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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The study of local overheating and plasma formation on stainless steel z-pinch targets

Plasma formation from intensely ohmically heated conductors is known to be highly non-uniform, as local overheating can be driven by micron-scale imperfections. Detailed understanding of plasma formation is required to predict the performance of magnetically driven physics targets and magnetically-insulated transmission lines (MITLs). Previous LDRD-supported work (projects 178661 and 200269) developed the electrothermal instability (ETI) platform, on the Mykonos facility, to gather high-resolution images of the self-emission from the non-uniform ohmic heating of z-pinch rods. Experiments studying highly inhomogeneous alloyed aluminum captured complex heating topography. To enable detailed comparison with magnetohydrodynamic (MHD) simulation, 99.999% pure aluminum rods in a z-pinch configuration were diamond-turned to ~10nm surface roughness and then further machined to include well-characterized micron-scale "engineered" defects (ED) on the rod's surface (T.J. Awe, et al., Phys. Plasmas 28, 072104 (2021)). In this project, the engineered defect hardware and diagnostic platform were used to study ETI evolution and non-uniform plasma formation from stainless steel targets. The experimental objective was to clearly determine what, if any, role manufacturing, preparation, or alloy differences have in encouraging nonuniform heating and plasma formation from high-current density stainless steel. Data may identify improvements that may be implemented in the fabrication/preparation of electrodes used on the Z machine. Preliminary data shows that difference in manufacturer has no observed effect on ETI evolution, stainless alloy 304L heated more uniformly than alloy 310 at similar current densities, and that stainless steel undergoes the same evolutionary ETI stages as ultra-pure aluminum, with increased emission tied to areas of elevated surface roughness.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Alloy Design Workbench-Surface Modeling Package Developed

NASA Glenn Research Center's Computational Materials Group has integrated a graphical user interface with in-house-developed surface modeling capabilities, with the goal of using computationally efficient atomistic simulations to aid the development of advanced aerospace materials, through the modeling of alloy surfaces, surface alloys, and segregation. The software is also ideal for modeling nanomaterials, since surface and interfacial effects can dominate material behavior and properties at this level. Through the combination of an accurate atomistic surface modeling methodology and an efficient computational engine, it is now possible to directly model these types of surface phenomenon and metallic nanostructures without a supercomputer. Fulfilling a High Operating Temperature Propulsion Components (HOTPC) project level-I milestone, a graphical user interface was created for a suite of quantum approximate atomistic materials modeling Fortran programs developed at Glenn. The resulting "Alloy Design Workbench-Surface Modeling Package" (ADW-SMP) is the combination of proven quantum approximate Bozzolo-Ferrante-Smith (BFS) algorithms (refs. 1 and 2) with a productivity-enhancing graphical front end. Written in the portable, platform independent Java programming language, the graphical user interface calls on extensively tested Fortran programs running in the background for the detailed computational tasks. Designed to run on desktop computers, the package has been deployed on PC, Mac, and SGI computer systems. The graphical user interface integrates two modes of computational materials exploration. One mode uses Monte Carlo simulations to determine lowest energy equilibrium configurations. The second approach is an interactive "what if" comparison of atomic configuration energies, designed to provide real-time insight into the underlying drivers of alloying processes.

Abel, Phillip B.↗
NASA NTRS1993

Comparison of liquid rocket engine base region heat flux computations using three turbulence models

The flow in the base region of launch vehicles is characterized by flow separation, flow reversals, and reattachment. Computation of the convective heat flux in the base region and on the nozzle external surface of Space Shuttle Main Engine and Space Transportation Main Engine (STME) is an important part of defining base region thermal environments. Several turbulence models were incorporated in a CFD code and validated for flow and heat transfer computations in the separated and reattaching regions associated with subsonic and supersonic flows over backward facing steps. Heat flux computations in the base region of a single STME engine and a single S1C engine were performed using three different wall functions as well as a renormalization-group based k-epsilon model. With the very limited data available, the computed values are seen to be of the right order of magnitude. Based on the validation comparisons, it is concluded that all the turbulence models studied have predicted the reattachment location and the velocity profiles at various axial stations downstream of the step very well.

Kumar, Ganesh N.↗
DOE OSTI2019

Facile in Situ Syntheses of Cathode Protective Electrolyte Additives for High Energy Density Li-Ion Cells

Increasing the energy densities of Li-ion batteries necessitates operation of layered lithiated oxide cathodes at potentials exceeding 4 V vs Li/Li + . When continually exposed to such high potentials, these materials gradually deteriorate unless protected by sacrificial agents called electrolyte additives. During the formation cycles, these electrolyte additives decompose on the electrodes forming thin protective layers of insoluble products impeding further deleterious reactions. Some of these electrolyte additives spontaneously react when introduced into the electrolyte to yield specific surface-modifying products that alone protect the cathode; in other words, the nominal additive is the precursor and the secondary product is the protective agent. Guided by this insight, we used molecular engineering to obtain such surface-active secondary products in situ with 100% yield. Two of these electrolyte additives proved exceptional in that they delay both the impedance rise and capacity fade in the Li-ion cells. We demonstrate this protective action and scrutinize the activation of these additives in the electrolyte. As a result, by “taming” spontaneous reactions and regaining full control over the chemical structure, new avenues open to targeted synthesis of electrolyte additives extending the operation of high voltage Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2019

Ultra-scalable Multifunctional Nanoengineered Cu and Al surfaces for anti-biofouling applications

Biofouling disrupts surface functionality and integrity of engineered substrates. A variety of natural materials such as plant leaves and insect wings have evolved sophisticated physical mechanisms capable of preventing biofouling. Over the past decade, several reports have pinpointed nanoscale surface topography as an important regulator of the surface adhesion and growth of bacteria. Although artificial nanoengineered features have been used to create bactericidal materials that kill adhered bacteria, functional surfaces capable of synergistically providing anti-biofouling and bactericidal properties remain to be developed. Furthermore,fundamental questions pertaining to the need for intrinsic hydrophobicity to achieve bactericidal performance or the crucial role played by structure length scale (nano vs. micro), remain to be answered. Here, we demonstrate highly scalable, cost effective, and efficient nanoengineered multifunctional surfaces that possess both anti-biofouling and bactericidal properties on industrially relevant copper (Cu) and aluminum (A1) substrates. We characterize biofouling and bactericidal performance using a combination of scanning electron microscopy (SEM), atomic force microscopy (AFM), live-dead bacterial staining and imaging, as well as solution phase measurements of bacterial viability. SEM results showed that nanostructures created on both Cuand Al were capable of physical deformation of adhered E. coli . Bacterial viability measurements on both Cu and Al indicated a complex interaction between the anti-biofouling and bactericidal nature of these materials and their surface topography, chemistry, and structure. We found that nano-length structures, as compared to micro-length, provide improved bactericidal properties,and that increased hydrophobicity greatly decreased the of adhered bacteria while also modestly increasing the surfaces killing capacity. This study provides additional insights into design guidelines for materials that are not only bactericidal, but also anti-biofouling, using a simple and economic method.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRSDate not supplied

Performance of the Dragonfly Mass Spectrometer (DraMS) Programmable UV Laser Source Engineering Test Unit (ETU)

NASA’s Dragonfly mission will sample surface materials from multiple sites on Saturn’s largest moon, Titan, in exploration of its potential for prebiotic chemistry. We report on the performance of our short-pulsed UV laser transmitter, developed for the Dragonfly’s on-board Mass Spectrometer (DraMS). Our engineering test unit (ETU) has completed flight qualification and demonstrated its operational science requirements, such that the final flight unit build can begin. The Titan Hydrocarbon Analysis Nanosecond Optical Source (THANOS) ETU laser produces 266 nm laser pulses at programmable energy levels in order to create high resolution laser desorption mass spectrometry (LDMS) measurements. The laser operates in short bursts of 1-50 pulses, each at < 2 ns pulse width, at a 100 Hz repetition rate. Creating a sealed Titanium unit, capable of operation on the extreme environment of Titan’s surface was a major engineering challenge. The laser successfully demonstrated its ability to meet all operational requirements in terms of pulse energy, beam pointing on target and repeatability even after extensive environmental testing.

Matthew W Mullin↗
NASA NTRSDate not supplied

Performance of the Dragonfly Mass Spectrometer (DraMS) Programmable UV Laser Source Engineering Test Unit (ETU)

NASA’s Dragonfly mission will sample surface materials from multiple sites on Saturn’s largest moon, Titan, in exploration of its potential for prebiotic chemistry. We report on the performance of our short-pulsed UV laser transmitter, developed for the Dragonfly’s on-board Mass Spectrometer (DraMS). Our engineering test unit (ETU) has completed flight qualification and demonstrated its operational science requirements, such that the final flight unit build can begin. The Titan Hydrocarbon Analysis Nanosecond Optical Source (THANOS) ETU laser produces 266 nm laser pulses at programmable energy levels in order to create high resolution laser desorption mass spectrometry (LDMS) measurements. The laser operates in short bursts of 1-50 pulses, each at < 2 ns pulse width, at a 100 Hz repetition rate. Creating a sealed Titanium unit, capable of operation on the extreme environment of Titan’s surface was a major engineering challenge. The laser successfully demonstrated its ability to meet all operational requirements in terms of pulse energy, beam pointing on target and repeatability even after extensive environmental testing.

Matthew Mullin↗
NASA NTRS1998

Using Engine Thrust for Emergency Flight Control: MD-11 and B-747 Results

With modern digital control systems, using engine thrust for emergency flight control to supplement or replace failed aircraft normal flight controls has become a practical consideration. The NASA Dryden Flight Research Center has developed a propulsion-controlled aircraft (PCA) system in which computer-controlled engine thrust provides emergency flight control. An F-15 and an MD-11 airplane have been landed without using any flight control surfaces. Preliminary studies have also been conducted that show that engines on only one wing can provide some flight control capability if the lateral center of gravity can be shifted toward the side of the airplane that has the operating engine(s). Simulator tests of several airplanes with no flight control surfaces operating and all engines out on the left wing have all shown positive control capability within the available range of lateral center-of-gravity offset. Propulsion-controlled aircraft systems that can operate without modifications to engine control systems, thus allowing PCA technology to be installed on less capable airplanes or at low cost, are also desirable. Further studies have examined simplified 'PCA Lite' and 'PCA Ultralite' concepts in which thrust control is provided by existing systems such as auto-throttles or a combination of existing systems and manual pilot control.

Burcham, Frank W., Jr.↗
NASA NTRS2002

Aeroheating Predictions for the X-43 Cowl-Closed Configuration at Mach 7 and 10

A pre-flight analysis was conducted for the Mach 7 and Mach 10 X-43 cowl-closed configurations to evaluate three-dimensional flow-field effects on localized heating in the vicinity of the closed cowl flap and sidewall. First, engineering-level analyses based on documented laminar and turbulent surface heating database were used to estimate localized heating amplification factors to account for turbulent flow effects, corner flow effects and the presence of forebody boundary layer trip devices. These estimated factors were applied to 2-D computational predictions to develop surface heat loads. Second, thin-film gauge surface heating data were obtained for a Mach 10 cowl-closed configuration in a reflected shock tunnel at simulated flight conditions. Third, computational fluid dynamics (CFD) flow-field predictions were obtained at Mach 10 ground test conditions to provide comparisons with the engineering database predictions and experimental measurements. Similarly, a CFD solution was also obtained at Mach 7 flight conditions to provide qualitative comparisons with engineering predictions. The Mach 10 CFD predictions compare favorably with the experimental measurements and the engineering estimates for surface heating amplification on the closed cowl. However, experimental measurements were not of sufficient quantity on the sidewall surface to capture the highest localized heating rates, and also the Mach 10 CFD predictions suggest higher peak heating on the sidewall compared to the engineering estimates. Also, the Mach 7 CFD predictions indicate qualitative agreement with the database estimates in terms of flow-field structure and peak heating locations on the closed-cowl flap and sidewall surfaces.

Cockrell, Charles E., Jr.↗
NASA NTRS1984

Circulation control technology applied to propulsive high lift systems

Technology developed for the Circulation Control Wing high-lift system has been extended to augment lift by entraining and redirecting engine thrust. Ejecting a thin jet sheet tangentially over a small curved deflecting surface adjacent to the slipstream of a turbofan engine causes the slipstream to flow around that deflecting surface. The angle of deflection is controlled pneumatically by varying the momentum of the thin jet sheet. The downward momentum of the slipstream enhances wing lift. This concept of pneumatically deflecting the slipstream has been applied to an upper surface blowing high-lift system and to a thrust deflecting system. The capability of the pneumatic upper surface blowing system was demonstrated in a series of investigations using a wind tunnel model and the NASA Quiet Short-haul Research Aircraft (QSRA). Full-scale thrust deflections greater than 90 deg were achieved. This mechanically simple system can provide increased maneuverability, heavy lift or overload capability, or short takeoff and landing performance.

Englar, R. J.↗
NASA NTRS1973

Wind tunnel investigation of a large-scale 25 deg swept-wing jet transport model with an external blowing triple-slotted flap

An investigation has been conducted to determine the aerodynamic characteristics of a large-scale subsonic jet transport model with an externally blown triple-slotted flap. The lift of the model was augmented by the turbofan engine exhaust impingement on the flap surface. The model had a 25 deg swept wing of aspect ratio 7.28 and four turbofan engines. The model was tested with two flap extents. One extended from 0.11 to 1.00 of the wing semispan, and the other extended from 0.11 to 0.75 of the wing semispan with a single-slotted aileron from 0.75 to 1.00 of the wing semispan. The results were obtained for several flap deflections with and without the horizontal tail at gross thrust coefficients from 0 to 4.0. Longitudinal and lateral data are presented with three and four engines operating.

Aoyagi, K.↗
NASA NTRS1985

The Construction of Curves and Surfaces Using Numerical Optimization Techniques

Numerical optimization techniques are playing an increasing role in curve and surface construction. Often difficult problems in curve and surface construction, especially when some aspect of shape control is involved, can be phrased as a constrained optimization problem. Four such classes of problems are explored: parametric curve fitting with non-linear shape constraints; explicit surface fitting with linear shape constraints; surface fitting to scattered data giving rise to ill-posed problems; finally, variable knot problems. In each of these problems there is a nonlinear aspect: either the shape of the curve or surface is important for manufacturing or engineering reasons or the shape affects the convergence of numerical algorithms which use the curve or surface or the placement of knots affects the accuracy of the fits. In all cases the class of functions used is that of parametric spline curves and tensor or direct product spline surfaces. The reason for choosing this class is that splines provide flexible models that are easily evaluated and stored. Furthermore, the B-spline representation of splines leads to convenient expressions for shape control over regions.

Ferguson, D. R.↗
NASA NTRS1985

Preliminary design study of a lateral-directional control system using thrust vectoring

A preliminary design of a lateral-directional control system for a fighter airplane capable of controlled operation at extreme angles of attack is developed. The subject airplane is representative of a modern twin-engine high-performance jet fighter, is equipped with ailerons, rudder, and independent horizontal-tail surfaces. Idealized bidirectional thrust-vectoring engine nozzles are appended to the mathematic model of the airplane to provide additional control moments. Optimal schedules for lateral and directional pseudo control variables are calculated. Use of pseudo controls results in coordinated operation of the aerodynamic and thrust-vectoring controls with minimum coupling between the lateral and directional airplane dynamics. Linear quadratic regulator designs are used to specify a preliminary flight control system to improve the stability and response characteristics of the airplane. Simulated responses to step pilot control inputs are stable and well behaved. For lateral stick deflections, peak stability axis roll rates are between 1.25 and 1.60 rad/sec over an angle-of-attack range of 10 deg to 70 deg. For rudder pedal deflections, the roll rates accompanying the sideslip responses can be arrested by small lateral stick motions.

Lallman, F. J.↗
DOE OSTI2020

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi 2 Te 4 and MnBi 4 Te 7 by Defect Engineering and Chemical Doping

MnBi 2 Te 4 and MnBi 4 Te 7 are intrinsic antiferromagnetic topological insulators, offering a promising materials platform for realizing exotic topological quantum states. However, high densities of intrinsic defects in these materials not only cause bulk metallic conductivity, preventing the measurement of quantum transport in surface states, but may also affect magnetism and topological properties. In this paper, systematic density functional theory calculations reveal specific material chemistry and growth conditions that determine the defect formation and dopant incorporation in MnBi 2 Te 4 and MnBi 4 Te 7 . The large strain induced by the internal heterostructure promotes the formation of large-size-mismatched antisite defects and substitutional dopants. The results here show that the abundance of antisite defects is responsible for the observed n-type metallic conductivity. Additionally, a Te-rich growth condition is predicted to reduce the bulk free electron density, which is confirmed by experimental synthesis and transport measurements in MnBi 2 Te 4 . Furthermore, Na doping is proposed to be an effective acceptor dopant to pin the Fermi level within the bulk band gap to enable the observation of surface quantum transport. The defect engineering and doping strategies proposed here should stimulate further studies for improving synthesis and for manipulating magnetic and topological properties in MnBi 2 Te 4 , MnBi 4 Te 7 , and related magnetic topological insulators.

36 MATERIALS SCIENCE↗
NASA NTRS1977

Static and wind-on tests of an upper-surface-blown jet-flap nozzle arrangement for use on the Quiet Clean Short-haul Experimental Engine (QCSEE)

The internal aerodynamic performance, the static turning characteristics, and the forward-speed characteristics of two 1/12-scale upper surface-blown jet-flap exhaust-nozzle arrangements designed for use on the Quiet Clean Short-Haul Experimental Engine (QCSEE) were investigated. The nozzles were equipped with interchangeable area-control side doors in the aft sidewalls of the nozzle so that the effective nozzle area could be varied over a wide range. A simulated wing was used to evaluate installation losses for the nozzles. A smoothly curved flap was attached to the trailing edge of the simulated wing to allow an evaluation of the static turning characteristics of the nozzle arrangement. Forward-speed effects on the jet turning characteristics of the QCSEE nozzles were evaluated by mounting a single engine on a semispan wing designed to be representative of a four-engine STOL transport configuration.

Phelps, A. E., III↗
NASA NTRS1992

Hybrid laminar flow control applied to advanced turbofan engine nacelles

The potential application of hybrid laminar flow control (HLFC) to the external surface of an advanced, high bypass ratio turbofan engine nacelle with a wetted area that approaches 15 percent of the wing total wetted area of future commercial transports is presented. A pressure distribution compatible with HLFC is specified and the corresponding nacelle geometry is computed employing a predictor/corrector design technique. Performance evaluations on an advanced twin-engine transport configuration are discussed to determine potential benefits in terms of reduced fuel consumption.

Collier, F. S., Jr.↗
NASA NTRS1997

Fatigue Reliability of Gas Turbine Engine Structures

The results of an investigation are described for fatigue reliability in engine structures. The description consists of two parts. Part 1 is for method development. Part 2 is a specific case study. In Part 1, the essential concepts and practical approaches to damage tolerance design in the gas turbine industry are summarized. These have evolved over the years in response to flight safety certification requirements. The effect of Non-Destructive Evaluation (NDE) methods on these methods is also reviewed. Assessment methods based on probabilistic fracture mechanics, with regard to both crack initiation and crack growth, are outlined. Limit state modeling techniques from structural reliability theory are shown to be appropriate for application to this problem, for both individual failure mode and system-level assessment. In Part 2, the results of a case study for the high pressure turbine of a turboprop engine are described. The response surface approach is used to construct a fatigue performance function. This performance function is used with the First Order Reliability Method (FORM) to determine the probability of failure and the sensitivity of the fatigue life to the engine parameters for the first stage disk rim of the two stage turbine. A hybrid combination of regression and Monte Carlo simulation is to use incorporate time dependent random variables. System reliability is used to determine the system probability of failure, and the sensitivity of the system fatigue life to the engine parameters of the high pressure turbine. 'ne variation in the primary hot gas and secondary cooling air, the uncertainty of the complex mission loading, and the scatter in the material data are considered.

Cruse, Thomas A.↗