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Journal of Jiangsu University(Natural Science Eidtion)

	2021 Vol.42 Issue.3 Published 2021-05-10

	249	Analysis of coaxial injection characteristics of natural gas/diesel dual fuel engine
		LI Yulan1,2, WANG Qian1， HUANG Yingjie1， SHAO Changsheng1， KANG Jiaming1， XIANG Yingjie1
		The high-speed schlieren method was used to carry out the coaxial injection test of natural gas/diesel dual fuel engine, and the effects of gas injection pressure and environmental pressure on the perimeter variation of three profiles of natural gas injection were analyzed. The numerical simulation was carried out by CFD software, and the natural gas volume fraction and velocity field were analyzed by ENSIGHT software. The results show that the circumference of three profiles of natural gas jet is decreased with the decreasing of natural gas injection pressure and the increasing of ambient pressure, and profile curves of dual fuel injection are more violent than that of single fuel injection. When the head of the natural gas jet meets the diesel spray, part of the natural gas stops at the head of jet, which affects the gas volume fraction of the whole jet. The smaller the injection pressure of natural gas is, the greater the effect of diesel is. The velocity is decreased from the head to the bottom of the natural gas jet. There are many vortices and vorticity fields in the middle of the jet, and there is a small turbulence intensity in the area where the diesel spray and the natural gas jet collide.
		2021 Vol. 42 (3): 249-256 [Abstract] ( 36 ) [HTML 1KB] [ PDF 4864KB] ( 407 )

	257	Experiment on assembly contact pressure of PEM water electrolyzer
		LONG Pan1,2, LUO Maji1,2,3, CHEN Ben1,2
		Because the pressure distribution on the membrane electrode assembly（MEA）had great influence on the performance of proton exchange membrane water electrolyzer（PEMWE）, the influence of assembly scheme on the pressure distribution on the MEA was investigated. The MEA was replaced by pressure-sensitive paper, and the PEMWE was assembled by different assembly schemes. The pressure distribution on pressure-sensitive paper was analyzed by experimental observation and image processing, and the influence of assembly scheme on the pressure distribution on the MEA was obtained. The experimental results show that with the increasing of clamping pressure, the pressure on the MEA is gradually increased and is more evenly distributed, while the excessive pressure can lead to the damage of cathode diffusion layer. The scheme 5 is the best assembly scheme to ensure the sealing effect and pressure distribution of MEA.
		2021 Vol. 42 (3): 257-263 [Abstract] ( 53 ) [HTML 1KB] [ PDF 15492KB] ( 491 )

	264	Performance analysis of battery cooling system based on mini-channel cold plate
		SONG Decai, DONG Fei, CHENG Ziyang, WAN Junshen
		To solve the problem of high temperature for lithium-ion battery during high rate discharge, a new type of cold plate was designed based on mini-channel, and the computational fluid dynamics (CFD) was used to simulate the cooling effects of battery module. The cooling properties of cold plates with different channel types were compared to select the channel type with better temperature performance and the effects of inlet mass flow of coolant and channel structure parameters were analyzed based on the optimized channel type. The results show that the channel combined in series and parallel has good performance, which can lower the temperature of battery module and improve the temperature uniformity with reduced coolant pressure drop. The increasing of coolant mass flow rate can improve the cooling effect, which slows down gradually. The increasing of channel width can reduce the average temperature of battery module and improve temperature uniformity, and the maximum temperature is decreased with latter slight increasing. With the increasing of channel height, the coolant flow rate is decreased, and the maximum battery temperature and the temperature difference are increased.
		2021 Vol. 42 (3): 264-270 [Abstract] ( 69 ) [HTML 1KB] [ PDF 6104KB] ( 398 )

	271	Experiment on explosion characteristics of methane and n-heptane
		WEI Yi1, PAN Jianfeng1, GABEL Dieter2
		To effectively prevent gas and liquid (vapor) explosion accidents in industrial production, it is necessary to obtain explosion characteristics of relevant gases and liquids. Based on the traditional 20 L spherical explosion test apparatus, the maximum explosion pressure(pmax), the maximum explosion pressure rise rate((dp/dt)max) and the deflagration index (KG) of methane and n-heptane with different concentrations were measured and analyzed under quiescent and flowing conditions. The results show that the pmax and (dp/dt)max values of methane are increased with latter decreasing and reach the peak values at 11%concentration under both conditions. The pmax and (dp/dt)max values of n-heptane show the same rule under flowing conditions and reach the peak values at 4% concentration. The optimal explosive concentrations of two alkanes are about 11% and 4%, respectively. The pmax values of two alkanes at optimal explosive concentrations are increased slightly by about 5% to 10% under flowing conditions, and the corresponding (dp/dt)max values are significantly increased by about 4 to 5 times, which leads to large explosion energy release and high explosion reaction rate. The KG values are also increased by 4 to 5 times, resulting in high destructiveness and hazard of explosions.
		2021 Vol. 42 (3): 271-277 [Abstract] ( 38 ) [HTML 1KB] [ PDF 3086KB] ( 479 )

	278	Transient flow characteristics and pressure pulsation characteristics at splitter of double-volute centrifugal pump during startup
		YANG Jingjiang1, ZHOU Runze1, CHEN Huilong2, YU Tianbao1
		To investigate the transient flow characteristics of the liquid inside volute and the pressure pulsation characteristics at the splitter during startup process of double-volute centrifugal pump, a double-volute centrifugal pump with specific speed of 90 was used as research object, and a set of circulating pipeline system was established. According to RNG k-ε turbulence model, ANSYS CFX software was used to simulate the three-dimensional unsteady state of double-volute centrifugal pump and circulating pipeline system. The evolution law of flow field and the variation tendency of hydraulic characteristics during startup process were analyzed, and the changes of pressure pulsation at different splitter positions were compared. The results show that at the beginning of startup, the flow velocity inside volute changes sharply, and the high-speed regions appear at the tongue and the initial position of splitter. There is an obvious velocity gradient at the entrance of volute. With the increasing of rotate speed, the high-speed regions are gradually decreased, and the internal flow tends to be stable. During the startup process, the pressure pulsation amplitudes at the initial position and the end position of splitter are relatively large, and the pressure pulsation on the outer side of splitter is more stable than that on the inner side of splitter.
		2021 Vol. 42 (3): 278-283 [Abstract] ( 47 ) [HTML 1KB] [ PDF 5272KB] ( 418 )

	284	Numerical simulation of a droplet colliding with a spherical particle
		DU Min， SONG Liang， SUN Wentao， WANG Yuecheng
		To investigate the rules of collision between a droplet and a spherical particle, a physical model was established to reflect the collision. The model was used to simulate the dynamic collision process, and the droplet radius spreading coefficient and the liquid film center height coefficient were also investigated. The effects of parameters of impact velocity, wetting angle and size ratio of droplet to particle on the collision were analyzed. The results show that within the scope of this paper, the increasing of impact velocity can increase the maximum radius spreading coefficient. When the impact velocity is 04 m·s-1, the droplets rebound completely. When the impact velocity is increased to 14 m·s-1, the droplets are broken. When the impact speed and the size ratio of droplet to particle are constant, the wetting angle is proportional to the maximum liquid film center height coefficient. When the wetting angle is less than 90°, with the increasing of size ratio of droplet to particle, the probability of droplet coating is increased.
		2021 Vol. 42 (3): 284-290 [Abstract] ( 43 ) [HTML 1KB] [ PDF 16138KB] ( 304 )

	291	Analysis of spray′s breakup and atomization of elliptical diesel nozzle under high injection pressure
		LU Dayong, JIA Hekun, YE Ze
		The large eddy simulation (LES) and the volume of fluid (VOF) model were coupled to investigate the mechanisms of spray axis-switching phenomenon and breakup process for elliptical orifice at different high injection pressures of 120, 140 and 160 MPa with fixed backpressure of 3 MPa. The effects of primary breakup process on the macro spray were analyzed based on the macro spray tests of circular and elliptical diesel nozzles. The results show that the elliptical orifice undergoes the axis-switching phenomenon even under high injection pressure, and the number of axis-switching phenomena is increased with the increasing of injection pressure. The injection pressure has little effect on the primary elliptical spray liquid core length, while the increasing of injection pressure is helpful to accelerate the liquid core breakup into small droplets.With the increasing of injection pressure, the more vortex structures which promote the formation of spray mushroom-like structures are generated at the spray head. Considering with the characteristics of primary elliptical spray, the turbulence of primary elliptical spray is improved by the increasing of injection pressure, which is helpful to intensify the instability of primary breakup process and improve the quality of macro spray.
		2021 Vol. 42 (3): 291-297 [Abstract] ( 37 ) [HTML 1KB] [ PDF 4678KB] ( 416 )

	298	Toothbrush gesture recognition method based on deep learning
		WANG Huaming, LIU Maoxing, XIONG Junfeng, YU Jinlong
		To solve the positioning problem in toothbrush sorting, a method was proposed based on deep learning for toothbrush positioning and gesture recognition. The image of toothbrush was denoised and enhanced, and the interested region was extracted by threshold segmentation. The geometric moment of image was calculated to obtain the direction angle of toothbrush and the outer rectangle. The center of outer rectangle was taken as the center of toothbrush to determine the toothbrush position. The residual network model was trained with the toothbrush image in the rectangular box. When the accuracy of the model reached the requirement, the model was saved to judge the attitude of toothbrush in the image. The test results show that the method can quickly and accurately realize the position determination and gesture recognition of toothbrush, and provide the posture information for the robot operation.
		2021 Vol. 42 (3): 298-302 [Abstract] ( 42 ) [HTML 1KB] [ PDF 20853KB] ( 309 )

	303	Multi-dimensional deep-sea fish recognition algorithm
		LI Chen1, LIU Yidan1,2, SUN Kelin1, LI Bo1, QUAN Xiangqian1, LIU Kaibin1
		To solve the difficulty of fish recognition and detection due to the nonuniformly distributed deep-sea light,the multi-dimensional deep-sea fish recognition algorithm was proposed based on visual cognition. The traditional GMM was optimized to initially determine the changing area from time dimension and construct the target features from space dimension for extracting the moving target completely. The fish recognition framework based on deep learning was established from spatio-temporal correlation dimension. The results show that the proposed algorithm can accurately extract moving objects under variously complex conditions. The AOM is more than 80%, which is better than that of current mainstream algorithms.
		2021 Vol. 42 (3): 303-308 [Abstract] ( 39 ) [HTML 1KB] [ PDF 6337KB] ( 412 )

	309	Multi-label classifier chain method based on gradient boosting
		WANG Jin， CHEN Yu， SUN Kaiwei
		To determine the chain order of the multi-label classifier chain algorithm and mine the high-level label corelation, a multi-label classifier chain method was proposed based on gradient boosting. The overall framework of GBCC was given, and the gradient boosting of a single label was conducted by pre-pruning strategy. In the process, the label confidence and error evaluation scores were used to determine the optimal chain order, and the label transfer and feature transfer were performed among labels to mine the high-level label relevance. The proposed method was compared with 4 classifier chain algorithms of CC, ECC, OCC and EOCC and 4 multi-label classification algorithms of BR, HOMER, MLKNN and CLR on 12 multi-label data sets such as bibtex and Corel5k. The results show that the new method can effectively improve the prediction performance under various evaluation indicators of micro-F1, macro-F1, Hamming loss and One-error with maintaining the flexibility of classifier chain algorithm.
		2021 Vol. 42 (3): 309-317 [Abstract] ( 51 ) [HTML 1KB] [ PDF 1870KB] ( 401 )

	318	Action recognition based on multiple time scale two-stream CNN and confidence fusion in video
		CHEN Jie， ZHAN Yongzhao
		In view of the changes in video sampling and the different movement speed of target subject, to solve the problems of the current deep network learning with single video sequence feature and the multiple action classifiers with different classification confidence, the video action recognition method was proposed based on multi time scale two-stream CNN and confidence fusion. Two-stream network was used to learn and extract the context information features between video frames of different time span on multiple time scales, and LSTM was used to predict the action categories with various characteristics. For each scale and mode of action classifier, the confidence of category determination was established with consideration of overall difference and uniqueness of category between the sample and other categories. Each classifier was used to fuse the confidence degree and the score of the action category decision for recognizing the video action. The video action recognition experiments were performed on the dataset of UCF101. The results show that the proposed method can effectively learn the contextual information of multiple time scales of videos and improve the accuracy of video action recognition to 92.2%.
		2021 Vol. 42 (3): 318-324 [Abstract] ( 35 ) [HTML 1KB] [ PDF 1852KB] ( 581 )

	325	Stability analysis of power supply circuit of aircraft transformer rectifier
		YANG Zhangang， CAI Jin， HUANG Kun， XU Haiyi
		To solve the problem that the line parameters of the power supply circuit of aircraft transformer rectifier could affect the stability of system, the influence trend of the line parameters on the stability was analyzed to select the appropriate parameters. The dq transform method was used to transform the power supply circuit of converter rectifier, and the mathematical model of circuit was obtained from the equivalent circuit. The steady-state operating point data were obtained by power flow calculation of the power supply circuit of converter rectifier, and the sensitivity of the line parameters was calculated at the steady-state operating point based on the circuit mathematical model. The influence trend of parameters on the small disturbance stability of the power supply circuit of converter rectifier was analyzed emphatically. The Simulink was used to simulate and verify the sensitivity calculation. The results show that increasing inductance, resistance and DC inductance on AC side, or reducing inductance and load power on DC side is beneficial to improve the stability of the power supply circuit of converter rectifier.
		2021 Vol. 42 (3): 325-330 [Abstract] ( 55 ) [HTML 1KB] [ PDF 1496KB] ( 475 )

	331	Test and parameter optimization of regaining and cleaning in multiple-pass cleaning device
		JIN Chengqian1, 2, LI Qinglun2
		To solve the problems of the cleaning load caused by multiple removal in the multi-channel cleaning device of wheat combine harvester and the decreasing of cleaning performance caused by high impurity content of the secondary double-threshing auger, through bench test, the ratio of the total mass of retreat agglutinate from the weight of grains, stalks and residual extracts was used as test index. The re-extracting parts of the multi-channel cleaning device with great influence on cleaning performance were selected with feeding amount, damper opening, fan speed, upper and lower wind deflector angles as test factors. The Box-Benhnken central combination design method was used to conduct five-factor three-level response surface test, and the Design-Expert software was used to respond to the test results for surface analysis.The effects of various factors on the test index were investigated to create relevant mathematical model. The experimental results show that the damper opening, the upper and lower wind guide angles have great influence on the ratio of total mass of grain extractives, stalks and residual extractives. Through multi-objective optimization, the best matching parameters are obtained. Under the parameters combination, the test verification results of the mass ratios of grains, stalks and residual extracts are 89.90%, 2.51% and 7.50%, respectively,which indicates that the appropriate components ratio in the secondary double-throwing auger in the multi-channel cleaning device can meet the requirements of cleaning performance.
		2021 Vol. 42 (3): 331-338 [Abstract] ( 28 ) [HTML 1KB] [ PDF 6878KB] ( 369 )

	339	Predicted optimizing mixture ratio of composite curing agent for soft clay based on PSO-SVM coupling algorithm
		PAN Binjie1, ZHU Jianfeng1,2, XU Riqing3,4
		To realize accurate prediction on the optimizing mixture ratio of composite curing agent for soft clay, according to the experimental data of unconfined compressive strength (qu) of solidified clay, a prediction model of qu for solidified clay was established based on SVM. The maximum unconfined compressive strength of solidified clay was taken as objective function, and the PSO-SVM coupling algorithm for the optimizing mixture ratio of composite curing agent for soft clay was proposed by combining particle swarm optimization algorithm (PSO). The effects of the maximum iteration number (Nmax) and the particle number (Np) on the prediction results of PSO-SVM algorithm were discussed. The results show that the accuracy of PSO-SVM algorithm is better than that of response surface method, and the proposed PSO-SVM algorithm is suitable for the determination of the optimizing mixture ratio of composite curing agent for any soft clay at a specific curing age. It is also suggested that using the proposed PSO-SVM algorithm, Nmax and Np should be greater than 60 and 40, respectively.
		2021 Vol. 42 (3): 339-345 [Abstract] ( 49 ) [HTML 1KB] [ PDF 2033KB] ( 430 )

	346	Energy consumption analysis of energy dissipation structure with fail-safe layers
		LI Tong, LIAO Guangming
		The basic principles and the current status of development of fail-safe design and energy dissipation were introduced, and the energy consumption of energy dissipation structures with fail-safe layers was analyzed based on the seismic energy analysis of structures. The fail-safe design and energy dissipation theories were used to effectively dissipate seismic energy and improve the seismic resistance of structures. The models were established by SAP2000 software to analyze the seismic resistance of structures. The results show that in terms of seismic resistance and cost effectiveness, the energy dissipation frame structures with double columns have superior performance, and the double-column design can effectively reduce inter-story displacement and cost. A single damper can absorb a large amount of seismic energy and reduce the energy consumption of primary structural members to ensure the bearing capacity of structures and avoid the safety hazards due to the double-column arrangement on floor.
		2021 Vol. 42 (3): 346-353 [Abstract] ( 28 ) [HTML 1KB] [ PDF 3327KB] ( 351 )

	354	Research progress on physical properties of PCM and energy conservation of light-weight building envelopes outfitted with PCMs
		ZHANG Yuan1,2,3, WEI Yanli1,2, XU Jinfeng1,2
		Considering the problem that the light-weight building materials decrease the heat capacity of building envelopes, the rational utilization of latent heat of phase change material (PCM) is one of potential efficient approaches for avoiding the heat capacity reduction in light-weight building envelopes. The domestic and oversea research works on PCM physical properties were summarized, and the thermal difference between PCMs and traditional insulation materials were compared. The energy conservation research progress of light-weight PCM outfitted building components and the related thermal designing index were summarized. According to domestic weather condition, indoor target temperature and composition of building envelope, the selection idea of PCM in engineering applications was determined with consideration of matched PCM phase change temperature, latent heat and thermal conductivity. The proper usage of PCM in light-weight building envelopes was also proposed with rational PCM locations and amounts in walls with different structural configurations.
		2021 Vol. 42 (3): 354-360 [Abstract] ( 43 ) [HTML 1KB] [ PDF 1100KB] ( 522 )

	361	Experiment of dynamic deformation characteristics of remolded saturated red clay in Chenggong area of Kunming
		YANG Zheng1,2, QU Juntong1, JI Dong1, ZI Xiaolei1， LIU Chao1
		To obtain the dynamic deformation characteristics of saturated red clay under different test conditions, the GDS dynamic triaxial test system was used to investigated the saturated red clay in Chenggong area of Kunming, and the effects of confining pressure, frequency and consolidation ratio on the dynamic deformation characteristics of remolded saturated red clay were discussed. The test results show that with the increasings of confining pressure and dynamic load frequency, the dynamic stress for the same strain is required greater, and the dynamic elastic modulus is increased with decreased damping ratio. With the increasing of consolidation ratio, the dynamic stress for the same strain is required smaller, and the dynamic elastic modulus is decreased with increased damping ratio. Through Hardin-Drnevich hyperbolic model, the dynamic constitutive relation of saturated red clay is fitted with good fitting effect. The fitting parameters under various test conditions are given, and the maximum dynamic elastic modulus and the maximum dynamic shear modulus are calculated.The maximum dynamic elastic modulus and dynamic shear modulus are increased with the increasings of confining pressure and dynamic load frequency, and those are decreased with the increasing of consolidation ratio.
		2021 Vol. 42 (3): 361-366 [Abstract] ( 37 ) [HTML 1KB] [ PDF 1627KB] ( 388 )

	367	Analysis on mechanical property of web and transverse internal force in bridge deck of box girder with corrugated steel webs
		ZHAO Pin1， RONG Xueliang1， YE Jianshu2， CHEN Wei1， WANG Guoan1
		Through the elastic test of one single-box with double-cell test girder for a corrugated steel webs, the vertical deformation and longitudinal deformation of the webs and the transverse strain of the upper flange were tested when the loads were distributed in different transverse locations of the upper flange. The force performance of the web and the transverse force characteristics of the upper flange supported by the web of composite beam were analyzed. The deformation characteristics of side web and middle web were achieved, and the influence of the ratio of web to upper flange line stiffness on the transverse force of upper flange was also obtained. The results show that there are certain differences among the deformations of the middle web, the side web and the support to the upper flange. The change trends of longitudinal strain and vertical strain of the middle web under load are different from that of the side web. The transverse stress of the upper flange of the corrugated steel web box girder is linearly changed with the ratio of web to upper flange stiffness.
		2021 Vol. 42 (3): 367-372 [Abstract] ( 37 ) [HTML 1KB] [ PDF 2166KB] ( 450 )

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