COMBUSTION AND FLAME
·
2021
·
IF 4.185
Jizhen Zhu,Sixu Wang,Mohsin Raza,Yuan Feng,Jing Li,Yebing Mao,Liang Yu,Yong Qian,Xingcai Lu
Methanol is an attractive oxygenate increasingly used as primary fuel for dual-fuel combustion technology yielding beneficial thermal-efficiency and emissions in modern engines. As such, it is significant to fundamentally understand the autoignition behavior of methanol/diesel mixtures. This study measured the ignition delay times (IDTs) of methanol/diesel blends with different mixing ratios (30%, 50%, 70% methanol by mol.) on a heated shock tube and a heated rapid compression machine at temperatures of 650−1450 K, pressures of 6−20 bar, and equivalence ratios of 0.5, 1.0 and 2.0. The typical two-stage ignition characteristics with the negative temperature coefficient response were observed for dual-fuel mixtures. In general, both the total and first-stage IDTs decrease with the increment of pressure and equivalence ratio as well as diesel proportion in mixtures. The simulation results performed with a published detailed mechanism in conjunction with a tri-component diesel surrogate demonstrate generally good agreement with the experimental data at all test conditions. Moreover, a crossover of IDTs occurs at a higher temperature (~1500 K) for varying equivalence ratios, and experiment and simulation both exhibit a non-linear mixing effect of methanol addition on diesel ignition. Interestingly, simulation results clearly suggest a crossover (~940 K) for mixtures with varying methanol content at an intermediate-temperature, where the IDT of the mixture with a lower methanol ratio becomes longer as the temperature is higher than that of the crossover. Furthermore, brute-force sensitivity analyses assisted with reaction path analysis were conducted to gain deeper insights into the autoignition chemistry of dual-fuel mixtures, especially for the chemical interaction between both fuels during the low-temperature oxidation process . It is found that methanol hardly generates •OH, whereas •OH is mainly produced by the low-temperature reaction pathways of diesel. Thus, •OH is the bridge for both fuels during the ignition process. At the high methanol ratio, the H-abstraction of diesel is mainly via •HO 2 while CH 3 OH consumes a large percentage of •OH. Consequently, the competition between methanol and diesel for •OH radicals inhibits the overall reactivity of reaction network. In addition, the original data reported here lay a foundation for the development and validation of more accurate and robust dual-fuel kinetic schemes.
研究领域:
燃烧化学
·
燃料科学
·
化学动力学
·
内燃机工程
·
替代燃料技术
✓ 已验证
DOI
高影响因子
Small
·
2023
·Vol. 19
·期 40
·2303227
·
IF 13.3
YuanZhe Wu,Quan Zong,Chaofeng Liu,Yanling Zhuang,Daiwen Tao,Jiangying Wang,Jingji Zhang,Qilong Zhang,Guozhong Cao
Vanadyl phosphate (VOPO 4 ·2H 2 O) has been regarded as one of the most promising cathode materials for aqueous Zn-ion batteries due to its distinct layered structure. However, VOPO 4 ·2H 2 O has not yet demonstrated the exceptional Zn ion storage performance owing to the structural deterioration during repeated charging/discharging process and poor intrinsic conductivity. In this work, 2D sodium vanadyl phosphate (NaVOPO 4 ·0.83H 2 O, denoted as NaVOP) is designed as a cathode material for Zn-ion batteries, in which sodium ions are preinserted into the interlayer, replacing part of water. Benefiting from the in situ surface oxidization, improved electronic conductivity, and increased hydrophobicity, the NaVOP electrode exhibits a high discharge capacity of 187 mAh g −1 at 0.1 A g −1 after activation, excellent rate capability and enhanced cycling performance with 85% capacity retention after 1500 cycles at 1 A g −1 . The energy storage mechanism of the NaVOP nanoflakes based on the rapid Zn 2+ and H + intercalation pseudocapacitance are investigated via multiple ex situ characterizations.
研究领域:
材料科学
·
电化学
·
能源存储
·
无机化学
·
纳米材料
✓ 已验证
DOI
高影响因子
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
·
2017
·
IF 3.012
Haojie Zhu,Ke Yang,Hua Lan,Shangshu Qian,Haoxiang Yu,Lei Yan,Nengbing Long,Miao Shui,Jie Shu
In this work, Na 2 Ti 3 O 7 is fabricated as lithium storage material via one-step solid state reaction. Worked as anode material , Na 2 Ti 3 O 7 delivers a stable electrochemical performance with good lithium storage capability. Structural analyses show that Na 2 Ti 3 O 7 anode experiences slight volume change during electrochemical lithiation/delithiation process. Moreover, the reversibility of structural evolution is further demonstrated by in-situ X-ray diffraction technique . All these evidences prove the cycling stability of Na 2 Ti 3 O 7 as lithium storage material. Besides, the kinetic properties of the Li + ion storage in Na 2 Ti 3 O 7 are systematically investigated. The observed results reveal that Na 2 Ti 3 O 7 delivers the lithium ions diffusion coefficient in the range of 10 − 14 –10 − 12 cm 2 s − 1 during the discharge process and 10 − 15 –10 − 12 cm 2 s − 1 during the recharge process. It suggests that Na 2 Ti 3 O 7 has good lithiation/delithiation kinetics in rechargeable batteries.
研究领域:
电化学
·
材料科学
·
能源存储
·
无机化学
·
固体化学
✓ 已验证
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2021
·
IF 13.273
Bin Qin,Yifei Cai,Xiaoqing Si,Chun Li,Jian Cao,Weidong Fei,Junlei Qi
The practical application of lithium-sulfur (Li-S) batteries is impeded by the shuttle effect of intermediate polysulfides and the inherent sluggish kinetics. Herein, Mo 2 C nanocatalysts anchoring on holey graphene scaffold (Mo 2 C@HGr) is explored as a lightweight and ultrathin modified separator to conquer the above issues. The artificially customized holes on holey graphene sheets facilitate ionic transfer and electrolyte penetration, and further enhance the sulfur utilization under lean electrolyte conditions. The experimental results together with theoretic calculation demonstrate the favourable chemical adsorption ability of Mo 2 C sites that blocking the diffusion of LiPSs. Abundant triple-phase interfaces among Mo 2 C nanomediators, holey graphene and electrolyte boost the conversion kinetics of the intercepted LiPSs. As a result, the cell with Mo 2 C@HGr modified separator shows superior rate capability (836 mAh g −1 ) even at 5 C current with a negligible Mo 2 C@HGr loading of 0.08 mg cm −2 . Furthermore, ultrahigh areal capacity of 5.9 mAh cm −2 is still attained with high sulfur loading of 6 mg cm −2 under lean electrolyte operation (E/S = 5.6 µL mg −1 ). This design concept can be extended to other graphene based multifunctional nanocomposite toward the development of more practical Li-S batteries.
研究领域:
电化学
·
能源材料
·
纳米催化
·
电池技术
·
功能复合材料
✓ 已验证
DOI
高影响因子
FUEL
·
2018
·
IF 4.908
Guoqing Wang,Yuyang Li,Lei Li,Fei Qi
Cellular instability of spherically expanding methanol/air flames was investigated in a constant-volume single-chamber cylindrical combustion vessel at initial temperatures of 373–423 K, initial pressures of 1–10 atm and equivalence ratios of 0.7–2.1. Flame morphology shows that the methanol/air flames suffer from cellular instability, especially at 5–10 atm. Stability analysis was performed to determine the logarithmic growth rate of disturbance, the critical Peclet number and the critical flame radius. The influences of initial temperature, initial pressure and equivalence ratio on cellular instability were analyzed to identify the influential factors. Both experimental results and stability analysis indicate cellular instability monotonically increases with increasing temperature or pressure and non-monotonically varies with increasing equivalence ratio. The reduced critical Peclet number and flame thickness slightly destabilize the flame surface as temperature increases. The almost unchanged critical Peclet number and the greatly reduced flame thickness with increasing pressure make the critical flame radius smaller and the flame surface more unstable at high pressures. The monotonically decreased critical Peclet number and the non-monotonically varied flame thickness result in the non-monotonic variation of cellular instability in methanol/air flames versus equivalence ratio. The critical flame radius consequently increases with increasing equivalence ratio under very rich conditions, while the corresponding flame surface becomes more smooth. The non-monotonic variation of cellular instability versus equivalence ratio is anticipated to exist widely in combustion of heavy fuels .
研究领域:
燃烧学
·
热力学
·
流体力学
·
化学动力学
·
能源工程
✓ 已验证
DOI
高影响因子
COMBUSTION AND FLAME
·
2021
·
IF 4.185
Qianjin Lin,Chun Zou,Shibo Liu,Yunpeng Wang,Lixin Lu,Chao Peng
The ignition delay times (IDTs) of 2-pentanone (methyl propyl ketone , MPK) were measured at equivalence ratios of 0.5, 1.0, and 1.5, pressures of 1 bar and 5 bar, and temperatures ranging between 1227 and 1571 K. A MPK low to high-temperature model was constructed on the basis of Pieper model and Fenard model. The improvement of the model is that the rate constants of sixteen MPK decomposition and hydrogen abstraction reactions (R1–R16) obtained by the analogy-based method, were globally optimized by the Bayesian Optimization algorithm using the high-temperature IDTs. The optimized model well predicts the laminar flame speeds (measured by Li et al.) and the IDTs and species profiles in low-temperature (measured by Fenard et al.). There is no overfitting during the optimization process. Therefore, the optimization method and the optimized MPK model are reliable. The comparisons of the optimized model with Pieper model and Fenard model were performed by the reaction pathway analysis and sensitivity analysis for the predictions of the MPK profile, the low and high-temperature IDTs and the laminar flame speeds. Because of the difference in the molecular structure between MPK and 2-butanone, remaining the branching ratio among three MPK decompositions (R1–R3) and the ratio among the rate constants of the MPK hydrogen abstraction reactions by OH, H and CH 3 unchanged is unnecessary in the development of the MPK model using the analogy-based method, while the branching ratio of the hydrogen abstraction reactions at carbon 1, 3, and 5 remains unchanged. The competition among the decomposition and hydrogen abstraction reactions of MPK is intricate and crucial to the low and high-temperature oxidation . It is necessary to globally optimize the rate constants of R1-R16 based on the multidimensional experimental results, such as low and high-temperature IDTs, laminar flame speeds, and species profiles.
研究领域:
燃烧化学
·
化学动力学
·
能源工程
·
反应机理建模
·
优化算法
✓ 已验证
DOI
高影响因子
COMBUSTION AND FLAME
·
2022
·
IF 5.767
Qianjin Lin,Chun Zou,Jianghui Luo,Wenxiang Xia,Wenyu Li,Chao Peng
Ignition delay times (IDTs) for di-isopropyl ketone (DIPK) were measured at pressures of 6 and 10 atm, equivalence ratios ( ϕ ) of 0.5, 1.0, and 2, and over a temperature range of 1100 - 1500 K. In the DIPK sub-model proposed by Barari et al., DIPK⇔IC 3 H 7 +IC 3 H 7 CO (R2) was erroneously written as DIPK⇔IC 3 H 7 + IC 4 H 7 O and the consumption paths of dimethyl ketene (DMK) are missing. A DIPK sub-model was proposed on the basis of Barari model by correcting these errors, reassigning the rate coefficients of the DIPK unimolecular decomposition reactions (R1, R2), H-abstraction reactions by O ˙ H (R3, R4), fuel radical isomerization reaction (R5), and β-scission decomposition reactions (R5-R10) using the analogy method, and adopting the theoretical calculations of the H-abstraction reactions by H ˙ , C ˙ H 3 , and H O ˙ 2 (R11-R16) provided by Allen et al.. The rate coefficients of R1-R10 were globally optimized by the Bayesian optimization algorithm using the experimental IDTs and profiles of DIPK and DMK. The optimized model well predicts not only the IDTs and profiles of DIPK and DMK, but also the laminar flame speeds and the profiles of many intermediates (propyne, propylene , and methyl ketene) and small species (H 2 , CO, CH 4 ) during the pyrolysis of DIPK. The calculation using the method of Chen et al. shows that no optimized reaction violates the collision limit. The sensitivity and rate of production analysis were used to discuss the DIPK unimolecular decompositions, DIPK H-abstraction reactions, DIPK radicals isomerization and β-scission reactions, and the optimization of the DIPK sub-model.
研究领域:
燃烧化学
·
化学动力学
·
能源工程
·
反应机理建模
✓ 已验证
DOI
高影响因子
JOURNAL OF PHYSICAL CHEMISTRY A
·
2016
·
IF 2.883
Chunlong Hu,Ying Tang,Xinli Song,Zhiming Liu,Bing Zhang
The photodissociation dynamics of highly excited iodobenzene from the C band absorption has been studied by femtosecond time-resolved ion yields techniques. Detailed photodissociation routes are discussed with the aid of high-level, spin–orbit resolved ab initio calculations of 1D potential energy curves. Upon 200 nm excitation within the C band, iodobenzene molecules on 7B2 and 7B1 states decay to 7A1 and 8B2 states through internal conversion in 75 fs, with electronic energy converted into high vibrational energy of 7A1 and 8B2 states. Subsequently, 7A1 and 8B2 states decay through internal vibrational energy redistribution in 540 fs, accompanied by the excited C–I mode and the resulting cleavage of the C–I bond. The overall time for the reaction starting from the phenyl-type modes and ending in final C–I fragmentation for I(2P3/2) production is 1.2 ps.
研究领域:
物理化学
·
化学动力学
·
光化学
·
超快光谱学
·
量子化学
✓ 已验证
DOI
高影响因子
COMBUSTION AND FLAME
·
2018
·
IF 4.494
Xibin Wang,Xiangshan Fan,Kangkang Yang,Jingshan Wang,Ximing Jiao,Zhiyi Guo
s 2-methyltetrahydrofuran (MTHF) has been considered as a potential biofuel candidate for the renewable feedstock and attractive properties. In this study, the spherically propagating flames of the MTHF/isooctane-air mixtures in different blending ratios were investigated at elevated temperatures and pressures over equivalence ratios of 0.8–1.5 in a constant volume chamber using high-speed photography technique. Laminar burning velocities were calculated through nonlinear method and correlated by mixing rules as a function of initial temperature, pressure, equivalence ratio, and blending ratio. To investigate the influence of the potential interaction between MTHF and isooctane , a detailed model was established by merging the models of the two fuels and validated against laminar burning velocity, ignition delay times and flame structure. The laminar flame velocities of MTHF were observed to increase with initial temperature while the flame velocities decrease with increase in pressure. Kinetic analysis indicates that the major consumption pathways for MTHF are through H abstraction reactions at 2 and 5 sites. The H abstraction reactions at methyl group are less competitive. Unsaturated hydrocarbons and aldehydes are produced in high concentration and are the main stable intermediates of MTHF combustion. The laminar burning velocity is sensitive to the reactions of small radicals and some intermediates such as propylene and ethylene. The laminar burning velocities of MTHF/isooctane blends increase with MTHF blending ratio. The influence of blending ratio on laminar burning velocity should attribute to the chemical factors, rather than thermal or diffusion factors . MTHF oxidation generates less proportion of propylene and higher fractions of H, OH than isooctane, reflecting positive chemical effects on laminar burning velocity as MTHF blended. According to the instability analysis, the Markstein length and critical radius shows similar flame instability among different blending ratios.
研究领域:
燃烧科学
·
化学动力学
·
生物燃料
·
能源工程
·
热物理
✓ 已验证
DOI
高影响因子
ENERGY & FUELS
·
2016
·
IF 2.835
Xiangshan Fan,Xibin Wang,Jingshan Wang,Kangkang Yang
The ignition delay times of 2,3-dihydrofuran (23DHF) and 2,5-dihydrofuran (25DHF) were investigated over the temperature range of 1100 to 1635 K with pressure of 1.2, 4, and 10 atm for lean (φ= 0.5), stoichiometric, and rich (φ= 2) fuel/O2/Ar mixtures. 23DHF shows shorter ignition delay times than 25DHF under the above conditions. A modified model (M_Tran model) was presented to improve the prediction of DHF ignition. Kinetic analysis indicated that most 23DHF transforms to cyclopropane carboxaldehyde (CPCA) and further to croton aldehyde (CA) by isomerization while most 25DHF dehydrogenates to furan. Some reactions involving CA and propene show strong sensitivity for 23DHF ignition. Some reactions of furan present strong effect on 25DHF ignition. Ignition delay data between furan, 23DHF, and 25DHF were compared to reveal the effect of number and location of carbon double bonds on the ignition characteristics. The bond dissociation energies of DHF are not as strong as that of furan and are significantly influenced by the locations of carbon double bonds, causing the differences in structure stability. As a result, the ignition trends of furan and DHF in this research are furan < 25DHF < 23DHF.
研究领域:
燃烧化学
·
化学动力学
·
燃料科学
·
高温物理
✓ 已验证
DOI
高影响因子
COMBUSTION AND FLAME
·
2021
·
IF 4.185
Shiqing Kang,Wendi Dong,Wenkai Liang,Bin Yang
A recent computational study showed that iso -octane exhibits a two-stage heat release behavior in the first-stage low temperature ignition regime under certain ranges of initial temperatures and pressures. To explore this computational result, ignition delay time measurements were conducted using a rapid compression machine (RCM) at three different conditions. The experimental observations indeed substantiate the computational results of two-stage heat release in the low-temperature auto-ignition process. Comparison between experimental measurements and simulation results using three different reaction models was also conducted, showing closeness in the timing and intensity of the two-stage heat release for two of them.
研究领域:
燃烧科学
·
化学动力学
·
内燃机
✓ 已验证
DOI
高影响因子
ENERGY & FUELS
·
2024
·
IF 5.2
Na Yang,Fanqi Bu,Mengyue Gu,Yonghong Cheng,Jinying Zhang
The hydrolysis of LiAlH4 is a feasible path to supply hydrogen at subzero temperatures due to its high hydrolysis reactivity and hydrogen purity. However, the extremely fast hydrolysis reaction of LiAlH4 hindered its practical application due to its kinetic instability and safety risks caused by the exothermic effect of the reaction. Herein, hydrophobic graphene nanosheets (GNS) have been coated on the surfaces of LiAlH4 particles (LiAlH4@GNS composites) to slow the hydrolysis kinetics of LiAlH4, especially at subzero temperatures. The GNS coating processes have been found to introduce not only GNS coating but also fragmentation of LiAlH4 particles. The coating process was found to hinder the hydrolysis reaction of LiAlH4 with increasing GNS coating to 3.82 wt %, while the hydrolysis of LiAlH4 was found to increase with further GNS coating process due to significant fragmentation effects. The hydrolysis speeds of LiAlH4@GNS (D50 = 100 μm, Dδ = 1.30) with GNS coating (∼3.82 wt %) have been demonstrated to be reduced to 70% of that of pristine LiAlH4, where the conversion rates were found to be still higher than 99.0% at −40 to 0 °C. The GNS coating is considered to serve as a barrier to hinder the free diffusion of H2O molecules toward the reaction interface at the initial stage of the reaction, resulting in longer induction periods of the composites than those of pristine LiAlH4. The hydrolysis of LiAlH4@GNS has been demonstrated to follow the shrinking core model controlled by liquid film diffusion, where the GNS coating plays an important role in extending the diffusion distance and reducing the diffusion efficiency of substances within the liquid film layer.
研究领域:
材料科学
·
氢能
·
纳米材料
·
化学动力学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）