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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Microphysical fundamentals governing cirrus cloud growth: Modeling studies

For application to Global Climate Models, large scale numerical models of cirrus cloud formation and maintenance need to be refined to more reliably simulate the effects and feedbacks of high level clouds. A key aspect is how ice crystal growth is initiated in cirrus, which has started a cloud microphysical controversy between camps either believing that heterogeneous or homogeneous drop freezing is predominantly responsible for cold cirrus ice crystal nucleation. In view of convincing evidence for the existence of highly supercooled cloud droplets in the middle and upper troposphere, however, it is concluded that active ice nuclei are rather scarce at cirrus cloud altitudes, and so a new understanding of cirrus cloud formation is needed. This understanding is sought through an examination of cirrus cloud growth models.

Sassen, Kenneth↗
NASA NTRS2014

Validation Ice Crystal Icing Engine Test in the Propulsion Systems Laboratory at NASA Glenn Research Center

The Propulsion Systems Laboratory (PSL) is an existing altitude simulation jet engine test facility located at NASA Glenn Research Center in Clevleand, OH. It was modified in 2012 with the integration of an ice crystal cloud generation system. This paper documents the inaugural ice crystal cloud test in PSLthe first ever full scale, high altitude ice crystal cloud turbofan engine test to be conducted in a ground based facility. The test article was a Lycoming ALF502-R5 high bypass turbofan engine, serial number LF01. The objectives of the test were to validate the PSL ice crystal cloud calibration and engine testing methodologies by demonstrating the capability to calibrate and duplicate known flight test events that occurred on the same LF01 engine and to generate engine data to support fundamental and computational research to investigate and better understand the physics of ice crystal icing in a turbofan engine environment while duplicating known revenue service events and conducting test points while varying facility and engine parameters. During PSL calibration testing it was discovered than heated probes installed through tunnel sidewalls experienced ice buildup aft of their location due to ice crystals impinging upon them, melting and running back. Filtered city water was used in the cloud generation nozzle system to provide ice crystal nucleation sites. This resulted in mineralization forming on flow path hardware that led to a chronic degradation of performance during the month long test. Lacking internal flow path cameras, the response of thermocouples along the flow path was interpreted as ice building up. Using this interpretation, a strong correlation between total water content (TWC) and a weaker correlation between median volumetric diameter (MVD) of the ice crystal cloud and the rate of ice buildup along the instrumented flow path was identified. For this test article the engine anti-ice system was required to be turned on before ice crystal icing would occur. The ice crystal icing event, an uncommanded reduction in thrust, was able to be turned on and off by manipulating cloud TWC. A flight test point where no ice crystal icing event occurred was also duplicated in PSL. Physics based computational tools were successfully used to predict tunnel settings to induce ice buildup along the low pressure compression system flow path for several test points at incrementally lower altitudes, demonstrating that development of ice crystal icing scaling laws is potentially feasible. Analysis of PSL test data showed that uncommanded reduction in thrust occurs during ice crystal cloud on operation prior to fan speed reduction. This supports previous findings that the reduction of thrust for this test article is due to ice buildup leading to a restricted airflow from either physical or aerodynamic blockage in the engine core flow path.

Ice Crystal Icing↗
NASA NTRS2014

Validation Ice Crystal Icing Engine Test in the Propulsion Systems Laboratory at NASA Glenn Research Center

The Propulsion Systems Laboratory (PSL) is an existing altitude simulation jet engine test facility located at NASA Glenn Research Center in Cleveland, OH. It was modified in 2012 with the integration of an ice crystal cloud generation system. This paper documents the inaugural ice crystal cloud test in PSL--the first ever full scale, high altitude ice crystal cloud turbofan engine test to be conducted in a ground based facility. The test article was a Lycoming ALF502-R5 high bypass turbofan engine, serial number LF01. The objectives of the test were to validate the PSL ice crystal cloud calibration and engine testing methodologies by demonstrating the capability to calibrate and duplicate known flight test events that occurred on the same LF01 engine and to generate engine data to support fundamental and computational research to investigate and better understand the physics of ice crystal icing in a turbofan engine environment while duplicating known revenue service events and conducting test points while varying facility and engine parameters. During PSL calibration testing it was discovered than heated probes installed through tunnel sidewalls experienced ice buildup aft of their location due to ice crystals impinging upon them, melting and running back. Filtered city water was used in the cloud generation nozzle system to provide ice crystal nucleation sites. This resulted in mineralization forming on flow path hardware that led to a chronic degradation of performance during the month long test. Lacking internal flow path cameras, the response of thermocouples along the flow path was interpreted as ice building up. Using this interpretation, a strong correlation between total water content (TWC) and a weaker correlation between median volumetric diameter (MVD) of the ice crystal cloud and the rate of ice buildup along the instrumented flow path was identified. For this test article the engine anti-ice system was required to be turned on before ice crystal icing would occur. The ice crystal icing event, an uncommanded reduction in thrust, was able to be turned on and off by manipulating cloud TWC. A flight test point where no ice crystal icing event occurred was also duplicated in PSL. Physics based computational tools were successfully used to predict tunnel settings to induce ice buildup along the low pressure compression system flow path for several test points at incrementally lower altitudes, demonstrating that development of ice crystal icing scaling laws is potentially feasible. Analysis of PSL test data showed that uncommanded reduction in thrust occurs during ice crystal cloud on operation prior to fan speed reduction. This supports previous findings that the reduction of thrust for this test article is due to ice buildup leading to a restricted airflow from either physical or aerodynamic blockage in the engine core flow path.

Turbofan Engine↗
NASA NTRS1991

Charging of mesospheric particles - Implications for electron density and particle coagulation

The relationship between N(e) and mesospheric aerosols near the mesopause is studied. The full distribution of charges on mesospheric aerosols is calculated, including dust and ice particles with radii ranging from 1 to 400 nm. The N(e) and ion density N(i) are obtained and ionization height profiles are calculated. The effects of dust and ice particles on N(e) and N(i) are studied for a wide range of assumed conditions. The results indicate that aerosol concentrations associated with visible polar mesospheric clouds are unlikely to cause a severe N(e) depletion. The pronounced 'bite-out' of N(e) at about 87 km in the summertime may be caused by a large concentration of small ice particles in a narrow cold layer near the mesosphere. Net negative charge on mesospheric aerosols may severely inihibit coagulation, so that mesospheric dust would not grow significantly. A higher supersaturation with respect to water vapor would be needed for heterogeneous nucleation of ice crystals.

Jensen, Eric J.↗
NASA NTRS1990

The Colorado/Missouri 1989 cirrus mini IFO

A series of experiments with aircraft were planned for Nov. and Dec. 1989 to study cirrus ice crystal nucleation mechanisms and to test new aircraft instrumentation. The measurements were conducted using the NCAR Sabreliner and King Air. Sampling was conducted near Boulder, Colorado, in lenticular (mountain wave) clouds, and over Missouri in cirrus generating cells. Field samples of aerosol and ice crystal replicas and melt water from these cirrus clouds were collected and studied. Aircraft instrumentation and sampling techniques are discussed.

Heymsfield, Andrew J.↗
NASA NTRS1991

Characterizing water/rock interaction in simulated comet nuclei via calorimetry: Tool for in-situ science, laboratory analysis, and sample preservation

Although results from the Giotto and Vega spacecraft flybys of comet P/Halley indicate a complex chemistry for both the ices and dust in the nucleus, carbonaceous chondrite meteorites are still regarded as useful analogs for the rocky components. Carbonaceous chondrites mixed with water enable simulation of water/rock interactions which may occur in cometary nuclei. Three general types of interactions can be expected between water and minerals at sub-freezing temperatures: heterogeneous nucleation of ice by insoluble minerals; adsorption of water vapor by hygroscopic phases; and freezing and melting point depression of liquid water sustained by soluble minerals. Two series of experiments were performed in a differential scanning calorimeter (DSC) with homogenized powders of the following whole-rock meteorites and comparison samples: Allende (CV3), Murchison (CM2), Orgueil (CI), Holbrook (L6), and Pasamonte (eucrite) meteorites as well as on peridotite (PCC-1, USGS), saponite (Sap-Ca-1, CMS), montmorillonite (STx-1, CMS), and serpentine (Franciscan Formation, California). Results are briefly discussed.

Allton, Judith H.↗
NASA NTRS2024

Cloud Top Phase Characterization of Extratropical Cyclones over the Northeast and Midwest United States: Results from IMPACTS

Cloud top phase (CTP) impacts cloud albedo and pathways for ice particle nucleation, growth, and fallout within extratropical cyclones. This study uses airborne lidar, radar, and Rapid Refresh analysis data to characterize CTP within extratropical cyclones as a function of cloud top temperature (CTT). During the 2020, 2022, and 2023 Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign deployments, the Earth-Resources 2 (ER-2) aircraft flew 26 research flights over the Northeast and Midwest U.S. to sample the cloud tops of a variety of extratropical cyclones. A training dataset was developed to create probabilistic phase classifications based on Cloud Physics Lidar measurements of known ice and liquid clouds. These classifications were then used to quantify dominant CTP in the top 150 m of clouds sampled by the Cloud Physics Lidar in storms during IMPACTS. Case studies are presented illustrating examples of supercooled liquid water at cloud top at different CTT ranges (-3°C -20°C. Liquid-bearing cloud tops were found at CTTs as cold as -37ºC.

Troy J. Zaremba↗
NASA NTRS1980

Growth of ice discs from the vapor and the mechanism of habit change of ice crystals

Ice crystals nucleated on a liquid nitrogen cooled glass fiber grow first as thin disks which subsequently transform to plates and columns as they thicken and extend to regions of higher supersaturation. Crystals are often found to be dislocation-free, which suggests that growth results from surface nucleation, the habit depending on preferential nucleation in an adsorbed multilayer on basal or prism face.

Keller, V. W.↗
NASA NTRS1995

Nucleation and growth of crystals under cirrus and polar stratospheric cloud conditions

Laboratory studies examine phase changes of hygroscopic substances which occur as aerosol in stratosphere and troposphere (sodium chloride, ammonium sulfate, ammonium bisulfate, nitric acid, sulfuric acid), under controlled conditions, in samples volume 1 to 10(exp -4) ml. Crystallization of salts from supersaturated solutions is examined by slowly evaporating a solution drop on a substrate, under controlled relative humidity, until self nucleation occurs; controlled nucleation of ice in a mm capillary U-tube gives a measured ice crystallization velocity at known supercooling. Two states of crystallization occur for regions where hydrates exist. It is inferred that all of the materials readily exist as supersaturated/supercooled solutions; the degree of metastability appears to be slightly enhanced by inclusion of aircraft produced soot. The crystallization velocity is taken as a measure of viscosity. Results suggest an approach to a glass transition at high molality, supersaturation and/or supercooling within the range of atmospheric interest. It is hypothesized that surface reactions occur more readily on solidified particles - either crystalline or glass, whereas volume reactions are more important on droplets with sufficiently low viscosity and volume diffusivity. Implications are examined for optical properties of such particles in the atmosphere. In a separate experiment, crystal growth was examined in a modified thermal vapor diffusion chamber over the range of cirrus temperature (-30 to -70 C) and under controlled supersaturation and air pressure. The crystals grew at a velocity of 1-2 microns/s, thickness 60-70 micron, in the form of thin column crystals. Design criteria are given for a system to investigate particle growth down to -100 C, (PSC temperatures) where nitric acid particles can be grown under similar control and in the form of hydrate crystals.

Hallett, John↗
NASA NTRS2000

Methanogenesis, Mesospheric Clouds, and Global Habitability

Hyperthermophilic methanogens can exist in a deep hot biosphere up to 110 C, or 10 km deep. Methane (CH4) itself is thermodynamically stable to depths of 300 km. Geologic (microbial plus abiogenic thermal) methane is transported upward, attested to by its association with helium, to form petroleum pools. Near or at the surface, geologic CH4 mixes with other natural and with anthropogenic CH4 yielding annual emissions into the atmosphere of 500 Tg, of which 200 Tg are natural and 300 Tg are man-made. The atmospheric lifetime of CH4, a greenhouse gas 20 times more effective than CO2 in raising global temperatures, is approximately 10 years. It is removed from the atmosphere mainly by reactions with hydroxyl radical (OH) to form CO2, but also by dry soil and by conversion to H2O in the stratosphere and middle atmosphere. A sudden rise in atmospheric temperatures by 9-12 C some 55 million years ago has been explained by the release in a few thousand years of three trillion tons of CH4 out of 15 trillion tons that had formed beneath the sea floor. What prevented this CH4-induced greenhouse effect from running away? An analog to the CH4-burp of 55 million years ago is the CH4-doubling over the past century which resulted in a increase in upper level H2O from 4.3 ppmv to 6 ppmv. This 30% increase in H2O vapor yielded a tenfold increase in brightness of polar mesospheric clouds because of a strong dependence of the ice particle nucleation rate on the water saturation ratios. Models show that at a given temperature the optical depth of mesospheric clouds scales as [H2O]beta with beta varying between 4 and 8. Radiative transfer tools applied to mesospheric particles suggest that an optical depth of approximately one, or 1000 times the current mesospheric cloud optical depth, would result in tropospheric cooling of about 10 K. Assuming beta=6, a thousandfold increase in optical thickness would require a three-fold increase of H2O, or a 20-fold increase of CH4. At the current rate of anthropogenic emissions this is expected to occur within the next 1000 years. This timescale is also commensurate with what has been assumed for the CH4- burp 55 million years ago.

Pueschel, Rudolf F.↗
NASA NTRS1996

Comparisons Between the Formation of Polar Stratospheric Clouds and Cirrus Clouds

Analyses of lidar data taken during the 1989 AASE I program show that polar stratospheric clouds most often contain frozen particles, but sometimes contain spherical, presumably liquid, particles. In this paper the mechanisms that lead to the freezing of particles, and to the formation of liquid particles will be discussed based largely upon analyses of existing data. For example, trajectory studies help shed light on the conditions that lead to particle freezing. During April of 1996 an experiment using the NASA DC-8 and ER-2 aircraft will be conducted over the central U.S. Some of the goals of the project are to better understand the mechanisms of cirrus cloud formation, and to investigate the properties of freezing nuclei in the upper troposphere. Results from this field program will be presented as they apply to the topic of ice crystal nucleation. Comparisons will be drawn between the mechanisms that lead to new particle formation in the polar stratosphere, and the mechanisms that lead to new particles formation in the upper troposphere.

Toon, Owen B.↗
NASA NTRS2002

Microphysics and Radiative Properties of Cirrus: Instrumentation and Analysis

Work under this grant has involved further development of a new aircraft instrument (the cloudscope) for real time characterization of atmospheric particulates together with field observations of such particulates, both in the form of ice and also as nuclei responsible for nucleation of both ice and water cloud particles. Part of the work involving assessment of the frequency of ice crystal shapes has been carried out in collaboration with the Meteorological Service of Canada; part of the work in a field program with the NCAR C-130. Part of the work has been interpreted in terms of laboratory simulation of ice crystal growth under a wide variety of conditions carried out under a grant from Physical Meteorology Program, National Science Foundation.

Hallett, John↗
NASA NTRSDate not supplied

TPSAS-NF1676L-13393-DND

In the two plus decades since it became evident that polar stratospheric clouds (PSCs) play a major role in the springtime depletion of polar ozone, the detailed composition and morphology of PSCs has been an area of interest. Although our PSC knowledge base is substantial, there is still considerable uncertainty in specific key areas related to their composition and formation. Probably the least well understood of these is the nucleation process responsible for the formation of nitric acid trihydrate (NAT) particles and the circumstances under which NAT formation and growth leads to stratospheric denitrification. CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) is an excellent instrument for observing PSCs and has already produced an extensive set of PSC observations with unprecedented spatial and temporal resolution covering five winters. These observations are providing new insight into the key remaining questions regarding PSC composition and formation mechanisms. In this paper, we examine the CALIOP PSC observations in combination with a microphysical model in attempt to better understand the underlying physical mechanisms for NAT nucleation. Of particular interest is the early phase of the 2009-2010 Arctic winter when CALIOP frequently observed extended regions of tenuous NAT clouds, clearly before ice was present in the polar vortex. This provides unprecedented large-scale evidence that ice particles are not the only nuclei on which NAT may form. Microphysical model calculations along backward trajectories from these CALIOP NAT cloud observations are used to investigate possible ice-independent, heterogeneous NAT nucleation mechanisms. These analyses will then be expanded to other winters to assess the overall significance of an ice-independent nucleation mechanism for NAT PSCs.

M C Pitts↗
NASA NTRS2014

Attendee Response to Guiding Questions of the September 2014 DOE Workshop on North Slope of Alaska Priorities

We advocate for several modeling approaches suitable to prove understanding of and capability to model aerosol behavior in nucleating droplets and ice and to model regional cloud systems at the mesoscale. The full complement of data that is ideal for particular study types is increasingly well understood; the ASR ISDAC Science Plan provides an excellent example of listing the data required for each study type targeted by that campaign. Whereas discussion here focused on the microscale and mesoscale, other studies should obviously focus on the regional, seasonal and global scale. When considering ice microphysics alone, laser focus on unconstrained model components could be usefully intensified (e.g., collision-coalescence kernels). Similarly, a focus on boundary layer structure would be deeply valuable to a wide range of model types. The expense of observations motivates efficient planning for observational data sets to support specific study approaches; the concept of closure is often useful (e.g., the surface energy budget).

nucleation↗
NASA NTRS1996

The Structural Properties of Vapor Deposited Water Ice and Astrophysical Implications

Films of vapor deposited water ice at low temperature (T<30 K) show a number of interesting structural changes during a gradual warmup. We would like to talk about the structure of the low temperature high density amorphous form of water ice, the process of crystallization, and some recent work on the morphological changes of water ice films at high temperature. The studies of the high density amorphous form are from in-situ electron microscopy as well as numerical simulations of molecular dynamics and have lead to new insights into the physical distinction between this high density amorphous form and the low density amorphous form. For the process of crystallization, we propose a model that describes the crystallization of water ice from the amorphous phase to cubic ice in terms of the nucleation of small domains in the ice. This model agrees well with the behavior of water ice in our electron microscopy studies and finds that pure water above the glass transition is a strong liquid. In more recent work, we have concentrated on temperatures above the crystallization temperature and we find interesting morphological changes related to the decrease in viscosity of the amorphous component in the cubic crystalline regime. Given enough time, we would like to put these results in an astrophysical context and discuss some observed features of the frost on interstellar grains and the bulk ice in comets.

Jenniskens, P.↗
NASA NTRS1980

Ice crystal growth in a dynamic thermal diffusion chamber

Ice crystals were grown in a supersaturated environment produced by a dynamic thermal diffusion chamber, which employed two horizontal plates separated by a distance of 2.5 cm. Air was circulated between and along the 1.2 m length of the plates past ice crystals which nucleated and grew from a fiber suspended vertically between the two plates. A zoom stereo microscope with a magnification which ranged from 3X to 80X and both 35 mm still photographs and 16 mm time lapse cine films taken through the microscope were used to study the variation of the shape and linear growth rate of ice crystals as a function of the ambient temperature, the ambient supersaturation, and the forced ventilation velocity. The ambient growth conditions were varied over the range of temperature 0 to -40 C, over the range of supersaturation 4% to 50% with respect to ice, and over the range of forced ventilation velocities 0 cm/s to 20 cm/s.

Keller, V. W.↗
NASA NTRS1982

Measurements of the aerosol and ice crystal populations in tropical stratospheric cumulonimbus anvils

A pair of particle size spectrometers was flown aboard the NASA U-2 operating from the Canal Zone to make measurements of the aerosol and ice crystal budgets in cirrus produced by thunderstorms in the tropics. Measurements indicate that fairly large crystals up to 1 mm in size are injected into the stratosphere during cumulonimbus activity. Ice water contents range from a few thousandths to a few hundredths of a gram per cubic meter. Because the ambient temperature is typically around -80 C the mass of the larger crystals largely returns to lower altitudes before evaporating. Aerosol size distributions indicate a curious narrow growth mode between 0.15 and 0.2 micron in cirrus anvils which is absent outside these clouds. The presence of this narrow mode is attributed to near water saturation produced at cloud top. Nucleation of new ice crystals as well as aerosol is hypothesized

Knollenberg, R. G.↗