共查询到20条相似文献,搜索用时 234 毫秒
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交错肋是航空发动机涡轮叶片的一种高性能内冷结构,为研究涡轮叶片内部交错肋冷却结构的流动和传热特性,针对30?、35?和45?三种肋倾角的交错肋结构进行了雷诺数在17000~70000之间的稳态传热实验和数值模拟研究。数值计算的有效性通过与实验结果进行对比得到充分验证。实验结果显示,在子通道个数和雷诺数均相同的情况下,平均Nu数和摩擦因子均随肋倾角的增大而增加;对比30?倾角的交错肋结构,45?倾角交错肋结构的平均Nu数增加了40.7%,摩擦因子增加了204.9%,综合传热性能提升了13.4%。数值计算结果显示,肋倾角的增大不仅增强了转向区域的冲击作用,而且加强了对侧子通道间的流动掺混,从而达到强化传热的效果。 相似文献
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叶片安装角偏差对涡轮通道内热斑迁移的影响 总被引:9,自引:0,他引:9
叶片的加工和安装偏差不仅直接影响到涡轮的性能,而且可能对叶片通道内热斑的迁移产生影响.为了研究这种偏差对热斑在涡轮中迁移及叶片热负荷等的影响,本文以某高压涡轮级为例,利用三维非定常数值模拟手段进行了研究.结果表明:动叶安装角的偏差对动叶中热斑的迁移如周向迁移有较明显的影响;而热斑迁移的变化将直接影响涡轮动叶压力面和吸力面的热负荷分布,最终影响涡轮叶片的寿命;并且热斑迁移的变化还导致下游支板通道内温度分布产生较为明显的变化,这有可能给发动机排气温度的测量带来偏差.热斑迁移的变化在涡轮的设计和故障分析中应予重视. 相似文献
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When operating under lean fuel–air conditions, flame flashback is an operational safety issue in stationary gas turbines. In particular, with the increased use of hydrogen, the propagation of the flame through the boundary layers into the mixing section becomes feasible. Typically, these mixing regions are not designed to hold a high-temperature flame and can lead to catastrophic failure of the gas turbine. Flame flashback along the boundary layers is a competition between chemical reactions in a turbulent flow, where fuel and air are incompletely mixed, and heat loss to the wall that promotes flame quenching. The focus of this work is to develop a comprehensive simulation approach to model boundary layer flashback, accounting for fuel–air stratification and wall heat loss. A large eddy simulation (LES) based framework is used, along with a tabulation-based combustion model. Different approaches to tabulation and the effect of wall heat loss are studied. An experimental flashback configuration is used to understand the predictive accuracy of the models. It is shown that diffusion-flame-based tabulation methods are better suited due to the flashback occurring in relatively low-strain and lean fuel–air mixtures. Further, the flashback is promoted by the formation of features such as flame tongues, which induce negative velocity separated boundary layer flow that promotes upstream flame motion. The wall heat loss alters the strength of these separated flows, which in turn affects the flashback propensity. Comparisons with experimental data for both non-reacting cases that quantify fuel–air mixing and reacting flashback cases are used to demonstrate predictive accuracy. 相似文献
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波浪与风载的共同作用下,海上风电机组平台存在多自由度运动,同时伴随着海上复杂的风况,其气动特性变化较为复杂。以NREL5MW风电机组为研究对象,在风剪切来流下,依据波浪和风载的作用规律,研究平台纵摇和纵荡运动对机组气动特性和绕流场细节的影响。结果表明:平台运动会造成风电机组气动性能的周期性波动,而风剪切作用使得风电机组平均发电量降低并加剧功率和推力的波动。风剪切会增大纵摇运动过程中展向截面的法向载荷幅值且波动加剧,但会降低与功率输出有关的切向受力;风剪切作用推迟了纵荡运动过程中展向截面法向和切向载荷峰值出现时刻,加剧载荷的波动。外叶展截面的法向和切向力系数曲线出现平台,加剧了叶片疲劳载荷,减小了功率输出。 相似文献
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与传统光纤不同,光子晶体光纤可以具有多个零色散波长,在四波混频光谱中,具有更丰富的相位匹配特性。目前很多文献报道了光子晶体光纤非线性光学特性的实验结果,但对其产生机理及光谱的变化规律缺乏详细的理论分析。为此对光纤中四波混频原理进行了分析,给出了高增益的相位匹配条件。利用多极法计算了光子晶体光纤的非线性系数及色散特性。对具有多个零色散波长光子晶体光纤的相位失配特性进行了分析,得到了相位匹配波长随泵浦波长及泵浦功率的变化规律。给出了相位匹配曲线,分析了不同色散曲线的相位匹配波长特点,两个零色散波长光子晶体光纤,在四波混频光谱中将激发出四个新的波长。实验得到了两个零色散波长光子晶体光纤的四波混频光谱,与理论分析一致,验证了相位匹配理论的可靠性。多个零色散波长光纤,能产生丰富的相位匹配曲线,会出现更多的四波混频波长,可以有效的控制光孤子及超短脉冲的四波混频及共振散射产生的光谱特性。为光子晶体光纤中基于四波混频的波长变换及超连续谱的研究提供了理论指导。 相似文献
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Rami F Leifels Y de Schauenburg B Gobbi A Hong B Alard JP Andronic A Averbeck R Barret V Basrak Z Bastid N Belyaev I Bendarag A Berek G Caplar R Cindro N Crochet P Devismes A Dupieux P Dzelalija M Eskef M Finck C Fodor Z Folger H Fraysse L Genoux-Lubain A 《Physical review letters》2000,84(6):1120-1123
Four different combinations of 9644Ru and 9640Zr nuclei, both as projectile and target, were investigated at the same bombarding energy of 400A MeV using a 4pi detector. The degree of isospin mixing between projectile and target nucleons is mapped across a large portion of the phase space using two different isospin-tracer observables, the number of measured protons and the tritium to 3He yield ratio. The experimental results show that the global equilibrium is not reached even in the most central collisions. Quantitative measures of stopping and mixing are extracted from the data. They are found to exhibit a quite strong sensitivity to the in-medium ( n,n) cross section used in microscopic transport calculations. 相似文献
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本文提出在Kα波段圆柱过模结构绕射辐射器件(RDG)中引入一种带有锥度结构的同轴内开槽布拉格反射器.采用复功率守恒技术(CCPT)对该反射器的频率响应特性进行分析.研究了相位匹配段长度,波纹槽深及锥度对反射器频率响应特性的影响,分析了波纹初始相位对反射器选模特性的影响,发现该反射器具有良好的模式选择特性.本文的研究工作为同轴Bragg反射器结构的研究提供了重要的理论分析手段.
关键词:
同轴Bragg反射器
频率响应特性
复功率守恒
绕射辐射振荡器 相似文献