Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Feature Engineering”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60

A study of the relative effectiveness and cost of computerized information retrieval in the interactive mode

Results of a number of experiments to illuminate the relative effectiveness and costs of computerized information retrieval in the interactive mode are reported. It was found that for equal time spent in preparing the search strategy, the batch and interactive modes gave approximately equal recall and relevance. The interactive mode however encourages the searcher to devote more time to the task and therefore usually yields improved output. Engineering costs as a result are higher in this mode. Estimates of associated hardware costs also indicate that operation in this mode is more expensive. Skilled RECON users like the rapid feedback and additional features offered by this mode if they are not constrained by considerations of cost.

Smetana, F. O.↗

Effect of forward velocity on the noise characteristics of dual-flow jet nozzles

Acoustic results of jet noise tests conducted on scale-model nozzles at a wall isolation facility are presented and analyzed. The test fixture featured a triple-flow system for the purpose of simulating freestream flow around hot dual-flow jet nozzles. Test nozzles included 1/20th scale models of the exhaust system for the JT8D-9 engine, power plant for the Boeing 727 airplane (bypass ratio 1) and of the JT8D-109 refan engine (bypass ratio 2). It was found that overall jet noise is reduced by the forward velocity in proportion to the fifth and sixth power of the relative primary jet velocity. Spectral and directivity characteristics are presented.

Reed, D. H.↗

En route noise of two turboprop aircraft

In order to weigh en route noise emissions originating from future propfan powered aircraft, a data base of emission levels from conventional turboprop aircraft is needed. For this reason flyover noise measurements on two twin-engine turboprop aircraft were conducted at flight heights between 17,000 and 21,000 ft. Acoustic data are presented together with propeller operational parameters and environmental meteorological data. Narrowband spectral analyses demonstrate the characteristic features of the measured propeller noise signatures: Noise spectra are dominated by the propeller rotational noise fundamental frequency and pronounced noise beats occur as a consequence of different rotational speeds of the propellers.

Dobrzynski, Werner↗

A computer-controlled x-y offset guiding stage for the MLRS

The MLRS has experienced excellent success in its lunar and artificial satellite laser ranging operations during its many years of operation, in spite of its relatively small 'receive' aperture. We continue to strive, however, for a greater volume of data, together with better accuracy and precision. We have just now completed the design, construction, and implementation of a computer controlled x-y offset guiding stage for the MLRS, analogous to the manual one that had been a part of the original 2.7-m lunar laser ranging system on Mt. Locke at McDonald Observatory. In the past, we had been hampered by the lack of a satisfactory hardware design which could fit within the very cramped quarters of the MLRS telescope's tail piece. Recently, with funding support from the U.S. Naval Observatory and the design and construction expertise of DFM Engineering, Inc., a satisfactory instrument has been specified, designed, built, and installed. This instrument will greatly expand MLRS observational opportunities by allowing the observing crews to actively guide on visible off axis lunar surface features or background stars while the on-axis lunar surface retroreflector targets are in the dark. This paper describes this instrument and its present implementation at the MLRS.

Shelus, Peter J.↗

Subscale Injector Testing to Support Ares Engines Development

The J-2X and RS-68B rocket engines are being developed for NASA's Ares I and Ares V launch vehicles. In support of the development of these engines, hot-fire testing on subscale coaxial injectors has been performed at NASA s Marshall Space Flight Center (MSFC) to evaluate performance data relative to injector type, liquid oxygen (LOX) post tip design features, element density and various operating conditions. Shear coaxial injectors with element densities of 1.1, 1.6, and 2.3 elements/in2 and a swirl coaxial injector with element density of 1.6 elements/in2 were evaluated at conditions relevant to the Ares applications. Chamber pressures with oxygen/hydrogen propellants ranged from 815-1630 psig with mixture ratios ranging from 4.7-6.9. Fuel manifold inlet temperatures were varied from 90 to 270 R. Shear coaxial LOX post tip thicknesses ranged from 0.006 in. to 0.0175 in. Modular, water cooled, calorimeter chamber assemblies were used to provide heating rate data and evaluate the effects of characteristic length (L*). Performance was evaluated relative to the resulting characteristic velocity (C*) efficiency. Testing with both the 2.3 and 1.1 elements/in2 shear coaxial injectors demonstrated no improvement in performance of the "thin" tip configuration versus the "thick" tip configuration. The loss in chamber pressure and associated performance loss seen in previous testing at low fuel temperatures could not be reliably repeated, indicating that this loss is not the result of a fluidic process in the injector elements. Further, no performance loss could be demonstrated once a faceplate seal specifically designed for operation with low temperature hydrogen was implemented in the 1.1 elements/sq in shear coaxial injector. Results for the 1.6 elements/sq in swirl injector at cold fuel temperatures showed performance higher than both the 1.6 elements/in2 shear coaxial injector and the 2.3 elements/in2 shear coaxial injector.

Protz, Christopher↗

A General-Purpose Optimization Engine for Multi-Disciplinary Design Applications

A general purpose optimization tool for multidisciplinary applications, which in the literature is known as COMETBOARDS, is being developed at NASA Lewis Research Center. The modular organization of COMETBOARDS includes several analyzers and state-of-the-art optimization algorithms along with their cascading strategy. The code structure allows quick integration of new analyzers and optimizers. The COMETBOARDS code reads input information from a number of data files, formulates a design as a set of multidisciplinary nonlinear programming problems, and then solves the resulting problems. COMETBOARDS can be used to solve a large problem which can be defined through multiple disciplines, each of which can be further broken down into several subproblems. Alternatively, a small portion of a large problem can be optimized in an effort to improve an existing system. Some of the other unique features of COMETBOARDS include design variable formulation, constraint formulation, subproblem coupling strategy, global scaling technique, analysis approximation, use of either sequential or parallel computational modes, and so forth. The special features and unique strengths of COMETBOARDS assist convergence and reduce the amount of CPU time used to solve the difficult optimization problems of aerospace industries. COMETBOARDS has been successfully used to solve a number of problems, including structural design of space station components, design of nozzle components of an air-breathing engine, configuration design of subsonic and supersonic aircraft, mixed flow turbofan engines, wave rotor topped engines, and so forth. This paper introduces the COMETBOARDS design tool and its versatility, which is illustrated by citing examples from structures, aircraft design, and air-breathing propulsion engine design.

Patnaik, Surya N.↗

Engineering the object-relation database model in O-Raid

Raid is a distributed database system based on the relational model. O-raid is an extension of the Raid system and will support complex data objects. The design of O-Raid is evolutionary and retains all features of relational data base systems and those of a general purpose object-oriented programming language. O-Raid has several novel properties. Objects, classes, and inheritance are supported together with a predicate-base relational query language. O-Raid objects are compatible with C++ objects and may be read and manipulated by a C++ program without any 'impedance mismatch'. Relations and columns within relations may themselves be treated as objects with associated variables and methods. Relations may contain heterogeneous objects, that is, objects of more than one class in a certain column, which can individually evolve by being reclassified. Special facilities are provided to reduce the data search in a relation containing complex objects.

Dewan, Prasun↗

Predictive Evaluations of Oxygen-Rich Hydrocarbon Combustion Gas-Centered Swirl Coaxial Injectors using a Flamelet-Based 3-D CFD Simulation Approach

NASA Marshall Space Flight Center (MSFC) has embarked upon a joint project with the Air Force to improve the state-of-the-art of space application combustion device design and operational understanding. One goal of the project is to design, build and hot-fire test a 40,000 pound-thrust Oxygen/Rocket Propellant-2 (RP-2) Oxygen-Rich staged engine at MSFC. The overall project goals afford the opportunity to test multiple different injector designs and experimentally evaluate the any effect on the engine performance and combustion dynamics. To maximize the available test resources and benefits, pre-test, combusting flow, Computational Fluid Dynamics (CFD) analysis was performed on the individual injectors to guide the design. The results of the CFD analysis were used to design the injectors for specific, targeted fluid dynamic features and the analysis results also provided some predictive input for acoustic and thermal analysis of the main Thrust Chamber Assembly (TCA). MSFC has developed and demonstrated the ability to utilize a computationally efficient, flamelet-based combustion model to guide the pre-test design of single-element Gas Centered Swirl Coaxial (GCSC) injectors. Previous, Oxygen/RP-2 simulation models utilizing the Loci-STREAM flow solver, were validated using single injector test data from the EC-1 Air Force test facility. The simulation effort herein is an extension of the validated, CFD driven, single-injector design approach applied to single injectors which will be part of a larger engine array. Time-accurate, Three-Dimensional, CFD simulations were performed for five different classes of injector geometries. Simulations were performed to guide the design of the injector to achieve a variety of intended performance goals. For example, two GCSC injectors were designed to achieve stable hydrodynamic behavior of the propellant circuits while providing the largest thermal margin possible within the design envelope. While another injector was designed to purposefully create a hydrodynamic instability in the fuel supply circuit as predicted by the CFD analysis. Future multi-injector analysis and testing will indicate what if any changes occur in the predicted behavior for the single-element injector when the same injector geometry is placed in a multi-element array.

Richardson, Brian R.↗

Imaging for Hypersonic Experimental Aeroheating Testing (IHEAT) Version 4.0: User Manual

The IHEAT v4.0 software is a data reduction code for global thermography data acquired in the NASA Langley Aerothermodynamics Laboratory (LAL) hypersonic wind tunnels. IHEAT uses red and green color-intensity data from two-dimensional images of wind tunnel models to compute temperatures and heat-transfer rates using a semi-infinite, one-dimensional heat transfer approximation at each image pixel. Multiple automated tools in IHEAT v4.0 decrease the time required to reduce the data from a phosphor thermography wind tunnel run. Data at one or all of the image pixel locations can be exported to computer files for further analysis. The prior version of IHEAT, v3.2, was written in PV-WAVE® (now owned by Rogue Wave® Software) in 1994 and was limited in functionality to fit within the memory constraints of the available computers at the time. IHEAT v4.0 is written in MATLAB® by MathWorks® and contains several new features that leverage the increase in available memory of the current computers. A Piecewise tool permits the user to extract data along a segmented line cut that can follow interesting features in the image better than the single, straight line cuts that were possible with the legacy Length and Profile tools. The new Load Run and Batch tools facilitate batch processing by loading in all of the input files and images for a run at the same time. Load Run permits the user to process the available run images manually, while Batch automatically saves heat transfer data from all of the images based on the analysis previously performed on a single frame. IHEAT v4.0 also can automatically calculate the temporal collapse of reference line cuts from the time history heating data for a run to indicate the appropriate frame to reduce for each run. The IHEAT v4.0 source code was compiled into a standalone executable file that can be accessed remotely from several computers with different operating systems, simultaneously. The software is run through the MATLAB® Compiler Runtime engine, and therefore, IHEAT does not require a software license to run. Any software commands executed in the IHEAT v4.0 code will not affect other similar applications running on the same machine. Similarly, changes to the parent software do not affect a compiled code. These features of IHEAT v4.0 are improvements over the legacy v3.2 code, which required regular maintenance to avoid losing functionality as the PVWAVE ® programming language was upgraded.

Mason, Michelle L.↗

Thermal barrier coating life modeling in aircraft gas turbine engines

Analytical models useful for predicting ceramic thermal barrier coating (TBC) spalling life in aircraft gas turbine engines are presented. Electron beam-physical vapor deposited (EB-PVD) and plasma sprayed TBC systems are discussed. TBC spalling was attributed to a combination of mechanisms such as metal oxidation at the ceramic-metal interface, ceramic-metal interface stress concentrations at free surfaces due to dissimilar materials, ceramic-metal interface stresses caused by local radius of curvature and interface roughness, material properties and mechanical behavior, transient temperature gradients across the ceramic layer and component design features. TBC spalling life analytical models were developed based on observations of TBC failure modes and plausible failure theories. TBC failure was assumed to occur when the imposed stresses exceeded the material strength (at or near the ceramic-metal interface). TBC failure knowledge gaps caused by lack of experimental evidence and analytical understanding are noted. The analytical models are considered initial engineering approaches that capture observed TBC failure trends.

Nissley, D. M.↗

Design and Operability of a Variably Premixed Rotating Detonation Engine for the Evaluation of Mixing Effects

The design of a variably premixed rotating detonation engine (RDE) is presented with preliminary experimental results. Premixed operation decouples the mixing process from the detonation cycle, enabling direct comparison with premixed simulations. A porous medium, formed into a ring of 6.45 mm radial thickness, serves as the premixture injector, arresting potential flash-back events. Two chamber geometries are tested, the first aimed at eliminating recirculation zones and comprised of a 7.62 mm wide channel, the width of which the porous injector occupies 85%. The second chamber geometry features a 10.7 mm channel width and a 3.08 mm wide backward-facing step on the internal diameter of the premixture injector. Transverse optical access is incorporated into the design using a transparent outer body. Tests were conducted at mixing conditions ranging from non-premixed to fully premixed with gaseous hydrogen and air reactants in the narrow-channel configuration. Engine operating modes and detonation wave speeds were characterized using aft-end high-speed chemiluminescence imaging, while detonation wave topology and heat release in the refill zone are captured by transverse imaging. A two-wave counterpropagating mode was most commonly observed in the narrow-channel configuration with wave speeds ranging from 49-67% of the theoretical Chapman-Jouguet (CJ) velocity. Fully premixed operation in the backward-facing step configuration rendered wave speeds up to 86% of CJ velocity, consistent with previous non-premixed results using the same channel width and a backward-facing step. These results demonstrate successful premixed RDE operation with high wave speeds and highlight the role of product recirculation zones in stabilizing the detonation cycle.

detonation↗

Preliminary study of supersonic-transport configurations with low values of sonic boom

A parametric study of low-boom supersonic transport airplanes with conventional configurations was made to identify the features of specific configurations that promise relatively low sonic boom overpressures (less than 47.9 N/sq m). The range of values considered was gross weight from 28,300 to 170,000 kg; cruise Mach numbers of 2 to 3.2; and wing loadings of 1436, 2870, and 4309 N/sq m. Fuselage length was varied from 49.1 to 102.4 m and fuselage diameter from 2.75 to 3.98 m. A nominal Mach 2 configuration weighing 56,700 kg and having a wing loading of 2870 N/sq m was selected; and its gross geometric, aerodynamic, and structural features were estimated. At a cruise altitude of 18,300 m, lift-drag ratio was estimated to be 7.35, while sonic boom overpressure was 41.7 N/sq m. Takeoff thrust loading using four afterburning turbojet engines at maximum dry thrust was 0.32. Payload for a 4440-km range was 16.7 percent of gross weight, giving a direct operating cost of 0.82 cent per seat statute mile.

Dugan, J. F., Jr.↗

Liquid rocket valve components

A monograph on valves for use with liquid rocket propellant engines is presented. The configurations of the various types of valves are described and illustrated. Design criteria and recommended practices for the various valves are explained. Tables of data are included to show the chief features of valve components in use on operational vehicles.

Source record↗

The NASA high pressure facility and turbine test rig

NASA Lewis Research Center is presently constructing a test facility for developing turbine-cooling and combustor technology for future-generation aircraft gas-turbine engines. Prototype engine hardware will be investigated in this facility at gas-stream conditions up to 2480 K average turbine inlet temperature and 4.14 million N/sq m turbine inlet pressure. The facility will have the unique features of fully automated control and data acquisition through the use of an integrated system of minicomputers and programmable controllers, which will result in more effective use of operating time and operators and will provide a built-in self-protection safety system. The facility, turbine rig, and turbine-cooling test program are described.

Stepka, F. S.↗

Evaluation of pressure and thermal data from a wind tunnel test of a large-scale, powered, STOL fighter model

A STOL fighter model employing the vectored-engine-over wing concept was tested at low speeds in the NASA/Ames 40 by 80-foot wind tunnel. The model, approximately 0.75 scale of an operational fighter, was powered by two General Electric J-97 turbojet engines. Limited pressure and thermal instrumentation were provided to measure power effects (chordwise and spanwise blowing) and control-surface-deflection effects. An indepth study of the pressure and temperature data revealed many flow field features - the foremost being wing and canard leading-edge vortices. These vortices delineated regions of attached and separated flow, and their movements were often keys to an understanding of flow field changes caused by power and control-surface variations. Chordwise blowing increased wing lift and caused a modest aft shift in the center of pressure. The induced effects of chordwise blowing extended forward to the canard and significantly increased the canard lift when the surface was stalled. Spanwise blowing effectively enhanced the wing leading-edge vortex, thereby increasing lift and causing a forward shift in the center of pressure.

Howell, G. A.↗

The composing process in technical communication

The theory and application of the composing process in technical communications is addressed. The composing process of engineers, some implications for composing research for the teaching and research of technical communication, and an interpretation of the processes as creative experience are also discussed. Two areas of technical communications summarized concern: the rhetorical features of technical communications, and the theoretical background for a process-based view, a problem-solving approach to technical writing.

Masse, R. E.↗

Prediction of vortical flows on wings using incompressible Navier-Stokes equations

Numerical solutions to the incompressible Navier-Stokes equations are in greater demand than ever before as the field of computational fluid dynamics (CFD) increases its impact as an engineering tool. An implicit upwind-relation finite-difference scheme is developed for solving unsteady incompressible Navier-Stokes equations incorporating an artificial time derivative of the pressure to the continuity equation. The essential features observed in experiments for complicated vortical flows past three round-edged low-aspect-ratio wings at high angles of attack are reproduced both qualitatively and quantitatively.

Hsu, C.-H.↗

IDEF5 Ontology Description Capture Method: Concept Paper

The results of research towards an ontology capture method referred to as IDEF5 are presented. Viewed simply as the study of what exists in a domain, ontology is an activity that can be understood to be at work across the full range of human inquiry prompted by the persistent effort to understand the world in which it has found itself - and which it has helped to shape. In the contest of information management, ontology is the task of extracting the structure of a given engineering, manufacturing, business, or logistical domain and storing it in an usable representational medium. A key to effective integration is a system ontology that can be accessed and modified across domains and which captures common features of the overall system relevant to the goals of the disparate domains. If the focus is on information integration, then the strongest motivation for ontology comes from the need to support data sharing and function interoperability. In the correct architecture, an enterprise ontology base would allow th e construction of an integrated environment in which legacy systems appear to be open architecture integrated resources. If the focus is on system/software development, then support for the rapid acquisition of reliable systems is perhaps the strongest motivation for ontology. Finally, ontological analysis was demonstrated to be an effective first step in the construction of robust knowledge based systems.

Menzel, Christopher P.↗