Aeronautical Engineering: A special bibliography with indexes, supplement 54

This bibliography lists 316 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1975

Development of a subsonic free-jet nozzle for inlet-engine integration ground test facilities

The Arnold Engineering Development Center (AEDC) offers a unique test capability for the evaluation of inlet-engine compatibility. The capability features a variable-attitude and variable-Mach number free-jet nozzle that subjects an aircraft propulsion system to a flow field approximating the flight environment. The free-jet nozzle provides a flow quality commensurate with inlet-engine compatibility test requirements over a wide range of pitch angles, yaw angles, and Mach numbers. The development of the nozzle centered on achievement of the required flow quality. Initial flow quality experiments revealed a tendency for large, secondary vortical flows to develop in the free-jet nozzle flow field. These vortical flows severely degraded the flow quality delivered by the nozzle. The failure of the initial nozzle to achieve flow quality goals motivated research focused on preventing the formation of vortices in subsonic free-jet nozzles. This thesis describes a comprehensive investigation that coupled water flow and airflow experiments to improve the understanding of the mechanisms leading to the formation of nozzle vortices, and to develop vortex suppression methods. Providing a unique flow visualization capability, the water tunnel revealed features of the complex flow field associated with the vortex formation and facilitated the identification of vortex suppression techniques. The airflow tests provided detailed flow-field measurements for validating water tunnel findings and verifying achievement of flow requirements. The water flow and airflow experiments provided information that enabled the development of specifications for a subsonic free-jet nozzle to be applied in the AEDC Aeropropulsion Systems Test Facility (ASTF) free-jet test system. The experiments used two sub-scale models of the ASTF Test Cell C-2. The airflow model quantified nozzle exit flow quality through measurements of Mach number and flow angle distributions. The measurements were obtained at nominal Mach numbers ranging from 0.3 to 0.9 and nozzle pitch angles ranging from 0 to 50 deg. The water flow model, installed in the University of Tennessee Space Institute water tunnel, used dye injection to delineate streaklines of the flow entering and exiting free-jet nozzle configurations. The development of the free-jet nozzle employed multiple entries in both the air flow and water flow facilities. The work progressed through the process of identifying flow anomalies, determining the critical parameters that dominate the secondary flow formation, identifying candidate flow quality improvement methods, selecting a method for application in the ASTF free-jet nozzle, and validating nozzle configurations prior to full-scale implementation. This thesis provides both visual and measured free-jet nozzle flow characteristics. obtained during the investigation. Comparisons of airflow and water flow simulations illustrate the validation of the water tunnel as a tool for studying secondary internal flows. Parametric results reveal the nozzle and installation features that influence the secondary flow formation. Finally, results show the numerous methods investigated for preventing the formation of vortices. The research yielded two successful vortex suppression methods. Each method modified the flow field in the vicinity of the vortex attachment point, near the nozzle inlet, to prevent vortex formation. The thesis describes the selection and application of one method in a nozzle configuration that meets the requirements for the ASTF free-jet test system

Supersonic combustor modeling

The physical phenomena involved when a supersonic flow undergoes chemical reaction are discussed. Detailed physical models of convective and diffusive mixing, and finite rate chemical reaction in supersonic flow are presented. Numerical algorithms used to solve the equations governing these processes are introduced. Computer programs using these algorithms are used to analyze the structure of the reacting mixing layer. It is concluded that, as in subsonic flow, exothermic heat release in unconfined supersonic flows retards fuel/air mixing. Non mixing is shown to be a potential problem in reducing the efficiency of supersonic as well as subsonic combustion. Techniques for enhancing fuel/air mixing and combustion are described

Aeronautical Engineering: A special bibliography, supplement 60

This bibliography lists 284 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1975

Aeronautical Engineering: A special bibliography with indexes, supplement 51

This bibliography lists 206 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in November 1974

Overview of the Applied Aerodynamics Division

A major reorganization of the Aeronautics Directorate of the Langley Research Center occurred in early 1989. As a result of this reorganization, the scope of research in the Applied Aeronautics Division is now quite different than that in the past. An overview of the current organization, mission, and facilities of this division is presented. A summary of current research programs and sample highlights of recent research are also presented. This is intended to provide a general view of the scope and capabilities of the division

Stratospheric aircraft exhaust plume and wake chemistry studies

This report documents progress to date in an ongoing study to analyze and model emissions leaving a proposed High Speed Civil Transport (HSCT) from when the exhaust gases leave the engine until they are deposited at atmospheric scales in the stratosphere. Estimates are given for the emissions, summarizing relevant earlier work (CIAP) and reviewing current propulsion research efforts. The chemical evolution and the mixing and vortical motion of the exhaust are analyzed to track the exhaust and its speciation as the emissions are mixed to atmospheric scales. The species tracked include those that could be heterogeneously reactive on the surfaces of the condensed solid water (ice) particles and on exhaust soot particle surfaces. Dispersion and reaction of chemical constituents in the far wake are studied with a Lagrangian air parcel model, in conjunction with a radiation code to calculate the net heating/cooling. Laboratory measurements of heterogeneous chemistry of aqueous sulfuric acid and nitric acid hydrates are also described. Results include the solubility of HCl in sulfuric acid which is a key parameter for modeling stratospheric processing. We also report initial results for condensation of nitric acid trihydrate from gas phase H2O and HNO3

Aeronautical engineering: A continuing bibliography, supplement 122

This bibliography lists 303 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1980

Numerička simulacija procesa spreja i izgaranja u komori za izgaranje mlaznog motora

U ovom radu, izvršeno je numeričko modeliranje procesa spreja i izgaranja unutar komore za izgaranje mlaznog motora. Promatrana komora sastoji se od dvostupanjskog radijalnog vrtložnika koji se koristi za induciranje vrtloga zraka. Na ulazu u komoru propisan je konstantan protok zraka kako bi se osiguralo dovoljno kisika u zoni izgaranja. U ovom radu tekuće gorivo Jet-A korišteno je kao zamjena za kerozin. Za modeliranje turbulentnog strujanja korišten je napredni k-ζ-f model turbulencije, dok je za opisivanje procesa spreja korišten Euler Lagrangeov pristup modeliranja spreja. Proces izgaranja modeliran je pomoću ECFM-3Z modela izgaranja dok je proces zapaljenja modeliran korištenjem ISSIM modela zapaljenja. Utjecaj spreja analiziran je provođenjem simulacija s različitim kutom spreja. Verificirani su prezentirani rezultati, kao što su temperaturna raspodjela, profili brzine te koncentracija emisija kroz komoru za izgaranje. S obzirom na dobivene rezultate, može se zaključiti da je postignuto ispravno fizikalno i kemijsko ponašanje unutar komore izgaranja. Sve simulacije su odrađene u komercijalnom RDF programu AVL FIRE™