Lingzhi Zheng, Miguel Figueroa-Labastida, Jesse W. Streicher, Alison M. Ferris, Ronald K. Hanson
{"title":"正庚烷火焰速度在反射冲击波后的实验测量,火焰前自燃化学反应程度可变","authors":"Lingzhi Zheng, Miguel Figueroa-Labastida, Jesse W. Streicher, Alison M. Ferris, Ronald K. Hanson","doi":"10.1016/j.combustflame.2024.113539","DOIUrl":null,"url":null,"abstract":"<div><p>The flame speeds of premixed stoichiometric <em>n</em>-heptane/21% O<sub>2</sub>-79% Ar (so-called “airgon”) flames with different extents of pre-flame auto-ignition chemistry were experimentally investigated using an extended test-time, side-wall-imaging shock tube. <em>n</em>-Heptane/airgon mixtures were impulsively heated by reflected shock waves to a temperature of 703 ± 8 K and pressure of 1.55 ± 0.05 atm, exhibiting first-stage auto-ignition at 20.1 ± 0.6 ms. Flames were spark-ignited using a laser from 0.45 ms to 39 ms after reflected-shock heating, thus probing the augmentation of flame speeds with variable extents of pre-flame auto-ignition chemistry. The fixed-initial-temperature experiments displayed multiple distinctive flame speed regimes across first-stage auto-ignition. A burned-gas flame speed (<span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>b</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span>) increase of 6% was first observed with spark-ignition at <span><math><mo>∼</mo></math></span>7 ms after reflected-shock heating. At spark-ignition timing very close to the first-stage auto-ignition, <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>b</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> displayed a sharp 24% rise, which then gradually declined to <span><math><mo>∼</mo></math></span>10% above the reference value where pre-flame chemistry is negligible. Experiments were additionally performed at 1.55 ± 0.05 atm using two fixed spark-ignition timings (0.45 ms and 25 ms after reflected-shock heating) for initial temperatures between 641 K and 771 K. In the experiments with variable initial temperatures, a non-monotonic <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>b</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> dependence on initial temperature was observed for the 25-ms experiments, which showed a maximum <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>b</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> increase of 14% relative to the 0.45-ms experiments. To provide modeling comparisons, the thermochemical time history of the reacting gas was first simulated; the species profiles and the temperature at a given residence time were then used to obtain the flame speed from 1D steady-state simulations. The multi-regime flame speed behavior was not observed in fixed-initial-temperature simulations, which predicted a single rise in flame speed only near the first-stage auto-ignition time. The simulations with variable initial temperatures qualitatively recovered the non-monotonic flame speed trend, but generally showed underprediction of flame speeds relative to experimental results. These new experiments provide insight into the effect of pre-flame chemistry on flame propagation and offer targets for improving flame modeling, potentially aiding the development of next-generation engine concepts.</p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":null,"pages":null},"PeriodicalIF":5.8000,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Experimental measurements of n-heptane flame speeds behind reflected shock waves with variable extents of pre-flame auto-ignition chemistry\",\"authors\":\"Lingzhi Zheng, Miguel Figueroa-Labastida, Jesse W. Streicher, Alison M. Ferris, Ronald K. Hanson\",\"doi\":\"10.1016/j.combustflame.2024.113539\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>The flame speeds of premixed stoichiometric <em>n</em>-heptane/21% O<sub>2</sub>-79% Ar (so-called “airgon”) flames with different extents of pre-flame auto-ignition chemistry were experimentally investigated using an extended test-time, side-wall-imaging shock tube. <em>n</em>-Heptane/airgon mixtures were impulsively heated by reflected shock waves to a temperature of 703 ± 8 K and pressure of 1.55 ± 0.05 atm, exhibiting first-stage auto-ignition at 20.1 ± 0.6 ms. Flames were spark-ignited using a laser from 0.45 ms to 39 ms after reflected-shock heating, thus probing the augmentation of flame speeds with variable extents of pre-flame auto-ignition chemistry. The fixed-initial-temperature experiments displayed multiple distinctive flame speed regimes across first-stage auto-ignition. A burned-gas flame speed (<span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>b</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span>) increase of 6% was first observed with spark-ignition at <span><math><mo>∼</mo></math></span>7 ms after reflected-shock heating. At spark-ignition timing very close to the first-stage auto-ignition, <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>b</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> displayed a sharp 24% rise, which then gradually declined to <span><math><mo>∼</mo></math></span>10% above the reference value where pre-flame chemistry is negligible. Experiments were additionally performed at 1.55 ± 0.05 atm using two fixed spark-ignition timings (0.45 ms and 25 ms after reflected-shock heating) for initial temperatures between 641 K and 771 K. In the experiments with variable initial temperatures, a non-monotonic <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>b</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> dependence on initial temperature was observed for the 25-ms experiments, which showed a maximum <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>b</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> increase of 14% relative to the 0.45-ms experiments. To provide modeling comparisons, the thermochemical time history of the reacting gas was first simulated; the species profiles and the temperature at a given residence time were then used to obtain the flame speed from 1D steady-state simulations. The multi-regime flame speed behavior was not observed in fixed-initial-temperature simulations, which predicted a single rise in flame speed only near the first-stage auto-ignition time. The simulations with variable initial temperatures qualitatively recovered the non-monotonic flame speed trend, but generally showed underprediction of flame speeds relative to experimental results. These new experiments provide insight into the effect of pre-flame chemistry on flame propagation and offer targets for improving flame modeling, potentially aiding the development of next-generation engine concepts.</p></div>\",\"PeriodicalId\":280,\"journal\":{\"name\":\"Combustion and Flame\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":5.8000,\"publicationDate\":\"2024-06-08\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Combustion and Flame\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0010218024002487\",\"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/S0010218024002487","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}
Experimental measurements of n-heptane flame speeds behind reflected shock waves with variable extents of pre-flame auto-ignition chemistry
The flame speeds of premixed stoichiometric n-heptane/21% O2-79% Ar (so-called “airgon”) flames with different extents of pre-flame auto-ignition chemistry were experimentally investigated using an extended test-time, side-wall-imaging shock tube. n-Heptane/airgon mixtures were impulsively heated by reflected shock waves to a temperature of 703 ± 8 K and pressure of 1.55 ± 0.05 atm, exhibiting first-stage auto-ignition at 20.1 ± 0.6 ms. Flames were spark-ignited using a laser from 0.45 ms to 39 ms after reflected-shock heating, thus probing the augmentation of flame speeds with variable extents of pre-flame auto-ignition chemistry. The fixed-initial-temperature experiments displayed multiple distinctive flame speed regimes across first-stage auto-ignition. A burned-gas flame speed () increase of 6% was first observed with spark-ignition at 7 ms after reflected-shock heating. At spark-ignition timing very close to the first-stage auto-ignition, displayed a sharp 24% rise, which then gradually declined to 10% above the reference value where pre-flame chemistry is negligible. Experiments were additionally performed at 1.55 ± 0.05 atm using two fixed spark-ignition timings (0.45 ms and 25 ms after reflected-shock heating) for initial temperatures between 641 K and 771 K. In the experiments with variable initial temperatures, a non-monotonic dependence on initial temperature was observed for the 25-ms experiments, which showed a maximum increase of 14% relative to the 0.45-ms experiments. To provide modeling comparisons, the thermochemical time history of the reacting gas was first simulated; the species profiles and the temperature at a given residence time were then used to obtain the flame speed from 1D steady-state simulations. The multi-regime flame speed behavior was not observed in fixed-initial-temperature simulations, which predicted a single rise in flame speed only near the first-stage auto-ignition time. The simulations with variable initial temperatures qualitatively recovered the non-monotonic flame speed trend, but generally showed underprediction of flame speeds relative to experimental results. These new experiments provide insight into the effect of pre-flame chemistry on flame propagation and offer targets for improving flame modeling, potentially aiding the development of next-generation engine concepts.
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.