Advances in Mechanics Engineering

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Authors: Qing Wu, Quan Lai Li, Bao An Han
Abstract: A new type of rotary tubular liquid mixer is proposed in this paper. The tubular rotary drum is rotated with stationary spiral blade fixed inside. The wings are fixed on the blades. The fluid is expelled into the rotary drum and is impinged, separated, flowed around and merged under the effect of centrifugal force and blade hindrance. Then the mixing process is finished. The dimension of mixture structure is reduced, meanwhile the mixture efficiency is enhanced and the mixture effect is strengthened. The practicable turbulent flow in the new rotary tubular liquid mixer is analyzed and the influencing factor is discussed, which provides some proofs for the structural improvement, as well as the selection and optimization of structural parameters.
Authors: Lu Zhi Tan, Ji Tian Han, Chang Nian Chen, Peng Cheng Dou
Abstract: An experimental study on critical heat flux (CHF) in a helically-coiled tube cooled with R-134a has been completed in order to assess present fluid-to-fluid modeling approaches. The investigated range of flow parameters for R-134a was: pressure from 0.2 to 0.5 MPa, mass flux values from 50 to 1500 kg m-2 s-1 and inlet quality from -0.2 to 0.1. The CHF data of R-134a have been compared with that of water by applying the Ahmad and the Katto modeling. The water equivalent CHF data translated from R-134a CHF data by using the two modeling approaches have shown a good agreement with the actual water CHF data from previous studies when mass flux exceeds 600 kg m-2 s-1. The results indicate that both the Ahmad and the Katto modeling can be applied only for the high mass flux conditions in helically-coiled tubes.
Authors: Li Ping Zhao, Jian Qiu Zhang, Lei Chen, Xuan Xie, Jun Qiang Cheng
Abstract: Studying the hydrodynamic characteristics of the sloping breakwater of circular protective facing by physical model test and taking a numerical simulation analysis of current field around the circular protective facing with holes under wave action by FLOW—3D.
Authors: Yong Hui Xie, Zhong Yang Shen, Tao Fan
Abstract: In order to investigate the mechanism of flow separation control in conical diffuser by vortex generator jets (VGJs) method, numerical simulations were conducted to discuss the effect of VGJs with different parameters on flow control. The aerodynamic performance in conical diffuser with angle of 14° was tested and analyzed based on Shear-Stress-Transport (SST) simulation. The flow charts at several sections were analyzed, illuminating the formation of complex vortices. Moreover, the effects of 5 VGJs parameters on the diffuser were analyzed by orthogonal analysis. It was shown that the number of jets and the pitch angle of jet showed more profound influence on the flow control by VGJs.
Authors: Yong Hui Xie, Huan Cheng Qu, Hai Yu He
Abstract: The flow separation is susceptible to appear and is known to affect the aerodynamic performance of the low-pressure high-lift cascade. Large Eddy Simulation was adopted in the present work and the periodic moving bar was employed to simulate the unsteady wake upstream of the blade. The flow control of the synthetic jet with unsteady wake was investigated in detail. The upstream wake increased the turbulent level of the boundary layer of the cascade. The synthetic jet got a better control under the effect of the upstream wake.
Authors: Kun Ye, Ren Xian Li
Abstract: Shelter wind wall is one of the most effective devices to reduce crosswind loads acting on trains. The height of the wall and distance between the wall and the center of railway are important factors for design and construction of wind wall. Since the wall design is related to many factors, such as train speeds, transverse wind speeds, types of the wall and so on, up to now, there are still different judgment methods in the optimal height and distance of the wall to get minimum aerodynamic forces on the train. Based on numerical analysis methods of three-dimensional viscous compressible aerodynamics equations, aerodynamic side forces and rolling moments acting on the train are analyzed. With 275 calculation models, include the straight and different radius curve railway with different heights and distances of shelter wind wall, the aerodynamic side forces and rolling moments are calculated. Simulation results show that the optimal height and distance of the wall are not the same during in straight and curve railway. And the direction of aerodynamic side force and rolling moment acting on the head and rear train may be different. The change trends of transverse forces (moments) with the height and distance of the wall are also different.
Authors: Yan Hua Xue, Zhi Guang Wang, Bin Shao, Yu Duan
Abstract: Surface supplied air diving includes those forms of diving where air is supplied from the surface to the diver by a flexible hose. The Surface Supplied Diving Systems (SSDS) are used primarily for operations to 190 feet of seawater. For the safe of surface supplied diving operation, the gas flow and gas pressure of SSDS must be ensured. Based on the hydrodynamic equations of high-pressure gas hose flow, the basic equation for high-pressure gas flow of surface supplied diving system is analyzed, according to which the gas pressure, gas flow and umbilical basic parameters of surface supplied diving operation are affirmed.
Authors: Yong Jun Dong, Xiao Zhang, Jing Fu Guo, Ming Qi Xu, Xue Ming Zhang
Abstract: The water-following capabilities of surface drifting buoy are investigated through analyzing the hydrodynamic factors which influence the buoy’s floating, so as to improve the precision of ocean currents measured by drifters, and optimize the design of drifters. The force balance equation of surface drifting buoy is established, and the wind coefficient of drifter model is obtained and analyzed. A prototype based on GPS (Global Positioning System) and BeiDou-1 (BeiDou Satellite Navigation Experimental System) is designed to collect surface currents near Gulf of Jiaozhou. Calculated results indicate that the velocity data, which take the wind coefficient into account, are more approaching the measuring value of fixed current-meter. That provides some experimental validities to the modelling and designing of surface drifting buoy. This study also shows that the surface trajectory from GPS and BeiDou-1 float provides a new means to measure surface circulations in the global ocean at real time, and that the estimated currents could be one of the important sources to improve our understanding for ocean dynamics characteristics.
Authors: Ye Ping Zhao, Feng Xiao, Xian Guo Han, Peng Zi Sun
Abstract: The effect of airflow in web cleaner fitted to back plate of cylinder on carding force between cylinder and its flat is researched experimentally in carding machine. The carding force is measured by a specially designed dynamometer. Experiment results show the airflow has the influence on the carding force between cylinder and its first to seventeenth flat in the side of taker-in, of which carding force of first five flats has being more influenced by the airflow. As the airflow rate increases, maximum and average carding force of first five flats increase gradually. The airflow is helpful to fibre ascending along needle on the clothing of cylinder and makes the carding force larger. This is a fundamental reason that the airflow increasing makes carding force bigger.
Authors: Lu Zhi Tan, Ji Tian Han, Chang Nian Chen, Peng Cheng Dou
Abstract: Experimental studies on critical heat flux (CHF) have been conducted in a uniformly heated horizontal straight tube and helically-coiled tube respectively with R-134a as the working fluid. The helically-coiled tube has the same heated length and inner diameter with the straight tube and experiments were performed under the following conditions: pressure from 0.4 to 2.5 MPa, mass flux values from 80 to 1500 kg m-2 s-1, inlet quality from -0.23 to 0.28 and critical quality from 0.65 to 0.86. The CHF data of the helically-coiled tube have been compared with that of the straight tube. The results show that the helically-coiled tube gets significant improvement in the CHF values vs. the straight tube under the same conditions and the degree of improvement depends on the mass flux, system pressure, inlet quality and critical quality.

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