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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 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Grid-refinement study of hypersonic laminar flow over a 2-D ramp

Computations were made for those test cases of Problem 3 which were designated as laminar flows, viz., test cases 3.1, 3.2, 3.4, and 3.5. These test cases corresponded to flows over a flat plate and a compression ramp at high Mach number and at high Reynolds number. The computations over the compression ramps indicate a substantial streamwise extent of separation. Based on previous experience with separated laminar flows at high Mach numbers which indicated a substantial effect with spatial grid refinement, a series of computations with different grid sizes were performed. Also, for the flat plate, comparisons of the results for two different algorithms were made.

Thomas, James L.↗
DOE OSTI2024

Oxadiazole derivatives as stable anolytes for >3 V non-aqueous redox flow battery

Effective utilization of energy from renewable sources such as wind and solar requires the development of long duration energy storage (LDES) systems that can accommodate intermittent energy accrual. One option under investigation is the use of a redox flow battery (RFB). A significant amount of work has explored aqueous RFB systems with a variety of inorganic and organic carriers. However, moving to a nonaqueous solvent such as acetonitrile (MeCN) for RFB provides a much larger electrochemical window, which could lead to increased energy density if properly utilized. Here, in this work, we investigate a series of 2,5-diphenyl-1,3,4-oxadiazole (DiPhenOx) derivatives as anolytes for a redox flow battery. DiPhenOx has a low voltage redox event that, while reversible by cyclic voltammetry, was determined to be irreversible during bulk electrolysis. To improve cycling performance, we introduced various ester and cyano groups to the phenyl rings of DiPhenOx using molecular engineering. We characterized these derivatives spectroscopically and electrochemically to assess their feasibility for flow battery applications. The ester derivatives with the best cycling performance were tested in a flow cell vs. ferrocene, 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene (DBBB) and thianthrene, which resulted in ~2 V, ~3 V and ~3 V redox flow batteries, respectively.

25 ENERGY STORAGE↗
DOE OSTI2011

Low Conductivity SiC/SiC Ceramic Composites for Fusion Blanket Flow Channel Inserts

Dual-coolant blanket designs for fusion reactors currently under development benefit from flow channel inserts that possess low electrical conductivity and low thermal conductivity. Such flow channel inserts will advance the state of fusion technology closer to producing continuous low cost, non-polluting power as is planned under DEMO. In addition to low electrical and thermal conductivity, the desired properties of the flow channel insert are compatibility with lead-lithium breeder/coolant, stability under a high neutron fluence, and mechanical robustness. Silicon carbide fiber-reinforced silicon carbide matrix composites (SiC/SiC) have been shown to meet all of these requirements with the exception of the thermal conductivity requirement. Efforts to manipulate the thermal conductivity included compositional and architectural approaches. An architecturally engineered SiC/SiC was demonstrated that met the low through-thickness thermal conductivity. An understanding of the factors controlling the through-thickness electrical conductivity was also developed and now allows engineering control of the electrical conductivity within the composite. Refinements in the design of a SiC/SiC composite flow channel insert were performed as well as identifying critical mechanical properties. Testing in molten Pb-Li was performed in a building-block manner starting with coupons and culminating in the testing of SiC/SiC flow channel insert segments at ~500ºC under 10 psig. Sections of both a simpler monocoque SiC/SiC flow channel insert and a nested flow channel insert were evaluated for compatibility and impermeability in the Pb-Li and included in situ measurements of electrical and thermal conductivity.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Wind tunnel test data for wing trailing vortex flow survey

Data are presented on velocity measurements made with hot wire anemometers in the wake of a model of the CV-990 aircraft and a rectangular wing in the NASA-Ames 2.14x3.05 meter (7- by 10-foot) wind tunnels. Variables included angle of attack, tunnel speed and axial distance up to 12 chord lengths downstream from the wing trailing edge. Effects of deflecting trailing edge flaps and small spoiler panels are shown.

Chigier, N. A.↗
NASA NTRS1972

Ground and flight test program of a Stokes-flow parachute: Packaging, deployment, and sounding rocket integration

The current design and hardware components of the patented 14 sqm Stokes flow parachute are described. The Stokes-flow parachute is a canopy of open mesh material, which is kept deployed by braces. Because of the light weight of its mesh material, and the high drag on its mesh elements when they operate in the Stokes-flow flight regime, this parachute has an extremely low ballistic coefficient. It provides a stable aerodynamic platform superior to conventional nonporous billowed parachutes, is exceptionally packable, and is easily contained within the canister of the Sidewinder Arcas or the RDT and E rockets. Thus, it offers the potential for gathering more meteorological data, especially at high altitudes, than conventional billowed parachutes. Methods for packaging the parachute are also recommended. These methods include schemes for folding the canopy and for automatically releasing the pressurizing fluid as the packaged parachute unfolds.

Niederer, P. G.↗
NASA NTRS1977

Verification test of the MSFC solar simulator using a Honeywell double-covered liquid solar collector

Additional verification data to support the utilization of the MSFC Solar Simulator for testing solar collectors was obtained. The Honeywell double-covered liquid solar collector number 2 for which thermal performance data under natural outdoor conditions had been previously obtained was installed on the Solar Simulator and subjected to a series of eight tests under various conditions of wind flow rate. Although these test conditions were not absolutely identical to those of the outdoor tests, they are considered to be sufficiently representative to provide a basis for an accurate comparative analysis of the data recorded for both test programs.

Shih, K., Sr.↗
NASA NTRS1981

Experimental investigations on the V/STOL tunnel at NASA/Langley Research Center

The flow characteristics of the V/STOL tunnel were investigated. The results show an interaction between tunnel components. The flow around the tunnel circuit gradually deteriorated with increasing distance from the testing area. The flow in the first diffuser was still satisfactory at the beginning of the circuit, while at the end of the circuit, the flow approaching the contraction became entirely unsatisfactory. Deterioration of flow was due largely to turning the stream around the corners, with the resulting flow distortion affecting the diffusers downstream. The large end of the last diffuser stalled on one side and nearly stalled the flow at the tip of the fan. It was found that these adverse flow characteristics reduce the flow quality and the efficiency of the tunnel.

Barna, P. S.↗
NASA NTRS1980

Effect of facility variation on the acoustic characteristics of three single stream nozzles

The characteristics of the jet noise produced by three single stream nozzles were investigated statistically at the NASA-Lewis Research Center outdoor jet acoustic facility. The nozzles consisted of a 7.6 cm diameter convergent conical, a 10.2 cm diameter convergent conical and an 8-lobe daisy nozzle with 7.6 cm equivalent diameter flow area. The same nozzles were tested previously at cold flow conditions in other facilities such as the Royal Aircraft Establishment (RAE) 7.3 m acoustic wind tunnel. The acoustic experiments at NASA covered pressure ratios from 1.4 to 2.5 at total temperatures of 811 K and ambient. The data obtained with four different microphone arrays are compared. The results are also compared with data taken at the RAE facility and with a NASA prediction procedure.

Gutierrez, O. A.↗
NASA NTRS1985

Computer program for calculating flow parameters and power requirements for cryogenic wind tunnels

A computer program has been written that performs the flow parameter calculations for cryogenic wind tunnels which use nitrogen as a test gas. The flow parameters calculated include static pressure, static temperature, compressibility factor, ratio of specific heats, dynamic viscosity, total and static density, velocity, dynamic pressure, mass-flow rate, and Reynolds number. Simplifying assumptions have been made so that the calculations of Reynolds number, as well as the other flow parameters can be made on relatively small desktop digital computers. The program, which also includes various power calculations, has been developed to the point where it has become a very useful tool for the users and possible future designers of fan-driven continuous-flow cryogenic wind tunnels.

Dress, D. A.↗
NASA NTRS1985

Combustor flame flashback

A stainless steel, two-dimensional (rectangular), center-dump, premixed-prevaporized combustor with quartz window sidewalls for visual access was designed, built, and used to study flashback. A parametric study revealed that the flashback equivalence ratio decreased slightly as the inlet air temperature increased. It also indicated that the average premixer velocity and premixer wall temperature were not governing parameters of flashback. The steady-state velocity balance concept as the flashback mechanism was not supported. From visual observation several stages of burning were identified. High speed photography verified upstream flame propagation with the leading edge of the flame front near the premixer wall. Combustion instabilities (spontaneous pressure oscillations) were discovered during combustion at the dump plane and during flashback. The pressure oscillation frequency ranged from 40 to 80 Hz. The peak-to-peak amplitude (up to 1.4 psi) increased as the fuel/air equivalence ratio was increased attaining a maximum value just before flashback. The amplitude suddenly decreased when the flame stabilized in the premixer. The pressure oscillations were large enough to cause a local flow reversal. A simple test using ceramic fiber tufts indicated flow reversals existed at the premixer exit during flickering. It is suspected that flashback occurs through the premixer wall boundary layer flow reversal caused by combustion instability. A theoretical analysis of periodic flow in the premixing channel has been made. The theory supports the flow reversal mechanism.

Proctor, M. P.↗
NASA NTRS1991

Application of a new K-tau model to near wall turbulent flows

A recently developed K-tau model for near wall turbulent flows is applied to two severe test cases. The turbulent flows considered include the incompressible flat plate boundary layer with the adverse pressure gradients and incompressible flow past a backward facing step. Calculations are performed for this two-equation model using an anisotropic as well as isotropic eddy-viscosity. The model predictions are shown to compare quite favorably with experimental data.

Thangam, S.↗
NASA NTRS1990

A numerical study of hypersonic stagnation heat transfer predictions at a coordinate singularity

The problem of grid induced errors associated with a coordinate singularity on heating predictions in the stagnation region of a three-dimensional body in hypersonic flow is examined. The test problem is for Mach 10 flow over an Aeroassist Flight Experiment configuration. This configuration is composed of an elliptic nose, a raked elliptic cone, and a circular shoulder. Irregularities in the heating predictions in the vicinity of the coordinate singularity, located at the axis of the elliptic nose near the stagnation point, are examined with respect to grid refinement and grid restructuring. The algorithm is derived using a finite-volume formulation. An upwind-biased total-variation diminishing scheme is employed for the inviscid flux contribution, and central differences are used for the viscous terms.

Grasso, Francesco↗
NASA NTRS1991

Development of a CFD Code for Analysis of Fluid Dynamic Forces in Seals

The aim is to develop a 3-D computational fluid dynamics (CFD) code for the analysis of fluid flow in cylindrical seals and evaluation of the dynamic forces on the seals. This code is expected to serve as a scientific tool for detailed flow analysis as well as a check for the accuracy of the 2D industrial codes. The features necessary in the CFD code are outlined. The initial focus was to develop or modify and implement new techniques and physical models. These include collocated grid formulation, rotating coordinate frames and moving grid formulation. Other advanced numerical techniques include higher order spatial and temporal differencing and an efficient linear equation solver. These techniques were implemented in a 2D flow solver for initial testing. Several benchmark test cases were computed using the 2D code, and the results of these were compared to analytical solutions or experimental data to check the accuracy. Tests presented here include planar wedge flow, flow due to an enclosed rotor, and flow in a 2D seal with a whirling rotor. Comparisons between numerical and experimental results for an annular seal and a 7-cavity labyrinth seal are also included.

Athavale, Mahesh M.↗