A METHOD FOR COMPUTING THE EFFECT OF AN ADDITIONAL OBSERVATION ON A PREVIOUS LEAST-SQUARES ESTIMATE
A data reduction method for computing effect of additional observation on previous least-squares estimates
DATA REDUCTION↗
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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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Amorphization as a Pathway to Fast Charging Kinetics in Atomic Layer Deposition-Derived Titania Films for Lithium Ion Batteries
Abstract not provided
25 ENERGY STORAGE↗
Reduction of noise from a fan stage for a turbofan engine by use of long-chord acoustically-treated stator vanes
A set of acoustically-treated long-chord vanes was designed to replace the vanes in an existing fan stage to investigate the noise reduction possibilities of both increased stator chord length and this method of incorporating acoustic damping material. The vanes were tested with both active and inactive acoustic surfaces. The inactive tests showed significant broadband noise effects with noise reductions in the middle to high frequencies and an increase at low frequencies. No reduction in blade passage tone was observed, but decreases in the overtones were observed. The tests with the active acoustic treatment showed large noise reductions over a wide frequency range.
Dittmar, J. H.↗
Taking some heat off the NDCs? The limited potential of additional short-lived climate forcers’ mitigation
Several studies have shown that the greenhouse gas reduction resulting from the current nationally determined contributions (NDCs) will not be enough to meet the overall targets of the Paris Climate Agreement. It has been suggested that more ambition mitigations of short-lived climate forcer (SLCF) emissions could potentially be a way to reduce the risk of overshooting the 1.5 or 2 °C target in a cost-effective way. In this study, we employ eight state-of-the-art integrated assessment models (IAMs) to examine the global temperature effects of ambitious reductions of methane, black and organic carbon, and hydrofluorocarbon emissions. The SLCFs measures considered are found to add significantly to the effect of the NDCs on short-term global mean temperature (GMT) (in the year 2040: -0.03 to -0.15 °C) and on reducing the short-term rate-of-change (by -2 to 15%), but only a small effect on reducing the maximum temperature change before 2100. This, because later in the century under assumed ambitious climate policy, SLCF mitigation is maximized, either directly or indirectly due to changes in the energy system. All three SLCF groups can contribute to achieving GMT changes.
54 ENVIRONMENTAL SCIENCES↗
Multifunctional Charge and Hydrogen‐Bond Effects of Second‐Sphere Imidazolium Pendants Promote Capture and Electrochemical Reduction of CO 2 in Water Catalyzed by Iron Porphyrins**
Abstract Microenvironments tailored by multifunctional secondary coordination sphere groups can enhance catalytic performance at primary metal active sites in natural systems. Here, we capture this biological concept in synthetic systems by developing a family of iron porphyrins decorated with imidazolium (im) pendants for the electrochemical CO 2 reduction reaction (CO 2 RR), which promotes multiple synergistic effects to enhance CO 2 RR and enables the disentangling of second‐sphere contributions that stem from each type of interaction. Fe‐ ortho ‐im(H) , which poises imidazolium units featuring both positive charge and hydrogen‐bond capabilities proximal to the active iron center, increases CO 2 binding affinity by 25‐fold and CO 2 RR activity by 2000‐fold relative to the parent Fe tetraphenylporphyrin ( Fe‐TPP ). Comparison with monofunctional analogs reveals that through‐space charge effects have a greater impact on catalytic CO 2 RR performance compared to hydrogen bonding in this context.
Narouz, Mina R.↗
Reduction of Noise from a Fan Stage for a Turbofan Engine by Use of Long-Chord Acoustically-Treated Stator Vanes
A set of acoustically-treated long-chord vanes was designed to replace the vanes in an existing fan stage to investigate the noise reduction possibilities of both increased stator chord length and a method of incorporating acoustic damping material. The vanes were tested with both active and inactive acoustic surfaces. Results of the inactive tests show significant broadband noise effects with noise reductions in the middle to high frequencies and an increase at low frequencies. No reduction in blade passage tone was observed, but decreases in the overtones were observed. Results of the tests with the active acoustic treatment show large noise reductions over a wide frequency range.
Dittmar, J. H.↗
Advanced latent heat of fusion thermal energy storage for solar power systems
The use of solar thermal power systems coupled with thermal energy storage (TES) is being studied for both terrestrial and space applications. In the case of terrestrial applications, it was found that one or two hours of TES could shift the insolation peak (solar noon) to coincide with user peak loads. The use of a phase change material (PCM) is attractive because of the higher energy storage density which can be achieved. However, the use of PCM has also certain disadvantages which must be addressed. Proof of concept testing was undertaken to evaluate corrosive effects and thermal ratcheting effects in a slurry system. It is concluded that the considered alkali metal/alkali salt slurry approach to TES appears to be very viable, taking into account an elimination of thermal ratcheting in storage systems and the reduction of corrosive effects. The approach appears to be useful for an employment involving temperatures applicable to Brayton or Stirling cycles.
Phillips, W. M.↗
Multifunctional Charge and Hydrogen-Bond Effects of Second-Sphere Imidazolium Pendants Promote Capture and Electrochemical Reduction of CO 2 in Water Catalyzed by Iron Porphyrins
Microenvironments tailored by multifunctional secondary coordination sphere groups can enhance catalytic performance at primary metal active sites in natural systems. In this work, we capture this biological concept in synthetic systems by developing a family of iron porphyrins decorated with imidazolium (im) pendants for the electrochemical CO 2 reduction reaction (CO 2 RR), which promotes multiple synergistic effects to enhance CO 2 RR and enables the disentangling of second-sphere contributions that stem from each type of interaction. Fe-ortho-im(H), which poises imidazolium units featuring both positive charge and hydrogen-bond capabilities proximal to the active iron center, increases CO 2 binding affinity by 25-fold and CO 2 RR activity by 2000-fold relative to the parent Fe tetraphenylporphyrin (Fe-TPP). Comparison with monofunctional analogs reveals that through-space charge effects have a greater impact on catalytic CO 2 RR performance compared to hydrogen bonding in this context.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Interior noise reduction in a large civil helicopter
The results of an evaluation of the effectiveness of current noise reduction technology in attaining acceptable levels of interior noise in a large (about 20,000 kg) passenger-carrying helicopter are presented. The helicopter studied is a modified CH-53A with a specially designed, acoustically treated passenger cabin. The acoustic treatment reduced the average A-weighted interior noise levels from 115 db to 87 db. The study suggests selected improvements in the acoustic treatment which could result in additional reduction in cabin noise levels. The resulting levels would be only slightly greater than the interior noise levels of current narrow-body jet transports.
Howlett, J. T.↗
Investigation of the effect of ceramic coatings on rocket thrust chamber life
Two cylindrical rocket thrust chamber cylinders were coated with a 0.203 mm layer of zirconium oxide using a process that employed electrodeposition of metal to a spray-coated mandrel. The cylinders were cyclically tested using hydrogen-oxygen propellants at a nominal chamber pressure of 4.14 MN/sq m to show the effect of the coating on life. Both cylinders failed prematurely due to causes unrelated to the coatings. Post destructive analysis showed no cooling passage wall deformation. Where erosion of the coating occurred, the coating thickness stabilized at 0.061 mm within 80 cycles and remained well adhered throughout the tests. The hot-gas-side metal wall temperature and the theoretical maximum effective strain were reduced by 80 and 92%, respectively, where the coating was 0.203 mm thick and by 40 and 50%, respectively, where the coating was 0.061 mm thick compared to an uncoated cylinder. The 50 and 92% reductions in maximum effective strain resulted in theoretical lives of 1900 cycles and greater than 10,000 cycles, respectively, compared to 300 cycles for the uncoated cylinder.
Quentmeyer, R. J.↗
Fatigue failure of regenerator screens in a high frequency Stirling engine
Failure of Stirling Space Power Demonstrator Engine (SPDE) regenerator screens was investigated. After several hours of operation the SPDE was shut down for inspection and on removing the regenerator screens, debris of unknown origin was discovered along with considerable cracking of the screens in localized areas. Metallurgical analysis of the debris determined it to be cracked-off-deformed pieces of the 41 micron thickness Type 304 stainless steel wire screen. Scanning electron microscopy of the cracked screens revealed failures occurring at wire crossovers and fatigue striations on the fracture surface of the wires. Thus, the screen failure can be characterized as a fatigue failure of the wires. The crossovers were determined to contain a 30 percent reduction in wire thickness and a highly worked microstructure occurring from the manufacturing process of the wire screens. Later it was found that reduction in wire thickness occurred because the screen fabricator had subjected it to a light cold-roll process after weaving. Installation of this screen left a clearance in the regenerator allowing the screens to move. The combined effects of the reduction in wire thickness, stress concentration (caused by screen movement), and highly worked microstructure at the wire crossovers led to the fatigue failure of the screens.
Hull, David R.↗
Fatigue failure of regenerator screens in a high frequency Stirling engine
Failure of Stirling Space Power Demonstrator Engine (SPDE) regenerator screens was investigated. After several hours of operation the SPDE was shut down for inspection and on removing the regenator screens, debris of unknown origin was discovered along with considerable cracking of the screens in localized areas. Metallurgical analysis of the debris determined it to be cracked-off-deformed pieces of the 41 micron thickness Type 304 stainless steel wire screen. Scanning electron microscopy of the cracked screens revealed failures occurring at wire crossovers and fatigue striations on the fracture surface of the wires. Thus, the screen failure can be characterized as a fatigue failure of the wires. The crossovers were determined to contain 30 percent reduction in wire thickness and a highly worked microstructure occurring from the manufacturing process of the wire screens. Later it was found that reduction in wire thickness occurred because the screen fabricator had subjected it to a light cold-roll process after weaving. Installation of this screen left a clearance in the regenerator allowing the screens to move. The combined effects of the reduction in wire thickness, stress concentration (caused by screen movement), and highly worked microstructure at the wire crossovers led to the fatigue failure of the screens.
Hull, David R.↗
Aerodynamic Characteristics of a Four-Propeller Tilt-Wing VTOL Model with Twin Vertical Tails, Including Effects of Ground Proximity
Results are presented of a wind-tunnel investigation of the aerodynamic stability, control, and performance characteristics of a model of a four-propeller tilt-wing VTOL airplane employing flaps and speed brakes through the transition speed range. The results indicate that the wing was stalled for steady level flight for all conditions of the investigation; however, the flapped configuration did produce a higher maximum lift. The effectiveness of the flap in delaying the stall in the present investigation was not as great as in some previous investigations because the flap used was smaller than that used previously. The wing stall resulted in an appreciable reduction of aileron effectiveness during the transition. Out of ground effect the low horizontal tail did not appear to be in an adverse flow field as had been expected and showed no erratic changes in effectiveness; however, in ground effect a large nose-down moment was experienced by the model. In general, the lateral aerodynamic data indicate that the configuration is directionally stable and possesses positive dihedral effect throughout the transition, and the data show no signs of erratic flow at the vertical tails.
Grunwald, Kalman J.↗
Synergistic Porosity and Charge Effects in a Supramolecular Porphyrin Cage Promote Efficient Photocatalytic CO 2 Reduction**
We present a supramolecular approach to catalyzing photochemical CO 2 reduction through second-sphere porosity and charge effects. An iron porphyrin box (PB) bearing 24 cationic groups, FePB-2(P), was made via post-synthetic modification of an alkyne-functionalized supramolecular synthon. FePB-2(P) promotes the photochemical CO 2 reduction reaction (CO 2 RR) with 97 % selectivity for CO product, achieving turnover numbers (TON) exceeding 7000 and initial turnover frequencies (TOF max ) reaching 1400 min -1 . The cooperativity between porosity and charge results in a 41-fold increase in activity relative to the parent Fe tetraphenylporphyrin (FeTPP) catalyst, which is far greater than analogs that augment catalysis through porosity (FePB-3(N), 4-fold increase) or charge (Fe p-tetramethylanilinium porphyrin (Fe-p-TMA), 6-fold increase) alone. In conclusion, this work establishes that synergistic pendants in the secondary coordination sphere can be leveraged as a design element to augment catalysis at primary active sites within confined spaces.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Wind-Tunnel Investigation of Effects of Unsymmetrical Horizontal-Tail Arrangements on Power-on Static Longitudinal Stability of a Single-Engine Airplane Model
A wind-tunnel investigation has been made to determine the effects of unsymmetrical horizontal-tail arrangements on the power-on static longitudinal stability of a single-engine single-rotation airplane model. Although the tests and analyses showed that extreme asymmetry in the horizontal tail indicated a reduction in power effects on longitudinal stability for single-engine single-rotation airplanes, the particular "practical" arrangement tested did not show marked improvement. Differences in average downwash between the normal tail arrangement and various other tail arrangements estimated from computed values of propeller-slipstream rotation agreed with values estimated from pitching-moment test data for the flaps-up condition (low thrust and torque) and disagreed for the flaps-down condition (high thrust and torque). This disagreement indicated the necessity for continued research to determine the characteristics of the slip-stream behind various propeller-fuselage-wing combinations. Out-of-trim lateral forces and moments of the unsymmetrical tail arrangements that were best from consideration of longitudinal stability were no greater than those of the normal tail arrangement.
AIRFOILS - NACA 65(216-012(MOD ) - CHAR & MOMENTS ↗
Concepts for reducing exhaust emissions and fuel consumption of the aircraft piston engine
A study was made to reduce exhaust emissions and fuel consumption of a general aviation aircraft piston engine by applying known technology. Fourteen promising concepts such as stratified charge combustion chambers, cooling cylinder head improvements, and ignition system changes were evaluated for emission reduction and cost effectiveness. A combination of three concepts, improved fuel injection system, improved cylinder head with exhaust port liners and exhaust air injection was projected as the most cost effective and safe means of meeting the EPA standards for CO, HC and NO. The fuel economy improvement of 4.6% over a typical single engine aircraft flight profile does not though justify the added cost of the three concepts, and significant reductions in fuel consumption must be applied to the cruise mode where most of the fuel is used. The use of exhaust air injection in combination with exhaust port liners reduces exhaust valve stem temperatures which can result in longer valve guide life. The use of exhaust port liners alone can reduce engine cooling air requirements by 11% which is the equivalent of a 1.5% increase in propulsive power. The EPA standards for CO, HC and NO can be met in the IO-520 engine using air injection alone or the Simmonds improved fuel injection system.
Rezy, B. J.↗
The effect of flue gas contaminants on electrochemical reduction of CO2 to methyl formate in a dual methanol/water electrolysis system
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Ester reduction on bifunctional metal-acid catalysts: Effect of metal to acid ratio
Not provided.
Chemistry↗