复合冲击和复合旋流冷却特性的对比研究

针对应用旋流冷却和气膜冷却对涡轮叶片前缘区进行冷却系统设计的科学命题,首次建立了包含冷气腔、冲击/旋流腔、气膜孔和燃气主流通道的复合冲击和复合旋流冷却模型,利用数值方法在相同几何和气动条件下对比了复合冲击和复合旋流冷却的流动换热特性.研究结果表明:冲击孔/旋流喷嘴流量沿X方向逐渐增大,吹风比沿X方向先增大后减小.复合冲击冷却的气膜孔流量和吹风比沿X方向略有增大,复合旋流冷却气膜孔流量和吹风比沿X方向减小.复合旋流冷却平均Nu比复合冲击冷却提升13.0%.气膜孔会扰动冷气流动,使附近小范围区域Nu提升.与复合冲击冷却相比,复合旋流冷却气膜孔的冷气流量和速度大,肾型对涡强度高,绝热气膜冷却效率减小.     

湍流度对单排圆孔及后扩孔气膜冷却的影响

通过传热-传质类比法研究了湍流度对单排圆柱孔及后扩孔气膜冷却效率的影响.计算结果表明,小吹风比M=0.5时,圆柱孔与后扩孔的壁面冷却效率相当,湍流度趋向于在整个下游区域使冷却效果恶化;大吹风比M=2时,后扩孔产生的壁面气膜冷却效率的提高明显,而湍流度的提高强化了冷却剂向壁面的扩散,削弱了冷却气膜脱离壁面的现象,趋向于在整个下游区域提升冷却效率.     

气膜和冲击复合冷却结构耦合传热数值研究

本文采用数值方法研究了气膜和冲击复合冷却结构的耦合传热和综合冷效。复合冷却平板模型布置有两个交错气膜孔和若干排冲击孔,气膜孔和冲击孔均采用圆柱孔型。分别研究了吹风比和冷气量分配对综合冷效、流场结构和对流换热特性等的影响规律,结果表明:复合冷却综合冷效明显受到吹风比影响;适当调节冷气量的分配,能够明显提高综合冷效。     

横流下前向与反向复合角沟槽孔气膜冷却效率

利用红外热像技术实验分析了横流比(Cr=0.08,0.16)和吹风比(BR=0.5,1.0,2.0)对横向沟槽内反向和前向复合角气膜孔的气膜覆盖特性的影响。数据对比指出:沟槽、复合角度和反向冷气出流对于前向简单孔所发生的射流分离现象存在明显的抑制作用,有利于提高气膜覆盖。复合角度在大腔进气(Cr=0)时会引起冷却效率偏转,而横流进气可以有效抑制冷却效率的偏转,使得气膜在横流方向分布更加均匀。在相同横流比时,小吹风比导致反向孔的整体气膜覆盖优于前向孔,大吹风比下情况相反。小横流比时,120°沟槽孔在各吹风比呈现出最好的气膜覆盖,较简单角孔而言,效率提高约42%;大横流比时,60°沟槽孔在各吹风比呈现出最好的气膜覆盖,效率提高约26%。     

透平静叶叶身全覆盖气膜冷却有效度实验研究

燃气轮机透平叶片气膜冷却性能受到吹风比、曲率、压力梯度等多种因素的影响。本文采用压力敏感漆(PSP)技术研究了燃气轮机静叶气膜冷却的冷却性能,实验测量了不同吹风比下全覆盖气膜的冷却有效度,并结合单排孔冷却的实验结果进行分析。结果表明：随吹风比增大,压力面冷却有效度递增,吸力面受曲率和压力梯度影响,冷却有效度先递增后递减;前缘射流在低吹风比下附壁效果较好,高吹风比下由于复合角造成冷气向中叶展汇聚;通过对比单排冷却的叠加结果与全覆盖实验结果的误差,研究了Sellers叠加模型在叶栅条件下的适用性。     

开槽前扩孔及复合角对气膜冷却的影响

本文对开槽前扩孔及在此基础上加30°、45°和60°不同角度复合角的气膜冷却结构进行了数值模拟,计算了指定冷却壁面的温度场分布以及冷却效率.结果表明:引入复合角后,能够改善冷却气膜在壁面的横向分布,复合角越大,气膜分布越均匀.在高吹风比下,复合角结构能够产生较大的气膜覆盖范围和较好的冷却效果.     

涡轮动叶吸力侧单排气膜孔冷却性能研究

本文通过数值模拟的方法,针对涡轮叶片吸力侧的单排气膜孔,研究了无量纲气膜孔出流位置、气膜孔复合角度和冷却空气质量流量占比对其气膜冷却效率与气动掺混损失的影响。结果表明,对于近前缘气膜孔,0.5%的冷却空气质量流量可以在保证较好的气动效率的同时在下游附近提供较高的绝热气膜冷却效率;对于中后部气膜孔,90°的气膜孔导致的掺混损失比相同冷气量的近前缘气膜孔高出一倍,此时复合角为60°的气膜孔有更好的气膜冷却效果。对比不同的孔排位置,位于流向位置0.3的气膜孔可以在下游较大区域取得良好的冷却效果,而且不引起过大的掺混损失。     

两排圆孔的气膜冷却特性

气膜冷却被广泛地应用在现代透平冷却设计中。对于很多热端部件,为了保证足够的冷却效果,其表面需要布置多排气膜孔来得到更高的冷却效率,Sellers叠加公式是目前多排孔设计当中最常用的叠加方法。本文采用PSP技术研究了单排圆孔与两排圆孔的在不同吹风比和密度比下气膜冷却特性,并同时进行了相应工况下的数值计算来获得更详细的流场信息,Sellers叠加公式预测结果也进行了比较以探索其适用范围。结果表明,对于圆孔的气膜冷却,在低吹风比时,第二排孔基本不受第一排孔影响;在高吹风比时,由于前排孔出气对主流的推举作用,后排孔更容易吹离,冷却效果变差。而Sellers叠加公式仅在低吹风比高密度比时预测结果较好,其余工况预测偏大。     

涡轮流场影响端壁气膜冷却的实验研究

采用压力敏感漆技术对高压涡轮动叶平面叶栅端壁气膜冷却特性进行了实验研究,对比分析了气膜冷却射流吹风比和叶栅进口主流雷诺数对端壁气膜有效度分布的影响.实验中主流雷诺数分别为164476、226154、308392和359790,各主流雷诺数下气膜射流吹风比变化范围从0.4到1.4.端壁前缘气膜孔吹气角为45°,其余端壁气...     

定出流面积条件下气膜冷却孔型的研究

本文采用数值模拟的方法,在保持冷却射流出口面积不变的条件下,分析比较了圆柱形孔、扇形孔、双射流孔和带双肩形孔这几种气膜孔的冷却效果。研究结果表明:对于圆柱形孔,气膜冷却效率在吹风比M=0.5左右效率较高;对于扇形孔,在对应圆柱形孔吹风比M=1.5时的效率要优于低吹风比情况;对于双射流孔和带双肩形孔,在对应圆柱形孔吹风比M=1.0时的冷却效果更好。原因在于高吹风比情况下,圆柱形孔结构中冷却射流与高温主流形成较强的肾形涡,会使冷却气体脱离壁面,并将高温主流卷入冷却气膜层,从而破坏冷却效果,而扇形孔、双射流孔以及带双肩形孔能有效地抑制肾形涡对冷却流的提升作用,从而保持冷却气膜的贴壁性,提高了气膜冷却效率。     

Non-minimally coupled scalar fields, Holst action and black hole mechanics

The paper deals with the extension of the Weak Isolated Horizon (WIH) formulation of black hole horizons to the non-minimally coupled scalar fields. In the early part of the paper, we introduce an appropriate Holst type action to incorporate scalar fields non-minimally coupled to gravity and construct the covariant phase space of the theory. Using this phase space, we proceed to prove the laws of black hole mechanics. Further, we show that with a gauge fixing, the symplectic structure on the horizon reduces to that of a U(1) Chern–Simons theory. The level of the Chern–Simons theory is shown to depend on the non-minimally coupled scalar field.     

光谱烧孔技术

论述了光谱烧孔技术的动力学理论模型 ;介绍了单光子烧孔和多光子烧孔所取得的实验结果 ;讨论了光谱烧孔的发展趋势 :提高烧孔度 ,实现室温烧孔和提高探测及读出时的信噪比。问题的关键在于光致填孔机制的研究。同时提出将它投入实际应用亟待解决的问题 ,即作为一种可能的高密度频域光信息存储手段所亟待解决的问题是开发适应于此技术的新材料 ,深入研究材料体系的烧扎特性     

不同选通条件下对光谱烧孔孔深的研究

本文从理论上分析了低激发密度下,选通光分别为脉冲光和连续光时,孔深随时间的变化,得到可以通过脉冲光烧孔、连续光选通的方法缩短烧孔时间.应用BaFCl_0.5Br_0.5:Sm²⁺(2%)进行了实验,分析了单脉冲烧孔的孔深.     

不同选通条件下对光谱烧孔孔深的研究

本文从理论上分析了低激发密度下，选通光分别为脉冲光和连续光时，孔深随时间的变化，得到可以通过脉冲光烧孔、连续光选通的方法缩短烧孔时间．应用ＢａＦＣｌ０．５Ｂｒ０．５：Ｓｍ２＋（２％）进行了实验，分析了单脉冲烧孔的孔深．     

Noncommutative Singular Black Holes

In this paper, applying the method of coordinate coherent states to describe a noncommutative model of Vaidya black holes leads to an exact （t - r） dependence of solution in terms of the noncommutative parameter σ. In this setup, there Js no black hole remnant at long times.     

Quantization of the space－time with topological defect

We present the classical solution of Lagrange equations for the black hole with a global monopole or with a cosmic string. Then we obtain the wavefunction of the space－time by solving the Wheeler－De Witt equation. De Broglie－Bohm interpretation applied to the wavefunction gives the quantum solution of the space－time. In the end, the quantum effect on Hawking radiation is studied.     

Comment on “Evolution Equations of Nonlinearly Permissible,Coherent Hole Structures Propagating Persistently in Collisionless Plasmas”

Recent critical remarks, published in this journal, about the present author's analysis of electron and ion holes and their stability are addressed and shown to be misunderstandings and misrepresentations.     

Three-dimensional massive Kiselev AdS black hole and its thermodynamics

We present an exact three-dimensional massive Kiselev AdS black hole solution. This Kiselev black hole is neither perfectly fluid, nor is it the quintessential solution, but the BTZ black hole modified by the anisotropic matter. This black hole possesses an essential singularity at its radial origin and a single horizon whose radius will increase monotonically when the parameter of the anisotropic matter field ω decreases. We calculate all thermodynamic quantities and find that the first law of thermodynamics of this massive Kiselev AdS black hole can be protected, while the consistent Smarr formula is only held in the extended thermodynamic phase space. After examining the sign of free energy, we conclude that there is no Hawking-Page transition since the massive Kiselev AdS black hole phase is always thermodynamically favored. Moreover, we study the phase transition between the Kiselev AdS black hole and BTZ black hole by considering the matchings for their temperature. We find that the Kiselev AdS black hole is still a thermodynamically more preferred phase, because it always has a smaller amount of free energy than the BTZ black hole, which seems to indicate that the anisotropic matter field may emerge naturally in BTZ black hole spacetime under some thermal fluctuations. We also show a first order phase transition between the Kiselev AdS black hole phase with -1w -1/2 and the black hole phase with -1/2w0. As the Kiselev AdS black hole has some notable features on the phase transition of black holes in three dimensions, it provides important clues to further investigate these both surprising and similar behaviors in four and higher dimensions.     

Noncommutative Singular Black Holes

In this paper, applying the method of coordinate coherent states to describe a noncommutative model of Vaidya black holes leads to an exact (t - r) dependence of solution in terms of the noncommutative parameter σ. In this setup, there is no black hole remnant at long times.     

A comparison of the intensity contours of fringes due to multiple reflection and spatial hole burning in semiclassical theory of laser

A comparison between spatial burning in the semiclassical theory of laser and the intensity contours of the fringes due to multiple reflections in a Fabry-Perot cavity is presented. The concept of spatial hole burning is also used in a quantum well system.