Transactions of the Canadian Society for Mechanical Engineering
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Volume 34 (2010), Issue 3-4
Thermocapillary effects in liquid systems of variable mass confined in a non-isothermal container
Mohamed M. El-Gammal, Jerzy M. Floryan, Jr
Interface deformation and thermocapillary rupture in a non-isothermal cavity with free upper surface is investigated. Temperature variations along the interface are induced by differentially heated walls. The dynamics of the process is modulated by changing mass of the liquid. The results determined for the large Biot and zero Marangoni numbers show the existence of limit points beyond processes leading to the interface rupture set in. Evolution of the limit point as a function of the liquid mass is investigated. The topology of the flow field is very similar regardless of whether the cavity is over-filled or only partially filled. It is shown that the cavity over-filling may, in general, extend the range of admissible capillary numbers and thus it can be used as a tool for prevention of rupture.
Nonlinear vibration of a three-dimensional moving gantry crane subjected to a travelling trolley hoisting swinging object
Davood Younesian, Elyas Ghafoori, Mehdi Sadeghpour
Nonlinear vibration of a three-dimensional moving gantry crane carrying a trolley hoisting a swinging object is studied in this paper.A finite element method is used to solve nonlinear coupled governing equations of the structure. A combinational technique (Newmark-Runge-Kutta) is employed for direct integration procedure. To develop a comprehensive parametric study and sensitivity analysis of the coupled nonlinear system, sequence of numerical simulations are carried out. Parametric study is directed to find out how different parameters like speed and acceleration of the trolley and gantry crane as well as the mass of the moving trolley and swinging object may affect the linear and nonlinear responses of the structure. It is found that the nonlinearity arises from large amplitude of three-dimensional motion of the swinging object.
MHD flow and heat transfer of two immiscible fluids between moving plates
Stamenkovic M. Zivojin, Dragisa D. Nikodijevic, Bratislav D. Blagojevic, Slobodan R. Savic
The magnetohydrodynamic (MHD) flow of two immiscible and electrically conducting fluids between isothermal, insulated moving plates in the presence of an applied electric and inclined magnetic field has been investigated in the paper. The partial differential equations governing the flow and heat transfer are solved analytically with appropriate boundary conditions for each fluid and these solutions have been matched at the interface. The numerical results for various values of the Hartmann number, the angle of magnetic field inclination, load parameter and the ratio of electrical and thermal conductivities have been presented graphically. It was found that decrease of magnetic field inclination angle flattens out the velocity and temperature profiles. With the increase of the Hartmann number velocity gradients near the plate’s increases, temperature in the middle of the channel decreases and near the plate’s increases. Induced magnetic field is evidently suppressed with an increase of the Hartman number. The effect of changes of the load factor is to aid or oppose the flow as compared to the short-circuited case.
Boundary slippage for improving the load and friction performance of a step bearing
The present paper proposes a new type of step bearing by specifically modifying the interfacial condition between the fluid film and the bearing surface and introducing the boundary slippage at those interfaces. Analysis for the load-carrying capacity and friction coefficient is presented for this kind of bearing. The comparison of the obtained analytical results with the conventional (no-slippage) step bearing results shows that modifying the interfacial condition and introducing the boundary slippage at the specific bearing surfaces can significantly increase the load-carrying capacity and reduce the friction coefficient of a step bearing. Design guideline, the load-carrying capacity and the friction coefficient are also presented for this bearing at optimum condition which reaches the maximum load-carrying capacity.
Application of abrasive-water jet technology for material sculpturing
Przemyslaw J. Borkowski
This paper presents a novel method for the 3D sculpturing of different materials using a highpressure abrasive water jet. The approach involves scanning an image, such as a photograph, and relating the color values of each pixel in the resulting bitmap image to the feed rate of the water jet. Keeping all other parameters such as stand-off distance and water pressure constant, different water jet feed rates will causes different levels of erosion of material. As a result, a three-dimensional sculptured surface will be realized from a two-dimensional image. The paper describes a mathematical model for shaping the material, as well as the experimental testbed used to test the novel approach. Also presented are methodical and experimental erosion results as well as a particular example of bas-relief made of metal.
Fuzzy Taguchi deduction optimization on multi-attribute CNC turning
In this paper, four parameters with three levels are considered to optimize the multi-attribute finish CNC (computer numerical control) turning based on L9 (34) orthogonal array. Additionally, nine fuzzy control rules with respective to five linguistic grades for each attribute are constructed. The TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) is moreover utilized to integrate and evaluate the multiple machining attributes for Taguchi experiment to receive the optimum general deduction parameters. It is shown that the attributes from the fuzzy Taguchi deduction optimization parameters are all significantly advanced comparing to those from benchmark.
Numerical analysis of displacements in spatial mechanisms with spherical joints utilizing an extended D-H notation
Spherical joints consist of a pair of concave and convex spherical surfaces engaged in such a way as to prevent translational motion of the ball and socket whilst simultaneously allowing three degrees of rotational freedom. The kinematics of spatial mechanisms comprising links and joints are commonly analyzed using the Denavit-Hartenberg (D-H) notation. However, whilst this method allows the kinematics of mechanisms containing prismatic, revolute, helical and cylindrical joints to be explicitly defined, it cannot be directly applied to mechanical systems containing spherical pairs. Accordingly, this paper proposes an extended D-H notation which allows the independent parameters of any spatial mechanism, including one with spherical pairs, to be derived for analysis and synthesis purposes. The validity of the proposed notation is demonstrated via its application to the analysis of mechanisms containing revolute (R), spherical (S), cylindrical (C) and prismatic (P) joints. The results confirm the viability of the extended D-H notation as a means of analyzing the displacements of mechanical systems containing kinematic chains such as RSCR, RSCP, CSSR and CSSP.
Optimization of the C3MR cycle with genetic algorithm
Hamidreza Taleshbahrami, Hamid Saffari
The aim of this paper is thermodynamic simulation and optimization of the C3MR system with Genetic Algorithm. For this purpose, in the first step, the Peng Robinson equation of state is simulated with a code in MATLAB and then used for simulating thermodynamic properties of natural gas and refrigerants that are used in the cycle. Following that the cycle is thermodynamically simulated and composite curves for subcooling and liquefaction heat exchangers are plotted. If composite curves in heat exchangers approach, the total power will decrease. Then, the total power used by the compressors is calculated. In the next step, the thermodynamic modeling is linked with Genetic Algorithm and the total power consumed by compressors is defined as objective function. The best value resulted from optimization has 23% lower power than the base design. In addition, heat exchange curves closed together.
Design of a load cell with large overload capacity
To increase the signal-to-noise (S/N) ratio and sensitivity of a load cell, it is desirable to design a structure that generates large strain close to maximum allowable strain of the sensor material for a given rating load force. However, accommodating the margin of safety with respect to overloading, compromises the sensitivity. This paper presents the design, analysis, and prototype testing of a load cell which can provide large overload protection capacity without compromising the sensitivity of the sensor. This is achieved by a special design of sensor structure that becomes virtually rigid after its flexures reach their maximum deflection, thereby the sensor can be protected against a large over load. The sensor dimensions, which maximizes the sensor’s sensitivity, for given values of rating load and overload are obtained through mechanical strength analysis. A load cell prototype is fabricated and then tested to measure its linearity and overload characteristics. The experimental results show an accuracy of 0.2% of full scale and overload protection of the sensor flexures.
Pareto based multi-objective optimization of solar thermal energy storage using genetic algorithms
Abolfazl Khalkhali, Mohamadhosein Sadafi, Javad Rezapour, Hamed Safikhani
Net energy stored (Qnet) and the discharge time of Phase Change Material (tPCM) in a solar system, are important conflicting objectives to be optimized simultaneously. In the present paper, multi-objective genetic algorithms (GAs) are used for Pareto approach optimization of a solar system using modified NSGA II algorithms. The competing objectives are Qnet and tPCM and design variables are some geometrical parameters of solar system. It is shown that some interesting and important relationships as useful optimal design principles involved in the performance of solar system can be discovered. These important results can be used for better design of a solar system.
Asymptotic analysis soot model for a high pressure common rail diesel engine
Tao Qiu, Zhiquan Qi, Wenhui Yin, Yongfeng Liu
A TP (Temperature Phase) model is presented to carry out optimization calculation for a highpressure common rail diesel engine. Temperature is the most important parameter in the TP model. When zone temperature T<1500 K, only the soot precursors –PAHs (Polycyclic aromatic hydrocarbons) is created and there is no soot emission. When zone temperature T≥1500 K, PAHs and soot source terms (particle inception, surface growth, oxidation, coagulation) are calculated. The TP model is then implemented in KIVA code instead of original model to carry out optimizing. The results of cylinder pressures, the corresponding heat release rates, and soot with variation of injection time, variation of rail pressure and variation of speed among TP model, KIVA standard model and experimental data are analyzed. The results indicate that the TP model can carry out optimization and CFD (computational fluid dynamics) and can be a tool to calculate for a high-pressure common rail diesel engine.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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