Article
Thermodynamics
Yuki Murakami, Christopher B. Reuter, Omar R. Yehia, Yiguang Ju
Summary: This study investigated autoignition-assisted nonpremixed cool flames of diethyl ether (DEE) in laminar counterflow and turbulent jet flame configurations. It was found that below a critical mixture condition, the cool flame extinction limit and the low-temperature ignition limit merge, leading to autoignition-assisted cool flame stabilization. Turbulent lifted cool flames were established based on findings from laminar flame experiments and a correlation was proposed for predicting the lift-off height of these flames.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Energy & Fuels
Andy Thawko, Ziyu Wang, Ning Liu, Yiguang Ju
Summary: This short communication reports the discovery of two different self-sustaining cool flame regimes of diethyl ether (DEE) in a diffusion counterflow burner. One is a weaker autoignition-assisted cool flame near the fuel burner, and the other is a normal diffusion cool flame near the stagnation plane. The study reveals that both flame regimes are governed by the same low-temperature chain-branching reaction pathway of DEE.
Article
Thermodynamics
Yiqing Wang, Wang Han, Zheng Chen
Summary: The study investigates the propagation of unsteady stratified dimethyl ether (DME)/air cool flames in six stratification configurations and compares them with compositionally homogeneous cool flames, finding that stratification can promote or suppress cool flame propagation based on changes in equivalence ratio. Moreover, the study reveals that stratification significantly affects the competition between specific reactions and thus impacts the fuel consumption rate. The evaluation of the ATF/FGM approach suggests that the FGM method is suitable for low-temperature chemistry, while the ATF approach may require further refinement for accurately capturing cool flame propagation speeds.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Keisuke Akita, Youhi Morii, Yuki Murakami, Hisashi Nakamura, Takuya Tezuka, Kaoru Maruta
Summary: The interactions between cool flames and flames with repetitive extinction and ignition were studied in a micro flow reactor. Two different flame dynamics were observed in reactors with different inner diameters. Cool flames and FREI were spatially separated in the reactor with an inner diameter of 1 mm, while interactions between cool flames and FREI were observed in the reactor with an inner diameter of 2 mm.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Gan Xiao, Haiwen Ge, Peng Zhao
Summary: This study aims to explore flame ignition and propagation characteristics in high-temperature flame experiments conducted in a shock tube, finding that flame ignition is highly sensitive to ignition energy and initial reaction progress, with significant variations in flame behavior under different conditions. For steady-state simulation, a sufficiently short upstream and sufficiently long downstream domain are necessary to obtain desired flame solutions.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Tianhan Zhang, Adam J. Susa, Ronald K. Hanson, Yiguang Ju
Summary: The initiation, propagation, and transition of autoignition assisted spherical cool flame and double flame were studied using n-heptane/air/He mixtures. The effects of ignition Damkohler number, ignition energy, and flame curvature on spherical flame propagation were examined. Results showed different flame regimes, acceleration of cool flame speed with increasing ignition Damkohler number, and a nonlinear dependence of flame speed on stretch. The study provides physical insight and guidance for flame speed measurement in engine relevant conditions.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Thermodynamics
Suryanarayan Ramachandran, Navneeth Srinivasan, Taaresh S. Taneja, Hongyuan Zhang, Suo Yang
Summary: This study investigates the formation of cool flames at high/supercritical pressures using AMR simulations. The results show that the increase in pressure leads to a decrease in the first stage ignition delay time and significant differences in the mixture-layer profiles.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Alex Krisman, Patrick Meagher, Xinyu Zhao, Ji-Woong Park, Tianfeng Lu, Jacqueline H. Chen
Summary: This study investigates flame quenching mechanisms in aeronautical engines through numerical simulations, revealing flame shortening and high flame stretch as two extinction mechanisms, with local balance determining the propensity for local extinction.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Matthew Q. Brown, Erica L. Belmont
Summary: The study investigated the effects of ozone enhancement on n-heptane cool flames through experimental and numerical assessments. The results showed that ozone impacts low temperature kinetics and affects low temperature ignition and cool flames.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Haiou Wang, Zhuo Wang, Kun Luo, Evatt R. Hawkes, Jacqueline H. Chen, Jianren Fan
Summary: In this study, premixed combustion in a turbulent boundary layer under auto-ignitive conditions was investigated using direct numerical simulation (DNS). The research found that combustion significantly modified near-wall turbulent structures and resulted in reaction front wrinkling in both the free stream and within the boundary layer. Different combustion modes were observed in various regions, with flame propagation prevailing in the near-wall region and auto-ignition becoming more important as the wall-normal distance increases.
COMBUSTION AND FLAME
(2021)
Article
Energy & Fuels
Guoqiang Xiong, Gesheng Li, Weilin Zeng, Junjie Liang
Summary: The steady flamelet method was used in the large eddy simulation (LES) of turbulent cool flames to investigate its capability. The results showed that it accurately captured the mean and variance trends for temperature, mixture fraction, and formaldehyde, as well as described the flame morphology of the two-stream flamelet form.
Article
Thermodynamics
Yuyang Wu, Taotao Zhou, Minming Zhu, Taohong Ye, Xianhui Chen
Summary: High-resolution two-dimensional numerical simulations are performed to investigate the impact of temperature fluctuations on n-heptane/air autoignition process. The results show that temperature fluctuation affects the autoignition mode, with a shift from single-stage ignition controlled by high-temperature chemistry to coexistence of multi-stage and single-stage ignition. Heat release and ignition delay increase for the first stage, while overall heat release and total ignition delay decrease. The presence of temperature fluctuations allows for the coexistence of low-temperature chemistry, high-temperature chemistry, single-stage ignition, and two-stage ignitions.
COMBUSTION SCIENCE AND TECHNOLOGY
(2023)
Article
Thermodynamics
Yitong Zhai, Qiang Xu, Shanshan Ruan, Lidong Zhang, Cheng Xie, Zhandong Wang, S. Mani Sarathy
Summary: In this study, the low-temperature oxidation of n-dodecane was investigated using synchrotron vacuum ultraviolet photoionization mass spectrometry and gas chromatography. Various intermediates and products, including alkenes, aldehyde/keto compounds, cyclic ethers, peroxides, acids, and alcohols/ethers, were identified and characterized. The detailed structures and formation pathways of these species were proposed and discussed. These results provide valuable experimental data for the development of kinetic models for the low-temperature oxidation of n-dodecane.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Huaibo Chen, Mingyuan Tao, Qi Yang, Haiwen Ge, Peng Zhao
Summary: This study investigates the effects of boundary layers on ignition and combustion mode evolution. It finds that the first-stage ignition is minimally affected by the boundary layer, while the main ignition event is significantly dependent on the boundary layer thickness. The research also identifies novel features of autoignition and subsequent combustion mode evolution influenced by a cold boundary layer, providing useful insights for interpreting abnormal combustion in boundary layer flows.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Energy & Fuels
Yingtao Wu, Xiangdong Kong, Lihan Fei, Zhaoming Mai, Jie Liu, Chenglong Tang, Zuohua Huang
Summary: Rapid compression machines (RCMs) are widely used in autoignition chemistry investigations, but quantitative species sampling in these reactors faces challenges of accuracy and limited time. This study numerically evaluates the uncertainty of quantitative species sampling during autoignition and finds that sampled species tend to lag behind true values due to dilution. Increasing sample duration over 2 ms has limited improvement on sampling accuracy, and a 10 mm probe tube is long enough to minimize errors caused by dilution. In reaction chambers with nonideal gas disturbance, sampled gases can be seriously diluted, leading to large result deviations.
Article
Thermodynamics
Shreshtha K. Gupta, Rahul Palulli, Mohsen Talei, Robert L. Gordon, Vaibhav K. Arghode
Summary: The capability of LES sub-grid scale modelling approaches to determine near-wall CO concentration during flame-wall interaction is investigated. Pre-tabulated lookup tables for CO based on the reduced temperature and a progress variable are shown to be a promising approach, while two commonly used generalised Flame Surface Density (FSD) models underpredict CO concentration.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2022)
Article
Chemistry, Physical
Ho Lung Yip, Ales Srna, Armin Wehrfritz, Sanghoon Kook, Evatt R. Hawkes, Qing Nian Chan
Summary: This study investigates the flame evolution of autoigniting H2 jets under various simulated compression-ignition engine conditions using high-speed schlieren and OH* chemiluminescence optical methods. The results indicate that the ignition delay of the jet is highly sensitive to changes in ambient temperature, while other parameter variations have minor effects on the ignition delay. Optical imaging reveals that the flame starts from a localized kernel and then engulfs the entire jet volume before receding towards the nozzle.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Thermodynamics
Pavel Panek, Davy Brouzet, Mohsen Talei, Robert L. Gordon
Summary: This paper evaluates flame surface density modeling in the context of large-eddy simulation (LES) using a direct numerical simulation (DNS) dataset. The results suggest that significant improvement is needed for flame surface density modeling, particularly for (rho Sd)s.
COMBUSTION AND FLAME
(2022)
Article
Energy & Fuels
Minchao Han, Robert L. Gordon, Mohsen Talei, Joshua S. Lacey
Summary: This paper investigates the ignition process of inhomogeneous n-heptane sprays injected by a prototype injector designed for the Engine Combustion Network's Spray G research. The influence of chamber and fuel conditions on the flame kernel formation and flame generation probabilities are analyzed. The study finds that chamber temperature and pressure have significant impacts on ignition probability, while the effects of fuel pressure are opposite to what is expected based on existing parameters.
Article
Mechanics
Jieli Wei, Xingyu Su, Xiao Wang, Hua Zhou, Evatt R. Hawkes, Zhuyin Ren
Summary: This paper proposes a new method for modeling the mixing timescale of individual species in turbulent non-premixed flames and evaluates its predictive capability using experimental data. The results demonstrate that this new method outperforms conventional methods, making it a promising candidate for practical applications.
Article
Chemistry, Physical
Patrick Rorimpandey, Ho Lung Yip, Ales Srna, Guanxiong Zhai, Armin Wehrfritz, Sanghoon Kook, Evatt R. Hawkes, Qing Nian Chan
Summary: This study investigates the ignition and combustion characteristics of diesel pilot and hydrogen jets under simulated compression-ignition engine conditions. The results show that the injection sequence and timing between injections significantly affect the combustion process. Igniting the hydrogen jet before the diesel pilot leads to better combustion performance, while delaying the ignition of the hydrogen jet reduces its combustion efficiency.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Chemistry, Physical
Ho Lung Yip, Ales Srna, Guanxiong Zhai, Armin Wehrfritz, Sanghoon Kook, Evatt R. Hawkes, Qing Nian Chan
Summary: This study investigates the mechanisms governing H2 jet flame evolution and stabilization by controlling the jet ignition location using a laser-induced plasma. The experiments examine the flame evolution in a constant-volume combustion chamber under various ambient O2 concentrations and temperatures. The results show that a localized flame kernel forms at the laser-induced plasma and spreads to engulf the entire upstream and downstream jet volume. The flame lift-off is sensitive to ambient O2 and temperature changes, and the edge-flame deflagration into stratified premixed fuel-ambient reactant streams explains the lift-off response.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Chemistry, Physical
Xinyu Liu, Gabrielle Seberry, Sanghoon Kook, Qing Nian Chan, Evatt R. Hawkes
Summary: In this study, a parametric investigation was conducted on a hydrogen diesel dual-fuel direct injection engine. It was found that at a hydrogen energy fraction of 90%, the engine achieved high indicated mean effective pressure and efficiency, but at the expense of increased NOx emissions. The hydrogen injection timing directly influenced the combustion mode and mixture condition. By adjusting the hydrogen injection timing, the engine performance could be optimized to achieve a reduction in CO2 emissions and an increase in IMEP/efficiency.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Mechanics
Hua Zhou, Evatt R. Hawkes, Timothy C. W. Lau, Rey Chin, Graham J. Nathan, Haiou Wang
Summary: Point-particle direct numerical simulations were used to quantify the turbulence modulation and particle responses in a turbulent particle-laden jet in the two-way coupled regime. The results showed that the presence of particles both reduced and increased the gas-phase turbulent kinetic energy in different regions. The particle response to the gas-phase flow was found to be stronger in the axial velocity component.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Xinbei Dou, Mohsen Talei, Yi Yang
Summary: This study investigates the impact of the near-wall temperature gradient on hydrogen auto-ignition characteristics. The simulations show that the near-wall temperature gradient greatly affects the onset and intensity of the auto-ignition event. Accurate modeling of the near-wall temperature gradient is necessary for simulations of hydrogen end-gas auto-ignition.
Article
Chemistry, Physical
MohammadReza Yosri, Rahul Palulli, Mohsen Talei, Joel Mortimer, Farzad Poursadegh, Yi Yang, Michael Brear
Summary: This paper presents URANS simulations of a large bore, hydrogen-fuelled DISI engine under different spark and start of injection timings. The simulations validate four out of six cases with experimental data and demonstrate that advanced spark timing leads to autoignition. Different start of injection timings show flame propagation involving a spark-initiated flame and an autoignition generated flame. The case with late injection timing features poor mixing and slower combustion.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Thermodynamics
Xingyu Su, Jieli Wei, Xiao Wang, Hua Zhou, Evatt R. Hawkes, Zhuyin Ren
Summary: This study proposes a new model called the KerM model for TPDF simulations of a turbulent non-premixed ethylene flame. By selecting mixing particle pairs based on their distance in composition space normalized by a characteristic kernel size, the KerM model features controllable localness. Comparisons with a direct numerical simulation data set show that the KerM model exhibits better performance in predicting the overall combustion process of the flame compared to the conventional MC model.
COMBUSTION AND FLAME
(2023)
Article
Energy & Fuels
Muhammad Umair Manzoor, MohammadReza Yosri, Mohsen Talei, Farzad Poursadegh, Yi Yang, Michael Brear
Summary: This work presents a numerical study of normal and knocking combustion of hydrogen in a cooperative fuel research (CFR) engine. The study is the first to simulate this problem in a CFR engine. Using the RANS framework, a single compression ratio and four different spark timings are considered to investigate the transition from normal to knocking combustion.
Article
Engineering, Civil
Jianhong Lin, Hua Zhou, Evatt R. Hawkes, Man-Ching Ma, Guan H. Yeoh
Summary: This study aims to investigate the turbulence-radiation interaction in underventilated turbulent line fires and its effect on radiation. The results show that the turbulence-radiation interaction significantly contributes to the radiation in all tested oxygen concentrations. The study emphasizes the importance of including a subgrid-scale TRI model in accurately predicting radiation fields in fires with local extinction.
FIRE SAFETY JOURNAL
(2023)
Article
Thermodynamics
Zisen Li, Evatt R. Hawkes, Armin Wehrfritz, Bruno Savard
Summary: Transported probability density function (TPDF) methods are suitable for modelling turbulent reactive flows. One of the challenges is accurately modelling molecular mixing terms. In this study, three multiple mapping conditioning (MMC)-like mixing models are examined using direct numerical simulation (DNS) datasets. The results show that these mixing models can predict flame extinction and reignition, and can be tuned to achieve a desired level of localness.
COMBUSTION AND FLAME
(2023)