JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TABRIZ)
Year:2004 | Volume:30 | Issue:2 (35) MECHANICS|Papers Count:6

In this study, for gypsum and hematite minerals separating from kaolin, the floatation technique that it's selective separation rate is very high, has been used. The effect of three factors; pulp conditioning time, pH and kind of collector, has been considered. All of experiments has been carried out by using cationic collectors (amines), in alkalin environment (pH range between 10.5 to 12.5) and pulp conditioning times of 4, 6, 8 and 10 minutes. The results of chemical analysis of before and after floatation samples, has been compared and the rate of separating capability of gypsum and hematite from kaolin has been defined.

In this paper the turbulent transonic flow around three projectiles are considered using O and H-C grids. The governing equations are solved using finite volume method and marched in time by four-stage Runge-Kutta scheme. The implemented turbulence model is a modified algebraic one based on ReNormalization Group (RNG) theory. Then the computational results are compared with the experimental data. It is found that using the H-C grid it is possible to overcome some restrictions related to the O-grid and also to increase the accuracy of the predictions. Finally a conclusion is presented about the performance of different projectiles.

Liquid phase sintering of pure nickel and titanium powders was used in this research to produce samples of Ni-Ti memory alloy (Nitinol). Effect of compaction pressure, volume fixation, sintering temperature and sintering time on porosity and percentage of the NiTi phase produced during sintering were investigated. Results showed that the effect of temperature and time on porosity depends on the compaction pressure and start and finish of the compound formation reactions during sintering. In order to reduce porosity and prevent volume change, the samples were refrained inside a rigid container (fixture). Although the fixture could cease the changing of the volume to some extent, formation of the new phases as well as post-solidification contraction of the samples caused an increase in porosity of the sample.

Physical state of air-fuel mixture at inflammation instance is one of the factors which can strongly influence on performance and as well on the pollutants of an engine. In homogeneous mixture the amount of NO pollutant would be higher, because of improved combustion process and of high maximum cycle temperature. Effects of entrance location of the EGR fluid on reduction of detrimental effects of cold EGR and as well increasing its capability on further reduction of NO were studied on a 1600 cc carburetor type petrol engine which fits on paykan cars manufactured by Iran– Khodroo Co. Experimental results showed that when the EGR fluid introduced from two different points to air- fuel mixture, reduction on NO was 7% and increase on engine power was 3% higher in comparison with that where the same quantity of EGR was introduced to air- fuel mixture from a single point downstream to throttle valve.

Although the usage of both rectangular and circular settling tanks in water treatment plants is conventional, there is considerable debate on the relative merits of both configurations with no consensus among the experts on which configuration is better. This paper shows hydrodynamics advantages of rectangular tanks by taking into account the complex effects of density differences between entered fluid and tank contents. The comparison was not done on the base of the higher efficiency, but much attention is paid on the intensity of negative phenomena such as denser bottom currents. Numerical results of rectangular tank with no inlet baffle show that there is no sludge transportation layers, no strong bottom current and efficiency increase with inlet densimetric froud number decreasing. All of these phenomena cause rectangular tanks serve well than circular one in higher hydraulic and solids loading. Clearly, since there were not any experimental data for equivalent rectangular tank, then the written code is validated by solving some other bench marked problems in the considering field.

With the high demand of the market change, special CNC machine tools have to support fabrication of low volume production. These types of machine tools need special CAD/CAM systems in order to automatically generate NC program for the new components. In this research, a tool shape oriented feature based CAD/CAM system has been developed for a profile grinding machine with a dressing part. A new algorithm is implemented for automatic tool selection, suitable tools layout, and NC program generation. The implemented algorithms have been developed as a prototype software system using Object ARX and Visual C++ operation on the AutoCAD platform.