直接孔隙尺度和体积平均数值模拟是研究多孔介质太阳能吸热器性能的两种有效方式。为了阐明不同数值方法在预测传热过程中的差异，本文在稳态和瞬态条件下开展了两种方法的对比研究。数值模型分别基于X射线计算机断层扫描和局部热非平衡模型建立，体积平均数值模拟中不可或缺的经验参数通过蒙特卡罗光线追踪法和直接孔隙尺度数值模拟确定。体积平均数值模拟方法预测的吸热器出口空气温度与直接孔隙尺度模拟结果吻合良好，随着吸热器工作温度升高，预测差异逐渐增大，稳态和瞬态数值模拟的最大相对误差分别为5.5%和3.68%。然而，体积平均方法无法捕捉空气和多孔骨架的局部温度信息，低估了吸热器的入口温度，导致对吸热器热效率的高估，最大相对误差为6.51%。比较结果表明，在准确地选取经验参数的基础上，体积平均方法能够实现吸热器瞬态和稳态性能的快速、准确预测。

非晶二氧化铪(a-HfO₂)由于其宽带隙和高介电常数等优异性能在半导体器件材料中被广泛关注。然而，a-HfO₂热输运性质尚不明确，由此阻碍了它在电子领域的潜在应用。本工作使用基于分子动力学的方法系统地研究了a-HfO₂的热输运性质。非平衡态分子动力学模拟表明，a-HfO₂的热导率在100 nm以下具有明显的尺寸效应。热流谱分解分析方法表明了传播子和扩散子的热输运对系统长度的敏感性。通过格林-久保模式分析方法计算表明a-HfO2的热导率随温度的升高而升高。通过量化不同温度下各热载流子对热导率的贡献，我们发现在低温下(<100 K)，传播子比扩散子对热输运的贡献显著，而在高温下，扩散子主导了热输运。

冷热电联产系统中生物质与太阳能的互补利用为能源危机和环境污染提供了有效的解决方案。本文旨在提出一种基于生命周期评估(LCA)方法的多目标优化模型，用于太阳能与生物质冷热电联供系统的优化设计。通过将多联产系统的生命周期过程划分为6个阶段，来分析能源消耗和温室气体排放。并结合全生命周期环境影响、可再生能源贡献和经济效益等评价指标，对混合系统的综合性能进行了优化。采用结合TOPSIS方法的非支配排序遗传算法II (NSGA-II)来搜索Pareto前沿结果，从而获得最优性能。将所开发的优化方法应用于工业园区的案例研究。结果表明，相较于参考系统，混合系统的性能优化后的效果显著，环境影响负荷降低率(EILRR)为46.03%，可再生能源贡献率(RECP)为92.73%，年总成本节约率(ATCSR)为35.75%。通过比较不同阶段的污染物当量排放量，运行阶段的污染物排放量最大，其次是原料获取阶段。综上可以看出，本文提出的基于LCA的多目标优化模型为设计和优化混合生物质能和太阳能的冷热电联产系统提供了一条潜力路径。

In Iran, the intensity of energy consumption in the building sector is almost 3 times the world average, and due to the consumption of fossil fuels as the main source of energy in this sector, as well as the lack of optimal design of buildings, it has led to excessive release of toxic gases into the environment. This research develops an efficient approach for the simulation-oriented Pareto optimization (SOPO) of building energy efficiency to assist engineers in optimal building design in early design phases. To this end, EnergyPlus, as one of the most powerful and well-known whole-building simulation programs, is combined with the Multi-objective Ant Colony Optimization (MOACO) algorithm through the JAVA programming language. As a result, the capabilities of JAVA programming are added to EnergyPlus without the use of other plugins and third parties. To evaluate the effectiveness of the developed method, it was performed on a residential building located in the hot and semi-arid region of Iran. To obtain the optimum configuration of the building under investigation, the building rotation, window-to-wall ratio, tilt angle of shading device, depth of shading device, color of the external walls, area of solar collector, tilt angle of solar collector, rotation of solar collector, cooling and heating setpoints of heating, ventilation, and air conditioning (HVAC) system are chosen as decision variables. Further, the building energy consumption (BEC), solar collector efficiency (SCE), and predicted percentage of dissatisfied (PPD) index as a measure of the occupants’ thermal comfort level are chosen as the objective functions. The single-objective optimization (SO) and Pareto optimization (PO) are performed. The obtained results are compared to the initial values of the basic model. The optimization results depict that the PO provides optimal solutions more reliable than those obtained by the SOs, owing to the lower value of the deviation index. Moreover, the optimal solutions extracted through the PO are depicted in the form of Pareto fronts. Eventually, the Linear Programming Technique for Multidimensional Analysis of Preference (LINMAP) technique as one of the well-known multi-criteria decision-making (MCDM) methods is utilized to adopt the optimum building configuration from the set of Pareto optimal solutions. Further, the results of PO show that although BEC increases from 136 GJ to 140 GJ, PPD significantly decreases from 26% to 8% and SCE significantly increases from 16% to 25%. The introduced SOPO method suggests an effective and practical approach to obtain optimal solutions during the building design phase and provides an opportunity for building engineers to have a better picture of the range of options for decision-making. In addition, the method presented in this study can be applied to different types of buildings in different climates.

串列叶片是一种可以延迟分离的流动控制方法。本研究利用数值方法探究了扩压因子和节距比对串列叶片流动结构的影响。单个叶片扩压因子从0.328变化到0.484。节距比从0.80变化到0.92。结果表明，损失系数随扩压因子的增加而增加，随节距比的增加而减小。前叶片叶根角区失速出现在所有研究的情况。间隙流决定了后叶片的角区分离情况。改变节距比和扩压因子会改变间隙流的动量分布。后叶片的角区分离会由于通道涡卷吸低动量间隙流和前叶片的叶根角区失速流体而受到抑制。增加扩压因子会导致后叶片的攻角发生变化，从而导致后叶片角区分离的变化。将串列叶片与参考的出口单列叶片进行对比。所有攻角下，串列叶片的性能都优于参考叶片。在设计攻角下，损失系数降低了26.35%，增压能力提高了7.89%。串列叶片在正攻角下的流动失稳是由前叶片的叶根角区失速造成的。间隙流的强度会随着攻角的增加而提高，从而防止后叶片在正攻角时发生角区分离。

本文针对1.5级轴流跨音压气机开展非定常数值模拟，以探究非定常扰动产生机制。首先利用试验测量数据对数值仿真结果进行了校核，在数值与试验结果一致性较好的前提下对压气机非定常流动机理进行深入分析。通过设置虚拟探针对近失速工况流场进行监测，确定非定常扰动源于动叶叶顶区域，且叶片压力面扰动最强，其频率呈宽频特性。结合叶顶瞬态流场特征分析，发现泄漏涡与激波干涉使得泄漏涡破碎，其产生的新涡核在流场中迁移诱发了非定常压力扰动。进一步分析压气机节流过程中泄漏涡与激波的相互作用，发现泄漏涡强度与激波强度随流量的减小而逐渐增大，当两者组合到达第一阈值，叶顶出现了单一的扰动频率；当两者组合到达第二阈值，叶顶扰动频率向宽频转变。

本研究基于COMSOL多物理场仿真软件，对液态金属锂在真空自由分子流状态下的蒸发过程进行了建模和数值模拟。通过系列研究，分析了锂原子在蒸发过程中的运动状况。根据现有的液态金属锂饱和蒸汽压实验值，得到了液态金属锂在600 K-900 K范围内饱和蒸汽压与温度的关系。建立了二维对称模型(3.5 mm×20 mm)，分别模拟了750 K、780 K、800 K、810 K、825 K和850 K壁温下液态锂的瞬态蒸发过程。研究了温度、蒸发系数、背压和长径比对蒸发过程的影响，分析了蒸发过程中分子通量和压力的变化趋势及原因。同时，模拟了变壁温条件下的蒸发过程。本研究使液态锂在真空分子流中的蒸发过程更加清晰，为空间反应堆和核聚变相关领域提供了理论支持。

本文在定容燃烧弹上研究RP-3航空煤油在非蒸发和蒸发环境下的喷雾特性，并对比了RP-3航空煤油与柴油的喷雾贯穿距离、喷雾锥角和喷雾面积。研究发现，RP-3航空煤油和柴油的非蒸发喷雾并没显著的差异，二者的喷雾贯穿距离、喷雾面积和喷雾锥角在大多数试验条件下几乎一致。在蒸发环境下，RP-3航空煤油比柴油产生更短的液相喷雾贯穿距离和更小的喷雾面积，这些差异在较低的环境温度下尤为明显。然而，燃料因素对蒸发喷雾锥角的影响较小。此外，增大环境密度或环境温度可减少燃油液相的喷雾贯穿距离和喷雾面积，相比于RP-3航空煤油，这些因素对于柴油的影响尤为明显。

The unsteady cloud cavitation shedding in fuel nozzles greatly influences the flow characteristics and spray break-up of fuel, thereby causing erosion damage. With the application of high-pressure common rail systems in diesel engines, this phenomenon frequently occurs in the nozzle; however, cloud cavitation shedding frequency and its mechanism have yet to be studied in detail. In this study, a visualization experiment and proper orthogonal decomposition (POD) method were used to study the variations in the cavitation shedding frequency and analyze the cavitation flow structure in a 3 mm square nozzle. In addition, large eddy simulation (LES) was performed to explore the causes of cavitation shedding, and the relationship between cavitation and vortices. With the increase of the inlet and outlet pressure differences, and fuel temperatures, the degree of cavitation intensified and the frequency of cavitation cloud shedding gradually decreased. LES demonstrated the relationship between the vortices, and the development, shedding, and collapse of the cavitation clouds. Further, the re-entrant jet mechanism was found to be the main reason for the shedding of cavitation clouds. Through comparative experiments, the fluctuation of the vapor volume fraction in the nozzle hole accurately predicted the regions with stable cavitation, re-entrant jet, cavitation cloud shedding, and collapse. The frequency of cavitation shedding can then be calculated. This study employed an instantaneous POD method based on instantaneous cavitation images, which can distinguish the evolution process and characteristics of cavitation in the nozzle hole of diesel engines.

Present work investigates the heat transfer and melting behaviour of phase change material (PCM) in six enclosures (enclosure-1 to 6) filled with paraffin wax. Proposed enclosures are equipped with distinct arrangements of the fins while keeping the fin’s surface area equal in each case. Comparative analysis has been presented to recognize the suitable fin arrangements that facilitate improved heat transfer and melting rate of the PCM. Left wall of the enclosure is maintained isothermal for the temperature values 335 K, 350 K and 365 K. Dimensionless length of the enclosure including fins is ranging between 0 and 1. Results have been illustrated through the estimation of important performance parameters such as energy absorbing capacity, melting rate, enhancement ratio, and Nusselt number. It has been found that melting time (to melt 100% of the PCM) is 60.5% less in enclosure-2 (with two fins of equal length) as compared to the enclosure-1, having no fins. Keeping the fin surface area equal, if the longer fin is placed below the shorter fin (enclosure-3), melting time is further decreased by 14.1% as compared to enclosure-2. However, among all the configurations, enclosure-6 with wire-mesh fin structure exhibits minimum melting time which is 68.4% less as compared to the enclosure-1. Based on the findings, it may be concluded that fins are the main driving agent in the enclosure to transfer the heat from heated wall to the PCM. Proper design and positioning of the fins improve the heat transfer rate followed by melting of the PCM in the entire area of the enclosure. Evolution of the favourable vortices and natural convection current in the enclosure accelerate the melting phenomenon and help to reduce charging time.

Phase change materials (PCMs) designate materials able to store latent heat. PCMs change state from solid to liquid over a defined temperature range. This process is reversible and can be used for thermo-technical purposes. The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management. The experiment is conducted in two test rooms in Antofagasta (Chile) during summer, fall, and winter. The PCM is integrated into the rooftop of the first test room, while the roof panel of the second room is a sealed air cavity. The work introduces a numerical model, which is built using the finite difference method and used to simulate the rooms’ thermal behavior. Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates. Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1°C±10.6°C, while the one of the air-panel room varies 28.3°C±18.5°C. Under the experiment’s conditions, the PCM room’s indoor temperature observes smoother diurnal fluctuations, with lower maximum and higher minimum indoor temperatures than that of the air-panel room. Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter, as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures. This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs, and improve indoor thermal comfort in different climates of Chile.

在跨音压气机中，旋转失速到喘振的过渡过程是非常短暂的，通常压气机旋转失速后来不及采取措施来防止喘振。因此，有必要寻找一些旋转失速的先兆，其出现可以为喘振的预防提供充足的时间。本研究对旋转失速发生前的一系列工况进行了全周非定常气动CFD分析，并仔细分析该过程中非定常流动特征的变化规律来寻找失速先兆。研究发现在不同工况下的非定常流场中存在周向节径数不同的扰动波并将其作为旋转失速的先兆，该扰动从叶片前缘产生，在周向和轴向充分发展，并以固定的转速在周向旋转，最终确认该失速先兆的时空模态特征可用于旋转失速预警。

Fast fluid transport on graphene has attracted a growing body of research due to a wide range of potential applications including thermal management, water desalination, energy harvesting, and lab-on-a-chip. Here, we critically review the theoretical, simulational, and experimental progress regarding the fluid slippage on graphene. Based on the summary of the past studies, we give perspectives on future research directions towards complete understanding and practical applications of slip flow on graphene.

碳排放问题日益引起人们的关注，高温领域的热能传递效率问题成为关注焦点。高温热管(HTHP)是一种工作温度高的高效传热装置，在太阳能热电、高温烟气余热回收、工业炉窑、核工业和航空等领域有广泛应用。本文从影响高温热管传热性能的因素、高温热管的仿真及理论分析，这两方面对近30年的相关文献进行了汇总分析。首先介绍了工质、热管结构和毛细芯结构对其传热性能的影响研究，并对每个方面的较优研究成果进行了一定的介绍；然后回顾了高温热管的数值模拟中所采用过的一些重要假设，对传热极限的一些理论研究结果；最后基于文献分析结果，对高温热管未来的研究方向尝试提出了一些建议。希望本文对高温热管领域从业者有一定的参考意义。

印刷电路板式换热器（PCHE）因其传热效率高、紧凑性好等优点，近年来在S-CO₂循环发电系统中得到了广泛的应用。但PCHE通道构型较多，实际工程应用时缺少构型选择的判断依据。因此，本文针对直通道、之字形通道、波纹通道和翼型翅片通道四种典型PCHE通道构型，在“三场协同”原理的指导下，对通道内流场和温度场以及流场和压力场的协同性进行讨论；进一步，对比分析了四种通道构型的综合换热性能；最后，获得了四种典型通道构型的传热和阻力关联式。结果表明，直通道PCHE的速度场与压力场间协同性较优，因此其阻力损失相对较小。之字形、波纹通道和翼型翅片可以减小速度和温度梯度间的夹角α，从而强化了换热。与之字形通道相比，波纹通道由于具有圆角，因此减小了流动阻力。在本文所研究的Re范围内，所提出的PCHE传热和阻力关联式最大误差为7%，拟合精度良好。本文的研究可为不同通道构型PCHE的选择和设计提供参考。

超临界二氧化碳(SCO₂)离心压缩机是SCO₂闭式布雷顿循环系统中的关键部件。深入了解压缩机内部的损失机制对于优化设计至关重要。然而，接近临界点时，SCO₂的物理特性高度非线性，压缩机内部流动与其特性密切相关，这不可避免地影响了压缩机内气动损失的产生。本文通过实验验证的数值方法对压缩机的损失机制进行了全面分析。首先，数值模拟方法针对Sandia SCO₂压缩机的实验结果进行了验证。其次，比较了使用SCO₂、理想二氧化碳（ICO₂）和理想空气（IAir）三种流体时压缩机的性能和损失分布。结果显示，在低流量系数下，SCO₂的性能与IAir相当，但在接近堵塞条件下明显不如其他两种流体。三种流体中的损失分布有明显区别。在叶轮中，SCO₂效率最低，其次是ICO₂和IAir。随着流量系数的增加，这些差异被放大。这是由于更强的叶顶区域周向压力梯度加剧了在轮盖/轮毂端壁上的边界层累积。此外，由于SCO₂的声速降低，激波在喉部区域更早出现，导致SCO₂叶轮内出现显著的边界层分离现象。

在电子设备冷却系统中，本工作提出了一种将遗传算法与自适应深度学习相结合的三维数据驱动优化设计模型，实现了碳/碳复合材料结构中的传热定向调控和优化。随优化进行的自适应过程使得深度学习模型对优化前缘结构的温度预测更接近真实值。利用该模型对三维复合结构中孔隙和高导热碳纤维的分布进行了优化，结果表明，当构建结构的孔隙率在3%至11%之间变化时，优化结构中的电子器件表面温度比初始结构低19.1-27.5%。电子器件的表面温度随着孔隙率的增加而增加。高导热碳纤维电子器件表面附近，孔隙分布于结构中间区域将使热疏导复合结构表现出最优散热能力。此外，本优化模型的计算时间缩减为传统遗传算法的十分之一。

压缩机在近临界区的低功耗是实现超临界CO₂布雷顿循环高效运行的关键因素。在压缩机的数值模拟中，在临界点附近CO₂物性的快速变化使得冷凝现象难以捕捉。本文研究了流体物理性质对冷凝现象的影响。首先比较了SRK EOS(状态方程)、PR EOS和SW EOS中CO₂的物理性质差异，然后对喷嘴和压缩机进行了仿真。结果表明，3种EOSs预测的凝结位置基本一致。与SW EOS相比，PR和SRK EOS预测的最大凝结质量分数差异分别为5.7%和11.5%，总压比差异分别为0.3%和3.8%。结果表明，PR EOS可用于工程实际的数值模拟。由于其物性计算结果更接近实际物性，而物性变化更平缓，具有相当的精度和数值稳定性。

循环工质对脉动热管传热特性具有重要影响。本文采用实验方法研究了以相变微胶囊（MEPCM）悬浮液（质量浓度为0.5%、1%）和超纯水为工质的脉动热管传热特性。结果表明，MEPCM 悬浮液能够提高脉动热管的运行稳定性。当倾角为90°时，蒸发端温度相较于超纯水降低，且蒸发端温度随MEPCM悬浮液浓度的增加而降低。脉动热管的传热性能与倾角呈正相关，90°时最优，而加热功率增大，倾角的不利作用减小。倾角为90°，以质量浓度为1%的MEPCM悬浮液为工质的脉动热管传热热阻最低，超纯水次之，质量浓度为0.5%的MEPCM悬浮液脉动热管传热热阻最高；倾角为60°和30°时，重力对工质流动的促进作用减弱，由于MEPCM悬浮液具有较高的粘度，超纯水脉动热管传热热阻最低；倾角为60°时，加热功率小于230 W时，质量浓度为0.5%的MEPCM悬浮液脉动热管热阻低于质量浓度为1%时的热阻；加热功率为230-250 W之间时，MEPCM悬浮液脉动热管的热阻趋于一致；加热功率大于270 W时，质量浓度为1%的MEPCM悬浮液脉动热管热阻低于质量浓度0.5%时的热阻。

The standing-wave thermoacoustic engines (TAE) are applied in practice to convert thermal power into acoustic one to generate electricity or to drive cooling devices. Although there is a number of existing numerical researches that provides a design tool for predicting standing-wave TAE performances, few existing works that compare TAE driven by cryogenic liquids and waste heat, and optimize its performance by varying the stack plate spacing. This present work is primarily concerned with the numerical investigation of the performance of TAEs driven by cryogenic liquids and waste heat. For this, three-dimensional (3-D) standing-wave TAE models are developed. Mesh- and time-independence studies are conducted first. Model validations are then performed by comparing with the numerical results available in the literature. The validated model is then applied to simulate the standing-wave TAEs driven by the cryogenic liquids and the waste heat, as the temperature gradient ΔT is varied. It is found that limit cycle oscillations in both systems are successfully generated and the oscillations amplitude is increased with increased ΔT. Nonlinearity is identified with acoustic streaming and the flow reversal occurring through the stack. Comparison studied are then conducted between the cryogenic liquid-driven TAE and that driven by waste heat in the presence of the same temperature gradient ΔT. It is shown that the limit cycle frequency of the cryogenic liquid system is 4.72% smaller and the critical temperature ΔT_cri =131 K is lower than that of the waste heat system (ΔT_cri=187 K). Furthermore, the acoustic power is increased by 31% and the energy conversion efficiency is found to increase by 0.42%. Finally, optimization studies on the stack plate spacing are conducted in TAE system driven by cryogenic liquids. It is found that the limit cycle oscillation frequency is increased with the decreased ratio between the stack plate spacing and the heat penetration depth. When the ratio is set to between 2 and 3, the overall performance of the cryogenic liquid-driven TAE has been greatly improved. In summary, the present model can be used as a design tool to evaluate standing-wave TAE performances with detailed thermodynamics and acoustics characteristics. The present findings provide useful guidance for the design and optimization of high-efficiency standing-wave TAE for recovering low-temperature fluids or heat sources.

燃气轮机的使用越来越广泛，其研发和生产体现了一个国家的工业能力和水平。由于多变的工作环境，通常燃气轮机都是工作在环境温度、载荷和燃料等多种工况同时变化的条件下。然而目前的研究以单工况变化为主，未充分考虑不同条件同时变化的情况。本文在单工况的基础上进一步研究燃气轮机的温度-载荷、燃料-载荷和燃料-温度三种双变工况性能。首先建立了燃气轮机的整机模型，其中压气机模型对燃气轮机性能影响最大，因此本文结合了gPROMs的工程建模优势和MATLAB神经网络强大的数学计算能力，得到了更为精确的压气机模型。然后以天然气燃料的变工况为基础，分别研究了部分载荷、环境温度和改烧另外四种煤制气这三个因素中两个因素同时变化时，燃机轮机的运行性能状况，即燃气轮机双变工况性能，这其中主要以出力和效率两个参数的变化为主。研究结果表明随着环境温度的升高，燃气轮机效率和功率输出会下降；随着燃料热值的降低，功率输出和燃气轮机效率增加；随着载荷降低燃气轮的效率降低，这些变化规律与单变工况一致，但在燃料和温度同时变化时仅调节IGV角度无法避免燃气轮机在30℃以上时出现喘振现象，此时需要调节抽气率来辅助调节才可使燃气轮机安全稳定运行。因此，燃气轮机双变工况研究对燃气轮机的调峰运行具有重要的参考意义。

锂离子电池是未来电动汽车和储能技术发展的重要组成部分和储能单元。因此，为应对锂离子电池的温度敏感性，维护锂离子电池的安全运行，采用合适的电池热管理系统（BTMS）是非常有必要的。本文从小规模电池组和大规模电化学储能电站（EESPS）两个方面探讨了目前主要的BTM策略和研究热点。详细介绍了各种散热方式（空气散热、液体散热、PCM散热、热管散热、混合冷却散热）的实际应用情况、优缺点及未来发展趋势。其中，结合工程应用，对风冷和液冷进行了深入的讨论，对PCM、热管和混合冷却的最新研究进展进行了阐述。本研究对BTMS在各个规模尺度上的研究提供了一个全面的认识。

Hyperloop已成为未来高速轨道交通的关键储备技术之一。管中的气体被压缩和摩擦，带来强烈的空气动力热效应。Hyperloop的流场特性和气动热效应的研究尚处于起步阶段，对流场结构的研究还很缺乏。在本研究中，喷管理论被用来初步判断壅塞流动现象。根据不同工况下的计算结果，获得了Hyperloop中壅流动现象的识别依据。此外，本研究还分析了壅塞/未壅塞流动对管内环形空间流动结构、温度和压力分布的影响。基于传统的高速铁路空气动力学、航空航天领域的相关理论和计算方法，结合模型试验数据，对管内流场特性进行可靠性验证。在壅塞流动下，列车前方会形成正激波。局部流场的温升超过50K，滞止区温升超过88K，压力约为管内初始压力的1.7倍。在未壅塞流动下，与不同的来流马赫数对应的流场分布呈现差异。当来流是超音速时，流场保持超音速，在列车前部形成弓形激波。激波或膨胀波导致局部流场表现出温度和压力的显著波动。相反，当来流是亚音速时，管内的流场保持亚音速，未观察到明显激波结构。

The costs of conventional fuels are rising on a daily basis as a result of technical limits, a misallocation of resources between demand and supply, and a shortage of conventional fuel. The use of crude oil contributes to increased environmental contamination, and as a result, there is a pressing need to investigate alternate fuel sources for car applications. Biodiesel is a renewable fuel that is derived chemically by reacting with the sources of biodiesel. The present research is based on analyzing the effect of fish oil biodiesel-ethanol blend in variable compression engine for variable compression ratio (VCR). The processed fish oil was procured and subjected to a transesterification process to convert fatty acids into methyl esters. The obtained methyl esters (biodiesel) were blended with ethanol and diesel to obtain a ternary blend. The ternary blend was tested for its stability, and a stable blend was obtained and tested in VCR engines for its performance, combustion, and emission characteristics. In the second phase, experiments are conducted in the diesel engine by fueling the fish oil methyl ester and ethanol blended with diesel fuel in the concentration of 92.5 vol% of Diesel+7.5 vol% of Fish oil+1.25 vol% ethanol, 92.5 vol% of Diesel+7.5 vol% of Fish oil+5 vol% ethanol, 87.5 vol% of Diesel+12.5 vol% of Fish oil+1.25 vol% ethanol, 87.5 vol% of Diesel+12.5 vol% of Fish oil+5 vol% ethanol, 82.5 vol% of Diesel+17.5 vol% of Fish oil+1.25 vol% ethanol, 82.5 vol% of Diesel+17.5 vol% of Fish oil+ 5 vol% ethanol to find out the performance parameters and emissions. Because the alternative fuel performs better in terms of engine performance and pollution management, the percentage chosen is considered the best mix. The results showed that the use of a lower concentration of ethanol in the fish oil biodiesel blend improved the engine thermal efficiency by 5.23% at a higher compression ratio. Similarly, the engine operated with a higher compression ratio reduced the formation of HC and CO emissions, whereas the NO_x and CO₂ emissions increased with an increased proportion of biodiesel in diesel and ethanol blends.

接触热阻作为一种重要而有效的接触传热指标，是传热过程中普遍存在的现象。在能源、航空航天、电子封装、低温制冷等领域，可以直接影响产品的可靠性、满负荷性能、功耗甚至生命周期。因此，增强界面传热和抑制接触热阻变得越来越重要。在此背景下，本文阐述了热接触热阻的概念以及减小接触热阻的方法。在回顾了现有的接触热阻测量方法和表征界面形态的基础上，重点介绍了接触热阻的理论基础，包括接触界面的二维数学特征以及量化接触热阻的理论和经验模型。然后阐述了热、力、几何对于接触热阻的影响。在宏观机理的基础上，总结了现有的抑制接触热阻的方法，重点回顾了聚合物复合热界面材料和填充高导热填料的金属界面材料以及新材料的开发方法。

薄膜型催化剂是一种具有应用前景的催化剂，具有节约原料，低成本高效的特点。使用一步法制备了一系列具有不同Fe含量的CuFeOx薄膜催化剂，并测试了空速185,000 mL g^-1 h^-1下甲烷对 N₂O 的催化还原特性。通过XRD、EDX 和 XPS表征发现铁含量的增加会显著影响分散性，并生成活性较低的偏析Fe₂O₃相，研究结果表明，Cu和Fe之间的协同作用在许多维度影响了CuFeOx薄膜催化剂的特征，如空心结构、比表面积、纳米微晶尺寸、催化剂表面Cu+、Fe³⁺、氧的含量，表面的还原程度和强活性位点。采用 DFT 计算，研究了 N₂O在CuFeO₂ (012) 表面模型上的吸附和分解过程。表面Fe位点和空心位点对N₂O分解具有活性，N2O在Fe位点和空心位点的分解能垒在0 K时分别为1.02 eV和1.25 eV。本文提出的通过掺杂氧化铁调控催化剂活性的方法可以为改进CH4催化还原N2O效果提供一种可能的途径。

为了解决循环流化床（CFB）机组智能和高效控制的迫切需求，开发超临界循环流化床（SCFB）机组关键运行参数的动态模型至关重要。因此，本文提出了数据知识驱动的SCFB机组床温、负荷和主蒸汽压力的动态模型。首先，采用知识驱动的方法建立SCFB机组关键运行参数的动态模型。模型参数基于单元的操作数据来确定，并进行持续优化。然后，利用双向长短期记忆结合卷积神经网络和注意力机制建立床温、负荷和主蒸汽压力的动态模型。最后，提出了基于临界权重法和变异系数法的协同集成方法，以建立数据知识驱动的SCFB机组关键运行参数模型。与其他方法相比，该模型具有较高的精度和拟合能力，能够有效捕捉动态特性，可为SCFB机组智能灵活控制模式的设计提供研究依据。

旋转不稳定是一种复杂的流动现象，随压气机气动负荷的不断提高，其诱发的叶片非同步振动问题已成为压气机设计面临的重要挑战。本研究旨在了解跨声速轴流压气机转子旋转不稳定引发的叶片非同步振动现象。实验中，叶片的非同步振动和气流激励通过应变片和壁面机匣压力脉动传感器获取，使用全环非定常数值模拟揭示了压气机内非同步气流激励的产生机制。结果表明：第一级转子叶片呈现一阶弯曲模态下的非同步振动，非同步振动的发生伴随着压力脉动的急剧增加，其幅值可达20%水平。当叶片处于大幅值振动时，非定常气流激励频率将锁定至叶片结构的固有频率，数值预测的非同步气流激励频率与实验结果吻合较好。周向不稳定流动气流扰动的主要模态数约为叶片数的47%，其周向尺度占据2～3栅距，叶尖泄漏流和吸力面分离涡相互作用使得叶尖不稳定涡在流向发生振荡，是引起叶片非同步振动的主要原因。

塑性结晶新戊二醇（NPG）具有庞压卡效应。然而，它们的应用在几个方面受到限制，例如低导热系数、大热滞后和差回弹性能。在本研究中，选择了具有超高导热率和高机械强度的多壁碳纳米管（MWCNTs）来增强NPG的性能。最佳混合比例被确定为NPG与3wt%MWCNTs的复合材料，该复合材料在牺牲较少的相变焓的情况下能够将过冷度降低6K。随后，最佳配比的复合材料的综合性能与纯NPG进行了比较。在40 MPa的情况下，观察到390 J·K^–1·kg^–1的熵变化和9.9 K的温度变化。此外，所需的最小驱动压力降低了19.2%，以实现可逆的压热效应。此外，复合材料的热导率提高了约28%，显著缩短了压热制冷循环中的热交换时间。更为重要的是，超高的压力释放率使复合材料的回弹时间减少了73.7%，为恢复膨胀功提供了新的机会。

Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering, energy conversion, and sustainability. This research addresses the challenge of enhancing these critical aspects to ensure prolonged system performance and durability in the context of evolving energy technologies. This research analyses the anti-oxidation and filtration behaviours of micro and nano-scale structures in the context of electro- and photo-thermal energy conversion and also storage systems. A micro multiscale hierarchical structure strategy is presented to fabricate multi-scale double-layer porous wick evaporators with the electrospun nanofibers made of gelatin-polyamide 6 (GPA6) and Ti₃C₂T_x MXene/silver nanowire with Cellulose Micro/NanoFibers (CMNF) cryogens by using spark plasma sintering (SPS) based high-pressure hydrothermal treatment model. An excellent anti-oxidation effect was offered by coating the film in thermal conditions and the anti-oxidation properties were further examined from 500°C to 850°C. The results are analysed using Matlab software to improve the efficiency of energy conversion processes by integrating nanostructures into thermal systems, to increase energy output while minimizing losses. The silver nanowire is with a heat transfer coefficient of 78%, a mass remaining rate of 98.7%, and an energy storage efficiency of 23.8%. This study enhances energy density and duration by integrating nanostructures into thermal systems while minimizing energy losses, and it not only exhibits excellent anti-oxidation properties but also possesses superior filtration capabilities for designing and engineering multifunctional nanomaterials.

随着各国提出碳中和目标，能源结构的清洁转型已成为国际上的热点和潮流。可再生能源发电将占主要比例，但这也导致了电力供应不稳定的问题。目前，大规模储能技术还不成熟。提高燃煤发电厂的灵活性以抑制可再生能源发电的不稳定性是一条可行的途径。热能储存是提高燃煤电厂灵活性的可行技术。本文综述了基于储热技术的燃煤电厂柔性改造研究，主要包括基于热水罐的中低温储热和基于熔盐的高温储热。总结了目前的技术难点，并对未来的发展前景进行了展望。热能储存系统和燃煤发电系统的结合是基础，倾斜温度层的控制和熔盐的选择与开发是关键问题。作者希望本文的研究能为燃煤电厂的柔性改造研究提供参考，也希望能促进蓄热基础在具体燃煤电厂改造项目中的应用。

聚酰亚胺（PI）薄膜广泛应用于印刷电路板、电子封装、界面面材料、显示面板等领域。提高PI膜的热导率对促进微电子器件的有效散热具有重要意义。本文设计了具有多个氢键的三聚氰胺氰尿酸盐（MC），并通过原位共沉淀法将其引入水溶性聚酰胺酸（Ws-PAA）溶液中。MC超分子在PI链的末端形成化学键，同时也通过氢键和π-π共轭来限制相邻链，通过这种分子焊接策略来改善链的排列。定制的PI/MC薄膜表现出各向异性热导率（TC）：面内TC可达到0.93W/mK，而透面TC为0.60W/mK。微观形态和结构特征证实了完整的热传导途径的形成。所开发的薄膜也显示出在微电子器件中作为散热介质的潜在应用前景。

导热增强体设计能够有效克服相变材料导热能力低的缺点。本文研究的主要贡献首先是讨论了在相同金属质量的条件下，如何通过在多孔结构中嵌入翅片主动增强熔融相变材料的自然对流，同时提高热传导能力，从而提升相变传热性能。此外，基于增材制造技术设计和制备了混合翅片-点阵结构导热增强体。采用两方程数值方法研究了相变材料的传热过程，并通过实验数据验证了该方法的有效性。数值计算结果表明，在点阵结构中合理地引入翅片不仅有效增强了熔融相变材料的自然对流，同时进一步提高了热传导能力。增强自然对流提高了相变材料的熔化速率以及降低了壁面温度，例如，由于金属铝翅片的存在，完全熔化时间和壁面温度分别降低了11.6%和19.7%。此外，混合翅片-点阵结构的孔隙率、孔密度和翅片尺寸等参数对相变传热有很大影响。随着基体材料热导率的降低，翅片对相变材料熔化速率的增强作用不断增加。例如，对于金属钛基体材料，当翅片被嵌入多孔结构中时，相变材料完全熔化时间减少了24.1%。总之，本研究使我们能够很好地理解相变传热机理，并为增材制造混合翅片-点阵结构设计提供了必要的实验数据。

太阳能与燃料电池技术相结合产生的合成气燃料是未来绿色能源解决碳中和问题的一种很有前景的方法。本文设计了一种新型太阳能驱动固体氧化物电解槽系统，该系统集成了余热系统以制备合成气。太阳能光伏和抛物线槽集热器共同驱动固体氧化物电解槽，以提高系统效率。建立了各部件的热力学模型，并进行了能量、（火用）和（火用经济）分析，以评估系统的性能。在设计工况下，太阳能光伏发电由于其转换效率较低，占总（火用）损失的88.46%。经济性分析表明，燃料电池组件的经济性系数较高，为89.56%，这是因为其投资成本较大。讨论了电流密度、工作温度、压力和摩尔分数等关键参数对系统性能的影响。结果表明，当SOEC的温度、压力和水蒸气摩尔分数分别为1223.K、0.MPa和50%时，最佳能量效率和（火用）效率分别为19.04%和19.90%。

Oxidation of acetylene (C2H2) has been investigated in a high-pressure jet-stirred reactor (HP-JSR) with equivalence ratios Φ=0.5, 1.0, 2.0 and 3.0 in the temperature range of 650 K–900 K at 1.2 MPa. 18 products and intermediates were analyzed qualitatively and quantitatively by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Generally, with Φ increasing, the production of intermediates increases significantly. CH₄, C₂H₄, C₂H₆, C₃H₆ and C3H8 were important intermediates, which were formed abundantly at Φ=3.0. Sufficient light hydrocarbon intermediates could be an important reason for significant formation of cyclopentadiene, benzene, toluene and styrene at Φ=3.0. A detailed kinetic mechanism consisting of 299 species and 2041 reactions has been developed with reasonable predictions against the present data and previous results obtained at 0.1 MPa. According to flux and sensitivity analysis, H and OH radicals play important roles in the consumption of C₂H₂. The combinations among light hydrocarbons and their free radicals are the main generation pathways of aromatics. C₃H₃, IC₄H₅ and AC3H5 are important precursors for the formation of aromatics. By comparing the results of atmospheric pressure and high pressure, it can be found that increasing the pressure is conducive to fuel consumption and aromatics generation.

采用高效、紧凑、灵活的超临界二氧化碳（sCO₂）布雷顿循环动力系统有助于提升核动力船舶性能。本文旨在设计并提出适用于核动力船舶的sCO₂循环系统，并对几种核动力sCO₂循环系统方案的热力学效率、设备成本、设备体积和系统部分负荷性能进行了评估。此外，本文还研究和比较了系统采用四种不同的负荷跟随策略时的热力学性能。结果表明，基于部分冷却循环的系统不仅具有较高的设计热效率和较小的设备体积、设备成本，还能在部分负荷工况下保持相对较高的热效率。采用同时调节透平和压缩机转速的负荷跟随策略可以使压缩机远离喘振区，并使循环系统在部分负荷时更加灵活高效。

研究熔盐在微米尺度下的熔化过程对于探究固液相变机理至关重要。本文提出了一种新颖的实验装置及实验分析方法，研究了太阳盐在微米尺度下1-10 °C/min三种加热速率下的熔化过程。重点研究了熔盐颗粒的固液相边界形貌结构和相转变动力学。同时，研究了不同加热速率下液体分数、温度和时间之间的关系式。通过可视化实验装置捕捉了固液相边界形貌结构，并获得了非等温相变过程中的瞬时液体体积分数。然后，提出了温度与液体体积分数之间的关联式，揭示了不同加热速率下固液相边界随温度变化的演变规律。此外，通过引入常数 (V_a,b)，建立了非等温相变动力学方程，并研究了更多动力学参数，如 lgV_a,b 和 -lgV_a,b/b。结果表明，对于太阳盐，指数 b 对不同加热速率并不敏感，范围为 3-5。然而，加热速率会影响 V_a,b 的值，并呈现出正相关关系。此外，通过提出的改进实验测试方法，可以快速预测 1-10 °C/min 范围内不同加热速率下的非等温相转变动力学方程。该研究填补了微米尺度下熔盐固液相转变机理的研究空白，为今后的研究提供了重要指导。