Al-Qadisiyah Journal for Engineering Sciences

Abstract Convergent-Divergent nozzle has many applications especially in steam turbine. The aim of this work is to see the effect of varying inlet pressure on steam behavior through the C-D nozzle. This was done experimentally and numerically. In the experimental part, a C-D nozzle was designed and fabricated in a test section. Steam was fed from boiler at range of (0.69-0.36) bar at saturation temperature for each pressure. Shadowgraph optical method was used to see the formation of shock waves and condensation zone. In the numerical part, the nozzle was simulated using FLUENT under ANSYS code 15.0. In the experimental results, it was found that the most important influence of rapid condensation on the pressure distribution is occurred downstream the through area, when the flow in the divergent part is termed supersonic the heat release causes a pressure rise in the zone of rapid condensation. Shock wave appears in the divergent part due to over-expansion. Each of condensation zone and shock wave were showed by using shadowgraph optical method. In the numerical approach, droplet growth rate contour are presented. The maximum droplet growth rate is (1020 micron /sec) and occurred downstream the throat area. The comparison of experimental and numerical results show good agreement

Abstract The present investigation was carried out to study the possibility of using waste glass of size up to 5mm as a fine aggregate in concrete and mortar. The waste glass was used as a partial weight replacement of sand with percentages of 10, 20, 30 and 40 %. The results have indicated that increasing the fractions of sand replacement by waste glass leads to reduce the compressive and tensile strength for both mortar and concrete. Up to 20 % replacement, the 28 days compressive strength of concrete and mortar is about 92 and 95 percent from the reference strengths, respectively. Also, it was found that the expansion of mortar specimens increase with increasing the waste glass content in the mix. At 20 % of sand replacement by waste glass, the expansion is slightly higher than that for the control specimens.

Abstract The present study aims aimed to investigate factors affecting the soundness of Portland cement (in terms of autoclave expansion test). These factors are C3S, C2S, C3A, C4AF, fineness (in terms of specific surface measured by Blaine method), the minor oxides MgO, free CaO, SO3, and the variables obtained from the chemical analysis of cement like silica modulus (SM), alumina ratio (AR), loss on ignition (LOI), insoluble residue (IR), and lime saturation factor (LSF). The autoclave expansion prediction models were built by using multiple linear regression analysis and based on (40) different cement samples taken from (7) different Iraqi cement factories, Indian cement, and Kuwaiti cement. (29) of the samples were ordinary Portland cement while the other (11) samples were sulphate resisting Portland cement. It was found that the multiple linear regression is very suitable for predicting the autoclave expansion of Portland cement. It was also found that the increase of fineness of cement, LSF, and LOI decreases the autoclave expansion, while the increase in the other factors increases the autoclave expansion. The correlation coefficients of the proposed models were (0.71002 and 0.98338) for the first model, (0.84366 and 0.98789) for the second model, and (0.85593 and 0.98872) for the third model, with and without intercept respectively