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Deng H.,Pennsylvania State University | Ozawa T.,Pennsylvania State University | Ozawa T.,Aerospace Research and Development Directorate | Levin D.A.,Pennsylvania State University
Journal of Thermophysics and Heat Transfer

Hypervelocity chemical reactions between SO2 and O are studied using the molecular dynamic/quasi-classicaltrajectory method for conditions relevant to the modeling of the rarefied atmosphere of Io, a moon of Jupiter. The implementation of both molecular dynamic/quasi-classical-trajectory and total-collisional-energy chemistry reaction models in direct simulation Monte Carlo is studied in a zero-dimensional time-dependent analysis and a twodimensional axisymmetric direct simulation Monte Carlo simulation to model a simple planetary flow condition. The molecular dynamic/quasi-classical- trajectory simulations were found to result in lower reaction rate constants and reaction probabilities than the total-collisional-energy model, and the vibrational favoring feature of theSO 2+ O← SO+ 2O reaction was revealed. The total collision cross section using the more general viscosity cross section was also obtained through the molecular dynamic/quasi-classical- trajectory simulations and was found to have a significantly different energy dependence compared with the original variable hard sphere cross section. For the twodimensional direct simulation Monte Carlo simulations it was found that the structure of the flow as well as the chemically formed sulfur oxide were different for the molecular dynamic/quasi-classical-trajectory and the totalcollisional-energy reaction probabilities and total cross sections. In addition, the reaction region was found to be highly nonequilibrium, which suggests that molecular dynamic/quasi-classical trajectory is a more suitable chemistry model for the simulation of Io's atmosphere. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. Source

Ozawa T.,Aerospace Research and Development Directorate | Li Z.,Pennsylvania State University | Sohn I.,Pennsylvania State University | Levin D.A.,Pennsylvania State University | Modest M.F.,University of California at Merced
48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

The current work implemented excited levels of atomic N and corresponding electron impact excitation/de-excitation and ionization processes in DSMC. Results show that when excitation models are included, the Starduct 68.9 km re-entry flow has an observable change in the ion number densities and electron temperature. Adding in the excited levels of atoms improves the degree of ionization by providing additional intermediate steps to ionization. The extra ionization reactions consume the electron energy and reduce the electron temperature. The DSMC results of number densities of excited levels are lower than the prediction of quasi steady state calculation. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. Source

Araki M.,Gunma University | Shiga S.,Gunma University | Shiga S.,Honda Corporation | Fukuda M.,Japan Aerospace Exploration Agency | And 4 more authors.
AIAA Journal

Noise reduction performance and feasibility of aerodynamic-tab (AT) jet noise suppressors in an actual hypersonic nozzle operating under takeoff conditions are investigated experimentally. Two kinds of AT nozzle geometries are applied, and it is shown that wedge ATs are more effective in terms of jet noise reduction. The AT nozzle position is varied every 1.0 mm in the y direction, and for wedge ATs, the AT position is defined as the center of gravity of their nozzle exit. It is considered that, due to the confinement of flow, distortion of the shock train by a large-scale structure in the shear layer, which contributes to shock associated acoustic radiation, is suppressed. It is considered that, near the shear layer, the effect of AT injection saturates since the AT working gas is injected out of the main jet (MJ) boundary and no longer contributes to the distortion of the MJ. Source

Iizuka T.,Tokyo Metroplitan University | Komatsu M.,Tokyo Metroplitan University | Tajika T.,Tokyo Metroplitan University | Aoyagi J.,Tokyo Metroplitan University | And 3 more authors.
48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2012

A low frequency (LF) plasma jet is proposed as an ignition system candidate for hydroxyl ammonium nitrate (HAN) based propellant, especially focused on SHP163, as substitution of conventional hydrazine. Plasma generation capability and power consumption characteristics were investigated as functions of frequency, applied voltage, and distance between high-voltage and ground electrodes. LF plasma jet in itself was generated at 5 Hz of frequency, 5 KV of applied voltage, and 5 mm of electrodes distance; and its power consumption was 16 W. At lower frequency and higher voltage, plasma generation capability was increased. Power consumption was decreased at lower frequency, lower applied voltage, and shorter electrode distance. At same applied voltage, lower power consumption was obtained at lower frequency and shorter electrodes distance. Additionally, LF plasma jet was applied to initiate SHP163. 1.1 × 10-2 g/s of mass reduction rate was obtained at 5 Hz of frequency and 5 KV of applied voltage, and its power consumption was 30 W. This result indicates that LF plasma jet has excellent possibility to be a good reaction initiation/enhancement system. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source

Suzuki T.,Japan Aerospace Exploration Agency | Suzuki T.,Aerospace Research and Development Directorate | Fujita K.,Japan Aerospace Exploration Agency | Fujita K.,Aerospace Research and Development Directorate | Sakai T.,Nagoya University
Journal of Thermophysics and Heat Transfer

A study has been conducted to show graphite nitridation in lower surface temperature regime. The heating tests are carried out in the 110 kW ICP wind tunnel installed in the Japan Aerospace Exploration Agency (JAXA) by using the graphite test piece. The amount of mass loss of the graphite test piece is obtained by comparing the weight between the before and after heating test. Obtained mass loss data are then correlated to the probability value of the nitridation reaction. To obtain the mass loss of the graphite test piece in the lower surface temperature regime, two different types of test pieces are developed in this study. One has a larger diameter than that used in the previous study, and the other is cooled by water. The test piece is sustained by a sleeve made from graphite for type A and from copper for type B. For type B, the back face of the graphite test piece is cooled by water during the testing. Based on the obtained probability values, a regression analysis is made, and the result is obtained in the Arrhenius form. Source

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