《流体力学 Fluid Mechanics》课程PPT教学课件（双语版）第十一章 气体射流

Fluid mechanics Chanter 11 Gas dittusion

1 Fluid Mechanics

流体力学 第十

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Chapter ll Gas diffusion 811-1 Introduction 811-2 Character of submerging turbulent diffusion in infinite space 811-3 kinetic analysis of diffusion in circular section §11-4 plane diffusion 8 11-5 Temperature or thickness difference of diffusion 811-6 Introduction of other diffusion in project and equipment Exercise of Chapter 11

3 Chapter 11 Gas diffusion §11–1 Introduction §11–2 Character of submerging turbulent diffusion in infinite space §11–3 kinetic analysis of diffusion in circular section §11–4 plane diffusion §11–5 Temperature or thickness difference of diffusion §11–6 Introduction of other diffusion in project and equipment Exercise of Chapter 11

第十一章气体射流 §11-1引言 §11-2无限空间淹没紊流射流的特征 §11-3圆断面射流的运动分析 s11-4平面射流 sI1-5温差或浓差射流 §11-6工程设备中常见的其他射流简介 第十一章习题

4 第十一章 气体射流 §11–1 引言 §11–2 无限空间淹没紊流射流的特征 §11–3 圆断面射流的运动分析 §11–4 平面射流 §11–5 温差或浓差射流 §11–6 工程设备中常见的其他射流简介 第十一章 习题

Gas arrosion Chapter 1l Diffusion of gas 811-1 Introduction Flow by gas diffusing from orifice, pipe mouth or slot called gas submerged diffusion flow. When orifice velocity is high fl in turbulent state, called turbulent diffusion. Most diffusion applied in engineering is turbulent diffusion of gas Diffusion describe flow velocity temperature and thickness after coming out Diffuse to infinite space, flow is not restricted by solid wall called free diffusion. Contrarily, called restricted diffusion

5 Flow by gas diffusing from orifice, pipe mouth or slot called gas submerged diffusion flow.When orifice velocity is high,flow is in turbulent state, called turbulent diffusion. Most diffusion applied in engineering is turbulent diffusion of gas. Diffusion describe flow velocity, temperature and thickness after coming out. Diffuse to infinite space, flow is not restricted by solid wall called free diffusion.Contrarily,called restricted diffusion. Chapter 11 Diffusion of gas §11-1 Introduction

气流 第十一章气体射流 §11-1引言 气体自孔口、管嘴或条缝向外喷射所形成的流动,称为气 体淹没射流。当出口速度较大,流动呈紊流状态,叫做紊流射 流。工程上所应用的射流,多为气体紊流射流。 射流讨论的是出流后的流速场、温度场和浓度场。 射流到无限大空间中,流动不受固体边壁的限制,为无限 空间射流,又称自由射流。反之,为有限空间射流,又称受限 射流

6 气体自孔口、管嘴或条缝向外喷射所形成的流动，称为气 体淹没射流。当出口速度较大，流动呈紊流状态，叫做紊流射 流。工程上所应用的射流，多为气体紊流射流。 射流讨论的是出流后的流速场、温度场和浓度场。 射流到无限大空间中，流动不受固体边壁的限制，为无限 空间射流，又称自由射流。反之，为有限空间射流，又称受限 射流。 第十一章 气体射流 §11-1 引言

Gas arrosion 8 11-2 Characteristic of turbulent diffusion in infinite space Take circular section diffusion as example talk about diffusion motion airflow diffused from circular section muzzle with radii R. Velocity of outlet section is considered uniform distributing, all are uo and is turbulent flow. Take axis of diffusion mx as axis x Owing to diffusion is turbulent flow type, transverse pulse of diffusion make exchange between mass and momentum among diffusion and medium Driving medium moving, mass flux transverse section area along x increasing, come into cone form flow diffused to around as in fig. 11-1 CAMDFo 7

7 §11-2 Characteristic of turbulent diffusion in infinite space Take circular section diffusion as example talk about diffusion motion. Airflow diffused from circular section muzzle with radii R .Velocity of outlet section is considered uniform distributing , all are u0 and is turbulent flow. Take axis of diffusion Mx as axis x Owing to diffusion is turbulent flow type, transverse pulse of diffusion make exchange between mass and momentum among diffusion and medium.Driving medium moving, mass flux , transverse section area along x increasing , come into cone form flow diffused to around, as in fig.11—1 CAMDF

气流 §11-2无限空间淹没紊流射流的特征 现以无限空间中圆断面紊流射流为例,讨论射流运动。 气流自半径为R的圆断面喷嘴喷出。出口断面上的速度 认为均匀分布,皆为4值,且流动为紊流。取射流轴线M为 x轴。 由于射流为紊流型,紊流的横向脉动造成射流与周围介质 之间不断发生质量、动量交换,带动周围介质流动,使射流的 质量流量、射流的横断面积沿κ方向不断增加,形成了向周围 扩散的锥体状流动场,如图11—1所示的锥体 CAMDE

8 §11-2 无限空间淹没紊流射流的特征 现以无限空间中圆断面紊流射流为例，讨论射流运动。 气流自半径为 R 的圆断面喷嘴喷出。出口断面上的速度 认为均匀分布，皆为 u0 值，且流动为紊流。取射流轴线Mx为 x 轴。 由于射流为紊流型，紊流的横向脉动造成射流与周围介质 之间不断发生质量、动量交换，带动周围介质流动，使射流的 质量流量、射流的横断面积沿 x 方向不断增加，形成了向周围 扩散的锥体状流动场，如图11—1所示的锥体CAMDF

Gas arrosion starting seg the main be B the core the boundary fayer E xo Fig. 11-1 Diffusion structure Structure and characteristic of turbulent diffusion

9 the starting segment the main body segment the core the boundary layer x s 0 x0 s M  o A D B C E F Fig. 11—1 Diffusion structure Structure and characteristic of turbulent diffusion

气流 起始段 主体段 B C 核心 边 界 E 层 Co 图11—1射流结构 紊流射流的结构及特性。 10

10 起始段 主体段 核心 边 界 层 x s 0 x0 s M  o A D B C E F 图 11—1 射流结构 紊流射流的结构及特性