Table of Content

28 August 2024, Volume 58 Issue 8 Previous Issue    Next Issue

Mechanical Engineering

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Experimental Study of Influence of Secondary Combustion on Combustion Characteristics of Axial Staged Combustor SUI Yongfeng, ZHANG Yuming, ZANG Peng, JIA Yuliang, HENG Sijiang, FU Yanni, GE Bing 2024, 58 (8):  1139-1147.  doi: 10.16183/j.cnki.jsjtu.2023.076 Abstract ( 329 )   HTML ( 29 )   PDF (4916KB) ( 557 )   Save In order to obtain the influencing rule of secondary combustion on emissions and combustion oscillation characteristics of gas turbine axial staged combustor in non-premixed combustion mode and explore a load increasing mode with stable low emission, an axial staged combustor for F-class gas turbines is selected for experimental study. The results show that CO consumption is restrained and CO emission increases sharply when secondary fuel is added at a lower combustor outlet temperature. The addition of secondary fuel and the increase of secondary equivalence ratio lead to the reduction of NOx emission, but the increase of load can weaken the ability of secondary fuel to reduce NOx emission. The addition of secondary fuel and the increase of secondary equivalence ratio restrain the combustion oscillation in the low frequency band (75—90 Hz). When the secondary equivalence ratio is higher than a certain threshold (0.19), the addition of secondary fuel can restrain higher frequency(175—210 Hz) combustion oscillation. In addition, by comprehensively considering the influence of secondary combustion on emissions and combustion oscillation, the operating range and load increasing mode of low emissions and stable combustion of axial staged combustor in the higher load range (20%—50% load) are obtained, which provides a reference for stable low emission operation of the unit during load increasing. Figures and Tables | References | Related Articles | Metrics

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Droplets Evaporation Characteristics of Diesel from Direct and Indirect Coal Liquefaction and Their Blends SHEN Yukun, WANG Jigang, QIAO Xinqi 2024, 58 (8):  1148-1155.  doi: 10.16183/j.cnki.jsjtu.2023.195 Abstract ( 158 )   HTML ( 10 )   PDF (4746KB) ( 210 )   Save To study the evaporation characteristics of diesel from direct coal liquefaction (DDCL), diesel from indirect coal liquefaction (DICL), and their blended fuel droplets at different ambient temperatures (500, 600 and 700 ℃), a droplet evaporation test apparatus based on the suspension method was used to suspend droplets using crossed quartz wires, and a fuel with very similar physicochemical properties to diesel was obtained by blending of DDCL and DICL at a mass ratio of 29∶21 by using the fuel design method. It is shown that the evaporation pattern of DDCL, DICL, and their blended fuel droplets is similar to that of diesel fuel, and they all show a two-stage evaporation. The deviation from the classical d2 law is large below 600 ℃, and the deviation from the d2 law gradually decreases with the increase of ambient temperature. At all three ambient temperatures, the blended fuel droplets exhibit a better evaporation performance than diesel, with 27.2%, 46.3%, and 19.6% higher average evaporation rates than diesel, respectively, providing supporting data for the application of coal liquefied diesel in diesel engines. Figures and Tables | References | Related Articles | Metrics

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Temperature Control Scheme for Gas Turbine of Combined Cycles with Exhaust Gas Recirculation LI Keying, CHEN Kun, JIANG Zepeng, LI Chao, GUO Xiaoguo, ZHANG Shijie 2024, 58 (8):  1156-1166.  doi: 10.16183/j.cnki.jsjtu.2023.126 Abstract ( 194 )   HTML ( 12 )   PDF (3707KB) ( 215 )   Save Under partial-load conditions, the combined application of exhaust gas recirculation of heat recovery steam generator and compressor inlet guide vane adjustment (EGR-IGVC) can effectively improve the performance of gas turbine combined cycle. However, if this strategy is combined with the temperature control scheme of constant T3(turbine inlet temperature)-T4m(maximum allowable turbine exhaust temperature), which is often adopted in gas turbine combined cycles under part-load conditions, it would cause a large bottoming cycle exergy destruction and a significant decrease in bottoming cycle power output at relatively lower loads. In this paper, a constant T3-T4m-T4d (the design value of turbine exhaust temperature) scheme suitable for the EGR-IGVC strategy is proposed, the PG9351FA gas turbine combined cycle unit is taken as the research object, and the partial-load performance of combined cycle under the two temperature control schemes is compared and investigated based on energy and exergy analysis. The results show that the combination of the EGR-IGVC strategy with the constant T3-T4m scheme is still the best at the ambient temperature of 15 ℃ and the partial-load rate of above 80%. At a load of 30%—80%, compared with the constant T3-T4m scheme, the EGR-IGVC strategy combined with the constant T3-T4m-T4d scheme can increase the gas turbine efficiency by 0.15%—0.47%, and decrease the exergy destruction of the heat recovery steam generator by more than 0.51%(2.15 MW). The results also show that adopting the constant T3-T4m-T4d scheme can always obtain higher combined cycle efficiency when the ambient temperature varies between 0 and 40 ℃. In addition, the increase in partial-load efficiency becomes more evident with the rise of ambient temperature. Figures and Tables | References | Related Articles | Metrics

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Effect of Non-Equilibrium Plasma Pretreatment on Combustion Characteristics of Propane/Air Mixtures XIONG Yong, ZHAO Qingwu, LIU Peng, LIU Jingyuan, CHENG Yong 2024, 58 (8):  1167-1178.  doi: 10.16183/j.cnki.jsjtu.2022.464 Abstract ( 149 )   HTML ( 13 )   PDF (20291KB) ( 185 )   Save The feasibility of using non-equilibrium plasma to pretreat in-cylinder mass at low in-cylinder pressures in internal combustion engines to improve the combustion process is explored. In a propane/air mixture with an initial pressure of 0.1 MPa, an initial temperature of 303 K, and an equivalence ratio of 1, and based on a high-frequency nanosecond pulse-driven along-surface dielectric barrier discharge plasma generation system, the morphology and energy characteristics of discharge of propane-air mixture and the effect on combustion at different ignition intervals and numbers of discharge pulse are studied in a constant-volume combustion bomb. The results of the discharge test show that the energy of a single pulse is about 5.2 mJ. The average power is 30 kW, and 80 pulses at 80 μs intervals produce approximately 40 discharge channels. When the mixture is treated with 80 pulses at 80 μs intervals, the combustion duration is reduced by 1.33 ms, which is a 16% reduction. As the number of discharge pulses increases, the burning duration first decreases linearly and then stabilizes, and the duration of combustion increases with the increasing ignition interval. Figures and Tables | References | Related Articles | Metrics

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Numerical Study of Combustion Characteristics of Methane/Hydrogen Hybrid Fuel of Lean Premixed Swirl WANG Xinci, LIU Aiguo, WU Xiaoqu, ZHANG Yunjie 2024, 58 (8):  1179-1187.  doi: 10.16183/j.cnki.jsjtu.2022.502 Abstract ( 149 )   HTML ( 11 )   PDF (22873KB) ( 1094 )   Save The numerical simulation method is used to study the influence of the mixing ratio of methane/hydrogen mixture on the combustion characteristics and pollutant emission characteristics of the combustor. The results show that due to the action of combustion chemical reaction, there exists a certain difference in the structure of cold and hot flow fields. The flow velocity of the hot flow field increases, and the recirculation zone becomes larger. The hydrogen content has a significant impact on the structure and temperature distribution characteristics of the hot flow field, and a central recirculation zone is formed when the hydrogen content is less than 20%, which can maintain stable combustion. When the hydrogen content is greater than 40%, the central recirculation zone disappears, the external recirculation zone is extended, and the spontaneous combustion and flashback occur to varying degrees. As the inlet air temperature increases, the spontaneous ignition phenomenon becomes more obvious, and the inlet air temperature decreases, the flashback phenomenon becomes more obvious. NOx emissions increase with the increase of hydrogen content, CO emissions decrease with the increase of hydrogen content, and CO is concentrated in the combustion zone of the main combustion stage. Figures and Tables | References | Related Articles | Metrics

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Measurement of Gas-Liquid Two-Phase Flow in Draft Tube LI Jinfeng, CHEN Wuguang, ZHANG Zhengchuan, XU Yongliang, LI Kaiying, YIN Junlian, WANG Dezhong 2024, 58 (8):  1188-1200.  doi: 10.16183/j.cnki.jsjtu.2023.091 Abstract ( 130 )   HTML ( 15 )   PDF (65901KB) ( 238 )   Save The limitation of traditional measurement technology in gas-liquid two-phase flow measurement is broken through.The liquid velocity field and vortex rope morphology from two vertical directions were measured synchronically by using particle image velocimetry and pulsed shadowgraphy technique. Experimental measurements show that the vortex rope in the draft tube presents three kinds of unstable circulation flow evolution, single spiral, double spiral, and overstocked rupture. When a single spiral vortex rope is partially split into two, it becomes a double spiral vortex rope. When the local spiral rise angle of a single spiral vortex rope decreases, it becomes an overstocked rupture. When there is a single spiral vortex rope in the draft tube, the vortex rope rotates precession around the central axis along with the liquid main flow, and the flow is divided into two parts, the outer main flow zone and the central stagnation zone, according to the axial velocity. The shear layer between the main flow zone and the stagnation zone rolls up to form several vortices. The position of liquid vortices determines the spatial morphology of the spiral vortex rope. Figures and Tables | References | Related Articles | Metrics

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Testing Method for Thermal Diffusivity of Solid Materials Based on Combined Boundary Conditions CHEN Qinghua, WU Jiale, LU Yu, JI Jiadong, LIU Ping 2024, 58 (8):  1201-1210.  doi: 10.16183/j.cnki.jsjtu.2023.018 Abstract ( 140 )   HTML ( 8 )   PDF (5652KB) ( 144 )   Save A method for measuring the thermal diffusivity of solid materials under combined boundary conditions in combination with the idea of inverse heat transfer problem is proposed. Based on the idea of the finite volume method and the alternating direction implicit method, MATLAB software is used to numerically solve the temperature field of the forward problem. The conjugate gradient method in combination with software programming is used to solve the inverse problem, and the thermal diffusion coefficient of the material is obtained by inversion. Based on the test principle, an experimental scheme is designed and a complete test system is built. The structure design, selection, and machining of the device equipment for constructing three types of boundary conditions and collecting temperature data are performed. The main program of each functional module of the software part is programmed and debugged in LabVIEW software. The comprehensive experiments of acrylic plate (PMMA), borosilicate glass (Pyrex7740) and marble are conducted by using the test device. The results show that the maximum relative deviation between the thermal conductivity test results and the literature values is 3.45%, less than 5%, which verifies the feasibility and accuracy of the test method and device. The uncertainty of PMMA thermal diffusion coefficient experiment is further analyzed, and the expanded uncertainty is 4.86%, which is at a low level, indicating that the experimental data are reliable and the test method is scientific. Figures and Tables | References | Related Articles | Metrics

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Maintenance Modeling of Remanufacturing Systems in Variable Working Condition with Coupling of Production Scheduling and Reliability XIAO Changsheng, ZHOU Xiaojun, ZHU Mixin 2024, 58 (8):  1211-1220.  doi: 10.16183/j.cnki.jsjtu.2023.113 Abstract ( 152 )   HTML ( 10 )   PDF (2389KB) ( 201 )   Save For the multi-process remanufacturing system under variable working conditions, a modeling method considering the coupling among equipment deterioration, maintenance, and production is proposed. First, a dynamic production priority considering equipment reliability is introduced, based on which, a production scheduling plan is generated. Then, an equipment hazard rate model under variable production plan is established. On this basis, a dual-cycle dynamic maintenance decision-making method is constructed, considering the dynamic nature of production scheduling plan and the uncertainty of equipment failure. The illustrative example shows that the model can effectively improve the net profit of the system and has more advantages than traditional production and maintenance decision-making methods. Figures and Tables | References | Related Articles | Metrics

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Opportunistic Maintenance Modeling of Large-Scale Hot Rolling Production Line Based on Maintenance Priority and Dual Variable Time Window MAO Wenxin, ZHOU Xiaojun 2024, 58 (8):  1221-1230.  doi: 10.16183/j.cnki.jsjtu.2023.173 Abstract ( 74 )   HTML ( 12 )   PDF (1391KB) ( 85 )   Save To solve the problem of differential maintenance demand caused by daily dynamic maintenance and periodic replacement of support rolls in large-scale hot rolling lines, a maintenance priority rule is introduced to identify maintenance judgment order of components under long distance condition and downtime constraint. A dual variable time window rule is constructed to identify whether components should be maintained and distinguish maintenance demand, and then a dynamic opportunity maintenance model is established for the system. The case study shows that the model can effectively solve the problem of differential maintenance scheduling for large-scale hot rolling lines under the constraints of maintenance resources and downtime, and has more cost advantages than the traditional time-window-based model. Figures and Tables | References | Related Articles | Metrics

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Design and Motion Analysis of Bionic Jaw Mechanism for Humanoid Expression Robot ZHAO Wei, YUAN Shaoke, LI Yinan, FEI Yanqiong 2024, 58 (8):  1231-1239.  doi: 10.16183/j.cnki.jsjtu.2022.469 Abstract ( 165 )   HTML ( 12 )   PDF (26383KB) ( 255 )   Save In order to solve the current problem of a single oral motion mode for the humanoid expression robot, a novel multi degree of freedom (DOF) bionic jaw mechanism was designed based on the anatomical motion mechanism of the human jaw. The inverse kinematics model of the mechanism was established, and the motion mode of the mechanism was analyzed to realize the multi DOF motion of the bionic jaw mechanism in space. A multi rigid body simulation of the bionic jaw mechanism was conducted, whose feasibility was verified by the experiments. The simulation and experimental results demonstrate that, based on the inverse kinematics model, the mechanism designed is able to simulate the three basic motion modes of human jaw, including open-close movement, protrusion movement, and side shifting movement, as well as the complex oral motion modes including chewing and lip biting. Therefore, the proposed mechanism can compensate for the limits of oral movement patterns of the existing humanoid robots. Figures and Tables | References | Related Articles | Metrics

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Development of a Small Jellyfish Robot with Controllable Trajectory WANG Qi, LI Lüzhou, DONG Xu, YUAN Ningyi, DING Jianning 2024, 58 (8):  1240-1248.  doi: 10.16183/j.cnki.jsjtu.2023.135 Abstract ( 129 )   HTML ( 19 )   PDF (34182KB) ( 130 )   Save In order to solve the problem of efficient trajectory control of centimeter-scale robots with small size, a small jellyfish robot (JRT) is designed and developed, which is composed of an air chamber, a center of gravity adjustment device and a jellyfish-inspired thruster with a size of only ⌀6.8 cm × 5.3 cm. Its trajectory can be effectively controlled underwater through the coordination of the center of gravity adjustment device and jellyfish-inspired thruster. Underwater experiments verify the function of JRT swimming and hovering in the vertical direction, horizontal directional swimming, and horizontal ejection. By analyzing the force balance relationship and motion state data of JRT swimming in the vertical and horizontal directions, a trajectory control scheme is proposed. The speed of horizontal directional swimming can reach 1.7 cm/s, and the trajectory deviation is 0—3.4 cm, which shows that the JRT has a good trajectory control ability and is expected to be applied in underwater resource exploration, environmental monitoring, and other fields. Figures and Tables | References | Related Articles | Metrics

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Modeling of Multi-Modal Knowledge Graph for Assembly Process of Wind Turbines with Multi-Source Heterogeneous Data HU Zhiqiang, LIU Mingfei, LI Qi, LI Xinyu, BAO Jinsong 2024, 58 (8):  1249-1263.  doi: 10.16183/j.cnki.jsjtu.2023.062 Abstract ( 395 )   HTML ( 16 )   PDF (11842KB) ( 1437 )   Save The assembly process information of wind turbines is usually scattered in process documents consisting of multi-modal information, such as 3D models, natural texts, and images. Therefore, the cost of maintaining data and extracting process knowledge is high while the efficiency is low. To solve this problem, a multi-modal knowledge graph-based modeling method for the assembly process knowledge of wind turbines is proposed with multi-source heterogeneous data. First, the concepts in multi-modal process knowledge graph of wind turbine (MPKG-WT) are defined by analyzing the process characteristics of wind turbines to complete the construction of ontology. Then, based on the characteristics of multi-source heterogeneous data and multi-modal information, data analysis, knowledge extraction, and semantic similarity calculation are leveraged to realize the automatic instantiation of the graph. Finally, taking the process data of a wind turbine enterprise as an example, MPKG-WT is constructed and verified by implementing an auxiliary system for process design. The results show that MPKG-WT is more informative than the single-modal graph, and the data in different modals can complement each other, which leads to significant improvements in the efficiency of process design. Figures and Tables | References | Related Articles | Metrics

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Simulation and Experimental Validation of Landing Distribution Characteristics of Aircraft Mass Fire Extinguishing Bags Sprayed at High Altitude WU Yang, LIN Dong, SUN Haoran, WU Chengyun, QU Yuanyuan, LI Xuan, HU Haitao, CHEN Yingchun 2024, 58 (8):  1264-1270.  doi: 10.16183/j.cnki.jsjtu.2023.014 Abstract ( 155 )   HTML ( 8 )   PDF (1609KB) ( 397 )   Save In order to optimize the design of high-altitude sprinkling system of fire-fighting aircraft, it is necessary to establish a model reflecting the high-altitude spraying and distribution mechanism of mass fire extinguishing bags during the flight. Based on the discrete element method and the computational fluid dynamics method, a high-altitude spraying and distributing model of aircraft mass fire extinguishing bags is established, and the spraying characteristics and landing area distribution at different flight speeds and altitudes are obtained. The model is verified by experiments. The deviations between simulated landing distribution and experimental data are less than 20.0%. The research results provide a theoretical model for the development of aircraft high altitude fire extinguishing system, so as to significantly improve the fire extinguishing performance of aircraft spraying system. Figures and Tables | References | Related Articles | Metrics

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Stochastic Due-Date Lot-Streaming Flowshop Scheduling with Benders Decomposition and Branch-and-Bound SHI Yadong, LIU Ran, WANG Chengkai, WU Zerui 2024, 58 (8):  1271-1281.  doi: 10.16183/j.cnki.jsjtu.2023.070 Abstract ( 216 )   HTML ( 15 )   PDF (1434KB) ( 439 )   Save The lot-streaming flowshop scheduling problem with stochastic due time is addressed in this paper, with the objective of minimizing the sum of expected job delays. Closed-form expressions for the expected delays of jobs are derived under three classical distribution conditions. A mathematical model is then formulated, considering set-up times and stochastic due time. To address the highly nonlinear nature of the model, a linearization is performed. Furthermore, an optimization algorithm is designed using a Logic-based Benders decomposition (LBBD) approach combined with branch-and-bound. Two effective acceleration strategies are introduced to improve the efficiency of the algorithm. The numerical experiments demonstrate the effectiveness of the proposed algorithm, and the necessity of considering stochastic lead times is verified by comparing the results with those obtained from deterministic due time. Figures and Tables | References | Related Articles | Metrics

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Construction of Combined Variable-Section Scroll Tooth Profiles Using Algebraic-Archimedes Double Spiral YAN Min, LIU Tao, MA Dequan, DANG Xu 2024, 58 (8):  1282-1289.  doi: 10.16183/j.cnki.jsjtu.2022.532 Abstract ( 268 )   HTML ( 13 )   PDF (1811KB) ( 288 )   Save The mathematical model of the profile is complicated and the connection conditions are not easily obtained by explicit calculation because different model parameters are used for different types of curves. To address the above problems, a new scroll profile is proposed by double spiral which is the combination of algebraic spiral and Archimedes spiral. First, based on the conjugate mesh theory, the relationship between the spindle angle and the pole angle of the curve is solved to derive the normalized mathematical model of the scroll line of the spiral type. Then, based on the smooth connection conditions of the combined profiles, the constraint equations of the connection points of the double spiral scroll profiles are established, and the geometric models of the two types of double spiral scroll profiles are obtained. Afterwards, the effects of the parameters of the first type of double spiral combined profile (spiral index, spiral coefficient, and pole angle of the connection point) on the geometric performance of the scroll teeth are quantitatively analyzed. Finally, the performance advantages of the two-screw combination scroll profile are comparatively studied. The results show that the geometry of the first type of double spiral combined profile is simple and can be directly used in production without head profile correction. The stroke volume is increased by 7.61%, the compression ratio is increased by 27.42%, and the area utilization factor is increased by 7.61% compared with the conventional circular involute scroll teeth at the same radial dimension of scroll teeth. Figures and Tables | References | Related Articles | Metrics

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Relaxation Characteristics of Hold-Down Spring of Core Support Barrel in Nuclear Reactor YANG Taibo, LIU Jiaxin, PENG Zhike, LUO Neng, LIU Caixue 2024, 58 (8):  1290-1296.  doi: 10.16183/j.cnki.jsjtu.2023.024 Abstract ( 188 )   HTML ( 10 )   PDF (5304KB) ( 259 )   Save The stability of the core support barrel (CSB) in a nuclear reactor is the guarantee and premise for the normal operation of the reactor core. As the constraint and support of the CSB, the hold-down spring (HDS) directly affects the vibration characteristics of the CSB. Under harsh conditions such as high temperature and radiation, degradation such as stress relaxation may occur in terms of the performance of the HDS, which will affect the vibration of the CSB and the operation security of the reactor. Therefore, it is necessary to study the relaxation characteristics of the HDS of the CSB. First, a finite element model including the CSB and the HDS is established. The wet modal method is adapted to analyze and obtain the change of the beam mode frequency of the CSB with the relaxation degradation of the HDS. Then, a relaxation test of the HDS of the CSB is conducted to verify the simulation results. The simulation model is further used to generate more beam mode frequency data of the CSB under the impact of different relaxation degrees of the HDS. Finally, combined with simulation and test data, a mathematical model for identifying the relaxation degree of the HDS of the CSB is established, which lays a technical foundation for monitoring the relaxation and degradation of the HDS of the CSB in nuclear reactor. Figures and Tables | References | Related Articles | Metrics