Theory and Design of Flight-Vehicle Engines

Papers are presented on such topics as the testing of aircraft engines, errors in the experimental determination of the parameters of scramjet engines, the effect of the nonuniformity of supersonic flow with shocks on friction and heat transfer in the channel of a hypersonic ramjet engine, and the selection of the basic parameters of cooled GTE turbines. Consideration is also given to the choice of optimal total wedge angle for the acceleration of aerospace vehicles, the theory of an electromagnetic-resonator engine, the dynamic characteristics of the pumps and turbines of liquid propellant rocket engines in transition regimes, and a hierarchy of mathematical models for spacecraft control engines

Langley aerospace test highlights, 1985

The role of the Langley Research Center is to perform basic and applied research necessary for the advancement of aeronautics and space flight, to generate new and advanced concepts for the accomplishment of related national goals, and to provide research advice, technological support, and assistance to other NASA installations, other government agencies, and industry. Significant tests which were performed during calendar year 1985 in Langley test facilities, are highlighted. Both the broad range of the research and technology activities at the Langley Research Center and the contributions of this work toward maintaining United States leadership in aeronautics and space research, are illustrated. Other highlights of Langley research and technology for 1985 are described in Research and Technology-1985 Annual Report of the Langley Research Center

Contribution à la compréhension de la dynamique des rotors des alternateurs hydroélectriques

Dans les centrales hydrauliques, les groupes turbines-alternateurs sont soumis à plusieurs forces et couples dynamiques qui, sous certaines conditions, peuvent engendrer des bruits, des vibrations et des problèmes d’interactions avec le réseau, voire même des bris d’équipement. L’objectif de cette thèse est de développer un modèle d’alternateur hydroélectrique afin d’étudier les effets de la non-uniformité de l’entrefer et du défaut de court-circuit entre spires au rotor sur le comportement dynamique des groupes turbines-alternateurs. Les alternateurs hydroélectriques présentent toujours des entrefers non-uniformes. Ainsi, l’étude cherche à développer un modèle en utilisant la méthode des éléments finis et une mesure précise de l’entrefer sur un alternateur en en opération afin d’étudier les forces électromagnétiques qui pourraient exciter sa structure. Puisque l’entrefer est affecté par la dilatation thermique, les formes du stator et du rotor et le mouvement du rotor, cette modélisation numérique est nécessaire pour l’obtention d’un modèle réaliste du comportement du générateur. D’autre part, parmi les défauts les plus communs qui peuvent apparaître au rotor d’un alternateur hydroélectrique figure le défaut de court-circuit entre spires. Les courts-circuits d’enroulements de pôles amènent une augmentation significative des vibrations. Ces deux défauts jouent un rôle important dans le calcul des forces électromagnétiques. Le modèle permet d’étudier et d’évaluer plus précisément l’impact de ces défauts sur les forces électromagnétiques transmises à l’arbre. La présente thèse s’intéresse aussi aux modes et aux fréquences susceptibles d’entraîner des vibrations de la structure du stator à cause des excitations électromagnétiques résultantes des défauts mentionnés. Les transformées de Fourier rapides de la densité de force électromagnétique et de la force résultante totale révèlent l’existence des composants sous-harmoniques absents dans d’autres types de machines électriques. Ces sous-harmoniques causent des vibrations importantes sur l’arbre du groupe turbine-alternateur, ainsi que sur le stator et le rotor de l’alternateur. Les résultats expérimentaux confirment les résultats numériques et analytiques dans l’identification des spectres des forces. Dans le présent travail, l’analyse numérique apporte une contribution à l’étude du comportement dynamique des lignes d’arbres de groupes de production hydroélectriques, qui consiste en l’identification des harmoniques des défauts mentionnés, dans le cadre du projet SAMH (Simulations numériques appliquées aux machines hydrauliques) de l’Institut de recherche d’Hydro-Québec

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Aeronautical engineering: A continuing bibliography with indexes (supplement 119)

This bibliography lists 341 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1980. Abstracts on the engineering and theoretical aspects of design, construction, evaluation, testing, operation, and performance of aircraft (including aircraft engines) and associated components, equipment, and systems are presented. Research and development in aerodynamics, aeronautics, and ground support equipment for aeronautical vehicles are also presented

Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Change

Understanding the process interactions and feedbacks among water, porous geological media, microbes, and vascular plants is crucial for improving predictions of the response of Earth’s critical zone to future climatic conditions. However, the integrated coevolution of landscapes under change is notoriously difficult to investigate. Laboratory studies are limited in spatial and temporal scale, while field studies lack observational density and control. To bridge the gap between controlled laboratory and uncontrollable field studies, the University of Arizona built a macrocosm experiment of unprecedented scale: the Landscape Evolution Observatory (LEO). LEO comprises three replicated, heavily instrumented, hillslope-scale model landscapes within the environmentally controlled Biosphere 2 facility. The model landscapes were designed to initially be simple and purely abiotic, enabling scientists to observe each step in the landscapes’ evolution as they undergo physical, chemical, and biological changes over many years. This chapter describes the model systems and associated research facilities and illustrates how LEO allows for tracking of multiscale matter and energy fluxes at a level of detail impossible in field experiments. Initial sensor, sampler, and soil coring data are already providing insights into the tight linkages between water flow, weathering, and microbial community development. These interacting processes are anticipated to drive the model systems to increasingly complex states and will be impacted by the introduction of vascular plants and changes in climatic regimes over the years to come. By intensively monitoring the evolutionary trajectory, integrating data with mathematical models, and fostering community-wide collaborations, we envision that emergent landscape structures and functions can be linked, and significant progress can be made toward predicting the coupled hydro-biogeochemical and ecological responses to global change

Energy, a continuing bibliography with indexes. Issue 33

This bibliography lists 1211 reports, articles, and other documents introduced into the NASA scientific and technical information system from January 1, 1981 through March 31, 1981