Heat loss and thermoelectric generator design

With the object of evaluating its importance to thermoelectric generator design, heat loss is introduced into the standard thermoelectric generator design theory. The theory for both the constant hot and cold junction temperatures model and the constant heat input model are so modified. The modification is first order and, therefore, is limited to small leg heat-transfer coefficients. Numerical results using representative properties show that significant differences can exist between the optimum geometry and performance of a generator idealized as lossless and those of a generator designed by the modified theory. The largest differences occur with the constant heat input model.     

Tuning the electronic and thermal transport behaviors of metal-dispersed Ti2O3 composites derived by metal–insulator transition

Thermal management requires an understanding of the relations among the thermal energy transfer, electronic properties, and structures of thermoconductive materials. Here, we enhanced the metal–insulator transition (MIT)-induced effect on the thermal conductivities of microstructure-controlled Ti₂O₃ composites containing W as a thermal conductive filler at approximately 450 K. To change the electronic and thermal transport properties, we varied the particle radii of the conductive phases in the raw material. The change in the calculated electronic thermal conductivity relative to the electrical conductivity of the W_x(Ti₂O₃)_1?x composite was enhanced by compounding the material. When x was reduced from 50 vol% to 20 vol% and the W particle diameter was reduced from 150 μm to 5 μm, the variation in the estimated electronic thermal conductivity of the W_x(Ti₂O₃)_1?x composite was increased by a factor of 2.01. The total thermal conductivity was also changed by the MIT. At x = 50 vol% and a W particle diameter of 5 μm, the maximum thermal conductivity change was 6.34 times larger than that of pure Ti₂O₃. The detailed relation between the MIT-induced changes in thermal transport and the microstructure were elucidated in classical effective medium approximations.     

极小展弦比跨音速汽轮机叶片非定常流动机理研究

随着能源效率需求的不断提升,汽轮机叶片的设计在不同应用场景中展现出显著的多样性。大展弦比叶片因端壁损失较低、流动效率较高,广泛用于传统燃气轮机和工业汽轮机。然而,在空间受限或特殊工况下,例如航空发动机的高负荷小型化设计、船舶推进系中的高压级和调节级的应用场景,小展弦比叶片因其紧凑设计成为首选。尽管如此,小展弦比叶片在性能上仍存在明显短板。端壁二次流和混合损失等问题显著增加了能量损失,严重影响整体性能。本文基于跨音速条件下的极小展弦比汽轮机叶片,采用延迟脱体涡模拟（DDES）方法,深入研究了小展弦比叶片的流动特性,重点分析了涡流结构、激波与边界层干扰引发的流动分离及其对性能的影响。研究发现,小展弦比叶片虽然具有结构紧凑的优势,但其能量损失主要集中在尾缘区域,且尾迹涡、端壁涡与激波的相互作用是损失增加的关键因素。结果表明,DDES方法在捕捉小展弦比叶片中小尺度涡流和瞬时现象方面表现出显著优势,能够更准确地反映激波的平均扰动效应及涡流对整体性能的影响。此外,本文还提出了针对极小展弦比叶片性能优化的未来方向,包括优化尾缘形状、调整端壁区域设计、减少激波干扰以及控制边界层分离等略。本研究为小展弦比叶片的性能优化提供了理论支持,同时展示了DDES方法在复杂流动模拟中的巨大优势。未来研究将进一步验证这些优化方案的可行性,以有效降低能量损失并提升汽轮机的整体效率。     

有芯感应炉熔沟感应加热与流场数值模拟

以某厂1吨双环式熔沟有芯感应炉为研究对象,通过ANSYS仿真软件耦合k–?标准方程和磁流体力学模型(MHD)建立了数值仿真模型,研究了熔沟内流场状态与温度分布,及不同熔沟间距与不同宽厚比对熔沟功率密度和熔沟顶面流速的影响。结果表明熔沟间距在275 mm~345 mm变化时,熔沟热值最大,约为410 kJ,功率密度为0.018 W/mm³;而随着宽厚比增加,熔沟热值逐渐下降。流场结果显示熔沟两侧沟道内熔体流速较快,并以螺旋式从熔沟两侧流向炉膛,到达熔沟顶面时速度最高达到0.297 m/s,炉膛内熔体在重力作用下流入中心沟道,下行熔体受到两侧熔沟射流的影响在熔沟上部形成纵向涡心。从熔沟中心沟道上方开始,沿着熔沟方向向熔沟两侧移动,熔体温度逐渐升高,在熔沟两侧拐角处最大,最大温差为12.9 ℃。     

EFFECT OF GEOMETRIC PARAMETERS ON VENTILATION PERFORMANCE IN A DRY ROOM

ABSTRACT

The characteristics of moisture ventilation in a dry room are studied numerically. The effects of three important parameters: the positions of outlets, the aspect ratio (β) of horizontal section and the air exchange rate (N), are analyzed in terms of the scales of ventilation efficiency. Ventilation performance is evaluated by varying the aspect ratio and the air exchange rate for the four different outlet arrangements. It is found that the ventilation performance is improved when the aspect ratio in the transverse arrangement of outlets is decreased. Ventilation efficiency reaches its highest value when β is set to be 4 in the longitudinal arrangement of outlets. Regardless of the aspect ratio, the upper arrangement of the outlets shows a better ventilation performance than the lower arrangement. For all geometrical models and aspect ratios investigated in this study, the increase of the air exchange rate for improving the ventilation performance is only valid up to 60 h^?1.     

基于AOP的Web应用框架的研究与实现

在研究面向方面编程思想的基础上,提出了一种Web应用框架。论述了采用J2EE过滤器实现关注点引擎,通过配置文件实现初始化并在运行时动态组装系统关注点和核心关注点的原理与方法。基于框架设计并实现了毕业论文管理系统,实践表明了框架的正确性与有效性。     

双向内外管压差流量计关键参数优化

针对现有的对双向内外管压差流量计关键结构的参数研究准确度不足的问题,在以往研究的基础上,提出了一种新的评价指标压损差,压损差为节流件内外的压差信号和前后压损的差值.相较于以往的压损比,更加科学合理.通过分析,确定影响双向内外管压差流量计性能指标的三个主要参数为异径比k、扩散角θ和节流件的大径R.通过三因素三水平的二次回...     

双极性电泳法的微细中空电极侧壁绝缘层制备

针对孔径(100～200)μm高深宽比微细孔电解加工中,电极侧壁绝缘层在电解液冲击和气泡撕裂中易损伤/脱落等问题,提出一种基于丙烯酸环氧树脂双极性电泳法的微细中空电极侧壁绝缘制备工艺.通过工艺参数优化后,利用所制备的侧壁绝缘电极,开展加工对比实验,结果表明双极性电泳法所制备的侧壁绝缘层,具有较高的致密性、均匀性、耐久性...