Article
Thermodynamics
Evan N. Rose, Vedha Nayagam, Daniel L. Dietrich, Michael C. Hicks, Uday G. Hegde, Rosa E. Padilla, Forman A. Williams
Summary: This research presents experimental observations of the two-stage autoignition dynamics of fiber-supported normal dodecane droplets in air. The results reveal the formation and propagation of cool-flame and hot-flame fronts during the autoignition process. The study provides detailed information about the locations and propagation speeds of the cool-flame and hot-flame kernels under different pressure and temperature conditions.
COMBUSTION SCIENCE AND TECHNOLOGY
(2022)
Article
Thermodynamics
Sepehr Mosadegh, Ahmadreza Ghaffarkhah, Colin van der Kuur, Mohammad Arjmand, Sina Kheirkhah
Summary: The effects of graphene oxide nanomaterials addition and oxidation level on ignition delay and burning rate of ethanol droplets were investigated experimentally. The results showed that increasing the loading concentration generally increased the ignition delay, except for ethanol doped with highly oxidized graphene. It was also found that atomization may occur for the doped ethanol droplets.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Hengyi Zhou, Yu Cheng Liu
Summary: This study extends the understanding of external group combustion for droplet clouds under two-stage autoignition conditions. It was found that fuel vapor transport is mainly supported by a thin vaporization layer near the cloud edge, and the ignition process is controlled by this layer. Three possible ignition modes were identified through parametric studies, and a new dimensionless group ignition number was proposed for better predictability.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Changfa Tao, Kai Miao, Fei Tang, Yejian Qian, Yu Zhang, Shun Meng, Chunmei Wang, Bin Jiang
Summary: The study investigates the effects of ambient temperatures and gasoline blending ratios on evaporation and combustion characteristics of lubricating oil, used lubricating oil, and the mixture of lubricating oil and gasoline using droplet suspension technology. It shows that different conditions lead to distinct characteristics of lubricating oil and used lubricating oil, and the combustion properties of the mixture of lubricating oil and gasoline vary with the gasoline component ratio.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2021)
Article
Thermodynamics
Hengyi Zhou, Yu Cheng Liu
Summary: This study extends our previous research on the external group combustion (EGC) of droplet clouds under two-stage autoignition conditions. The effects of droplet heating and different n-alkane fuel candidates are further considered. It is found that fuel volatility has little impact on the combustion modes of droplet clouds. Internal group combustion (IGC) occurs for relatively low values of the group ignition number G ig , and as G ig increases, the combustion mode can switch to EGC. IGC modes can be sustained by cool or hot flame, and their structures are analyzed in detail. A regime diagram based on G ig and ambient temperature T a is developed for all IGC modes.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Energy & Fuels
Alexis Cova-Bonillo, Rayda Patino-Camino, Juan Jose Hernandez, Magin Lapuerta
Summary: This study analyzes the impact of water concentration in ethanol on the autoignition characteristics of ethanol-diesel blends. The results indicate that water content has little effect on autoignition times in general, but acts as a reactivity inhibitor at low hydrated ethanol contents and as an autoignition enhancer at higher concentrations. The chemical effect associated with water as a third-body becomes more important at higher concentrations.
Article
Thermodynamics
Jianfu Zhao, Lei Zhou, Xiaojun Zhang, Kuangdi Li, Haiqiao Wei
Summary: The present study experimentally investigated different combustion modes and the transition mechanism in a confined combustion chamber using a H2-O2-N2 mixture with variable oxygen concentration as test fuel. It was found that the combustion mode transition was jointly influenced by the ignition delay time and flame propagation velocity. Increasing oxygen concentration led to a transition from normal combustion to end-wall detonation, and the flame propagation velocity played a crucial role in this transition.
COMBUSTION AND FLAME
(2021)
Review
Thermodynamics
Kristian Ronn, Andre Swarts, Vickey Kalaskar, Terry Alger, Rupali Tripathi, Juha Keskivali, Ossi Kaario, Annukka Santasalo-Aarnio, Rolf Reitz, Martti Larmi
Summary: The introduction of downsized, turbocharged Gasoline Direct Injection (GDI) engines in the automotive market has led to an increase in research on Low-speed Pre-ignition (LSPI) and super-knock within the last decade. LSPI is characterized by early ignition of fuel-air mixture, while super-knock is an occasional development from pre-ignition to high intensity knocking through detonation. Experimental research has included detailed approaches using different setups, and fuel and lubricant surrogates have allowed for modeling of various aspects of the phenomena. This paper provides a comprehensive review of LSPI and super-knock, discusses experimental methodologies, and suggests mitigating strategies based on fuel, oil, and engine parameters.
PROGRESS IN ENERGY AND COMBUSTION SCIENCE
(2023)
Article
Energy & Fuels
Bhavishkar Ittoo, Jong Boon Ooi, Manh-Vu Tran, Farzad Jaliliantabar, Gholam Hasan Najafi, Varghese Swamy
Summary: The addition of multiwalled carbon nanotubes (MWCNTs) to MF-diesel blends at optimal levels improves the thermal efficiency and reduces NOx emissions during combustion. Nanofuels displayed increased micro-explosion intensity and reduced occurrences, attributed to the higher surface tension and viscosity. However, the combustion characteristics deteriorate at higher MWCNTs dosing, possibly due to nanoparticle agglomeration.
Article
Thermodynamics
F. A. Williams, V. Nayagam, D. L. Dietrich
Summary: Droplet-combustion experiments conducted on the International Space Station have shown that cool-flame combustion can occur and be sustained after the extinction of a hot flame. The effective ambient atmosphere during this combustion stage may depend on the previous combustion history.
COMBUSTION AND FLAME
(2022)
Article
Energy & Fuels
Daniil S. Romanov, Ksenia Yu. Vershinina, Pavel A. Strizhak
Summary: This study analyzed the dynamic characteristics of ignition and combustion of a group of three waste-derived slurries in a low-temperature air flow. The results showed that a distance of 3-5 mm between droplet centers achieved almost simultaneous gas-phase ignition. Increasing the air flow velocity delayed the droplet ignition, while adding industrial oil reduced cooling and entrainment effects. The research suggests providing a dense droplet flow for stable ignition during low-temperature boiler start-up.
Article
Chemistry, Applied
Yonghong Yan, Rui Sun, Liutao Sun, Wenkun Zhu, Dengke Chen
Summary: This study evaluated the effect of primary air velocity on the ignition characteristics of bituminous coal and semicoke mixture, indicating that convection heating was more important than radiant heating for fuel ignition. The optimized flame stability was achieved at a primary air velocity of 18 m/s, and a recommended PAV of no more than 22 m/s for co-firing bituminous coal with a large proportion of semicoke.
FUEL PROCESSING TECHNOLOGY
(2022)
Article
Chemistry, Physical
Ziyu Wang, Chao Yan, Bowen Mei, Ying Lin, Yiguang Ju
Summary: This study investigates the oxidation of diethyl ether (DEE) under low-temperature and ultra-high-pressure conditions. The experimental data shows that DEE exhibits unusual low-temperature oxidation behavior with two negative temperature coefficient (NTC) zones. Increasing the pressure stabilizes RO2 and promotes HO2 chemistry, resulting in weaker NTC zones. The existing DEE model is updated to improve the predictability of key species, especially at intermediate temperature.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Thermodynamics
Timothy S. Krause, Vedha Nayagam, Daniel L. Dietrich, Meredith B. Colket, Forman A. Williams
Summary: This study investigates the two-stage autoignition process of n-dodecane droplets with varying ambient oxygen concentrations in oxygen-nitrogen mixtures under microgravity conditions using high-speed shadowgraphy. The results show that a cool-flame front forms first in the leaner regions farther away from the droplet, propagates towards the fuel-rich region closer to the droplet surface, and eventually encompasses the droplet. A hot-flame kernel is then initiated in the wake of the cool flame and quickly expands, establishing a diffusion flame around the droplet. The first ignition delay time is insensitive to the ambient oxygen concentration, while the second ignition delay time varies approximately as the negative 2 power of the oxygen mole fraction.
COMBUSTION SCIENCE AND TECHNOLOGY
(2023)
Article
Thermodynamics
Adam J. Susa, Ronald K. Hanson
Summary: This paper reports simultaneous schlieren and emission imaging through the side wall of a round shock tube for experimental autoignition studies. Autoignition experiments are conducted for non-dilute propane-oxygen-argon mixtures at elevated temperatures and pressures. The results show the importance of experimental design and provide valuable data for understanding autoignition processes.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Engineering, Multidisciplinary
Keisuke Yamada, Hidefumi Kataoka, Takahiro Kagami, Yuta Unno, Daisuke Segawa, Toshikazu Kadota
ATOMIZATION AND SPRAYS
(2015)
Article
Thermodynamics
K. Ishii, H. Kataoka, T. Kojima
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2009)
Article
Thermodynamics
K. Ishii, K. Morita, Y. Okitsu, S. Sayama, H. Kataoka
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2013)
