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Numerical Simulation and Analysis of Power Consumption and Metzner-Otto Constant for Impeller of 6PBT

Chinese Journal of mechanical engineering 2014年第3期27卷 635-640页

作者： LUAN Deyu CHEN Qiao ZHOU Shenjie school of mechanical and Electrical engineering Qingdao University of Science and Technology school of mechanical engineering Shandong University

Majority of non-Newtonian fluids are pseudoplastic with shear-thinning property, which means that the viscosity will be different in different parts of the stirred tank. In such mixing process, it is difficult to predict accurately the power consumption and mean shear rate for designing novel impeller. Metzner-Otto method is a widely accepted method to solve these questions in mixing non-Newtonian fluids. As a result, Metzner-Otto constant will become a key factor to achieve an optimum way of economical mixing. In this paper, taking glycerine and xanthan gum solutions as research system, the power consumption, stirred by the impeller composed of perturbed six-bent-bladed turbine （6PBT） with differently geometrical characteristics in a cylindrical vessel, is studied by means of computational fluid dynamics （CFD）. The flow is modeled as laminar and a multiple reference frame （MRF） approach is used to solve the discretized equations of motion. In order to determine the capability of CFD to forecast the flow process, the torque test experiment is used to measure the glycerine solution power consumption. The theological properties of the xanthan gum solutions are determined by a Brookfleld rheometer. It is observed that the power consumption predicted by numerical simulation agrees well with those measured using torque experiment method in stirring glycerine solution, which validate the numerical model. Metzner-Otto constant is almost not correlated with the flow behavior index of pseudoplastic fluids. This paper establishes the complete correlations of power constant and Metzner-Otto constant with impeller geometrical characteristics through linear regression analysis, which provides the valuable instructions and references for accurately predicting the power consumption and mean shear rate of pseudoplastic fluids in laminar flow, comparatively.

关键词： impeller composed of perturbed six-bent-bladed trbine pseudoplastic fluids power constant Metzner-Otto constant

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Spindle Thermal Error Optimization Modeling of a Five-axis Machine Tool

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Chinese Journal of mechanical engineering 2017年第3期30卷 746-753页

作者： Qianjian GUO Shuo FAN Rufeng XU Xiang CHENG Guoyong ZHAO Jianguo YANG school of mechanical engineering Shandong University of Technology school of mechanical engineering Shanghai Jiao Tong University

Aiming at the problem of low machining accu- racy and uncontrollable thermal errors of NC machine tools, spindle thermal error measurement, modeling and compensation of a two turntable five-axis machine tool are researched. Measurement experiment of heat sources and thermal errors are carried out, and GRA（grey relational analysis） method is introduced into the selection of tem- perature variables used for thermal error modeling. In order to analyze the influence of different heat sources on spindle thermal errors, an ANN （artificial neural network） model is presented, and ABC（artificial bee colony） algorithm is introduced to train the link weights of ANN, a new ABC- NN（Artificial bee colony-based neural network） modeling method is proposed and used in the prediction of spindle thermal errors. In order to test the prediction performance of ABC-NN model, an experiment system is developed, the prediction results of LSR （least squares regression）, ANN and ABC-NN are compared with the measurement results of spindle thermal errors. Experiment results show that the prediction accuracy of ABC-NN model is higher than LSR and ANN, and the residual error is smaller than 3 pm, the new modeling method is feasible. The proposed research provides instruction to compensate thermal errors and improve machining accuracy of NC machine tools.

关键词： Five-axis machine tool Artificial bee colony Thermal error modeling Artificial neural network

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Fast image retargeting based on strip dividing and resizing

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Journal of Systems engineering and Electronics 2014年第6期25卷 1072-1081页

作者： Shungang Hua Honglei Wei Tieming Su school of mechanical engineering Dalian University of Technology school of mechanical and Power engineering Dalian Ocean University

Based on image strip dividing, an effective and fast image retargeting algorithm is proposed for resizing images. First,we construct the image energy map using gradient magnitude of the pixels and calculate the accumulated energy of each column,dividing the image into several strips by integrating similar energy columns. The reduced amount of dimension is decided in inverse proportion to the average energy for each strip. Then we retarget the image combining scaling with cropping in terms of each strip＇s reduced ratio. Experiment results show that the proposed algorithm is capable of implementing fast image retargeting and preserving both the local structures and the global visual effect of the image.

关键词： image retargeting strip dividing energy map scaling cropping

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Fractal Prediction Model of Thermal Contact Conductance of Rough Surfaces

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Chinese Journal of mechanical engineering 2013年第1期26卷 128-136页

作者： JI Cuicui ZHU Hua JIANG Wei school of mechanical and Electrical engineering China University of Mining and Technology school of mechanical engineering University of Leeds

The thermal contact conductance problem is an important issue in studying the heat transfer of engineering surfaces, which has been widely studied since last few decades, and for predicting which many theoretical models have been established. However, the models which have been existed are lack of objectivity due to that they are mostly studied based on the statistical methodology characterization for rough surfaces and simple partition for the deformation formats of contact asperity. In this paper, a fractal prediction model is developed for the thermal contact conductance between two rough surfaces based on the rough surface being described by three-dimensional Weierstrass and Mandelbrot fractal function and assuming that there are three kinds of asperity deformation modes： elastic, elastoplastic and fully plastic. Influences of contact load and contact area as well as fractal parameters and material properties on the thermal contact conductance are investigated by using the presented model. The investigation results show that the thermal contact conductance increases with the increasing of the contact load and contact area. The larger the fractal dimension, or the smaller the fractal roughness, the larger the thermal contact conductance is. The thermal contact conductance increases with decreasing the ratio of Young＇s elastic modulus to the microhardness. The results obtained indicate that the proposed model can effectively predict the thermal contact conductance at the interface, which provide certain reference to the further study on the issue of heat transfer between contact surfaces.

关键词： rough surface fractal thermal contact conductance prediction model

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Alleviation of spike stall in axial compressors utilizing grooved casing treatment

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Chinese Journal of Aeronautics 2015年第3期28卷 649-658页

作者： Reza Taghavi-Zenouz Sarallah Abbasi school of mechanical engineering Iran University of Science and Technology school of mechanical engineering Arak University of Technology

Abstract This article deals with application of grooved type casing treatment for suppression of spike stall in an isolated axial compressor rotor blade row. The continuous grooved casing treatment covering the whole compressor circumference is of 1.8 mm in depth and located between 90% and 108% chord of the blade tip as measured from leading edge. The method of investigation is based on time-accurate three-dimensional full annulus numerical simulations for cases with and without casing treatment. Discretization of the Navier Stokes equations has been carried out based on an upwind second-order scheme and k-a-SST （Shear Stress Transport） turbulence modeling has been used for estimation of eddy viscosity. Time-dependent flow structure results for the smooth casing reveal that there are two criteria for spike stall inception known as leading edge spillage and trailing edge backftow, which occur at specific mass flow rates in near-stall conditions. In this case, two dominant stall cells of different sizes could be observed. The larger one is caused by the spike stall covering roughly two blade passages in the circumferential direction and about 25% span in the radial direction. Spike stall disturbances are accompanied by lower frequencies and higher amplitudes of the pressure signals. Casing treatment causes flow blockages to reduce due to allevi- ation of backflow regions, which in turn reduces the total pressure loss and increases the axial veloc- ity in the blade tip gap region, as well as tip leakage flow fluctuation at higher frequencies and lower amplitudes. Eventually, it can be concluded that the casing treatment of the stepped tip gap type could increase the stall margin of the compressor. This fact is basically due to retarding the movement of the interface region between incoming and tip leakage flows towards the rotor leading edge Diane and suttressing the reversed flow around the blade trailing edee.

关键词： Axial compressor Casing treatment Frequency spectrum Spike stall inception Tip leakage flow

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Moisture effect on the combustion of a single copper concentrate particle in a flash smelting furnace

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International Journal of Minerals,Metallurgy and Materials 2014年第3期21卷 251-258页

作者： E.Hassan Zaim S.H.Mansouri A.Arab Solghar Department of mechanical engineering School of Engineering Shahid Bahonar University Department of mechanical engineering School of Engineering Vali-e-Asr University

A mathematical model has been presented to study the combustion of a single copper concentrate particle with high moisture content. By using the presented model, the effect of particle moisture content on particle temperature, sulfur oxidation, and combustion heat generation has been evaluated. The mineralogical composition of the commonly used concentrate at Khatoonabad flash smelting furnace has been used in this study. It was found that the particle moisture content is removed in the sub-second time range and thus the moisture has marginal impact on the variation of particle temperature and on the reaction rate when the gas temperature is assumed to be constant in the reaction shaft. When a concentrate with high moisture content is charged, the particle size enlargement due to the agglomeration of concentrate particles causes an abrupt fall in the particle reaction rate.

关键词： flash smelting furnaces copper smelting moisture combustion

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Stifness modeling and analysis of a novel 4-DOF PKM for manufacturing large components

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Chinese Journal of Aeronautics 2013年第6期26卷 1577-1585页

作者： Li Yonggang Zhang Erjiang Song Yimin Feng Zhiyou school of mechanical engineering Tianjin University of Technology and Education school of mechanical engineering Tianjin University school of Electromechanical engineering Tianjin Polytechnic University

Faster response to orientation varying is one of the outstanding abilities of a parallel kinematic machine（PKM）.It enables such a system to act as a reconfgurable module employed to machine large components *** stiffness formulation and analysis are the beforehand key tasks for its parameters design.A novel PKM with four degrees of freedom（DOFs）is proposed in this *** topology behind it is 2PUS-2PRS parallel *** semianalytical stiffness model is frstly obtained,where the generalized Jacobian matrix of 2PUS-2PRS is formulated with the help of the screw theory and the stiffness coeffcients of complicated components are estimated by integrating fnite element analysis and numerical *** the help of the model,it is predicted that the property of system stiffness distributes within the given workspace,which features symmetry about a certain plane and is also verifed by performing fnite element analysis of the virtual ***,key parameters affecting the system stiffness are identifed through sensitivity *** provide insights for further optimization design of this PKM.

关键词： Manufacturing Parallel kinematic machine Stiffness Semi-analytical method Finite element analysis

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Theoretical analysis of the sound absorption characteristics of periodically stiffened micro-perforated plates

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Acta Mechanica Sinica 2014年第5期30卷 714-726页

作者： Hai-An Zhou Xiao-Ming Wang Yu-Lin Mei school of mechanical engineering Shandong University of Technology school of mechanical engineering Dalian University of Technology school of Automotive engineering Dalian University of Technology

The vibro-acoustic responses and sound absorption characteristics of two kinds of periodically stiffened micro-perforated plates are analyzed theoretically. The connected periodical structures of the stiffened plates can be ribs or block-like structures. Based on fundamental acoustic formulas of the micro-perforated plate of Maa and Takahashi, semi-analytical models of the vibrating stiffened plates are developed in this paper. Approaches like the space harmonic method, Fourier transforms and finite element method （FEM） are adopted to investigate both kinds of the stiffened plates. In the present work, the vibro-acoustic responses of micro-perforated stiffened plates in the wavenumber space are expressed as functions of plate displacement amplitudes. After approximate numerical solutions of the amplitudes, the vibration equations and sound absorption coefficients of the two kinds of stiffened plates in the physical space are then derived by employing the Fourier inverse transform. In numerical examples, the effects of some physical parameters, such as the perforation ratio, incident angles and periodical distances etc., on the sound absorption performance are examined. The proposed approaches are also validated by comparing the present results with solutions of Takahashi and previous studies of stiffened plates. Numerical results indicate that the flexural vibration of the plate has a signif- icant effect on the sound absorption coefficient in the water but has little influence in the air.

关键词： Absorption- Stiffened- Micro-perforated Spaceharmonic - Finite element method

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Intelligent monitoring-based safety system of massage robot

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Journal of Central South University 2016年第10期23卷 2647-2658页

作者：胡宁李长胜王利峰胡磊徐晓军邹雲鹏胡玥沈晨 school of Automation Science and Electrical engineering Beihang University school of mechanical engineering and Automation Beihang University school of mechanical and Electrical engineering Harbin Engineering University

As an important attribute of robots, safety is involved in each link of the full life cycle of robots, including the design, manufacturing, operation and maintenance. The present study on robot safety is a systematic project. Traditionally, robot safety is defined as follows: robots should not collide with humans, or robots should not harm humans when they collide. Based on this definition of robot safety, researchers have proposed ex ante and ex post safety standards and safety strategies and used the risk index and risk level as the evaluation indexes for safety methods. A massage robot realizes its massage therapy function through applying a rhythmic force on the massage object. Therefore, the traditional definition of safety, safety strategies, and safety realization methods cannot satisfy the function and safety requirements of massage robots. Based on the descriptions of the environment of massage robots and the tasks of massage robots, the present study analyzes the safety requirements of massage robots; analyzes the potential safety dangers of massage robots using the fault tree tool; proposes an error monitoring-based intelligent safety system for massage robots through monitoring and evaluating potential safety danger states, as well as decision making based on potential safety danger states; and verifies the feasibility of the intelligent safety system through an experiment.

关键词： robot fault tree safety strategies for robots intelligent safety

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An eikonal equation based path planning method using polygon decomposition and curve evolution

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Defence Technology（防务技术） 2020年第5期16卷 1001-1018页

作者： Zheng Sun Zhu-Feng Shao Hui Li school of mechanical and Electrical engineering Zaozhuang UniversityZaozhuang277160China Department of mechanical engineering School of Mechanical EngineeringTsinghua UniversityBeijing100084China

Path planning is a key technique of autonomous navigation for robots,and the velocity field is an important *** velocity field in a complex workspace is still *** this paper,an inner normal guided segmentation algorithm in a complex polygon is proposed to decompose the complex workspace in this *** artificial potential field model based on probability theory is then used to calculate the potential field of the decomposed workspace,and the velocity field is obtained by utilizing the potential field of this *** optimization is implemented by curve evolution,during which the internal force generated in the smoothing process of the initial path by a mean filter and the external force is obtained from the gradient of the workspace potential *** parameter selection principle is deduced by analyzing the influence of several parameters on the path length and *** results show that the designed polygon decomposition algorithm can effectively segment complex workspace and that the path optimization algorithm can shorten and smoothen paths.

关键词： Level set Path planning Artificial potential field Polygon decomposition Path optimization Curve evolution

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