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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Impact of Sr-Containing Secondary Phases on Oxide Conductivity in Solid-Oxide Electrolyzer Cells

Solid-oxide electrolyzer cells (SOECs) based on a yttria-stabilized zirconia (YSZ) oxide electrolyte produce hydrogen from water with the assistance of excess thermal energy; however, Sr diffusion within the Gd-doped CeO 2 (GDC) barrier layer during processing or operation can lead to the formation of unwanted secondary phases such as SrO and SrZrO 3 . Here, to establish and compare the degree of impact of these phases on SOEC performance, we conduct first-principles calculations to study their bulk oxide conductivities and compare them to that of the YSZ electrolyte. We find that SrO has a low conductivity arising from the poor mobility and low concentration of mobile oxygen vacancies, and its presence in SOECs should therefore be avoided. SrZrO 3 also has a lower oxide conductivity than YSZ; however, this discrepancy is primarily due to lower vacancy concentrations rather than low mobility. We find that sufficient levels of Y-doping on the Zr site can increase oxygen vacancy concentrations in SrZrO 3 to achieve an oxide ionic conductivity on par with that of YSZ, thereby mitigating any potential deleterious effect on transport performance. Energy-dispersive X-ray spectroscopy confirms that Y is the most common minority element present in SrZrO 3 forming near the GDC–YSZ interface, alleviating concerns regarding the impact of SrZrO 3 on device performance. These results from our combined computational–experimental analysis can inform future engineering strategies designed to limit the detrimental effects of Sr-induced secondary phase formation on SOEC performance.

08 HYDROGEN↗
DOE OSTI2020

An a priori evaluation of a principal component and artificial neural network based combustion model in diesel engine conditions

A principal component analysis (PCA) and artificial neural network (ANN) based chemistry tabulation approach is presented. ANNs are used to map the thermochemical state onto a low-dimensional manifold consisting of five control variables that have been identified using PCA. Three canonical configurations are considered to train the PCA-ANN model: a series of homogeneous reactors, a nonpremixed flamelet, and a two-dimensional lifted flame. The performance of the model in predicting the thermochemical manifold of a spatially-developing turbulent jet flame in diesel engine thermochemical conditions is a priori evaluated using direct numerical simulation (DNS) data. The PCA-ANN approach is compared with a conventional tabulation approach (tabulation using ad hoc defined control variables and linear interpolation). The PCA-ANN model provides higher accuracy and requires several orders of magnitude less memory. Here, these observations indicate that the PCA-ANN model is superior for chemistry tabulation, especially for modelling complex chemistries that present multiple combustion modes as observed in diesel combustion. The performance of the PCA-ANN model is then compared to the optimal estimator, i.e. the conditional mean from the DNS. The results indicate that the PCA-ANN model gives high prediction accuracy, comparable to the optimal estimator, especially for major species and the thermophysical properties. Higher errors are observed for the minor species and reaction rate predictions when compared to the optimal estimator. It is shown that the prediction of minor species and reaction rates can be improved by using training data that exhibits a variation of parameters as observed in the turbulent flame. The output of the ANN is analysed to assess mass conservation. It is observed that the ANN incurs a mean absolute error of 0.05% in mass conservation. Furthermore, it is demonstrated that this error can be reduced by modifying the cost function of the ANN to penalise for deviation from mass conservation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Cyber-Informed Engineering Requirements Framework Use Cases

The requirement analysis use case effort leverages the Cyber-Informed Engineering (CIE) requirements framework to examine two real-world scenarios: Battery Energy Storage System (BESS) installation at the Flatirons Campus, NLR; SCADA improvement program. This work evaluates the existing requirements for each use case, applies the CIE requirements framework, and assesses the benefits and enhancements gained compared to the current requirements. The results will advance CIE from concept to practical application by identifying key opportunities for integrating CIE principles into established engineering workflows during the requirements phase.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1971

Inertial navigation systems analysis.

This volume offers the avionic systems engineer a fundamental exposition of the mechanization and error analysis of inertial navigation systems. While the material is applicable to spacecraft and undersea navigation, emphasis is placed upon terrestrial applications on or slightly above the earth's surface. As a result, practical considerations are geared toward those aircraft navigation systems of particular current interest. Extensive use is made of perturbation techniques to develop linearized system equations, whose solutions closely approximate those obtained by nonlinear differential equations. A unified error analysis technique is developed that is applicable to virtually all system configurations. The technique provides a greatly simplified method for comparing the performance of competing system configurations.

Britting, K. R.↗
NASA NTRS1989

Development of a combustor analytical design methodology for liquid rocket engines

The development of a user friendly computerized methodology for the design and analysis of liquid propellant rocket engine combustion chambers is described. An overview of the methodology, consisting of a computer program containing an appropriate modular assembly of existing industry wide performance and combustion stability models, is presented. These models are linked with an interactive front end processor enabling the user to define the performance and stability traits of an existing design (point analysis) or to create the essential design features of a combustor to meet specific performance goals and combustion stability (point design). Plans for demonstration and verification of this methodology are also presented. These plans include the creation of combustor designs using the methodology, together with predictions of the performance and combustion stability for each design. A verification test program of 26 hot fire tests with up to four designs created using this methodology is described. This testing is planned using LOX/RP-1 propellants with a thrust level of approx. 220,000 N (50,000 lbf).

Pieper, Jerry L.↗
DOE OSTI2023

Mean Time to Failure Analysis for the Los Alamos National Laboratory Weapons Engineering Tritium Facility Tritium Containment Vessels

The Weapons Engineering Tritium Facility (WETF) is a Hazard Category 2 nonreactor nuclear facility located in Technical Area 16 (TA-16) of Los Alamos National Laboratory. Tritium related research, development, and processing in support of stockpile stewardship program activities is conducted at WETF. Within WETF, various devices can be used to contain tritium and certain devices are designated as Tritium Containment Vessels (TCVs). Several different device types are identified as TCVs within WETF such as LP-50s and AL-M1s. Historically, a threshold tritium mass value has been used as the mechanism for designating a device as a TCV. When the tritium content of the device was below the tritium mass threshold it was not considered to be a TCV in the formal context. When the tritium content was above the administrative threshold, the device was considered to be a TCV. An upper tritium mass limit was also established for TCVs.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1961

ANALYSIS OF CRYOGENIC PROPELLANT FEED SYSTEMS FOR ELECTROTHERMAL ENGINES.

An analytical investigation was made of the problems associated with the long-term storage and control of flow of cryogenic propellants for electrothermal engines. Storage of 35 to 174 pounds of propellant for three years is made difficult by the high ratio of surface area to storage tank volume, and the resulting high rate of heat leak. Vented and non-vented storage, storage as high pressure gas, and the use of refrigeration were considered. Recommended storage methods are: for ethane and ammonia vented storage - by venting propellant stored in excess of mission requirements; for hydrogen and helium - by non-vented storage of cold supercritical vapor; and for methane by storage as a non-vented two-phase mixture. The optimum propellant density in the storage tank and optimum insulation thickness were also determined. Design charts were developed for hydrogen and helium, for estimating the maximum pressure expected in non-vented storage tanks, as function of mission requirements. Separation of the constituent phases of liquid-vapor mixtures is achieved by throttling the two-phase mixture to a lower pressure (and temperature) and vaporizing the liquid in the mixture by heat exchange with the contents of the storage tank. The time limitations for continuous use of this method are discussed. Linde super insulations SI-44 or SI -91 are recommended for insulation. Precooling the insulation to temperatures below the steady state level with cold helium vapor before or during fueling of the storage tank eliminates the flow of heat to the tank contents during countdown and take-off. The masses, sizes, and power requirements of the recommended systems are low. The controls are simple and reliable. From the equations and charts in this report the components of the system for a particular mission can be sized. Recommendations are given for experimental work required for the development and testing of such components.

ELECTROTHERMAL ENGINE↗
NASA NTRS1973

Numerical analysis of stiffened shells of revolution. Volume 4: Engineer's program manual for STARS-2S shell theory automated for rotational structures - 2 (statics) digital computer program

The engineering programming information for the digital computer program for analyzing shell structures is presented. The program is designed to permit small changes such as altering the geometry or a table size to fit the specific requirements. Each major subroutine is discussed and the following subjects are included: (1) subroutine description, (2) pertinent engineering symbols and the FORTRAN coded counterparts, (3) subroutine flow chart, and (4) subroutine FORTRAN listing.

Svalbonas, V.↗
NASA NTRS1975

Numerical nonlinear inelastic analysis of stiffened shells of revolution. Volume 3: Engineer's program manual for STARS-2P digital computer program

Engineering programming information is presented for the STARS-2P (shell theory automated for rotational structures-2P (plasticity)) digital computer program, and FORTRAN 4 was used in writing the various subroutines. The execution of this program requires the use of thirteen temporary storage units. The program was initially written and debugged on the IBM 370-165 computer and converted to the UNIVAC 1108 computer, where it utilizes approximately 60,000 words of core. Only basic FORTRAN library routines are required by the program: sine, cosine, absolute value, and square root.

Svalbonas, V.↗
NASA NTRS1980

Thermodynamic analysis of turbulent combustion in a spark ignition engine. Experimental evidence

A method independent of physical modeling assumptions is presented to analyze high speed flame photography and cylinder pressure measurements from a transparent piston spark ignition research engine. The method involves defining characteristic quantities of the phenomena of flame propagation and combustion, and estimating their values from the experimental information. Using only the pressure information, the mass fraction curves are examined. An empirical burning law is presented which simulates such curves. Statistical data for the characteristics delay and burning angles which show that cycle to cycle fractional variations are of the same order of magnitude for both angles are discussed. The enflamed and burnt mass fractions are compared as are the rates of entrainment and burning.

Beretta, G. P.↗
NASA NTRS1981

Design and analysis of a fuel-efficient single-engine, turboprop-powered, business airplane

The speed, range, payload, and fuel efficiency of a general aviation airplane powered by one turboprop engine was determined and compared to a twin engine turboprop aircraft. An airplane configuration was developed which can carry six people for a noreserve range of 2,408 km at a cruise speed above 154 m/s, and a cruise altitude of about 9,144 m. The cruise speed is comparable to that of the fastest of the current twin turboprop powered airplanes. It is found that the airplane has a cruise specific range greater than all twin turboprop engine airplanes flying in its speed range and most twin piston engine airplanes flying at considerably slower cruise airspeeds.

Martin, G. L.↗