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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 235 records · Page 13

All sources NASA NTRS DOE OSTI

NASA NTRS1980

Nonlinear static TPS analysis

A nonlinear analysis which includes the effect of mismatch and filler bar was developed to predict the strain isolator pad reuseable surface insulation through-the-thickness interface stresses. Parametric studies were conducted for simulated shock loading on square tiles. Expected loads on an actual tile were also studied. The results indicate that when no mismatch is present, linear solutions tend to give nonconservative maximum stresses relative to the nonlinear solutions. When mismatch is present, the linear maximum stresses are only conservative at low load levels and highly nonconservative at high load levels. Although the presence of filler bar reduces maximum tensile stresses in some cases, it does not appear that the nominal dimension filler bar can reduce the nonlinear stress to a level at which the linear solution becomes conservative relative to the nonlinear solution. Moreover, on an outboard trailing edge elevon tile at descent with +20 deg flap, the linear analysis is 49% nonconservative relative to the nonlinear analysis with filler bar.

Housner, J. M.↗

NASA NTRS1982

Spin tests of a single-engine, high-wing light airplane

The airplane has a relatively steep spin mode (low angle of attack) with a high load factor and high velocity. The airplane recovers almost immediately after any deviation from the prospin control positions, except for one maneuver with reduced flexibility in the elevator control system.

Stewart, E. C.↗

NASA NTRS1983

Life considerations of the shuttle orbiter densified-tile thermal protection system

The Shuttle orbiter themal protection system (TPS) incorporates ceramic reusable surface insulation tiles bonded to the orbiter substructure through a strain isolation pad. Densification of the bonding surface of the tiles increases the static strength of the tiles. The densification proces does not, however, necessarily lead to an equivalent increase in fatigue strength. Investigation of the expected lifetime of densified tile TPS under both sinusoidal loading and random loading simulating flight conditions indicates that the strain isolation pads are the weakest components of the TPS under fatigue loading. The felt pads loosen under repetitive loading and, in highly loaded regions, could possibly cause excessive step heights between tiles causing burning of the protective insulation between tiles. A method of improving the operational lifetime of the TPS by using a strain isolation pad with increased stiffness is presented as is the consequence of the effect of increased stiffness on the tile inplane strains and transverse stresses.

Cooper, P. A.↗

NASA NTRS1989

Dynamic Torque Calibration Unit

Proposed dynamic torque calibration unit (DTCU) measures torque in rotary actuator components such as motors, bearings, gear trains, and flex couplings. Unique because designed specifically for testing components under low rates. Measures torque in device under test during controlled steady rotation or oscillation. Rotor oriented vertically, supported by upper angular-contact bearing and lower radial-contact bearing that floats axially to prevent thermal expansion from loading bearings. High-load capacity air bearing available to replace ball bearings when higher load capacity or reduction in rate noise required.

Agronin, Michael L.↗

NASA NTRSDate not supplied

Aerodynamic Loss Generation in a Low-Pressure Turbine Stage with High Lift Blading

Background - A joint program (FAA): Honeywell-U.S. Air Force- NASA to develop highly-loaded LPT stages Objective of current work - Application and evaluation of a High-Fidelity numerical simulation for flow field in a highly loaded LPT stage. 1. loss generation mechanism. 2. Reynolds number effects on stage performance

low pressure turbine↗

DOE OSTI2022

Atomically Dispersed Pentacoordinated‐Zirconium Catalyst with Axial Oxygen Ligand for Oxygen Reduction Reaction

Single-atom catalysts (SACs), as promising alternatives to Pt-based catalysts, suffer from the limited choice of center metals and low single-atom loading. Here, we report a pentacoordinated Zr-based SAC with nontrivial axial O ligands (denoted O-Zr-N-C) for oxygen reduction reaction (ORR). The O ligand downshifts the d-band center of Zr and confers Zr sites with stable local structure and proper adsorption capability for intermediates. Consequently, the ORR performance of O-Zr-N-C prominently surpasses that of commercial Pt/C, achieving a half-wave potential of 0.91 V vs. reversible hydrogen electrode and outstanding durability (92% current retention after 130-hour operation). Moreover, the Zr site shows good resistance towards aggregation, enabling the synthesis of Zr-based SAC with high loading (9.1 wt%). With the high-loading catalyst, the zinc-air battery (ZAB) delivers a record-high power density of 324 mW cm -2 among those of SAC-based ZABs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Switching Modes for Reduction of Peak Voltage Transients in GaN-Based Three Level ANPC Inverter

The switching pole voltage can transition between P,0, and N states in a three-level active neutral point clamped (ANPC) inverter. State transitions between 0-P and 0-N can be realized with different switching modes. Three switching modes- Short 1 , Short 2 , and Full are studied considering the effect of capacitive current paths. The role of clamping and inner switch on/off conditions is determined using simplified equivalent circuit models. Short 2 with clamping switch off is beneficial for turn-on overvoltage suppression but results in high turn-off overvoltage. Full mode with a parallel current sharing path is effective for turn-off overvoltage suppression but leads to high turn-on overvoltage. Hence, a Modified Full mode is proposed to achieve the simultaneous objective of overvoltage suppression at both turn-on and turn-off transient during high load currents. This benefits 3L ANPC operation at a low power factor with a high load current at fundamental voltage zero crossing points. Here, a 650V GaN-based three-level ANPC inverter prototype is designed and used to evaluate the switching modes and overvoltage suppression strategies through double pulse tests and continuous operation.

42 ENGINEERING↗

DOE OSTI2025

Fuel Property Effects on Stochastic Preignition Events During Engine Load Transitions

Stochastic preignition (SPI) is an abnormal combustion phenomenon that can cause catastrophic engine damage. There have been several proposed mechanisms of SPI, where a uniform source is still not certain, however, SPI tendencies have been shown to be influenced by engine operating conditions, oil composition, engine age, and fuel chemical and physical properties. Laboratory research and testing for SPI propensity is challenging given the stochastic nature of events, as well as the potential for significant degradation of the engine platform and measuring equipment over time. Thus, SPI specific experiments are generally conducted under either sustained or cyclic patterning of steady-state operating conditions to avoid the influence of transient engine boundary conditions on test parameters of interest (e.g. oil additive package, fuel properties, engine speed/load, etc.). In this work a cyclically varying SPI test sequence involves a 5 min engine warmup period at a low engine load of around 4 bar gross indicated mean effective pressure (IMEPg), followed by a transition to high load (~20 bar IMEPg) at a constant 2000 rev/min engine speed for a total of 25 min. This individual test sequence load schedule is then sequentially repeated 10 times to generate significant statistical data for analysis. This work examines the influence of fuel chemical and physical properties on SPI tendency during the unsteady portion of the 10-cycle sequence (the first 5 min of the high load operation in each sequence of the loading cycle) which has been discarded from previous analyses due to the uncertainty in engine operating and thermal boundary conditions. Results from this analysis suggest an increasing trend in the ratio of SPI events during the unsteady test period relative to the steady test period with increasing fuel Reid Vapor Pressure (RVP), implying differences in uncontrolled ignition source terms, possibly from, fuel wall interactions and retention during the load transition phase of the test.

Splitter, Derek [ORNL] (ORCID:0000000174044047)↗

NASA NTRS2012

Effects of Radiation and a High Iron Load on Bone Mineral Density

Astronauts on long duration space flight missions to the moon or mars are exposed to radiation and have increase iron (Fe) stores, both of which can independently induce oxidative stress and may exacerbate bone mass loss and strength. We hypothesize a high Fe diet and a fractionated gamma radiation exposure would increase oxidative stress and lower bone mass. Three mo-old, SD rats (n=32) were randomized to receive an adequate Fe diet (45 mg Fe/kg diet) or a high Fe diet (650 mg Fe/kg diet) for 4 wks and either a cumulative 3 Gy dose (fractionated 8 x 0.375 Gy) of gamma radiation (Cs-137) or sham exposure starting on day 14. Elisa kit assessed serum catalase, clinical analyzer assessed serum Fe status and ex vivo pQCT scans measured bone parameters in the proximal/midshaft tibia and femoral neck. Mechanical strength was assessed by 3-pt bending and femoral neck test. There is a significant decrease in trabecular bone mineral density (BMD) from radiation (p less than 0.05) and a trend in diet (p=0.05) at the proximal tibia. There is a significant interaction in cortical BMD from the combined treatments at the midshaft tibia (p less than 0.05). There is a trending decrease in total BMD from diet (p=0.07) at the femoral neck. In addition, high serum Fe was correlated to low trabecular BMD (p less than 0.05) and high serum catalase was correlated to low BMD at all 3 bone sites (p less than 0.05). There was no difference in the max load of the tibia or femoral neck. Radiation and a high iron diet increases iron status and catalase in the serum and decreases BMD.

Yuen, E.↗

DOE OSTI2021

Fuel Effects on Advanced Compression Ignition Load Limits

In order to increase the efficiency of light-duty gasoline engines, the Co-Optimization of Fuels and Engines (Co-Optima) initiative from the U.S. Department of Energy is investigating multi-mode combustion strategies. Multi-mode combustion can be describe as using conventional spark-ignited combustion at high loads, and at the part-load operating conditions, various advanced compression ignition (ACI) strategies are being investigated to increase efficiency. Of particular interest to the Co-Optima initiative is the extent to which optimal fuel properties and compositions can enable higher efficiency ACI combustion over larger portions of the operating map. Extending the speed-load range of these ACI modes can enable greater part-load efficiency improvements for multi-mode combustion strategies. In this manuscript, we investigate fuel effects for six different fuels, including four with a research octane number (RON) of 98 and differing fuel chemistries, iso-octane, and a market representative E10 fuel, on the load limits for two different ACI strategies: spark-assisted compression ignition (SACI) and partial fuel stratification-gasoline compression ignition (PFS-GCI) operation. Experimental results show that limits to intake boosting limit high load operation for most fuels, but high smoke emissions for high particulate matter index (PMI) fuels under SACI conditions could also be a limitation. Contrastingly, low load is limited by combustion efficiency, but these effects have more pronounced variation with fuel chemistry for PFS-GCI than with SACI. Additional, distinct effects affecting autoignition timing and peak heat release at higher speeds were identified for fuels having different low temperature heat release (LTHR) propensities for both ACI modes.

33 ADVANCED PROPULSION SYSTEMS↗

NASA NTRSDate not supplied

Dry Pressed, High Areal Loading Electrode Architectures Enabled by Holey Graphene

For future electric aviation, advanced battery cell chemistry beyond lithium ion batteries are required to meet mission requirements. High energy density battery concepts such as lithium-sulfur (Li-S) and lithiumoxygen (Li-O2) chemistries are being intensively investigated to realize their extraordinary theoretical promise in terms of energy density. Most fabrication methods of cathodes for these novel battery chemistries followed a conventional approach. In this approach, the active material is mixed with a polymer binder and a conductive carbon in a high-boiling organic solvent to form a slurry, followed by casting onto a current collector and solvent evaporation. The process is usually lengthy and poses environmental hazards due to the use of organic solvents.

Lin Yi↗

DOE OSTI2021

Avoiding surface instability and slurry jamming in simultaneous multilayer coating of structured particulate films

Simultaneous multilayer coating techniques are widely known, but their industrial application remains limited to narrow market sectors. One barrier to adoption may be the mismatch between industries that are familiar with such processes but have no need, and industries that have need but are not familiar. Moreover, there are application-specific technical challenges to developing multilayer-coating processes. In this article, we describe our resolution of two specific issues in simultaneous multilayer coating of all aqueous highly loaded slurries for new and emerging energy applications. The first issue is particle jamming (associated with Shear-thickening) of the highly loaded slurries in the die internals, which we alleviated by adding small amounts of viscosity modifiers without reducing the solid loading. The second issue is a Marangoni-driven surface instability that resembles top layer de-wetting, which we solved by carefully selecting surfactants to tune the dynamic surface tensions of each slurry. Both issues were resolved early in a step-wise development, saving significant development cost which in our case was driven by expensive materials.

08 HYDROGEN↗

DOE OSTI2024

Upcycling linear low-density polyethylene waste to turbostratic graphene for high mass loading supercapacitors

Linear low-density polyethylene (LLDPE) waste is difficult to upcycle into more valuable carbon materials because it tends to completely decompose into small molecules during thermal processing. In this work, LLDPE is upcycled into a high quality turbostratic graphene using a pre-treatment step to oxidatively crosslink the polymer with the assistance of solid additives (KCl and K 2 CO 3 ) that improve crosslinking by increasing the effective surface area of the polymer melt during processing. After this pretreatment step, the crosslinked polymer could then be carbonized and catalytically graphenized between 400–950°C without decomposition of the polymer feedstock. The LLDPE derived graphene (LLDPE-G) obtained from this process has a Brunauer–Emmett–Teller (BET) specific surface area, up to 1800m 2 g -1 and average Raman I D /I G and I 2D /I G ratios of 0.85 and 0.57, respectively, indicating high quality graphene. When used as an electrode material in symmetric supercapacitors, LLDPE-G possesses a specific capacitance up to 175Fg -1 at a mass loading of 20mgcm -2 , which is two times the commercial requirement, yielding an areal capacitance of 3.5 Fcm -2 . Moreover, LLDPE-G exhibits exceptional cycling stability with a capacitance retention of 95.8 % after 100,000 cycles at a current density of 4.0 Ag -1 . Additionally, the KCl and K 2 CO 3 solids are recycled and reused over 3 complete reaction cycles to make new LLDPE-G with the material quality and electrocapacitive performance retained and verified after each cycle. Our approach creates new opportunities for upcycling waste LLDPE and other varieties of polyethylene into a higher value graphene used for electrochemical energy storage applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

MoS 2 nanosheet integrated electrodes with engineered 1T-2H phases and defects for efficient hydrogen production in practical PEM electrolysis

Low electrical conductivity and poor accessibility of MoS 2 reaction sites raise great challenges in maximizing the triple-phase-boundary (TPB) sites of MoS 2 -based electrodes and minimizing ohmic losses for efficient hydrogen evolution reaction (HER) in practical proton exchange membrane (PEM) water electrolysis. Herein, we report a scalable hydrothermal approach to fabricate ionomer-free integrated electrodes with engineered 1 T-2 H heterophase and defect-rich MoS 2 nanosheets (MoS 2 NSs) in-situ grown onto the carbon fiber paper (CFP). With an ultralow loading of 0.14 mg/cm 2 , a small voltage of 2.25 V was obtained at 2000 mA/cm 2 in a practical cell with Nafion115 membrane, which outperforms all previously reported high-loading non-precious catalyst-based electrodes. Impressively, it shows 44 times higher mass activity than a high-loading and ionomer-mixed MoS 2 assemblies electrode. Furthermore, this work builds a bridge from catalyst optimization to electrode fabrication and provides a promising direction for improving intrinsic catalytic activity, electrode conductivity and stability for practical PEM water electrolysis.

1T-2H heterophase↗

DOE OSTI2024

Upcycling Linear Low-Density Polyethylene Waste into Graphene for High Mass Loading Supercapacitors

Polyethylene is notoriously difficult to upcycle because it decomposes into light gases at approximately 350-400 °C which prevents processing it at higher temperatures to convert it into electrode materials. We address this challenge by using an air-based, thermos-oxidative process, which heats linear low-density polyethylene (LLDPE) just below the decomposition point to initiate oxidation and cross-linking of LLDPE alkyl chains. These molecular transformations allow LLDPE to be graphenized at 950 °C without decomposing. The LLDPE-derived graphene (LLDPE-G) has a BET specific surface area up to 1,800 m2/g and Raman ID/IG ratio of 0.85. When used as electrode material for a symmetric supercapacitor with the 1 M H2SO4 electrolyte, LLDPE-G possesses an specific capacitance up to 175 F/g at mass loading of 20 mg/cm2, yielding an areal capacitance of 3.5 F/cm2. The cycling stability with capacitance demonstrates a retention of 95.8% after 100,000 cycles at high current density of 4.0 A/g.

Gao, Yuan↗

NASA NTRS2002

Aerodynamic Design Study of Advanced Multistage Axial Compressor

As a direct response to the need for further performance gains from current multistage axial compressors, an investigation of advanced aerodynamic design concepts that will lead to compact, high-efficiency, and wide-operability configurations is being pursued. Part I of this report describes the projected level of technical advancement relative to the state of the art and quantifies it in terms of basic aerodynamic technology elements of current design systems. A rational enhancement of these elements is shown to lead to a substantial expansion of the design and operability space. Aerodynamic design considerations for a four-stage core compressor intended to serve as a vehicle to develop, integrate, and demonstrate aerotechnology advancements are discussed. This design is biased toward high efficiency at high loading. Three-dimensional blading and spanwise tailoring of vector diagrams guided by computational fluid dynamics (CFD) are used to manage the aerodynamics of the high-loaded endwall regions. Certain deleterious flow features, such as leakage-vortex-dominated endwall flow and strong shock-boundary-layer interactions, were identified and targeted for improvement. However, the preliminary results were encouraging and the front two stages were extracted for further aerodynamic trimming using a three-dimensional inverse design method described in part II of this report. The benefits of the inverse design method are illustrated by developing an appropriate pressure-loading strategy for transonic blading and applying it to reblade the rotors in the front two stages of the four-stage configuration. Multistage CFD simulations based on the average passage formulation indicated an overall efficiency potential far exceeding current practice for the front two stages. Results of the CFD simulation at the aerodynamic design point are interrogated to identify areas requiring additional development. In spite of the significantly higher aerodynamic loadings, advanced CFD-based tools were able to effectively guide the design of a very efficient axial compressor under state-of-the-art aeromechanical constraints.

Larosiliere, Louis M.↗

NASA NTRS1989

Hubble Space Telescope-Space Shuttle interface dynamic verification test

A test program has been developed for the interface between the Space Shuttle Orbiter and the Hubble Space Telescope which couples a standard modal test for a simple suspended structure with a novel, 'interface verification' test. While the free-free modal test is used to verify the high loads generating structural modes due to the interaction of internal components of the structure with the rest of the structure, the interface verification test verifies the character of the high-loading generating modes in which the structure reacts against the booster interface. The novel method excites the structure at a single payload-booster interface DOF, while all other interfaces are left free to move.

Blair, Mark A.↗

NASA NTRSDate not supplied

Flight Performance Estimates for the NASA X-57 Distributed Electric Propulsion Flight Demonstrator

The X-57 flight demonstrator concept featured four configurations starting with a conventional combustion-powered multiengine airplane and ending with a fully electric configuration with two forms of distributed propulsion and a highly modified wing. These configurations, called Mods, were designed to gain incremental insight into different aircraft propulsion configuration options and their impact on the aircraft performance. The gasoline-powered Mod I configuration consumed 2.6 to 2.9 times more stored energy in cruise than the electric but otherwise conventionally configured Mod II configuration. The highly loaded wing of Mod III led to an increase of 40% in the power-off lift-to-drag ratio as compared to Mod II at the project high-speed cruise target speed and altitude. The power-on lift-to-drag ratio of Mod III was 53% higher than Mod II due to the beneficial aero-propulsive interaction of the wingtip-mounted cruise propellers in Mod III. The high-lift propeller system of Mod IV recovered the low-speed performance of the conventional configuration in Mod II that was otherwise lost with the introduction of the highly loaded Mod III wing. The battery-electric configurations also benefitted from a lack of power lapse in the electric motors with increasing air density as compared to the combustion-powered baseline aircraft.

Distributed Performance↗