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NASA NTRS1993

An experimental investigation of S-duct flow control using arrays of low-profile vortex generators

An experimental investigation was undertaken to measure the effect of various configurations of low-profile vortex generator arrays on the flow in a diffusing S-duct. Three parameters that characterize the vortex generator array were systematically varied to determine their effect: (1) the vortex generator height; (2) the streamwise location of the vortex generator array; and (3) the vortex generator spacing. Detailed measurements of total pressure at the duct exit, surface static pressure, and surface flow visualization were gathered for each vortex generator configuration. These results are reported here along with total pressure recovery and distortion coefficients determined from the experimental data. Each array of vortex generators tested improved total pressure recovery. The configuration employing the largest vortex generators was the most effective in reducing total pressure recovery. No configuration of vortex generators completely eliminated the flow separation that naturally occurs in the S-duct, however the extent of the separated flow region was reduced.

Reichert, Bruce A.↗

NASA NTRS1996

[Two-phase Interfaces in Weak External Fields]

Our aim has been that of understanding from first principles the behavior of two-phase interfaces in the absence of gravitational constraints. This is fundamental to our ability to deal with the fluid structures that abound in the real biological, chemical, and physical world. A substantial effort was mounted to determine how familiar hydrodynamic concepts have to be modified and interpreted to make them appropriate to the multi-level structure alluded to above. This was primarily in the context of the microscopic symmetric pressure tensor, which was, for the first time, expressed in the invaluable density functional format, and the used to follow the predictions of popular microscopic models of the energetics of interfacial systems. In the course of these investigations, the previous murky relation between pressure tensor and thermodynamics was completely clarified. The process of extending thermodynamic information to interfacial dynamics was initiated along two paths. One was from the viewpoint of an inertialess lattice gas, resulting in the surprising conclusion that at this level, all transport is governed by precisely the thermodynamic free energy, albeit with a non-trivial effective particle mobility. The other aimed at understanding the fashion in which slow macroscopic motions, accounted for by a time-varying microscopic energy, generate effective hydrodynamic parameters. By examining a solvable model system, it was found that all current procedures for doing so are deficient, and suitable alleviation suggested. The major effect of this project was to set the stage for the analysis of the substantial dynamical regimes in which extensive equilibrium information provides the dominant background. This produces a smooth junction to the models of Araki and Munakata, Giacomin and Lebowitz, and Oxtoby. It is also crucial to our understanding of the complex interfacial equilibrium configurations required for intermediate stages of two-phase separation, for which the "phase-field" techniques we have been developing are uniquely effective. And it puts us within striking range of the physical experiments that can provide incisive tests of the theoretical framework.

Percus, J. K.↗

NASA NTRS2002

Experimental Investigation of Transition to Turbulence as Affected by Passing Wakes

Experimental results from a study of the effects of passing wakes upon laminar-to-turbulent transition in a low-pressure turbine passage are presented. The test section geometry is designed to simulate the effects of unsteady wakes resulting from rotor-stator interaction upon laminar-to-turbulent transition in turbine blade boundary layers and separated flow regions over suction surfaces. Single-wire, thermal anemometry techniques were used to measure time-resolved and phase-averaged, wall-normal profiles of velocity, turbulence intensity, and intermittency at multiple streamwise locations over the turbine airfoil suction surface. These data are compared to steady state, wake-free data collected in the same geometry to identify the effects of wakes upon laminar-to-turbulent transition. Results are presented for flows with a Reynolds number based on suction surface length and exit velocity of 50,000 and an approach flow turbulence intensity of 2.5 percent. From these data, the effects of passing wakes and associated increased turbulence levels and varying pressure gradients on transition and separation in the near-wall flow are presented. The results show that the wakes affect transition both by virtue of their difference in turbulence level from that of the free-stream but also by virtue of their velocity deficit relative to the freestream velocity, and the concomitant change in angle of attack and temporal pressure gradients. The results of this study seem to support the theory that bypass transition is a response of the near-wall viscous layer to pressure fluctuations imposed upon it from the free-stream flow. The data also show a significant lag between when the wake is present over the surface and when transition begins. The accompanying CD-ROM includes tabulated data, animations, higher resolution plots, and an electronic copy of this report.

Kaszeta, Richard W.↗

NASA NTRS2002

Superfinished Surfaces for Power Transfer Systems Improvement

The continuous demands for high performance and lightweight power train systems resulted in requirements for higher power density gearing systems. However, increasing the load bearing capacity of the gear teeth, without increasing size, places stringent requirements upon metallurgy, dimensional control, and surface finish of the final products. In order to operate the mating parts near the upper bounds of their theoretical design envelope, manufacturing processes are required that are capable of improving the fatigue life and load bearing capacity of precision parts, while producing the required geometric accuracy. Results of the recent experimental studies indicate that the super finishing process is able to achieve these goals. This paper will review the results of our continuing evaluation of the super finish process as applied to aerospace gearing. Two separate evaluations were performed on gears to examine the effects of super finishing on resistance to both pitting and contact fatigue. For the reported experiments, both conventional and super finished test gears were simultaneously manufactured using the same process and the same heat lot of materials. This paper will also provide a brief description of the manufacturing technology used to achieve the results and will compare the results with other published data. In addition, this paper presents a couple of off-the-shelf manufacturing technologies that have been successfully used to super finish test specimens and will provide a glimpse of other emerging super finishing technologies. This is a US Army Manufacturing Technology project. The project was sponsored by the Aviation and Missiles Command (AMCOM) and was being managed and conducted by IIT Research Institute.

Niskanen, Paul↗

NASA NTRS2007

Experimental Investigation of Transition to Turbulence as Affected by Passing Wakes: Effects of High FSTI and Increased Rod Spacing

Experimental results from a study of the effects of passing wakes upon laminar-to-turbulent transition in a low-pressure turbine passage are presented. The test section geometry is designed to simulate the effects of unsteady wakes resulting from rotor-stator interaction upon laminar-to-turbulent transition in turbine blade boundary layers and separated flow regions over suction surfaces. Single-wire, thermal anemometry techniques are used to measure time-resolved and phase-averaged, wall-normal profiles of velocity, turbulence intensity and intermittency at multiple streamwise locations over the turbine airfoil suction surface. The Reynolds number based on suction surface length and stage exit velocity is 50,000. This study compares a previously documented base case flow having an approach flow turbulence intensity of 2.5 percent and a wake passing Strouhal number of 0.792 to two additional cases: one having an increased rod spacing case having a wake passing Strouhal number of 0.396, and another having an elevated approach flow turbulence intensity of 10 percent. From these data, the effects of increased rod spacing and elevated FSTI upon transition and separation processes in the near-wall flow are documented. The results show that a decreased wake passing Strouhal number results in an earlier separation with a larger separation bubble, while the elevated FSTI results in earlier separation, but with a shorter, thinner, separation bubble. The data and animations are included in an accompanying CD ROM.

Kaszeta, Richard W.↗

NASA NTRS2002

Experimental Investigation of Transition to Turbulence as Affected by Passing Wakes

Experimental results from a study of the effects of passing wakes upon laminar-to-turbulent transition in a low-pressure turbine passage are presented. The test section geometry is designed to simulate the effects of unsteady wakes resulting from rotor-stator interaction upon laminar-to-turbulent transition in turbine blade boundary layers and separated flow regions over suction surfaces. Single-wire, thermal anemometry techniques were used to measure time- resolved and phase-averaged, wall-normal profiles of velocity, turbulence intensity, and intermittency at multiple streamwise locations over the turbine airfoil suction surface. These data are compared to steady state, wake-free data collected in the same geometry to identify the effects of wakes upon laminar-to-turbulent transition. Results are presented for flows with a Reynolds number based on suction surface length and exit velocity of 50,000 and an approach flow turbulence intensity of 2.5 percent. From these data, the effects of passing wakes and associated increased turbulence levels and varying pressure gradients on transition and separation in the near-wall flow are presented. The results show that the wakes affect transition both by virtue of their difference in turbulence level from that of the free-stream but also by virtue of their velocity deficit relative to the freestream velocity, and the concomitant change in angle of attack and temporal pressure gradients. The results of this study seem to support the theory that bypass transition is a response of the near-wall viscous layer to pressure fluctuations imposed upon it from the free-stream flow. The data also show a significant lag between when the wake is present over the surface and when transition begins. The accompanying CD-ROM includes tabulated data, animations, higher resolution plots, and an electronic copy of this report.

Kaszeta, Richard W.↗

NASA NTRS2016

Demonstration of Robustness and Integrated Operation of a Series-Bosch System

Manned missions beyond low Earth orbit will require highly robust, reliable, and maintainable life support systems that maximize recycling of water and oxygen. Bosch technology is one option to maximize oxygen recovery, in the form of water, from metabolically-produced carbon dioxide (CO2). A two stage approach to Bosch, called Series-Bosch, reduces metabolic CO2 with hydrogen (H2) to produce water and solid carbon using two reactors: a Reverse Water-Gas Shift (RWGS) reactor and a carbon formation (CF) reactor. Previous development efforts demonstrated the stand-alone performance of a RWGS reactor containing Incofoam(TradeMark) catalyst and designed for robustness against carbon formation, two membrane separators intended to maximize single pass conversion of reactants, and a batch CF reactor with both transit and surface catalysts. In the past year, Precision Combustion, Inc. (PCI) developed and delivered a RWGS reactor for testing at NASA. The reactor design was based on their patented Microlith(TradeMark) technology and was first evaluated under a Phase I Small Business Innovative Research (SBIR) effort in 2010. The Microlith(TradeMark) RWGS reactor was recently evaluated at NASA to compare its performance and operating conditions with the Incofoam(TradeMark) RWGS reactor. Separately, in 2015, a fully integrated demonstration of an S-Bosch system was conducted. In an effort to mitigate risk, a second integrated test was conducted to evaluate the effect of membrane failure on a closed-loop Bosch system. Here, we report and discuss the performance and robustness to carbon formation of both RWGS reactors. We report the results of the integrated operation of a Series-Bosch system and we discuss the technology readiness level. 1

Abney, Morgan B.↗

NASA NTRS2011

Performance of a Kilowatt-Class Stirling Power Conversion System in a Thermodynamically Coupled Configuration

A pair of 1-kWe free-piston Stirling power convertors has been modified into a thermodynamically coupled configuration, and performance map testing has been completed. This is the same configuration planned for the full-scale 12-kWe power conversion unit (PCU) that will be used in the Fission Power System Technology Demonstration Unit (TDU). The 1-kWe convertors were operated over a range of conditions to evaluate the effects of thermodynamic coupling on convertor performance and to identify any possible control challenges. The thermodynamically coupled convertor showed no measureable difference in performance from the baseline data collected when the engines were separate, and no major control issues were encountered during operation. The results of this test are guiding controller development and instrumentation selection for the TDU.

Geng, Steven M.↗

NASA NTRS1997

Inlet Shape Effects on the Far-Field Sound of a Model Fan

A wind tunnel test was conducted to determine the effects of inlet shape on fan radiated noise. Four inlet geometries, which included a long standard flight type inlet, a short, aggressive flight inlet a scarf inlet, and an elliptical inlet were investigated in the study. The fan model used in the study was a 0.1 scale of the Pratt and Whitney Advanced Ducted Propeller (ADP), an ultra high bypass ratio turbofan engine. Acoustic data are presented for a fan speed of 70% (12,000 rpm) and a tunnel speed of 0.10 Mach number, The fan was configured with a 16-bladed rotor and a 40 stator vane set that were separated by 2.0 chord lengths. The radiated noise was measured with 15 microphones on a boom that traversed the length of the tunnel test section. Data from these microphones are presented in the form of sideline angle directivity plots. Noise associated with the test inlets was also predicted using a ray acoustics code. Inlet shape has been found to have a significant effect on both tone and broadband noise, and the non-axisymmetric inlet shape can be used for a noise reduction method.

Clark, L. R.↗

NASA NTRS1958

Large-Scale Wind-Tunnel Tests of an Airplane Model with an Unswept, Aspect-Ratio-10 Wing, Two Propellers, and Blowing Flaps

An investigation was made to determine the lifting effectiveness and flow requirements of blowing over the trailing-edge flaps and ailerons on a large-scale model of a twin-engine, propeller-driven airplane having a high-aspect-ratio, thick, straight wing. With sufficient blowing jet momentum to prevent flow separation on the flap, the lift increment increased for flap deflections up to 80 deg (the maximum tested). This lift increment also increased with increasing propeller thrust coefficient. The blowing jet momentum coefficient required for attached flow on the flaps was not significantly affected by thrust coefficient, angle of attack, or blowing nozzle height.

Griffin, Roy N., Jr.↗

DOE OSTI2021

Progress Report on Performance of A709 and G91 Steels in Sodium

Specimens in six different processing and heat treatment conditions of A709 H58776 were exposed to sodium at 550, 600, and 650°C, respectively for various exposure times. G91 base metal was tested in sodium at 550, 600, and 650°C, and G91 weldment at 550 and 600°C, respectively. Parallel thermal aging experiments were conducted on G91 and A709 to obtain thermal aging data for comparison with sodium exposure results to separate the thermal and sodium effects. The corrosion data obtained on A709 steel continue to show low corrosion rates, which indicate good compatibility of A709 with sodium when oxygen content is controlled. G91 has also shown acceptable corrosion rates over the temperature range of 550-650°C in sodium. Thermal aging or sodium exposures reduced the tensile strength, uniform elongation, and total elongation for A709 ESR, AOD specimens. These specimens consistently showed higher yield stress and tensile strength and lower uniform and total elongations after sodium exposure than after thermal aging under comparable testing conditions. It implies that there was an additional effect of sodium exposure that gave rise to an increase in tensile strength of A709. Dynamic strain aginginduced flow serrations were completely removed by either thermal aging or sodium exposure at 650°C, which imply that carbon or nitrogen in solution was removed from the solution and formed precipitates during aging or sodium exposures. The tensile data ruled out the possibility of decarburization under the sodium exposure conditions. The HOMO specimens behaved somewhat differently from the ESR and AOD specimens in sodium. While thermal aging and sodium exposures at 550 and 600°C decreased the yield stress and the ultimate tensile strength of G91, there was virtually no additional effect resulting from sodium exposures at these two temperatures. In contrast, sodium exposures at 650°C had a drastic effect on the yield stress and the ultimate tensile strength of G91. It is suggested that G91 experienced decarburization in the 650°C sodium environments. Carbon concentrations in sodium in the SMT-1 and SMT-2 loops were determined by a foil equilibration method. The estimated carbon concentration was in the range of 0.8-1.2 ppm in the SMT-1 loop and 0.3-0.7 ppm in the SMT-2 loop. The carbon activity in sodium in the SMT-2 loop was estimated to be 0.03-0.08 at 600°C, and 0.08-0.2 at 550°C. The carbon activity in sodium at 650°C in the SMT-1 loop was 0.04-0.07. Equilibrium simulation of the carburization – decarburization processes was conducted for A709 and G91 steels exposed in sodium environments at temperatures of 550-700°C. The carbon activity-concentration relationship for G91 was re-evaluated by considering four phases in G91, i.e. bcc ferrite, M 23 C 6 , NbC and VC carbides. It was found that the carburization-decarburization process in G91 steel was dictated by M 23 C 6 carbides at high carbon activities, while NbC carbides dominated the process at low carbon activities. Formation of NbC increases the decarburization resistance of G91 steel. It remains to be understood whether the decarburization resistance provided by MC carbides in G91 can be maintained during long-term operations of SFRs. The carbon concentration-activity relationship for A709 was calculated based on the equilibrium of fcc-austenite and M 23 C 6 carbide phase. The calculations showed that A709 decarburizes at 650°C in the SMT-1 loop environments, which is different from the experimental findings. The carbon concentration-activity relationship in A709 was further evaluated by considering four phases, including fcc-austenite, M 23 C 6 , NbC, and TiC carbide phases. TiC is the most stable carbides among the three carbide phases. The carburization-decarburization process in A709 is dictated by M 23 C 6 carbides at high carbon activities and by TiC at low carbon activities. Formation of TiC increases the decarburization resistance of A709 steel. Because of the complexity of the precipitation process in A709 during sodium exposures, detailed characterization of precipitates in sodium-exposed specimens and improved thermodynamic models are needed to understand the carburization-decarburization behavior of A709. Kinetic analysis of carbon transfer will be investigated for G91 and A709 in future work.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

NASA NTRS2018

Steady and Unsteady Excitation of Separated Flow over the NASA Hump Model

Separated flow and its control over the NASA hump model were investigated at subsonic speeds. Three-dimensional, unsteady fluid dynamic simulations were supplemented by wind tunnel measurements. Flow control was implemented by means of spatially distributed discrete jets operating in steady and unsteady modes. The effects of excitation amplitude and frequency were studied numerically and experimentally. Several integral parameters were explored as quality metrics. In addition to the existing ones, two new integral parameters, which are slightly modified versions of the normal force and moment coefficients, were introduced. These two parameters together with pressure drag coefficient were found to be well correlated with the flow control and used in the performance evaluation of different flow control methods including, zero net mass flux actuators, steady suction, sweeping jet actuators, and the currently studied steady and unsteady excitations. For the cases tested, it was found that the unsteady excitation is superior to the steady excitation and slightly better than the sweeping jet actuators whereas the steady suction was found to be the most effective. Although the numerical simulations overpredict the separation bubble, these simulations capture the salient features of flow separation control and hence help us to understand the effect of steady/unsteady excitation on the separated flow.

Koklu, Mehti↗

NASA NTRS1987

A vector-based failure detection and isolation algorithm for a dual fail-operational redundant strapdown inertial measurement unit

A vector-based failure detection and isolation technique for a skewed array of two degree-of-freedom inertial sensors is developed. Failure detection is based on comparison of parity equations with a threshold, and isolation is based on comparison of logic variables which are keyed to pass/fail results of the parity test. A multi-level approach to failure detection is used to ensure adequate coverage for the flight control, display, and navigation avionics functions. Sensor error models are introduced to expose the susceptibility of the parity equations to sensor errors and physical separation effects. The algorithm is evaluated in a simulation of a commercial transport operating in a range of light to severe turbulence environments. A bias-jump failure level of 0.2 deg/hr was detected and isolated properly in the light and moderate turbulence environments, but not detected in the extreme turbulence environment. An accelerometer bias-jump failure level of 1.5 milli-g was detected over all turbulence environments. For both types of inertial sensor, hard-over, and null type failures were detected in all environments without incident. The algorithm functioned without false alarm or isolation over all turbulence environments for the runs tested.

Morrell, Frederick R.↗

NASA NTRS1995

First flight test results of the Simplified Aid For EVA Rescue (SAFER) propulsion unit

The Simplified Aid for EVA Rescue (SAFER) is a small, self-contained, propulsive-backpack system that provides free-flying mobility for an astronaut engaged in a space walk, also known as extravehicular activity (EVA.) SAFER contains no redundant systems and is intended for contingency use only. In essence, it is a small, simplified version of the Manned Maneuvering Unit (MMU) last flown aboard the Space Shuttle in 1985. The operational SAFER unit will only be used to return an adrift EVA astronaut to the spacecraft. Currently, if an EVA crew member inadvertently becomes separated from the Space Shuttle, the Orbiter will maneuver to within the crew member's reach envelope, allowing the astronaut to regain contact with the Orbiter. However, with the advent of operations aboard the Russian MIR Space Station and the International Space Station, the Space Shuttle will not be available to effect a timely rescue. Under these conditions, a SAFER unit would be worn by each EVA crew member. Flight test of the pre-production model of SAFER occurred in September 1994. The crew of Space Shuttle Mission STS-64 flew a 6.9 hour test flight which included performance, flying qualities, systems, and operational utility evaluations. We found that the unit offers adequate propellant and control authority to stabilize and enable the return of a tumbling/separating crew member. With certain modifications, production model of SAFER can provide self-rescue capability to a separated crew member. This paper will present the program background, explain the flight test results and provide some insight into the complex operations of flight test in space.

Meade, Carl J.↗

DOE OSTI2020

Polyphenol-Sensitized Atomic Layer Deposition for Membrane Interface Hydrophilization

Improvements in energy-water systems will necessitate fabrication of high-performance separation membranes. To this end, interface engineering is a powerful tool for tailoring properties, and atomic layer deposition (ALD) has recently emerged as a promising and versatile approach. However, most non-polar polymeric membranes are not amenable to ALD processing due to the absence of nucleation sites. Here, a sensitization strategy for ALD-coating is presented, illustrated by membrane interface hydrophilization. Facile dip-coating with polyphenols effectively sensitizes hydrophobic polymer membranes to TiO2 ALD coating. Tannic acid-sensitized ALD-coated membranes exhibit outstanding underwater crude oil repulsion and rigorous mechanical stability through bending and rinsing tests. As a result, these membranes demonstrate outstanding crude oil-in-water separation and reusability compared to untreated membranes or those treated with ALD without polyphenol pretreatment. A possible polyphenol-sensitized ALD mechanism is proposed involving initial island nucleation followed by film intergrowth. This polyphenol sensitization strategy enriches the functionalization toolbox in material science, interface engineering, and environmental science.

36 MATERIALS SCIENCE↗

DOE OSTI2020

V28 Test Report

The V28 containment vessel was procured by the US Army Recovered Chemical Material Directorate (RCMD) as a replacement vessel for use on the P2 Explosive Destruction Systems. It is the fourth EDS vessel to be fabricated under Code Case 2564 of the ASME Boiler and Pressure Vessel Code, which provides rules for the design of impulsively loaded vessels. The explosive rating for the vessel, based on the Code Case, is nine (9) pounds TNT- equivalent for up to 637 detonations. This report documents the results of explosive tests that were done on the vessel at Sandia National Laboratories in Albuquerque New Mexico to qualify the vessel for explosive use. The primary qualification test consisted of six, 1.5 pounds charges of Composition C-4 (equivalent to 11.25 pounds TNT) distributed around the vessel in accordance with the User Design Specification. This test was repeated due to a lack of proper clamp settings. Two additional tests using less explosive were performed, one identical in configuration to a test performed in the V27 qualification series as a baseline for comparison, and one where the separation distance of the charges was increased to extend the V27 analysis of distributed load effects on the P2 vessel. All vessel acceptance criteria were met.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗

NASA NTRS1985

Strategies for analyzing mixed pixels in remotely sensed imagery

Two uncalibrated synthetic aperture radar (SAR) scenes from Death Valley, California, and two uncalibrated scenes from Owens Valley, California, were used to test a technique to identify and separate the primary factors associated with multipolarized radar image sets. Unique to the technique is the concept that varied types of radar polarization signatures are a result of the interaction of a few physical factors (e.g., roughness, volume scattering, and dielectric constant). Thus, the varied signatures observed in an image reflect the interaction between these factors. The objectives are to first separate the interaction of factors directly influencing the measurement and to attempt to identify these factors. Interpretation of the SAR image sets proceeds by testing models that hypothesize the cause and effect relations between those factors directly affecting the radar measurement and those features of interest to the interpreter. The results of our analysis indicated two consistent endmember types over all four image scenes. These types are defined by a high flat polarized signature near a level of 255 DN and a low level flat signature near 0 DN for all polarizations. Four other endmember types were also isolated. The spatial distribution of these endmember types indicates possible correspondence to surface volume scattering and changes in surface dielectric. However, the shapes of these endmember types were different from scene to scene.

Smith, M.↗

NASA NTRS1986

Flight experiences with laminar flow

A review of natural laminar flow (NLF) flight experiences over the period from the 1930's to the present has been given to provide information on the achievability and maintainability of NLF in typical airplane operating environments. Significant effects of loss of laminar flow on airplane performance have been observed for several airplanes, indicating the importance of providing information on these changes to laminar flow airplane operators. Significant changes in airplane stability and control and maximum lift were observed in flight experiments with the loss of laminar flow. However, these effects can be avoided by proper selection of airfoils. Conservative laminar flow airfoil designs should be employed which do not experience significant loss of lift (caused by flow separation) upon the loss of laminar flow. Mechanisms have been observed for the effects of insect accumulation, flight through clouds and precipitation, and propeller slipstreams on laminar flow behavior. Fixed transition testing, in addition to free transition testing, is recommended as a new standard procedure for airplanes with surfaces designed to support laminar flow.

Holmes, Bruce J.↗