噴嘴通常是不同橫截面面積的管道,其結(jié)構(gòu)形式對射流動力學性能有很大影響。噴嘴通常用于控制從其流出的排出流體的流動速度、方向、形狀和壓力。當流體流過噴嘴時管內(nèi)的高壓氣流在工作條件下產(chǎn)生一定程度的噪聲。工業(yè)上使用的流體輸運設(shè)備如用于處理不銹鋼的高壓噴嘴,會產(chǎn)生120 dB或以上的強噪聲,嚴重污染車間的工作環(huán)境,對工人的健康和工作效率產(chǎn)生負面影響。因此,論文通過對氣流噪聲的機理和特性進行研究,設(shè)計滿足熱量傳遞的條件下較低噪聲水平的噴嘴結(jié)構(gòu)。試驗研究噴嘴構(gòu)型對高壓水射流流動影響時結(jié)果最為可靠,然而成本昂貴且周期較長,因此本文應(yīng)用渦粘性模型和二階精度的有限體積法對不同噴嘴的外部流場進行了大渦模擬,研究了不同噴嘴外部流場非定常結(jié)構(gòu)特性,具體內(nèi)容如下:首先,根據(jù)壓力、速率和噪聲之間的關(guān)系設(shè)計噴嘴的結(jié)構(gòu);其次,通過分析高壓射流引起的噪聲構(gòu)建射流模型;第三,通過數(shù)值模擬的方法對不同噴嘴結(jié)構(gòu)和射流噪聲的關(guān)聯(lián)進行了研究,計算采用直徑為0.8 mm的噴嘴,分別以不同的形式排列。采用CATIAV5軟件設(shè)計了噴嘴形狀,并利用ANSYS和FLUENT對氣流分析進行了驗證,采用計算空氣聲學解算器對噴嘴產(chǎn)生的流場進行激勵... 

【文章來源】：天津大學天津市 211工程院校 985工程院校 教育部直屬院校

【文章頁數(shù)】：112 頁

【學位級別】：碩士

【文章目錄】：
摘要
Abstract
Nomenclature
Abbreviations
Chapter 1 Introduction
    1.1 The purpose and significance of the research
    1.2 Development and research status of aero acoustics
    1.3 Research background and present situation of jet noise
    1.4 Outline of the Thesis
    1.5 A presentation on Fluid Flow
        1.5.1 Definition
        1.5.2 Types of Fluid Flow
        1.5.3 Flow Equations
        1.5.4 Area ratio
Chapter 2 Types and Characteristics of Nozzle
    2.1 Definition
    2.2 Types of nozzles
    2.3 Nozzle flows
    2.4 Introductions to Aeroacoustics
    2.5 Turbulence in nozzle
        2.5.1 Turbulent Flow Structures
        2.5.2 Turbulence Models Available in FLUENT
        2.5.3 The k–εTurbulence Models
        2.5.4 Large Eddy Simulation（LES）
        2.5.5 Boundary Layer Separation
        2.5.6 Boundary Layer and Nozzle Flow Separation
Chapter 3 Modeling Descriptions
    3.1 Governing Equations of Fluid Flow
        3.1.1 Mass is conserved（Law of Mass Conservation）
        3.1.2 Momentum is conserved（Newton's Second Law）
        3.1.3 Energy is conserved（First Law of Thermodynamics）
    3.2 Turbulence Modeling
        3.2.1Closure problem
        3.2.2 Calculating Turbulent Viscosity
        3.2.3 Eddy viscosity
    3.3 Near wall treatment and Y+value
Chapter 4 Fundamental of spray noise
    4.1 Wave equation
    4.2 Mechanism of spray noise
    4.3 Characteristics of spray noise
Chapter 5 Flow field analysis of spray noise
    5.1 Introduction
    5.2 3D Geometric modeling and parameters
    5.3 Theoretical mechanism of acoustic radiation in flow field
        5.3.1 Turbulence theory
        5.3.2 Motion equation and quasi similarity condition
        5.3.3 Turbulence mechanism
        5.3.4 Acoustic analogies
        5.3.5 Lighthill's Acoustic Analogy
        5.3.6 Ffowcs Williams& Hawking's extended analogy using permeablecontrol surface
    5.4 Turbulence model of jet flow field
        5.4.1 modeling of jet flow field
        5.4.2 Mesh generation
        5.4.3 Broadband Noise Models
        5.4.4 Broadband noise prediction based on LES
    5.5 The Interaction between a Background Flow and an Acoustics Field
    5.6 Environmental noise control
        5.6.1 Introduction
        5.6.2 Sound pressure and Sound power– Effect and Cause
        5.6.3 Relationship between Sound Pressure and Sound Power Levels
    5.7 converting sound power level to sound pressure level
    5.8 Results
Chapter 6 Summary and Prospect
    6.1 A summary of the full text
    6.2 Work prospect
Bibliography
Publication of papers and participation in scientific research
Acknowledgement



本文編號：2988024