Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Reacting”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Numerical modelling of turbulent flow in a combustion tunnel

A numerical technique is presented for the analysis of turbulent flow associated with combustion. The technique uses Chorin's random vortex method (rvm), an algorithm capable of tracing the action of elementary turbulent eddies and their cumulative effects without imposing any restriction upon their motion. In the past, the rvm has been used with success to treat nonreacting turbulent flows, revealing in particular the mechanics of large-scale flow patterns, the so-called coherent structures. Introduced here is a flame propagation algorithm, also developed by Chorin, in conjunction with volume sources modelling the mechanical effects of the exothermic process of combustion. As an illustration of its use, the technique is applied to flow in a combustion tunnel where the flame is stabilized by a back-facing step. Solutions for both nonreacting and reacting flow fields are obtained which satisfactorily describe the essential features of turbulent combustion in a lean propane-air mixture that were observed in the laboratory by means of high speed Schlieren photography.

Ghoniem, A. F.↗
NASA NTRS1982

Viscous-shock-layer heating analysis for the shuttle windward-symmetry plane with surface finite catalytic recombination rates

The paper demonstrates the capability of a reacting, two-dimensional viscous-shock-layer solution using the equivalent axisymmetric body concept to predict heating rates on the shuttle windward centerline for a wide range of altitudes. Results indicate that the nonequilibrium effects persist through most of the STS-2 entry heating pulse down to an altitude of about 50 km. When results are compared to those of the inviscid flowfield plus boundary layer solution of Scott (1980), agreement is fair to poor for nonequilibrium calculations, although very good for equilibrium calculations. A parametric study to demonstrate the effect of uncertainties in oxygen surface recombination rate for RCG coated HRSI on heating, indicates favorable results when a wall recombination rate of 100 cm/sec is used in the temperature range 1400-900 K.

Shinn, J. L.↗
NASA NTRS1982

Conversion of acoustic energy by lossless liners

The Blokhintzev acoustic energy equation is applied to a two-dimensional duct containing a uniform flow with a finite length lining. It is shown that the difference of the incident and outgoing acoustic energy differs in general from the energy dissipated in the liner, the difference being related to the displacements at the liner's edges. It is shown that in the case of a locally reacting lossless liner for frequencies below the first cut-off frequency and for low Mach number acoustic energy is generated if the flow and the incident sound wave are in the same direction and is absorbed if these two directions are opposite unless special edge conditions are met. Furthermore it is shown under the same conditions that the ratio of the reflection coefficient at finite flow velocity to the reflection coefficient at vanishing velocity is to first order in Mach number independent of the liner characteristics. A numerical calculation confirms these predictions at least for mass-like linear admittance.

Moehring, W.↗
NASA NTRS1982

Catalytic recombination and Space Shuttle heating

The measurement of surface temperatures on the thermal protection materials of the Space Shuttle Orbiter during reentry provides the basis for an important test of the prediction techniques developed over the past 10 years for reacting flows over reentry vehicles. The present investigation is concerned with comparisons of calculated temperatures with those measured during the second and third Space Shuttle missions. The general trends of the calculations compared favorably with the measurements. However, the calculations overpredicted the temperatures on the forward part of the windward centerline. Agreement was better farther aft, especially at the later times in the entry. The investigation has pointed out the significance of surface chemical reactions on the heat flux to the surface of the Orbiter and the need for further understanding.

Scott, C. D.↗
NASA NTRS1982

Formation of the thioester, N-acetyl, S-lactoylcysteine, by reaction of N-acetylcysteine with pyruvaldehyde in aqueous solution

N-acetylcysteine reacts efficiently with pyruvaldehyde (methylglyoxal) in aqueous solution (pH 7.0) in the presence of a weak base, like imidazole or phosphate, to give the thioester, N-acetyl, S-lactoylcysteine. Reactions of 100 mM N-acetylcysteine with 14 mM, 24 mM and 41 mM pyruvaldehyde yield, respectively, 86%, 76% and 59% N-acetyl, S-lactoylcysteine based on pyruvaldehyde. The decrease in the percent yield at higher pyruvaldehyde concentrations suggests that during its formation the thioester is not only consumed by hydrolysis, but also by reaction with some substance in the pyruvaldehyde preparation. Indeed, purified N-acetyl, S-lactoylcysteine disappears much more rapidly in the presence of pyruvaldehyde than in its absence. Presumably, N-acetyl, S-lactoylcysteine synthesis occurs by rearrangement of the hemithioacetal of N-acetylcysteine and pyruvaldehyde. The significance of this pathway of thioester formation to molecular evolution is discussed.

Weber, A. L.↗
NASA NTRS1982

High-temperature resins

The basic chemistry, cure processes, properties, and applications of high temperature resins known as polyimides are surveyed. Condensation aromatic polymides are prepared by reacting aromatic diamines with aromatic dianhydrides, aromatic tetracarboxylic acids, or with dialkyl esters of aromatic tetracarboxylic acids, depending on the intended end use. The first is for coatings or films while the latter two are more suitable for polyimide matrix resins. Prepreg solutions are made by dissolving reactants in an aprotic solvent, and advances in the addition of a diamine on the double bond and radical polymerization of the double bond are noted to have yielded a final cure product with void-free characteristics. Attention is given to properties of the Skybond, Pyralin, and NR-150B polyimide prepreg materials and characteristics of aging in the NP-150 polyimides. Finally, features of the NASA-developed PMR polyimides are reviewed.

Serafini, T. T.↗
NASA NTRS1983

Improving Hydrocarbon Separation In Gas Chromatography

Modified solica spheres enhance chromatographic separation. Commercially available silica spheres are modified by reacting them with molecules containing isocyante and isothiocyanate groups. Applications of surface derivatized spheres that result from reaction include analysis of samples prouced by atmospheric or soil probes.

Pollock, G. E.↗
NASA NTRS1983

Fire-Resistant Composites

Resin blend produces high-char-yield, low-smoke composites. Diglycidyl Ether of Bis-(4-Hydroxyphenyl)-Fluorene is prepared by reacting epichlorohydrin and sodium hydroxide with 9,9-bis(hydroxyphenyl) fluorene. End of reaction determined by gas or liquid chromatography, mass spectroscopy or infrared techniques. Used to manufacture printed circuit boards and panels for buildings, ships and aircraft.

Kourtides, D. A.↗
NASA NTRS1983

Solvent-Resistant Polysulfones

Polysulfones terminated with trimethylsilylethynyl, ethynyl, and phenylethynyl groups increased solvent resistance. Upon application of heat, with or without catalyst, end groups react to provide cross linking and chain extension. Result: temperature of polymer increased, more importantly, solvent resistance greatly improved. Solutions used conveniently for preparation of films, coatings, membranes, prepreg, and adhesive tapes.

Hergenrother, P. M.↗
NASA NTRS1984

Perfluoroalkylene-Ether Triazine Elastomers

New process yields product that resists heat and action of oxygen and water. Ring closing step, which gives elastomer its stability, imidoylamidine dinitrile reacts with perfluoroether acide, yielding prepolymer. Prepolymer then treated with ammonia and cured by heating to form polymer. Elastomers are highly resistant to heat, oxidation, and hydrolysis.

Rosser, R. W.↗
NASA NTRS1984

Acoustic Imaging of Combustion Noise

Elliposidal acoustic mirror used to measure sound emitted at discrete points in burning turbulent jets. Mirror deemphasizes sources close to target source and excludes sources far from target. At acoustic frequency of 20 kHz, mirror resolves sound from region 1.25 cm wide. Currently used by NASA for research on jet flames. Produces clearly identifiable and measurable variation of acoustic spectral intensities along length of flame. Utilized in variety of monitoring or control systems involving flames or other reacting flows.

Ramohalli, K. N.↗
NASA NTRS1984

Binder for Carbon-Fiber Coating

Insoluble, even coating formed by soaking in polyacrylic acid. Carbon fiber material prepared by soaking in solution of 20 percent polyacrylic acid in water. Material blotted and dried at 120 degrees C for at least 2 hours. Dried material reacted with boiling aqueous solution of calcium acetate. Treated material removed from boiling solution, blotted, dried at 120 degrees C, washed with distilled water, and dried again.

Dowler, W. L.↗
NASA NTRS1984

Solvent Extraction of Furfural From Biomass

Solvent-extraction method reduces energy required to remove furfural produced during acid hydrolysis of biomass. Acid hydrolysis performed in vessel containing both solvents and reacting ingredients. With intimate contact between solvents and aqueous hydrolyis liqour, furfural removed form liquor almost as fast as it forms.

Humphrey, M. F.↗
NASA NTRS1984

Ice as an Abrading Agent

Grit-blasting method makes unnecessary to disassemble equipment for cleaning. Stream of small, frozen pellets directed at assembly to be cleaned. Pellets consist of deionized-water ice, carbon dioxide ice, or another substance that does not react chemically with parts to be cleaned and leaves no residue. Method suited to cleaning titanium and parts that touch liquid oxygen.

Blow, R. K.↗
NASA NTRS1982

Development and application of the GIM code for the Cyber 203 computer

The GIM computer code for fluid dynamics research was developed. Enhancement of the computer code, implicit algorithm development, turbulence model implementation, chemistry model development, interactive input module coding and wing/body flowfield computation are described. The GIM quasi-parabolic code development was completed, and the code used to compute a number of example cases. Turbulence models, algebraic and differential equations, were added to the basic viscous code. An equilibrium reacting chemistry model and implicit finite difference scheme were also added. Development was completed on the interactive module for generating the input data for GIM. Solutions for inviscid hypersonic flow over a wing/body configuration are also presented.

Stainaker, J. F.↗
NASA NTRS1982

Vaporization thermodynamics of K2S and K2SO3

The vaporization reactions, vapor pressures, and thermodynamics of potassium sulfide and potassium sulfite were studied for purposes of providing fundamental data for the seed cycle in magnetohydrodynamic electric power generation. Rate of effusion studies, supported by tube furnace experiments, X-ray powder diffraction, mass spectrometry and appropriate chemical analyses and tests, revealed that potassium sulfite disproportionates at high temperatures to form potassium sulfide and potassium sulfate. Potassium sulfide was observed to vaporize incongruently, the initial vapors beng predominantly potassium atoms, with minor species being S2 and various K-S molecules. The ratio of K/S2 in the vapor is very large initially and decreases steadily with prolonged heating. Several materials were evaluated for purposes of containing K2S/K2SO3 at temperatures or = 800 C: Pt, Mo, W, quartz, machinable glass, BN, high density graphite, pyrolytic coated graphite, and alumina. Of these, only alumina was observed to be chemically inert to both K2S but reacted with K2SO3. The other materials were not suitable for either substance. Thermodynamic calculations based on measured vapor pressures and approximate free energy functions are described. Results from isothermal total mass loss experiments and from thermogravimetric experiments are also included.

Bennet, J. E.↗
NASA NTRS1982

An investigation of equilibrium concepts

A different approach to modeling of the thermochemistry of rocket engine combustion phenomena is presented. The methodology described is based on the hypothesis of a new variational principle applicable to compressible fluid mechanics. This hypothesis is extended to treat the thermochemical behavior of a reacting (equilibrium) gas in an open system.

Prozan, R. J.↗
NASA NTRS1983

Oxidation and formation of deposit precursors in hydrocarbon fuels

The oxidation of two jet turbine fuels and some pure hydrocarbons was studied at 130 C with and without the presence of small amounts of N-methyl pyrrole (NMP) or indene. Tendency to form solid-deposit precursors was studied by measuring soluble gum formation as well as dimer and trimer formation using field ionization mass spectrometry. Pure n-dodecane oxidized fastest and gave the smallest amount of procursors. An unstable fuel oil oxidized much slower but formed large amounts of precursors. Stable Jet A fuel oxidized slowest and gave little precursors. Indene either retarded or accelerated the oxidation of n-dodecane, depending on its concentration, but always caused more gum formation. The NMP greatly retarded n-dodecane oxidation but accelerated Jet A oxidation and greatly increased the latter's gum formation. In general, the additive reacted faster and formed most of the gum. Results are interpreted in terms of classical cooxidation theory. The effect of oxygen pressure on gum formation is also reported.

Mayo, F. R.↗