Table of Content

28 January 2023, Volume 57 Issue 1 Previous Issue    Next Issue

New Type Power System and the Integrated Energy

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Management and Optimal Control Algorithm for Electric Vehicle Charging in Random Environment LIU Didi, YANG Yifei, YANG Yuhui, ZOU Yanli, WANG Xiaohua, LI Xin 2023, 57 (1):  1-9.  doi: 10.16183/j.cnki.jsjtu.2021.499 Abstract ( 1061 )   HTML ( 273 )   PDF (1627KB) ( 551 )   Save With the increasing scale of electric vehicles (EVs), the adaptive management of its charging behavior becomes an urgent problem to be solved. From the point of view of charging service provider, an online management algorithm for EV charging is proposed based on the Lyapunov optimization theory under the random environment in this paper, considering renewable sources energy, storage equipment, time-varying electricity price, and the tolerable delay of EV, with an aim of maximizing the benefits of charging service providers (i.e., minimizing the cost of electricity purchased). The performance of the proposed algorithm is analyzed to verify that it can achieve near-optimal optimization results without any a priori statistical information about the system inputs (renewable energy generation, charging demand, and time-varying electricity price). The simulation results show that the proposed algorithm can effectively reduce the economic cost by 27.3% compared with the benchmark algorithm. Figures and Tables | References | Related Articles | Metrics

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Optimal Sizing of Grid-Connected Wind-Solar-Biogas Integrated Energy System Considering Demand Response YU Faqiang, ZHANG Mingjie, CHENG Yu, CHEN Dawei, YANG Hanyu, LI Canbing 2023, 57 (1):  10-16.  doi: 10.16183/j.cnki.jsjtu.2022.017 Abstract ( 559 )   HTML ( 21 )   PDF (1559KB) ( 348 )   Save There are abundant biomass resources in China’s rural areas, which can be converted into biogas energy through fermentation systems. However, the rewards of the investments of the pure biogas projects is poor because biogas is a cheap resource. This paper proposes a 100% renewable grid-connected wind-solar-biogas integrated energy system which utilizes the complementarity between solar energy, wind energy, and biogas to provide users with biogas and electricity. The battery-like characteristics of biogas are modeled based on the microbial fermentation kinetic model and the temperature-sensitive characteristics of biogas fermentation. In addition, the demand-side response is considered to further increase the flexibility of the system, and the time-of-use electricity price is used to save power purchase costs, thereby minimizing investment costs and annual operating costs. Case studies show that the wind-solar-biogas micro-energy network can effectively reduce the total investment cost by 3% to 9% while increasing the benefit by 1.27 to 2.40 times. Figures and Tables | References | Related Articles | Metrics

Naval Architecture, Ocean and Civil Engineering

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Influence of Convection Heat Transfer on Circular Tube Structure of Polar Marine Engineering Equipment CAO Taichun, WU Gang, KONG Xiangyi, YU Dongwei, WU Lin, ZHANG Dayong 2023, 57 (1):  17-23.  doi: 10.16183/j.cnki.jsjtu.2021.205 Abstract ( 502 )   HTML ( 20 )   PDF (1248KB) ( 382 )   Save Electric heat tracing is often used for cold protection in polar ocean engineering equipment. Heat balance is the key problem of convective heat transfer. In this paper, the circular tube structure is taken as the research object. Numerical simulations using Fluent and model experiment are conducted to analyze the change of the convective heat transfer coefficient of the circular tube component under the polar environment with a wind speed range of 0—40 m/s and a temperature range of -40—0 ℃. Based on the numerical simulation data, the prediction model of the convective heat transfer coefficient of the electric heating tube is obtained. The results show that the convective heat transfer coefficient increases with the increase of wind speed and the decrease of temperature. When the temperature is below -30 ℃, or when the wind speed is greater than 25 m/s and the temperature is lower than -20 ℃, the influence of temperature on the convective heat transfer coefficient increases. The rationality of the model is verified by experimental test. Figures and Tables | References | Related Articles | Metrics

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Ship Block State Identification and Transfer Monitoring Based on Time-Site Data of Blocks CHEN Junyu, TIAN Ling 2023, 57 (1):  24-35.  doi: 10.16183/j.cnki.jsjtu.2021.287 Abstract ( 482 )   HTML ( 8 )   PDF (1597KB) ( 336 )   Save Ship block transfer is important to the orderly flow of blocks between crafts, which is costly. Shipyard managers have to monitor the actual transfers, especially the unproductive transfers that occur when blocks are obstructed or reworked. A high-load shipyard, called S, often uses one site for multiple purposes, and the difficulties in obtaining the state of ship blocks through the time-site data of blocks provided by the existing monitoring technology make it difficult to monitor two types of unproductive transfers. To address this problem, four hidden Markov models whose parameters are calculated by a supervised approach are proposed, and a Viterbi algorithm based method is proposed to identify the state of blocks, achieving an accuracy of up to 93.5% on the test dataset. One of the hidden Markov models is applied to the time-site data of blocks to monitor two types of unproductive transfers in shipyards. Preliminary suggestions for improving the blocks transfer process based on monitoring results are proposed. Figures and Tables | References | Related Articles | Metrics

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Sequential Prediction Method of Single Parameter for Thermal System Based on MWSA XIAO Pengfei, NI He, JIN Jiashan 2023, 57 (1):  36-44.  doi: 10.16183/j.cnki.jsjtu.2021.300 Abstract ( 459 )   HTML ( 14 )   PDF (1291KB) ( 316 )   Save The changes in the status parameters of the thermal system reflect the operating status of the system in real time. The forecast results of the trend extraction and time series prediction of the current equipment status parameters can be used as a reference for the next operation management strategy and equipment maintenance, which can be used for the long-term system safe and stable operation. In this paper, a method which is described as MWSA, based on the midpoint and regression based empirical mode decomposition (MREMD), the wavelet threshold denoising (WTD) and midpoint and techniques, the singular value decomposition (SVD) and optimized parameter permutation entropy (PE), and an auto regressive integrated moving average model (ARIMA), is applied to the single-parameter time series prediction of thermal systems. First, the MREMD is used to decompose the monitored operating state parameters into a number of intrinsic mode functions (IMF) and residual components. Next, the components that do not meet the screening conditions are subjected to wavelet thresholding. The denoised components and the components that originally meet the filtering conditions are recomposed into new IMF components. Finally, the K-means clustering algorithm based on SVD and PE is used to classify the recomposed IMF components, the component with a lower entropy value is selected and reconstructed into a trend item, and ARIMA is used to predict. An actual case verifies that this method can effectively overcome the interference of high-frequency noise in the original parameter timing, and the prediction accuracy is higher than that of similar methods without noise reduction treatment. Figures and Tables | References | Related Articles | Metrics

Mechanical Engineering

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Flow Boiling Heat Transfer Coefficient and Frictional Pressure Drop Correlations for R32 GU Bo, DU Zhongxing, ZENG Weijie, TIAN Zhen, ZHANG Zhiting 2023, 57 (1):  45-54.  doi: 10.16183/j.cnki.jsjtu.2021.239 Abstract ( 717 )   HTML ( 26 )   PDF (2322KB) ( 404 )   Save The objective of this study is to establish generalized correlations for R32 flow boiling heat transfer and frictional pressure drop in channels with wide ranges of geometric and flow parameters. In this paper, two consolidated databases for heat transfer and frictional pressure drop were amassed from open literature, which involved R32 as working fluid. The heat transfer database consisted of 1 489 data points from 8 sources, with hydraulic diameters of 1—6.3 mm, while the pressure drop database included 496 data points from 8 sources, which covered hydraulic diameters of 0.643—6 mm. A new heat transfer coefficient correlation and a frictional pressure drop correlation were developed based on the prediction technique of dimensionless parameter analysis considering the governing force effect. Moreover, the existing correlations were also introduced to perform assessment. The validation results show that the existing correlations have poor results of mean absolute errors (MAE) and significantly high maximum absolute errors (MAX), but the new heat transfer coefficient correlation provides a superior prediction accuracy with a MAE of 14.59% and 90.85% of data within ±30% error bands. In addition, the new pressure drop correlation exhibits the best performance, which yields a MAE of 17.86%. The two new correlations have a broad application range and satisfactory prediction accuracy, which are applicable to analyze the heat transfer and pressure drop performance of heat exchangers with refrigerant R32. Figures and Tables | References | Related Articles | Metrics

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Numerical Simulation Study on Effect of Fin Array on Impingement Heat Transfer Performance of Airfoil Surface ZHANG Tianlun, WANG Kechen, ZHANG Xu, ZHOU Wenwu 2023, 57 (1):  55-65.  doi: 10.16183/j.cnki.jsjtu.2021.222 Abstract ( 462 )   HTML ( 15 )   PDF (27478KB) ( 305 )   Save Impinging jet is widely implemented at the leading edge of aircraft wings for anti-/de-icing purposes. To further improve the anti-icing performance, this paper utilized numerical simulation to explore the impingement heat transfer characteristics of different fin arrays on flat plate and concave surface sequentially. The fin array in the flat-plate model consisted of 8, 12 straight fins or 12 curved fins. The concave surface model consisted of 8 short or long fins. The results show that the addition of fin arrays on the flat plate and airfoil surface can significantly improve the jet impact heat transfer performance at different Reynolds numbers. Compared with non-fins, the comprehensive heat transfer effect on the airfoil surface is increased by 4%—10%, especially for the stagnation region. Further flow field analysis reveals that adding fin array not only increases the area of heat transfer, but also strengthens the turbulent kinetic energy of impingement jet flow, leading to an enhancement of heat transfer performance. Figures and Tables | References | Related Articles | Metrics

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Simulation and Analysis of Contactless Solar Evaporation YU Jie, XU Zhenyuan 2023, 57 (1):  66-75.  doi: 10.16183/j.cnki.jsjtu.2021.255 Abstract ( 512 )   HTML ( 16 )   PDF (4616KB) ( 375 )   Save Zero-liquid discharge is an efficient pathway for high concentration brine and wastewater treatment. Contactless solar evaporation is a new configuration proposed in recent years towards this target, which has the advantages of solar energy utilization, simple structure, passive operation, and anti-fouling. Considering that contactless solar evaporation lacks an effective predictive model to guide the optimization in real scenarios, a steady-state thermal resistance network model is developed for the first time and further analyses are conducted. According to the results, two main heat sources of the water, radiative heat transfer and air gap heat transfer, contribute 54.2% and 45.8% to the total heat flow and both have a significant impact on the evaporation performance. The larger air gap thickness has a negative effect on both of the two heat transfer processes. The evaporation rate with an air gap thickness of 10 mm is only 70% of that with an air gap thickness of 4 mm. Additionally, decreasing vapor diffusion resistance is an efficient way to increase the evaporation rate. The evaporation rate triples when the vapor diffusion coefficient increases from 5×10-6 m2/s to 2.5×10-5 m2/s. Figures and Tables | References | Related Articles | Metrics

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Measurement of Cryogenic Thermal Contact Resistance of Brass by Lamination Method SHEN Yi, CAO Jiaxing, HUANG Yonghua 2023, 57 (1):  76-83.  doi: 10.16183/j.cnki.jsjtu.2021.394 Abstract ( 646 )   HTML ( 12 )   PDF (8861KB) ( 345 )   Save Prior studies on cryogenic thermal contact resistance (TCR) measurement mainly focus on liquid nitrogen temperature region and above. There are limited solid TCR data in the lower temperature region. The present measurement is based on an RDK-408D2 two-stage G-M cryogenic refrigerator. By using the laminated method, the TCR data of brass samples in the temperature range of 10—30 K at different roughnesses and preloads are measured and the influence of different factors on TCR is discussed. The results show that the TCR of the brass contact surface in this temperature zone is between 6.89×10-4 and 1.86×10-2 m2·W/K. With a smaller roughness of the contact surface, higher temperature, and greater pre-tightening force, the TCR becomes smaller. This behavior is consistent with the conventional qualitative understanding. The above cryogenic experimental data can provide certain support for the calculation of TCR for related cryogenic application design. Figures and Tables | References | Related Articles | Metrics

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Atomization Characteristics Analysis and Structure Optimization of an Aviation Fuel Nozzle BAI Qingsong, WU Yang, HOU Li 2023, 57 (1):  84-92.  doi: 10.16183/j.cnki.jsjtu.2021.256 Abstract ( 907 )   HTML ( 19 )   PDF (9690KB) ( 648 )   Save Fuel atomization plays an important role in premixed combustion of aero-engine. In order to improve the atomization characteristics of an aviation fuel nozzle and optimize its structural parameters, the volume of fluid (VOF) interface capture algorithm and orthogonal experimental design were used to study the influence of internal flow and structural parameters (expansion angle, length of straight section, rise angle of swirl groove, and number of swirl groove) on the atomization characteristics. The results show that the local vortex on the swirl groove affects the fuel flow in the nozzle, and the local pressure loss can be eliminated by changing the structure of the swirl groove inlet. The number of swirl grooves has the most significant effect on Sauter mean diameter (SMD), the expansion angle is the biggest factor affecting the atomization cone angle, there is an optimal swirl groove elevation angle to minimize the oil film thickness, and the length of straight section has relatively little effect on the atomization characteristics. When the expansion angle is 60°, the length of straight section is 0.25 mm, the rising angle of swirl groove is 45°, the number of swirl grooves is 2, and the optimization effect is the best. After optimization, the oil film thickness decreases by 43.68%, the atomization cone angle increases by 3.70%, and the SMD decreases by 14.79%. Figures and Tables | References | Related Articles | Metrics

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Task Assignment and Path Planning for Automatic Guided Vehicles in Aircraft Assembly Workshop QIU Kejun, BAO Zhongkai, CHEN Lu 2023, 57 (1):  93-102.  doi: 10.16183/j.cnki.jsjtu.2021.223 Abstract ( 514 )   HTML ( 23 )   PDF (2561KB) ( 373 )   Save To realize efficient scheduling of automatic guided vehicles (AGV) in the aircraft final assembly workshop, a two-stage method of AGV task allocation and path planning is proposed which effectively solves the problem of multi-trip distribution scheduling of AGV in the workshop. In the task allocation stage, an AGV task allocation model based on the trip is established to improve task allocation efficiency. In the path planning stage, the time window algorithm is used to initialize, update, and arrange the time window of the resources occupied by the AGV. Considering that the latest delivery time constraints may be violated due to obstacle avoidance and waiting, three adjustment strategies are designed to realize the conflict-free path planning of AGV, including the package exchanging strategy, the priority exchanging strategy, and the reserved conflict duration relaxation strategy. In numerical experiments, the average solving time of the two-stage method applied to problems with the scale of 50, 100, and 150 is 15.86, 41.12, and 162.29 s, which indicates that the two-stage method effectively alleviates the complexity of the multi-trip AGV scheduling problem. The two-stage method can realize the scheduling of the AGV in aircraft assembly workshop within a reasonable time and adapt to the rapid increase in the annual production of aircraft. Figures and Tables | References | Related Articles | Metrics

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Formation Control Strategy of Multiple Mobile Robots Cooperative Operation Based on Backstepping Method LIU Yuming, ZHAO Yong, DONG Zhengjian, WANG Ping, JI Yuqi 2023, 57 (1):  103-115.  doi: 10.16183/j.cnki.jsjtu.2021.325 Abstract ( 508 )   HTML ( 14 )   PDF (9418KB) ( 319 )   Save A multi-shift tooling coordinated operation control strategy based on the backstepping method is investigated, a desired motion state planning scheme based on the improved artificial potential field method and the pure trajectory tracking method is proposed, and the actual situation is determined according to the adaptive Monte Carlo positioning method. For the estimated value of the motion state, a queue controller in combination the anti-stepping method and the virtual pilot following method is designed. A simulation model based on the robot operation system (ROS) environment is constructed, and the simulation is verified. The results show that the proposed formation error calculation method can improve the accuracy of error estimation. The formation control strategy can make the formation error converge within 6.2 s, and the designed formation controller can meet the operation requirements of multi-shift tooling. Figures and Tables | References | Related Articles | Metrics

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Application of Adaptive Fuzzy Nonlinear Control with Variable Universe in Liquid Level Control of Steam Generator QIAN Hong, ZOU Mingyao 2023, 57 (1):  116-126.  doi: 10.16183/j.cnki.jsjtu.2021.235 Abstract ( 392 )   HTML ( 9 )   PDF (1935KB) ( 259 )   Save Aimed at the important position of the steam generator liquid level control system in maintaining the safe and efficient operation of the power plant in the PWR nuclear power plant, and the fact that there exist strong nonlinear characteristics in the controlled object of the steam generator liquid level under different load sections and changing conditions, this paper proposes a fuzzy control algorithm with the adaptive variable universe function. Based on the general fuzzy control algorithm, the Lyapunov function is constructed through the nonlinear system model, and the optimal adaptive expansion factor is solved based on the ideal control law, and Lyapunov theorem is used to prove the stability of the control system. The simulation results show that the fuzzy control with adaptive variable universe function can better effectively control the liquid level of the steam generator under different working conditions and variable working conditions than the traditional proportional integral (PI) control and fuzzy PI control. The problem of controller overrun is solved, and the system has a better robustness. Figures and Tables | References | Related Articles | Metrics