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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Investigation of Unsteady Flow Interaction Between an Ultra-Compact Inlet and a Transonic Fan

In the study presented, unsteady flow interaction between an ultra-compact inlet and a transonic fan stage is investigated. Future combat aircraft engines require ultra-compact inlet ducts as part of an integrated, advanced propulsion system to improve air vehicle capability and effectiveness to meet future mission needs. The main purpose of the current study is to advance the understanding of the flow interaction between a modern ultra-compact inlet and a transonic fan for future design applications. Many experimental/ analytical studies have been reported on the aerodynamics of compact inlets in aircraft engines. On the other hand, very few studies have been reported on the effects of flow distortion from these inlets on the performance of the following fan/compressor stages. The primary goal of the study presented is to investigate how flow interaction between an ultra-compact inlet and a transonic compressor influence the operating margin of the compressor. Both Unsteady Reynolds-averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) approaches are used to calculate the unsteady flow field, and the numerical results are used to study the flow interaction. The present study indicates that stall inception of the following compressor stage is affected directly based on how the distortion pattern evolves before it interacts with the fan/compressor face. For the present compressor, the stall initiates at the tip section with clean inlet flow and distortion pattern away from the casing itself seems to have limited impacts on the stall inception of the compressor. A counter-rotating swirl, which is generated due to flow separation inside the s-shaped compact duct, generates an increased flow angle near the blade tip. This increased flow angle near the rotor tip due to the secondary flow from the counter-rotating vortices is the primary reason for the reduced compressor stall margin.

Compressor↗
NASA NTRS2015

Application of an Aligned and Unaligned Signal Processing Technique to Investigate Tones and Broadband Noise in Fan and Contra-Rotating Open Rotor Acoustic Spectra

The study of noise from a two-shaft contra-rotating open rotor (CROR) is challenging since the shafts are not phase locked in most cases. Consequently, phase averaging of the acoustic data keyed to a single shaft rotation speed is not meaningful. An unaligned spectrum procedure that was developed to estimate a signal coherence threshold and reveal concealed spectral lines in turbofan engine combustion noise is applied to fan and CROR acoustic data in this paper (also available as NASA/TM-2015-218865). The NASA Advanced Air Vehicles Program, Advanced Air Transport Technology Project, Aircraft Noise Reduction Subproject supported the current work. The fan and open rotor data were obtained under previous efforts supported by the NASA Quiet Aircraft Technology (QAT) Project and the NASA Environmentally Responsible Aviation (ERA) Project of the Integrated Systems Research Program in collaboration with GE Aviation, respectively. The overarching goal of the Advanced Air Transport (AATT) Project is to explore and develop technologies and concepts to revolutionize the energy efficiency and environmental compatibility of fixed wing transport aircrafts. These technological solutions are critical in reducing the impact of aviation on the environment even as this industry and the corresponding global transportation system continue to grow.

Aeroacoustics↗
NASA NTRS2018

Acoustic Testing of a High-Tip-Speed Fan with Bypass-Duct Liners

Under a pair of Space Act Agreements between NASA and Honeywell Aerospace, a model-scale (22 in.-diameter fan) acoustic wind tunnel test was carried out in the fall of 2014 in the NASA Glenn Research Center 9- by 15-Foot Low-Speed Wind Tunnel. The goal was to obtain acoustic pressure measurements for far-field, inlet and exit rotating rake, and in-duct microphone locations. This supersonic-tip-speed fan was tested in three bypass duct configurations: hard-wall, traditional liner, and advanced multiple-degree-of-freedom. Limited aerodynamic data was collected to verify the expected operating conditions. Preliminary analysis of the acoustic data finds it suitable for use in evaluating current NASA and Honeywell Aerospace acoustic tools and liner design practices.

Noise↗
NASA NTRS2019

Acoustic Testing of a High-Tip-Speed Fan with Bypass-Duct Liners - Overview

Under a pair of Space Act Agreements between NASA and Honeywell Aerospace, a model-scale (22 in.-diameter fan) acoustic wind tunnel test was carried out in the fall of 2014 in the NASA Glenn Research Center 9- by 15-Foot Low-Speed Wind Tunnel. The goal was to obtain acoustic pressure measurements for far-field, inlet and exit rotating rake, and in-duct microphone locations. This supersonic-tip-speed fan was tested in three bypass duct configurations: hard-wall, traditional liner, and advanced multiple-degree-of-freedom. Limited aerodynamic data was collected to verify the expected operating conditions. Preliminary analysis of the acoustic data finds it suitable for use in evaluating current NASA and Honeywell Aerospace acoustic tools and liner design practices. This report provides an overview of the test and some preliminary findings.

Miller, Christopher J.↗
NASA NTRS2019

An Investigation of Bifurcation Acoustic Treatment Effects on Aft-Fan Engine Nacelle Noise

Increasing air traffic and more stringent aircraft noise regulations continue to expand requirements on aircraft noise reduction capabilities for conventional and unconventional aircraft configurations. A major component of the overall aircraft noise is the sound associated with the propulsion system mounted in the engine nacelle. Acoustic liners mounted in the aircraft engine nacelles provide a significant portion of the current fan noise reduction. However, they must be further optimized if challenging noise reduction goals are to be achieved. One area within the aft bypass duct that may be an excellent candidate for increased attention is the acoustic treatment on the engine bifurcations (i.e., engine pylon and lower bifurcation). This paper describes a fundamental study of the effects of bifurcation treatment on simulated aft fan noise, as well as the validation of numerical tools to predict such effects. Five bifurcation configurations (four treated and one hardwall) were fabricated and tested in the NASA Langley Curved Duct Test Rig. Results show that mode scattering may occur due to both the presence of the bifurcation, as well as variable impedance distributions on the bifurcation surface. Future work will also include optimization of bifurcation treatments for testing in the Curved Duct Test Rig. These initial results are promising and this work provides valuable information for further study and improvement of the performance of bifurcation acoustic treatments.

Nark, Douglas M.↗
NASA NTRS2023

The Friendly Argument Notation (FAN): 2023 Version

This document constitutes the official description of the current iteration of the Friendly Argument Notation (FAN). This new version provides several enhancements to the original 2020 instantiation, while maintaining essential compatibility with it. Specifically, the new version enables distinguishing between deductive and non-deductive arguments, removes the requirement for always providing an explicit statement of reasoning, and relaxes the rules for when labels may be used. The primary intended use of FAN is unchanged: creating and evaluating arguments about safety-critical systems, specifically the types of arguments common within safety and assurance cases.

language↗
NASA NTRSDate not supplied

A Fundamental Study of Bifurcation Acoustic Treatment Effects on Aft-Fan Engine Noise

Increasing air traffic and more stringent aircraft noise regulations continue to expand requirements on aircraft noise levels for conventional and unconventional aircraft configurations. A major component of the overall aircraft noise is the sound associated with the propulsion system mounted in the engine nacelle. Acoustic liners mounted in the aircraft engine nacelles provide a significant portion of the current fan noise reduction. However, they must be further optimized if challenging noise reduction goals are to be achieved. One location within the aft bypass duct that may be an excellent candidate for increased attention is the acoustic treatment on the engine bifurcations (i.e., engine pylon and lower bifurcation). This paper presents the continuation of a fundamental study of the effects of bifurcation treatment on simulated aft fan noise and the validation of numerical tools to predict such effects. Five bifurcation configurations (four treated and one hardwall) were fabricated and tested in the NASA Langley Curved Duct Test Rig. Results show that mode scattering may occur due to both the presence of the bifurcation, as well as variable impedance distributions on the bifurcation surface. Future work will also include optimization of bifurcation treatments for testing in the Curved Duct Test Rig. These initial results are promising and this work provides valuable information for further study and improvement of the performance of bifurcation acoustic treatments.

bifurcation effects↗
NASA NTRSDate not supplied

A Fundamental Study of Bifurcation Acoustic Treatment Effects on Aft-Fan Engine Noise

Increasing air traffic and more stringent aircraft noise regulations continue to expand requirements on aircraft noise levels for conventional and unconventional aircraft configurations. A major component of the overall aircraft noise is the sound associated with the propulsion system mounted in the engine nacelle. Acoustic liners mounted in the aircraft engine nacelles provide a significant portion of the current fan noise reduction. However, they must be further optimized if challenging noise reduction goals are to be achieved. One location within the aft bypass duct that may be an excellent candidate for increased attention is the acoustic treatment on the engine bifurcations (i.e., engine pylon and lower bifurcation). This paper presents the continuation of a fundamental study of the effects of bifurcation treatment on simulated aft fan noise and the validation of numerical tools to predict such effects. Five bifurcation configurations (four treated and one hardwall) were fabricated and tested in the NASA Langley Curved Duct Test Rig. Results show that mode scattering may occur due to both the presence of the bifurcation, as well as variable impedance distributions on the bifurcation surface. Future work will also include optimization of bifurcation treatments for testing in the Curved Duct Test Rig. These initial results are promising and this work provides valuable information for further study and improvement of the performance of bifurcation acoustic treatments.

bifurcation effects↗
NASA NTRSDate not supplied

A Fundamental Study of Bifurcation Acoustic Treatment Effects on Aft-Fan Engine Noise

Increasing air traffic and more stringent aircraft noise regulations continue to expand requirements on aircraft noise levels for conventional and unconventional aircraft configurations. A major component of the overall aircraft noise is the sound associated with the propulsion system mounted in the engine nacelle. Acoustic liners mounted in the aircraft engine nacelles provide a significant portion of the current fan noise reduction. However, they must be further optimized if challenging noise reduction goals are to be achieved. One location within the aft bypass duct that may be an excellent candidate for increased attention is the acoustic treatment on the engine bifurcations (i.e., engine pylon and lower bifurcation). This paper presents the continuation of a fundamental study of the effects of bifurcation treatment on simulated aft fan noise and the validation of numerical tools to predict such effects. Five bifurcation configurations (four treated and one hardwall) were fabricated and tested in the NASA Langley Curved Duct Test Rig. Results show that mode scattering may occur due to both the presence of the bifurcation, as well as variable impedance distributions on the bifurcation surface. Future work will also include optimization of bifurcation treatments for testing in the Curved Duct Test Rig. These initial results are promising and this work provides valuable information for further study and improvement of the performance of bifurcation acoustic treatments.

bifurcation effects↗
NASA NTRS2024

Forced Response Aeromechanics Analysis in MATLAB®-Based Environment Code With Application to Distortion-Tolerant Fan R24 Blade Geometry

Researchers at the NASA Glenn Research Center have developed a research-level code for forced response analysis for turbomachinery that provides a streamlined framework for aeromechanics analysis, as well as for generating Goodman diagrams. The Forced Response Aeromechanics Analysis in a MATLAB-Based Environment (FRAAME, Version 1) code is designed to accept blade surface unsteady pressure time histories generated by three-dimensional (3D) Unsteady Reynolds-Averaged Navier-Stokes (URANS) code TURBO and modal displacements, modal stresses, and static stresses generated via expanded ANSYS® (Ansys, Inc.) cyclic symmetry analysis. The code’s looping structure allows for largescale analyses, including many blade surface pressure files, modal displacements, and modal stress files for full annulus forced response analysis, including a modal summation method for multiple engine orders and modes. This code is applied to the R24 fan geometry for the Boundary Layer Ingesting Inlet/Distortion-Tolerant Fan (BLI2DTF) project, a propulsion system being developed to increase the fuel efficiency of future aircraft, to serve as validation of experimental data as well as external simulation results. This tool’s functional, modular form is intended to allow users to make modifications easily. Those modifications can include requests for information for any step in the analysis process, as well as adding various functions to compute additional information of interest. It is also written, given sufficient input information, as a general blade geometry forced response solver that is not necessarily specific to the R24 geometry but is used here for verification of code functionality and accuracy. Although forced response analysis tools are also available in commercially available code packages, the post-processing FRAAME code offers reliable, fast, and scalable forced response analysis and Goodman diagram generation for large cases utilizing, specifically, TURBO and ANSYS® results information in an effort to streamline forced response and high cycle fatigue analyses.

Aeromechanics↗
NASA NTRSDate not supplied

Astrobiological Potential of Rocks Acquired By the Perseverance Rover at the Front of the Western Sediment Fan in Jezero Crater, Mars.

Major objectives of the Perseverance rover mission include identifying past habitable environments, collecting rocks that are likely to preserve biosignatures and using the rover’s instruments to look for potential biosignatures in these rocks. The recognition of the > 3.5 billion-year old habitable environments in Jezero crater, Mars (Fig. 1); promised that the mission could achieve these objectives. The western sedimentary fan deposit, the hydrated minerals therein and the carbonate minerals at the margin of this fan were identified as particularly compelling areas in which to search for the signs of past life and collect the oldest aqueously deposited rocks from another planet.

Mars 2020↗
NASA NTRS2024

What Are the Olivine-Rich Boulders in the Upper Fan and Margin Unit at Jezero Crater, Mars?

Since February 2021, the Perseverance rover has explored Jezero Crater in the Nili Fossae region of Mars which hosts large outcrops of a regional olivine-carbonate unit. In the crater floor, Perseverance investigated two igneous formations: Máaz, composed of basaltic lava and/or pyroclastic flows, and Séítah, an olivine-rich cumulate] below Máaz. Then, Perseverance explored the western fan composed by diverse sedimentary rocks of variable composition, but often containing olivine On the upper fan and margin unit, Perseverance encountered number of centimetric to metric boulder rocks. Two main types of boulders were identified based on texture and composition: the olivine-rich and pyroxene-bearing boulders. Here, we use SuperCam data to describe the texture, geochemistry and mineralogy of the olivine-rich boulders. Then, we discuss their possible petrological origin and some possible implications for the regional Nili Fossae olivine-carbonate unit.

Mars 2020↗
NASA NTRSDate not supplied

Fan Noise Predictions of the NASA Source Diagnostic Test using Unsteady Simulations with LAVA Part II - Tonal and Broadband Noise Assessment

The NASA Source Diagnostic Test (SDT) campaign experimental data is used for validation of a sliding mesh technique recently implemented within the Launch, Ascent, and Vehicle Aerodynamics computational framework for time-accurate simulation of rotating fans. The far-field acoustics are analyzed in this work, building upon the aerodynamic validation studies previously published in Part I. Two modeling approaches are explored: the unsteady Reynolds-averaged Navier Stokes (uRANS) with the negative Spalart-Allmaras (SA-neg) turbulence model closure, and a hybrid Reynolds-averaged Navier Stokes/large-eddy simulation (RANS/LES) paradigm employing a zonal detached-eddy simulation (ZDES) closure with enhanced shielding protection. Two convective flux scheme approaches with different dissipation properties are also explored with ZDES. The Ffowcs-Williams and Hawkings (FW-H) permeable surface approach is used for propagation of the near-field acoustics to the far-field microphone locations. This work analyzes the low-speed (approach) condition, characterized by a fan rotation speed of 7808 rotations-per-minute (RPM). Three different grid levels ranging between 200 million and 1.1 billion grid points are considered. Results show good prediction of the broadband noise levels at sideline angles ranging between 70° and 110°. The forward arc observers show an under-prediction of the overall sound pressure levels (OASPL) even at the fine grid level. A breakdown of the inlet and exhaust contributions reveals a steep drop-off in the broadband noise levels past a blade-passing frequency (BPF) of 1.5, potentially caused by a lack of resolved small-scale turbulent fluctuations in the interstage region. Past 110° the OASPL are over-predicted by up to 10 dB due to an over-prediction of the low-frequency broadband noise levels in the aft arc. The detuning of BPF2 caused by small deviations in the blade stagger angle around the wheel is captured, and a corresponding decrease in the sound power level for this cut-on tone is observed.

AATT↗
NASA NTRS1963

CHARACTERISTICS OF LIFTING-FAN V/STOL AIRCRAFT

Wind-tunnel tests of full scale practical configuration of lifting fan v/stol aircraft show transition pitching moments comparable to conventional aircraft, and that lift increases with greater forward speed

LIFT FAN↗