Investigation on the Effects of Field Emission Plasma on the Performance of a Micro-Combustor

2021 ◽  
Author(s):  
Maria Grazia De Giorgi ◽  
Giacomo Cinieri ◽  
Donato Fontanarosa ◽  
Antonio Ficarella
Keyword(s):  
Field Emission ◽  
Performance Enhancement ◽  
Plasma Chemistry ◽  
Plasma Discharge ◽  
Second Order ◽  
The Body ◽  
Coupling Scheme ◽  
Dbd Plasma ◽  
Reference Case ◽  
Plasma Actuation

Abstract This work provides a numerical investigation of the effects of micro field emission dielectric barrier discharge (FE-DBD) plasma actuation on the performance of a micro-combustion system composed of two straights perpendicular microchannels for propellant injection followed by a rectangular micro-combustion chamber in a T-shaped planar configuration. Concerning the modeling, a novel two-step approach has been developed. The first step consisted in solving the chemistry of a sinusoidal plasma discharge in a zero-dimensional modeling. To this purpose, the collisional processes involved in the plasma discharge have been solved using a Boltzmann-equation approach, which permits to predict the electron impact reactions based on a two-temperature model. Furthermore, the zero-dimensional hypothesis used for computations assumed uniform plasma during the overall discharge duration. Concerning the plasma chemistry, excitation and de-excitation processes, electron-ion recombination reactions, attachment and detachment for electrons and neutral species have been considered in order to improve the prediction accuracy. This step allowed to quantify the body force, the heat source and the propellant composition modification induced by sinusoidal plasma actuation operating at 10 MHz of repetition rate, atmospheric pressure and 300 K temperature. Therefore, the predicted cycle averaged plasma effects have been used in 2D steady-state simulations of the laminar, compressible, reactive micro flow, based on a continuum Navier-Stokes approach. SIMPLE pressure-velocity coupling scheme was chosen with a second order pressure spatial discretization. A second-order upwind scheme was applied. The hydrogen-oxygen combustion has been modeled using the Connaire mechanism. The comparison between the results of the reference case without plasma actuation, and those retrieved in presence of plasma actuation at different supplied voltages, highlighted the performance enhancement due to plasma discharge.

Analysis of the First Order and Slowly Varying Motions of an Axisymmetric Floating Body in Bichromatic Waves

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
João Pessoa ◽  
Nuno Fonseca ◽  
C. Guedes Soares
Keyword(s):  
Vertical Cylinder ◽  
Vertical Axis ◽  
Second Order ◽  
The Body ◽  
Floating Body ◽  
Drift Motion ◽  
First Order ◽  
Motion Responses ◽  
Simple Geometry ◽  
Good Agreement

The paper presents an experimental and numerical investigation on the motions of a floating body of simple geometry subjected to harmonic and biharmonic waves. The experiments were carried out in three different water depths representing shallow and deep water. The body is axisymmetric about the vertical axis, like a vertical cylinder with a rounded bottom, and it is kept in place with a soft mooring system. The experimental results include the first order motion responses, the steady drift motion offset in regular waves and the slowly varying motions due to second order interaction in biharmonic waves. The hydrodynamic problem is solved numerically with a second order boundary element method. The results show a good agreement of the numerical calculations with the experiments.

Drift Forces on a Floating Body of Simple Geometry Due to Second Order Interactions Between Pairs of Harmonics With Different Frequencies

2009 ◽  
Author(s):  
Joa˜o Pessoa ◽  
Nuno Fonseca ◽  
C. Guedes Soares
Keyword(s):  
Vertical Cylinder ◽  
Vertical Axis ◽  
Second Order ◽  
The Body ◽  
Floating Body ◽  
Order Problem ◽  
Simple Geometry ◽  
The Mean ◽  
Order Quantities ◽  
Drift Forces

The paper presents an investigation of the slowly varying second order drift forces on a floating body of simple geometry. The body is axis-symmetric about the vertical axis, like a vertical cylinder with a rounded bottom and a ratio of diameter to draft of 3.25. The hydrodynamic problem is solved with a second order boundary element method. The second order problem is due to interactions between pairs of incident harmonic waves with different frequencies, therefore the calculations are carried out for several difference frequencies with the mean frequency covering the whole frequency range of interest. Results include the surge drift force and pitch drift moment. The results are presented in several stages in order to assess the influence of different phenomena contributing to the global second order responses. Firstly the body is restrained and secondly it is free to move at the wave frequency. The second order results include the contribution associated with quadratic products of first order quantities, the total second order force, and the contribution associated to the free surface forcing.

Ozone Production With Plasma Discharge: Comparisons Between Activated Air and Activated Fuel/Air Mixture

2021 ◽  
Author(s):  
Ghazanfar Mehdi ◽  
Maria Grazia De Giorgi ◽  
Donato Fontanarosa ◽  
Sara Bonuso ◽  
Antonio Ficarella
Keyword(s):  
Experimental Data ◽  
Plasma Chemistry ◽  
Kinetic Scheme ◽  
Plasma Discharge ◽  
Chemical Kinetic ◽  
Ozone Production ◽  
Air Plasma ◽  
Flammability Limits ◽  
Combustion Enhancement ◽  
The Impact

Abstract This study focused on the comparative analysis about the production of ozone and active radicals in presence of nanopulsed plasma discharge on air and on fuel/air mixture to investigate its effect on combustion enhancement. This analysis is based on numerical modeling of air and methane/air plasma discharge with different repetition rates (100 Hz, 1000 Hz and 10000 Hz). To this purpose, a two-step approach has been proposed based on two different chemistry solvers: a 0-D plasma chemistry solver (ZDPlasKin toolbox) and a combustion chemistry solver (CHEMKIN software suite). Consequently, a comprehensive chemical kinetic scheme was generated including both plasma excitation reactions and gas phase reactions. Validation of air and methane/air mechanisms was performed with experimental data. Kinetic models of both air and methane/air provides good fitting with experimental data of O atom generation and decay process. ZDPlasKin results were introduced in CHEMKIN in order to analyze combustion enhancement. It was found that the concentrations of O3 and O atom in air are higher than the methane/air activation. However, during the air activation peak concentration of ozone was significantly increased with repetition rates and maximum was observed at 10000 Hz. Furthermore, ignition timings and flammability limits were also improved with air and methane/air activation but the impact of methane/air activation was comparatively higher.

Plasma actuation effect on a NACA 4412 airfoil

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Burak Karadag ◽  
Cem Kolbakir ◽  
Ahmet Selim Durna
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Open Loop ◽  
Electrode Configuration ◽  
Small Scale ◽  
Low Velocity ◽  
Dbd Plasma ◽  
Content Type ◽  
Plasma Actuation ◽  
Electric Wind

Purpose This paper aims to investigate the effects of a dielectric barrier discharge (DBD) plasma actuator (PA) qualitatively on aerodynamic characteristics of a 3 D-printed NACA 4412 airfoil model. Design/methodology/approach Airflow visualization study was performed at a Reynolds number of 35,000 in a small-scale open-loop wind tunnel. The effect of plasma actuation on flow separation was compared for the DBD PA with four different electrode configurations at 10°, 20° and 30° angles of attack. Findings Plasma activation may delay the onset of flow separation up to 6° and decreases the boundary layer thickness. The effects of plasma diminish as the angle of attack increases. Streamwise electrode configuration, in which electric wind is produced in a direction perpendicular to the freestream, is more effective in the reattachment of the airflow compared to the spanwise electrode configuration, in which the electric wind and the free stream are in the same direction. Practical implications The Reynolds number is much smaller than that in cruise aircraft conditions; however, the results are promising for low-velocity subsonic airflows such as improving control capabilities of unmanned aerial vehicles. Originality/value Superior efficacy of spanwise-generated electric wind over streamwise-generated one is demonstrated at a very low Reynolds number. The results in the plasma aerodynamics literature can be reproduced using ultra-low-cost off-the-shelf components. This is important because high voltage power amplifiers that are frequently encountered in the literature may be prohibitively expensive especially for resource-limited university aerodynamics laboratories.

Systematically Reviewing the Efficacy of Mindfulness-Based Interventions for Enhanced Athletic Performance

2015 ◽  
Vol 9 (3) ◽  
pp. 232-262 ◽  
Author(s):  
Ryan Sappington ◽  
Kathryn Longshore
Keyword(s):  
Sport Psychology ◽  
Performance Enhancement ◽  
Assessment Tool ◽  
Skills Training ◽  
Sport Performance ◽  
The Body ◽  
Psychological Skills ◽  
Psychological Skills Training ◽  
Quality Of Research

The field of applied sport psychology has traditionally grounded its performance enhancement techniques in the cognitive-behavioral elements of psychological skills training. These interventions typically advocate for controlling one’s cognitive and emotional processes during performance. Mindfulness-based approaches, on the other hand, have recently been introduced and employed more frequently in an effort to encourage athletes to adopt a nonjudgmental acceptance of all thoughts and emotions. Like many applied interventions in sport psychology, however, the body of literature supporting the efficacy of mindfulness-based approaches for performance enhancement is limited, and few efforts have been made to draw evidence-based conclusions from the existing research. The current paper had the purpose of systematically reviewing research on mindfulness-based interventions with athletes to assess (a) the efficacy of these approaches in enhancing sport performance and (b) the methodological quality of research conducted thus far. A comprehensive search of relevant databases, including peer-reviewed and gray literature, yielded 19 total trials (six case studies, two qualitative studies, seven nonrandomized trials, and four randomized trials) in accordance with the inclusion criteria. An assessment tool was used to score studies on the quality of research methodology. While a review of this literature yielded preliminary support for the efficacy of mindfulness-based performance enhancement strategies, the body of research also shows a need for more methodologically rigorous trials.

Rotor Performance Enhancement Using Pulsed Plasma Actuation

AIAA Journal ◽  
2021 ◽  
pp. 1-6
Author(s):  
Dor Polonsky ◽  
David Keisar ◽  
David Greenblatt
Keyword(s):  
Performance Enhancement ◽  
Pulsed Plasma ◽  
Plasma Actuation

Series Active Variable Geometry Suspension Robust Control Based on Full-Vehicle Dynamics

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Cheng Cheng ◽  
Simos A. Evangelou
Keyword(s):  
High Performance ◽  
Performance Enhancement ◽  
Ride Comfort ◽  
The Body ◽  
Control Technique ◽  
Variable Geometry ◽  
Physical Constraints ◽  
Car Model ◽  
Time Domains ◽  
Vertical Accelerations

This paper demonstrates the ride comfort and road holding performance enhancement of the new road vehicle series active variable geometry suspension (SAVGS) concept using an H∞ control technique. In contrast with the previously reported work that considered simpler quarter-car models, the present work designs and evaluates control systems using full-car dynamics thereby taking into account the coupled responses from the four independently actuated corners of the vehicle. Thus, the study utilizes a nonlinear full-car model that represents accurately the dynamics and geometry of a high performance car with the new double wishbone active suspension concept. The robust H∞ control design exploits the linearized dynamics of the nonlinear model at a trim state, and it is formulated as a disturbance rejection problem that aims to reduce the body vertical accelerations and tire deflections while guaranteeing operation inside the existing physical constraints. The proposed controller is installed on the nonlinear full-car model, and its performance is examined in the frequency and time domains for various operating maneuvers, with respect to the conventional passive suspension and the previously designed SAVGS H∞ control schemes with simpler vehicle models.

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