{"title":"Experimental and numerical study on the effect of diluents on laminar burning velocities of near-limit hydrogen flames at normal and reduced pressures","authors":"Senlin Lyu, Yunyang Liu, Erjiang Hu, Geyuan Yin, Zuohua Huang","doi":"10.1016/j.fuel.2025.137031","DOIUrl":null,"url":null,"abstract":"<div><div>In this study, the effects of diluents (CO<sub>2</sub>, N<sub>2</sub>, AR and HE) and pressures on laminar burning velocity (LBV) of near-limit H<sub>2</sub>/Air/diluent flames were investigated experimentally and computationally. The LBVs of H<sub>2</sub>/Air at CO<sub>2</sub> and N<sub>2</sub> dilution at varying equivalence ratios (<em>ϕ</em>) and dilution ratios (up to 52 % by volume) under normal and reduced pressures were measured using a constant volume vessel. Several H<sub>2</sub> kinetic models (FFCM-1, NUIG 2013, Davis model, Sun model, Dryer model and Li model) were compared and validated against experimental data. The fictitious dilution gas method was applied to investigate the chemical, physical, and global effects of the four diluents. Corresponding kinetic analysis was conducted to gain deep insight of the combustion process of near-limit H<sub>2</sub> flames. The results show that the measured minimum LBV for H<sub>2</sub>/Air/diluent flames is yield below 2 cm/s and the models prediction results are significantly lower than measured values. Inhibition effect on LBV is CO<sub>2</sub> > N<sub>2</sub> > AR > HE. CO<sub>2</sub> exists the strongest chemical effect to suppress LBV. HE exists the weakest inhibition effect, benefiting from its highest thermal diffusivity, as well as its low specific heat capacity. A reversal of sensitivity was observed at 40 % CO<sub>2</sub> dilution with <em>ϕ</em> = 0.8. The sensitivity of the reaction H + O<sub>2</sub> + M = HO<sub>2</sub> + M increases with increasing dilution ratio, and the diluent as the third body of the system, M, controls the rate of the reaction. The difference in rate of this reaction may be responsible for the discrepancy between model predictions and experimental values.</div></div>","PeriodicalId":325,"journal":{"name":"Fuel","volume":"406 ","pages":"Article 137031"},"PeriodicalIF":7.5000,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Fuel","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0016236125027565","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
In this study, the effects of diluents (CO2, N2, AR and HE) and pressures on laminar burning velocity (LBV) of near-limit H2/Air/diluent flames were investigated experimentally and computationally. The LBVs of H2/Air at CO2 and N2 dilution at varying equivalence ratios (ϕ) and dilution ratios (up to 52 % by volume) under normal and reduced pressures were measured using a constant volume vessel. Several H2 kinetic models (FFCM-1, NUIG 2013, Davis model, Sun model, Dryer model and Li model) were compared and validated against experimental data. The fictitious dilution gas method was applied to investigate the chemical, physical, and global effects of the four diluents. Corresponding kinetic analysis was conducted to gain deep insight of the combustion process of near-limit H2 flames. The results show that the measured minimum LBV for H2/Air/diluent flames is yield below 2 cm/s and the models prediction results are significantly lower than measured values. Inhibition effect on LBV is CO2 > N2 > AR > HE. CO2 exists the strongest chemical effect to suppress LBV. HE exists the weakest inhibition effect, benefiting from its highest thermal diffusivity, as well as its low specific heat capacity. A reversal of sensitivity was observed at 40 % CO2 dilution with ϕ = 0.8. The sensitivity of the reaction H + O2 + M = HO2 + M increases with increasing dilution ratio, and the diluent as the third body of the system, M, controls the rate of the reaction. The difference in rate of this reaction may be responsible for the discrepancy between model predictions and experimental values.
期刊介绍:
The exploration of energy sources remains a critical matter of study. For the past nine decades, fuel has consistently held the forefront in primary research efforts within the field of energy science. This area of investigation encompasses a wide range of subjects, with a particular emphasis on emerging concerns like environmental factors and pollution.