Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : design

Fabrication, Characterization and Modeling of Al2o3/Ni Functionally Graded Materials

Alaa Abdulhasan Atiyah

Engineering and Technology Journal, 2014, Volume 32, Issue 9, Pages 2286-2302

Functionally graded materials (FGMs), with ceramic and metallic constituents, are frequently used for tremendous high temperature applications. In this paper, six sets of FGMs samples were designed and fabricated using powder technology technique. All FGMs were sorted according to the conditions of sintering (i.e. temperature and time). The ceramic constituents were represented by (Al2O3) and the metallic constituents were represented by (Ni).It is found that as the sintering temperature and time increased, the apparent density was increased and porosity was reduced. (F-FGM, sintered at 1350°C for 3 hrs.) sample seems to impart high and slight linear graded microhardness across the layers without any obvious jumps throughout the thickness. The interfacial microhardness values were found very close to the bulk microhardness of adjacent layers. The reason behind such behavior is the minimum porosities and improved apparent density due to the efficient sintering practices (i.e. 1350°C and 3 hrs.) and uniform mutual diffusion of (Ni) and (Al2O3) particles across the layer interfaces. As the sintering time and temperature increase, the microstructure becomes much denser and the interfaces become more homogeneous that lead to eliminate the discontinuity in microstructure. A Finite element method throughout the COMSOL Multiphysicswas used extensively in estimation of temperature distribution through the thickness as well as residual stresses that induced as a result of high temperature loading of fabricated FGM. The model also shows aclear fluctuation of stresses along the thickness that imparts a development of stress concentration regions near the interfaces of layers, especially at the lower half region of FGM that was enriched by (Ni). Stresses clearly become normal variables with thickness at the upper half of FGM that enriched with (Al2O3).

A Numerical Model For Performance Prediction Of Dry Cooling Conditions Of Air Cooled Condensers In Thermal Power Plant Stations

Ali Hussain Tarrad

Engineering and Technology Journal, 2010, Volume 28, Issue 16, Pages 5271-5291

The present work represents theoretical treatment of dry cooling of the air cooled condensers applied in the power plants technology. A suggested model was built in a form of computer program to predict the effectiveness of the condenser showing the effect of inlet air temperature and its mass flow rate on the performance of the condenser. The model construction depends on the idea of using a row by row marching solution for energy balance for both stream sides.
The model has the ability to estimate the heat transfer coefficient, air temperature and other air physical properties distribution in the air flow direction from row to row. The results showed that using the cooling process of the air before entering the condenser improves the performance of the condenser and reduces the required area for a specified condensation load and steam loading. For fixed surface area of
the condenser, lowering the dry bulb temperature from (45) to (28) ºC at a constant wet bulb temperature and mass flow rate of the entering air can improve the condensation load up to (23 %) for the present investigated conditions.

Stress Evaluation of Low Pressure Steam Turbine Rotor bBlade and Design of Reduced Stress Blade

Arkan K. Husain Al-Taie

Engineering and Technology Journal, 2008, Volume 26, Issue 2, Pages 169-179

The low pressure steam turbine blade rows have a history of stress failure . They suffer from
tensile and bending stresses partly due to the centrifugal force as a result of high rotational
speeds and partly due to high pressure, temperature and speed steam loading. The centrifugal
force is one of the problems that face the designers of turbine blades especially the long ones.
The designer always aims at reducing these stresses. One way to do so is by the reduction of blade
mass. That is to make the blade of variable cross section stead in of straight. This paper presents
the method of reducing cross section. Analysis of such blade is also done as applied to the (P 23-
14A) steam blade.