Advanced gearbox technology

An advanced 13,000 HP, counterrotating (CR) gearbox was designed and successfully tested to provide a technology base for future designs of geared propfan propulsion systems for both commercial and military aircraft. The advanced technology CR gearbox was designed for high efficiency, low weight, long life, and improved maintainability. The differential planetary CR gearbox features double helical gears, double row cylindrical roller bearings integral with planet gears, tapered roller prop support bearings, and a flexible ring gear and diaphragm to provide load sharing. A new Allison propfan back-to-back gearbox test facility was constructed. Extensive rotating and stationary instrumentation was used to measure temperature, strain, vibration, deflection and efficiency under representative flight operating conditions. The tests verified smooth, efficient gearbox operation. The highly-instrumented advanced CR gearbox was successfully tested to design speed and power (13,000 HP), and to a 115 percent overspeed condition. Measured CR gearbox efficiency was 99.3 percent at the design point based on heat loss to the oil. Tests demonstrated low vibration characteristics of double helical gearing, proper gear tooth load sharing, low stress levels, and the high load capacity of the prop tapered roller bearings. Applied external prop loads did not significantly affect gearbox temperature, vibration, or stress levels. Gearbox hardware was in excellent condition after the tests with no indication of distress

Aeronautical Engineering: A special bibliography with indexes, supplement 62

This bibliography lists 306 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1975

Advances and challenges in shale oil development: A critical review

    Different from the conventional oil reservoirs, the primary storage space of shale is micro/nano pore networks. Moreover, the multiscale and multi-minerals characteristics of shale also attract increasing attentions from researchers. In this work, the advances and challenges in the development of shale oil are summarized from following aspects: phase behavior, flow mechanisms, reservoir numerical simulation and production optimization. The phase behavior of fluids confined in shale nanopores are discussed on the basis of theoretical calculations, experiments, and molecular simulations. The fluid transport mechanisms through shale matrix are analyzed in terms of molecular dynamics, pore scale simulations, and experimental studies. The methods employed in fracture propagation simulation and production optimization of shale oil are also introduced. Clarifying the problems of current research and the need for future studies are conducive to promoting the scientific and effective development of shale oil resources.Cited as: Feng, Q., Xu, S., Xing, X., Zhang, W., Wang, S. Advances and challenges in shale oil development: A critical review. Advances in Geo-Energy Research, 2020, 4(4), 406-418, doi: 10.46690/ager.2020.04.0

Finite element formulation to study thermal stresses in nanoencapsulated phase change materials for energy storage

Nanoencapsulated phase change materials (nePCMs) – which are composed of a core with a phase change material and of a shell that envelopes the core – are currently under research for heat storage applications. Mechanically, one problem encountered in the synthesis of nePCMs is the failure of the shell due to thermal stresses during heating/cooling cycles. Thus, a compromise between shell and core volumes must be found to guarantee both mechanical reliability and heat storage capacity. At present, this compromise is commonly achieved by trial and error experiments or by using simple analytical solutions. On this ground, the current work presents a thermodynamically consistent and three-dimensional finite element (FE) formulation considering both solid and liquid phases to study thermal stresses in nePCMs. Despite the fact that there are several phase change FE formulations in the literature, the main novelty of the present work is its monolithic coupling – no staggered approaches are required – between thermal and mechanical fields. Then, the FE formulation is implemented in a computational code and it is validated against one-dimensional analytical solutions. Finally, the FE model is used to perform a thermal stress analysis for different nePCM geometries and materials to predict their mechanical failure by using Rankine’s criterion

Advanced Turboprop Project

At the direction of Congress, a task force headed by NASA was organized in 1975 to identify potential fuel saving concepts for aviation. The result was the Aircraft Energy Efficiency (ACEE) Program implemented in 1976. An important part of the program was the development of advanced turboprop technology for Mach 0.65 to 0.85 applications having the potential fuel saving of 30 to 50 percent relative to existing turbofan engines. A historical perspective is presented of the development and the accomplishments that brought the turboprop to successful flight tests in 1986 and 1987

AGBT Advanced Counter-Rotating Gearbox Detailed Design Report

An Advanced Counter-Rotating (CR) Gearbox was designed and fabricated to evaluate gearbox efficiency, durability and weight characteristics for emerging propfan-powered airplanes. Component scavenge tests showed that a constant volume collector had high scavenge effectiveness, which was uneffected by added airflow. Lubrication tests showed that gearbox losses could be reduced by controlling the air/oil mixture and by directing the oil jets radially, with a slight axial component, into the sun/planet gears

Aeronautical engineering: A special bibliography with indexes, supplement 82, April 1977

This bibliography lists 311 reports, articles, and other documents introduced into the NASA scientific and technical information system in March 1977

Aeronautical Engineering: A special bibliography with indexes, supplement 67, February 1976

This bibliography lists 341 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1976

Computational uncertainity quantification in pressure-driven fracture processes

Tesi en modalitat de cotutela Universitat Politècnica de Catalunya i Eindhoven University of TechnologyUncertainty quantification is important in assessing and predicting the performance of complex engineering systems and processes, especially in the absence of adequate experimental or real-world data. With the increase in computing power, computational uncertainty quantification is playing an increasingly important role in decision making processes. We have studied the application of uncertainty quantification to pressure-driven fracture processes, which are surrounded by uncertainty as data are typically scant and available models are often rudimentary. In this dissertation we have developed a computational framework that combines simulation techniques for pressure-driven fracturing processes with state-of-the-art uncertainty quantification techniques. On the one hand, the framework simulates the influence of uncertainties in, for example, formation data, on quantities of interest such as the fracture length. On the other hand, the uncertainty quantification framework allows us to incorporate indirect measurement data, such as well pressures, in the simulation procedure. The developed computational uncertainty quantification framework improves the understanding of the influence of uncertainties on pressure-driven fracture processes.La cuantificación de la incertidumbre es importante para evaluar y predecir el desempeño de complejos sistemas y procesos de ingeniería, especialmente en ausencia de un mundo experimental o real adecuado datos. Con el aumento de la potencia informática, la cuantificación de la incertidumbre computacional está jugando un papel cada vez más importante en los procesos de toma de decisiones. Hemos estudiado la aplicación de cuantificación de la incertidumbre a los procesos de fractura por presión, que están rodeados de incertidumbre como los datos suelen ser escasos y los modelos disponibles son a menudo rudimentarios. En esta disertación hemos desarrollado un marco computacional que combina simulación. Técnicas para procesos de fractura por presión con cuantificación de incertidumbre de vanguardia técnicas Por un lado, el marco simula la influencia de las incertidumbres en, por ejemplo, datos de formación, sobre cantidades de interés como la longitud de la fractura. Por otro lado, la incertidumbre. El marco de cuantificación nos permite incorporar datos de medición indirecta, como también presiones, en el procedimiento de simulación. El marco de cuantificación de incertidumbre computacional desarrollado mejora la comprensión de la influencia de las incertidumbres en los procesos de fractura por presión.Postprint (published version