Área de Ingeniería Aeroespacial (aero)http://hdl.handle.net/10016/195742019-09-16T23:09:57Z2019-09-16T23:09:57ZDevelopment and validation of a radial variable geometry turbine model for transient pulsating flow applicationsGalindo, J.Tiseira, A.Fajardo Peña, PabloGarcia-Cuevas, L. M.http://hdl.handle.net/10016/288202019-09-16T15:05:17Z2014-09-01T00:00:00ZDevelopment and validation of a radial variable geometry turbine model for transient pulsating flow applications
Galindo, J.; Tiseira, A.; Fajardo Peña, Pablo; Garcia-Cuevas, L. M.
This paper presents the development and validation of a one-dimensional radial turbine model able to be used in automotive turbocharger simulations. The model has been validated using results from a numerical 3D CFD simulation of stationary and pulsating flow in a variable geometry radial turbine. As the CFD analysis showed, the main non-quasi-steady behavior of the turbine is due to the volute geometry, so special care was taken in order to properly model it while maintaining low computational costs. The flow in the volute has been decomposed in its radial and azimuthal direction. The azimuthal flow corresponds to the flow moving along the volute, while the radial flow is computed by coupling its flow with a stator model. Although the stator caused fewer accumulation effects than the volute, a small accumulation model has been used for it, which also allows to compute the evolution of the flow inside the turbine with lower costs. The flow in the moving rotor can be considered quasi-steady, so a zero-dimensional model for the rotor has been developed. Several losses models where implemented for both the stator and the rotor. The results show good agreement with the CFD computations.
2014-09-01T00:00:00ZElectron cooling and finite potential drop in a magnetized plasma expansionMartínez Sánchez, ManuelNavarro Cavallé, JaumeAhedo Galilea, Eduardo Antoniohttp://hdl.handle.net/10016/288092019-09-14T00:02:37Z2015-05-05T00:00:00ZElectron cooling and finite potential drop in a magnetized plasma expansion
Martínez Sánchez, Manuel; Navarro Cavallé, Jaume; Ahedo Galilea, Eduardo Antonio
The steady, collisionless, slender flow of a magnetized plasma into a surrounding vacuum is considered. The ion component is modeled as mono-energetic, while electrons are assumed Maxwellian upstream. The magnetic field has a convergent-divergent geometry, and attention is restricted to its paraxial region, so that 2D and drift effects are ignored. By using the conservation of energy and magnetic moment of particles and the quasi-neutrality condition, the ambipolar electric field and the distribution functions of both species are calculated self-consistently, paying attention to the existence of effective potential barriers associated to magnetic mirroring. The solution is used to find the total potential drop for a set of upstream conditions, plus the axial evolution of various moments of interest (density, temperatures, and heat fluxes). The results illuminate the behavior of magnetic nozzles, plasma jets, and other configurations of interest, showing, in particular, in the divergent plasma the collisionless cooling of electrons, and the generation of collisionless electron heat fluxes.
2015-05-05T00:00:00ZParticle modeling of radial electron dynamics in a controlled discharge of a Hall thrusterDomínguez Vázquez, AdriánAhedo Galilea, Eduardo AntonioTaccogna, Fhttp://hdl.handle.net/10016/287572019-09-11T09:54:03Z2018-06-01T00:00:00ZParticle modeling of radial electron dynamics in a controlled discharge of a Hall thruster
Domínguez Vázquez, Adrián; Ahedo Galilea, Eduardo Antonio; Taccogna, F
An improved radial particle-in-cell model of an annular Hall effect thruster discharge with secondary-electron emission from the walls and a radial magnetic field is presented. New algorithms are implemented: first, to adjust the mean neutral density to the desired mean plasma density; second, to avoid the refreshing of axially accelerated particles; and third, to correctly weigh low-density populations (such as secondary electrons). The high-energy tails of the velocity distribution functions of primary and secondary electrons from each wall are largely depleted, leading to temperature anisotropies for each species. The secondary-electron populations are found to be partially recollected by the walls and partially transferred to the primary population. The replenishment ratio of the primary high-energy tail is determined based on the sheath potential fall. Significant asymmetries at the inner and outer walls are found for the collected currents, the mean impact energy, and the wall and sheath potentials. Radial profiles in the plasma bulk are asymmetric too, due to a combination of the geometric expansion, the magnetic mirror effect, and the centrifugal force (emanating from the E x B drift). The temperature anisotropy and non-uniformity, and the centrifugal force modify the classical Boltzmann relation on electrons along the magnetic lines.
Special issue on plasma-surface Interactions
2018-06-01T00:00:00ZDevelopment of a segregated compressible flow solver for turbomachinery simulationsBenajes, JesúsGalindo, JoséFajardo Peña, PabloNavarro, Robertohttp://hdl.handle.net/10016/287412019-09-03T00:03:50Z2014-10-01T00:00:00ZDevelopment of a segregated compressible flow solver for turbomachinery simulations
Benajes, Jesús; Galindo, José; Fajardo Peña, Pablo; Navarro, Roberto
A steady multiple reference frame segregated compressible solver and an unsteady sliding mesh one are developed using OpenFOAM® to simulate turbomachinery. For each of the two solvers, governing equations, numerical approach and solver structure are explained. Pressure and energy equation are implemented so as to obtain the best numerical properties, such as the ability to use large time-steps. Sod shock tube test case is used to assess the prediction of compressible phenomena by the transient scheme, which shows proper resolution of compressible waves. Both solvers are used to simulate a turbocharger turbine, comparing their solutions to corresponding ones using ANSYS® Fluent® as a means of validation. The multiple reference frame solver global results quantitatively differ from those computed using ANSYS Fluent, although predicted flow features match. The solution obtained by the sliding mesh solver presents better agreement compared to ANSYS Fluent one.
2014-10-01T00:00:00Z