共查询到19条相似文献,搜索用时 296 毫秒
1.
2.
3.
致密多孔层板冷却结构研究 总被引:2,自引:0,他引:2
应用FLUENT软件对内部绕流形式不同的7种层板结构进行流动与换热的耦合计算,分析扰流柱、冲击孔、气膜孔之间的排布方式以及堵塞比等参数对层板冷却效率与相对压力损失的影响规律。研究表明,层板结构以冲击孔和气膜孔呈现长菱形分布、扰流柱呈梭子形排布的方式较好,压力损失小,综合冷却效率可以提高10%左右;在进气流量相同的情况下,不同的层板结构压力损失相差不大,压力损失主要发生在从环腔经气膜壁进入火焰筒流出的过程中;增加扰流柱的数量或者是增大扰流柱的直径都会带来堵塞比的增大,层板的相对压力损失会随之增加,综合冷却效率增大,一定程度上强化了换热。 相似文献
4.
叉车的冷却系统担负着发动机和液力传动系统的冷却作用,冷却效果的好坏直接关系着叉车能否正常工作和发动机的使用寿命,因此正确分析叉车冷却系统各部件间的作用关系,对经常出现高温现象的叉车冷却系统进行合理的设计改进意义重大。我公司生产的CPCD50/60/70AA系列叉车普遍存在油温偏高问题,在南方地区使用时尤为严重。影响冷却系统冷却效果的因素有:(1)水箱的冷却面积;(2)风扇的直径、叶片数和转速;(3)风扇距离水箱的距离;(4)风扇罩的形状。总之让尽量多的风量通过尽可能大的水箱冷却面积可以得到好的冷却效果。针对以上影响因素我们认… 相似文献
5.
层板结构冷却机理的数值模拟研究 总被引:1,自引:0,他引:1
应用商业软件对一种典型的层板结构选取多个单元进行了流动和换热的耦合计算,考虑了燃气侧及冷气侧流动的影响,燃气及冷气的流动方式模拟层板叶片中真实的流动方式。网格划分采用非结构性网格,湍流模型采用k-ω双方程模式,速度与压力采用SIMPLE算法耦合求解。获得了层板内部的流动和换热情况,流体域、固体域的温度信息。发现冲击孔及气膜孔内部的流动不具有对称性,各换热面的换热系数分布也不均匀,燃气侧局部区域出现负热流现象。分析了层板燃气侧、内部及冷气侧的流动和换热特性及其对层板冷却有效性的影响,得到了层板冷却有效性随吹风比变化的曲线。 相似文献
6.
为研究旋转造成的非稳定性对高压涡轮动叶气膜冷却的影响,建立了3维涡轮叶栅通道模型,应用周期性边界条件数值模拟了不同转速下涡轮动叶表面气膜冷却效率和换热系数的分布,冷气进口与涡轮前总压比为1.07,温度比为0.5。转速增加,叶片前缘滞止线从压力面移向吸力面,气膜出流从吸力面移向压力面;压力面气膜冷却效率上升,换热系数下降;吸力面冷却效率先上升后降低;换热系数下降。与静止相比,旋转不稳定性增大了叶片表面气膜覆盖面积。 相似文献
8.
针对三气(燃气、冷气、大气)、两壁(隔热屏、燃烧室外壁)、一膜(隔热屏冷气膜)的燃烧室物理模型,建立了它们之间气动与传热互相耦合的隔热屏二维壁温计算模型.模型中考虑了燃气、空气的动力粘性系数和导热系数随温度的变化,以及燃气温度轴向的非线形变化.利用该模型针对某燃烧室设计进行壁温预测,并进行了三种增大冷气量方法的冷却效果比较,研究了同比例减小孔径和孔间距的冷却特性.计算结果表明:每增加1%冷气量,平均隔热屏温度降低约30K,同比例减小孔径和孔间距可以不增大冷气用量而降低隔热屏壁温,孔径减半,平均温度降低40K左右,孔径越小降低幅度越大. 相似文献
9.
10.
模拟研究不同结构参数和运行参数对叉流式露点蒸发冷却器(DPEC)冷却性能的影响。优化后的结构参数为:通道宽度宜取4 mm,干、湿通道长度均宜取1.2 m,开孔率宜取0.2,换热面积比宜取0.2;与优化后的结构参数相匹配的运行参数为:空气流量比宜取1,相应的一、二次空气流量均宜低于916 m~3/h。模拟研究我国8种典型气候条件对叉流式DPEC冷却性能的影响,结果显示冷却器在我国中西部气候条件下能够提供较低温度的送风(18.9~23.9℃)。 相似文献
11.
12.
叶片前缘气膜冷却数值模拟 总被引:4,自引:0,他引:4
为了研究叶片前缘区域的换热特性,采用非结构化网格和realizable紊流模型,求解三维N-S方程,对前缘带有一排冷气孔的涡轮叶片进行了换热特性的数值模拟.分析了不同动量比,湍流度,孔间距及径向角下冷气射流的运动规律,换热分布以及冷效分布特点.结果表明,当动量比Ⅰ大于1时,在相同孔型下,动量比越高,冷效越大.在相同动量比下,孔间距越小,冷效越大.但动量比,孔间距及径向角对换热系数影响不大.当湍流度增加时,换热系数增加而冷效降低.沿展向,气膜孔中心区域冷效较高,两孔之间区域较低;而换热系数则相反,气膜孔中心区域换热系数较小,两孔之间区域较大. 相似文献
13.
Somin Shin Ki Seon Lee Seoung Duck Park Jae Su Kwak 《Journal of Mechanical Science and Technology》2009,23(3):624-630
Heat transfer coefficients were measured in a channel with one side dimpled surface. The sphere type dimples were fabricated,
and the diameter (D) and the depth of dimple was 16 mm and 4 mm, respectively. Two channel heights of about 0.6D and 1.2D,
two dimple configurations were tested. The Reynolds number based on the channel hydraulic diameter was varied from 30000 to
50000. The improved hue detection based transient liquid crystal technique was used in the heat transfer measurement. Heat
transfer measurement results showed that high heat transfer was induced downstream of the dimples due to flow reattachment.
Due to the flow recirculation on the upstream side in the dimple, the heat transfer coefficient was very low. As the Reynolds
increased, the overall heat transfer coefficients also increased. With the same dimple arrangement, the heat transfer coefficients
and the thermal performance factors were higher for the lower channel height. As the distance between the dimples became smaller,
the overall heat transfer coefficient and the thermal performance factors increased.
This paper was recommended for publication in revised form by Associate Editor Yong Tae Kang
Jae Su Kwak received his B.S. and M.S. degrees in Mechanical Engineering from Korea University in 1996 and 1998, respectively. He then
received his Ph.D. from Texas A&M University in 2002. Dr. Kwak is currently an Assistant Professor at the School of Aerospace
and Mechanical Engineering at Korea Aerospace University in Goyang-City, Korea. His main research interests include gas turbine
heat transfer, compact heat exchanger, and enhancement of heat transfer. 相似文献
14.
15.
涡轮叶片非对称扇形气膜孔冷却特性数值研究 总被引:2,自引:0,他引:2
针对涡轮导向叶片吸力面和压力面上特定位置上的单排气膜孔,在吹风比为0.44~2.67范围内,数值研究非对称扇形气膜孔的冷却特性。基准对称扇形孔侧向扩展角为20°,后向扩展角为10°。研究结果表明,在扇形总扩展角相等的条件下,非对称型扇形气膜孔的气膜出流穿透能力与对称型扇形气膜孔基本相当,但气膜出流侧向覆盖范围较对称型扇形气膜孔有一定程度的改善,在高吹风比下扇形气膜孔侧向扩展角的影响较为显著。相对而言,非对称扇形气膜孔改善气膜冷却的效果在涡轮叶片压力面侧能得到更好的体现。 相似文献
16.
Heat/mass transfer characteristics on the near-tip blade surface under combustor-level high inlet turbulence have been investigated
within a high-turning turbine rotor passage by using the naphthalene sublimation technique. The inlet turbulence intensity
and length scale are 14.7% and 80 mm, respectively. The tip gap-to-chord ratio is changed to beh/c = 0.74, 1.47, and 2.94 percents. Increasingh/c results not only in higher heat/mass transfer in the pressure-side tip region but also in more convective transport on the
pressure surface even far away from the tip edge. Severe heat/mass transfer is always observed in the suction-side tip-leakage
flow region which can be divided into two distinct high transport regions. There is a local maximum of heat/mass transfer
along the trailing-edge centerline. This arises from the interaction of a tip-leakage vortex with a trailing-edge vortex shedding.
Comparisons of the present data forh/c = 2.94 percents with the previous low turbulence one show that there is a large discrepancy of heat/mass transfer in the
pressure-side near-tip area, which diminishes with departing from the tip edge. The suction-side heat/mass transfer in the
tip-leakage flow region is less influenced by the high inlet turbulence than that at the mid-span. The leading-edge heat/mass
transfer under the high inlet turbulence is always higher than that in the low turbulence case, while there is no big difference
in the trailing-edge heat/mass transfer between the two cases. 相似文献
17.
18.
19.
Zhen-Zhe Li Kwang-Su Heo Dong-Ji Xuan Seoung-Yun Seol 《Journal of Mechanical Science and Technology》2009,23(3):607-613
Thermoforming is one of the most versatile and economical processes available for polymer products, but cycle time and production
cost must be continuously reduced in order to improve the competitive power of products. In this study, water spray cooling
was simulated to apply to a cooling system instead of compressed air cooling in order to shorten the cycle time and reduce
the cost of compressed air used in the cooling process. At first, cooling time using compressed air was predicted in order
to check the state of mass production. In the following step, the ratio of removed energy by air cooling or water spray cooling
among the total removed energy was found by using 1-D analysis code of the cooling system under the condition of checking
the possibility of conversion from 2-D to 1-D problem. The analysis results using water spray cooling show that cycle time
can be reduced because of high cooling efficiency of water spray, and cost of production caused by using compressed air can
be reduced by decreasing the amount of the used compressed air. The 1-D analysis code can be widely used in the design of
a thermoforming cooling system, and parameters of the thermoforming process can be modified based on the recommended data
suitable for a cooling system of thermoforming.
This paper was recommended for publication in revised form by Associate Editor Dongsik Kim
Zhen-Zhe Li received his B.S. degree in Mechanical Engineering from Yanbian University, China, in 2002. He then received his M.S. degree
in Aerospace Engineering from Konkuk University, South Korea, in 2005. He then received his Ph.D. degree in Mechanical Engineering
from Chonnam National University, South Korea, in 2009. Dr. Li is currently a Researcher of the Department of Mechanical Engineering,
Chonnam National University, South Korea. Dr. Li’s research interests include applied heat transfer, fluid mechanics and optimal
design of thermal and fluid systems.
Kwang-Su Heo received his B.S. degree in Mechanical Engineering from Chonnam National University, South Korea, in 1998. He then received
his M.S. and Ph.D. degrees in Mechanical Engineering from Chonnam National University, South Korea, in 2003 and 2008, respectively.
Dr. Heo is currently a Post-doctorial Researcher of the Department of Mechanical Engineering, KAIST(Korean Advanced Institute
of Science and Technology), South Korea. Dr. Heo’s research interests include applied heat transfer, fluid mechanics and thermal
analysis of superconductor.
Dong-Ji Xuan received his B.S. degree in Mechanical Engineering from Harbin Engineering University, China, in 2000. He then received his
M.S. degree in Mechanical Engineering from Chonnam National University, South Korea, in 2006. He is currently a Ph.D. candidate
of the Department of Mechanical Engineering, Chonnam National University, South Korea. His research interests include control
& optimization of PEM fuel cell system, dynamics & control, mechatronics.
Seoung-Yun Seol received his B.S. degree in Mechanical Design from Seoul National University, South Korea, in 1983. He then received his
M.S. degree in Mechanical Engineering from KAIST(Korean Advanced Institute of Science and Technology), South Korea, in 1985.
He then received his Ph.D. degree in Mechanical Engineering from Texas Tech University, USA, in 1993. Dr. Seol is currently
a Professor of the School of Mechanical and Systems Engineering, Chonnam National University, South Korea. Dr. Seol’s research
interests include applied heat transfer, fluid mechanics and thermal analysis of superconductor. 相似文献