| 1. |
- Ye, Lian, et al.
(författare)
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Feasibility analysis of plastic and biomass hydrochar for blast furnace injection
- 2023
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermal carbonization (HTC) technology upgrades combustible waste (CW) to high-quality fuel known as hydrochar. However, there is a research gap regarding the application limit of hydrochar instead of fossil fuels in blast furnaces. In this study, the physical, chemical, and metallurgical properties of hydrochar were thoroughly analyzed. The results showed that gross calorific value, grindability, ignition temperature, explosivity, combustion and gasification all improved by HTC process compared with the waste feedstocks. Moreover, the HTC process can effectively remove harmful elements (K, Na, Cl, and S) from feedstocks into liquid and gas phase without adding other reagents, reducing harmful effects in the blast furnace. Removal rates by HTC were >80% for alkali metals and >73.9% for Cl (reaching 98.18% for polyvinyl chloride hydrochar). The environmental benefit calculation shows that the CO2 emission reduction of replacing bituminous coal with 40% HTC-treated maize straw can reach 94.7 kg/tHM. The annual CO2 reduction can reach 1.7 x 107 kg and the annual coal reduction is 1.5 x 107 kg of a blast furnace. The results showed that hydrochar is a clean energy source compared with fossil fuel alternatives and meets the blast furnace injection requirements.
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| 2. |
- Dong, Qibing, et al.
(författare)
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Regulating concentration of surface oxygen vacancies in Bi 2 MoO 6 /Bi-MOF for boosting photocatalytic ammonia synthesis
- 2024
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Ingår i: Journal of Catalysis. - 0021-9517 .- 1090-2694. ; 433
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Tidskriftsartikel (refereegranskat)abstract
- Surface oxygen vacancies (OVs) engineering has been widely adopted as an effective strategy to enhance photocatalytic performance. At present, photocatalytic systems capable of precisely regulating surface OVs concentrations, which could help illuminate the effects of the surface OVs concentration on N2 fixation activity, are still scarce. Herein, bismuth-based metal organic framework (Bi-MOF) was loaded onto the surface of Bi2MoO6 (BMO) as an operable platform, and the OVs concentration in the Bi-MOF component of BMO/Bi-MOF could be regulated by reduction of bismuth ions therein. Experimental results confirm that optimum construction of OVs in the Bi-MOF promotes the photoelectrons transfer from BMO to Bi-MOF, facilitating the activation of N2 at OVs. Consequently, the optimized catalyst shows superior performance in NH3 production, which reaches 125.78 μmol h−1 g−1, 21.4 higher than that of BMO. This work underline the significance of regulating surface OVs concentration, providing inspiration for the development of efficient OVs-modified photocatalysts.
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| 3. |
- Gao, Mingming, et al.
(författare)
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Engineered 2D MXene-based materials for advanced supercapacitors and micro-supercapacitors
- 2024
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Ingår i: Materials Today. - 1369-7021 .- 1873-4103. ; 72, s. 318-358
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Forskningsöversikt (refereegranskat)abstract
- The class of two-dimensional transition metal carbides/nitrides/oxycarbides (known as MXenes) has shown great potential in energy storage applications due to their intrinsic layered structure, outstanding electrical conductivity, tunable surface chemistry, and unique physicochemical properties. This review summarizes the latest progresses of MXene-based materials for supercapacitors and micro-supercapacitors. First, state-of-the-art structural engineering strategies for the construction of novel MXene-based electrodes are highlighted, as the electrochemical performance of MXenes is influenced by their structure, such as interlayer spacing and surface functional group density. Furthermore, the charge storage mechanisms of MXene-based electrodes in different electrolytes are discussed to stimulate further design and development of tailored materials for high-performance devices. Moreover, different device fabrication technologies are summarized and the achievements of specific device geometries (e.g., fiber-shape, planar-type, and three-dimensional devices) containing MXene-based materials are critically reviewed. Finally, perspectives and outlook for the development of high-performance MXene-based electrodes in terms of material engineering, performance improvement and device innovation are provided, clearly indicating research directions for next-generation advanced energy storage devices.
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| 4. |
- Ji, Longjuan, et al.
(författare)
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Structure and thermoacoustic instability of turbulent swirling lean premixed methane/hydrogen/air flames in a model combustor
- 2024
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Ingår i: International Journal of Hydrogen Energy. - 0360-3199. ; 60, s. 890-901
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Tidskriftsartikel (refereegranskat)abstract
- The structure and thermoacoustic instability (TI) of premixed CH4/H2/air swirling flames were experimentally investigated for a range of hydrogen fraction (ηH2) up to 80% under different equivalence ratio (Φ) and swirl number (S) conditions. It is shown that the onset of TI is enhanced when increasing either ηH2, S, or Φ. The dominant frequency of TI increases dramatically with ηH2. The higher dominant frequency in the hydrogen-enriched flames can be attributed to a shorter flame length which results in a reduced flame convection time. It is observed that the unstable flames are always accompanied by the appearance of outer recirculation zone (ORZ) flame. Therefore, the flame kernel residing in the ORZ can be an indicator of the occurrence of TI. The flame front of thermoacoustic unstable flames was observed to be more wrinkled, e.g., with larger mean absolute curvature (κ abs) and local flame surface area ratio (δΣmax). Importantly, the phase-locked analysis shows that κ abs and δΣmax can be modified at different oscillation phases, and their maximum and minimum values are simultaneously achieved at phase angles θ of about 0° and 180°, respectively. Variations of κ abs and δΣmax are in phase with the heat release rate, indicating a strong correlation between the TI and flame structure modification; however, they show a phase lag of about 72° behind the pressure in this work. These results are vital when understanding and predicting the TI based on the flame structure, especially when adopting a visual detection method of the instability.
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| 5. |
- Bie, Yiming, et al.
(författare)
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Optimization of electric bus scheduling considering stochastic volatilities in trip travel time and energy consumption
- 2021
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Ingår i: Computer-Aided Civil and Infrastructure Engineering. - : Wiley. - 1093-9687 .- 1467-8667. ; 36:12, s. 1530-1548
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Tidskriftsartikel (refereegranskat)abstract
- This paper develops a vehicle scheduling method for the electric bus (EB) route considering stochastic volatilities in trip travel time and energy consumption. First, a model for estimating the trip energy consumption is proposed based on field-collected data, and the probability distribution function of trip energy consumption considering the stochastic volatility is determined. Second, we propose the charging strategy to recharge buses during their idle times. The impacts of stochastic volatilities on the departure time, the idle time, the battery state of charge, and the energy consumption of each trip are analyzed. Third, an optimization model is built with the objectives of minimizing the expectation of delays in trip departure times, the summation of energy consumption expectations, and bus procurement costs. Finally, a real bus route is taken as an example to validate the proposed method. Results show that reasonable idle times can be generated by optimizing the scheduling plan, and it is helpful to stop the accumulation of stochastic volatilities. Collaboratively optimizing vehicle scheduling and charging plans can reduce the EB fleet and delay times while meeting the route operation needs.
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| 6. |
- Cai, Xiao, et al.
(författare)
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Propagation of Darrieus-Landau unstable laminar and turbulent expanding flames
- 2021
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:2, s. 2013-2021
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Tidskriftsartikel (refereegranskat)abstract
- The propagation of laminar and turbulent expanding flames subjected to Darrieus-Landau (DL), hydrodynamic instability was experimentally studied by employing stoichiometric H2/O2/N2 flames under quiescent and turbulent conditions performed in a newly developed medium-scale, fan-stirred combustion chamber. In quiescent environment, DL unstable laminar flame exhibits three-stage propagation, i.e. smooth expansion, transition acceleration, and self-similar acceleration. The self-similar acceleration is characterized by a power-law growth of acceleration exponent, α, with normalized Peclet number, which is different from the usually suggested self-similar propagation with a constant α. The imposed turbulence advances the onset of both transition acceleration and self-similar acceleration stages and promotes the strength of flame acceleration as additional wrinkles are invoked by turbulence eddies. A DL-turbulent interaction regime is confirmed to be the classical corrugated flamelets regime. Furthermore, the DL instability significantly facilitates the propagation of expanding flames in medium and even intense turbulence. The development of DL cells is not suppressed by turbulence eddies, and it needs to be considered in turbulent combustion.
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| 7. |
- Cai, Xiao, et al.
(författare)
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Structure and propagation of spherical turbulent iron-methane hybrid flame at elevated pressure
- 2023
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Ingår i: Combustion and Flame. - 0010-2180. ; 255
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Tidskriftsartikel (refereegranskat)abstract
- In this communication we demonstrate the role of turbulence intensity in the dual-front structure and self-similar propagation of spherical turbulent iron-methane hybrid flames. We first show that iron-methane hybrid mixture, whose iron concentration is below a critical threshold for the formation of a dust flame front in laminar or weak turbulent environment, can be burned strongly with both separated dual-front and merged single-front structures in intense turbulence. It is suggested that the formation of iron flame front would be attributed to local iron concentration accumulation by preferential sampling with near-unity Stocks number (St), heat transfer enhancement of iron particles to fluid and mixing promotion of iron particles with oxidants by strong turbulence. The propagation of iron front falls behind the methane front in the leading segments which is promoted by flame stretch for sub-unity Lewis number (Le), thus the separated dual-front structure occurs. Furthermore, the strong self-similar propagation of spherical turbulent iron-methane hybrid flame was observed under different turbulence intensities (urms). Mechanistically, such strong self-similar propagation of the hybrid flame is the consequence of the couple effects of flame mode transition at high urms with near-unity St and differential diffusion for sub-unity Le.
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| 8. |
- Cai, Xiao, et al.
(författare)
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Turbulent burning velocity and its related statistics of ammoniahydrogenair jet flames at high Karlovitz number : Effect of differential diffusion
- 2023
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 39:4, s. 4215-4226
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Tidskriftsartikel (refereegranskat)abstract
- To clarify the role of differential diffusion in highly turbulent premixed flames, a series of turbulent premixed ammonia/hydrogen/air flames were investigated using the NH-PLIF diagnostics. The investigated flames have almost the same laminar burning velocity, SL, but are characterized by different Lewis number, Le, from 0.56 to 1.77. The Karlovitz number, Ka, of these flames ranges from 11 to 1052, and the turbulence intensity, u'/SL, covers from 10 to 156. It is observed that the global consumption speed, ST,GC/SL, of sub-unity Le flames is much larger than that of super-unity Le flames at high Ka, indicating that the differential diffusion plays a significant role in highly turbulent flames. The flame surface density and the area ratio of turbulent flames with different Le are, however, similar under wide turbulent conditions. The stretch factor of sub-unity Le flames is estimated to be significantly larger than that of super-unity Le cases. The enhanced ST,GC of sub-unity Le flames is suggested to be attributed to the promotion of local burning rates by the couple effect of differential diffusion and turbulent flame stretch within the flame brush, rather than the enlargement of flame surface area at high Ka. Furthermore, three correlations for the ST,GC were developed based on Damkohler's second hypothesis with consideration of the Le effect. The correlation of ST,GC/SL - (ReTLe-2)0.5 is further validated by using small-scale methane/air and large-scale ammonia/air flames at high Ka, where ReT is turbulent Reynolds number. It suggests that the ST,GC is roughly inversely proportional to the Le, and the differential diffusion effect should be included in the theoretical analysis and numerical simulation of highly turbulent flames.
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| 9. |
- Cai, Xiao, et al.
(författare)
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高Ka 数下分子扩散效应对氨气/氢气/空气预混火焰结构的影响
- 2022
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Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics. - 0253-231X. ; 43:8, s. 2025-2032
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneous planar laser induced fluorescence (PLIF) and Rayleigh scattering thermometry (RST) were applied to measure the key species and temperature fields of premixed ammonia/ hydrogen/air jet flames to investigate the effects of differential diffusion on flame structure. NH-PLIF technique was developed to properly characterize the reaction zone of ammonia flames. Three flames with similar laminar combustion characteristics but different Lewis numbers (Le) were investigated. Results show that the reaction zone are locally thickened for all flames at high Karlovitz number (Ka). Furthermore, the reaction layer thickness increases with the Le, indicating that the differential diffusion still plays a role in the turbulent combustion even in the distributed reaction zone regime.
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| 10. |
- Guo, Shilong, et al.
(författare)
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Investigation on bluff-body and swirl stabilized flames near lean blowoff with PIV/PLIF measurements and LES modelling
- 2019
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 160
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Tidskriftsartikel (refereegranskat)abstract
- Lean premixed combustion (LPC) is a promising technology for low-NOx emission, while it increases the risk of blowoff at the same time. Experiments and Large Eddy Simulations (LES) on swirl stratified lean-premixed CH4/air flames were performed to study the differences between the stable and near blowoff flame. The flow fields and instantaneous flame structures were measured by simultaneous Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (OH-PLIF). The Thickened Flame (TF) model coupled with a two-step reduced chemical mechanism was used in LES modelling. The non-dynamic formulation of sub-grid flame wrinkling model is performed well for stable condition while it cannot predict the near lean blowoff flame reasonable. Compared with the stable flame, several significant differences can be observed in the near lean blowoff flame. The height of high-temperature-zone is relatively low and the heat loss of flame attachment can be easily enhanced by the low temperature spot induced by flame-vortex interaction. The flame attachment is subject to higher excess strain rate and turbulence fluctuation. Meanwhile, a Processing Vortex Core (PVC) appears downstream of the centerline. It is concluded that lean blowoff is the result of interactions between the fuel/air mixture ignition, PVC instability and flame attachment lift-off.
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