Área de Ingeniería Aeroespacial (aero)
http://hdl.handle.net/10016/19574
2019-09-23T18:48:34ZA collisionless plasma thruster plume expansion model
http://hdl.handle.net/10016/28875
A collisionless plasma thruster plume expansion model
Merino Martínez, Mario; Cichocki, Filippo; Ahedo Galilea, Eduardo Antonio
A two-fluid model of the unmagnetized, collisionless far region expansion of the plasma plume for gridded ion thrusters and Hall effect thrusters is presented. The model is integrated into two semi-analytical solutions valid in the hypersonic case. These solutions are discussed and compared against the results from the (exact) method of characteristics; the relative errors in density and velocity increase slowly axially and radially and are of the order of 10-2-10-3 in the cases studied. The plasma density, ion flux and ambipolar electric field are investigated. A sensitivity analysis of the problem parameters and initial conditions is carried out in order to characterize the far plume divergence angle in the range of interest for space electric propulsion. A qualitative discussion of the physics of the secondary plasma plume is also provided.
2015-04-30T00:00:00ZFully magnetized plasma flow in a magnetic nozzle
http://hdl.handle.net/10016/28873
Fully magnetized plasma flow in a magnetic nozzle
Merino Martínez, Mario; Ahedo Galilea, Eduardo Antonio
A model of the expansion of a plasma in a magnetic nozzle in the full magnetization limit is presented. The fully magnetized and the unmagnetized-ions limits are compared, recovering the whole range of variability in plasma properties, thrust, and plume efficiency, and revealing the differences in the physics of the two cases. The fully magnetized model is the natural limit of the general, 2D, two-fluid model of Ahedo and Merino [Phys. Plasmas 17, 073501 (2010)], and it is proposed as an analytical, conservative estimator of the propulsive figures of merit of partially magnetized plasma expansions in the near region of the magnetic nozzle.
2016-02-01T00:00:00ZAssessment of secondary bubble formation on a backward-facing step geometry
http://hdl.handle.net/10016/28872
Assessment of secondary bubble formation on a backward-facing step geometry
Juste, G.L.; Fajardo Peña, Pablo; Guijarro, A.
Flow visualization experiments and numerical simulations were performed on a narrow three-dimensional backward-facing step (BFS) flow with the main objective of characterizing the secondary bubble appearing at the top wall. The BFS has been widely studied because of its geometrical simplicity as well as its ability to reproduce most of the flow features appearing in many applications in which separation occurs. A BFS test rig with an expansion ratio of 2 and two aspect ratios (AR = 4 and AR = 8) was developed. Tests were performed at range of Reynolds numbers ranging from 50 to 1000; visualization experiments provided a qualitative description of secondary bubble and wall-jet flows. Large eddy simulations were carried out with two different codes for validation. Numerical solutions, once validated with experimental data from the literature, were used to acquire a deeper understanding of the experimental visualizations, to characterize the secondary bubble as a function of the flow variables (Reynolds and AR) and to analyze the effect of the secondary bubble on primary reattachment length. Finally, to decouple the sidewall effects due to the non-slip condition and the intrinsic flow three-dimensionality, numerical experiments with free-slip conditions over the sidewalls were computed. The main differences were as follows: When the non-slip condition is used, the secondary bubble appears at a Reynolds number of approximately 200, increases with the Reynolds number, and is limited to a small part of the span. This recirculation zone interacts with the wall-jets and causes the maximum and minimum lengths in the reattachment line of the primary recirculation. Under free slip conditions, the recirculation bubble appears at a higher Reynolds number and covers the entire channel span. Published by AIP Publishing.
2016-07-01T00:00:00ZCharacterization of diamagnetism inside an ECR thruster with a diamagnetic loop
http://hdl.handle.net/10016/28856
Characterization of diamagnetism inside an ECR thruster with a diamagnetic loop
Correyero Plaza, Sara; Merino Martínez, Mario; Elias, Paul-Quentin; Jarrige, J.; Packan, D.; Ahedo Galilea, Eduardo Antonio
The plasma-induced magnetic field in an electron cyclotron resonance plasma thruster is measured non-intrusively by means of a diamagnetic loop that encloses the plasma flow. The calibration process is described, and parasitic currents in the thruster walls and plasma oscillations are identified as the dominant sources of uncertainty. The integrated magnetic flux is seen to depend on the applied power and less significantly on the mass flow rate. The effect of the diamagnetic loop radius is also studied by testing two loops of different diameters. To estimate the perpendicular electron pressure in the plasma from the loop measurements, two plasma beam models, 1D and 2D, are used. While both models give similar results for the small loop, they differ significantly for the large loop, showing the relevance of 2D effects when a large diamagnetic loop is used.
2019-05-01T00:00:00Z