Article
Thermodynamics
M. Zuhaib Akram
Summary: The study investigated the impact of hydrogen on lean flammability limits and burning characteristics of n-decane using a spherical combustion chamber and Chemkin software. It was found that the effect of Ignition Energy (IE) on flame morphology decreased with increasing lambda, while hydrogen addition extended the lean limit of n-decane significantly. By consuming OH, H radical produced greatly from H-2 and CO, enhancing the reaction rates and leading to an improvement in the lean limit.
Article
Thermodynamics
Joongoo Jeon, Doyoung Shin, Wonjun Choi, Sung Joong Kim
Summary: This study investigated the extinction mechanism of lean limit hydrogen flames using the stabilized flame method, which revealed that the primary extinction of hydrogen flames occurred at the trailing edge by heat loss mechanism. The simulation also showed that a combination of conduction and recirculation flow associated with the Lewis number effect played a key role in understanding the extinction mechanism of lean limit hydrogen flames, with recirculating flow causing the stretch extinction playing a dominant role in final flame extinction.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Energy & Fuels
Kai Zhang, Sheng Shang, Xiaolin Li, Wei Gao
Summary: This paper experimentally and numerically investigates the lower flammability limits (LFLs) of NH3/H2 mixtures at different initial pressures and temperatures. It is found that the LFLs of ammonia and hydrogen decrease with an increase in initial temperature, with ammonia experiencing a greater reduction. An increase in initial pressure decreases the LFL of ammonia but increases the LFL of hydrogen. The increase of H2 reduces the LFL of the NH3/H2 mixture, consistent with Le Chatelier's Law. Prediction models for LFLs of NH3, H2, and NH3/H2 mixtures under different conditions are established. The changes in OH radicals in elementary reactions play a crucial role in affecting LFLs, with specific OH reactions for NH3 and H2 contributing to their different LFLs.
Article
Thermodynamics
Herry Lesmana, Mingming Zhu, Zhezi Zhang, Jian Gao, Junzhi Wu, Dongke Zhang
Summary: This study investigates the flammability limits of partially dissociated NH3 in air through experimental and kinetic modeling approaches. The results show that the flammability limits widen significantly with increasing degree of NH3 dissociation, leading to wider ranges compared to pure NH3. The production of key radicals like OH, H, O, and NH2 during combustion is enhanced in the presence of H2, contributing to the wider flammability limits observed near LFL and UFL.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Energy & Fuels
Kai Zhang, Xiaolin Li, Yuting Jiang, Wei Gao
Summary: The lower flammability limits (LFLs) of H2/NH3/CH3OH mixtures and their flame morphologies were studied experimentally under elevated pressures, temperatures, and blending ratios. The flame morphologies of LFLs were found to be mushroom-like, darkening with increased initial pressures and remaining unchanged with increased initial temperatures. Blending ratios had little effect on the flame morphologies, except for specific cases. The LFLs of the mixtures varied with different variables, such as the increase in H2 or NH3 and the pressure and concentration of CH3OH. A prediction formula for the LFLs of the mixtures was established with low average absolute and relative errors.
Article
Energy & Fuels
Tao Wang, He Liang, Zhenmin Luo, Bin Su, Litao Liu, Yang Su, Xuqing Wang, Fangming Cheng, Jun Deng
Summary: The study investigated the influence of mixed flammable gases on the flammability limit of methane, revealing that adding gas fuel can lower the flammability limit and increase explosion risk. Thermodynamic and chemical kinetic analyses showed that as the volume fraction of mixed gas increased, peak flame temperature and flammability exponent also gradually increased or decreased.
Article
Energy & Fuels
Xiao Yang, Mohan Li, Ziyong Yin, Zhengchang Song
Summary: This study investigates the impact of swirler vane angle (beta) on the combustion behavior of premixed lean hydrogen-air flame in a swirl micro-combustor through numerical simulations. The findings reveal that a beta of 15 degrees results in a larger lower flammability limit (LFL) compared to a beta of 0 degrees. Additionally, beta values of 30 degrees, 45 degrees, and 60 degrees show minimal differences in LFL, with all values being lower than that of beta = 0 degrees. The anchoring of the flame is primarily influenced by the corner recirculation zone (CRZ) at beta values of 0 degrees and 15 degrees, while at beta values exceeding 30 degrees, flame anchoring is mainly determined by the inner recirculation zone (IRZ). The stabilization ability of the IRZ is stronger than that of the CRZ, but excessive swirling intensity leads to an increase in the length of the IRZ, resulting in a decrease in stabilization ability. Increasing the beta enhances the outer wall temperature at relatively low inlet velocities; however, at larger inlet velocities, a high beta reduces the thermal performance and combustion efficiency of the combustor due to the downstream movement of the flame root and reaction zone. This research improves our understanding of swirling flame characteristics in micro-combustors and offers valuable insights for the design and optimization of swirl micro-combustors.
CHEMICAL ENGINEERING AND PROCESSING-PROCESS INTENSIFICATION
(2023)
Article
Energy & Fuels
Lei Zhou, Peilin Liu, Lijia Zhong, Zhonghui Feng, Haiqiao Wei
Summary: The study found that fueled pre-chamber turbulent jet ignition can enhance combustion by increasing flame speed and area growth rate. However, pre-chamber ignition fueled with hydrogen can widen the lean flammability limit in the main chamber and reduce the sensitivity of the flame to excess air.
Article
Thermodynamics
Vernon J. Mascarenhas, Christopher N. Weber, Phillip R. Westmoreland
Summary: This study focuses on predicting the Lower Flammability Limit (LFL), using methane as a reference, and utilizing mechanistic flame models. The research compares the relationship between concentration and flammability limits, and discusses the methods and challenges of flammability testing.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Energy & Fuels
De-en Song, Xianzhong Hu
Summary: The effects of CO2 on the flammability limits of ethane were investigated through experimental measurements and numerical calculations. The results show that the thermal and chemical properties of CO2 play a significant role in modifying the flammability limits of ethane.
Review
Food Science & Technology
Barbara Speranza, Angela Racioppo, Antonio Bevilacqua, Veronica Buzzo, Piera Marigliano, Ester Mocerino, Raffaella Scognamiglio, Maria Rosaria Corbo, Gennaro Scognamiglio, Milena Sinigaglia
Summary: This article discusses the impact of emerging food processing technologies on the quality and safety of fish products. Non-traditional methods such as non-thermal atmospheric plasma and pulsed electric fields are considered to better extend the shelf life of fish products while maintaining their organoleptic properties. These emerging technologies have shown good effectiveness in controlling microbial growth, as well as saving energy and time.
Article
Engineering, Multidisciplinary
Shuhei Takahashi, Rikiya Oiwa, Misuzu Tokoro, Yoshinari Kobayashi
Summary: The study investigated the flammability limits of materials with different thickness in opposed flow and found that there is a significant difference in limiting oxygen concentration (LOC) based on sample thickness. By introducing a hypothesis of heat penetration zone shape, an empirical model was established to describe the effect of sample thickness on the flammability limit.
Article
Energy & Fuels
Mathilda Maury, Didier Mathieu, Johan Jacquemin
Summary: Due to the lack of established procedures, we propose a simple method to estimate the LFL of arbitrary fuel-air mixtures based on a relationship introduced over 80 years ago. This method provides a constant fraction of the stoichiometric concentration of fuel as the LFL, except for halogen compounds. The element count on the fuel structure primarily determines the LFL values, which contrasts with the assumptions of quantitative structure-property relationship (QSPR) and group contribution (GC) approaches.
Article
Thermodynamics
Ruiguang Yu, Jie Liu, Wenkai Liang, Chung K. Law, Hewu Wang, Minggao Ouyang
Summary: An experimental and computational investigation was conducted on the flammability limits of NCA battery vent gas blended with inert gases, and the associated phenomena were studied. Simulation results agreed well with experimental data for different inert gas ratios. It was found that an absolute limit state exists at very high inert gas ratios, where the lean and rich limits merge. The study also identified the effects of inert gases on flame properties and proposed a unified flammability exponent criterion.
COMBUSTION AND FLAME
(2023)
Article
Engineering, Electrical & Electronic
Karl Strecker, Sabit Ekin, John F. O'Hara
Summary: This article develops a theoretical framework and numerical simulations to quantify the impact of atmospheric group velocity dispersion (GVD) on the error rate of wireless terahertz communication links. The research reveals that long-distance, broadband terahertz communication systems may be limited by intersymbol interference caused by GVD, rather than signal attenuation. Increasing signal strength does not improve the error rate in dispersion limited links, and theoretical predictions based solely on signal-to-noise ratio (SNR) are invalid for the broadband case.
IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY
(2022)
