共查询到20条相似文献,搜索用时 62 毫秒
1.
带气膜孔内部冷却通道的流动传热特性 总被引:2,自引:0,他引:2
燃气轮机高温透平内部冷却通道中弯头、肋片和气膜孔之间存在着复杂的交互作用。本文采用瞬态液晶技术对光滑通道、无抽吸的带肋通道和有气膜孔抽吸的带肋通道的表面传热分布和沿程压力损失进行了详细测量,同时采用RANS数值模拟方法研究其流场特性。结果表明180°弯头产生的大分离是压力损失的主要因素,45°斜肋片产生的螺旋形流动在弯头与大分离交互作用明显,气膜孔抽吸破坏孔附近边界层使得肋间传热而相对集中于孔附近。在13%抽吸量条件下,气膜孔抽吸降低U型通道中压力损失约20%,同时保持传热强化程度与无抽吸工况相同。 相似文献
2.
3.
4.
涡轮叶片尾缘劈缝气膜冷却特性实验研究 总被引:2,自引:0,他引:2
《工程热物理学报》2016,(9)
本文将层板冷却应用于涡轮叶片尾缘冷却中。为了研究肋形状对其劈缝气膜冷却特性的影响,在四种吹风比下,实验测量了直肋和倒斜角肋两种肋结构下的气膜冷却效率和换热系数,结果发现:1)倒斜角肋结构在劈缝下游的气膜冷却效率分布比直肋更均匀,倒斜角肋结构的平均气膜冷效高于直肋结构;2)两种结构的换热系数在劈缝出口处受吹风比影响较大,相同吹风比下,倒斜角肋结构的换热系数略高于直肋结构。 相似文献
5.
6.
为了研究网格缝结构的气膜冷却特性,开展了平板模型试验研究,使用瞬态液晶测温技术测量了缝下游表面的气膜冷却效率和换热系数分布,在相同压比下与圆柱孔进行了气膜冷效对比,同时研究了缝内扰流柱布局对网格缝结构气膜冷却特性的影响。网格缝结构的吹风比范围为0.26M1.25。实验结果表明:网格缝结构的气膜冷效展向分布均匀性比圆柱孔有显著提高,且吹风比增加后不会出现射流脱离壁面的现象;在扰流柱和缝后斜面的作用下,缝下游会形成对卷旋涡,使得最下游一排扰流柱下游的气膜冷效相对较高;扰流柱顺排时,缝下游气膜冷效分布更均匀,大吹风比时,顺排结构的展向平均气膜冷效比叉排结构高出23%~84%,换热系数比高出11%;吹风比M1时,顺排结构的流量系数更高,M1时,叉排结构的流量系数更高。 相似文献
7.
8.
9.
10.
为了进一步提高涡轮入口温度,提出一种新型气膜冷却方法~含化学热沉的气膜冷却方法。对于新方法来讲,化学热沉的存在会影响气膜孔下游的流场,从而影响主流与固体壁面的换热。建立简化理想化学热沉模型,采用标准k-ε湍流模型对该方法进行数值模拟,结果表明,化学热沉的存在降低了气膜孔出口下游不远处壁面附近的温度,同时增大了壁面处混合气膜与壁面之间的对流换热系数. 相似文献
11.
Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide 总被引:1,自引:0,他引:1
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs. 相似文献
12.
A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users. 相似文献
13.
S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
14.
A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output. 相似文献
15.
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper. 相似文献
16.
17.
We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed. 相似文献
18.
Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell. 相似文献
19.
A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques. 相似文献
20.
Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing. 相似文献