{"title":"路易斯数和热膨胀对管内层流火焰回火的综合影响","authors":"Kai Huang, Louis Benteux, Wenhu Han, D. Valiev","doi":"10.3390/fluids9010028","DOIUrl":null,"url":null,"abstract":"The understanding of the boundary layer flame flashback (BLF) has considerably improved in recent decades, driven by the increasing focus on clean energy and the need to address the operational issues associated with flashback. This study investigates the influence of the Lewis number (Le) on symmetric flame shapes under the critical conditions for a laminar boundary layer flashback in cylindrical tubes. It has been found that the transformation of the flame shape from a mushroom to a tulip happens in a tube of a given radius, as the thermal expansion coefficient and Le are modified. A smaller Lewis number results in a local increase in the burning rate at the flame tip, with the flame being able to propagate closer to the wall, which significantly increases the flashback propensity, in line with previous findings. In cases with a Lewis number smaller than unity, a higher thermal expansion results in a flame propagation happening closer to the wall, thus facing a weaker oncoming flow and, consequently, becoming more prone to flashback. For Le > 1, the effect of the increase in the thermal expansion coefficient on the flashback tendency is much less pronounced.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":null,"pages":null},"PeriodicalIF":1.8000,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Combined Impact of the Lewis Number and Thermal Expansion on Laminar Flame Flashback in Tubes\",\"authors\":\"Kai Huang, Louis Benteux, Wenhu Han, D. Valiev\",\"doi\":\"10.3390/fluids9010028\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The understanding of the boundary layer flame flashback (BLF) has considerably improved in recent decades, driven by the increasing focus on clean energy and the need to address the operational issues associated with flashback. This study investigates the influence of the Lewis number (Le) on symmetric flame shapes under the critical conditions for a laminar boundary layer flashback in cylindrical tubes. It has been found that the transformation of the flame shape from a mushroom to a tulip happens in a tube of a given radius, as the thermal expansion coefficient and Le are modified. A smaller Lewis number results in a local increase in the burning rate at the flame tip, with the flame being able to propagate closer to the wall, which significantly increases the flashback propensity, in line with previous findings. In cases with a Lewis number smaller than unity, a higher thermal expansion results in a flame propagation happening closer to the wall, thus facing a weaker oncoming flow and, consequently, becoming more prone to flashback. For Le > 1, the effect of the increase in the thermal expansion coefficient on the flashback tendency is much less pronounced.\",\"PeriodicalId\":12397,\"journal\":{\"name\":\"Fluids\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.8000,\"publicationDate\":\"2024-01-19\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Fluids\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.3390/fluids9010028\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"MECHANICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Fluids","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3390/fluids9010028","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MECHANICS","Score":null,"Total":0}
引用次数: 0
摘要
近几十年来,人们对边界层火焰回火(BLF)的认识有了很大提高,其原因是对清洁能源的日益关注以及需要解决与回火相关的运行问题。本研究探讨了刘易斯数(Le)对圆柱形管内层流边界层回火临界条件下对称火焰形状的影响。研究发现,在给定半径的管子中,随着热膨胀系数和 Le 的变化,火焰形状会从蘑菇形转变为郁金香形。路易斯数越小,火焰顶端的局部燃烧率就越高,火焰可以传播到更靠近管壁的地方,这就大大增加了回火的可能性,这与之前的研究结果是一致的。在路易斯数小于 1 的情况下,较高的热膨胀会导致火焰传播更靠近墙壁,从而面对较弱的迎气流,因此更容易发生回火。当 Le > 1 时,热膨胀系数的增加对回火倾向的影响要小得多。
Combined Impact of the Lewis Number and Thermal Expansion on Laminar Flame Flashback in Tubes
The understanding of the boundary layer flame flashback (BLF) has considerably improved in recent decades, driven by the increasing focus on clean energy and the need to address the operational issues associated with flashback. This study investigates the influence of the Lewis number (Le) on symmetric flame shapes under the critical conditions for a laminar boundary layer flashback in cylindrical tubes. It has been found that the transformation of the flame shape from a mushroom to a tulip happens in a tube of a given radius, as the thermal expansion coefficient and Le are modified. A smaller Lewis number results in a local increase in the burning rate at the flame tip, with the flame being able to propagate closer to the wall, which significantly increases the flashback propensity, in line with previous findings. In cases with a Lewis number smaller than unity, a higher thermal expansion results in a flame propagation happening closer to the wall, thus facing a weaker oncoming flow and, consequently, becoming more prone to flashback. For Le > 1, the effect of the increase in the thermal expansion coefficient on the flashback tendency is much less pronounced.