Haifa El-Sadi

Simulation of complex liquids in micropump

Abstract Complex liquids can be encountered in many applications of microdevices. In the present study, the performance of microscrew pump using complex liquid is investigated numerically. The microscrew pump operation depends on the surface sweep forces. It consists of a screw placed inside a microchannel. When the screw rotates, a net force is transferred to the fluid due to differential pressure on the depth of the thread and pressure gradient along the screw axis, thus causing the fluid to displace. Three-dimensional complex liquid simulations of micropump were performed. The effect of screw pitch, thread, Reynolds number and pump load on the micropump performance has been studied. The simulations of complex liquids indicate that the highest bulk velocity is achieved with high thread depth at low Reynolds number. However, effective pumping is accomplished at low Reynolds number, high pressure load and high thread depths.

CFD Study of HPT Blade Cooling Flow Supply Systems

This work summarizes the results of the CFD analyses to investigate the effect of the geometrical parameters for a typical coverplate-disk cavity and blade broach system also known as the blade cooling flow supply system. A turbofan high pressure turbine was used as the test vehicle for this investigation. The main objective was to explore potential improvements in engine SFC (aerodynamic performance) by reducing the parasitic work while minimizing the impact on the factors that affect the durability of the turbine blades; feed pressure, temperature, and mass flow. Various tangential on-board injection (TOBI) blade cooling flow supply systems were considered: i) Phase 1 compared the radial TOBI and axial TOBI, ii) Phase 2 compared coverplate-disk cavity shapes, and iii) Phase 3 compared blade broach shapes. The in-house CFD code NS3D was used for the analyses. Compared to the radial TOBI, the axial TOBI has a positive impact on the parasitic work (lower) and blade feed temperature (lower) while it has a negative impact on the blade feed pressure (lower). Further, the coverplate-disk cavity shapes investigated had no significant impact on the parasitic work, blade feed pressure, and blade feed temperature. The CFD solutions show that the major portion of the parasitic work is due to flow turning at the broach entrance. Finally, reducing the blade broach cross-section by sloping up the lower wall has no significant impact on the parasitic work and blade feed temperature but a negative impact on the blade feed pressure and mass flow. Modifying the broach pressure side wall shape is preferred among the blade broach geometries investigated. Future work to improve the CFD analysis consists of performing unsteady analyses to better capture the vortex flow in the blade broach, and including upstream stationary components with either iterative boundary condition modeling or an unsteady multi-stage approach.Copyright

Modeling of supercritical fluid extraction of phenanthrene from clayey soil

The supercritical fluid (SFC) extraction efficiency of phenanthrene from clayey soils was modeled. The model accounts for effective diffusion of the phenanthrene in the solid pores, axial dispersion in the fluid phase, and external mass transfer to the fluid phase from the particle surface. This model, involving partial differential equations, was solved using the finite difference. The model showed the relationship between diffusivity, mass transfer coefficient, and properties of porous media (clay texture). The porous media analysis was performed with a microscope and by an image analysis. The proposed model compared well with the experimental data available in the literature.

Simulation of coating -visco-elastic liquid in the Micro-nip of metering size press

For a set of operating conditions and coating color formulations, undesirable phenomena like color spitting and coating ribs may be triggered in the Micro-nip during the coating process. Therefore, our interest in this work focus on another parameter affect on the undesirable phenomena as the vortices in the Micro-nip. The problem deals with the flow through the Micro-nip of metering size press. The flow enters and exits at a tangential velocity of 20 m/s between two rollers with diameter 80 cm and 60 mum apart. In the upper and bottom part of the domain the angular velocity is 314 rad /s. It has one sub-domain. Previous studies focus on the Micro-nip without considering the inertia and the viscoelasticity of the material. Roll coating is a technique commonly used in the coating industry to meter a thin fluid film on a moving substrate. During the film formation, the fluid is subjected to very high shear and extensional rates over a very short period of time. The fluid domain changes as a function of the hydrodynamic pressure within the nip as a result of the deformable cover usually used on one of the rolls. The free surface also adds more complexity to the flow due to the force equilibrium in the fluid gas interface. Last of all, the rheological behavior of the coating fluid is usually non-Newtonian, so the metering flow hydrodynamics is finally very difficult to describe. It is concluded that the normal forces of micro-nip increases with increasing the inhibitors. Therefore, it affects on the smoothness and creates defects. On the other hand, it can be concluded that the creation of big vortex in the middle of micro-nip affects on the coating liquid behavior.