掺气减蚀概念及优化 - 图文

本科生毕业论文

题 目 巴拉水电站溢洪道掺气减蚀措施 学 院 水利水电学院 专 业 热能与动力工程 学生姓名 刘信祥 学 号 0743081007 年 级 2007级 指导教师 邓 军

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二Ο一一 年 五 月 十六 日

四川大学本科毕业论文 巴拉溢洪道掺气减蚀措施

巴拉溢洪道掺气减蚀措施

专业：热能与动力工程

姓名：刘信祥 指导老师：邓军

摘要:溢洪道一般过流较大、流速较高，都会因为其流速较高容易残生空蚀破坏。在溢洪道上设置掺气设施，促使水流掺气，防止或者减少过水建筑物产生严重的空蚀，这种在水建筑物上设置掺气设施的方法，是水工中广泛采用的减蚀技术。然而，由于掺气减蚀机理复杂，目前对于通气量等问题的理论研究不够，关于掺气槽体型的研究成果较少，尚未有一套成熟有效的理论方法。本文通过模型试验，对溢洪道掺气槽进行实际分析。得到以下结论：

1.工程中常用的掺气减蚀措施：优化溢洪道体型，尽量使得过流表面的体型流线化,避免水流与固体边界发生分离现象；采用抗空蚀强度较高的材料作为过流表面材料;严格控制过流表面的不平整度。采取掺气减蚀措施，设置掺气坎。这也是工程中最常采取的有效措施。

2. 确定掺气坎的设置条件：工程实践得出在水流流速大于30m/s，空蚀指数?<0.3时建议设置掺气坎，当水流速度大于36m/s,空蚀指数?<0.2时必须设置掺气坎来减免空蚀破坏。

3. 影响掺气效果的因素：掺气坎的挑高和坎高，掺气坎的位置，通气竖井的通气情况和挑水水舌与边界的相交情况。

4.掺气坎空腔回水问题的研究及解决方案：分析了产生回水的理论原因，主要是受挑流落水点交角的影响，提出设置水平坡段将坡度集中起来，从而达到减小挑流落水点交角的目的。

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四川大学本科毕业论文 巴拉溢洪道掺气减蚀措施

关键词：溢洪道 掺气减蚀 掺气坎

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四川大学本科毕业论文 巴拉溢洪道掺气减蚀措施

Abstract：The spillway had a hug flux and a heavy speed in generally. In order to protect the water-carrying structures, people took some measures, one of these is that take the flow to be aerated flow. aeration cavitation-alleviation for spillway dam is the most commonly way to protect the water-carrying structures. In this paper, finding the most suitable Flow Aeration Type for Bala hydroelectric power station is what pursue for Sluice Buildings, no matter what kinds of flows, cavitation damage will play a important role with the heavy speed. However, the mechanism of aeration cavitation-alleviation is complicate and nowadays there is few studies in these sphere. Say nothing of types of arators. In this paper, we had a conclusion by analyzing the model test concerned respectively:

1. Engineering Aeration commonly used measures: optimize the spillway size, try to make the flow surface of the body streamlined to avoid the occurrence of flow separation with the solid boundary; cavitation-resistant high strength material as the material flow surface ; strict control over flow of surface roughness. measures taken Aeration, aerator set. This is also the project most effective measures taken.

2. determine the conditions of Aerator: engineering practice gave the suppose that if flow velocity is more than 30m/s, and the cavitation index the cavitation index

?<0.3, the aerator should be set, when the flow speed is greater than 36m/s,

?<0.2 ,aerator must be set to avoid cavitation damage.

3. the factors influencing cavitiation damage: the high ceiling and aerator high ridge, the location of aerator, ventilation shaft ventilation conditions and fetching water and the water situation in the tongue and the intersection of the boundary.

4. Aerator backwater problems and solutions: theoretical analysis of the reasons for producing backwater, mainly by the challenge of living water point angle is proposed to set the level of the gradient slope sections together, so as to achieve reduced point angle pick purpose of living water.

Keyword: spillway, aeration cavitation-alleviation, aerator

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四川大学本科毕业论文 巴拉溢洪道掺气减蚀措施

目录

第一章 绪论 ...................................................... 7

1.1空化空蚀[5] ................................................................................................................................................... 7 1.1.1空化空蚀相关概念 ........................................................................................................ 7 1.1.2空蚀机理 [6] ................................................................................................................... 7 1.1.3空化的分类 .................................................................................................................... 9 1.1.4空化的影响及溢洪道空蚀的特点 ................................................................................ 9 1.1.5减免空蚀的措施 .......................................................................................................... 10 1.2掺气水流 ..................................................................................................................................................... 10 1.2.1掺气现象及其影响[8] ................................................................................................... 11 1.2.2明渠中掺气水流的结构 .............................................................................................. 11 1.3掺气减蚀研究[8] ........................................................................................................................................ 13 1.4掺气减蚀原理和效果 ............................................................................................................................. 14 1.4.1掺气减蚀的原理[9] ........................................................................................................................... 14 1.4.3工程实践 ............................................................................................................................................. 15 1.5 掺气减蚀设施的类型 ............................................................................................................................ 15 1.5.1过流面和侧面掺气的型式 .......................................................................................... 15 1.5.2工程常用掺气减蚀类型 .............................................................................................. 15

第二章 巴拉工程溢洪道及实验模型 ................................. 20

2.1工程概况 ..................................................................................................................................................... 20 2.2巴拉溢洪道特点及实验模型 ............................................................................................................... 20

第三章 实验研究 ................................................. 23

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