Article
Chemistry, Physical
Yongjian Wang, Wuqiang Long, Pengbo Dong, Hua Tian, Yuanyou Tang, Yang Wang, Mingfei Lu, Weiqi Zhang
Summary: In order to improve the efficiency and reduce NOx emissions in stoichiometric hydrogen-enriched natural gas (NG) engines, a detailed 3-D simulation model based on actual boundary conditions was developed. Various methods, such as Miller valve timing, hydrogen volume fraction, and EGR rate, were proposed and investigated for knock regulation, combustion, and emission control. The study found that knock causes a bimodal characteristic of the heat release rate (HRR) curve, limiting the performance improvement of stoichiometric NG engines under high load conditions. To accurately predict and control the occurrence of the second peak of HRR, a new parameter called BI was defined. Additionally, the Miller timing with 20 degrees CA of the intake valve late closing showed better combustion performance within the knock limit, albeit with a slight increase in NOx emissions.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Thermodynamics
Seokwon Cho, Chiheon Song, Youngbok Lee, Namho Kim, Sechul Oh, Kyoungdoug Min
Summary: In order to comply with stringent CO2 regulations, internal combustion engine development has prioritized enhanced thermal efficiency, leading to engines with operating conditions more prone to knock. The limitations of current knock sensors in decomposing knock signals have necessitated the use of cross-referencing signals. This study presents a novel prediction model for knock propensity, aiming to enable active control of knock and support conventional knock sensors with a virtual knock sensor. The model incorporates predictive sub-models for in-cylinder pressure, residual gas fraction, heat loss, burn duration, and heat release rate, achieving remarkable agreement with experimental results.
INTERNATIONAL JOURNAL OF ENGINE RESEARCH
(2023)
Article
Chemistry, Physical
Esenay Arslan, Nafiz Kahraman
Summary: Natural gas, an alternative fuel, has been widely used in transportation due to its economic and environmental advantages. While it is commonly used in spark ignition engines, its application in compression ignition engines has been limited due to combustion issues. However, the addition of hydrogen to natural gas can enhance its combustion properties in compression ignition engines.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Thermodynamics
Sridhar Sahoo, Dhananjay Kumar Srivastava
Summary: CNG is considered a promising alternative fuel in the transport sector due to its high octane number and wide flammability limit. A dedicated engine is necessary to fully exploit the potential of CNG properties. Most vehicles operate in bi-fuel mode with CNG.
Article
Energy & Fuels
Farzad Poursadegh, Michael Brear, Barnaby Hayward, Yi Yang
Summary: This paper presents an experimental and numerical study on the combustion, autoignition, and octane rating of hydrogen fuel. The results show that hydrogen has significantly higher knock resistance compared to standard gasolines when providing similar energy. However, care must be taken when examining hydrogen's autoignition, knock, and abnormal combustion.
Article
Energy & Fuels
Hao Meng, Changwei Ji, Jinxin Yang, Ke Chang, Gu Xin, Shuofeng Wang
Summary: This study aims to investigate the knock of HWRE from different aspects and provide relevant information for the design of hydrogen specific WRE. The results show that factors such as ignition timing, spark plug number, spark plug location, excess air ratio, and engine speed have an impact on the knock intensity and duration of HWER.
Article
Chemistry, Physical
Weijian Zhou, Hongyuan Xi, Song Zhou, Zhao Zhang, Majed Shreka
Summary: In this study, the knock phenomenon of a reactivity controlled compression ignition (RCCI) engine fueled with natural gas/diesel is numerically investigated. The knock mechanism is explained and a strategy to suppress knock is proposed. The knock characteristics are studied by monitoring pressure oscillations at different positions in the cylinder. The results show that under high load conditions, the pressure oscillation amplitude is significant at the center and edge of the cylinder. The knock mechanism is analyzed using various methods such as pressure difference, temperature isosurface, and heat release rate. It is found that the knock in the RCCI engine is mainly caused by end-gas auto-ignition. The effects of pilot oil injection timing and compression ratio on knock are further studied. It is confirmed that diesel knock and end-gas knock can coexist in the same cycle of RCCI engine operation, and proper adjustments can effectively suppress knock.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Thermodynamics
Diego Bestel, Daniel Olsen, Anthony Marchese, Bret Windom
Summary: Natural gas is considered a promising alternative to diesel fuel in high-efficiency internal combustion engines due to its low cost and emissions. However, computational tools need to account for the complex chemistry between reactive species found in exhaust gas recirculation (EGR), including NOx, and the fuel to design these next-generation natural gas engines. The influence of NOx chemistry on natural gas engine operation remains unknown, and the development of NOx-enabled mechanisms for engine simulations is needed.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Energy & Fuels
Long Liu, Yue Wu, Yang Wang
Summary: This study revealed the unique knock characteristics and mechanism of large-bore natural gas dual-fuel marine engine, indicating that the uneven pressure distribution and heat release caused by flame jet and strong swirl are the main reasons for knock. A knock suppression method by reducing the pilot fuel was proposed based on the knock mechanism.
Article
Thermodynamics
Mahdi Aghahasani, Ayat Gharehghani, Amin Mahmoudzadeh Andwari, Maciej Mikulski, Juho Konno
Summary: By employing NGDI strategy, the compression ratio of natural gas fueled engines can be increased, resulting in reduced emissions of carbon monoxide and carbon dioxide. Under full-load conditions, the knock intensity decreases significantly as the percentage of natural gas increases.
ENERGY CONVERSION AND MANAGEMENT
(2022)
Article
Thermodynamics
Charlotte Rudolph, Burak Atakan
Summary: A novel method for energy conversion in piston engines, pyrolysis of natural gas/hydrogen mixtures for energy storage, is investigated. The addition of hydrogen allows for increased yields of certain products but also reduces storage power and efficiency.
Article
Energy & Fuels
Hee Sun Han, Ka Ram Han, Yuangang Wang, Chul Jin Kim, Chae Hoon Sohn, Chungwoo Nam
Summary: The burning of a mixture of diesel and natural gas shows potential in achieving better fuel economy and reduced emission. This study investigates the effects of blending natural gas with diesel fuel on ignition delay, heat production, and pollutant emission through numerical and experimental methods. A surrogate fuel with high accuracy is formulated to closely simulate the properties of diesel. The study also suggests an optimal mixture ratio for the dual fuel based on ignition time and acceptable pollutant emission in HCCI engines.
Article
Thermodynamics
Hao Meng, Changwei Ji, Teng Su, Jinxin Yang, Ke Chang, Gu Xin, Shuofeng Wang
Summary: This study investigates the knock characteristics of a hydrogen-fueled Wankel rotary engine (HWRE) and reveals important findings. The study finds that knock intensity, knock duration, and maximum pressure rising rate can be used to characterize the knock of the HWRE. Among these parameters, the maximum pressure rising rate is more advantageous in terms of computational cost and performance. Moreover, knock intensity has a significant impact on the timed sequence of peak knock pressure and peak in-cylinder pressure, and the mechanism of backfire caused by the knock of the HWRE is different from that of hydrogen-fueled reciprocating piston engines.
Article
Energy & Fuels
P. Boomadevi, V Paulson, Stanley Samlal, Madhanraj Varatharajan, Manigandan Sekar, Mishal Alsehli, Ashraf Elfasakhany, Siriporn Tola
Summary: This paper investigates the feasibility of using biofuels as an alternative to Jet A fuel, with experimental results showing that adding biofuels at lower proportion levels can produce positive effects.
Article
Energy & Fuels
Lin Chen, Xiao Zhang, Ren Zhang, Jinguang Li, Jiaying Pan, Haiqiao Wei
Summary: The efficiency and power output of natural gas engines are usually low. This study investigates the inner mechanism of lubricant-induced abnormal combustion in a natural gas/hydrogen engine, finding that abnormal combustion is closely related to retained hot spots and early auto-ignition leads to negative work and low thermal efficiency. It is also found that non-knocking end-gas auto-ignition is favorable for improving engine efficiency. This research provides important insights into understanding abnormal combustion in high-power natural gas/hydrogen engines.
Article
Thermodynamics
Yifan Yang, Haodong Zhang, Linye Li, Mingming Gu, Xi Xia, Fei Qi
Summary: This paper investigates the formation of a blue whirl by controlling tangential and radial airflows. By using a unique fire whirl apparatus, the blue whirl can be formed directly upon ignition without going through the transient phase. The study also discovers new flame regimes and explores the mechanism behind the formation and transition of the blue whirl.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Xiaobin Qi, Songyan Gao, Zhiping Zhu, Qinggang Lyu, Haixia Zhang
Summary: This study experimentally investigated the propagation characteristics of reverse combustion under oxygen-limited and enriched conditions. The contribution of volatiles gas-phase oxidation and char surface oxidation to reverse combustion was evaluated. The results showed that oxygen enrichment expanded the operating range of oxygen flow rate for reverse combustion and enhanced the low-temperature oxidation of the solid fuel. The findings provide a better understanding of the driving mechanism of reverse combustion and have important implications for efficient thermal conversion of solid fuels.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Bingjie Chen, Peng Liu, Bingzhi Liu, Zhandong Wang, Xiang Gao, William L. Roberts
Summary: In this study, the low temperature oxidation of 1,2,4-trimethylbenzene was investigated using experiments and numerical simulations. The results showed the presence of toxic oxygenated aromatic compounds and proposed potential formation pathways. The numerical simulations accurately predicted the mole fractions of most compounds, but some compounds were missing.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Meng Sui, Zhiheng Zhu, Fashe Li, Hua Wang
Summary: The effect of adding ferrocene as a combustion catalyst to Jatropha biodiesel on its pyrolysis and combustion performance is investigated. The results show that adding ferrocene reduces activation energy and harmful emissions while improving combustion efficiency.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Manaf Sheyyab, Mohammed Abdulrahman, Subharaj Hossain, Patrick T. Lynch, Eric K. Mayhew, Kenneth Brezinsky
Summary: Fuel surrogates, simplified representations of complex fuels, accurately model speciation results and reaction kinetics, reproduce the ignition quality and chemical functional group compositions of their parent fuels.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Yan Wang, Shumeng Xie, Hannes Bottler, Yiqing Wang, Xinyi Chen, Arne Scholtissek, Christian Hasse, Zheng Chen
Summary: This study investigates how flow affects the ignition and transition process of a cool flame. The results show that the ignition energy determines the highest temperature and the strain rate influences the flame propagation and the transition from cool flame to hot flame.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Tanusree Chatterjee, Mengyuan Wang, Goutham Kukkadapu, Chih-Jen Sung, William J. Pitz
Summary: Cycloalkanes, including cyclohexane, are important hydrocarbons in transportation fuels. However, limited oxidation data at low-to-intermediate temperatures and inadequate predictive ability of kinetic models have hindered the understanding and improvement of cyclohexane oxidation. This study provides experimental and modeling results to develop a more accurate kinetic model for cyclohexane oxidation.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Tao Wu, Erik Hagen, Haiyang Wang, Dylan J. Kline, Michael R. Zachariah, Carole Rossi
Summary: It was found that incorporating CuO into Al/I2O5 can significantly reduce the ignition time and enhance the combustion performance. The optimum composition of 80/20 wt% of I2O5/CuO shows a 30 times shorter ignition time and produces a peak pressure and pressurization rate 4 and 26 times greater than traditional Al/I2O5. A series of characterizations helped unravel the cause of improvement and propose a reaction mechanism for this ternary Al/I2O5/CuO system. This study proposes a facile, inexpensive, and efficient way to enhance the combustion performance of Al/I2O5 biocidal nanoenergetic materials.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Mahmoud Gadalla, Shervin Karimkashi, Islam Kabil, Ossi Kaario, Tianfeng Lu, Ville Vuorinen
Summary: In this study, the flame initiation process in dual-fuel spray assisted combustion is explored through scale-resolved simulations, providing numerical evidence on the initiation of premixed flames. It is found that there is a transient mixed-mode combustion phase after ignition, followed by a primarily deflagrative combustion mode. The interactions between turbulence and premixed flame front are characterized in the corrugated regime.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Neeraj Kumar Pradhan, Arindrajit Chowdhury, Debasis Chakraborty, Neeraj Kumbhakarna
Summary: In this study, a modified model for predicting the burn rate of composite solid propellants is proposed. The model has been validated against experimental and theoretical results, and it outperforms existing models in all cases considered. The model is highly robust and provides results quickly, making it highly efficient in terms of time, effort, and computational resources.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Lili Ye, Zhihe Zhang, Fan Wang, Xiaodong Wang, Yiming Lu, Lei Zhang
Summary: This study investigated the pyrolysis mechanism of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) explosive using ab initio and kinetic modeling simulations. The results showed that N-NO2 bond fission and C-H beta-scission are important channels in the decomposition of HMX.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Andrei N. Lipatnikov, Hsuchew Lee, Peng Dai, Minping Wan, Vladimir A. Sabelnikov
Summary: This study investigates the importance of thermodiffusive and hydrodynamic instabilities of laminar flames in turbulent flows through numerical simulations. The analysis suggests that laminar flame instabilities play a minor role at sufficiently high Karlovitz numbers.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Shijie Xu, Yue Qiu, Leilei Xu, Jianqing Huang, Shen Li, Elna J. K. Nilsson, Zhongshan Li, Weiwei Cai, Marcus Alden, Xue-Song Bai
Summary: Metal powder is a promising carbon-free and recyclable energy carrier. In this study, a computational model for the combustion and phase change of micron-sized iron particles was proposed and validated. The model successfully captures the melting, surface reactions, cooling, and solidification processes. The study also reveals a two-stage solidification phenomenon and identifies a diffusion-controlled mechanism during the melting process. The reaction between iron and CH4/O2/N2 flame products is found to play a significant role in the iron combustion process.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Khalid Aljohani, Abd El-Sabor Mohamed, Haitao Lu, Henry J. Curran, S. Mani Sarathy, Aamir Farooq
Summary: This study investigates the impact of exhaust gas recirculation (EGR) and NOx on the ignition delay time of oxygenated gasoline. A gasoline surrogate model is developed and the experimental data are useful for predicting fuel ignition behavior in internal combustion engines. The results show that EGR inhibits gasoline reactivity, while NOx has a promoting effect at high temperatures. This research is important for understanding the combustion behavior of gasoline in engines.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Chengcheng Ao, Jia Yan, Tong Yan, Lidong Zhang, Pan Wang
Summary: This study investigates the inhibitory effect of ammonia blended with hydrocarbon fuels on soot formation. The results show that there is a chemical interaction between ammonia and polycyclic aromatic hydrocarbons (PAHs), blocking the formation of larger PAHs.
COMBUSTION AND FLAME
(2024)