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Stability and Emission Characteristics of Ammonia/Air Premixed Swirling Flames with Rotating Gliding Arc Discharge Plasma

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SSRN 2022年

作者： Ju, Rongyuan Wang, Jinhua Zhang, Meng Mu, Haibao Zhang, Guanjun Yu, Jinlu Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Electrical Insulation and Power Equipment School of Electrical Engineering Xi’an Jiaotong University Xi’an710049 China School of Aeronautics Engineering Air Force Engineering University Xi’an710038 China

Ammonia received increased attention as a carbon-free fuel and hydrogen carrier. Poor combustion stability and high NOx emission are the main issue for ammonia combustion. Effects of rotating gliding arc (RGA) discharge plasma on the flame stability and NOx emission of NH3/air premixed swirling flames were investigated. The discharge characteristics of the RGA were studied. The flame stabilization mechanisms by plasma were revealed and analyzed according to the flame structure transition and the distribution of key intermediate OH radicals. The NOx emissions were measured by the Gasmet DX4000 Fourier Transform Infrared (FTIR) gas analyzer. Results showed that the RGA discharge plasma can enhance the stability and extend the lean blow-off (LBO) limits from 0.6 to approximately 0.43-0.57. A hysteresis phenomenon about the transition between the lift-off flame and the attached flame was observed without plasma and disappeared with plasma activation. The plasma reduces NO and NO2 emissions mainly due to the kinetic and cracking effects of plasma. Extremely low NO emission below 300 ppm can be observed for very lean ammonia flames with an equivalence ratio (f) lower than 0.6, which are stabilized by plasma, while a large amount of unburned NH3 emission is accompanied. © 2022, The Authors. All rights reserved.

关键词： Ammonia

Thermodynamic Analysis of a Hybrid Energy System Coupling Solar Organic Rankine Cycle and Ground Source Heat Pump: Exploring Heat Cascade Utilization

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SSRN 2023年

作者： Chen, Liangqi Yue, Huifeng Wang, Jiangfeng Lou, Juwei Wang, Shunsen Guo, Yumin Deng, Bohao Sun, Lu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China China United Northwest Institute for Engineering Design & Research Co. Ltd Xi’an710077 China School of Human Settlements and Civil Engineering Xi'an Jiaotong University Xi’an710049 China

The demand for efficient utilization of renewable energy is growing and the hybrid energy system driven by solar and geothermal energy is a significant way to achieve carbon neutrality. This paper presents a hybrid energy system coupling solar organic Rankine cycle (S-ORC) with ground source heat pump (GSHP) for heating and power supply to explore the heat cascade utilization. In the hybrid energy system, the ground heat exchanger (GHE) is shared by the S-ORC and GSHP systems and the waste heat from the condenser of S-ORC is recovered to enhance the coefficient of performance (COP) of GSHP. A mathematical model is optimized to analyze the parametric effects on thermodynamic performance. The results indicate that the COP of the hybrid energy system can be improved up to 6.5 which shows the obvious advantage compared to 2.8 of the stand-alone GSHP system. Furthermore, the hybrid energy system can obtain optimum exergy efficiency by matching ground source temperature and condensation temperature in the ORC unit. For a building of 3000m2 with heating and power supply, multi-objective optimization is carried out to obtain the optimal design performance that the net power output, thermal efficiency and exergy efficiency are 180.0kW, 27.5%, and 9.2% respectively. © 2023, The Authors. All rights reserved.

关键词： Geothermal heat pumps

A review on thermal application of metal foam

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Science China(Technological Sciences) 2020年第12期63卷 2469-2490页

作者： CHEN Kang GUO LieJin WANG Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China Institute of Solar Engineering Technology Northwest Engineering Corporation LimitedPowerChinaXi’an 710065China School of Environmental Science and Engineering Donghua UniversityShanghai 201620China

Heat exchangers embedded with metal foam are drawing increasing attention in the thermal application field,due to the performance of low density,large ratio of surface area to volume as well as high thermal conductivity. In these applications,compact heat exchanger,solar thermal facilities and thermal energy storage are the three core components. This paper focuses on the lasted advances in thermal applications,presenting a review of theoretical and experimental progress over metal foam in thermal application. The empirical and theoretical models for pressure drop,heat transfer coefficient and performance evaluation criteria of compact heat exchangers with metal foam are reviewed and discussed,especially different optimized *** is a trade-off between heat transfer enhancement and increase of pressure drop. Some exploratory work performed by present authors are also introduced. The manufacturing,heat transfer and flow characteristics of tube bundle wrapped with metal foam are taken into account for optimization of heat exchanger. It is confirmed that the conversion mechanism of heat transfer is carried out that heat conduction is the dominative term at high dimension permeability. The correlations of heat transfer rate and pressure drop for staggered and single row tube bundle wrapped with metal foam are concluded,respectively. The effects of different bonding methods are revealed for point-contact in metal foam and base tube. The powder-sintering method can provide a stable and minimum-thickness bonding layer. Various types of solar thermal facilities utilized metal foam to improve the energy conversion efficiency from solar radiant energy to thermal energy are also reviewed and discussed,including solar collector for intermediate-low temperature utilization and solar receiver for high temperature utilization. The Last but not least,existing and future metal foam thermal application stations are overviewed.

关键词： metal foam heat transfer enhancement solar thermal facilities thermal energy storage

Thermodynamic Analysis of a Hybrid Energy System Coupling Solar Organic Rankine Cycle and Ground Source Heat Pump: Exploring Heat Cascade Utilization

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SSRN 2023年

The demand for efficient utilization of renewable energy is growing and the hybrid energy system driven by solar and geothermal energy is a significant way to minimize carbon emission and achieve carbon neutrality. This paper presents a hybrid energy system coupling solar organic Rankine cycle (S-ORC) with ground source heat pump (GSHP) for heating and power supply to further increase thermal efficiency and explore the heat cascade utilization of hybrid energy system during the heating season. In the hybrid energy system, the ground heat exchanger (GHE) is shared by the S-ORC and GSHP systems and the waste heat from the condenser of S-ORC is recovered to enhance the coefficient of performance (COP) of GSHP. A mathematical model is optimized to analyze the parametric effects on thermodynamic performance under different operating conditions. The comparison between the hybrid energy system and the stand-alone GSHP system is performed to present the superiority of energy recycling. The results indicate that the COP of the hybrid energy system can be improved up to 6.5 which shows the obvious advantage compared to 2.8 of the stand-alone GSHP system under the given system conditions. In addition, the increase of turbine inlet pressure can not only reduce the area of solar fields and length of buried tubes, but also contribute to the thermodynamic performance of the hybrid energy system. Furthermore, the hybrid energy system can obtain optimum exergy efficiency by matching ground source temperature and condensation temperature in the ORC unit. For a building of 3000m2 with heating and power supply, multi-objective optimization by means of a genetic algorithm is carried out to obtain the optimal design performance that the net power output, thermal efficiency and exergy efficiency are 180.0kW, 27.5%, and 9.2% respectively. © 2023, The Authors. All rights reserved.

关键词： Geothermal heat pumps

Aeroderivative Gas Turbine and Composite Sco2 power Cycle Integrated System: Towards Large-Scale Gas-to-power Efficient Conversion

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SSRN 2023年

作者： Jiang, Yuemao Wang, Shunsen Su, Wen Li, Bo Wang, Zhe State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China School of Energy Science and Engineering Central South University Changsha410083 China National Center for International Research of Subsea Engineering Technology and Equipment Dalian Maritime University Dalian116026 China

power-to-Gas is proving to be an effective means of storing electricity from renewables on a large scale. Nevertheless, there is yet to be a clear technical route for large-scale hydrogen-enriched gas conversion into electricity (Gas-to-power). This paper proposed a novel integrated power system consisting of an aeroderivative gas turbine and a composite supercritical CO2 (sCO2) power cycle. In addition, a new evaluation indicator based on exergy was also proposed to reveal the real waste heat recovery capacity and select the sCO2 cycles. After that, a comprehensive energy, exergy, exergoeconomic, and environment (4E) analysis and global parametric studies were conducted for the integrated system. Finally, an entropy-based TOPSIS decision-maker was combined with the tri-objective optimization algorithm for the combined cycle integrated design. Thermodynamic optimization results show that, unlike the thermal efficiency, the exergy efficiency of the partial heating sCO2 cycle of 48.3% is higher than that of the recuperated one. With the exhaust gas carrying 21% of fuel exergy, the total exergy recovery efficiency is 51.7%, and the fuel efficiency of the integrated system is over 50%. As for the exergoeconomic, the combustor alone is responsible for 77.1% of the total exergy destruction, the initial cost of the bottoming cycle is less than half that of the gas turbine, and the high-pressure turbine has the highest exergoeconomic factor of 91.5%. The key parameters of the gas turbine significantly influence the performance of the sCO2 cycle and the integrated system 4E performance. There is an optimal gas turbine inlet temperature of about 1500 K to minimize the LCOE. After the multi-objective integrated optimization, the overall efficiency, LCOE, and specific gas emissions are 50.2%, 7.8 cents/kWh, and 396.8 g/kWh, respectively, which are all higher than those from optimizing the bottoming cycle alone. It is considered that the technical solutions and research results

关键词： Gas turbines

Study on basic coal consumption characteristics in dynamic process of 660MW ultra-supercritical coal-fired unit

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Study on basic coal consumption characteristics in dynamic p...

2019 Canadian Society for Civil engineering Annual Conference, CSCE 2019

作者： Yin, Junjie Liu, Ming Yan, Junjie Zhao, Yongliang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

ISBN: (纸本)9780791883747

With the spreading of intermittent renewable power, coalfired power units should cycle frequently to balance the load between power supply side and demand side. Coal consumption of coal-fired units operating in dynamic processes is influenced by many factors, including thermal system, control system, heat storage variation, etc. Therefore, it is very difficult to evaluate the energy efficiency of coal-fired units operating in dynamic processes. It is important to ascertain the basic coal consumption rate in dynamic processes, which is the basis to evaluate the operation performance of coal-fired units. In this study, an off-design calculation model of 660MW ultra-supercritical coal-fired unit is developed and validated with design parameters. The developed model can be used to predict the coal consumption rates under steady-state off-design conditions. The basic coal consumption means the coal consumption of coal-fired units with operating parameters the same as target values. To calculate the basic coal consumption rate, a load cycling process is differentiated into lots of short time periods and every period is regarded as a steady-state condition with constant load, therefore the coal consumption rates in every period are equal to that of the corresponding steady-state condition. The calculation formula of basic coal consumption rates in is derived for load cycling processes. On the basis of the off-design calculation model and assumption of idealized condition, average coal consumption rates during different processes with constant load cycling rates can be calculated and analyzed. Results show that if the initial and final loads are both settled, the basic coal consumption rate remains unchanged and is independent of load cycling rate. If the load cycling amplitude remains unchanged, the basic coal consumption rate increases as the initial load decrease. The study aims to provide benchmark values for the energy consumption analysis in actual dynamic processes,

关键词： Energy efficiency

Modeling Study on Anisotropic Transport Properties of Pemfc Gdls Facilitated by Xct

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SSRN 2025年

作者： Liu, Hang Li, Yang Huang, Heng Zhou, Zhifu Wu, Wei-Tao Wei, Lei Lyu, Jizu Hu, Chengzhi Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

The gas diffusion layer (GDL) of proton exchange membrane fuel cells (PEMFCs) is a critical component for the transport of reactants. The efficiency of reactant gas transport remains a major technical challenge in the field today. The anisotropic structure of the GDL gives rise to substantial variations of gas diffusion as well as permeability in different directions. The study employs X-CT technology to obtain the actual GDL’s geometry, aiming to investigate a spatial structure at the microscale and its gas transport characteristics. CFD method is used to simulate and study the gas diffusivity and gas permeability of GDL with four different thicknesses. The numerical simulation results show the diffusivity and permeability in the Through-plane (TP) direction are lower than those in the In-plane (IP) direction. Moreover, the effective diffusion coefficient decreases with increasing thickness, but is also dependent on the solid fibre structure of GDL. Horizontal alignment of the carbon fibers and the disc-shaped adhesive contributes to the anisotropy between the TP and IP directions, resulting in anisotropic gas transport. The purpose of the study is to supply critical references for manufacturing techniques and optimization of gas transport in GDLs. © 2025, The Authors. All rights reserved.

关键词： Gas permeability

Numerical study on the mechanism of drag modulation by dispersed drops in two-phase Taylor-Couette turbulence

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arXiv

arXiv 2023年

作者： Su, Jinghong Yi, Lei Zhao, Bidan Wang, Cheng Xu, Fan Wang, Junwu Sun, Chao New Cornerstone Science Laboratory Center for Combustion Energy Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Energy and Power Engineering Tsinghua University Beijing100084 China State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences P. O. Box 353 Beijing100190 China Department of Engineering Mechanics School of Aerospace Engineering Tsinghua University Beijing100084 China

The presence of a dispersed phase can significantly modulate the drag in turbulent systems. We derived a conserved quantity that characterizes the radial transport of azimuthal momentum in the fluid-fluid two-phase Taylor-Couette turbulence. This quantity consists of contributions from advection, diffusion, and two-phase interface, which are closely related to density, viscosity, and interfacial tension, respectively. We found from interface-resolved direct numerical simulations that the presence of the two-phase interface consistently produces a positive contribution to the momentum transport and leads to drag enhancement, while decreasing the density and viscosity ratios of the dispersed phase to the continuous phase reduces the contribution of local advection and diffusion terms to the momentum transport, respectively, resulting in drag reduction. Therefore, we concluded that the decreased density ratio and the decreased viscosity ratio work together to compete with the presence of two-phase interface for achieving drag modulation in fluid-fluid two-phase turbulence. Copyright © 2023, The Authors. All rights reserved.

关键词： Drag

Laser-Synthesized Ligand-Free Cu Nanocatalysts in Electrochemical CO2 Reduction to Methane

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arXiv

arXiv 2025年

作者： Ye, Taiping Lactionov, Artyom Sozaev, Islam Popov, Anton Klimentov, Sergei Kabashin, Andrei V. Liu, Ya International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi 710049 China National Research Nuclear University MEPhI Moscow115409 Russia CNRS LP3 Aix-Marseille Université Marseille13288 France

Electrochemical CO2 reduction (eCO2R) represents a pivotal strategy for mitigating global carbon emissions while simultaneously converting renewable energy into storable chemical fuels. Copper-based catalysts have been extensively explored in this field due to their unique capability to catalyze multi-carbon products. However, the intrinsic complexity of eCO2R pathways on Cu surfaces often leads to mixed product distributions, posing a significant challenge for achieving high selectivity toward a single desired hydrocarbon. Herein, we report a breakthrough in methane selectivity using laser-synthesized, ligand-free Cu nanomaterials. Unlike conventional Cu catalysts that produce diverse products, these ligand-free nanoparticles exhibit unprecedented selectivity for methane (CH4) with a Faradaic efficiency (FE) exceeding 70% at superior overpotentials. The absence of surface ligands, a direct consequence of the ultrafast laser ablation synthesis, ensures abundant exposed active sites with tailored electronic and geometric configurations. We attribute the exceptional methane selectivity to the synergistic effects of active sites-rich surfaces and optimized *CO intermediate binding energetics, which favor the protonation pathway toward CH4 rather than C–C coupling. This work not only resolves the longstanding selectivity dilemma in Cu-catalyzed eCO2R but also establishes laser-synthesized ligand-free nanomaterials as a versatile platform for designing high-performance electrocatalysts. Copyright © 2025, The Authors. All rights reserved.

关键词： Nanoparticles