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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.

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At least 91 records · Page 5
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NASA NTRS1979

Development of stable low-electroosmotic mobility coatings

Long-time rinsings of the Z6040-methlycellulose coating used successfully on the ASTP MA=011 experiment indicate the permanency of this coating is inadequate for continuous flowing systems. Two approaches are described for developing coatings which are stable under continuous fluid movement and which exhibit finite and predictable electroosmotic mobility values while being effective on different types of surfaces, such as glass, plastics, and ceramic alumina, such as is currently used as the electrophoresis channel in the GE-SPAR-CPE apparatus. The surface charge modification of polystyrene latex, especially by protein absorption, to be used as model materials for ground-based electrophoresis experiments, and the preliminary work directed towards the seeded polymerization of large-particle-size monodisperse latexes in a microgravity environment are discussed.

Vanderhoff, J. W.↗
NASA NTRS1981

Advection fog formation in a polluted atmosphere

Large quantities of atmospheric aerosols with compositions SO4(2-), NO3(-) and NH4(+) have been detected in highly industrialized areas. The major portions of aerosol products are the results of energy-related fuel combustion. Both microphysical and macrophysical processes are considered in investigating the time-dependent evolution of the saturation spectra of condensation nuclei associated with both polluted and clean atmospheres during the time periods of advection fog formation. The results show that the condensation nuclei associated with a polluted atmosphere provide more favorable conditions than condensation nuclei associated with a clean atmosphere to produce dense advection fog, and that attaining a certain degree of supersaturation is not necessarily required for the formation of advection fog with condensation nuclei associated with a polluted atmosphere for monodisperse distribution.

Hung, R. J.↗
NASA NTRS1982

Performance of the continuous flow diffusion chambers

A brief comparative description is made of the chambers. Overall, comparisons for the various types of experiments - monodisperse, polydisperse and ambient aerosol - showed agreement among these chambers to within 15% in most cases. A careful analysis of the results indicated that a proper accounting of certain parameters would bring about much closer agreement among four of these instruments.

Hudson, J. G.↗
NASA NTRS1981

Comparison between two Aitken counters and with cloud condensation nuclei counters at the 1980 International CCN Workshop

The Pollak and the TSI 3020 counters agreed to within about 10% at concentrations below 1000 cu cm, whereas above that concentration, substantial systematic differences were observed. When the test aerosol was monodisperse and the CCN counters were operated at supersaturations that should nucleate all the aerosol, the Pollak counter read about 6% to 20% lower than the CCN counter in the concentration range from 250/cu cm to 1800/cu cm. The TSI 3020 read about 20% lower than the CCN counter at concentrations less than 1000/cu cm, and a factor of about two higher at concentrations above 1000/cu cm.

Rogers, C. F.↗
NASA NTRS1981

Comparing dry aerosol size measurements

Two instruments were used to size dry aerosols for the CCN experiments: the Naval Research Laboratory (NRL) instrument which uses an electrical mobility analyzer to separate the aerosol size fractions and a diffusion chamber to grow and count the particles and the University of Wyoming (WYO) aerosol monitoring system. Measurements from these two systems were usually found to be in agreement during the CCN Workshop. Two examples are presented to compare aerosol size distribution measurements of the two instruments: experiment 8 (monodisperse NaCl) and experiment 27 (polydisperse AgI). Differential (dN/dR) and cumulative plots are shown for both instruments for experiment 8 and experiment 27; also shown are Aitken particle measurements for comparison.

Rogers, D. C.↗
NASA NTRS1980

Advection fog formation and aerosols produced by combustion-originated air pollution

The way in which pollutants produced by the photochemical reaction of NO(X) and SO(X) affect the quality of the human environment through such phenomena as the formation of advection fog is considered. These pollutants provide the major source of condensation nuclei for the formation of fog in highways, airports and seaports. Results based on the monodisperse, multicomponent aerosol model show that: (1) condensation nuclei can grow and form a dense fog without the air having attained supersaturation; (2) the mass concentration range for NO(X) is one-third that of SO(X); and (3) the greater the mass concentration, the particle concentration, and the radius of condensation nuclei, the denser the fog that is formed.

Hung, R. J.↗
NASA NTRS1982

Studies with sample conductivity, insertion rates, and particle deflection in a continuous flow electrophoresis system

The continuous flow electrophoresis system makes electrophoresis possible in a free-flowing film of aqueous electrolyte medium. The sample continuously enters the electrolyte at the top of the chamber and is subjected to the action of a lateral dc field. This divides the sample into fractions since each component has a distinctive electrophoretic mobility. Tests were made using monodisperse polystyrene latex microspheres to determine optimum sample conductivity, insertion rates and optimum electric field applications as baseline data for future STS flight experiments. Optimum sample flow rates for the selected samples were determined to be approximately 26 micro-liters/min. Experiments with samples in deionized water yielded best results and voltages in the 20 V/cm to 30 V/cm range were optimum. Deflections of formaldehyde fixed turkey and bovine erythrocytes were determined using the continuous flow electrophoresis system. The effects of particle interactions on sample resolution and migration in the chamber was also evaluated.

Williams, G., Jr.↗
NASA NTRS1983

STS-6 sixth Space Shuttle mission. First flight of the Challenger

A prelaunch summary of the sixth Space Shuttle mission is provided. The Challenger orbiter; launching; uprated engines; lighter weight boosters; lightweight tank; external tank reduction; landing; the tracking and data relay satellite system (TDRSS), TDRS-1 deployment; the inertial upper stage (IUS), the spacewalk;electrophoresis, monodisperse latex reactor, night time/day time optical survey of lightning, and getaway special experiments are described.

Source record↗
NASA NTRS1983

Influence of multidroplet size distribution on icing collection efficiency

Calculation of collection efficiencies of two-dimensional airfoils for a monodispersed droplet icing cloud and a multidispersed droplet is carried out. Comparison is made with the experimental results reported in the NACA Technical Note series. The results of the study show considerably improved agreement with experiment when multidroplet size distributions are employed. The study then investigates the effect of collection efficiency on airborne particle droplet size sampling instruments. The biased effect introduced due to sampling from different collection volumes is predicted.

Chang, H.-P.↗
NASA NTRS1983

Impact and explosion crater ejecta, fragment size, and velocity

A model was developed for the mass distribution of fragments that are ejected at a given velocity for impact and explosion craters. The model is semi-empirical in nature and is derived from (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationship between maximum ejecta fragment size and crater diameter and an assumption on the functional form for the distribution of fragements ejected at a given velocity. This model implies that for planetary impacts into competent rock, the distribution of fragments ejected at a given velocity are nearly monodisperse, e.g., 20% of the mass of the ejecta at a given velocity contain fragments having a mass less than 0.1 times a mass of the largest fragment moving at that velocity. Using this model, the largest fragment that can be ejected from asteroids, the moon, Mars, and Earth is calculated as a function of crater diameter. In addition, the internal energy of ejecta versus ejecta velocity is found. The internal energy of fragments having velocities exceeding the escape velocity of the moon will exceed the energy required for incipient melting for solid silicates and thus, constrains the maximum ejected solid fragment size.

Okeefe, J. D.↗
NASA NTRS1984

Combustion characteristics in the transition region of liquid fuel sprays

A monodisperse aerosol generator was modified to study ignition requirements, flammability limits, and flame speeds in the transition region. An ignition system was developed and tested. The fabrication of an optical drop sizing system is nearly complete. Preliminary measurements of droplet size effects on the minimum ignition energy for n-heptane sprays performed. Parameteric studies of droplet size effects on minimum ignition energies of various fuels including alcohols are in progress.

Cernansky, N. P.↗
NASA NTRS1984

Structure of particle-laden jets - Measurements and predictions

Measurements of mean and fluctuating velocities of both phases as well as particle mass fluxes were completed in turbulent, particle-laden jets containing monodisperse particles with well-defined initial and boundary conditions. The new measurements were used to evaluate a stochastic separated flow model of the process which treated effects of interphase slip and turbulent dispersion using random-walk computations for particle motion. The continuous phase was treated using a modified k-epsilon model allowing for direct contributions of interphase transport to both mean and turbulence properties. The model performed reasonably well over the new data base, with all empirical parameters fixed from earlier work. In contrast, simplified models ignoring either interphase slip or turbulent dispersion yielded poor agreement with the measurements.

Shuen, J.-S.↗
NASA NTRS1984

A technique combining the visibility of a Doppler signal with the peak intensity of the pedestal to measure the size and velocity of droplets in a spray

A technique combining the visibility of a Doppler signal and the intensity of the scattered light to measure the size and velocity of particles is presented. It is shown that using only the visibility technique can lead to large errors under many conditions such as dense sprays. It is also shown that this error is considerably reduced and very high resolution is obtained by combining the visibility with the intensity of the scattered light. An instrument was developed using this new concept and measurements were performed in sprays of known characteristics. The results of monodispersed, bimodal and trimodal sprays are reported.

Hess, C. F.↗
NASA NTRS1984

Development of the phase/Doppler spray analyzer for liquid drop size and velocity characterizations

The present novel method for spray drop size and velocity measurement is analogous to a laser Doppler velocimeter, obtaining data from the spatial frequency of the interference fringe pattern produced by light scattering. Monodisperse droplet streams were used as a basic test of the theory, as well as of the susceptibility of the method to effects involved in actual application. Either beam intersection angle or detector spacing can be changed to achieve the same result. Polydispersed sprays were also measured.

Bachalo, W. D.↗
NASA NTRS1985

Calibrating Droplet Generator for Pressurized Testing Vessel

Device helps to aline laser for droplet-sizing interferometer. Monodispersing Droplet Generator creates uniformly sized droplets. Laser source and receiver of interferometer alined and focused on droplets. MDG mounted in high-pressure flange on tank. Line extensions pass through flange to outside. Flange allows MDG to operate at high injector back pressures used for tests.

Defever, G. J.↗
NASA NTRS1985

The structure of dilute combusting sprays

An experimental and theoretical study of drop processes in a turbulent flame is described. The experiments involved a monodisperse (105 and 180 micro m initial diameter) stream of methanol drops injected at the base of a turbulent methane-fueled diffusion flame burning in still air. The following measurements were made: mean and fluctuating phase velocities, mean drop number flux, drop-size distributions and mean gas-phase temperatures. Measurements were compared with predictions of two separated flow models: (1) deterministic separated flow, where drop-turbulence interactions are ignored; and (2) stochastic separated flow, where drop-turbulence interactions are considered using random-walk computations. The stochastic separated flow analysis yielded best agreement with measurements, since it provides for turbulent dispersion of drops which was important for present test conditions (and probably for most combusting sprays as well). Distinguishing the presence or absence of envelope flames around the drops, however, was relatively unimportant for present test conditions, since the drops spent most of their lifetime in fuel-rich regions of the flow where this distinction is irrelevant.

Shuen, J. S.↗
NASA NTRS1985

Research study of droplet sizing technology leading to the development of an advanced droplet sizing system

An instrument to measure the size and velocity of droplets was developed. The instrument uses one of two techniques, as appropriate. In the first technique two small laser beams of one color identify the center of a larger laser beam of a different color. This defines a region of almost uniform intensity where the light scattered by the individual droplets can be related to their size. The first technique uses the visibility of a Doppler burst and validates it against the peak intensity of the signal's pedestal. Results are presented for monodisperse, bimodal, trimodal, and polydisperse sprays produced by the Berglund-Liu droplet generator and a pressure nozzle. Size distributions of a given spray obtained using three different size ranges show excellent self-consistency in the overlapping region. Measurements of sprays of known characteristics exhibit errors in the order of 10%. The principles of operation and design criteria of the instrument are discussed in great detail.

Hess, C. F.↗