Loading...

Table of Content

    28 July 2020, Volume 54 Issue 7 Previous Issue    Next Issue
    Performance Test of an Adsorption Cooling and Heating Cogeneration System Driven by Solar Thermal Energy
    PENG Jiajie, PAN Quanwen, GE Tianshu, WANG Ruzhu
    2020, 54 (7):  661-667.  doi: 10.16183/j.cnki.jsjtu.2019.019
    Abstract ( 868 )   PDF (1839KB) ( 427 )   Save
    The adsorption cooling and heating cogeneration system driven by solar thermal energy can produce cold air and domestic water with a suitable temperature. It does not require a cooling water circuit and a cooling water pump but can meet the needs of miniaturized applications. In order to explore the operation performance and influencing factors of the system, an experimental study was conducted on a silica gel-water adsorption air cooler with two adsorption beds, a condenser and a gravity heat pipe evaporator. The dynamic operating characteristics of the cooler were obtained. The results show that the cooler can effectively utilize the solar hot water in the range of 62℃ to 85℃; the cooling capacity ranges from 0.95kW to 2.76kW; the system refrigeration coefficient of performance ranges from 0.24 to 0.46, and comprehensive coefficient of performance ranges from 1.48 to 2.40; and the optimal cycle time for a single cycle of the cooler is 750s. When the average inlet temperatures of hot water, cooling water, and cold air are respectively 85.1℃, 29.9℃, and 29.5℃, the average outlet temperatures of cold air and cooling water are respectively 22.4℃ and 40.1℃. The experimental results provide reliable information for the efficient use of solar energy to achieve cooling and heating cogeneration.
    References | Related Articles | Metrics
    Adaptability of Multi-Structure of Finned Tube Heat Exchanger Under Variable Operation Conditions Based on Back Propagation Neural Network
    LI Qianglin, ZENG Weijie, TIAN Zhen, GU Bo
    2020, 54 (7):  668-673.  doi: 10.16183/j.cnki.jsjtu.2019.147
    Abstract ( 843 )   PDF (1690KB) ( 332 )   Save
    Based on the experimental data of variable structure heat exchangers, the feasibility of neural network model in the performance for the prediction of water-air finned tube heat exchangers is studied. The back propagation (BP) neural network models of 2 rows and 3 rows of finned tubes under refrigeration and heating conditions are established which optimize and determine the optimal network structure under the condition of single hidden layer and double hidden layer. The prediction error of the models is about 1%. The specified structural heat exchanger data is set as a test set, and the performance of the single hidden layer and double hidden layer network model is compared. The research results show that for the refrigeration condition, the double hidden layer model cannot improve the accuracy of the model, but will even reduce the prediction accuracy of some parameters due to over-fitting. For the heating condition, the double hidden layer model has a better accuracy in prediction.
    References | Related Articles | Metrics
    Eddy Current Distance Measurement Calibration Method for Curved Surface Parts Based on Support Vector Machine Regression
    TAO Zhengrui, DANG Jiaqiang, XU Jinyang, AN Qinglong, CHEN Ming, WANG Li, REN Fei
    2020, 54 (7):  674-681.  doi: 10.16183/j.cnki.jsjtu.2020.99.010
    Abstract ( 813 )   PDF (3728KB) ( 283 )   Save
    Based on the accuracy requirements for the thickness of the polyurethane form layer on the outer surface of the fuel tank, the calibration testing of four common curvature section specimens is conducted. Besides, the eddy current ranging calibration method based on support vector machine regression analysis is proposed to establish the lifting distance prediction model (LDPM), which is used for curved surface eddy current distance measurement. The influence of curvature on the measurement errors of eddy current ranging is studied. The measurement errors are divided into the surface curvature errors and other errors according to the cause of the error. In the different ranges of the sensor range, the relative variation of the error components is analyzed, which provides a basis for surface measurement error compensation. In addition, the comparative analysis of LDPM and the calibration function obtained by using common calibration methods in terms of measurement accuracy and calculation rate are performed, which provides suggestions for the selection of the calibration method for eddy current ranging of curved parts. The results show that the surface curvature error is not sensitive to the curvature in the initial stage of the sensor range. Near the midpoint of the range, the absolute value of the surface curvature error decreases first and then increases with the increase of curvature. In the terminal region, the absolute value of the surface curvature error increases with the rise of curvature, while other errors remain constant within different measurement ranges over the entire range. Moreover, the LDPM can control the measurement error within [-0.5, 0.5]mm, and the accuracy is comparable to five multi-peak Gaussian fitting, higher than the fourth-order polynomial fitting, which can meet the thickness measurement accuracy requirements and is convenient for non-destructive testing.
    References | Related Articles | Metrics
    Impact of Welding Parameters on Arc Characteristics in Triple-Wire Welding
    MA Xiaoli, XU Chen, WANG Weicheng, HUA Xueming
    2020, 54 (7):  682-687.  doi: 10.16183/j.cnki.jsjtu.2019.028
    Abstract ( 787 )   PDF (3850KB) ( 270 )   Save
    Characteristics and arc stability of multi-arc morphology in multi-wire welding are significantly different from those of single-wire welding due to electromagnetic force. A triple-wire welding platform was established, and the influence of welding current and wire-to-wire distance on arc shape characteristics was quantitatively studied by using the triple-wire welding high-speed photographic system. The fluctuation values of arc shape parameters (arc height, arc area, and arc deflection) were used to evaluate arc stability. The results show that there is no obvious fluctuation in arc height, and its value is related to welding current, but independent of wire-to-wire distance. When the welding current is set at a high level, there are more molten pool metals, which cause the “submerged arc phenomenon”, and the height and area of the arc become smaller than those at a low level of welding current. In addition, the arc under the high current condition has a strong anti-interference ability. Therefore, the arc deflection is small, and the arc combustion is stable. The change of wire-to-wire distance has a more direct effect on the middle arc area than that of leading arc and trailing arc. Overall, the interference effect and deflection of arc decrease and the arc stability improves as the wire-to-wire distance increases.
    References | Related Articles | Metrics
    Numerical Simulation of Circumferential Non-Uniform Heat Transfer of Single-Phase Flow in Helical Pipes
    WANG Rui, XIAO Yao, GU Hanyang, YE Yanan
    2020, 54 (7):  688-696.  doi: 10.16183/j.cnki.jsjtu.2019.077
    Abstract ( 809 )   PDF (4281KB) ( 467 )   Save
    In this paper, the Reynolds stress model is used to simulate the circumferential non-uniform heat transfer of single-phase flow in a helical pipe. The calculation is verified based on the comparison with the experimental data. It is found that the ratio of gravity acceleration to centrifugal force acceleration (?) affects the circumferential heat transfer distribution of helical pipes. The reason for this is that the changes of ? lead to the changes of the direction of resultant force of gravity and centrifugal force. It is concluded that the main factor affecting the circumferential heat transfer distribution is ?. Besides, the changing rules and the effects of geometry parameters of helical pipes, such as the ratio of gravity acceleration to centrifugal force acceleration, pitch circle diameter, pipe hydraulic diameter, and spirally ascend angle, on the circumferential heat transfer distribution are discussed.
    References | Related Articles | Metrics
    Bias Attack and Detection Method for Networked Inverted Pendulum System
    XU Binbin, HONG Zhen, ZHAO Lei, YU Li
    2020, 54 (7):  697-704.  doi: 10.16183/j.cnki.jsjtu.2020.174
    Abstract ( 697 )   PDF (2183KB) ( 305 )   Save
    In order to solve the data integrity attack of networked control systems, a bias attack and its detection method based on the networked inverted pendulum platform sensors are designed in this paper. First, the Ettercap tool is utilized to realize network intrusion and inject false data. Next, combined with the support vector machine (SVM) method, the LibSVM classifier is used to train the four kinds of state information in the inverted pendulum system to obtain the model and classify the data. After that, the SVM method is compared with K-nearest neighbor and decision tree methods in the self-built system. Finally, the method proposed is validated on the platform. The simulation and experimental results show that the designed attack method can change the stability of the system. Compared with the commonly used machine learning method, the SVM has more advantages in the binary classification of bias attack detection and can effectively distinguish the false data in the transmission data.
    References | Related Articles | Metrics
    Model of Technology Opportunity Mining Using Machine Learning Algorithm and Its Application
    BAO Qinglin, CHAI Huaqi, ZHAO Songzheng, WANG Jilin
    2020, 54 (7):  705-717.  doi: 10.16183/j.cnki.jsjtu.2020.99.007
    Abstract ( 891 )   PDF (1789KB) ( 258 )   Save
    The applicability of the existing technology opportunity mining results is relatively low owing to the small sample size and the lack of evaluation on the technology application prospects in the mining process. In order to solve this problem, with the goal of improving the applicability of mining results, based on the existing research, this paper proposes a three-dimensional patent prediction model by taking into account a large number of patents and adding an assessment of the prospects for technology applications. Using the PLSA algorithm in machine learning and combining with the MapReduce computing framework under Hadoop, it uses patent text mining to construct the technology and function dimensions of the patent prediction model, adopts entropy weight and TOPSIS method to construct the value dimension of the patent prediction model, and fills the element items in the patent forecasting model based on the MapReduce computing framework. Then, it applies a patent prediction model to 133508 patent texts in the titanium field in the DII database from 1999 to 2018. The results show that the model has identified a total of 3 priority and 2 secondary technology opportunities in the titanium field, and these technology opportunities can be developed in order of priority. This model enriches the method for technology opportunity mining and provides a more accurate and prospective technology research and development direction for innovation subjects.
    References | Related Articles | Metrics
    Ship Block Transportation Scheduling Considering Cooperative Transportation of Flatcars
    LI Baihe, JIANG Zuhua, TAO Ningrong, MENG Lingtong, ZHENG Hong
    2020, 54 (7):  718-727.  doi: 10.16183/j.cnki.jsjtu.2018.339
    Abstract ( 839 )   PDF (1443KB) ( 280 )   Save
    This paper aims at solving the problem of ineffective dispatching status for flatcars in shipyard transportation tasks using the task time window and the loading constraints of various types of flatcars and blocks as constraints. Considering the fact that the weight of a single large block exceeds the maximum loading capacity of a flatcar during actual transportation, this paper proposes a method of cooperative transportation using multiple flatcars. Aimed at establishing an optimization model, the optimal objects set the no-load travel time and waiting time for the task as the weight of the flatcars. Then, a tabu search algorithm is designed to solve the model proposed. Taking the actual data of a shipyard as an example, the application of the model is verified by specific examples. The results show that the method proposed provides a better scheduling scheme which can solve the transportation problem of large blocks and better realize the efficient utilization of resources.
    References | Related Articles | Metrics
    Numerical Simulation of a Rising Bubble in Variable-Density Fluids
    LI Qian, LOU Yingzhong, HE Zhiguo
    2020, 54 (7):  728-735.  doi: 10.16183/j.cnki.jsjtu.2019.211
    Abstract ( 915 )   PDF (2555KB) ( 197 )   Save
    In this paper, a direct numerical simulation model coupled with gas and two layers of liquid with different densities is developed to study the dynamics of rising bubbles in a two-layer stratified environment. Based on the level set method with 5th-order weighted essentially non-oscillatory (WENO) and 3rd-order Runge-Kutta scheme, a numerical method coupling multiple level set functions is proposed to capture both the gas-liquid interface and each liquid surface, as well as calculating both the density and viscosity on the interface. The method proposed is verified by comparing with the available numerical simulation results. Besides, this model is employed to study the motion of a rising bubble in a two-layer fluid involving water and oil, which provides detailed flow structures in a complex environment. The results suggest that compared with the movement in a uniform environment, the water column induced by pressure difference is easier to break at the bottom when a bubble rises against a two-layer stratified background. The increase of liquid thickness above the bubble can extend the time that the bubble stays in the underwater deformation stage, and can lead to a flatter bottom of the bubble.
    References | Related Articles | Metrics
    Foundation Selection and Seismic Performance of Steam Turbine
    WANG Wei, LU Sikui, YANG Chengzhong, XU Sihua, CHEN Jinjian
    2020, 54 (7):  736-744.  doi: 10.16183/j.cnki.jsjtu.2018.302
    Abstract ( 921 )   PDF (4373KB) ( 299 )   Save
    To determine the foundation form and seismic performance of a nuclear steam turbine, this paper established a three-dimensional finite element model of integral structure of the turbine by using LS-DYNA finite element program and comprehensively analyzed the foundation selection problem and the overall seismic resistance of the turbine. The results show that in the rigid foundation and spring foundation of current nuclear power equipment, the spring foundation is more suitable to be used as the foundation of the nuclear steam turbine for its better seismic performance. When the spring foundation is chosen as the foundation of the nuclear steam turbine, the entire structure can meet the seismic requirements at frequently occurred earthquake of 8 degree seismic precautionary intensity. However, at rarely occurred earthquake of 8 degree seismic precautionary intensity, the seismic performance of the structure should be improved because the deformation of some structures of the steam turbine is too large and the internal force does not meet the requirements of its own strength and seismic requirements.
    References | Related Articles | Metrics
    Experimental and Numerical Study of Compressor Tip Leakage Flow Based on Arc-Curve Skewed Slot Casing Treatment
    WU Yadong, LI Tao, ZHANG Yongjie
    2020, 54 (7):  745-755.  doi: 10.16183/j.cnki.jsjtu.2019.040
    Abstract ( 800 )   PDF (6090KB) ( 235 )   Save
    To explore the influence of casing treatment on compressor overall performance, flow unsteadiness, and rotating instability (RI) at blade tip region, arc-curve skewed slot casing treatment is applied to the passive control of the tip clearance flow of a single-stage low-speed axial compressor. The spectrum analysis of blade tip fluctuating pressure under different operating conditions is conducted, and the changes of performance and flow field characteristics at rotor tip region before and after casing treatment are compared. The results show that arc-curve skewed slot casing treatment could increase stall margin by 6.8%, suppress the broadband hump in the frequency spectrum caused by RI, delay the starting position of the leakage vortex, and eliminate the circumferential flow propagation across adjacent blades. The backflow formed in the skewed slot can suck low-velocity fluid, reduce the blockage in the flow passage, and improve the flow capacity near blade tip.
    References | Related Articles | Metrics
    Influence of Fuel-Staging Ratio on Combustion Performance of Dual Fuel Combustor
    LIU Aiguo, CHEN Xuanren, YANG Yudong, CHEN Lei, WANG Chengjun
    2020, 54 (7):  756-764.  doi: 10.16183/j.cnki.jsjtu.2019.132
    Abstract ( 842 )   PDF (3055KB) ( 373 )   Save
    The flow field and combustion characteristics of a dual fuel low pollution combustor were studied by using numerical and experimental methods. The low-pollution combustor was numerically simulated by using Fluent software. The ignition and extinguishing characteristics of the combustor were tested experimentally. The fuel energy distribution ratio of duty class and main combustion stage was changed when the inlet parameters of the combustor were fixed. The influence of the energy ratio of the main combustion stage on combustion characteristics was compared and analyzed. The results show that there is a central reflux zone, a corner reflux zone, and a lip reflux zone in the head of the low-pollution combustor studied. The ignition and extinguishing characteristics of the combustor meet the requirements and the fuel classification ratio has a great impact on pollutant emissions. When the dual fuel design point and the gas fuel are used alone, CO and NOx emissions meet the design requirements of the combustor.
    References | Related Articles | Metrics
    Thermal Characteristics Analysis of a Stratospheric Aerostat Based on Multi-Layer Node Model
    DENG Xiaolong, MA Zhenyu, YANG Xixiang, ZHU Bingjie
    2020, 54 (7):  765-770.  doi: 10.16183/j.cnki.jsjtu.2019.013
    Abstract ( 764 )   PDF (1020KB) ( 431 )   Save
    In this paper, a multi-layer node model, which is based on the two-node model, is proposed for thermal analysis of aerostats. The thermal performance simulation of a National Aeronautics and Space Administration (NASA) ultra long duration balloon suggests that the multi-layer node model can provide the distribution of different envelope parts and the development of helium temperature tendency with time. It is found that the diurnal temperature variation between top envelop and bottom envelop is smaller than that of stratospheric airships. It is also concluded that a low helium temperature difference can be reached at a high latitude position and a low helium temperature can be reached at a low altitude. The conclusions are valuable for superheat control of stratospheric aerostats.
    References | Related Articles | Metrics