Article
Thermodynamics
Cheng Chi, Wang Han, Dominique Thevenin
Summary: Ammonia (NH3) shows promise as a carbon-free energy carrier and can be used as a fuel in gas turbines for power generation. This study investigates the impact of molecular diffusion modeling (MDM) on turbulent premixed NH3/H2/air jet flames, focusing on flame structure, NO production, and the combined role of MDM and stretch rate. The results show that MDM has a significant influence on NO production and turbulent flame speed, while having negligible impact on major species and NO distribution. Flame curvature and strain are found to be critical factors in accurately predicting NO emission and NH3/H2/air flame propagation.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Materials Science, Multidisciplinary
R. Koike, R. Suzuki, K. Katayama, M. Higashihata, H. Ikenoue, D. Nakamura
Summary: Pulsed laser deposition (PLD) is a commonly used technique for fabricating thin films. This study visualizes SiO2 nanoparticles generated by laser ablation using two-dimensional laser scattering imaging and investigates their behavior during pressure-controlled PLD. The spatial distribution of the nanoparticles decreases with increasing ambient gas pressure, and the distribution exhibits various shapes depending on the gas species. The size and number of web-like aggregates of nanoparticles increase with pressure. The information obtained from this study is useful for optimizing conditions in nanoporous film fabrication.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2022)
Article
Energy & Fuels
Taiyu Wang, Zhenguo Wang, Jianguo Tan, Mingbo Sun, Zun Cai, Yao Liu
Summary: This study investigated the combustion characteristics of a highly-turbulent premixed jet flame influenced by a confined space. The results showed that the flame characteristics at different distances were comprehensively investigated, and a critical value for flame extinction was identified. The flame structures were classified into V-shaped flame, converging flame, and fully developed flame. The presence of intense combustion regions related to CH* and OH* reactions was observed in the confined space.
Article
Engineering, Environmental
Entong Ye, Zheng Chen, Yongyong Shi, Dan Zhang, Wenfei Li, Hong Qin, Ziming Luo, Quansheng Wu, Qian Lin, Hongyan Pan, Keliang Wang
Summary: By using polyelectrolyte membranes (SPE) as an electronic acceptor to anchor Pd catalyst, a H2O2 selectivity of 90.1% and productivity of 5764.4 mmol·gPd^-1·h^-1 were achieved. TEM, XRD, ICP-MS, XPS, CO-DRIFT, O2-TPD, synchrotron radiation, and density functional theory (DFT) simulations revealed that the electrons of Pd are transferred into polyelectrolyte membranes and Pd clusters are strongly chemisorbed on SPE, leading to enhanced H2O2 productivity and selectivity by promoting O2 adsorption and inhibiting O-O bond dissociation.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Agricultural Engineering
Yao Cheng, Kunling Liu, Yunlan Liu, Dan Ding, Jinhao Li, Fengxiu Zhang
Summary: A highly durable bio-based flame retardant, ammonium salt of glycine phosphamide phosphoric acid (AGPP), was synthesized without formaldehyde and attached to cotton fabrics by forming P-O-C bonds with cellulose. The conjugation of N and P=O in AGPP resulted in a stable structure, making it difficult to hydrolyze even during high-intensity washing, significantly improving the launderability of the treated cotton fabrics. The presence of N-P and P-O-C bonds was confirmed by FT-IR and XPS analysis. The treated cotton fabrics with 25 wt% AGPP showed a limiting oxygen index of 51.6%, which only dropped to 43.9% after 50 laundering cycles. TG, TG-FTIR, and residual char analyses indicated that AGPP altered the degradation direction of the cotton fabrics and exhibited a condensed-phase flame retardant mechanism. SEM, XRD, and mechanical property tests demonstrated that the morphology, crystal structure, and mechanical performance of the treated cotton fabrics were well maintained.
INDUSTRIAL CROPS AND PRODUCTS
(2023)
Article
Thermodynamics
Jiarui Zhang, Zhixun Xia, Likun Ma, Liya Huang, Yunchao Feng, Dali Yang
Summary: Experimental investigation was conducted on the aluminum particles turbulent jet flame in this study. The results showed that aluminum particles need to be heated within a certain distance to ignite, and the flame structure can be divided into preheating zone, flame zone, and burnout zone. Increasing the oxidizing ability can significantly improve the flame temperature and reduce the lift-off height and visible length of the flame.
Article
Thermodynamics
Andrea Aniello, Davide Laera, Sylvain Marragou, Herve Magnes, Laurent Selle, Thierry Schuller, Thierry Poinsot
Summary: This study investigates H2-air flames obtained with a laboratory scale coaxial dual-swirl injector. Two flame archetypes are observed experimentally for the same global equivalence ratio and different thermal powers. Large Eddy Simulations (LES) are used to retrieve both regimes and investigate their stabilization modes. The results provide insights into the flame structures and the unsteady transition from lifted to anchored flames.
COMBUSTION AND FLAME
(2023)
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
Energy & Fuels
Jianlei Zhang, Ligang Zheng, Jian Wang, Rongkun Pan, Hailin Jia, Yuxin Miao, Zhanwang Shi, Xi Wang
Summary: Isochoric combustion experiments were conducted to study the instabilities of CH4/H-2/CO2/O-2 flames with an equivalence ratio of 0.80. The results revealed that oxygen enrichment had a slight effect on the crack length evolution at low hydrogen fractions but a significant effect at high hydrogen fractions. Thermodiffusive instability dominated the average cell area evolution at low hydrogen fractions, while hydrodynamic instability dominated at high hydrogen fractions. The addition of hydrogen resulted in a more significant enhancement of both thermodiffusive and hydrodynamic instabilities at lower oxygen fractions. The unstable region in the R-n plane was found to be consistent with the trend of crack growth observed in the experiments.
Article
Energy & Fuels
Hongyu Lu, Shixiang Liu, Jiang Lv, Xin Li, Michael A. Delichatsios, Longhua Hu
Summary: This work investigates the flame geometrical characteristics of vertical downward turbulent jet fires in still air. The study proposes a new physical model and conducts CFD simulation to show the combustion structure. The research reveals the inner flow field and average mixture fraction of a downward jet fire and validates the CFD result with experimental data. It also discusses the differences between downward, upward, and horizontal jet fires and presents a physical model considering the initial downward momentum, flame buoyancy, and air entrainment.
Article
Thermodynamics
Weijie Zhang, Wang Han, Jinhua Wang, Zuohua Huang, Wu Jin, Jeroen van Oijen
Summary: This study models the Darmstadt multi-regime turbulent flame MRB26b using the Flamelet-Generated Manifold (FGM) in the context of Large Eddy Simulation (LES). Different databases are used to build premixed, non-premixed, and partially premixed chemical databases, and the LES-FGM results are compared with experimental data using two sub-filter closure models. The results show that the databases lead to similar modelling of major species but better predict intermediate minor species using counter-flow flame databases. The study also reveals the over-prediction of minor species using the DTF model and proposes a correction method for improvement.
COMBUSTION AND FLAME
(2023)
Article
Chemistry, Multidisciplinary
Wenqian Lin, Ruifang Shi, Jianzhong Lin
Summary: The study investigates the distribution and deposition of cylindrical nanoparticles in a turbulent pipe flow, showing that the particle concentration becomes non-uniform along the flow direction. The particles tend to align with their major axis near the flow direction, especially with increasing particle aspect ratio. Additionally, particles near the wall have a more obvious alignment with the flow direction compared to those in the center of the pipe.
APPLIED SCIENCES-BASEL
(2021)
Article
Thermodynamics
Dong Seok Jeon, Gyu Jin Hwang, Nam Il Kim
Summary: The effects of adding hydrogen to methane were investigated through the transition from laminar to turbulent regimes in non-premixed lifted flames. The lift-off heights varied depending on fuel tube diameter, jet velocity, and hydrogen ratio. The study discussed transitional phenomena and proposed an improved relationship between lift-off heights and fuel jet velocities. The blow-off mechanism and overall stabilization modes of the flames were also explained.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Wei Gao, Naian Liu, Xiaodong Xie, Haixiang Chen, Hong Zhu, Yan Jiao
Summary: This paper presents an experimental and analytical study on non-vertical round turbulent jet fire. Propane jet fire tests are conducted to measure the velocity and temperature fields of the flame, as well as determine its geometry from video images. The results show that flame entrainment is enhanced as the initial flame angle decreases, and flame deflection-induced buoyancy flow significantly influences the flame structure. A model combining a kinetic energy equation is established to analytically correlate the flame entrainment coefficient with buoyancy and streamline curvature, and the model calculations are consistent with the experimental indications. The study provides insights into flame motion and flame radiation prediction in turbulent conditions.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
M. Di Lorenzo, P. Brequigny, F. Foucher, C. Mounaim-Rousselle
Summary: The downsized spark ignition engine is a promising technology for reducing pollutants and greenhouse gas emissions by increasing the efficiency through boosting the intake air pressure. However, modeling the combustion process under drastic conditions of high pressure, high temperature, and high dilution rate remains challenging.
COMBUSTION AND FLAME
(2022)
