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An Investigation on Characteristics of Severe Slugging in an Offshore S-Shaped Riser with a Long Pipeline

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SSRN 2023年

作者： Yu, Haiyang Xu, Qiang Huang, Bo Cao, Yeqi Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi 'an Jiaotong University Xi’an710049 China

Long pipelines and risers are essential for transporting oil and gas from the seabed to offshore processing facilities. However, most research focuses on riser systems with short pipelines (≤ 400 m). A 29.1 m high S-shaped riser connecting a 1657 m horizontal pipe, which is comparable to the scale of industrial fields, is utilized for investigating the characteristics of severe slugging. Based on the visual data of gas-liquid interface evolution and the fluctuation of the riser's pressure, the flow pattern map is drawn. Long pipelines delay the liquid accumulation and prolong the severe slugging period. A new correlation for predicting the slugging period is proposed with a deviation of ±15%. The long pipeline provides sufficient compression space and aggravates the blowouts of liquid slugs. The maximum blowout velocity reaches 23 times the mixing velocity. The gas accumulated in the pipeline expands sharply, which causes the instability of the gas-liquid interface in the horizontal pipe and induces a large number of liquid slugs to flow into the riser, where the continuity blowdown of slugs appears. A slug-tracking model considering pressure and liquid holdup is established to precisely forecast the fluctuation of riser pressure during the slug continuity blowdown. © 2023, The Authors. All rights reserved.

关键词： flow patterns

Enhancement of Scr Denitrification Control Strategy Considering Fluegas Temperature Fluctuation: Fundamental Principle and Performance Evaluation

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SSRN 2023年

作者： Gao, Wei Yin, Junjie Liu, Ming Zhao, Yongliang Wang, Chaoyang Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Nitrogen oxides (NOx) is one of the main pollutants in coal-fired power plants, and selective catalytic reduction (SCR) is widely applied to reduce NOx emissions. Coal-fired power plants should frequently change their output power to help the power grid to accommodate high penetration of intermittent renewable power. However, NOx emission transient overshoot often occurs in coal-fired power plants when coal-fired power plants dynamically change their output power. In this study, the dynamic models for a coal-fired power plant and SCR denitrification are developed. The fluegas temperature fluctuation is revealed as a key cause for the NOx emission transient overshoot. The change law of SCR reaction temperature during load cycling processes is obtained, and its prediction model based on neural network algorithm is developed. Then, an enhanced control strategy considering temperature fluctuation of SCR inlet fluegas is proposed, and denitrification performance with the original and enhanced control strategies during load cycling processes are compared. The results show that the transient overshoot of NOx outlet concentration is avoided during load cycling processes, and the maximum value of NOx emissions during loading down and loading up processes with the enhanced control strategy are 48.62 and 49.44 mg m−3, which decreases by 7.36 and 4.63 mg m−3 compared with the original control strategy, respectively. Moreover, when the enhanced control strategy is adopted, the cumulative NH3 consumption decreases by 0.48 and 11.84 g m−3 during loading down and loading up processes, respectively. © 2023, The Authors. All rights reserved.

关键词： Coal fired power plant

Research on Full-Day Operation Strategies of Virtual power Plants Integrating Interruptible Loads Energy Storage to Adapt to Various Weather Changes

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SSRN 2024年

作者： Chong, Daotong Tian, Zeyu Wang, Zhu Du, Guanghan Yan, Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China

Interruptible load energy storage (ILES) represents a novel energy storage technology with the dual functionality of load and storage. The storage aspect of an ILES facilitates flexible and controllable scheduling. In contrast, the load attribute offers widespread energy storage potential. ILES surpasses traditional storage methods, particularly at large scales, by efficiently utilizing existing resources, reducing investment needs, and avoiding energy decay. However, the dual nature of ILES presents challenges in its direct application to power grids, necessitating its integration into virtual power plants (VPPs) as an indirect but crucial scheduling tool. This study develops a dynamic simulation model for a large-scale VPP incorporating an industrial-scale ILES. A control strategy is proposed, focusing on the efficient and flexible use of ILES and ensuring the VPP's safe, stable operation. This strategy includes a method for determining the dispatching time and range of the ILES and introduces three schemes—power universality, power enhancement, and power attenuation—to compute the dispatching power of the ILES and develop a dispatch plan tailored to varying needs. Additionally, the strategy enhances existing control systems by generating optimized signals to increase the dispatch rate and ensure operational safety. Simulation analysis of three typical scenarios assesses the dispatching parameters of the ILES, VPP operation safety, and system capacity for grid ancillary service participation. The findings show that while maintaining safety and stability, the ILES dispatch rate improved from 10 MW/min to 40 MW/min, diminishing energy losses and enhancing efficiency. Adjustments in dispatching times increased the ILES dispatching power from 53.7 MW to 101.8 MW and the VPP output power from 16.9 "MW∙h" to 96.7 "MW∙h", significantly boosting system flexibility and ancillary service capabilities. The variability in dispatching power, under scheme modifications, ranged

关键词： Energy storage

Experimental Investigation of Pressure Pulsation and Noise Due to Thermodynamic Effects on Cavitation in High-Temperature Water

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SSRN 2024年

作者： Xu, Bo Hu, Hongfei Yang, Kuang Wang, Haijun State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

In power systems or equipment, water is often in a state of high temperature and high pressure. The thermodynamic effects are non-negligible during cavitation. The orifice plate, as one of the most fundamental structures in cavitation flow, is used as a research object in cavitation experiment to analyze the thermodynamic effects of high-temperature water. In this study, the variational mode decomposition is improved by using the center frequency and correlation coefficient of the intrinsic mode functions, thus developing an adaptive variational mode decomposition method (AVMD). This method effectively decomposes the pressure pulsations and radiated noise during cavitation and can reasonably classify different cavitation stages. The results indicate that periodic turbulence pulsation frequencies of 5-15 Hz are observed in non-cavitating regions. With the onset of cavitation, the flow field exhibits high-frequency pseudo-periodic frequencies, and the turbulence pulsation frequency gradually decreases, with Strouhal number (St) reducing from 0.2 to 0.1. In regions of severe cavitation, the St of turbulence pulsation frequency exceeds 0.4. Under the same cavitation number, during the development stage of cavitation, as the degree of subcooling decreases, the temperature drop in the cavitation region gradually increases, and the maximum is 2.5 K. The amplitude of pressure pulsations also declines, with the maximum reduction reaching 49.7%. In the severe cavitation stage, the temperature drop in the cavitation region reaches a maximum of 2.87K and is no longer affected by the degree of subcooling. The radiated noise sound pressure level exhibited similar trends as the pressure pulsations inside the pipe when the cavitation number changed. The noise was dominated by low frequencies, with a sound pressure level around 82dBA. The mid-frequency component had a sound pressure level around 79dBA, while the high-frequency component corresponded to a level around 77dBA. At the s

关键词： Variational mode decomposition

Robust DNA-Bridged Memristor for Textile Chips

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Angewandte Chemie 2020年第31期132卷 12862-12868页

作者： Xu X. Zhou X. Wang T. Shi X. Liu Y. Zuo Y. Xu L. Wang M. Hu X. Yang X. Chen J. Chen L. Chen P. Peng H. State Key Laboratory of Molecular Engineering of Polymers Department of Macromolecular Science and Laboratory of Advanced Materials Fudan University Shanghai 200438 China State Key Laboratory of ASIC and System School of Microelectronics Fudan University Shanghai 200433 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao Tong University Shannxi 710049 China State Key Laboratory of Surface Physics Fudan University Shanghai 200438 China Department of Materials Science Fudan University Shanghai 200438 China

Electronic textiles may revolutionize many fields, such as communication, health care and artificial intelligence. To date, unfortunately, computing with them is not yet possible. Memristors are compatible with the interwoven structure and manufacturing process in textiles because of its two-terminal crossbar configuration. However, it remains a challenge to realize textile memristors owing to the difficulties in designing advanced memristive materials and achieving high-quality active layers on fiber electrodes. Herein we report a robust textile memristor based on an electrophoretic-deposited active layer of deoxyribonucleic acid (DNA) on fiber electrodes. The unique architecture and orientation of DNA molecules with the incorporation of Ag nanoparticles offer the best-in-class performances, e.g., both ultra-low operation voltage of 0.3 V and power consumption of 100 pW and high switching speed of 20 ns. Fundamental logic calculations such as implication and NAND are demonstrated as functions of textile chips, and it has been thus integrated with power-supplying and light emitting modules to demonstrate an all-fabric information processing system. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

关键词： DNA fiber electronics logic-in-memory computing memristors nanoparticles

Exergy-Based Control Strategy Design and Dynamic Performance Enhancement for Parabolic Trough Solar Receiver-Reactor of Methanol Decomposition Reaction

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SSRN 2023年

作者： Zhang, Peiye Liu, Ming Mu, Ruiqi Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The parabolic trough solar receiver-reactors of methanol decomposition reaction (PTSRR-MDR) enable efficient hydrogen production with solar energy at users' end. Solar fluctuations affect the solar-to-chemical efficiency, hydrogen yield and system stability, indicating the necessity for an appropriate control strategy. In this study, dynamic and thermodynamic models of PTSRR-MDR with Cu/ZnO/Al2O3 as catalyst were developed. Results of thermodynamic analysis show that an optimal flow rate exists for methanol to achieve the maximum solar-to-chemical exergy efficiency of the PTSRR-MDR. The temperature increases sharply and exceeds the catalyst sintering temperature when the methanol flow rate decreases under its optimal value. Then, control objectives to achieve the maximum efficiency were obtained with a temperature of 3 °C to guarantee the PTSRR-MDR safety. Control strategies based on Dynamic Matrix Control (DMC), Forward-Feedback Control (FFC) and Ramp Control (RC) were evaluated under cloud shading/recovering and real radiation processes. Results show that strategies based on DMC, FFC, and RC increase the solar-to-chemical exergy efficiency from 14.76% to 16.31%, 16.28% and 15.65%, respectively. The Integral Squared Error (ISE) for methanol conversion rate under three methods are 1.46, 0.32 and 5.28, respectively, indicating that strategy based on FFC is considered most suitable for PTSRR-MDR operation control. © 2023, The Authors. All rights reserved.

关键词： Methanol

Deposition of Cement Kiln Ash on the Tubes of Waste Heat Recovery Boiler

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Deposition of Cement Kiln Ash on the Tubes of Waste Heat Rec...

IEEE PES Asia-Pacific power and Energy engineering Conference (APPEEC)

作者： Yufeng Wang Chunyun Hu Shi'en Hui Qinxin Zhao Qulan Zhou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

Deposition of cement kiln ash on the tubes of heat recovery boiler affects the heat exchange efficiency. The basic characteristic of cement kiln ash and the deposition on the tubes with different arrangements are presented. Numerical simulation and experiment measurement show that flow field feature, especially the low-velocity zone and vortex street, causes different shape of ash deposit around the tube. The effect of ash concentration, tube arrangement and gas velocity on the deposition is analyzed. The effect of the tube diameter and the gas composition is also discussed.

关键词： Ash Electron tubes Surface treatment Heat recovery Waste heat Shape Boilers

Experimental Investigation on Heat Transfer of Supercritical Water flowing in a Horizontal Tube with Axially Non-Uniform Heating

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SSRN 2023年

作者： Hou, Zhenghui Huang, Xin Gao, Yu Zhang, Shengjie Wang, Haijun State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

For a heat exchanger, the heat flux is usually non-uniform in the axial direction, and the knowledge about heat transfer of supercritical water with axially non-uniform heating is scarce. To fill the gap, experiments were conducted in a horizontal tube to study the heat transfer characteristics of supercritical water with axially sinusoidal heating. The pressures varied from 23.5 to 26.5 MPa, mass fluxes 200 to 400 kg·m-2·s-1 and average heat fluxes 50 to 150 kW·m-2. Compared with uniform heat flux, the temperature difference between the top and bottom wall is larger than that of the axially sinusoidal heat flux. The inner-wall heat flux is non-uniform along the circumference due to the temperature difference, being higher at the side wall and lower at the top wall. A relative heat flux parameter is defined to describe the relative magnitude of the local heat flux. The relative heat flux parameter of the top generatrix, which is inversely proportional to the average heat flux, decreases linearly with the increase of the temperature difference between the top and side generatrix. The non-uniform degree of heat flux along the circumference is positively correlated with the average heat flux. Additionally, the local heat transfer characteristics should be considered in horizontal tubes. On the one hand, the heat transfer deterioration may occur when the fluid temperature near the top wall is higher than the pseudo-critical temperature and it can be suppressed with increasing Reynolds number. On the other hand, the local heat transfer can be enhanced if the side and bottom wall temperatures exceed the pseudo-critical temperature. © 2023, The Authors. All rights reserved.

关键词： Heat flux

New Technology of Thermodynamic Cycle for Waste Heat Recovery of Vehicle Gasoline Engine

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New Technology of Thermodynamic Cycle for Waste Heat Recover...

IEEE PES Asia-Pacific power and Energy engineering Conference (APPEEC)

作者： Xin Xin Zhang Ke Zeng Mao Gang He State Key Laboratory of Multiphase Flow in Power Engineering Xi''an Jiaotong University Xi'an Shaanxi China

In this paper, the exothermic distribution of fuel was studied detailedly through conducting thermal equilibrium experiment when the vehicle gasoline engine was at different working conditions. Considering the characteristic of the exhaust temperature of the vehicle gasoline engine, the Organic Rankine Cycle (ORC) was adopted for the exhaust recovery. The thermodynamic parameter and thermodynamic performance of the main state points in the ORC were theoretically calculated via computer program. The optimal parameter was determined. On this basis, the organic working fluids were selected. In the last part, a new thermodynamic cycle configuration which can be used to recover the heat from exhaust gas, cooling water and lubricant of vehicle gasoline engine was put forward and introduced.

关键词： Thermodynamics Heat engines Heat recovery Waste heat Vehicles Petroleum Fuels Thermal conductivity Employee welfare Temperature