Computational Fluid Dynamics (CFD)
Samaneh Hajikhani; Foad Farhani; Hassan Ali Ozgoli; Seyed Mostafa Hosseinalipour
Abstract
Hot gas ingestion, due to pressure differences in the turbine’s main flow path, is a challenge for gas turbine designers. It reduces aerodynamic performance, increases temperature gradients and thermal stresses, and decreases disk life. Designers should predict the ingestion and use the precise ...
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Hot gas ingestion, due to pressure differences in the turbine’s main flow path, is a challenge for gas turbine designers. It reduces aerodynamic performance, increases temperature gradients and thermal stresses, and decreases disk life. Designers should predict the ingestion and use the precise design of the cooling system, balancing the cooling and sealing flow, to enable the turbine to operate at higher temperatures (TIT) and efficiency to save costs and reduce harmful effects on turbine components. This paper presents a numerical investigation of a 1.5-stage test rig to study the ingestion phenomenon. A numerical tool was developed to enhance the coefficients and constants of a rapid ingestion model in a zero-dimensional secondary air system (SAS) code applicable to power plant turbines, such as Frame 9. Comparisons of CFD and test results demonstrate satisfactory agreement. Combining CFD and experimental validation, a numerical effectiveness map for the selected test rig rim seal is presented. CFD results post-processing reveals that increased cooling flow rate increases the pressure within the wheelspace, reduces swirl in the core region, and improves seal effectiveness. The swirl ratio was highly sensitive to SAS flow, increasing by 90% with a 50% reduction in SAS flow at a dimensionless radius of 0.85. Analysis of flow vectors exiting the axial clearance rim seal indicates that increasing the SAS flow rate enhances the main gas path flow disturbances. Moreover, at a constant flow rate, an increase in the first wheelspace flow rate increases the effectiveness of the second wheelspace by approximately 33%.
Fluid Mechanics
Payam Rahim Masharei; Seyed Mostafa Hosseinalipour; Mohammad Javad moslemani
Abstract
Laminar mixing of glycerin in a chaotic mixer is carried by means of the blob deformation method. The mixer was a cylindrical vessel with two rotational blades which move along two different circular paths with a stepwise motion protocol. The flow visualization was performed by marking of the free surface ...
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Laminar mixing of glycerin in a chaotic mixer is carried by means of the blob deformation method. The mixer was a cylindrical vessel with two rotational blades which move along two different circular paths with a stepwise motion protocol. The flow visualization was performed by marking of the free surface of the flow with a tracer. The effects of controlling parameters such as rotational speed of blades, blades length, and rotational speed amplitude on mixing efficiency and time were analyzed by measuring of the area covered by the tracer. The results revealed that increasing rotational speed intensifies stretching and folding phenomenon, and consequently better mixing can be obtained. Also, the better condition in flow kinematic was provided to blend as stepwise motion protocol with wider amplitude adopted. A reduction in mixing time could be observed as the blades with longer length were used. In addition, it was also found that the promotion of mixing by rotational speed is more effective than that of two other parameters. The quantitative data and qualitative observations proved the potential of proposed chaotic mixer in wide range of industrial processes including chemical reaction and food processing in which laminar mixing is required.
