المؤلفون: Wang, Chengming, Wang, Haiou, Luo, Kun, Fan, Jianren

المصدر: Energies (19961073); Oct2023, Vol. 16 Issue 19, p6985, 19p

مصطلحات موضوعية: LARGE eddy simulation models, HYDROGEN flames, FLAME, AMMONIA, TURBULENT jets (Fluid dynamics), ABSOLUTE value

مستخلص: Ammonia is a promising carbon-free fuel. However, one of the main challenges for ammonia combustion is the high level of NO emissions. In this study, simulations were conducted for ammonia/air laminar counterflow flames and turbulent non-premixed jet flames in the KAUST high-pressure combustion duct (HPCD) at a pressure of 5 bar, with two ammonia cracking ratios of 14% and 28%. The influence of ammonia cracking ratio on the flame structure and NO formation mechanism were examined. The laminar counterflow flame results showed that HNO is one of the most critical species related to NO formation and NO is mainly generated through the path of NH 2 → NH → HNO → NO . For the turbulent flames, the flamelet/progress variable (FPV) approach was employed in the context of large eddy simulations (LES) for high-fidelity simulations. The simulation results were compared with the measured data with promising agreements, which proves the accuracy of the FPV method for the present flames. It was shown that with increasing cracking ratio, not only the flame reactivity is enhanced, but also the generation of NO is increased. The correlation between NO and HNO is weaker when compared to that between NO and radicals such as O , H and OH in the entire flame. Through the distribution of NO source terms, it was found that the NO source term has a higher absolute value in the upstream region and the absolute value rapidly decreases with increasing streamwise distance. The total NO source term is positive in the fuel-lean zone and shows negative values in the fuel-rich zone. [ABSTRACT FROM AUTHOR]

: Copyright of Energies (19961073) is the property of MDPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Wang, Siyuan, Wang, Haiou, Luo, Kun, Fan, Jianren

المصدر: Energies (19961073); Feb2023, Vol. 16 Issue 3, p1065, 17p

مصطلحات موضوعية: PHASE transitions, FLAME, CHEMICAL reactions, DIFFUSION, CRITICAL temperature, DIFFUSION coefficients, OFFICES

مستخلص: In this paper, a large-eddy simulation (LES) of turbulent non-premixed LO2/CH4 combustion under transcritical conditions is performed based on the Mascotte test rig from the Office National d'Etudes et de Recherches A e ´ rospatiales (ONERA), and the aim is to understand the effects of differential diffusion on the flame behaviors. In the LES, oxygen was injected into the environment above the critical pressure while the temperature was below the critical temperature. The flamelet/progress variable (FPV) approach was used as the combustion model. Two LES cases with different species diffusion coefficient schemes—i.e., non-unity and unity Lewis numbers—for generating the flamelet tables were carried out to explore the effects of differential diffusion on the flame and flow structures. The results of the LES case with non-unity Lewis numbers were in good agreement with the experimental data. It was shown that differential diffusion had evident impacts on the flame structure and flow dynamics. In particular, when unity Lewis numbers were used to evaluate the species diffusion coefficient, the flame length was underestimated and the flame expansion was more significant. Compared to laminar counterflow flames, turbulence in jet flames allows chemical reactions to take place in a wider range of mixture fractions. The density distributions of the two LES cases in the mixture fraction space were very similar, indicating that differential diffusion had no significant effects on the phase transition under transcritical conditions. [ABSTRACT FROM AUTHOR]

: Copyright of Energies (19961073) is the property of MDPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Sun, Liyan, Lin, Junjie, Kong, Dali, Luo, Kun, Fan, Jianren

المصدر: Energies (19961073); Mar2022, Vol. 15 Issue 6, p1973-1973, 11p

مصطلحات موضوعية: CHEMICAL-looping combustion, ENDOTHERMIC reactions, EXOTHERMIC reactions, COMPUTER simulation, OXYGEN carriers, CARBON emissions

مستخلص: Chemical looping combustion is one novel technology for controlling CO 2 emission with a low energy cost. Due to a lack of understanding of the detailed and micro behavior of the CLC process, especially for a three dimensional structure, numerical simulations are carried out in this work. The configuration is built according to the experimental unit and gaseous fuel is used in this work. A two-fluid model considering heterogeneous reactions is established, and the flow behaviour and reaction characteristics are obtained. The temperature in the air reactor increases with height owing to the exothermic reaction of the xidation of the oxygen carrier, while the temperature in the fuel reactor decreases with height due to the endothermic reaction. The oxidation level of the oxygen carrier is obtained by simulation, which is hard for measurement, and the difference between the inlet and outlet is 0.065. The influences of the operating temperature and injection rate of fuel are presented to understand the performance of the system. The highest fuel conversion rate reaches 0.92 under high operating temperature. The numerical results are helpful for acquiring insight on the flow and reactive behaviour of CLC reactors. [ABSTRACT FROM AUTHOR]

: Copyright of Energies (19961073) is the property of MDPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Sun, Liyan, Lin, Junjie, Kong, Dali, Luo, Kun, Fan, Jianren

المصدر: Energies (19961073); Jan2022, Vol. 15 Issue 1, p321, 1p

مصطلحات موضوعية: FLUID dynamics, METHANATION, FLUIDIZED bed reactors, TUBES, CHEMICAL equilibrium

مستخلص: CO methanation is an exothermic process, and heat removal is an essential issue for the methanation reactor. Numerical studies were carried out to investigate the performance of a 3D fluidized bed methanation reactor with immersed cooling tubes. The simulations were carried out in the frame of the Euler–Euler model to analyze the performance of the reactor. The influences of operating temperatures were studied to understand the reaction characteristics. The temperature increases rapidly neared the inlet due to the reactions. The immersed tubes were effective at removing the reaction heat. The chemical equilibrium state was achieved with an operating temperature of 682 K for the case with immersed tubes. Different control mechanisms can be found during the process of increasing and decreasing the temperature. The reaction kinetic is the dominate factor for the cases with lower temperatures, while the chemical equilibrium will play a more important role at high temperature conditions. The configuration with staggered tubes is beneficial for heat removal. [ABSTRACT FROM AUTHOR]

: Copyright of Energies (19961073) is the property of MDPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Sun, Liyan¹ (AUTHOR) liyan.sun@toulouse-inp.fr, Luo, Kun² (AUTHOR) zjulk@zju.edu.cn, Fan, Jianren² (AUTHOR) fanjr@zju.edu.cn

المصدر: Energies (19961073). Nov2021, Vol. 14 Issue 21, p7095. 1p.

مصطلحات موضوعية: *SYNTHETIC natural gas, *METHANATION, *FLUIDIZED bed reactors, *FLUIDIZED-bed combustion, *HEAT of reaction, *NATURAL gas production

مستخلص: The production of synthetic natural gas (SNG) via methanation has been demonstrated by experiments in bench scale bubbling fluidized bed reactors. In the current work, we focus on the scale-up of the methanation reactor, and a circulating fluidized bed (CFB) is designed with variable diameter according to the characteristic of methanation. The critical issue is the removal of reaction heat during the strongly exothermic process of the methanation. As a result, an interconnected bubbling fluidized bed (BFB) is utilized and connected with the reactor in order to cool the particles and to maintain system temperature. A 3D model is built, and the influences of operating temperature on H2, CO conversion and CH4 yield are evaluated by numerical simulations. The instantaneous and time-averaged flow behaviors are obtained and analyzed. It turns out that the products with high concentrations of CH4 are received at the CFB reactor outlet. The temperature of the system is kept under control by using a cooling unit, and the steady state of thermal behavior is achieved under the cooling effect of BFB reactor. The circulating rate of particles and the cooling power of the BFB reactor significantly affect the performance of reactor. This investigation provides insight into the design and operation of a scale-up methanation reactor, and the feasibility of the CFB reactor for the methanation process is confirmed. [ABSTRACT FROM AUTHOR]

المؤلفون: Pang, Liping¹ (AUTHOR) pangliping@buaa.edu.cn, Luo, Kun¹ (AUTHOR) luokun@buaa.edu.cn, Yu, Shizhao² (AUTHOR) ysz_sky@163.com, Ma, Desheng¹ (AUTHOR) madesheng@buaa.edu.cn, Zhao, Miao¹ (AUTHOR) huanshuiyy@163.com, Mao, Xiaodong³ (AUTHOR) maoxiaodong@sau.edu.cn

المصدر: Energies (19961073). Nov2020, Vol. 13 Issue 22, p6129. 1p.

مصطلحات موضوعية: *HEAT transfer, *AVIONICS, *VAPOR compression cycle, *NUSSELT number

مستخلص: In this paper, the liquid cooling and vapor compression refrigeration system based on an Antifreeze-R134a Heat Exchanger (ARHEx) was applied to the thermal management system for high-power avionics in helicopters. The heat transfer performance of the ARHEx was studied. An experimental prototype of ARHEx was designed and established. A series of experiments was carried out with a ground experimental condition. A heat transfer formula for the antifreeze side in the ARHEx was obtained by means of the coefficient of Nusselt number with experimental analysis. The performance of heat transfer and pressure drop for the refrigerant side of the ARHEx was deduced for the given condition. [ABSTRACT FROM AUTHOR]

المؤلفون: Lin, Junjie¹ (AUTHOR) linjunjie@zju.edu.cn, Luo, Kun¹ (AUTHOR) zjulk@zju.edu.cn, Wang, Shuai¹ (AUTHOR), Sun, Liyan¹ (AUTHOR), Fan, Jianren¹ (AUTHOR)

المصدر: Energies (19961073). Sep2020, Vol. 13 Issue 17, p4442. 1p.

مصطلحات موضوعية: *CRITICAL velocity, *PARTICLE size distribution, *BUSINESS consultants

مستخلص: The behavior of solid mixing dynamic is of profound significance to the heat transfer and reaction efficiencies in energy engineering. In the current study, the solid mixing characteristics of binary particles in the bubbling fluidized bed are further revealed at particle-scale. Specifically, the influences of gas superficial velocity, Sauter mean diameter (SMD) in the system and the range distribution of particle sizes on the performance of mixing index are quantitatively explored using a computational fluid dynamics-discrete element method (CFD-DEM) coupling model. The competition between solid segregation and the mixing of binary particles is deeply analyzed. There is a critical superficial velocity that maximizes the mixing index of the binary mixture in the bubbling fluidized bed. Solid mixing performs more aggressive when below the critical velocity, otherwise solid segregation overtakes mixing when above this critical velocity. Moreover, superficial velocity is a major factor affecting the mixing efficiency in the binary bubbling fluidized bed. Additionally, the mixing behavior is enhanced with the decrease of SMD while it is deteriorated in the binary system with a wide range of particle size distribution. Therefore, it is highly recommended to perform a binary particle system with smaller SMD and closer particle size distribution for the purpose of enhancing the mixing behavior. The significant understanding of mixing characteristics is expected to provide valuable references for the design, operation, and scale-up of binary bubbling fluidized bed. [ABSTRACT FROM AUTHOR]