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At least 433 records · Page 24

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NASA NTRS2009

Preliminary Axial Flow Turbine Design and Off-Design Performance Analysis Methods for Rotary Wing Aircraft Engines: Applications - Part 2

In this paper, preliminary studies on two turbine engine applications relevant to the tilt-rotor rotary wing aircraft are performed. The first case-study is the application of variable pitch turbine for the turbine performance improvement when operating at a substantially lower shaft speed. The calculations are made on the 75 percent speed and the 50 percent speed of operations. Our results indicate that with the use of the variable pitch turbines, a nominal (3 percent (probable) to 5 percent (hypothetical)) efficiency improvement at the 75 percent speed, and a notable (6 percent (probable) to 12 percent (hypothetical)) efficiency improvement at the 50 percent speed, without sacrificing the turbine power productions, are achievable if the technical difficulty of turning the turbine vanes and blades can be circumvented. The second casestudy is the contingency turbine power generation for the tilt-rotor aircraft in the One Engine Inoperative (OEI) scenario. For this study, calculations are performed on two promising methods: throttle push and steam injection. By isolating the power turbine and limiting its air mass flow rate to be no more than the air flow intake of the take-off operation, while increasing the turbine inlet total temperature (simulating the throttle push) or increasing the air-steam mixture flow rate (simulating the steam injection condition), our results show that an amount of 30 to 45 percent extra power, to the nominal take-off power, can be generated by either of the two methods. The methods of approach, the results, and discussions of these studies are presented in this paper.

Chen, Shu-cheng, S.↗

NASA NTRS2014

Engineering Antifragile Systems: A Change In Design Philosophy

While technology has made astounding advances in the last century, problems are confronting the engineering community that must be solved. Cost and schedule of producing large systems are increasing at an unsustainable rate and these systems often do not perform as intended. New systems are required that may not be achieved by current methods. To solve these problems, NASA is working to infuse concepts from Complexity Science into the engineering process. Some of these problems may be solved by a change in design philosophy. Instead of designing systems to meet known requirements that will always lead to fragile systems at some degree, systems should be designed wherever possible to be antifragile: designing cognitive cyberphysical systems that can learn from their experience, adapt to unforeseen events they face in their environment, and grow stronger in the face of adversity. Several examples are presented of on ongoing research efforts to employ this philosophy.

Jones, Kennie H.↗

DOE OSTI2021

Evaluation of clear-sky and satellite-derived irradiance data for determining the degradation of photovoltaic system performance

Knowing the degradation in performance of a photovoltaic (PV) system over time is important for estimating the lifetime energy produced and the financial return. A key parameter for normalizing performance and determining degradation is the plane-of-array (POA) irradiance. Because accurate long-term POA measurements are not always readily available, three methods of providing irradiance data for determining the degradation rate of PV systems were evaluated—a method using irradiance data modeled with the Ineichen clear-sky model and monthly Linke turbidity coefficients, a method using the supplemental clear-sky irradiance data from the National Solar Radiation Data Base (NSRDB), and a method using the NSRDB solar irradiance data for both cloudy and clear-sky conditions (all-sky). The irradiance data from the three methods were evaluated using measured irradiance data from 1998 through 2018 for the seven-station SURFRAD network and for 3-, 5-, and 10-year periods that might be used for evaluating PV system performance. Only the two clear-sky methods for the 10-year periods had less uncertainty with respect to determining PV system degradation than the expected median degradation rate for PV systems of -0.5%/year to -0.6%/year. Shorter periods and the all-sky method had larger uncertainties, making their use questionable for determining the degradation rates of PV systems.

14 SOLAR ENERGY↗

NASA NTRS2013

Three-Axis Attitude Estimation With a High-Bandwidth Angular Rate Sensor

A continuing challenge for modern instrument pointing control systems is to meet the increasingly stringent pointing performance requirements imposed by emerging advanced scientific, defense, and civilian payloads. Instruments such as adaptive optics telescopes, space interferometers, and optical communications make unprecedented demands on precision pointing capabilities. A cost-effective method was developed for increasing the pointing performance for this class of NASA applications. The solution was to develop an attitude estimator that fuses star tracker and gyro measurements with a high-bandwidth angular rotation sensor (ARS). An ARS is a rate sensor whose bandwidth extends well beyond that of the gyro, typically up to 1,000 Hz or higher. The most promising ARS sensor technology is based on a magnetohydrodynamic concept, and has recently become available commercially. The key idea is that the sensor fusion of the star tracker, gyro, and ARS provides a high-bandwidth attitude estimate suitable for supporting pointing control with a fast-steering mirror or other type of tip/tilt correction for increased performance. The ARS is relatively inexpensive and can be bolted directly next to the gyro and star tracker on the spacecraft bus. The high-bandwidth attitude estimator fuses an ARS sensor with a standard three-axis suite comprised of a gyro and star tracker. The estimation architecture is based on a dual-complementary filter (DCF) structure. The DCF takes a frequency- weighted combination of the sensors such that each sensor is most heavily weighted in a frequency region where it has the lowest noise. An important property of the DCF is that it avoids the need to model disturbance torques in the filter mechanization. This is important because the disturbance torques are generally not known in applications. This property represents an advantage over the prior art because it overcomes a weakness of the Kalman filter that arises when fusing more than one rate measurement. An additional advantage over prior art is that, computationally, the DCF requires significantly fewer real-time calculations than a Kalman filter formulation. There are essentially two reasons for this: the DCF state is not augmented with angular rate, and measurement updates occur at the slower gyro rate instead of the faster ARS sampling rate. Finally, the DCF has a simple and compelling architecture. The DCF is exactly equivalent to flying two identical attitude observers, one at low rate and one at high rate. These attitude observers are exactly of the form currently flown on typical three-axis spacecraft.

Bayard, David S.↗

NASA NTRS2004

Link Design and Planning for Mars Reconnaissance Orbiter (MRO) Ka-band (32 GHz) Telecom Demonstration

NASA is planning an engineering telemetry demonstration with Mars Reconnaissance Orbiter (MRO). Capabilities of Ka-band (32 GHz) for use with deep space mission are demonstrated using the link optimization algorithms and weather forecasting. Furthermore, based on the performance of previous deep space missions with Ka-band downlink capabilities, experiment plans are developed for telemetry operations during superior solar conjunction. A general overview of the demonstration is given followed by a description of the mission planning during cruise, the primary science mission and superior conjunction. As part of the primary science mission planning the expected data return for various data optimization methods is calculated. These results indicate that, given MRO's data rates, a link optimized to use of at most two data rates, subject to a minimum availability of 90%, performs almost as well as a link with no limits on the number of data rates subject to the same minimum availability.

Ka-band↗

DOE OSTI2018

Ruthenium oxide nanostring clusters anchored Graphene oxide nanocomposites for high-performance supercapacitors application

Highlights: • GO-RuO{sub 2} nanocomposites were synthesized by simple hydrothermal method. • GO-RuO{sub 2} nanocomposites were characterized by XRD, SEM, TEM and EDS. • GO-RuO{sub 2} nanostring composite has shown a maximum specific capacitance of 859 Fg{sup −1} at the scan rate of 5 mVs{sup −1}. • GO-RuO{sub 2} nanostring composite electrode exhibits tremendous cyclic stability. - Abstract: Here, we report simple hydrothermal method for the preparation of Graphene oxide (GO) is embellished with nanostring clusters of ruthenium oxide (GO-RuO{sub 2}). The structure of the nanocomposite material was ascertained using X-ray diffraction (XRD), Raman spectroscopy, Scanning electron spectroscopy (SEM), Energy dispersive spectroscopy (EDS) and Transmission spectroscopy (TEM). The supercapacitor performance of the nanocomposites was investigated in acidic electrolyte, 1.0 M H{sub 2}SO{sub 4}, in a three-electrode setup. GO-RuO{sub 2} nanostring composite has shown a maximum specific capacitance of 859 Fg{sup −1} at the scan rate of 5 mVs{sup −1} using Cyclic voltammetry (CV) and by using Chronopotentiometry (CP) the specific capacitance towered up to 512 Fg{sup −1} at a current density of 2.5 Ag{sup −1}. Further, the material also possesses a high energy density of 246 Wh kg{sup -1}with a maximum power density of 1028 W kg{sup -1}. GO-RuO{sub 2} nanostring composite electrode exhibits tremendous cyclic stability with the specific capacitance retention of nearly 99% of the initial capacitance.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2017

Fitting of Failure Rate Data to a Closed Form Solution using Gamma-Poisson Method of Moments

Due to the responsibility and gravity of estimation of nuclear power plant failure rates, it is required that there be consistent and accurate methodology for describing the likelihood of an event occurring. However, the methodology currently employed can vary dependent on the data, as well as subjective conjecture from the expert performing the analysis. The current implementation of the empirical Bayes method to a Gamma-Poisson (GaP) distribution utilizes algorithms to solve for the parameters that do not provide consistent answers. Additionally, to achieve a distribution of the likelihood, the variance of each parameter of the GaP must be determined. There does not exist an exact solution to one of the parameters variance and is typically estimated using techniques like the Kass-Steffey adjustment. Thus a new approach to the problem is proposed, built upon the method of moments for a negative binomial, based upon the work of Bradlow. Using the method of moments approach, we are able to achieve a closed form estimation of the mean and variance for each parameter in the negative binomial distribution. Due to the relationship between the negative binominal and GaP distribution, results can be made between the distributions. The hyper-priors defined assume beta prime distribution which is appropriately informed; the results of this application translate back to the Gamma distribution for easy utilization in SAPHIRE. Additionally several cases are explored using publically available NRC data that considers zero inflated, over dispersed, and Poisson data.

Failure Rate↗

NASA NTRS1993

Absorption heat pump for space applications

In the first part, the performance of the Absorption Heat Pump (AHP) with water-sulfuric acid and water-magnesium chloride as two new refrigerant-absorbent fluid pairs was investigated. A model was proposed for the analysis of the new working pairs in a heat pump system, subject to different temperature lifts. Computer codes were developed to calculate the Coefficient of Performance (COP) of the system with the thermodynamic properties of the working fluids obtained from the literature. The study shows the potential of water-sulfuric acid as a satisfactory replacement for water-lithium bromide in the targeted temperature range. The performance of the AHP using water-magnesium chloride as refrigerant-absorbent pair does not compare well with those obtained using water-lithium bromide. The second part concentrated on the design and testing of a simple ElectroHydrodynamic (EHD) Pump. A theoretical design model based on continuum electromechanics was analyzed to predict the performance characteristics of the EHD pump to circulate the fluid in the absorption heat pump. A numerical method of solving the governing equations was established to predict the velocity profile, pressure - flow rate relationship and efficiency of the pump. The predicted operational characteristics of the EHD pump is comparable to that of turbomachinery hardware; however, the overall efficiency of the electromagnetic pump is much lower. An experimental investigation to verify the numerical results was conducted. The pressure - flow rate performance characteristics and overall efficiency of the pump obtained experimentally agree well with the theoretical model.

Nguyen, Tuan↗

NASA NTRSDate not supplied

Variance Decomposition of MEDLI2 Reconstructed Heating Using Neural Networks

The Mars Entry, Descent, and Landing Instrumentation (MEDLI2) sensor suite collected data during entry of the Mars 2020 Perseverance rover into Mars’ atmosphere. An inverse estimation of the backshell and heatshield surface aeroheating was performed, using the data from the MEDLI2 Instrumented Sensor Plugs, a network of thermocouples embedded within the thermal protection system across the aeroshell. Monte Carlo analysis was conducted to assess the sensitivity of the surface heat rate, temperature, and heat load to uncertainties in thermocouple depth and material properties. In this paper, a variance decomposition method using Sobol indices was employed to understand the relative contributions of each uncertainty parameter. Performing this analysis using results from the inverse analysis tool FIAT_Opt was found to require incredibly high computation time, and thus machine learning models were trained and evaluated as a surrogate model for FIAT_Opt. This paper demonstrates that machine learning models can be an efficient, accurate alternative to state-of-the-art inverse analysis tools like FIAT_Opt, especially for computationally-expensive processes. Using these models, the sensitivity analysis showed that uncertainties in heat capacity and thermal conductivity were the main drivers for the overall uncertainty in peak reconstructed heating and heat load.

H S Alpert↗

DOE OSTI2017

Current Efforts in Immobilized Low-Activity Waste Glass Testing to Support the Hanford Site Integrated Disposal Facility - 17119

Cleanup plans for Hanford site high-level radioactive mixed tank waste calls for separating the waste into high-level waste (HLW) and low-activity waste (LAW) fractions. The fractions will be vitrified separately at the Hanford Tank Waste Treatment and Immobilization Plant (WTP). The HLW glass will be sent to an offsite geological disposal facility while the immobilized low-activity waste (ILAW) glass will be disposed at the onsite Integrated Disposal Facility (IDF). In order to inform models used to predict the performance of ILAW glass at IDF, it is necessary to understand the corrosion behavior of the glass. In this paper, we discuss tests that account for the effects of 1) solution chemistry, 2) the ion exchange reaction, and 3) secondary phase formation on the glass dissolution rate. To quantify the effects of solution chemistry, specifically changes in pH, T, and Si concentration, the single-pass flow-through (SPFT) test method is applied. A designed set of these tests results in a set of kinetic rate law parameters that are used in a glass dissolution rate law based on transition-state theory. Furthermore, for SPFT tests with relatively high concentrations of Si, an ion exchange rate is provided. Additionally, through tests such as the pressurized unsaturated flow (PUF) test method, a suite of secondary phases can be compiled. The collection of kinetic rate law parameters, the ion exchange term, and the suite of secondary phases are provided to IDF performance assessment (PA) modelers. Lastly, we present a description of the efforts made to verify and validate the use of these parameters and secondary phases through the use of a field lysimeter present at the Hanford site. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2017

Energy levels, oscillator strengths, line strengths, and transition probabilities in Si-like ions of La XLIII, Er LIV, Tm LV, and Yb LVI

Detailed calculations using the multi-configuration Dirac–Fock (MCDF) method are carried out for the lowest 64 fine-structure levels of the 3s{sup 2}3p{sup 2}, 3s{sup 2}3p3d, 3s3p{sup 3}, 3s3p{sup 2}3d, 3s{sup 2}3d{sup 2}, and 3p{sup 4} configurations in Si-like ions of La XLIII, Er LIV, Tm LV, and Yb LVI. Energies, oscillator strengths, wavelengths, line strengths, and radiative electric dipole transition rates are given for all ions. A parallel calculation using the many-body perturbation theory (MBPT) method is also carried out to assess the present energy levels accuracy. Comparisons are performed between these two sets of energy levels, as well as with other available results, showing that they are in good agreement with each other within 0.5%. These high accuracy results can be used to the modeling and the interpretation of astrophysical objects and fusion plasmas. - Highlights: • Energy levels and E1 transition rates of Si-like ions are presented. • Breit interaction and Quantum Electrodynamics effects are discussed. • Present results should be useful in the astrophysical application and plasma modeling.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1942

Principles and methods of rating and testing centrifugal superchargers

Explore the source record for details and available documents.

SUPERCHARGERS-PRATT & WHITNEY 1830 TWIN WASP↗

NASA NTRS1990

Performance of (CoPC)n catalyst in active lithium-thionyl chloride cells

An experimental study was conducted with anode limited D size cells to characterize the performance of an active lithium-thionyl chloride (Li/SOCl2) system using the polymeric cobalt phthalocyanine, (CoPC)n, catalyst in carbon cathodes. The author describes the results of this experiment with respect to initial voltage delays, operating voltages, and capacities. The effectiveness of the preconditioning methods evolved to alleviate passivation effects on storage are also discussed. The results clearly demonstrated the superior high rate capability of cells with the catalyst. The catalyst did not adversely impact the performance of cells after active storage for up to 6 months, while retaining its beneficial influences.

Shah, Pinakin M.↗

DOE OSTI2026

Creep in multi-principal element materials –– A review

The ongoing push towards enhanced energy efficiency and reduced emissions has necessitated the creation of materials with superior performance, especially under extreme conditions. Modern industries, such as aerospace, energy production, and nuclear power, rely heavily on materials that can withstand elevated temperatures without compromising structural integrity. At these heightened temperatures, materials, even when subjected to mechanical stresses well below their yield strength, may experience slow deformation leading to eventual rupture — a phenomenon known as creep. With the expansive design space that comes with the high entropy concept and their reported excellent high temperature strength, multi-principal element materials (MPEMs) have attracted interest in the scientific community for high-temperature applications. Here, this review offers a comprehensive examination of existing studies on creep in MPEMs, which includes multi-principal element−alloys, −bulk metallic glasses, −ceramics, and −superalloys, comparing published findings on MPEMs with pure elements, traditional alloys, bulk metallic glasses, and superalloys. The sub-topics covered include a comparison among different creep-testing methods, creep mechanisms, creep exponents, creep strain rates, activation volume, and creep-activation energy. Modeling efforts for predicting creep behavior of MPEMs are also reviewed. Methods for improving creep resistance by performing heat treatments and/or modifying microstructures are discussed. Overall, the current state of MPEMs has not yet surpassed the creep performance of commercial alloys. Finally, directions for future efforts are suggested, such as experimenting in various controlled environments, expanding the number of compositions tested, exploring advanced manufacturing techniques, and using machine-learning to predict creep properties based on compositions and microstructures.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Leach Testing of Laboratory-Scale Melter Evaporator Condensate Cementitious Waste Forms

Cementitious waste forms immobilizing evaporated AP-105 off-gas condensate were used to determine radionuclide and contaminant leachability in deionized water over a 63-day period. The off-gas condensate was collected during the actual tank AP-105 low activity waste continuous laboratory-scale melter (LSM)) run performed in fiscal year 2018 and was then solidified as a cementitious waste form using the Cast Stone formulation (8 weight percent [wt%] ordinary Portland cement, 45 wt% class F fly ash, 47 wt% blast furnace slag). Here, using the U.S. Environmental Protection Agency Method 1315 leach testing procedure, the release rate of technetium 99 (Tc), iodine-129 (I), nitrate (NO 3 - ), and sodium (Na + ) from two Cast Stone specimens was measured. From these measurements, observed diffusivity values for each constituent were calculated and can be used in future iterations and maintenance of the Integrated Disposal Facility performance assessments. Furthermore, by testing Cast Stone specimens immobilizing off-gas produced while vitrifying actual tank waste, the results of this effort improve the technical defensibility of long-term waste form performance estimates for the Cast Stone formulation. Finally, 99 Tc distribution within a representative waste form at the end of the 63-day leach period as well as bulk mineralogy were determined using solid phase characterization methods.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2023

Benchmarking quantum logic operations relative to thresholds for fault tolerance

Contemporary methods for benchmarking noisy quantum processors typically measure average error rates or process infidelities. However, thresholds for fault-tolerant quantum error correction are given in terms of worst-case error rates—defined via the diamond norm—which can differ from average error rates by orders of magnitude. One method for resolving this discrepancy is to randomize the physical implementation of quantum gates, using techniques like randomized compiling (RC). In this work, we use gate set tomography to perform precision characterization of a set of two-qubit logic gates to study RC on a superconducting quantum processor. We find that, under RC, gate errors are accurately described by a stochastic Pauli noise model without coherent errors, and that spatially correlated coherent errors and non-Markovian errors are strongly suppressed. We further show that the average and worst-case error rates are equal for randomly compiled gates, and measure a maximum worst-case error of 0.0197(3) for our gate set. Our results show that randomized benchmarks are a viable route to both verifying that a quantum processor’s error rates are below a fault-tolerance threshold, and to bounding the failure rates of near-term algorithms, if—and only if—gates are implemented via randomization methods which tailor noise.

97 MATHEMATICS AND COMPUTING↗

NASA NTRS2014

MAG4 Versus Alternative Techniques for Forecasting Active-Region Flare Productivity

MAG4 is a technique of forecasting an active region's rate of production of major flares in the coming few days from a free-magnetic-energy proxy. We present a statistical method of measuring the difference in performance between MAG4 and comparable alternative techniques that forecast an active region's major-flare productivity from alternative observed aspects of the active region. We demonstrate the method by measuring the difference in performance between the "Present MAG4" technique and each of three alternative techniques, called "McIntosh Active-Region Class," "Total Magnetic Flux," and "Next MAG4." We do this by using (1) the MAG4 database of magnetograms and major-flare histories of sunspot active regions, (2) the NOAA table of the major-flare productivity of each of 60 McIntosh active-region classes of sunspot active regions, and (3) five technique-performance metrics (Heidke Skill Score, True Skill Score, Percent Correct, Probability of Detection, and False Alarm Rate) evaluated from 2000 random two-by-two contingency tables obtained from the databases. We find that (1) Present MAG4 far outperforms both McIntosh Active-Region Class and Total Magnetic Flux, (2) Next MAG4 significantly outperforms Present MAG4, (3) the performance of Next MAG4 is insensitive to the forward and backward temporal windows used, in the range of one to a few days, and (4) forecasting from the free-energy proxy in combination with either any broad category of McIntosh active-region classes or any Mount Wilson active-region class gives no significant performance improvement over forecasting from the free-energy proxy alone (Present MAG4).

Falconer, David A.↗

NASA NTRS2014

MAG4 Versus Alternative Techniques for Forecasting Active-Region Flare Productivity

Falconer, David A.↗