due to acoustic resonance between inlet and nozzle, vortex kinematics (large coherent structures), and acoustic-convective wave coupling mechanisms due to combustion. Such intensified pressure oscillations are undesirable, since they can lead to violent structural vibration, and overheating. How to enhance and predict the engines’ stability behaviors is another challenge for engine manufacturers. The present work surveys the research and development in ramjet combustion and combustion instabilities in ramjet engines. Typical active and passive controls of ramjet combustion instabilities are then reviewed. To support this review, a case study of combustion instability in solid-fueled ramjet is provided. The popular mode decomposition algorithms such as DMD (dynamic mode decomposition) and POD (proper orthogonal decomposition) are discussed and applied to shed lights on the ramjet combustion instability in the present case study.

Paraffin (PA) is a common phase change material, which is widely used in battery thermal management systems (BTMS) because of its high latent heat and temperature uniformity, simple system structure, and no increase in battery energy consumption. In this work, sulfur-free expanded graphite (EG) is prepared by oxidation intercalation without H₂SO₄ in the preparation process, which avoids the harm to devices caused by the S element. The sulfur-free EG exhibits a high expanded volume of 324 mL·g^–1, which can adsorb PA well to prevent leakage. When the mass filling ratio of EG is 5.0%, EG/PA-5.0 composite films show high latent heat of phase transition (253.08 J·g^–1), and thermal conductivity (2.56 W·m^–1·K^–1). EG/PA films are attached to the external surface of the lithium iron phosphate battery for a heat dissipation performance test. When the discharge rate is 1C at room temperature, the surface temperature and maximum temperature difference between temperature measurement points of the battery with EG/PA-5.0 film are 32.1°C and 1.2°C. After charge-discharge at 1C for 100 cycles, the thermal properties of EG/PA remain basically unchanged, and it has good cycle stability. The simulation results are in good agreement with the actual temperature changes of the battery at different discharge rates. This work indicates that sulfur-free EG/PA composite has a good application prospect in BTMS of the power batteries.

As the total amount and share of new energy installed capacity continue to rise, the demand for flexible regulation capability of the power system is becoming more and more prominent. The current conventional molten salt energy storage system has insufficient peaking capacity. A solar-molten salt energy storage system based on multiple heat sources is constructed in this study. The heat generated from the solar field and the steams are used for the peaking process to further enhance the peaking capacity and flexibility. The installation multi-stage steam extraction and the introduction of an external heat source significantly improve the system performance. The simulation models based on EBSILON software are developed and the effects of key parameters on performance are discussed. The feasibility of the proposed system is further evaluated in terms of exergy and economy. The results demonstrate that the proposed SF-TES-CFPP (solar field, thermal energy storage system, coal-fired power plant) system exhibits the enhancement of peaking capability and flexible operation. In comparison with the conventional TES-CFPP, the integration of solar energy into the peaking process has enabled the SF-TES-CFPP system to enhance its peaking capacity by 20.60 MW while concurrently reducing the coal consumption rate by 10.26 g/kWh. The round-trip efficiency of the whole process of the system can be up to 85.43% through the reasonable heat distribution. In addition, the exergy loss of the principal components can be diminished and the exergy efficiency of the system can be augmented by selecting an appropriate main steam extraction mass and split ratio. The economic analysis demonstrates the dynamic payback period is 9.90 years with the net present value (NPV) across the entire life cycle reaching 1.069 02×10⁹ USD.

In this study, we perform a numerical investigation of a steady laminar stagnation flow flame stabilized at a wall with the consideration of heat transport, focusing on a lean hydrogen/air mixture with a fuel/air equivalence ratio 0.6. We discuss the NO emissions and their formation rates under various conditions, such as flow velocity and combustion pressure. It is found that the predominant reaction pathway for NO formation involves NNH radicals, though this changes near the wall surface. Beyond examining the wall’s influence on flame structures, the present work focuses on the impact of combustion process on materials. Specifically, the accumulation of atomic hydrogen at the wall surface is explored, which is significant for the consequent modeling of potential hydrogen embrittlement. Additionally, the growth rate of oxide layers on the material surface increases significantly if the combustion pressure and consequently the combustion temperatures are enhanced. These investigations offer valuable insights into how combustion processes affect material, which is useful for designing engineering components under high-temperature environments.

The impact of turbine guide vanes on a three-dome combustor’s lean blowout limit and blowout process was experimentally investigated. The parameters studied include the presence of the turbine guide vanes or not and the blockage ratio of turbine guide vanes. It is shown that the presence of turbine guide vanes and an increase in the blockage ratio increase the lean blowout fuel-to-air ratio. From the images of flame spontaneous emission captured by the high-speed camera, the coupling of the combustor with turbine guide vanes can alter the sequence of the blowout among the three domes, and localized tiny flame lumps have been observed to develop into larger flames during lean blowout. However, flames within the combustor are established independently near blowout, and no reignition is observed. Furthermore, the turbine guide vanes have been found to shorten the duration of the blowout process and enhance the likelihood of blowout by increasing the lean fuel-to-air ratio.

The modification with dark metallic oxide is identified as the crucial strategy to enhance optical absorptions of calcium-based materials for the direct solar-driven thermochemical energy storage. The effect of modification on the heat release behavior in carbonation of calcium-based material has been widely investigated, but its effect on the heat storage behavior in calcination is lacking of sufficient research, typically for low-cost calcium resource such as carbide slag. The Fe-modified and Mn-modified carbide slags for CaCO₃/CaO heat storage were synthesized and their optimum decomposition temperatures, effective heat storage conversions, heat flows and heat storage rates in endothermic stage were investigated. Although the Fe modification exacerbates the CaO sintering due to the formation of Ca₂Fe₂O₅, that is still effective in reducing the regeneration temperature of CaO in CaCO₃/CaO cycles. The Mn modification enhances significantly sintering resistance by forming the CaMnO₃ and its transformation into Ca₂MnO₄. The effective heat storage conversion of Mn-modified carbide slag after 30 cycles is 3.2 times as high as that of untreated carbide slag. Mn-modified carbide slag exhibits the lowest regeneration temperature and the highest heat storage rate after cycles. The loose and stable porous structure of Mn-modified carbide slag contributes to its superior endothermic performance. Therefore, Mn-modified carbide slag seems to be the potential candidate for calcium looping thermochemical heat storage.

The rapid expansion of data centers has significantly increased energy consumption, with cooling systems accounting for about 40% of total use. Utilizing natural ambient cooling sources provides a simple and effective approach to enhancing energy efficiency. Radiative cooling (RC), though an emerging solution that can considerably reduce energy use, faces challenges in data centers due to the complex, multi-level nature of cooling systems, requiring careful adaptation across different scales, which hinders its widespread adoption in data centers. In this study, we designed radiative coolers for data center cooling systems to enhance efficiency, and then proposed an RC system integrating these structures and analyzed its energy-saving performance. The cooling properties of a real radiative cooling film applied to the cooler surface were experimentally tested, and the data were used for the simulation analysis of the proposed coolers. Five different radiative cooler structures were designed and optimized, and we conducted a comprehensive multi-level performance analysis of the optimized structures, including operational parameters such as flow rate and temperature, as well as the impact of location, climate, and regional adaptability. Subsequently, a novel hybrid cooling system incorporating radiative coolers for data centers was proposed. Comparative studies across different climate zones in China demonstrated that this hybrid system delivers substantial energy savings compared to traditional vapor-compression systems. Results showed that in Beijing, Urumqi, and Guangzhou, the annual temperature difference between the inlet and outlet of the radiative cooler ranges from 2.40°C to 3.28°C, making it feasible for radiative cooling throughout the year in most parts of China. The annual Power Usage Effectiveness (PUE) in Beijing using the novel RC system is 1.19, with an increase in Energy Efficiency Ratio (EER) of 60.74%. This study may contribute to the development of green, energy-efficient cooling technologies for future data centers.

The green transition of power systems relies on the accurate measurement of the economic cost associated with the deep peak-shaving process in coal-fired power plants. To evaluate the variation in the coal consumption rate during low-load operation, a model of a 300 MW coal-fired unit was established, with less than 1% deviation from the actual operation value. The results indicate that the coal consumption rate at 20% load can increase to 1.48 times the full-load value. When the excess air coefficient is reduced by 0.3 at low-load conditions, between 40% and 20% load, the exhaust gas temperature is reduced by approximately 5°C, leading to a decrease in the coal consumption rate. In addition, elevating the steam temperature to the design value can reduce the coal consumption rate by 6% to 13%, and increase the inlet temperature of Selective Catalytic Reduction (SCR) process by 10°C. Improving the turbine efficiency during peak-shaving significantly reduces the coal consumption cost, and the enhancement of the mean steam temperature is an efficient approach. This study offers a theoretical reference for the retrofitting, design and economic operation of coal-fired units in peak-shaving, thereby supporting energy system transitions.

Vegetable oils and animal fats-sourced biodiesel are considered a promising alternative to conventional diesel fuel. However, they possess convinced restrictions like inadequate cold flow properties, poor lubricity, and complex emissions of nitrogen oxides (NO_x). However, various nano-additives have emerged to overcome those limitations and enhance the performance of biodiesel in diesel engines. The impact of different additives on diesel engine characteristics that have been conducted recently with the combination of biodiesel is thoroughly analyzed in this review paper. Additionally, to provide a thorough summary of experimental research done in this area, the article addresses the several kinds of additives that are frequently employed and their effects on engine performance, combustion, emissions, wear, and durability. The evaluation of nano-additives’ impacts in diesel-biodiesel engines highlights significant improvements in emissions, combustion efficiency, and engine durability. For example, the multi-walled carbon nanotubes (MWCNT) are found to increase Brake Thermal Efficiency (BTE) by up to 36.81%, while cerium oxide (CeO₂) can reduce Brake Specific Fuel Consumption (BSFC) by as much as 30%. Additionally, titanium dioxide (TiO₂) achieves a minimum NO_x reduction of 22.57%, and graphene nanoplatelets (GNPs) have produced a minimum 65% reduction in carbon monoxide (CO) emissions, albeit with higher hydrocarbons (HC) emissions. However, long-term engine durability studies are needed to assess the compatibility of nano-additives with engine components and their impact on engine longevity which could be the future research direction aiming to investigate new nanoparticle possibilities and reduce pollutants to maximize biodiesel performance.

Air source heat pump has insufficient heating performance under the low ambient temperature conditions;  meanwhile, the thermal storage device in heat pump system has a wide range of application. This study proposes a  thermal storage air source heat pump heating system (HSASHP) with a novel structure, and has established both the  mathematical models and simulation models of each component of the single-stage and the thermal storage air source heat  pump heating systems in MATLAB/Simulink respectively, with three operation modes proposed for the latter (i.e., the thermal storage air source heat pump heating system); by using the outdoor ambient temperature during the heating period in Baotou, China, the heating capacity of the two heat pump systems are simulated and the economy of both systems’ operation are investigated. The results show that within a 7-day heating period, the total heat production of the thermal storage heat pump unit and the single-stage heat pump unit is 442.58 kW·h and 355.68 kW·h, respectively, with HSASHP 24% higher; the average heating Coefficient of Performance (COP) of the two heat pump units is 2.11 and 1.51, respectively, with HSASHP 39.74% higher; the power consumption of the two heat pump units is 202.74 kW·h and 239.74 kW·h, respectively, with HSASHP 15.44% lower. These all illustrate the effectiveness of the new structure in improving the performance of heat pump units. However, the total power consumption and operational economy of both air source heat pump heating systems do not differ significantly.

Digital twin is a cutting-edge technology in the energy industry, capable of predicting real-time operation data for equipment performance monitoring and operational optimization. However, methods for calibrating and fusing digital twin prediction with limited in-situ measured data are still lacking, especially for equipment involving complicated multiphase flow and chemical reactions like coal-fired boilers. In this work, using coal-fired boiler water wall temperature monitoring as an example, we propose a digital twin approach that reconstructs the water wall temperature distribution with high spatial resolution in real time and calibrates the reconstruction using in-situ water wall temperature data. The digital twin is established using the gappy proper orthogonal decomposition (POD) reduced-order model by fusing CFD solutions and measured data. The reconstruction accuracy of the digital twin was initially validated. And then, the minimum number of measured data sampling points required for precise reconstruction was investigated. An improved uniform data collection method was subsequently developed. After that, the computational time required for the digital twin and the traditional CFD was compared. Finally, the reconstruction method was further validated by in-situ measured temperature from the in-service boiler. Results indicate that the established digital twin can precisely reconstruct the water wall temperature in real time. Thirty-nine sampling points are sufficient to reconstruct the temperature distribution with the original data collection method. The proposed uniform data collection method further reduces the mean relative errors to less than 0.4% across four test cases, and with the constrained technique, the errors decrease to 0.374% and 0.345% for Cases 1 and 3, which had poor reconstructions using the original sampling point arrangement. In addition, the reconstruction time of the digital twin is also considerably reduced compared to CFD. Engineering application indicates that the reconstructed temperatures are highly consistent with in-situ measured data. The established water wall temperature digital twin is beneficial for water wall tube overheating detection and operation optimization.

Non-Fourier heat conduction models are extended in response to heat transfer phenomena that cannot be accurately described by Fourier’s Law of heat conduction. This paper provides a review of heat conduction in functionally graded materials (FGMs) employing non-Fourier models. FGMs are designed materials with a gradual transition in composition, microstructure, or thermal conductivity throughout their volume. The spatial variation in thermal conductivity can lead to deviations from Fourier’s Law, resulting in non-Fourier heat conduction behavior in certain situations, such as at very short time scales or in materials with high thermal conductivity gradients. Researchers utilized various models, such as, Cattaneo-Vernotte, parabolic two-step model, hyperbolic two-step, phonon kinetic, dual-phase lag, and three-phase lag models to describe non-Fourier heat conduction phenomena. The objective of this review is to enhance the understanding of non-Fourier heat transfer in FGMs. As a result, the analytical studies conducted in this particular area receive a greater emphasis and focus. Various factors affecting non-Fourier heat conduction in FGMs including gradient function, material gradient index, initial conditions, boundary conditions, and type of non-Fourier model are investigated in various geometries. The literature reviews reveal that a significant portion of research efforts is centered around the utilization of dual phase lag and hyperbolic models in the field of non-Fourier heat conduction within FGMs. 

Traditional salt solutions, due to their susceptibility to crystallization and corrosion, can be replaced by ionic liquids (ILs) to enhance the effectiveness of liquid desiccant dehumidification systems. This study proposes integrating a transcritical-carbon-dioxide heat pump (TCHP) with an IL dehumidification cycle, thereby providing both cooling and heating for IL under large temperature differentials. Thermodynamic analysis is conducted to investigate the influence of key design parameters. The findings reveal that the TCHP is capable of handling the significant temperature rise during IL regeneration. The evaporation temperature is the key factor for matching the supply and demand of cooling and heating in the system. The self-circulation ratio of the solution is limited by the regeneration temperature. When the initial air humidity ratio is 8.0 g/kg and the supply air humidity ratio is 1.0 g/kg, the proposed system’s total heat COP is 31.9% higher than that of the reference systems.

Advancements in high-temperature heat pump technology are pivotal for achieving global carbon neutrality goals, with the working fluid’s heat transfer and flow properties being crucial for efficient condenser design. Nevertheless, research on high-temperature condensation of organic fluids is sparse, necessitating the development of accurate correlations for heat transfer and flow characteristics. This study emphasizes experimental research on R245fa’s condensation heat transfer and pressure drop within a 40°C–110°C saturation temperature range inside a plain tube with a 9-mm internal diameter. Sensitivity analysis highlighted the differences in condensation characteristics between high and low temperatures, and influencing mechanisms are revealed. Then, the measured data are employed to assess the accuracy of previous correlations. Based on the importance factor analysis result, adjustments are made to Reynolds number and flow regime boundaries. Finally, the correlations incorporating high temperature condensation of R245fa are developed, yielding a decrease in deviation from 17.6% to 7.23% for heat transfer and from 15.1% to 7.51% for frictional pressure drop gradient. Utilizing the newly developed models, 877 data points across 14 working fluids are predicted, results in a decrease in deviation from 18.85% to 10.65% for heat transfer coefficient, indicating a significant improvement in both accuracy and generality of the developed correlations.

Fourier heat conduction in functionally graded materials (FGMs) has attracted considerable scientific interest due to its simplicity in modeling. FGMs, characterized by a gradual variation in material composition and properties, exhibit unique thermal conductivity behaviors that differ from conventional homogeneous materials. Understanding and analyzing heat transfer in FGMs is crucial for optimizing their thermal performance in various applications. The analytical analysis of Fourier heat conduction in FGMs has facilitated a more profound understanding of the heat transfer phenomena that occur within these advanced materials. This paper provides a comprehensive overview of the research conducted on Fourier heat conduction in FGMs, highlighting the key methodologies, findings, and implications. The literature review showed that the thermal conductivity in FGMs varies spatially, affecting the temperature distribution and heat flux within the material. The gradual variation in material properties in FGMs necessitates the development of specialized analytical solutions to accurately describe the heat transfer behavior. Additionally, the choice of appropriate analytical functions has been found to significantly impact the accuracy and efficiency of the analytical solutions. Researchers have explored various functions, including power functions, exponential functions, and polynomial functions, to represent the temperature distribution within FGMs. It has been observed that the choice of these functions should be based on compatibility with the analytical solution of the heat conduction equation, ensuring accurate predictions of temperature profiles and heat transfer rates.

To address the complex spatiotemporal characteristics of impeller axial clearance leakage flow in a liquid-ring vacuum pump, plasma actuation with radial centripetal, circumferential reverse, and counter discharge layout types was designed to control the leakage flow. The regulation effects and interference mechanisms of plasma actuation on clearance leakage flow were explored. The results show that under plasma flow control of the three layout types, the vacuum degree of the pump changes not obviously, but the shaft power is reduced and the efficiency is improved to a certain extent. Among them, the circumferential reverse has a more obvious control effect on the hydraulic performance of the pump and has more advantages in controlling the medium- and high-intensity leakage flow in the compression zone, while the radial centripetal has a more effective control effect on the low-intensity leakage flow in the transition zone. All three layout types of plasma actuation can effectively weaken the medium-intensity leakage flow near the beginning of the compression zone, but their suppression effect on the high-intensity leakage flow near the end of the compression zone is weak. Due to the weak leakage in the transition region, the plasma actuation induced airflow and low-intensity leakage flow are coupled with each other, which will further aggravate the complexity and variability of the flow in the clearance. For unsteady clearance leakage flow, the circumferential reverse has a more stable control effect. About the control of medium-intensity leakage flow, the radial centripetal plasma actuation effect is better than the circumferential reverse. The research results can provide theoretical and methodological references for the performance optimization of liquid-ring vacuum pumps.

Latent heat storage technology plays a critical role in storing and utilizing geothermal energy. By combining cascaded phase change materials (PCM) with mine filling technologies, mine geothermal energy can be stored thermally more effectively. Therefore, this paper designed a physical model of double casing cascaded latent heat storage (CLHS) system in mine. Paraffin RT28 and RT35 were encapsulated in annular gap 1 and annular gap 2, respectively, and this backfill mode was defined as Case 1. The scheme whose backfill sequences of the two PCM were exchanged is defined as Case 2. The heat transfer process of backfill body and PCM was simulated and analyzed by using FLUENT software, and compared with the single stage latent heat storage process. The temperature, liquid fraction (LF), heat transfer capacity, and heat transfer rate were used to evaluate the thermal properties of the CLHS process. It was necessary to study the effect of the filling sequence of PCMs on the heat storage and release process of the backfill body using these results as a starting point. The results show that the main factor affecting latent heat storage in cascaded system is the heat transfer of surrounding rock. Compared with the single-stage heat storage process, the heat storage time of cascaded heat storage process is reduced by 73 min, which is significantly decreased by 20.9%. Moreover, the whole liquid phase fraction (β) of the single-stage has little change during the heat release, while the PCM of the cascaded heat release process can fully release the latent heat. In terms of layout order of PCM, compared with Case 1, the latent heat storage time of Case 2 is increased by about 40 min, and the heat release rate (ε_s) is significantly lower than that of Case 1. In the initial heat release stage, the heat release rate of Case 2 reaches 95.6 W, which is 30.6% lower than that of Case 1. In comparison, the heat storage and release effect of Case 1 is better than that of Case 2. This paper provides a reference for the improvement of heat storage and release rate of the backfill coupled cascaded latent heat storage system (BCCLHS).

The present work aims to provide preliminary support and research foundation for developing integrated technology of CO₂ utilization and tar-rich coal pyrolysis to produce high-value chemicals and fuels. The chemical properties of tar produced by tar-rich coal pyrolysis under traditional N₂ and N₂/CO₂ atmospheres were investigated in a fixed-bed reactor at different temperatures (600°C–800°C) and atmospheric pressures. The results showed that tar-rich coal pyrolysis under CO₂ atmosphere can promote tar production (mass fraction 8.42% increased) compared with that of traditional pyrolysis (under N₂), with the maximum value up to 21.26% (in weight). It should be noted that the generation of coal tar and CO small molecule gas can be promoted by increasing the concentrations of CO₂ in pyrolysis atmosphere gases. GC-MS and simulated distillation results showed that the CO₂ atmosphere can promote the production of light oil components such as phenols, alcohols, and olefins, while inhibiting the production of heavy components such as asphalt simultaneously. Elemental analysis results showed the H/C ratio of coal tar increased under CO₂ atmosphere indicating that the high quality of coal tar is improved, which is consistent with that of simulated distillation and GC-MS test. Finally, a possible reaction pathway of tar-rich coal under CO₂ atmosphere pyrolysis is also proposed.

Upstream blade wake turbulence fluctuation may affect compressor blade forced response caused by wake sweeping. In order to investigate the effect of wake turbulence fluctuation and predict the blade vibration more accurately, this paper proposes a forced response calculation model that considers the excitation of upstream blade wake turbulence fluctuation on the basis of the conventional forced response calculation method. Using a three-stage axial compressor as the research subject, a quasi-three-dimensional large eddy simulation is conducted using the blade profile at 77.8% of the span of the inlet guide vane. Analysis of the flow field around the inlet guide vane indicates noticeable total pressure fluctuation in the wake of the inlet guide vane. The influence of upstream wake turbulence fluctuation is incorporated into the forced response calculation model in the form of total pressure fluctuation to obtain more accurate excitation forces. Specifically, the relationship between the amplitude of total pressure fluctuation and total pressure loss is established according to the results of large eddy simulation, and different formulas are set according to the position zoning of suction surface and pressure surface. Computational results show that, if only wake sweeping is considered, the maximum amplitude is 27% lower than the test result. However, when wake sweeping and wake fluctuation are considered, the calculated result better matches the test result, with only a 6% reduction compared to the test result. The results confirm the effectiveness of the proposed model.

In addressing the challenges of solid waste disposal, this study proposed to utilize electrolytic manganese residue to produce building insulation materials. The research focused on the factors such as precursor material ratio, alkali activator ratio, foaming agent and foam stabilizer on the target insulation materials properties. The findings indicated that SiO₂/Al₂O₃ molar ratio, SiO₂/Na₂O molar ratio, and liquid/solid mass ratio impact the mechanical properties of the samples. The best mechanical performance of building structural material samples was characterized by a compressive strength of 11.15 MPa and a density of 1476 kg/m³. The optimal properties for building insulation materials were a thermal conductivity of 0.131‒0.104 W/(m·K), compressive strength of 1.49‒0.69 MPa, and density of 533‒433 kg/m³, with a cost of 1722‒1294 CNY/m³. This research provides a new approach for large-scale electrolytic manganese residue utilization while enhancing insulation performance and reducing energy consumption in buildings, with promising prospects for further engineering development.

The inferior flammability of coal gasification fine slag (CGFS) from entrained-flow gasifiers hampers its resourceful utilization. However, the reasons behind its poor flammability still need to be investigated. This paper conducted a comparative study on the combustion characteristics of three CGFS samples: CGFS_GSP, CGFS_SN, and CGFS_OMB (subscripts GSP, SN, and OMB representing different gasification processes), using experimental techniques such as TG/DTG and combustion kinetic model fitting methods. Additionally, a comprehensive investigation into the physicochemical properties of CGFS was conducted. The objective was to elucidate the causes behind the poor flammability of CGFS. The results revealed that CGFS exhibits lower volatile matter content and higher activation energy than their corresponding raw coal (RC), leading to a significantly higher ignition temperature. The ignition temperatures of RC1, RC2, and RC3 are 361.82°C, 378.66°C, and 404.99°C, respectively. In contrast, the ignition temperatures of CGFS_GSP, CGFS_SN, and CGFS_OMB are 549.08°C, 566.58°C, and 532.67°C, respectively. During the combustion reaction, the temperature (T_max) at which CGFS reaches its maximum weight loss rate is significantly higher than the temperature (T_maxIII) at which fixed carbon in raw coal reaches its maximum weight loss rate. The T_maxIII of RC1, RC2, and RC3 are 450.90°C, 457.19°C, and 452.77°C, respectively. In contrast, the T_max of CGFS_GSP, CGFS_SN, and CGFS_OMB are 583.55°C, 608.20°C, and 582.18°C, respectively. The maximum weight loss rate of different types of CGFS is also significantly lower than the fixed carbon combustion maximum weight loss rate of their respective raw coal samples. The physicochemical characterization results of CGFS demonstrate that, compared to the corresponding raw coal, there is a significant reduction in the proportion of active sites in CGFS. Simultaneously, the proportion of C-C/C-H on the surface of residual carbon in CGFS decreases. In contrast, the proportion of O=C-O significantly increases, suggesting a shift toward a more stable state of carbon-containing functional groups. This study is expected to offer essential theoretical support for the efficient combustion utilization of CGFS.

In this paper, a new multi-generation system, incorporating solid oxide fuel cell (SOFC), gas turbine (GT), lithium bromide chiller, gas and heat storage components is proposed to address the issues of volatility in user load and energy source input and mismatching between supply and demand. The dynamic model and control strategy of the system are established, and the system dynamic characteristics in response to solar DNI and external load disturbances are studied. The system can rapidly adjust the key output and input parameters to realize a new supply-demand balance in a shorter period of time by multiple PID control methods. The response processes of two combined cooling, heating and power (CCHP) systems with and without gas storage to cope with load changes are compared. The results show that the CCHP system with gas storage can effectively shorten the response time of load following. The solar collector and the SOFC-GT can reach a new equilibrium within a few tens of seconds under the controller. The response time of the methanol reactor is longer compared to those of solar collector and the SOFC-GT, taking several minutes to stabilize. When the cooling and heating load change, the system can adjust the output to the demand value within 500 and 260 seconds.

Cold sintering as a new technology for the fabrication of ceramic composites could overcome the shortcomings of traditional high temperature sintering approach and achieve dense structure in the composite at a relatively low temperature (<200°C). In this work, a shape stabilization phase change composite is fabricated and investigated by dint of such new fabrication approach, in which a mixed nitrate salt of NaNO₃-KNO₃ is used as phase change material and magnesia powder is acted as structure skeleton. Using of deionized water as sintering additive, the effects of sintering agent content, sintering temperature, uniaxial pressure and time on the composite microstructure characteristics and macroscopic properties are evaluated. The results show that the liquid salt could be effectively accommodated in the magnesia skeleton, forming a dense and stable structure in the composite. There is existence of optimal cold sintering parameters at which a benign combination of mechanical strength and thermal cycling performance could be attained in the composite. Under the sintering temperature of 150°C, duration time of 8 min, uniaxial pressure of 150 MPa, and water mass content of 7%, the fabricated composite exhibits a heat storage density of 610 kJ/kg at its potential utilization temperature range of 30°C–580°C and a compressive strength over 240 MPa with a dense density higher than 98%, demonstrating that it can be a viable alternative used in thermal energy storage domains.

This paper investigates the film cooling characteristics and flow structure of trailing edge cutback in turbine vanes, and explains the unsteady flow mixing mechanism of this cooling structure using Proper Orthogonal Decomposition (POD) method. The Delayed Detached Eddy Simulation (DDES) turbulence model was used to obtain detailed information about the velocity and temperature field for the POD method. To verify the accuracy of the numerical results, fast-response Pressure Sensitive Paint (PSP) and high-frequency Particle Image Velocimetry (PIV) experiments were also conducted, and the results achieved good agreement. As the blowing ratio increases, the effectiveness η of the cutback’s film cooling exhibits a “increase-decrease-increase” trend, with η reaching its minimum point at around a blowing ratio (M_slot) of 0.75. Three kinds of coherent vortex structures are observed in the flow field at different blowing ratios. According to the analysis using the POD method, the first and second order modes of a Karman-like vortex street are observed in the vicinity of the wall at various blowing ratios. This coherent flow structure is directly related to the mixing intensity between the mainstream gas and the coolant. At M_slot=0.75, these modes had the highest energy ratio and formed a stable dominant coherent structure in the flow field. As the blowing ratio increases, the main characteristic modes in the temperature field gradually change, and the mode appears crescent-shaped when the effectiveness of film cooling is at its lowest. This paper combines the vortex structure of the flow field to explain the flow field feature distribution at the lowest effectiveness point η and analyzes its impact on the film cooling characteristics of the protected surface.

The mined-out areas formed by ore extraction have promoted the development of seasonal energy storage technology in underground spaces. Currently, most studies on the heat storage/release performance of backfills with embedded heat exchange pipes have idealized the operating conditions, such as constant fluid inlet temperature and flow rate. However, actual operating conditions are influenced by many factors like weather conditions, surface equipment, and heat load fluctuations, making them unstable. Therefore, this paper constructs a solar-assisted heat pump coupled mine backfill body heat storage system (SAHP-MBBHSs) based on TRNSYS simulation software and verifies the accuracy of the backfill heat exchangers (BFHEs) model through experiments. Considering the influence of various external factors on the operating conditions, we investigated the long-term seasonal heat storage/release performance of the BFHEs, focusing on the effects of solar collector area, U-tube spacing, thermal conductivity of backfill materials, and heat storage start/stop time. The results show that reducing the U-tube spacing increases the fluctuation amplitude of the average temperature of the backfill body, with the maximum average fluctuation amplitude difference reaching 16.6°C between the 11th and 15th years. Delaying the onset of thermal storage reduces the storage effectiveness of the U-BFHEs, while increasing the heat release effectiveness. During the thermal storage/release interval, heat loss to the surrounding rock does not exceed 4.7%, with the minimal overall impact. The thermal conductivity of the backfill body has the greatest effect on the heat transfer effectiveness of U-BFHEs, increasing from 1 W·m^–1·K^–1 to 2 W·m^–1·K^–1 resulting in respective increases of 58.8% and 39.2% in the heat transfer effectiveness during the 15th year of thermal storage/release. The total heat storage-release effectiveness of the U-BFHEs does not exceed 43.7%, indicating significant room for improvement. Utilizing seasonal thermal storage in the backfill body can effectively enhance the heating performance of SAHP-MBBHSs, with the maximum average APF and HSPF values reaching 3.85 and 5.43, respectively, during the 11th–15th years of operation, maintaining high efficiency even after long-term operation.

This work focuses on evaluating the performance of a 660 MW ultra-supercritical power plant from the perspective of energy saving ability. By conducting the exergy analysis, the exergy loss distribution and the efficiency of regenerators are thoroughly measured. The results show that the exergy loss of a high-pressure regenerative heater can be as high as 3.03 MW. Thus, installing outer steam coolers can reduce the exergy loss of high-pressure regenerative heaters. The energy saving potential of different configurations across wide load conditions is further analyzed. These analyses reveal that the flue gas waste heat utilization configurations not only alter the exergy loss distribution in the regenerative heating system but also reduce the need for high-grade extraction steam, thereby enhancing the unit’s power generation capacity. Based on the proposed optimal configuration, the gas-water heaters with high-temperature and low-temperature heat sources are utilized to heat the corresponding feed water, enabling a cascade utilization of waste heat. This approach minimizes the standard coal consumption for power generation of the unit to 253.39 g·(kW·h)^–1, 1.27% lower than the reference unit. Under rated conditions, the power generation increases by 5.99 MW. Under 40% THA condition, this configuration exhibits significant energy-saving benefits with a 0.97% reduction in coal consumption rate. Furthermore, the study has delved into the impact of turbine degradation, which is found to adversely affect the thermal performance of the power unit. This revelation provides crucial insights into maintaining and optimizing the performance of the thermal system.

In response to the challenges posed by the transformation of China’s reed industry, leading to difficulties in reed utilization, and the significant increment in raw soil from the expansion of urban infrastructure, the authors proposed a novel method of coupling reed with raw soil to produce an ecological building insulation material. The aim is to enhance the thermal comfort of rural buildings and achieve building energy saving. The research has applied theoretical and experimental methods as the core means of exploration for key factors in the preparation of the novel ecological insulation material. These factors include raw soil content and curing methods. Key performance indicators such as thermal insulation, mechanical properties, fire resistance, water resistance, moisture resistance, and acoustic performance have been utilized for evaluation. The research results indicate that the proposed process and method for the preparation of the ecological insulation material effectively utilize reed and raw soil, achieving excellent multi-target performance. When the content of raw soil is in the range of 0–40%, the material’s thermal conductivity ranges from 0.097 W/(m·K) to 0.104 W/(m·K), compressive strength from 0.70 MPa to 0.79 MPa, water absorption rate from 29.42% to 38.95%, moisture absorption rate from 13.33% to 31.48%, and the maximum sound absorption coefficient is 0.80, with a maximum sound insulation of 56.66 dB. Additionally, a non-combustible A-grade fire resistance was achieved. To expand the application space and scope of the novel material, the research team further explored on-site construction material preparation processes and conducted experimental research, focusing on the key aspect of the “curing process”. The low temperature curing method of industrial heating blanket was proposed. The research results indicated that the method is feasible. At an environmental temperature of 25°C, with different curing times and curing temperatures, the material’s thermal conductivity ranges from 0.089 W/(m·K) to 0.109 W/(m·K), and the compressive strength is between 0.14 MPa and 0.70 MPa, meeting the relevant parameter requirements. This research opens up avenues for other types of biomass with high economic added value applications and can be directly applied to improving the thermal environment of residential buildings, contributing to building energy saving, rural revitalization, and the implementation of dual-carbon strategies in China.

The paper utilizes a combination of entropy production theory and numerical simulation to analyze the energy dissipation of Francis turbines. The distribution law of local entropy production rate (LEPR) in various components of hydraulic turbines is explored under different operating conditions. A detailed examination of hydraulic losses within the Francis turbine reveals that the primary contributors are the runner and draft tube, with comparatively smaller losses occurring in the spiral casing and guide vane areas. The study further explores the formation reasons behind these losses. Within the runner area, the LEPR mainly concentrates in the inlet area of the blade channel, as well as the pressure and suction surfaces of the runner blades. The main reason for hydraulic losses in the runner area is the movement of vortex structures in the blade channel. Within the draft tube area, the hydraulic losses mainly occur on the walls of the straight cone section and the elbow section. There is a backflow phenomenon in the draft tube, which is the main reason for hydraulic losses in the draft tube area. This article can provide a certain theoretical reference for exploring the influencing factors of hydraulic losses in hydraulic turbines.

The improvement of composite phase change materials in energy storage density and thermal conductivity is significant for the efficient use of energy. This study proposed novel composite materials based on forsterite with high specific heat as matrix materials, chloride salts (NaCl-KCl) with high latent heat as phase change materials and SiO₂ nanoparticles as fillers. The results indicated that forsterite and chloride salts exhibited excellent chemical compatibility, and the composite materials containing 40% (in weight) chloride salts achieved an energy storage density of 882.5 J/g within the range of 100°C to 800°C, a latent heat of 108.1 J/g, and a thermal conductivity of 0.68–0.81 W/(m·K) at 300°C–500°C. Furthermore, the addition of SiO₂ enhanced the thermal conductivity and energy storage density of composite materials due to the formation of unique nanostructures. More importantly, the removal of structural water during heat-treatment process resulted in the formation of micropores and increased specific surface area of forsterite particles, which facilitated the adsorption and stabilization of molten chloride salts. Combined with the stabilization effect of forsterite and synergistic effect of SiO₂ nanoparticles, the obtained composite materials with 2.0% (in weight) SiO₂ nanoparticles exhibited good thermal stability with 1.80% weight loss and 2.34% reduction in latent heat after 150 cycles, indicating a promising application in high-temperature thermal energy storage.

In this study, a three-dimensional numerical investigation was conducted on the front and rear fans of a three-bypass variable cycle engine under various speeds and internal bypass conditions. The impact of internal bypass conditions and speeds on the matching characteristics of the front and rear fans, as well as the factors limiting the variation of bypass ratio, are summarized. The findings reveal that for near stall, design point, and near choke internal bypass conditions, the operating point of the front fan tends to move towards near-stall while that of the rear fan moves towards near-choke when increasing external bypass back pressure. At design speed, external bypass blockage is identified as a limiting factor for increasing the bypass ratio at the internal bypass design point. Additionally, blockage caused by a significant amount of low-energy fluid at the suction surface of the rear fan stator leads to rear fan stall which limits further increase in bypass ratio at external bypass near stall condition. Similarly, leakage flow overflow passage at the top section of first stage rotor blade in front fan results in front fan stall, which restricts decrease in bypass ratio at internal bypass near stall condition. As corrected speed decreases, there is an upper-left shift observed in the curve depicting variation in relative back pressure with respect to change in bypass ratio due to the phenomenon “pre-surge and post-choke”. This indicates increased air flow into external bypass resulting in higher values for lower speeds. Furthermore, limitation on further increase in bypass ratio at external bypass near stall condition with decreasing speed can be attributed to transition from rear fan stall to external bypass blockage.

As one of the hottest components of gas turbine, the blade tip is difficult to be cooled down for the complexity flow field in the tight tip clearance. The blade tip protection requires advanced tip structures. To develop new structures, the effect of ribs on blade squealer tip aerothermal performance and cooling performance were investigated. Ribbed squealers tips (1R, 2R and 3R, compared to the Basic case) were designed and their cooling ability under five coolant blowing ratios (M) were measured by the Pressure Sensitive Paint (PSP) technique, taking film cooling effectiveness (η) as the criterion. Numerical method was validated and then was adopted to analyze the flow field and aerodynamic loss in the tip gap. The results indicated that the cooling coverage and η increase with M for sufficient coolant supply. Compared to the Basic case, the η on the middle section is higher while that on the trailing part is lower for the ribbed squealer tips. The flow field analysis showed that the coolant flows downstream to the trailing edge in the Basic case, bringing additional cooling protect to the downstream region. The ribs induce vortices behind them to involve the local and upstream coolant and prevent upstream coolant from flowing down, leading to the improvement in the local and the degradation in the downstream for the film cooling performance. The aerodynamic results pointed out that the ribbed squealer tips are superior to the Basic case in terms of the aerodynamic performance, even though the tip leakage mass flow of these cases are larger than that of the Basic case. The maximum reduction on pressure loss coefficient is 16.2% for the ribbed squealer tip.

Waste plastics, with their high hydrogen-to-carbon (H/C) atomic ratios, can act as hydrogen donors during coal pyrolysis, thereby enhancing tar yield and quality. Thus far, a study has been conducted on the co-pyrolysis characteristics of coal and waste plastic, along with a rapid prediction method for tar yield. An experimental system for the co-pyrolysis of coal and waste plastic is established to examine the distribution patterns of pyrolysis products, such as gas, tar, and char, at varying temperatures and coal-to-waste plastic ratios. The results indicate a significant synergistic effect during the co-pyrolysis of coal and plastic waste. As the blending ratio of waste plastic increases, the tar yield also increases, with the value of the synergistic effect parameter initially rising and then falling. As the blending ratio continues to increase, the formation of a liquid phase becomes more prevalent on the surface of coal particles during the pyrolysis process, which inhibits tar release and leads to a gradual decrease in the positive synergistic effect of the waste plastic on tar yield. Based on these findings, a rapid prediction model for tar yield has been developed using neural networks and optimized with a Genetic Algorithm (GA) and Particle Swarm Optimization (PSO), achieving a 10.52% reduction in the average prediction error under training conditions. The proposed model is utilized to predict the tar yield for new conditions in the database, with the relative error generally maintained within (–20%, 30%), demonstrating good accuracy and utility.

In this study, a full smoothed Blended Blade and End Wall (BBEW) design method for axial fan blade is proposed, overcoming the limitations of traditional BBEW design methods which can only control dihedral angles in planar cascade using straight-line adjustments. Then the effect and mechanism of BBEW technique on Rotor 67 have been studied using a design of experiments (DoE) population. Key parameters that affect the effect of BBEW techniques, including the maximum blended position and the maximum blended scale, are extracted through DoE population. The results show that nearly all blended designs in suction side realize the aerodynamic improvement of overall performance at different rotation speeds. Specifically, the peak efficiency is improved by 0.46% at design condition. From the perspective of flow details, through the radial migration of low-energy flow from corner region to mainstream by radial blade force, the area of corner separation is significantly decreased and its topology is simplified.

The junction film cooling has been proposed to deal with the situation of insufficient film cooling performance under limited coolants. Numerical investigations are performed for baseline case and four junction film hole cases (3_junction, 4_junction, 5_junction and 6_junction cases) at the coolant mass flow rate varying from 0.0016 kg/s to 0.0064 kg/s. From the results, due to the expanded film hole exit and the interactions between branch film jets, junction film hole cases can suppress the “injection phenomenon” of film jet and the “entrainment effect” of mainstream, thus to improve film cooling performance, especially the film spanwise coverage. By comparison, under low coolant mass flow rate, the 5_junction case can generate the most obvious film cooling performance improvement. To be specific, at the coolant mass flow rate of 0.0016 kg/s, it achieves 76.92% improvement in area-averaged adiabatic film cooling effectiveness, and at the coolant mass flow rate of 0.0032 kg/s, the improvement is up to 703.85%. Through flow loss analysis, the results show that at low coolant mass flow rate, the junction film hole cases improve film cooling performance and pay a little cost of pressure loss; but under high coolant mass flow rate, they can improve film cooling performance and reduce total pressure loss concurrently. Among them, the 5_junction case generates the lowest total pressure loss coefficient; corresponding to the coolant mass flow rate of 0.0048 kg/s and 0.0064 kg/s, it decreases by 15.90% and 41.58% respectively. Through this study, the junction film cooling for improving cooling performance is provided, which is conducive to further raising turbine intake temperature, thereby improving the kinetic and thermodynamic properties of gas turbines.

The effect of different fuel mixtures (C₂H₂, C₃H₆, C₃H₈, C₂H₂+C₃H₆, C₂H₂+C₃H₈) on the acceleration of the gas detonation flame under the same detonation tube gun structure has been studied using numerical simulation. The trends of the internal parameters of the gun, as well as the variations of the gas flow velocity, temperature and pressure at the gun outlet with time were analyzed. At equivalence ratio of 1, the simulation results demonstrate that acetylene fuel produces the shortest detonation time and reaches the highest average gas flow velocity of 1031.6 m/s at the gun exit, and the acetylene detonation reaches the highest average temperature of 2750.6 K. The fastest speeds of OH and other parameters were produced by the detonation of C₂H₂ and its mixture fuels, which represents the fastest flame propagation. Propane detonation at the outlet of the gun to reach the maximum pressure of 0.66 MPa; internal to the gun, detonation of CO₂ produced by the majority of the distribution of the wall region. Different fuel compositions lead to variations in the detonation spray effects, and altering the fuel composition can meet diverse requirements for detonation and spray particle characteristics.

Flame propagation speeds are reported for ammonia/hydrogen/air mixtures with equivalence ratios in the range of 0.5–1.5, preheated gas temperatures ranging from 298 K to 673 K and hydrogen volume fractions of 0%, 20%, and 50%. The measurements were conducted using a Bunsen burner and an optical schlieren system. The results show that the flame propagation speed and combustion stabilities of the premixed gases increase with increasing preheating temperature. The combustion stability is significantly improved under the 20% hydrogen volume fraction condition. For the NH₃/H₂ mixtures with a hydrogen volume fraction of 50%, the flame propagation speed at 673 K with a stoichiometric ratio is approximately 4.85 times that at 298 K. The experimental results show that at 673 K, the flame propagation speed of the NH₃/H₂/air mixture increases by 7.8 times when the hydrogen volume fraction increases from 20% to 80%. The numerical results predicted with the Mei, Shrestha, and Stagni mechanisms are compared with the experimental data. The mechanisms proposed by Shrestha and Stagni overestimate the flame propagation speed, especially at high preheating temperatures. The results predicted with the Mei mechanism are consistent with the available data. The concentrations of OH, H, O and NH₂ are increased by the hydrogen addition; thus, the ammonia consumption is accelerated.

The complex three-dimensional flow within the last turbine stage under low-load condition intensifies internal flow instabilities, decreasing turbine efficiency and operational reliability. In this paper, to investigate the flow instability characteristic of air turbine used in Compressed Air Energy Storage (CAES) systems, three-dimensional unsteady numerical simulations are conducted on two-stage axial flow turbines, namely a small-scale turbine (AT-S) and a large-scale turbine (AT-L). Two low-load conditions of AT-S with a radial inlet chamber (RIC) were firstly analyzed. At the lowest relative mass flow (m_rel) of 0.18, no rotating instability (RI) and rotating stall (RS) phenomena were observed in AT-S, which features an aspect ratio of 2.4 for the last-stage rotor blades (R2). However, vortex instability was observed in the RIC, and it was not related to the occurrence of RI or RS. Thus, analysis on four low-load conditions of AT-L without RIC was conducted, where the R2 aspect ratio is 5.4. When m_rel was reduced to 0.28, RI occurred. As m_rel furtherly decreased to 0.18, RS occurred. The RI and RS phenomena were accompanied by disturbance clusters appearing at the blades top. Different flow modes were observed in RI and RS, which features with different combinations of Through-flow mode (TM), Choke mode (CM), and Separation mode (SM). This study not only considers the influence of the RIC, but also the factors of blade length on flow instabilities of CAES turbine.

This study delves into the theoretical exploration of the effects of injector and orifice arrangement, spray angle, and orifice size on combustion and emission characteristics of horizontal opposed two-stroke engines. By employing numerical simulations, the research systematically investigates how variations in these parameters influence engine performance and emissions. The findings underscore the significance of injector and orifice configuration in optimizing fuel spatial mixing and atomization, resulting in improved indicated thermal efficiency and indicated mean effective pressure. However, it is noted that while emissions of HC, Soot, and CO can be maintained at low levels by injector and orifice configuration, NO_x emissions tend to be relatively higher. Moreover, the study highlights the impact of spray angle on combustion dynamics, where an optimum spray angle is identified for achieving peak thermal efficiency and effective pressure due to the improvement between spray distribution and impingement. Additionally, the study reveals the critical role of nozzle diameter in combustion and emissions control, with an optimal diameter leading to enhanced thermal efficiency and reduced emissions of Soot, HC, CO, and CO₂ to some extent. Overall, these findings offer valuable insights into optimizing engine performance and emissions control strategies in horizontal opposed two-stroke engines, guiding future research and development efforts in the field.