JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2008 | Volume:35 | Issue:2 (50) MECHANICAL ENGINEERING|Papers Count:8

Efficient design of radiator is of paramount importance in the performance of an automotive cooling system. In this paper, two radiators with different characteristics have been tested, and their behavior appraised. For this purpose, system resistance curves for both radiators have been plotted. Characteristic curves of fans, including the static and total pressure against the flow rate, were plotted and operating points for each radiator determined. Then a test rig, similar to that of an engine's cooling system, was set up for the fan and the radiator. Radiator's inlet flow distribution was precisely measured, using hot wire anemometry, and the inlet airflow pattern was analyzed. A comparison of results reperesents that 15% increase in the number of the blades in unit length can increase pressure drop in radiator and therfore, the air flow rate decreases by 9% at the speed of 2800 r.p.m. However, due to the increase in the heat transfer area, the thermal performance of the radiator has improved and the heat transfer rate has increased by 11%. Road tests on the vehicles also show this improvement in the performance of the cooling system.

In this paper the effect of various heat treatment cycles on mechanical properties and wear resistance of insitu Fe-6vol%TiC composite were studied. The composite were produced insitu by an induction furnace coupled with centrifugal equipments. Various heating cycles such as spheroidizing, quenching in water and quenching plus tempering were performed. Hardness, tensile and wear properties of heat treated specimens and as cast specimen were investigated. Micro structural studies were performed by using optical and scanning electron microscopes. Thus, the hardness, tensile strength and wear resistance were increased by quenching and the elongation was increased by sphroidizing the specimens. However the wear ratio in the as cast condition was maximum.

The purpose of the current work is to develop a solution method for incompressible Navier-Stokes equations, for both velocity and temperature fields, based on artificial compressibility concept. The equations are discretized in Finite-Volume formulation, convective fluxes are calculated using a high-order characteristic-based Roe-like flux splitting method. For time-marching, 5th-order Runge-Kuta algorithm, because of its wide range of stability, is used. The formulation can be used for both steady and unsteady flows. The results for three different flux treatments are presented. The first one is a kind of averaging method and the second and third ones are first and second order methods developed by the authors. The method validation is performed by solving velocity and temperature fields over circular cylinder and ribbed surface, and comparing the results by data in literature which a reasonable agreement would exist. The convergence rate of the method shows a sensible reduction in iteration steps.

The dual fuel engines at part loads inevitably suffer from lower thermal efficiency and higher carbon monoxide and unburned hydrocarbon emission. In this respect, exhaust gas recirculation (EGR) and its temperature can be used as an effective way to improve the performance and emission parameters of these engines at part load conditions. Therefore, experimental works conducted on an IDI dual fuel engine to investigate the effect of different amounts of EGR temperature on combustion process, performance and emissions of these engines. The amount of EGR conducted into the engine has been 10 percent and different amounts of EGR temperature have been considered. Results of this work show that CO and TUHC emissions reduce and NOx emission increases very low. Moreover, performance parameters show better behavior in comparison with baseline dual fuel engine (without EGR).

In this research project, the properties and characterization of Iranian bauxite extracted from Loushan mines is compared with one type of industrial China's refractory grade bauxite in order to be used in refractory industries. At first physical, chemical, thermal, phase and micro structural properties of as received and sintered samples of Iranian Bauxite at different temperatures were analyzed and then were compared with China's calcined bauxite properties. The results showed that the refractory bauxite minerals obtained from Iranian Loushan mines contains the proper amounts of alumina and other oxides. So it could be concluded that these properties are comparable to the China's one and this refractory grade bauxite is suitable for refractory industries for using in the production of many kinds of shaped and monolithic refractory products.

In this paper, we have studied a FSI model to simulate fluid-solid interaction on the blood vessel. The computer simulation of pulsatile blood flow was carried out based on the time dependent axisymmetric Navier-Stokes equations for incompressible Newtonian fluid flow. An elastic incompressible material with large deformation was considered for arterial wall. The specified boundary conditions for the Navier-Stokes equations are real pulsatile pressure waveform of brachial artery at inflow and outflow. Fluid and solid equations were solved with ALE-based loose coupling method for FSI problems. Results were showed the significant decreasing in time dependent wall shear stress with increasing elastic modulus of vessel wall. Also, at the same pressure gradient and different stiffness of vessel wall, different flow rate was obtained. It can be concluded that the measuring of pressure wave and using it as a boundary condition is non-invasive and more suitable to study the blood vessel characteristics.

Mixing is one of the more practice operations in chemical processes and knowledge of fluid flow profile can help for optimizing the operation considerably. In process of preparation of sodium perborate, Sodium metaborate and hydrogen peroxide, as raw materials, mix and react in presence of a turbine mixer. In this investigation, the role of presence of baffle in velocity profile in mixing tank including a turbine agitator with two impellers has been studied. Regarding this matter, velocity vectors and counters of different sections of tank in two cases; with and without baffles, have been drawn with the aid of computation fluid dynamic (CFD) method. The results show that radial velocities are the same for two cases but presence of baffle affects on vertical velocity. In the other words, baffle can increase turbulence in vertical axe.

In this paper the change in clamping force (preload) value has been investigated in bolted joints under tensile axial load both experimentally and numerically. To do this, a holed plate of Al-Alloy 7075-T6 is clamped at its hole by a bolt and nut, and then the plate is subjected to a tensile axial load. In order to evaluate the bolt clamp force magnitudes due to the applied torque to the nut, an experimental method has been used by measuring the compressive axial stress from the axial strain of a steel bush that was located between the nut and the plate. The investigation was carried out on two specimens that were clamped by two different torques. In each specimen the clamp force was measured at first and then its changes were recorded during the axial tensile load that was applied to the plate ends. In the numerical part, 3-D finite element models were used to simulate the bolt clamping process and the changes in clamping force when the plate is subjected to the tensile axial load. Both experimental and numerical methods show that the clamping force is reduced during tensile axial load application. This is due to the transverse plate contraction that causes the clamp to relax. The percentage of clamping force reduction is more pronounced at the joint where bigger torque was applied to the nut.