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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Numerical Simulation of the Oscillations in a Mixer: An Internal Aeroacoustic Feedback System

The space-time conservation element and solution element method is employed to numerically study the acoustic feedback system in a high temperature, high speed wind tunnel mixer. The computation captures the self-sustained feedback loop between reflecting Mach waves and the shear layer. This feedback loop results in violent instabilities that are suspected of causing damage to some tunnel components. The computed frequency is in good agreement with the available experimental data. The physical phenomena are explained based on the numerical results.

Jorgenson, Philip C. E.↗
NASA NTRS2005

Cold Aero Performance of a Two-Dimensional Mixer Ejector Nozzle

Since 1986, NASA and the U.S. aerospace industry have been assessing the economic viability and environmental acceptability of a second-generation supersonic civil transport, or High Speed Civil Transport (HSCT). Environmental acceptability in terms of airport community noise and economic viability are critical elements in this endeavor. Development of a propulsion system that satisfies strict airport noise regulations (FAR36 Stage III levels), at acceptable performance and weight, is critical to the success of any HSCT program. Two-dimensional mixer-ejector (2DME) exhaust systems are one approach in achieving this goal. In support of HSCT development, GEAE (GE Aircraft Engines), under contract to the NASA Glenn Research Center, conducted this test program at the NASA Langley 16 ft transonic wind tunnel to evaluate the cold aerodynamic performance aspects of the 2DME exhaust system concept. The effects of SAR (SAR, suppressor area ratio, = mixed-flow area/primary nozzle throat area), MAR (MAR = overall exhaust system exit/mixing-plane area), flap length, CER (suppressor chute expansion ratio), chute alignment, and free stream Mach number were investigated on a 1/11th cold aerodynamic scale model of a 2DME exhaust system.

Balan, C.↗
NASA NTRS2005

Quadrant CFD Analysis of a Mixer-Ejector Nozzle for HSCT Applications

This study investigates the sidewall effect on flow within the mixing duct downstream of a lobed mixer-ejector nozzle. Simulations which model only one half-chute width of the ejector array are compared with those which model one complete quadrant of the nozzle geometry and with available experimental data. These solutions demonstrate the applicability of the half-chute technique to model the flowfield far away from the sidewall and the necessity of a full-quadrant simulation to predict the formation of a low-energy flow region near the sidewall. The quadrant solutions are further examined to determine the cause of this low-energy region, which reduces the amount of mixing and lowers the thrust of the nozzle. Grid resolution and different grid topologies are also examined. Finally, an assessment of the half-chute and quadrant approaches is made to determine the ability of these simulations to provide qualitative and/or quantitative predictions for this type of complex flowfield.

Yoder, Dennis A.↗
NASA NTRS2002

Transonic Resonance Demonstrated To Be a Source of Internal Noise From Mixer-Ejector Nozzles

During noise field studies with mixer-ejector nozzles in NASA's High-Speed Research program, tones were often encountered. The tones would persist in the simulated "cutback" condition (shortly after takeoff). Unfortunately, we did not understand their origin and, thus, could not develop a logical approach for suppressing them. We naturally questioned whether or not some of those tones were due to the transonic resonance. This was studied with a 1/13th scale model of the High-Speed Civil Transport nozzle. The first objective was to determine if indeed tones could be detected in the radiated noise. The next objective was to diagnose if those tones were due to the transonic resonance. Agreement of the frequencies with the correlation equation and the effect of boundary layer tripping were to be used in the diagnosis.

Zaman, Khairul B.↗
NASA NTRS2006

Acoustic Characteristics of Various Treatment Panel Designs Specific to HSCT Mixer-Ejector Application

The development process of liner design methodology is described in several reports. The results of the initial effort of concept development, screening, laboratory testing of various liner concepts, and preliminary correlation (generic data) are presented in a report Acoustic Characteristics of Various Treatment Panel Designs for HSCT Ejector Liner Acoustic Technology Development Program. The second phase of laboratory test results of more practical concepts and their data correlations are presented in this report (product specific). In particular, this report contains normal incidence impedance measurements of several liner types in both a static rig and in a high temperature flow duct rig. The flow duct rig allows for temperatures up to 400 F with a grazing flow up to Mach 0.8. Measurements of impedance, DC flow resistance, and in the flow rig cases, impact of the liner on boundary layer profiles are documented. In addition to liner rig tests, a limited number of tests were made on liners installed in a mixer-Ejector nozzle to confirm the performance of the liner prediction in an installed configuration.

Salikuddin, M.↗
NASA NTRS1994

Sound suppression mixer

A gas turbine engine flow mixer includes at least one chute having first and second spaced apart sidewalls joined together at a leading edge, with the sidewalls having first and second trailing edges defining therebetween a chute outlet. The first trailing edge is spaced longitudinally downstream from the second trailing edge for defining a septum in the first sidewall extending downstream from the second trailing edge. The septum includes a plurality of noise attenuating apertures.

Brown, William H.↗
NASA NTRS1991

Multiplying video mixer system

A multiplying video mixer system including a digital signal generator for generating at least one overlay signal and an attribute control bit corresponding to each of a plurality of pixels. A background signal generator generates input background signals to which the attribute control bits are applied to effect the input background signals with a desired opaque/transparent attribute. At least one video multiplier multiplies the overlay attribute signals and background signals to produce an output video signal having an amplitude equal to the product of the amplitudes of the overlay and background signals.

Heckt, Neil W.↗
NASA NTRS2005

Progress on a Multichannel, Dual-Mixer Stability Analyzer

Several documents describe aspects of the continuing development of a multichannel, dual-mixer system for simultaneous characterization of the instabilities of multiple precise, low-noise oscillators. One of the oscillators would be deemed to be a reference oscillator, its frequency would be offset by an amount (100 Hz) much greater than the desired data rate, and each of the other oscillators would be compared with the frequency-offset signal by operation of a combination of hardware and software. A high-rate time-tag counter would collect zero-crossing times of the approximately equal 100-Hz beat notes. The system would effect a combination of interpolation and averaging to process the time tags into low-rate phase residuals at the desired grid times. Circuitry that has been developed since the cited prior article includes an eight-channel timer board to replace an obsolete commercial time-tag counter, plus a custom offset generator, cleanup loop, distribution amplifier, zero-crossing detector, and frequency divider.

Kirk, Albert↗
NASA NTRS2017

Liquid-Gas Mixer and Turbulator Therefor

Disclosed is a liquid-gas mixer including a central passageway provided about an injector axis, and first and second gas passageways. The first gas passageway is radially outward of the central passageway and radially inward of the second gas passageway. A turbulator is provided between the first and second gas passageways, and includes a plurality of first disturbance generators and a plurality of second disturbance generators. The first and second disturbance generators are provided about the turbulator in an alternating arrangement.

Brown, Christopher James↗
NASA NTRS2018

XY vs X Mixer in Quantum Alternating Operator Ansatz for Optimization Problems with Constraints

Quantum Approximate Optimization Algorithm, further generalized as Quantum Alternating Operator Ansatz (QAOA), is a family of algorithms for combinatorial optimization problems. It is a leading candidate to run on emerging universal quantum computers to gain insight into quantum heuristics. In constrained optimization, penalties are often introduced so that the ground state of the cost Hamiltonian encodes the solution (a standard practice in quantum annealing). An alternative is to choose a mixing Hamiltonian such that the constraint corresponds to a constant of motion and the quantum evolution stays in the feasible subspace. Better performance of the algorithm is speculated due to a much smaller search space. We consider problems with a constant Hamming weight as the constraint. We also compare different methods of generating the generalized W-state, which serves as a natural initial state for the Hamming-weight constraint. Using graph-coloring as an example, we compare the performance of using XY model as a mixer that preserves the Hamming weight with the performance of adding a penalty term in the cost Hamiltonian.

quantum computing↗