Experimental Thermal and Fluid Science最新文献_第5页

Experimental investigation of the cooling effectiveness of a leading-edge showerhead configuration with counter-inclined compound holes under the influence of freestream turbulence 自由流湍流影响下反倾斜复合孔前缘花洒冷却效果的实验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-11-07 DOI: 10.1016/j.expthermflusci.2025.111638

Xiyuan Liang , Tong Ye , Xinyu Wang , Lin Ye , Cunliang Liu , Xiying Niu

To enhance the film cooling effectiveness of the leading-edge showerhead on turbine vanes, combined compound angle configurations of film holes were incorporated into the cooling structure design. Pressure-sensitive paint (PSP) technology was used to measure the film cooling effectiveness under various momentum flux ratios ranging from 0.09 to 6.04 and the mainstream turbulence intensity ranging from 2.03 %∼23.58 %. The effects of the momentum flux ratio and mainstream turbulence intensity were compared. The results revealed that the effect of the mainstream turbulence intensity on the film cooling effectiveness at the leading-edge was related to the momentum flux ratio. For the vane leading-edge pressure side, the effect of mainstream turbulence intensity on the film cooling effectiveness was related to the momentum flux ratio. Under a low momentum flux ratio, an increase in mainstream turbulence intensity led to a sharp decline in the film cooling effectiveness, resulting in a maximum reduction of 52.5 % in the area-averaged film cooling effectiveness on the pressure side. When the momentum flux ratio was high, the increased mainstream turbulence intensity enhanced the energy dissipation of the cooling jet, thereby improving the film cooling performance in this region, with a maximum increase of 13.8 % in the film cooling effectiveness. As for the vane leading-edge suction side, the film cooling effectiveness decreases with increasing mainstream turbulence intensity, with a maximum reduction of 36.9 %. Moreover, within the varied range of mainstream turbulence intensities and momentum flux ratios studied in this paper, an increase in the film hole compound angle improved the film cooling effectiveness and relieved the degree of reduction in the film cooling effectiveness caused by the film jet blown off. However, for the pressure side, excessively large film hole compound angle did not significantly improve the film cooling effectiveness. In contrast, to ensure good film cooling characteristics, larger compound-angle film holes can be designed on the vane leading-edge suction side, whereas smaller compound-angle film holes can be created on the vane leading-edge pressure side.

为了提高涡轮叶片前缘淋喷头的气膜冷却效果，在冷却结构设计中采用复合角度的膜孔组合形式。在动量通量比为0.09 ~ 6.04，主流湍流强度为2.03% ~ 23.58%的条件下，采用压敏涂料（PSP）技术测量了气膜冷却效果。比较了动量通量比和主流湍流强度的影响。结果表明，主流湍流强度对前缘气膜冷却效果的影响与动量通量比有关。对于叶片前缘压力侧，主流湍流强度对气膜冷却效果的影响与动量通量比有关。在低动量通量比下，主流湍流强度的增加导致气膜冷却效率急剧下降，压力侧面积平均气膜冷却效率最大下降52.5%。当动量通量比较高时，主流湍流强度的增加增强了冷却射流的能量耗散，从而改善了该区域的气膜冷却性能，气膜冷却效率最大提高了13.8%。叶片前缘吸力侧的气膜冷却效率随着主流湍流强度的增加而降低，最大降幅为36.9%。此外，在本文研究的不同主流湍流强度和动量通量比范围内，增大膜孔复合角提高了膜冷却效率，缓解了被吹出的膜射流导致的膜冷却效率降低的程度。而对于压力侧，过大的膜孔复合角并没有显著提高膜冷却效果。为了保证良好的气膜冷却特性，可以在叶片前缘吸力侧设计较大的复合角膜孔，在叶片前缘压力侧设计较小的复合角膜孔。

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引用次数: 0

Laser induced cavitation bubble and shockwave measurements with fiber optical hydrophone very close to origin 激光诱导空化泡和冲击波的近源光纤水听器测量

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-11-07 DOI: 10.1016/j.expthermflusci.2025.111655

Ž. Lokar, J. Petelin, D. Horvat, V. Agrež, R. Petkovšek

Laser induced breakdown in water generates shockwaves and cavitation bubble, both originating from the breakdown of the plasma. The dynamics of a shockwave propagating from a point source changes significantly with distance. In spherical geometry without energy loss, the energy spreads out in accordance with the inverse square law, the pressure decreases proportionally with distance. Thus, closer to the shockwave source a more pronounced shockwave dynamics is expected. A fast, robust and precisely positioned sensor with a small detection area is needed to accurately measure the shockwave pressure in such conditions. A single mode optic fiber-based hydrophone meets these requirements. In addition to measuring the shockwave induced change in light reflectance from the fiber tip, the fiber optic hydrophone, when positioned very close to the breakdown bubble, picks up some of the light which exits the sensor and is reflected from the bubble wall. Due to bubble growth, this results in an oscillating interference signal. We introduce signal processing to distinguish between the two signals, originating from different phenomena but captured in a single oscilloscope trace. While using only FFT processing to remove the oscillations from the signal does not preserve the shockwave properties properly, the introduced local filtering procedure allows for correct separation of the two overlapping contributions to the waveform. The transient interference signal allowed for extraction of tens of bubble wall velocity data points in the first 100 ns of a single bubble growth event, showing the very early bubble growth behaviour. After this contribution was eliminated from the signal, the shockwave pressure trace was successfully assessed at very small distances, down to the situation where the hydrophone nearly touched the plasma edge. Pressure trace allowed for extraction of various parameters such as maximum pressure, risetime, shockwave energy and pressure impulse. The shockwave energy was measured to decay as 6.5 dB/mm for distances above 50 μm.

激光在水中的击穿产生冲击波和空化泡，两者都源于等离子体的击穿。从点源传播的冲击波的动力学随距离的变化而显著变化。在无能量损失的球面几何中，能量按平方反比定律扩散，压力随距离成比例减小。因此，在靠近激波源的地方，预期会有更明显的激波动力学。在这种条件下，需要一种快速、坚固、定位精确、检测面积小的传感器来精确测量冲击波压力。单模光纤水听器可以满足这些要求。除了测量来自光纤尖端的冲击波引起的光反射率变化外，当光纤水听器非常靠近破裂气泡时，它还会拾取一些从传感器流出并从气泡壁上反射的光。由于气泡生长，这导致振荡干扰信号。我们引入信号处理来区分两种信号，这两种信号来自不同的现象，但在单个示波器跟踪中被捕获。虽然仅使用FFT处理从信号中去除振荡并不能正确地保留冲击波特性，但引入的局部滤波过程允许正确分离对波形的两个重叠贡献。瞬态干扰信号允许在单个气泡生长事件的前100纳秒内提取数十个气泡壁速度数据点，显示出非常早期的气泡生长行为。从信号中消除这一贡献后，在非常小的距离内成功地评估了冲击波压力轨迹，直到水听器几乎接触等离子体边缘的情况。压力跟踪允许提取各种参数，如最大压力，上升时间，冲击波能量和压力脉冲。在距离大于50 μm时，冲击波能量衰减为6.5 dB/mm。

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引用次数: 0

Bubble breakup in the microchannels with a long constriction 气泡在微通道中破裂，具有较长的收缩

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-11-03 DOI: 10.1016/j.expthermflusci.2025.111640

Baolei Jiao , Lifeng Chen , Xuemin Yan , Xiaoda Wang

Bubble dynamics within contracting microchannels exhibit profound complexity, receiving a long-standing research focus. This study systematically investigated bubble behaviors in elongated constrictions both in the 2D and 3D pore-throat combinations. A high-speed imaging device captured the bubble evolution in structurally diverse constrictions, while the effects of gas–liquid flow rates and fluid properties were quantified to establish transitional boundaries between distinct flow regimes. Bubble breakup—a typical flow pattern—demonstrated notable disparities between 2D and 3D configurations. To elucidate these differences, interfacial dynamics were tracked to analyze breakup mechanisms during the constriction traversal. In both dimensional systems, bubble breakup was primarily driven by the drawing and squeezing forces exerted by the continuous phase. Crucially, in the 3D pore-throat combination, the intensified drawing forces and prolonged squeezing forces, significantly enhanced breakup propensity. Mutual squeezing among the daughter-bubbles induced asynchronous breakup events, yielding non-uniform daughter-bubble size distributions. A power-law relationship characterized the dependence of mean daughter-bubble size on the mother-bubble length and the superficial flow velocity, with the exponent critically governed by microchannel geometric parameters. This work will advance fundamental understanding of bubble breakup mechanics in confined geometries and provide actionable insights for microfluidic device design.

收缩微通道内的气泡动力学表现出深刻的复杂性，长期以来一直是研究的焦点。本研究系统地研究了二维和三维孔喉组合中细长收缩条件下的气泡行为。高速成像设备捕捉到了不同结构收缩条件下气泡的演化过程，同时对气液流速和流体性质的影响进行了量化，以建立不同流动状态之间的过渡边界。气泡破裂是一种典型的流动模式，在2D和3D形态之间表现出明显的差异。为了阐明这些差异，我们跟踪了界面动力学，分析了收缩穿越过程中的破裂机制。在这两个维度系统中，气泡破碎主要是由连续相施加的拉伸和挤压力驱动的。关键是，在三维孔喉组合中，拉拔力的增强和挤压力的延长显著增强了破裂倾向。泡沫之间的相互挤压导致了非同步破裂事件，产生了不均匀的泡沫大小分布。平均气泡大小与母泡长度和表面流速呈幂律关系，指数受微通道几何参数的严格控制。这项工作将促进对受限几何气泡破裂力学的基本理解，并为微流控装置的设计提供可行的见解。

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引用次数: 0

Study on the de-icing performance of wind turbine blades based on PCMS-C14 coating combined with electrothermal heating 基于PCMS-C14涂层结合电热加热的风电叶片除冰性能研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-11-01 DOI: 10.1016/j.expthermflusci.2025.111639

Zheng Sun , He Shen , Yiting Wang , Haotian Zheng , Fang Feng , Yan Li

Icing on wind turbine blades severely compromises turbine operation, while existing standalone anti-icing and de-icing methods exhibit inherent limitations. This study experimentally investigates the synergistic de-icing performance of wind turbine blades using the PCMS-C14 phase-change microcapsule coating, developed independently by the Wind Energy Laboratory at Northeast Agricultural University, combined with electrothermal heating. Experiments were conducted in an icing wind tunnel under controlled parameters: water flow rate (60 mL/min), ambient temperatures (−5 °C, −10 °C, −15 °C), incoming wind speeds (3 m/s, 6 m/s, 9 m/s), and energy flux densities (8 kW/m², 10 kW/m², 12 kW/m²). Results demonstrate that although higher wind speeds and lower temperatures increase de-icing energy demand, the hybrid coating-electrothermal approach significantly outperforms pure electrothermal de-icing across all tested scenarios: the highest energy-saving efficiency of 19.23 % was achieved at an energy flux density of 10 kW/m²; an energy reduction of 21.5 % was observed at an ambient temperature of −10 °C; and the optimal energy-saving effect was obtained at a wind speed of 6 m/s. This integrated strategy effectively reduces de-icing time by 25–68 s, lowers energy consumption by 12.89 % to 21.5 %, and significantly improves de-icing uniformity and thermal management stability. This study provides a practical solution and experimental basis for enhancing the energy efficiency and operational reliability of wind turbines in cold regions.

风力涡轮机叶片结冰严重影响涡轮机运行，而现有的独立防冰和除冰方法具有固有的局限性。本研究利用东北农业大学风能实验室自主研发的PCMS-C14相变微胶囊涂层，结合电热加热，对风力发电机叶片协同除冰性能进行了实验研究。实验在结冰风洞中进行，控制参数为：水流速度（60 mL/min）、环境温度（- 5℃、- 10℃、- 15℃）、来风速度（3 m/s、6 m/s、9 m/s）和能量通量密度（8 kW/m2、10 kW/m2、12 kW/m2）。结果表明，虽然较高的风速和较低的温度增加了除冰的能源需求，但在所有测试场景中，混合涂层-电热方法的节能效果明显优于纯电热除冰：在能量通量密度为10 kW/m2时，节能效率最高，达到19.23%；在环境温度为- 10℃时，能量降低21.5%；风速为6 m/s时，节能效果最佳。该综合策略可有效缩短除冰时间25 ~ 68 s，降低能耗12.89% ~ 21.5%，显著提高除冰均匀性和热管理稳定性。该研究为提高寒冷地区风力发电机组的能效和运行可靠性提供了切实可行的解决方案和实验依据。

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引用次数: 0

Quantification and mitigation of uncertainties in thermal conductivity measurements using a modified ASTM D5470 thermal resistance tester 使用改进的ASTM D5470热阻测试仪对热导率测量中的不确定性进行量化和降低

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-11-01 DOI: 10.1016/j.expthermflusci.2025.111636

Chinmaya Joshi , Clancy Milam , Stephen Pierson , Ying Sun , Jared Berg , Han Hu

In this paper, we have investigated the effect of thermal interface materials (TIMs) on the accuracy and uncertainty of thermal conductivity measurements. A modified ASTM D5470 thermal resistance tester (TRT) has been developed to measure the out-of-plane thermal conductivity of pyrolytic graphite (PG) and titanium grade 2 (TiG2) with and without TIMs. Compared to the ASTM D5470 standard, this modified design uses three thermocouples per side to support regressive analysis of the temperature profile and quantifies the uncertainty of the measurements with and without TIMs. Nine PG samples and four TiG2 samples of varying thickness have been tested to obtain thermal resistance as a function of sample thickness. The steady-state temperature profiles were used for heat flux and thermal resistance calculation. The results reveal that TIMs significantly reduce measurement uncertainty for both samples, i.e., 38.8 % for TiG2 and 27.8 % for PG. The effect of TIMs on the measurement accuracy diverges, with a far more pronounced effect on TiG2 than PG. This can be owed to the higher out-of-plane thermal conductivity of TiG2 (∼16.2 W/m-K) than PG (∼2 W/m-K). Contact resistance is expected to play a more critical role in tests of materials with higher thermal conductivity, and TIMs can effectively mitigate contact resistance. For lower conductivity materials, the weight of contact resistance is lower, and the effect of TIMs is thus less pronounced. This work establishes a robust framework for quantifying and mitigating uncertainties in thermal conductivity measurements, which will lead to more accurate characterization of materials for the design and qualification of advanced thermal management systems in aerospace, electronics, and energy applications.

本文研究了热界面材料（TIMs）对导热系数测量精度和不确定度的影响。研制了一种改进的ASTM D5470热阻测试仪（TRT），用于测量有或没有TIMs的热解石墨（PG）和2级钛（TiG2）的面外导热系数。与ASTM D5470标准相比，这种改进的设计每侧使用三个热电偶来支持温度分布的回归分析，并量化有和没有TIMs的测量的不确定性。对9个不同厚度的PG样品和4个不同厚度的TiG2样品进行了测试，得到了热阻与样品厚度的关系。用稳态温度曲线计算热流密度和热阻。结果表明，TIMs显著降低了两种样品的测量不确定度，即TiG2的测量不确定度为38.8%，PG的测量不确定度为27.8% . TIMs对测量精度的影响存在差异，TiG2的影响远比PG的明显，这可能是由于TiG2的面外导热系数（~ 16.2 W/m-K）高于PG （~ 2 W/m-K）。接触电阻有望在高导热材料的测试中发挥更关键的作用，而TIMs可以有效地降低接触电阻。对于电导率较低的材料，接触电阻的重量较低，因此TIMs的影响不太明显。这项工作为量化和减轻热导率测量中的不确定性建立了一个强大的框架，这将导致更准确的材料表征，用于航空航天，电子和能源应用中的先进热管理系统的设计和鉴定。

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引用次数: 0

Analysis of scour dynamics and turbulence structures at a sequence of repelling spur dikes using higher-order moments, turbulent kinetic energy fluxes, and quadrant analysis 利用高阶矩、湍流动能通量和象限分析，对排斥性直堤序列的冲刷动力学和湍流结构进行分析

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-10-30 DOI: 10.1016/j.expthermflusci.2025.111637

Sandeep Kumar, Prashanth Reddy Hanmaiahgari

This study aims to understand local scour dynamics and turbulence characteristics around the head of repelling spur dikes by analyzing sediment bed morphology, higher-order turbulence statistics, turbulent kinetic energy fluxes, and quadrant-based turbulence events, which remain insufficiently understood in the context of these river training structures. The flow field was measured using Vectrino ADV under two Reynolds numbers (

R_{e}

) of 48,508 and 42579. The sediment bed topography exhibited distinct patterns, with maximum scour depth (

d_{s})

of 0.48 h (

h = flow depth

) and 0.55 h at the first spur dike in both scenarios, and at the second spur dike, greater erosion occurred at a higher Reynolds number. Higher-order turbulence moments

M_{12}, M_{21}, M_{30}

and

M_{03}

revealed ejections followed by primarily sweep, outward, and inward events near the bed. The

M_{03}

magnitude exhibited greater variation primarily with ejection events; these phenomena were shaped by bed morphology. At both Reynolds numbers, the sweep events dominate ejection events at first and second spur dikes near-bed zone. In contrast, inward and outward events prevailed at the third spur dike. Turbulent kinetic energy flux,

F_{ku}

and

F_{kw}

revealed greater magnitudes at the first and second spur dikes with dissimilarity in their sign. A significantly high vorticity is observed immediately u/s and d/s of the first spur dike throughout the depth. Quadrant analysis confirmed energetic activity near the bed zone dominated by sweep and ejection events governed turbulence structures, while the coherent structure near the water surface persisted throughout the test reach but weakened in the downstream.

本研究旨在通过分析沉积物床形态、高阶湍流统计、湍流动能通量和基于象限的湍流事件，了解在这些河流训练结构背景下仍未得到充分了解的排斥性直堤头部周围的局部冲刷动力学和湍流特征。在雷诺数Re为48,508和42579时，采用Vectrino ADV对流场进行了测量。两种情况下，第1支脉的最大冲刷深度（ds）分别为0.48 h （h=流深）和0.55 h，第2支脉的最大冲刷深度在较高雷诺数下发生较大的侵蚀。高阶湍流时刻M12，M21，M30和m03显示出抛射，随后主要是在床附近扫向，向外和向内的事件。m03星等的变化主要与喷发事件有关；这些现象是由床层形态形成的。在两种雷诺数下，在第一和第二直堤近层带处，扫射事件主导喷射事件。相比之下，在第三直堤，内向和外向的事件占主导地位。湍流动能通量、Fku和Fkw在第1和第2直堤处表现出较大的量级，但其标志不同。在整个深度处，第一直脉的u/s和d/s涡度都很高。象限分析证实，床带附近的能量活动主要由横扫和喷射事件控制湍流结构，而靠近水面的相干结构在整个测试河段持续存在，但在下游减弱。

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引用次数: 0

Research on the rebound and fusion characteristics of high temperature aluminium droplets impact on aluminium liquid film 高温铝液滴冲击铝液膜的回弹与熔合特性研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-10-26 DOI: 10.1016/j.expthermflusci.2025.111633

Qinrui Xu, Jiang Li, Kang Li, Shihui Cheng

The rebound/fusion characteristics of high-temperature aluminium droplets impact on aluminium liquid film are crucial for accurately predicting the evolution of solid rocket motor slag deposition. In this study, the rebound and fusion characteristics of aluminium droplet impact on aluminium liquid film were systematically investigated through experimental research and direct numerical simulation (DNS). Electromagnetic induction heating and pneumatic driving technology are used to generate high-temperature aluminium droplets, combined with a high-speed camera to capture the impact transient process. For the numerical simulations, we use the Basilisk software with Volume of Fluid model. This model helps us understand how the gas film evolves and how the interfaces interact during droplet impact. The results show that the droplet impact results are dominated by Weber number (We), and the droplets rebound when We ≤ 5.4, while fusion occurs when We > 5.4. This critical condition applies to the dimensionless liquid film thickness of 20 ≤ H* ≤ 30 and the Ohnesorge number of 0.8 ≤ Oh ≤ 1.0 × 10^-3. The numerical simulation results showed that the wall effect was significant in the thin liquid film (H* < 1.5), with an inverted “hump” shape of the gas film and limited liquid film retraction. For thick liquid film (H* ≥ 1.5), the gas film forms an arc-shaped profile. We also establish a formula for the maximum dimensionless penetration depth of the liquid film, based on the Weber and Ohnesorge numbers. Additionally, we propose a prediction model for the rebound and fusion of high-surface-tension droplets on liquid films. This model is based on the liquid film surface arc length and energy analysis. This study reveals the kinetic mechanism of high-surface-tension droplet impact. It provides useful insights for predicting slag deposition in engines and optimizing thermal protection systems.

高温铝液滴冲击铝液膜的回弹/熔合特性对于准确预测固体火箭发动机熔渣过程的演变至关重要。本研究通过实验研究和直接数值模拟（DNS）两种方法，系统研究了铝液滴撞击铝液膜时的回弹和融合特性。采用电磁感应加热和气动驱动技术产生高温铝液滴，结合高速摄像机捕捉冲击瞬态过程。采用流体体积模型的Basilisk软件进行数值模拟。该模型有助于我们了解气膜的演变过程以及液滴撞击过程中界面的相互作用。结果表明：液滴撞击结果以韦伯数（We）为主，当We≤5.4时，液滴发生反弹，当We >； 5.4时，液滴发生融合。该临界条件适用于无量纲液膜厚度为20≤H*≤30，欧内格数为0.8≤Oh≤1.0 × 10-3。数值模拟结果表明，在薄液膜（H* < 1.5）中，壁面效应显著，气膜呈倒“驼峰”形状，液膜收缩有限。对于厚液膜（H*≥1.5），气膜呈弧形。我们还建立了基于Weber和Ohnesorge数的液膜最大无因次渗透深度公式。此外，我们还提出了高表面张力液滴在液体膜上的回弹和融合的预测模型。该模型基于液膜表面弧长和能量分析。本研究揭示了高表面张力液滴撞击的动力学机理。它为预测发动机中的渣沉积和优化热保护系统提供了有用的见解。

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引用次数: 0

Examination of urea water solution spray characteristics in hot cross flow 热交叉流中尿素水溶液喷射特性的检验

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-10-24 DOI: 10.1016/j.expthermflusci.2025.111635

P. Senthilkumar , T.N.C. Anand

Injecting Urea-Water sprays at low pressure into the hot exhaust gas flow stream in the presence of catalysts is one of the most effective ways to reduce NO

_{X}

emissions in diesel engines. The effectiveness of NO

_{X}

conversion is greatly impacted by spray parameters such as droplet size, velocity, dispersion, and homogeneity upstream of the catalyst. For estimating droplet size, Particle/Droplet Image Analysis (PDIA) is a reliable technique, and it has numerous benefits, including the ability to visualize the droplet shape and quantify non-spherical droplets. In this present study, the PDIA and Particle Tracking Velocimetry (PTV) techniques with high pixel resolution were used to look at the size and velocity of the droplets of the urea-water solution (UWS) spray in a heated cross-flow. The results indicate that smaller spherical droplets are located at the top of the spray, whereas the majority of the bigger droplets are non-spherical and present at the bottom. Droplet size decreases as injection pressure and air velocity rise due to improved atomization. Droplet velocity in the flow direction increases with air velocity and decreases with size. The PDIA method has the ability to measure both spherical and non-spherical droplets. When non-spherical droplets are excluded from droplet size measurements, there is a significant difference in the SMD measured, highlighting the importance of using a technique which can measure non-spherical droplets in such sprays. However, since the PDIA method is usually used with low repetition rate cameras, droplets must be captured over a range of imaging times, from the time they begin to appear in the field of view to the time they eventually disappear.

在催化剂存在的情况下，向热废气流中低压注入尿素水喷雾是减少柴油机NOX排放的最有效方法之一。催化剂上游的液滴大小、速度、分散性和均匀性等喷雾参数对NOX转化的有效性有很大影响。对于估计液滴大小，颗粒/液滴图像分析（PDIA）是一种可靠的技术，它有许多优点，包括能够可视化液滴形状和量化非球形液滴。在本研究中，采用高像素分辨率的PDIA和粒子跟踪测速（PTV）技术观察了尿素-水溶液（UWS）喷雾在加热交叉流中的液滴大小和速度。结果表明，较小的球形液滴位于喷雾的顶部，而大多数较大的液滴是非球形的，存在于喷雾的底部。由于雾化效果的改善，液滴尺寸随着喷射压力和空气速度的增加而减小。液滴在气流方向上的速度随气流速度的增大而增大，随粒径的增大而减小。PDIA方法能够同时测量球形液滴和非球形液滴。当在液滴尺寸测量中排除非球形液滴时，测量的SMD存在显着差异，突出了使用一种可以测量此类喷雾中非球形液滴的技术的重要性。然而，由于PDIA方法通常与低重复率相机一起使用，因此必须在一定的成像时间范围内捕获液滴，从它们开始出现在视场中到它们最终消失的时间。

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引用次数: 0

Experimental investigation of flow and heat transfer characteristics in the bend region of matrix channel 基质通道弯曲区流动传热特性的实验研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-10-23 DOI: 10.1016/j.expthermflusci.2025.111632

Arun Chand , Nishab Ali , Andallib Tariq

Matrix cooling is gaining attention as an advanced internal cooling strategy for gas turbines, offering both enhanced mechanical integrity and superior heat transfer. However, the aerothermal behavior in bend regions, especially downstream of the matrix, remains insufficiently explored. This study presents a detailed experimental investigation of flow dynamics and heat transfer across the bend section that occurs downstream of the matrix channel. Two matrix configurations, i.e., (i) 3-subchannel (3SC) and (ii) 4-subchannel (4SC), are systematically studied at Reynolds numbers (Re) of 5,000, 7,500, and 10,000. High-resolution particle image velocimetry (PIV) and liquid crystal thermography (LCT) techniques have been used for multi-plane aerothermal measurements to elucidate the correlation of complex flow with thermal fields. Results indicate that the matrix emanates the corotating vortices, leading to spatially non-uniform secondary flows, including the emergence of Dean-type vortices at the downstream bend. In particular, the 4SC matrix promotes stronger vortex-driven mixing, yielding significant local and average heat transfer enhancement in the bend region. At Re = 10,000, the 4SC channel achieves a peak heat transfer augmentation of 133 % relative to a smooth baseline, while incurring only a slight increase in friction factor. Across all conditions, the 3SC and 4SC configurations deliver thermal performance factors (TPF) of up to 2.09 and 2.34, respectively. These findings support the potential of matrix cooling to deliver high thermal effectiveness in next-generation internal cooling applications.

矩阵冷却作为一种先进的燃气轮机内部冷却策略正受到越来越多的关注，它既提供了增强的机械完整性，又提供了优越的传热。然而，弯曲区域的气动热行为，特别是在基体的下游，仍然没有得到充分的探索。本研究对基质通道下游弯曲段的流动动力学和传热进行了详细的实验研究。在雷诺数（Re）为5000、7500和10000时，系统地研究了(i) 3-子通道（3SC）和（ii） 4-子通道（4SC）两种矩阵构型。高分辨率粒子图像测速（PIV）和液晶热成像（LCT）技术被用于多平面气动热测量，以阐明复杂流动与热场的关系。结果表明，该矩阵产生旋转涡，导致二次流在空间上不均匀，包括在下游弯道处出现迪恩型涡。特别是，4SC矩阵促进了更强的涡驱动混合，在弯曲区域产生显著的局部和平均传热增强。在Re = 10,000时，4SC通道相对于平滑基线实现了133%的峰值传热增加，而摩擦系数仅略有增加。在所有条件下，3SC和4SC配置的热性能系数（TPF）分别高达2.09和2.34。这些发现支持了基质冷却在下一代内部冷却应用中提供高热效率的潜力。

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引用次数: 0

Combustion of NH3/CH4 mixtures in a swirl burner: Study of non-premixed flames with radial fuel injection 旋流燃烧器中NH3/CH4混合物的燃烧：径向喷射非预混火焰的研究

IF 3.3 2区工程技术 Q2 ENGINEERING, MECHANICAL

Experimental Thermal and Fluid Science

Pub Date : 2025-10-21 DOI: 10.1016/j.expthermflusci.2025.111630

Antoine Morel, Toufik Boushaki

The transition to renewable energy is essential in addressing climate change. While natural gas plays a significant role in this transition, it still produces CO₂ emissions. Ammonia (NH₃) is being investigated as a promising alternative fuel. However, ammonia combustion presents several technical challenges, such as low flame velocity, limited calorific value, difficulties with flame stabilization, and high NOx emissions. This study examines the impact of ammonia addition to methane, equivalence ratio, and swirl number on pollutant emissions (NO, CO, CH₄, and CO₂), exhaust gas temperature, and flame stability. Experiments are carried out using a swirl burner with a radial fuel injection in a 1-meter high combustion chamber. The burner consists of two concentric tubes, with the inner tube supplying fuel and the outer tube supplying air. The fuel is injected radially through eight holes at the burner exit. The ammonia fraction ranges from 0 to 100 %, the equivalence ratio from 0.8 to 1.0, and the swirl number from 0.8 to 1.4, with a constant flame power of 10 kW. Emissions of NO, CO, CH₄, and CO₂ are measured in the dry exhaust gases using a multi-gas analyzer, inside chamber temperatures are measured and the flame structure is analyzed via OH* and NH₂* chemiluminescence and velocity measurements by LDA technique. The results show that both the swirl number and equivalence ratio significantly alter flame geometry, affecting combustion zones and flame height. Axial velocity measurements indicate that the recirculation zone shrinks with ammonia addition, while a high swirl number increases axial velocity, promoting ammonia combustion and upstream flame propagation. Up to 30 % ammonia, the flame remains stable, but higher ammonia levels lead to fluctuations in stabilization. High ammonia content in the fuel mixture results in reductions of NO, CO, and CO₂ emissions, though there is a potential increase in unburned gases. As expected, the inside chamber temperatures decrease as the ammonia fraction increases.

向可再生能源过渡对于应对气候变化至关重要。尽管天然气在这一转变中发挥了重要作用，但它仍会产生二氧化碳排放。氨（NH3）作为一种有前途的替代燃料正在被研究。然而，氨燃烧存在一些技术挑战，如火焰速度低、热值有限、火焰稳定困难以及NOx排放高。本研究考察了氨加甲烷、当量比和旋流数对污染物排放（NO、CO、CH4和CO2）、废气温度和火焰稳定性的影响。在1米高的燃烧室中，采用径向喷油的旋流燃烧器进行了实验。燃烧器由两根同心管组成，内管供给燃料，外管供给空气。燃料通过燃烧器出口处的八个孔径向注入。氨分数为0 ~ 100%，当量比为0.8 ~ 1.0，旋流数为0.8 ~ 1.4，火焰功率为10kw。利用多气体分析仪测量了干燥废气中NO、CO、CH4和CO2的排放量，测量了室内温度，通过OH*和NH2*化学发光分析了火焰结构，并利用LDA技术测量了速度。结果表明，旋流数和等效比都能显著改变火焰几何形状，影响燃烧区域和火焰高度。轴向速度测量表明，随着氨的加入，再循环区缩小，而高旋流数增加轴向速度，促进氨燃烧和上游火焰传播。高达30%的氨，火焰保持稳定，但较高的氨水平导致稳定波动。燃料混合物中的高氨含量导致NO， CO和CO2排放量的减少，尽管未燃烧气体的潜在增加。正如预期的那样，随着氨馏分的增加，室内温度降低。

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引用次数: 0