共查询到20条相似文献,搜索用时 93 毫秒
1.
采用Realizable k-ε湍流模型,并结合Simple算法和有限体积法对三维定常不可压缩N-S方程进行离散,对某重型燃气轮机透平第一级动叶在不同吹风比和主流湍流度条件下的气膜冷却效率进行了数值模拟。结果表明:气膜冷却能够有效地降低叶片表面的温度,但叶片前缘吹风比的改变对冷却效果的影响不是很大,在前缘滞止线两侧仍然存在较大的高温区;在压力面侧和吸力面侧,随着吹风比的增大,沿叶片展向平均冷却效率分布都得到了提高;低吹风比时,吸力面靠前缘区域孔排中的冷却孔保持单孔冷却特点,孔间区域冷却效果较差;主流湍流度对气膜冷却效果产生了明显的影响,但影响趋势因不同吹风比而各不相同,其对冷却射流的影响主要集中在气膜孔下游扩散上。 相似文献
2.
为了增强燃气轮机动叶气膜冷却效果,提出一种缩放型气膜孔结构。采用数值模拟的研究方法,模拟了当吹风比M=1.2、主流湍流度Tu=5%时,不同孔间距下分别带有圆柱型气膜孔和缩放型气膜孔叶片的气膜冷却效果。研究结果表明:无论是在叶片压力面还是吸力面,带有缩放型气膜孔叶片的气膜冷却效果总体要优于圆柱型气膜孔叶片;在圆柱型气膜孔和缩放型气膜孔叶片表面,覆盖的气膜整体朝向叶片偏转角流动,由于叶片受到前缘冷却的影响,叶片后缘位置的气膜冷却效率更高,整体呈现出偏转叠加效应,带缩放型气膜孔的叶片在后缘位置冷却优势更加明显;随着孔间距的减小,两种孔型叶片的平均气膜冷却效率都呈现递增趋势,冷却性能得到提高。 相似文献
3.
4.
为了提高燃气轮机动叶的气膜冷却效果,采用Realizable k-ε湍流模型,并结合Simple算法和有限体积法对三维定常不可压缩N-S方程进行离散,在不同吹风比和主流湍流度条件下,分析了某重型燃气轮机孔间距对动叶气膜冷却效率的影响.结果表明:在一定条件下,随着孔间距的增大,冷却气体覆盖程度变差,冷却效率下降;受到叶片前缘孔排冷气的动量叠加,叶片后缘孔排气膜冷却效率明显高于前缘孔排气膜冷却效率;相同孔间距下,随着吹风比的增大,叶片综合冷却效率呈现升高的趋势;在其他条件一定的情况下,吹风比M=1.4时,主流湍流度越大,气膜冷却效率越低,但影响较小. 相似文献
5.
6.
采用低稠度涡轮导向叶片设计方案,可减少导向叶片的用量,减轻涡轮重量,降低发动机冷气用量及耗油率,但同时也带来导向叶片端壁冷却负荷增大等问题。依据低稠度涡轮导向叶片端壁的结构与流动换热特点,制定了槽缝和气膜孔共同冷却的方案。通过数值模拟和分析,重点研究了低稠度涡轮导向叶片端壁前缘气膜孔在不同方向角、孔数、孔径以及叶栅通道中气膜孔布置等条件下的流动及冷却特性。研究结果表明:对低稠度涡轮导向叶片端壁前缘气膜孔进行优化设计,可以有效克服导向叶片端壁前缘高强度马蹄涡对于气膜冷却效果的不良影响;在叶栅通道内合理设置气膜孔,可以改善通道内复杂涡旋对端壁气膜的卷吸作用,提高气膜冷却效果;当槽缝和气膜孔中的冷气流量比分别为3%和2%、气膜孔方向角为45°、气膜孔直径为1.25 mm、叶片前缘和叶栅通道气膜孔数分别为8和1时,叶片端壁表面被冷气膜全部覆盖,此时端壁面平均气膜冷却效率相对最高,达到53.7%。 相似文献
7.
8.
气膜孔的位置对涡结构和气膜冷却效率的影响 总被引:1,自引:0,他引:1
在燃气轮机中,气膜冷却技术能有效地从高温燃气中保护涡轮叶片,如何提高气膜冷却效率是气膜冷却研究的热点问题。使用大涡模拟(LES)模型分析了平板气膜孔在吹风比为0.5工况时气膜孔下游的速度分布,并与实验进行对比验证。在相同吹风比下,通过模拟叶片上不同气膜孔的位置相应的入口速度分布,研究其对气膜冷却效率的影响,以及对气膜冷却过程中占主导地位涡结构的形成和发展的重要影响。随着气膜孔的位置靠后,湍流边界层随之增厚,滚子涡和肾型涡对生成加快,涡强增大,涡核脱离壁面,从而影响气膜冷却效率。湍流边界层的变化对流向和展向的气膜冷却效率和冷却覆盖范围有明显的影响。 相似文献
9.
10.
在燃气轮机透平叶片冷却设计中,气膜冷却是一种高效的冷却方式,能保护叶片表面不受高温燃气侵蚀。成型孔是目前广泛应用的气膜孔型。为研究孔型结构对冷却效率的影响作用,展开了数值计算。首先通过数值模拟方法研究了平板上4种不同结构的成型孔在吹风比为1.5~2.5工况下的流动换热规律,发现一种收敛缝型孔具有冷气覆盖面广、冷却效率高的特点。将带展向11°扩张角、流向10°扩张角的成型孔与收敛缝型孔布置在叶片上,进一步展开数值计算,发现在前者的气膜孔排布置下,冷却气分布更加均匀,冷气消耗量少,仅为收敛缝型孔的37%,更符合冷却叶片设计原则。 相似文献
11.
论述了盐化工热电厂二期技术改造的方案与具体措施,说明在背压机组后增设后置机来增加其进汽量是解决背压机组因下游用汽量不足而无法稳定运行问题的有效手段;选取参数适当的旧凝汽式机组改造为背压机组的后置机在技术上是成熟的,在实际应用上也是可行的。 相似文献
12.
13.
14.
本文将煤气化技术用于注蒸汽燃气轮机循环,对以煤气化产物为燃料的注蒸汽循环进行了热力学分析,并讨论了各参数对循环性能的影响。 相似文献
15.
Ozer Igra 《Energy Conversion and Management》1981,21(1):13-48
In order to exploit wind power as economically as possible, it was suggested that the wind turbine should be enclosed inside a specially designed shroud. Various geometries are discussed; it is shown that with a fairly compact shroud a significant power augmentation can be achieved. For improving the shroud performance, the use of a ring-shaped flap or boundary layer control technique is introduced. It is shown that up to 80% improvement in the shroud power augmentation can be obtained by the use of an appropriate ring-shaped flap while proper bleeding of the shroud's external flow into its inner rear part will increase its power augmentation by about 25%. The present review also discussed the design and performance of an axial flow turbine which is the most suitable for the proposed shrouds. It is shown that such a turbine produces a fairly stable output for varying wind speeds while exhibiting a fairly high efficiency. Based on the reported research with shrouds, a pilot plant producing 1 hp at 5 m/s with a 3 m dia. turbine was built. Its design and preliminary field test results are also included in the review. 相似文献
16.
Yomei Yoshioka 《Energy Materials: Materials Science and Engineering for Energy Systems》2018,13(2):386-396
More than 80% of prime energy is now supplied by thermal power plants in Japan since the Great East Earthquake of 2011 and more than two thirds of them were operated for over 30 years. Evaluation of the residual life of those aged plants are, therefore, required to maintain reliability and also to avoid premature retirement. Several kinds of life assessment technologies for the high temperature components of aged steam and gas turbines have already been developed and applied to actual components. Further developments for the advanced ones are now still being conducted. The current status of Japanese thermal power plants is briefly overviewed and the life assessment technologies developed for evaluating the material degradation and component damage conditions and life extension capabilities of steam and gas turbines are explained with some examples of the applications. The differences between the development concepts and the methods developed for both turbines are also explained along with those of the design specifications. 相似文献
17.
18.
In this study, the aerodynamic noise characteristics of Savonius wind turbines were investigated using hybrid computational aero-acoustics techniques, and low-noise designs were proposed based on the understanding of the noise generation mechanism. First, the flow field around the turbine was analyzed in detail by solving three-dimensional unsteady incompressible Reynolds-averaged Navier–Stokes equations using computational fluid dynamics techniques. Then, the aerodynamic noise radiating from the wind turbine was predicted using the Ffowcs Williams and Hawkings equation with the obtained flow field information. Two distinct harmonic noise components—the blade passing frequency (BPF) and harmonics with a fundamental frequency that is much higher than the BPF—were identified in the predicted noise spectrum. The origin of the higher harmonic components was found to be related to vortex shedding from the rotating turbine. Based on this finding, the proposed low-noise design for Savonius wind turbines uses S-shaped blades. S-shaped blades were found to reduce the noise levels of Savonius wind turbines by up to 2.7 dB. 相似文献
19.
张晓晗 《电网与水力发电进展》2009,25(5):65-67
烟岗水电站属于高水头电站,在此水头段适合的水轮机机型有混流式和水斗式两种。通过对两种机型特点和两种转轮在国内外设计及生产制造难易程度的比较,以及参考国外厂家的选型意见,针对本电站地形条件、压力管道长等具体情况,选定烟岗水电站水轮机机型。 相似文献
20.
针对R20燃气轮机第三级涡轮工作叶片断裂事故,对叶片断裂部位开展宏观、微观形貌分析和力学 性能检测,得出叶片断裂的原因。结果显示:叶片的失效原因为疲劳,疲劳源在叶盆侧距离进气边3~4㎜
的表面研磨区域交界处,对比2和3号叶片的相同位置,1号叶片第一榫齿面研磨情况较为严重,研磨区域内 含有较高的铁和氧元素,与榫齿面和涡轮盘榫槽面发生微动磨损有关,导致疲劳裂纹过早地萌生;从宏观上 观察断口的疲劳扩展区比例、疲劳条纹宽度和疲劳条纹出现位置,判断为高周疲劳且疲劳裂纹扩展应力较高。 相似文献