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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 NTRS2000

Unsteady High Turbulence Effects on Turbine Blade Film Cooling Heat Transfer Performance Using a Transient Liquid Crystal Technique

Unsteady wake effect, with and without trailing edge ejection, on detailed heat transfer coefficient and film cooling effectiveness distributions is presented for a downstream film-cooled gas turbine blade. Tests were performed on a five-blade linear cascade at an exit Reynolds number of 5.3 x 10(exp 5). Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. Coolant blowing ratio was varied from 0.4 to 1.2; air and CO2 were used as coolants to simulate different density ratios. Surface heat transfer and film effectiveness distributions were obtained using a transient liquid crystal technique; coolant temperature profiles were determined with a cold wire technique. Results show that Nusselt numbers for a film cooled blade are much higher compared to a blade without film injection. Unsteady wake slightly enhances Nusselt numbers but significantly reduces film effectiveness versus no wake cases. Nusselt numbers increase only slic,htly but film cooling, effectiveness increases significantly with increasing, blowing ratio. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher 0 effectiveness at lower blowing ratios (M = 0.8). Trailing edge ejection generally has more effect on film effectiveness than on the heat transfer, typically reducing film effectiveness and enhancing heat transfer. Similar data is also presented for a film cooled cylindrical leading edge model.

Han, J. C.↗
NASA NTRSDate not supplied

Formation of Tropopause Cirrus clouds by Typhoon-induced gravity waves during the Asian Summer Monsoon: A Case Study from the BATAL 2017 Campaign

Cirrus clouds in the Tropical Tropopause Layer (TTL) have a net warming impact on Earth’s climate and they regulate the amount of water vapor entering the lower stratosphere through dehydration process near the cold-point tropopause. During the Boreal summer, Asian Summer Monsoon (ASM) is an important source of cirrus clouds and humidity in the TTL owing to frequent deep convection. However, better representation of convection and TTL cirrus clouds in global climate models is needed for accurate assessment of their response to changing climate. In this study, we investigate the mechanisms involved in the formation of a tropopause cirrus cloud layer observed during the Balloon measurement campaigns of the Asian Tropopause Aerosol Layer (BATAL) over Hyderabad (17.47 °N, 78.58 °E), India on 23 August 2017. A subvisible cirrus cloud layer (optical thickness ~0.025) was detected by a backscatter sonde (COBALD) onboard a balloon near the cold-point tropopause (CPT, temperature~ -86.4 ° C, altitude~17.9 km) which was later confirmed by the CATS lidar on the ISS. Simultaneous measurements from an optical particle counter (Boulder Counter) revealed the presence of ice crystals smaller than 50 microns in this layer. The formation mechanism responsible for this tropopause cirrus is investigated using a technique combining three-dimensional back-trajectories, satellite observations, and ERA5 reanalysis data. Satellite observations revealed that the overshooting convection associated with a category-3 typhoon Hato, which hit Macau and Hong Kong on 23 August 2017 injected ice into the lower stratosphere. This caused a hydration patch that followed the ASM anticyclone subsequently moving towards Hyderabad. The presence of tropopause cirrus cloud layers in the cold temperature anomalies and updrafts along the back-trajectories indicated towards the role of typhoon-induced gravity waves in their formation. This case study highlights the role of typhoons in influencing the formation of tropopause cirrus clouds through stratospheric hydration and gravity waves in the ASM anticyclone.

Amit Kumar Pandit↗
NASA NTRS1973

Multiple jet study

Test data is presented which allows determination of jet penetration and mixing of multiple cold air jets into a ducted subsonic heated mainstream flow. Jet-to-mainstream momentum flux ratios ranged from 6 to 60. Temperature profile data is presented at various duct locations up to 24 orifice diameters downstream of the plane of jet injection. Except for two configurations, all geometries investigated had a single row of constant diameter orifices located transverse to the main flow direction. Orifice size and spacing between orifices were varied. Both of these were found to have a significant effect on jet penetration and mixing. The best mixing of the hot and cold streams was achieved with duct height.

Walker, R. E.↗
NASA NTRS1985

Variable frequency VLF signals in the magnetosphere Associated phenomena and plasma diagnostics

Coherent variable-frequency signals (ramps) extending from 1 to 8 kHz, injected into the magnetosphere from Siple Station, Antarctica (L=4.3), exhibit upper and lower cutoffs when received at the conjugate station, Roberval, Quebec. Ramp group delay measurements and ionospheric sounding data are used to determine the cold plasma density and L shell of the propagation path. Relationships among f, df/dt, and the 'phase equator' for gyroresonance are calculated using second-order resonance equations generalized to relativistic electrons. The concept thereby introduced is used to develop a diagnostic technique which, for an assumed g(alpha)(v exp -n) electron distribution, provides an estimate of the energy dependence n. Additional aspects of the magnetospheric response to ramp injection, such as emission triggering, curvature due to dispersion, and amplitude saturation, are discussed.

Carlson, C. R.↗
NASA NTRS1980

Cold water aquifer storage

A working prototype system is described in which water is pumped from an aquifer at 70 F in the winter time, chilled to a temperature of less than 50 F, injected into a ground-water aquifer, stored for a period of several months, pumped back to the surface in the summer time. A total of 8.1 million gallons of chilled water at an average temperature of 48 F were injected. This was followed by a storage period of 100 days. The recovery cycle was completed a year later with a total of 8.1 million gallons recovered. Approximately 20 percent of the chill energy was recovered.

Reddell, D. L.↗
NASA NTRS1975

Hypersonic engine airplane integration

A summary of the research activities is presented along with the design and analysis of an integrated scramjet engine which utilizes heat conduction flames. The scramjet engine model described was tested at a freestream Mach number of 4.0 by personnel at the General Applied Science Laboratory. The research effort was primarily concerned with the interpretation and analysis of the experimental data. The mixing tests were conducted with cold ambient air, while the combustion tests were conducted with hot vitiated air. The purpose of the cold mixing tests was to determine the degree of mixedness of the fuel at the ignitor station so as to certify if the fuel injection conditions and fuel injectors locations were properly selected to give a uniform fuel concentration profile at the ignitor station. A second objective was to assess the influence of the fuel injection on the inlet flow. Several fuel injection configurations were tested.

Source record↗
NASA NTRS1986

Beam-induced pressure gradients in the early phase of proton-heated solar flares

The pressure gradient induced in a coronal loop by proton beam momentum deposition is calculated and compared with the thermal pressure gradient arising from nonuniform deposition of beam energy; it is assumed that the transfer of momentum and energy from beam to target occurs via the Coulomb interaciton. Results are presented for both a low mean energy and a high mean energy proton beam injected at the loop apex and characterized by a power-law energy spectrum. The present treatment takes account of the breakdown of the cold target approximation for the low-energy proton beam in the corona, where the thermal speed of target electrons exceeds the beam speed. It is found that proton beam momentum deposition plays a potentially significant role in flare dynamics only in the low mean energy case and only in the corona, where it may dominate the acceleration of target material for as long as several tens of seconds. This conclusion suggest that the presence of low-energy nonthermal protons may be inferred from velocity-sensitive coronal observations in the early impulsive phase.

Tamres, David H.↗
NASA NTRS2016

Modeling the Rapid Boil-Off of a Cryogenic Liquid When Injected into a Low Pressure Cavity

Many launch vehicle cryogenic applications require the modeling of injecting a cryogenic liquid into a low pressure cavity. The difficulty of such analyses lies in accurately predicting the heat transfer coefficient between the cold liquid and a warm wall in a low pressure environment. The heat transfer coefficient and the behavior of the liquid is highly dependent on the mass flow rate into the cavity, the cavity wall temperature and the cavity volume. Testing was performed to correlate the modeling performed using Thermal Desktop and Sinda Fluint Thermal and Fluids Analysis Software. This presentation shall describe a methodology to model the cryogenic process using Sinda Fluint, a description of the cryogenic test set up, a description of the test procedure and how the model was correlated to match the test results.

Fluid Mechanics↗
NASA NTRS1993

Feasibility of detecting aircraft wake vortices using passive microwave radiometers

The feasibility of detecting the cold core of the wake vortex from the wingtips of an aircraft using a passive microwave radiometer was investigated. It was determined that there is a possibility that a cold core whose physical temperature drop is 10 C or greater and which has a diameter of 5 m or greater can be detected by a microwave radiometer. The radiometer would be a noise injection balanced Dicke radiometer operating at a center frequency of 60 GHz. It would require a noise figure of 5 dB, a predetection bandwidth of 6 GHz, and an integration time of 2 seconds resulting in a radiometric sensitivity of 0.018 K. However, three additional studies are required. The first would determine what are the fluctuations in the radiometric antenna temperature due to short-term fluctuations in atmospheric pressure, temperature, and relative humidity. Second, what is the effect of the pressure and temperature drop within the cold core of the wake vortex on its opacity. The third area concerns the possibility of developing a 60 GHz radiometer with a radio metric sensitivity an order of magnitude improvement over the existing state of the art.

Harrington, Richard F.↗
NASA NTRS2014

Patterns of Convective Influence and Temperature in the TTL during ATTREX

The Tropical Tropopause Layer, a zonal torus of air around 13-18km altitude and -30 to 30 latitude,is the gatekeeper for air entering the stratosphere from the troposphere. The overall speed of theupward motion affects the input of all the trace constituents, but how the upward transfer is distributedbetween convective injection and slow ascent indirectly driven by breaking waveshas a critical effect on both water and some short-lived species (e.g., bromine compounds). Convection'spotential ability to bypass the cold trap in the center of the TTL torus can contribute to stratospherichydration. Convection can also quickly move short-lived tracers to higher altitudes (and higher ozonevalues), and contribute to ozone destruction.This presentation focusses on the relationship of convectively influenced air to temperature in the TTL, withan emphasis on the qualitative evolution during ATTREX. We use a technique of obtaining global, highresolution distributions of convective cloud tops at 3-hourly intervals to derive distributions ofconvectively influenced air in the TTL, and examine its relationship to TTL temperature. TTL temperaturedistributions are often affected directly by convection, but equatorial and other gravity waves having a varietyof space and time scales are also important. The relationship of these temperature patterns to outputfrom convection will determine whether hydrated air remains in the TTL, or whether it is stripped of itswater soon after injection.

Pfister, Leonhard↗
NASA NTRS1983

LOX/hydrocarbon fuel carbon formation and mixing data analysis

By applying the Priem-Heidmann Generalized-Length vaporization correlation, the computer model developed by the present study predicts the spatial variation of propellant vaporization rate using the injector cold flow results to define the streamtubes. The calculations show that the overall and local propellant vaporization rate and mixture ratio change drastically as the injection element type or the injector operating condition is changed. These results are compared with the regions of carbon formation observed in the photographic combustion testing. The correlation shows that the fuel vaporization rate and the local mixture ratio produced by the injector element have first order effects on the degree of carbon formation.

Fang, J.↗
NASA NTRS1999

Method and apparatus for cold gas reinjection in through-flow and reverse-flow wave rotors

A method and apparatus for cold gas reinjection in through-flow and reverse-flow wave rotors having a plurality of channels formed around a periphery thereof. A first port injects a supply of cool air into the channels. A second port allows the supply of cool air to exit the channels and flow to a combustor. A third port injects a supply of hot gas from the combustor into the channels. A fourth port allows the supply of hot gas to exit the channels and flow to a turbine. A diverting port and a reinjection port are connected to the second and third ports, respectively. The diverting port diverts a portion of the cool air exiting through the second port as reinjection air. The diverting port is fluidly connected to the reinjection port which reinjects the reinjection air back into the channels. The reinjection air evacuates the channels of the hot gas resident therein and cools the channel walls, a pair of end walls of the rotor, ducts communicating with the rotor and subsequent downstream components. In a second embodiment, the second port receives all of the cool air exiting the channels and the diverting port diverts a portion of the cool air just prior to the cool air flowing to the combustor.

Nalim, M. Razi↗
NASA NTRS2009

Cold-Flow Testing of a Proposed Integrated Center-Body Diffuser/Steam Blocker Concept for Plum Brook Station's B-2 Test Facility

The center-body diffuser (CBD) steam blocker (SB) system is a concept that incorporates a set of secondary drive nozzles into the envelope of a CBD, such that both nozzle systems (i.e., the rocket engine and the steam blocking nozzles) utilize the same supersonic diffuser, and will operate either singularly or concurrently. In this manner, the SB performs as an exhaust system stage when the rocket engine is not operating, and virtually eliminates discharge flow on rocket engine shutdown. A 2.25-percent scale model of a proposed SB integrated into a diffuser for the Plum Brook B-2 facility was constructed and cold-flow tested for the purpose of evaluating performance characteristics of various design options. These specific design options addressed secondary drive nozzle design (method of steam injection), secondary drive nozzle location relative to CBD throat, and center-body throat length to diameter (L/D) ratios. The objective of the test program is to identify the desired configuration to carry forward should the next phase of design proceed. The tested scale model can provide data for various pressure ratios; however, its design is based on a proposed B-2 spray chamber (SC) operating pressure of 4.0 psia and a steam supply pressure of 165 psia. Evaluation of the test data acquired during these tests indicate that either the discrete axial or annular nozzle configuration integrated into a CBD, with an annular throat length of 1.5 L/D at the nominal injection position, would be suitable to carry forward from the SB's perspective. Selection between these two then becomes more a function of constructability and implementation than performance. L/D also has some flexibility, and final L/D selection can be a function of constructability issues within a limited range.

Edwards, Daryl A.↗
NASA NTRS1975

Theoretical and experimental study of flow through turbine cascades with coolant flow injection

An analytical study is presented which deals with the change in the outlet flow conditions from a turbine blade row due to coolant air injection through slots. The analysis applies to small secondary to primary mass flow ratios, taking into consideration the change in boundary layer development resulting from injection. The effects of injection location, injection flow angle and injected air momentum flux are investigated. The results of the present analysis are compared with the values obtained using the mixing theory method and experimental data from cold flow tests in a turbine cascade tunnel.

Tabakoff, W.↗
NASA NTRS1977

Cold plasma diagnostics using satellite measurements of VLF signals from ground transmitters

A diagnostic technique to obtain the cold-plasma density profile in the magnetosphere is introduced. This method uses satellite measurements of group delay and pulse duration of VLF signals from ground transmitters in conjunction with a detailed ray-tracing analysis. An iterative method is involved which starts with an approximate density profile, computes the ray paths for that profile, and then compares the properties of the rays that reach the satellite location with the actual satellite measurements. The density profile is then modified to account for any discrepancies between the two results. The same process is repeated with the new profile until one has reasonable agreement between the data and ray-tracing results. This method is applied to the case of an Imp 6 pass, where strong signals from the Siple VLF transmitter were observed for over 25 min. Good agreement is found between the results of the proposed technique and the well-known ground whistler techniques of cold-plasma diagnostics. The results also serve to illustrate the wide diversity of propagation paths from ground transmitters to high-altitude satellites during VLF wave-injection experiments.

Inan, U. S.↗
NASA NTRS1977

Effect of endwall cooling on secondary flows in turbine stator vanes

An experimental investigation was performed to determine the effect of endwall cooling on the secondary flow behavior and the aerodynamic performance of a core-turbine stator vane. The investigation was conducted in a cold-air, full-annular cascade, where three-dimensional effects could be obtained. In one configuration, the cooling holes were oriented so that the coolant was injected in line with the inviscid streamline direction. In another configuration, the coolant was injected at an angle of 15 deg to the inviscid streamline direction and oriented toward the vane pressure surface. Total-pressure surveys were taken downstream of the stator vanes over a range of cooling flows. Changes in the total-pressure contours downstream of the vanes were used to obtain the effect of endwall cooling on the secondary flows in the stator. Comparisons are made between the two cooled-endwall configurations and with the results obtained previously for solid (uncooled) endwalls.

Goldman, L. J.↗
NASA NTRS1978

The collisional interaction of a beam of charged particles with a hydrogen target of arbitrary ionization level

The classical theory of scattering under the Coulomb potential of both charged and neutral particles is used to derive formulae for the energy deposition rate and mean scattering of a beam of charged particles interacting with a cold hydrogen target of arbitrary ionization level as a function of the column density traversed by the beam. These general results hold for any form of stable injection energy spectrum, and their relevance to the existing literature on chromospheric heating during solar flares is discussed.

Emslie, A. G.↗
NASA NTRS2014

A Method for Obtaining High Time and Spatial Resolution Convective Cloud Top Data for the TTL

A method for obtaining high time and spatial resolution convective cloud top data for the TTL Leonhard Pfister, Eric Jensen, Rei Ueyama, Eliot Atlas, and Maria Navarro Convective systems in the tropics have a maximum in the cloud top altitude distribution of about 13.5 km. However, there is a significant tail to this distribution -- a few percent reach the cold point tropopause (CPT) at 16.5 km, and there has been clear evidence of convective mass deposited as high as 19 km in the tropics. The region between 13.5 km and the cold point tropopause is transitional, between the free tropical troposphere where convective mixing dominates, and the stratosphere where slow upward ascent dominates. In this region (the Tropical Tropopause Layer), convective injection, slow ascent, and mixing from midlatitudes all have similar time scales. So, even though only a few percent of convective systems reach the CPT, convection is important. Space Based Lidar and cloud radar measurements have yielded information about long term average statistical distributions of cloud altitude as a function of location. However, we also need time-dependent cloud top altitude and cloud top potential temperature information, primarily to understand the water vapor and TTL cloud distributions. This is because the effect of convection depends on the local temperature, and on the subsequent temperature history. Time dependent cloud top information is also needed to understand short-lived tracers because cross-isentropic flow is time and space dependent. This paper presents a method of obtaining time and space dependent convective cloud top theta (and altitude) information using 3-hourly geostationary brightness temperature data, coupled with global 3 -hourly rainfall estimates and temperature analyses. We explore different mixing algorithms to obtain the most reasonable agreement with near-simultaneous observations by cloudsat and calipso. Observations of short-lived tracers from ATTREX, coupled with short-term trajectories are used to test the method's accuracy. An important caveat is the ambiguity of evaluating convective cloud top altitudes under from combined cloudsat and calipso measurements.

cold point tropopause (CPT)↗