To address the thermal protection requirements of scramjets operating at high Mach numbers (Ma > 8), this study proposes a novel composite double triangular regenerative cooling system. Innovatively, the system employs both supercritical CO2 and supercritical n-decane as coolants. Supercritical n-decane serves both as a coolant and fuel, while supercritical CO2 significantly enhances cooling efficiency due to its excellent thermophysical properties. Under a high heat flux condition of 3 MW/m(2), the system exhibits exceptional temperature control capability. Numerical simulation is conducted using the SST k-omega turbulence model to evaluate the effects of geometric dimensions, flow patterns, and channel materials on thermal-hydraulic performance. The spacing (d) of adjacent channels has an optimal value, and an excessively large or small value leads to decreased cooling efficiency. At d/H = 0.3 (H height of fluid domain), the system achieves the best cooling performance, with the Nusselt number (Nu) and overall thermal performance factor (eta) reaching the values of 363.82 and 1.20, respectively. Counter-current flow improved temperature uniformity, compared to co-current flow, reducing the temperature difference by 45.8 %. The channel material significantly affects cooling performance. Due to the high thermal conductivity of copper, the maximum wall temperatures of its channel are 3.7 % and 2.9 % lower than those of the steel channel and GH4169 channel, respectively.

The application of the rotation mechanism promotes heat exchange in the phase-change energy storage (PCES) process and improves the temperature non-uniformity at the end. This research proposes a novel type of subzone rotation condition, where different rotational speeds and rotation directions are applied to distinct phase transition regions, and it is implemented in the triple-tube heat storage process. An experimental system is constructed to monitor the temperature of PCM inside the PCES unit connected to the motor for rotation. Cross-comparisons are made with numerical process of PCES under the application of rotation conditions to verify its accuracy. The effect of constant and fluctuating heat sources on this PCES under different subzone rotation conditions is also considered. The comparison results indicate that the fluctuating heat source on overall melting behavior can be ignored, while the subzone rotation condition can improve the negative effect of the difficult-to-melt area. After applying a subzone rotational speed of 0.2 rpm, compared with static energy storage process, the mean PCES rate increased by 299.43 %, while the required time for heat storage completion is reduced by 74.73 %. The novel active enhanced heat exchange method proposed in the research is conducive to the further development of PCES technology.

Condensation heat transfer is a highly efficient heat transfer method. To further enhance the heat transfer coefficient, this study proposes a method utilizing an actively adjustable electric field. The research employs a mesoscopic-scale pseudopotential model coupled with a leaky dielectric model. Four strategies were compared to evaluate their enhancement effects on condensation, including no electric field, horizontal placed electric field, vertical placed electric field, and exchanging electric field. The study subsequently explored the effects of exchanging time, conductivity ratio, permittivity ratio, and electric capillary number on condensation heat transfer. Results indicate that the strategy of exchanging the electric field direction yields the optimal enhancement, reducing the condensation cycle by 21.51% and increasing overall efficiency by 19.51%. An optimal exchanging time was identified when the droplet diameter reached 45 lattices. Furthermore, by determining the optimal electric field intensity exchanging strategies under varying conductivity and permittivity ratios, the condensation heat transfer efficiency was further optimized by 27.44%.

Thermal energy storage(TES) devices are critical for efficient energy utilization and stable supply in building-integrated solar energy systems. Previous studies on rotation-driven TES devices have overlooked the trade-off between energy consumption and heat storage performance. Numerical simulations were conducted in this study to systematically explore finned paraffin-based thermal energy storage devices. Key thermal performance parameters, including thermal charging behavior, temperature distribution, flow field characteristics, heat storage capacity, heat storage efficiency, and energy consumption, were analyzed to evaluate the impact of rotation on/off switching moments. Results indicate that rotation-driven enhancement significantly shortens the charging time of vertical finned thermal energy storage tubes, with the benefits of this enhancement most pronounced in the late melting stage. The "first fixed then rotated" strategy (activating rotation at a liquid fraction of approximately 0.6) outperforms continuous rotation: compared with continuously rotating vertical finned thermal storage tubes, this strategy increases the benefits of reduced melting time, improved melting rate, and enhanced temperature response by 40.47%, 43.52%, and 36.98% per unit energy consumption, respectively. This study fills the existing research gap in dynamic rotation control for finned PCM storage devices. It provides a theoretical basis and technical support for optimizing finned thermal energy storage units in building solar systems, thereby promoting higher energy efficiency and operational stability of such systems.

Active regenerative cooling technology is well-suited for extreme operating conditions characterized by high temperatures and intense thermal loads, serving as a highly effective approach for reducing combustion chamber wall temperatures. Large Eddy Simulation (LES) is employed to investigate the thermo-hydraulic characteristics of supercritical n-decane in a jet-regeneration cooling channel with the pin fin, focusing on the critical yet underexplored effects of pin fin-jet spatial configurations. The results indicate that the fluid flow within the jetregeneration cooling channel gradually evolves towards a quasi-steady state, accompanied by the breakdown process of large-scale vortex structures into small-scale turbulence. The introduction of the pin fin significantly enhances the distribution stability of the thermophysical properties of supercritical n-decane, facilitating uniform temperature field transfer and thereby boosting the overall heat transfer efficiency of the channel. Compared to the pin fin placement schemes in front of and directly below the jet, positioning the pin fin behind the jet effectively leverages the high turbulence intensity in the jet wake region, achieving an optimal balance between heat transfer enhancement and flow resistance suppression. Compared to the flat channel, this configuration leads to an average increase of 3.29 % in the Nusselt number (Nu) throughout 0-1.8 s, with an instantaneous maximum enhancement of 32.6 %. The Thermal-Hydraulic Performance Factor (HTPF) is notably superior to the benchmark value of unity, underscoring its comprehensive performance advantages.

Heat transfer in heterogeneous anisotropic composites is governed not only by effective thermal conductivity, but also by the organization of local heat flux pathways. In yarn-reinforced ceramic matrix composites (CMCs), high-conductivity yarns can redistribute conductive transport between the yarn and matrix phases, whereas conventional quantities such as temperature-gradient magnitude and local heat flux vectors provide limited information on how such redistribution relates to the global conduction task. This study presents a reference-based analysis for quantifying yarn-induced heat flux reorganization in CMCs. A geometrically identical homogeneous matrix model is used as the baseline, and its volume-averaged heat flux vector is adopted as a first-order macroscopic conduction reference. Two descriptors, Excess Deviation (ED) and Directional Deviation (DD), are defined to evaluate the overall vector deviation and directional alignment of local heat flux relative to this reference. The analysis is applied to a ceramic matrix composite vane leading-edge model containing 2D woven, 0° ply-stacked, and 45° ply-stacked yarn architectures. The results show that the 2D woven architecture produces broader matrix conductive-burden relief through continuous in-plane conductive pathways and yarn-undulation-induced through-thickness coupling. In contrast, ply-stacked architectures mainly localize heat flux reorganization near yarn layers, leaving interlayer matrix regions with stronger conductive burden. The 45° ply-stacked configurations achieve similar overall heat-transfer performance to the 0° configurations with a lower yarn volume fraction. These results clarify how yarn architecture controls local heat flux pathway organization and matrix conductive-burden redistribution in a curved CMC vane leading edge.

The formation and evolution of the air entrapment constitute a critical physical mechanism during droplet impact on solid surfaces, directly affecting the performance of systems such as fuel spray in aero engines, spray cooling, and aircraft anti-icing/de-icing. Most existing studies are based on the assumption of ideal spherical droplet impact, ignoring the decisive effect of the actual dynamic state of the droplets from formation to impact on the air entrapment. In this study, the pseudopotential lattice Boltzmann method is employed to investigate the complete dynamic process from droplet formation to impact by means of a combined analysis of morphological evolution and energy conversion. The results reveal that the pre-impact oscillatory state of the droplet influences the onset of air entrapment. The occurrence of air entrapment requires simultaneous fulfillment of both critical morphological and energy conditions, namely that the aspect ratio (AR) is above 1.067 and the kinetic-to-surface energy ratio (Ek/Es) exceeds 4.63. Three distinct evolution patterns emerge across the Weber number range, where the inverse correlation between entrapment size and spreading factor confirms competitive energy allocation between radial expansion and normal cavity formation. The energy released during the entrapment collapse substantially modifies the receding flow structure. These findings establish a quantitative relationship between the initial droplet state and impact behavior and elucidate the fundamental mechanism of air entrapment. This study provides a direct theoretical basis for optimizing droplet impact processes in aerospace applications via active control of injection parameters.

Active regenerative cooling technology represents one of the effective approaches for reducing combustion chamber wall temperatures. Large Eddy Simulations (LES) have been conducted to investigate the flow and heat transfer behavior of supercritical n-decane within various regenerative cooling channels. The simulation findings demonstrate that in contrast to flat regenerative cooling channels, jet regenerative cooling channels substantially amplify turbulent disturbances and efficiently disrupt the growth of the fluid boundary layer. This is achieved through the combined mixing and perturbing actions of jet impingement and crossflow, ultimately yielding a notable 50.32 % enhancement in local maximum heat transfer efficiency. When the temperature draws near to the pseudo-critical point, the thermophysical properties of n-decane experience significant alterations, resulting in localized temperature fluctuations of the wall. Moreover, the smaller the hydraulic diameter, the faster the jet velocity, and the stronger the generated disturbances. When compared to circular jet orifices, oval ones prove more effective in facilitating lateral expansion of the fluid upon wall impingement, thereby minimizing kinetic energy losses. Specifically, at a hydraulic diameter of 0.3 mm, the average wall temperature of oval jets is 74.1 K lower than that of circular jets. The heat transfer process of supercritical n-decane within jet regenerative cooling channels comprises three distinct phases: a buoyancy-driven laminar acceleration phase, a shear-induced turbulent transition phase, and a fully developed turbulent stabilization phase.

To improve the low thermal conductivity challenge of phase change materials (PCM) in energy storage applications, this study introduces a composite thermal energy storage (TES) unit integrating PCM with water. Numerical simulations are employed to examine the influence of a fluctuating heat source on the heat charging dynamics of the unit. Results derived from Taguchi analysis indicate that increasing the amplitude, half-period, and initial temperature of the fluctuating heat source consistently reduces the melting time. The initial temperature exhibited the most significant effect on accelerating the charging process. Furthermore, elevating the amplitude and initial temperature led to a corresponding increase in the mean energy storage rate of the PCM while extending the half-period initially enhanced, then diminished, the mean energy storage rate. The optimal heat source parameters are identified as Case 4, characterized by an amplitude of 6.5 K, a half-period of 15 s, and an initial temperature of 352 K. Compared to the baseline heat source conditions, this configuration demonstrated a 33.7 % improvement in the mean energy storage rate within the PCM, a 48.9 % increase in water, and a 21.2 % reduction in charging time. These findings indicate that the heat source fluctuation has a significant influence on the energy storage process of the complex energy storage unit.

Ceramic matrix composites (CMCs) are recognized as optimal materials for future aero-engine applications due to their low density and excellent high-temperature resistance performance. However, the anisotropic thermal conductivity presents substantial challenges in thermal analysis, which restricts the application to hightemperature components. In this paper, a 2D woven structure model of a CMC plate was reconstructed using 3D Computed Tomography (CT) scanning technology based on its actual structure. Then, numerical simulations were conducted to investigate the coupling heat transfer characteristics of the CMC plate, focusing on different coating types and yarn's fiber volume fractions (V). The results reveal that the overall cooling effectiveness derived from the woven structure model differs from that of the homogeneous model, as the latter fails to capture the temperature gradient differences between the yarn and the matrix. As V increases from 0.2 to 0.5, the overall cooling effectiveness decreases by 2.4 %, and the temperature gradient differences between the yarn and the matrix become more pronounced. Furthermore, applying coatings to the CMC plate intensifies the temperature gradient differences across various regions and enhances the overall cooling effectiveness by up to 2.2 %.

A comprehensive numerical study is conducted to investigate the operational performance of kerosene-assisted aluminum powder combustion in a scramjet engine. A numerical simulation scheme for supersonic multiphase hybrid turbulent combustion is built within the Eulerian-Lagrangian framework. The impacts of control parameters on flow fields and combustion mechanisms are systematically analyzed, and the flow patterns, flame structures, and species distribution inside the tandem hybrid combustion scramjet combustor are elaborated. As indicated by numerical results, kerosene-supported combustion outperforms pure aluminum powder combustion in flame stabilization. It also accelerates the ideal heating and evaporation process of metal powders, alleviating the local high temperature inside the engine, improving the engine's thermal protection performance to a certain extent, and increasing the energy released by combustion by over 25%. In addition, the mass proportion of fuels in dual combustion stages significantly shapes flow patterns and flame morphology inside the combustor. Within the fuel ratio range of 5.0 to 1.5, as the ratio decreases, both the combustion efficiency and total pressure loss present a tendency to increase initially and decrease afterwards. In general, there exists an optimal value range around the fuel ratio of 3.0, which can maximize the combustion efficiency while meeting the required combustion temperature and pressure conditions.

Ceramic matrix composites (CMCs) are regarded as ideal candidates for hot-end components in future aeroengines due to their high-temperature resistance and low density. However, the anisotropy of their thermal conductivity and the multi-phase nature pose significant challenges for numerical simulations. Currently, thermal simulation methods for CMCs can be classified into macro-scale and meso-scale approaches. In this study, both methods are employed to simulate a CMC plate, and the resulting temperature and temperature gradient distributions on internal characteristic sections are compared. The results indicate that the macro-scale method inherently lacks the resolution to capture internal local temperature and gradients, whereas the meso-scale method provides such resolution. Moreover, the internal thermal details are considerably more complex than macro-scale averages suggest. Local temperature fluctuations exhibit a peak relative difference of 17.21%, and the maximum error in gradient prediction reaches 7 & times; 105 K/m, corresponding to a relative difference of 470%. Such substantial prediction inaccuracies directly lead to erroneous thermal stress calculations, posing a significant design risk. Consequently, the meso-scale simulation method is more suitable than the macro-scale method for simulating CMC hot-end components, and can therefore provide valuable guidance for the thermal design of such components.

Turbine blade tip clearance exacerbates aerodynamic losses and raises thermal load on the blade tip, detrimentally affecting blade lifespan and reliability. Arranging the film hole is a prevalent approach for blade tip cooling. A rational hole layout is crucial for improving the film cooling effectiveness and minimizing losses. Based on the conventional nine-hole tip layout along the camber line, this study presents a design concept involving moving one, two, or three film holes from the trailing edge region to the leading edge and adjusting the mid-chord holes downward. Five novel film hole layouts are given rise to by this concept. Numerical simulations are carried out to analyze the film cooling effectiveness and the streamline distribution on different film hole layouts. The results show that moving the trailing edge holes forward can enhance coolant flow on the leading edge and on the suction side. As more trailing edge holes are relocated forward, overall film cooling effectiveness is improved. Specifically, the layout with three trailing edge holes relocated to the leading edge has an 11.47% higher area-average film cooling effectiveness than the nine-hole tip layout along the camber line. The layout with three mid-chord holes shifted downward, with a 2.83% increase, enhances the cooling of the suction side on the mid-chord region and overall cooling uniformity. The structure that integrates both methods described above shows a 14.49% increase over the nine-hole tip layout along the camber line. In addition, changes in the positions of the film holes on the blade tip surface will also affect the aerodynamic losses. These findings provide valuable guidance for designing high-efficiency cooling tip structure.

To address the issues of a slow melting rate and the accumulation of low temperature phase change material (PCM) at the bottom of horizontal thermal energy storage (TES) units, this study proposes a novel bottom-cut optimization strategy. A numerical model is developed and validated experimentally for the horizontal TES unit with various bottom-cut ratios (H/R from 0.28 to 1.0) is developed and validated experimentally. The effects of the cut ratio on melting time, melting front evolution, temperature field, velocity field, and Nusselt and Grashof numbers are analyzed. The results indicate that reducing the cut ratio optimizes the thermal path in the upper region, enhancing natural convection and thermal uniformity. Compared with the circular unit, the unit with a cut ratio of 0.28 reduces the complete melting time from 28,310 s to 7380 s, representing a decrease of 73.93%. Meanwhile, the average Nusselt number and average Grashof number increase by 155.45% and 75.95%, respectively, indicating enhanced convective heat transfer intensity. Furthermore, a multilayer perceptron (MLP) model is trained on 1135 numerical datasets to rapidly predict the melting performance. The model achieves relative errors within ±10% on both the training and testing sets. This work offers an efficient approach for designing high-performance TES devices through bottom-cut optimization combined with machine learning for rapid prediction.

At extremely high Mach number (Ma >= 8), kerosene is faced with issues of cracking with a limited heat sink for regenerative cooling. Supercritical CO2 can be used as additional cooling method for regenerative cooling because of its excellent heat and mass transfer capability and it can easily convert heat into electricity for the engine electric system. In this study, pin-fins are applied to a regenerative cooling channel using sCO(2) to further enhance heat transfer at extremely high heat flux. Heat transfer and fluid flow are analyzed by the k-omega SST model considering effects of pitch ratio, solid materials and accelerations. From this study, compared with a smooth cooling channel, the pin-fin channel (Case 3) obtains a heat transfer enhancement of 3.08, a friction factor of 4.66, thermal performance enhancement of 1.84, and the maximum temperature of the heated surface is decreased by 36 % at Re = 45,000. The maximum velocity is found at the near-wall regions determined by the combined effects of temperature difference and accelerations. When the channel material is Cu with the high thermal conductivity, the maximum temperature is decreased by 37 % compared with a steel channel and the temperature distribution also becomes more uniform.

Latent heat storage is an effective method to solve the intermittency problem of solar heat utilization. However, the low thermal conductivity of phase change heat storage materials limits the heat transfer efficiency. Therefore, the method of coupling heat transfer enhancement with two optimization methods of rotation and conical design is proposed in this study. The numerical simulation method was used to reveal the phase change characteristics of different heat storage tanks under rotating conditions. The numerical model of the rotational phase change is established through the finite volume method and verified. Subsequently, the melting heat storage characteristics of cylindrical, positive cone and inverted cone heat storage tanks with rotating angular velocities of 0 rad/s and 1 rad/s are studied. The results show that the melting rate and heat storage rate increase significantly under rotating conditions. The full melting time of the inverted cone heat storage tank under rotating condition is the shortest, and the heat storage rate is the fastest, which is 0.0162 kJ/s, which is increased by 60.40% compared with the benchmark case.

In this study, a novel sensible-latent heat composite energy storage structure is constructed by filling the bottom of the phase change material with water. Based on the thermal conductivity of water, the heat transfer and sensible heat storage are enhanced, and the energy storage performance of different material proportions under constant heat flux and solar thermal radiation conditions is explored. The effects of sensible heat material filling height and heat flux of heat source on internal PCM melting process and overall energy storage performance are studied by numerical simulation, and an experimental system is constructed to conduct model reliability analysis. The comprehensive performance improvement of the composite structure under all-day solar radiation conditions in Xi'an summer is further studied. The results show that under constant heat source density (qconst= 1000 W/m2), the melting time of Case 6 structure with 50 % water is 43.04 % lower than that of Case 1 structure with pure paraffin. However, at the end of melting, the sensible and total energy absorption of PCM in Case 6 decreased by 74.67 % and 56.20 %. Comparing the solar thermal radiation conditions from 6:00 to 18:00 on a sunny day in Xi'an for Case 1 and Case 6, the total heat energy obtained by Case 6 after 12 rounds of heat storage throughout the day is increased by 16.12 % compared with Case 1. Although the volume of PCM in Case 6 is reduced by half, the overall energy storage rate is higher.