Advanced research and technology programs for advanced high-pressure oxygen-hydrogen rocket propulsion

A research and technology program for advanced high pressure, oxygen-hydrogen rocket propulsion technology is presently being pursued by the National Aeronautics and Space Administration (NASA) to establish the basic discipline technologies, develop the analytical tools, and establish the data base necessary for an orderly evolution of the staged combustion reusable rocket engine. The need for the program is based on the premise that the USA will depend on the Shuttle and its derivative versions as its principal Earth-to-orbit transportation system for the next 20 to 30 yr. The program is focused in three principal areas of enhancement: (1) life extension, (2) performance, and (3) operations and diagnosis. Within the technological disciplines the efforts include: rotordynamics, structural dynamics, fluid and gas dynamics, materials fatigue/fracture/life, turbomachinery fluid mechanics, ignition/combustion processes, manufacturing/producibility/nondestructive evaluation methods and materials development/evaluation. An overview of the Advanced High Pressure Oxygen-Hydrogen Rocket Propulsion Technology Program Structure and Working Groups objectives are presented with highlights of several significant achievements

The classical multicomponent nucleation theory for cavitation in water with dissolved gases

The Classical Nucleation Theory (CNT) in its multicomponent form is presented as a reliable tool for the investigation of homogeneous nucleation in cavitation processes in aqueous systems. Several cases are considered, starting form the most simple case of a void cavity emerging at negative pressure, then treating the case of a bubble composed of water vapor only, and finally investigating the influence of various gases dissolved in water on the nucleation rate and the composition of the critical cluster. Aqueous systems related to cavitation in hydraulic machinery and to cavitation in carbonated beverages are discussed.http://deepblue.lib.umich.edu/bitstream/2027.42/84298/1/CAV2009-final120.pd

Cavitation processes in binary systems – the effect of a dissolved gas on the nucleation rate described by the classical nucleation theory

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.The Classical Nucleation Theory (CNT) is applied to nucleation in cavitation processes in binary mixtures of a liquid component and a dissolved gas component. The multi-component form of the CNT allows to study the influence of the dissolved gas concentration on the resulting nucleation rate. Four binary mixtures are studied, diethylether – nitrogen, propane – carbon dioxide, isobutane – carbon dioxide, and chlorodifluoromethane – carbon dioxide, whose experimental nucleation rates are available in the literature. The nucleation rates and their dependence on concentration of the dissolved gas calculated according to the CNT show good agreement with the experimental data.pm201

Interaction between the jet and wakes as a method for passive control of plane impinging jets

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.A planar impinging air jet was experimentally investigated, with passive flow control as means of enhancement of impingement heat/mass transfer. The control was achieved by means of an array of small cylinders, fixed at the nozzle lips so as to bridge the nozzle exit gap. Experiments used mainly the naphthalene sublimation technique, with the resultant local mass transfer coefficient converted to prediction of the corresponding heat transfer by means of the heat/mass transfer analogy. Also measured were the local velocities. The experiment revealed the expected spatially periodical character of the flow field and heat/mass transfer distributions. To quantify the heat/mass transfer effects, three procedures are proposed. Compared with the standard planar impinging jet at the optimal nozzle-to-wall distance, the enhancement of the average heat/mass transfer was demonstrated to reach up to 8%.pm201

The characteristic thickness of polymer electrolyte membrane and the efficiency of fuel cell

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.We propose a simple diffusion model of a PEM fuel cell and perform its thermodynamic analysis. Our description is based on a set of two mass balance equations involving water and proton transport through the membrane coupled with two reaction equations describing the electrochemical reactions at the electrodes. Equations for the water and proton flux densities are constructed in a linearized form suitable for the analysis from the point of view of irreversible thermodynamics. In terms of our simplified model, relations for the characteristic thickness of a PEM membrane is derived, and the maximum efficiency of a fuel cell is evaluated, both as functions of the transport properties of the PEM material

Infrared spectroscopy study of the in-plane response of YBa2Cu3O6.6 in magnetic fields up to 30 Tesla

With Terahertz and Infrared spectroscopy we studied the in-plane response of an underdoped YBa2Cu3O6.6 single crystal with Tc=58(1) K in high magnetic fields up to B=30 Tesla applied along the c-axis. Our goal was to investigate the field-induced suppression of superconductivity and to observe the signatures of the three dimensional (3d) incommensurate copper charge density wave (Cu-CDW) which was previously shown to develop at such high magnetic fields. Our study confirms that a B-field in excess of 20 Tesla gives rise to a full suppression of the macroscopic response of the superconducting condensate. However, it reveals surprisingly weak signatures of the 3d Cu-CDW at high magnetic fields. At 30 Tesla there is only a weak reduction of the spectral weight of the Drude-response (by about 3%) that is accompanied by an enhancement of two narrow electronic modes around 90 and 240 cm-1, that are interpreted in terms of pinned phase modes of the CDW along the a- and b-direction, respectively, and of the so-called mid-infrared (MIR) band. The pinned phased modes and the MIR band are strong features already without magnetic field which suggests that prominent but short-ranged and slowly fluctuating (compared to the picosecond IR-time scale) CDW correlations exist all along, i.e., even at zero magnetic field.Comment: 12 pages, 3 figure