{"title":"评估热扩散贫油预混 H2/空气火焰的湍流-火焰相互作用,以实现分布式燃烧机制","authors":"","doi":"10.1016/j.combustflame.2024.113699","DOIUrl":null,"url":null,"abstract":"<div><p>Simultaneous laser-induced fluorescence of OH radicals and particle image velocimetry, and quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering measurements are used to investigate the effects of Karlovitz number (by varying the equivalence ratio) and residence time (by varying the axial measurement location) on the internal flame structures of lean premixed hydrogen/air turbulent jet flames. The turbulent flow fields, instantaneous macroscopic flame structures, and thermochemical states of a set of lean premixed hydrogen/air turbulent flames with varying initial equivalence ratio of 0.3, 0.4, and 0.45 at a constant bulk velocity of 100<!--> <!-->m/s are discussed. With an increasing equivalence ratio, the Karlovitz number derived from the turbulent flow fields decreases rapidly from 7690 to 260 and 100, determined at a downstream location of <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span> <!--> <!-->=<!--> <!-->7. At the highest Karlovitz number (i.e., the lowest equivalence ratio), a distributed burning is observed in the jet flame as turbulent transport dominates over molecular mixing, and the effects of differential diffusion and flame curvature are suppressed. With decreasing Karlovitz number, intense burning regions characterized by elevated local equivalence ratio, high water mole fraction, and super-adiabatic flame temperatures are observed in association with positive flame curvature. The same combustion diagnostics are applied to another lean premixed hydrogen/air turbulent flame with an initial equivalence ratio of 0.4 and a bulk velocity of 200<!--> <!-->m/s at selected downstream locations of <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span> <!--> <!-->=<!--> <!-->3.5, 7, 10.5, and 14 to assess the effects of developing turbulence and residence time. Corresponding Karlovitz numbers are 680, 730, 775, and 690, as the local turbulent intensity changes along downstream locations. While flame structures reveal characteristics towards distributed burning at lower <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span>, a locally intense burning region appears at higher <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span> together with positive curvature. This is mainly because the turbulence develops with increasing <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span> and the flame surface is more disturbed and curved by turbulent eddies with increasing turbulence length scales. The highly diffusive hydrogen is locally concentrated by positively curved flame surfaces, resulting in fuel-rich burning regions at a higher temperature. This indicates that, as velocity fluctuations increase in axial direction, turbulence can also promote thermo-diffusive instabilities to a certain extent, increasing the mixture inhomogeneity in temperature space by interacting with the differential diffusion effect of hydrogen at atmospheric pressure.</p><p><strong>Novelty and significance</strong></p><p>The novelty of the current work is the focus on turbulence–chemistry interactions of premixed hydrogen/air jet flames at high turbulence and ultra lean conditions. Comprehensive experimental results including the turbulent flow fields (particle image velocimetry), instantaneous flame structures (laser-induced fluorescence of OH radicals) and internal thermochemical states (quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering imaging) of hydrogen/air jet flames are analyzed and discussed. The data sets with well-characterized boundary conditions and high measurement accuracy, are crucial for validation and development of numerical simulation models.</p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":null,"pages":null},"PeriodicalIF":5.8000,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0010218024004085/pdfft?md5=7f413a4d7de9db68cca47021fc2eaf39&pid=1-s2.0-S0010218024004085-main.pdf","citationCount":"0","resultStr":"{\"title\":\"Assessing turbulence–flame interaction of thermo-diffusive lean premixed H2/air flames towards distributed burning regime\",\"authors\":\"\",\"doi\":\"10.1016/j.combustflame.2024.113699\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Simultaneous laser-induced fluorescence of OH radicals and particle image velocimetry, and quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering measurements are used to investigate the effects of Karlovitz number (by varying the equivalence ratio) and residence time (by varying the axial measurement location) on the internal flame structures of lean premixed hydrogen/air turbulent jet flames. The turbulent flow fields, instantaneous macroscopic flame structures, and thermochemical states of a set of lean premixed hydrogen/air turbulent flames with varying initial equivalence ratio of 0.3, 0.4, and 0.45 at a constant bulk velocity of 100<!--> <!-->m/s are discussed. With an increasing equivalence ratio, the Karlovitz number derived from the turbulent flow fields decreases rapidly from 7690 to 260 and 100, determined at a downstream location of <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span> <!--> <!-->=<!--> <!-->7. At the highest Karlovitz number (i.e., the lowest equivalence ratio), a distributed burning is observed in the jet flame as turbulent transport dominates over molecular mixing, and the effects of differential diffusion and flame curvature are suppressed. With decreasing Karlovitz number, intense burning regions characterized by elevated local equivalence ratio, high water mole fraction, and super-adiabatic flame temperatures are observed in association with positive flame curvature. The same combustion diagnostics are applied to another lean premixed hydrogen/air turbulent flame with an initial equivalence ratio of 0.4 and a bulk velocity of 200<!--> <!-->m/s at selected downstream locations of <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span> <!--> <!-->=<!--> <!-->3.5, 7, 10.5, and 14 to assess the effects of developing turbulence and residence time. Corresponding Karlovitz numbers are 680, 730, 775, and 690, as the local turbulent intensity changes along downstream locations. While flame structures reveal characteristics towards distributed burning at lower <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span>, a locally intense burning region appears at higher <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span> together with positive curvature. This is mainly because the turbulence develops with increasing <span><math><mrow><mi>x</mi><mo>/</mo><mi>D</mi></mrow></math></span> and the flame surface is more disturbed and curved by turbulent eddies with increasing turbulence length scales. The highly diffusive hydrogen is locally concentrated by positively curved flame surfaces, resulting in fuel-rich burning regions at a higher temperature. This indicates that, as velocity fluctuations increase in axial direction, turbulence can also promote thermo-diffusive instabilities to a certain extent, increasing the mixture inhomogeneity in temperature space by interacting with the differential diffusion effect of hydrogen at atmospheric pressure.</p><p><strong>Novelty and significance</strong></p><p>The novelty of the current work is the focus on turbulence–chemistry interactions of premixed hydrogen/air jet flames at high turbulence and ultra lean conditions. Comprehensive experimental results including the turbulent flow fields (particle image velocimetry), instantaneous flame structures (laser-induced fluorescence of OH radicals) and internal thermochemical states (quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering imaging) of hydrogen/air jet flames are analyzed and discussed. The data sets with well-characterized boundary conditions and high measurement accuracy, are crucial for validation and development of numerical simulation models.</p></div>\",\"PeriodicalId\":280,\"journal\":{\"name\":\"Combustion and Flame\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":5.8000,\"publicationDate\":\"2024-09-02\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S0010218024004085/pdfft?md5=7f413a4d7de9db68cca47021fc2eaf39&pid=1-s2.0-S0010218024004085-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Combustion and Flame\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0010218024004085\",\"RegionNum\":2,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"ENERGY & FUELS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Combustion and Flame","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0010218024004085","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
Assessing turbulence–flame interaction of thermo-diffusive lean premixed H2/air flames towards distributed burning regime
Simultaneous laser-induced fluorescence of OH radicals and particle image velocimetry, and quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering measurements are used to investigate the effects of Karlovitz number (by varying the equivalence ratio) and residence time (by varying the axial measurement location) on the internal flame structures of lean premixed hydrogen/air turbulent jet flames. The turbulent flow fields, instantaneous macroscopic flame structures, and thermochemical states of a set of lean premixed hydrogen/air turbulent flames with varying initial equivalence ratio of 0.3, 0.4, and 0.45 at a constant bulk velocity of 100 m/s are discussed. With an increasing equivalence ratio, the Karlovitz number derived from the turbulent flow fields decreases rapidly from 7690 to 260 and 100, determined at a downstream location of = 7. At the highest Karlovitz number (i.e., the lowest equivalence ratio), a distributed burning is observed in the jet flame as turbulent transport dominates over molecular mixing, and the effects of differential diffusion and flame curvature are suppressed. With decreasing Karlovitz number, intense burning regions characterized by elevated local equivalence ratio, high water mole fraction, and super-adiabatic flame temperatures are observed in association with positive flame curvature. The same combustion diagnostics are applied to another lean premixed hydrogen/air turbulent flame with an initial equivalence ratio of 0.4 and a bulk velocity of 200 m/s at selected downstream locations of = 3.5, 7, 10.5, and 14 to assess the effects of developing turbulence and residence time. Corresponding Karlovitz numbers are 680, 730, 775, and 690, as the local turbulent intensity changes along downstream locations. While flame structures reveal characteristics towards distributed burning at lower , a locally intense burning region appears at higher together with positive curvature. This is mainly because the turbulence develops with increasing and the flame surface is more disturbed and curved by turbulent eddies with increasing turbulence length scales. The highly diffusive hydrogen is locally concentrated by positively curved flame surfaces, resulting in fuel-rich burning regions at a higher temperature. This indicates that, as velocity fluctuations increase in axial direction, turbulence can also promote thermo-diffusive instabilities to a certain extent, increasing the mixture inhomogeneity in temperature space by interacting with the differential diffusion effect of hydrogen at atmospheric pressure.
Novelty and significance
The novelty of the current work is the focus on turbulence–chemistry interactions of premixed hydrogen/air jet flames at high turbulence and ultra lean conditions. Comprehensive experimental results including the turbulent flow fields (particle image velocimetry), instantaneous flame structures (laser-induced fluorescence of OH radicals) and internal thermochemical states (quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering imaging) of hydrogen/air jet flames are analyzed and discussed. The data sets with well-characterized boundary conditions and high measurement accuracy, are crucial for validation and development of numerical simulation models.
期刊介绍:
The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on:
Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including:
Conventional, alternative and surrogate fuels;
Pollutants;
Particulate and aerosol formation and abatement;
Heterogeneous processes.
Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including:
Premixed and non-premixed flames;
Ignition and extinction phenomena;
Flame propagation;
Flame structure;
Instabilities and swirl;
Flame spread;
Multi-phase reactants.
Advances in diagnostic and computational methods in combustion, including:
Measurement and simulation of scalar and vector properties;
Novel techniques;
State-of-the art applications.
Fundamental investigations of combustion technologies and systems, including:
Internal combustion engines;
Gas turbines;
Small- and large-scale stationary combustion and power generation;
Catalytic combustion;
Combustion synthesis;
Combustion under extreme conditions;
New concepts.