Analytical and Numerical Investigation on Eccentric Journal Bearing

In this paper, analytical and numerical analyses of radial and tangential velocities and pressure of lubricant film have been considered in an eccentric journal bearing. A 2D flow of shear-thinning viscous fluid is followed by Carreau-Yasuda mathematical model between two eccentric cylinders. The model is mathematically conserved from eccentric coordinate to concentric coordinate due largely to easy solution. Therefore, the PDE equations were converted to the ODE equations with a set of nonlinear algebraic first order equations with their boundary conditions. These kinds of equations are called boundary value problems (BVP) that can be solved with shooting method. The results are compared with 2D numerical simulation in the Fluent software. Lubricant tangential velocity and pressure distributions are examined in the dynamic journal bearing. The comparison of the results revealed that numerical analysis as same as analytical approach is a reliable method for determining lubricant motion in the gap.

Exergy Analysis of Steel Electric Arc Furnace

In this paper, energy and exergy analysis of an existing steel electric arc furnace (EAF) was performed to estimate the furnace potential for increasing the efficiency and decreasing the electrical energy consumption. The results of analysis show that the energy and exergy efficiencies of the furnace are 56.9% and 40.5%, respectively. Field data show that mass flow rate of hot flue gas is around 10.4 kg/s in average which contains 18.3% and 12.2% of total input energy and exergy, respectively. By using energy of flue gas for preheating the sponge iron, electrical energy consumption of the furnace could be reduced up to 88 GJ which means 21.2% reduction in electrical energy consumption and 13.6% increase in steel production. Also, exergy efficiency improves about 10.8% by using preheating scheme.

Experimental Study of Natural Gas Fuel Temperature Influence on Radiation Enhancement and Emission

The enhancement of the flame radiation in gas fueled burners not only improves the thermal efficiency, but also can suppress the rate of NO emission due to reducing the flame temperature. In this experimental investigation, the effect of inlet gas temperature on the flame radiation intensity and the rate of NO formation are studied. To serve this aim, with increasing the temperature of inlet methane to the burner up to 310°C, the variations of CO and NO level in exhaust gases and also the exhaust gas temperature are recorded by gas analyzer device. In each case, the flame radiation intensity was also measured by a photovoltaic module. The results revealed that by increasing the inlet gas temperature up to 250°C, the NO concentration and the exhaust gases temperature are raising. But when the inlet gas temperature exceeds from 250°C and reaches to 310°C, the flame luminosity gradually increases which results in 70 percent growth in flame radiation and 10 percent drop in exhaust gas temperature. The results of the preheating of inlet air also show the same behavior.

Thermodynamic Analysis of a Combined Power and Water Production System

Most of the potable water and electricity are produced by dual purpose plants. Dual-purpose plants are the one that supplies heat for a thermal desalination unit and produces electricity for distribution to the electrical grid. In this paper a power plant is combined with a multi-effect evaporation thermal vapor compression (METVC) system. Compared with the most widely used (Multi Stage Flash) MSF desalination, METVC has more advantages. Then, energy and exergy analysis equations for desalination plant, power generation cycle, heat recovery steam generator and combined power and water cycle are developed and the results are presented. Results show by rising number of effect from 2 to 14, performance ratio, exergy efficiency and specific heat transfer area rise steadily. For combined system, the maximum and minimum values of exergy destruction rate are related to combustion chamber and desalination effects, respectively. Also, with increasing TIT, exergy destruction rate of power generation cycle decreases while the exergy destruction rate of METVC, especially thermo compressor, goes up and fresh water production reduces dramatically.

Some Properties of Stratified Composites

The multi-component composites could represent the cheapest solution when controllable properties are required. In order to establish the right amount of filler it is necessary to analyze not only the electro-magnetic and mechanical properties but also, the thermal ones. The filler presence in the matrix produces discontinuities at the fibre-matrix interface with consequences regarding mechanical properties. Using a single filler it is possible to improve one or two properties electrical and thermal conductivity for instance and mean time to induce a decrease of other properties as bending strength, shock resistance etc. Using polymer layers with relatively high electrical conductivity as external layers of laminate and magnetic particles filled polymer as core layers. An electric circuit might be, at the same time, the reinforcement of a composite leading to lighter structures and, based on carbon fiber’s properties might transmit information about the material’s loading, temperature or integrity. Fabric reinforced or textile composites are used in aerospace, automotive, naval and other applications. They are convenient material forms providing adequate stiffness and strength in many structures. The microstructure of composite reinforced with woven, braided, or stitched networks is significantly different from that of tape based laminates. The properties of the composite depend not only on the properties of the components but on quality and nature of the interface between the components and its properties. Reinforced composites with filled epoxy matrix were formed using a hybrid technique consisting in layer-by-layer adding of reinforcement sheets into a glass mould. Various distributions of reinforcement sheets and filled polymer layers were realized in order to point out the ways in which the final properties might be controlled. Mechanical properties were analyzed.

Densification Behavior of Metal Powder Under Uniaxial Cold Compaction

Metal powder compaction is a quite important process in Powder Metallurgy (PM) industry and it is widely applied in the manufacturing of key components in different fields. During metal powder compaction, the solid volume fraction changes and many mechanical characteristics become different. The Finite Element simulation provides a flexible and efficient approach for the researches of this process and its complicated mechanical behaviors. In this paper, several 2D finite element spherical powder compaction models are generated. Different particle arrangements are build up and different friction coefficients are set to the inter-particle contacts and die wall contact for a certain arrangement. The Von Mises yield surface with isotropic hardening plasticity model is applied in the simulation and the displacement controlled load is used to compress the structure up to 25% of die height. Results show that the die wall friction increases compaction pressure but inter-particle friction has negligible effect.

Modeling and Experimental Verification of a Novel SMA-Actuated Robotic Module

Robotic modules with especial abilities may provide new opportunities in developing robotic systems. Changing the robot framework in different missions may be implemented in the modular robotic system design. Shape memory alloys (SMA) may be considered as suitable actuators with unique features. Due to the complex behavior of the SMAs less works are done on the precise modeling and positioning systems of them. Spring type SMA actuators, which are less considered in the literature, produce more deflections. In this paper a novel module with two DOFs is developed. SMA springs are employed as actuators in an embedded package including a mechanism, an electronic hardware, and a sensory system. Modeling of the spring type SMA is discussed in details using Liang and Brinson models. Simulation results are verified using an experimental setup indicating the applicability of the model in predicting the dynamic behavior of the module.

Controllability and Maintenance of Human Trunk Response Surface for Isometric Extension Strength

From an ergonomic point of view, quantitative assessment of the feasibility of the task performance is an intricate process, which combines the multidimensional task demand profile with the individual’s multidimensional performance capacity profile. Trunk muscle strength is affected by the trunk posture but it is not clear how the variability of trunk muscle is affected by the trunk posture or exertion level. A validated triaxial dynamometer, Sharif-LIST, was used for to model the surface response of trunk muscle extension strength variability as a function of trunk posture in the sagittal, coronal and transverse planes in standing position. Fifteen healthy males with no history of low back pain in the previous year participated in this study. A full factorial method was used to design the experiments to fit a second-order model of response surface method (RSM) with block effect (BE). For the first time in the literature, the results of this study indicate that the quadratic RSM model is suitable to represent the trunk extension strength variability in terms of its coefficient of variation (CV) and standard deviation (SD) of maximum trunk torque as a function of trunk posture in coronal and sagittal planes (R2 = 0.6, p<0.5). These results showed that in the positions with higher trunk strength values, the higher standard deviation and lower coefficient of variation were observed which is consistent with previous findings.

Experimental Analysis of PEM Fuel Cells With Biomimetical Mixed Flows as Gas Distributors

A proton exchange membrane fuel cell (PEMFC) is an electrochemical device that converts the chemical energy from the gases into electrical energy. The PEMFCs consist of many parts, and the current collector plate is one of the key components among them. Channels in the bipolar plate distribute air on the cathode side and hydrogen on the anode side. Theoretically a fuel cell produces more current as more fuel is supplied. However the way in which the gases are supplied affects dramatically the performance of the cell. The present paper shows how the mixed flows improve the current density produced by fuel cells. Polarization and power density curves are presented. The results suggest that a flow with two levels of bifurcations is preferred for the anode side. This behavior is expected due to the similitude with the performance of the natural world in which geometries with this type of bifurcations transport the nutrients inside the tree leaves and plants.

Mechanical Characterization of Fiber Fabrics

Fabric reinforced or textile composites are increasingly used in aerospace, automotive, naval and other applications. They are convenient material forms providing adequate stiffness and strength in many structures. In such applications they are subjected to three-dimensional states of stress coupled with hydro-thermal effects. Assuming that a composite material is a complex structure it is obvious that is hard to describe all its properties in terms of its parts properties. The properties of the composite depend not only on the properties of the components but on quality and nature of the interface between the components and its properties. As reinforcement two types of fiber fabric were used; first one is a simple type fabric of untwisted tows of carbon filaments while the second one is also simple type but as yarn and fill are used alternately untwisted tows of carbon and aramide filaments. There were some problems to be solved before molding: fabric stability during handling, cutting, imbuing the carbon and aramide tows are slipping one on each other leading to fabric defects; generally the epoxy systems do not adhere to the carbon fiber; in order to obtain a valuable material the nature of interface must be the same for polymer-carbon fiber and polymer aramide fiber. In order to solve these problems the two fabrics were covered (by spraying) with a thin film of PNB rubber. Into the rubber solution were also dispersed small amounts of clay (to create a better interface) and carbon black (to improve the electrical conductivity). The rubber presence solves the fabric stability problem; ensures the same type of interface between fibers and polymer matrix; ensures a more elastic interface between fibers and polymer matrix. This treatment induces modification on tensile behavior of fabrics. This study is about mechanical evaluation of such fabrics.