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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Characterization of Deficiencies in the Frequency Domain Forced Response Analysis Technique for Supersonic Turbine Bladed Disks

Turbine blades in rocket and jet engine turbomachinery experience enormous harmonic loading conditions. These loads result from the integer number of upstream and downstream stator vanes as well as the other turbine stages. Assessing the blade structural integrity is a complex task requiring an initial characterization of whether resonance is possible and then performing a forced response analysis if that condition is met. The standard technique for forced response analysis in rocket engine turbines is to decompose a computational fluid dynamics (CFD).generated flow field into its harmonic components, and to then perform a frequency response analysis at the problematic natural frequencies using cyclically symmetric structural dynamic models. Recent CFD analysis and water-flow testing at NASA/MSFC, though, indicates that this technique may miss substantial harmonic and non ]harmonic excitation sources that become present in complex flows. This complex content can only be captured by a CFD flow field encompassing at least an entire revolution. A substantial development effort to create a series of software programs to enable application of the 360 degree forcing function in a frequency response analysis on cyclic symmetric models has been completed (to be described in a future paper), but the question still remains whether the frequency response analysis itself is capable of capturing the excitation content sufficiently. Two studies comparing frequency response analysis with transient response analysis, therefore, of bladed-disks undergoing this complex flow environment have been performed. The first is of a bladed disk with each blade modeled by simple beam elements and the disk modeled with plates (using the finite element code MSC/NASTRAN). The focus of this model is to be representative of response of realistic bladed disks, and so the dimensions are roughly equivalent to the new J2X rocket engine 1st stage fuel pump turbine. The simplicity of the model allows the CFD load to be able to be readily applied, along with analytical and experimental variations in both the temporal and spatial fourier components of the excitation. In addition, this model is a first step in identifying response differences between transient and frequency forced response analysis techniques. The second phase assesses this difference for a much more realistic solid model of a bladed-disk in order to evaluate the effect of the spatial variation in loading on blade dominated modes. Neither research on the accuracy of the frequency response method when used in this context or a comprehensive study of the effect of test-observed variation on blade forced response have been found in the literature, so this research is a new contribution to practical structural dynamic analysis of gas turbines. The primary excitation of the upstream nozzles interacts with the blades on fuel pump of the J2X causes the 5th Nodal diameter modes to be excited, as explained by Tyler and Sofrin1, so a modal analysis was first performed on the beam/plate model and the 5ND bladed-disk mode at 40167 hz was identified and chosen to be the one excited at resonance (see figure 1). The first forced response analysis with this model focuses on identifying differences between frequency and transient response analyses. A hypothesis going into the analysis was that perhaps the frequency response was enforcing a temporal periodicity that did not really exist, and so therefore it would overestimate the response. As high dynamic response was a considerable source of stress in the J2X, examining this concept could potentially be beneficial for the program.

Brown, Andrew M.↗
DOE OSTI2016

Bench-Scale Testing and Process Performance Projections of CO2 Capture by CO2–Binding Organic Liquids (CO2BOLs) With and Without Polarity-Swing-Assisted Regeneration

This manuscript provides a detailed analysis of a continuous flow, bench scale study of the CO2BOL solvent platform with and without its Polarity Swing Assisted Regeneration (PSAR). This study encompassed four months of continuous flow testing of a candidate CO2BOL with a thermal regeneration and PSAR regeneration using decane antisolvent. In both regeneration schemes, steady state capture of >90 %CO2 was achieved using simulated flue gas at acceptable L/G ratios. Aspen Plus™ modeling was performed to assess process performance compared to previous equilibrium performance projections. This paper also includes net power projections, and comparisons to DOE’s Case 10 amine baseline.

Zheng, Feng↗
NASA NTRS1974

Effects of surface roughness on the aerodynamic characteristics of the modified 089 B shuttle orbiter at Mach 6 (LA15)

A one hundredth scale model of the modified 089B shuttle orbiter was tested in the Langley 20-Inch Mach 6 tunnel. Force and moment, surface pressure and oilflow data were obtained on one model, and phase-change coating data were obtained on another. The pressure tests were conducted first; the tubes were clipped near the base of the model and then the force and moment and oil flow tests conducted. Angles of attack for the tests were from 20 deg to 35 deg and are commensurate with the range of flight values from entry down to Mach 5. The design flight Reynolds number at Mach 6, based on model length, was 15 million, which could not be obtained in the tunnel; therefore, the tests were conducted at the highest and lowest values for this model in the tunnel, 9.4 million and 4.0 million, respectively, to indicate Reynolds number effects. Two control deflection combinations, representative of the bank and pitch control limits of the design flight trajectory, were used.

Ashby, G. C., Jr.↗
NASA NTRS1974

ATM test and integration

The test and checkout philosophy of the test program for the Skylab ATM module and the overall test flow including in-process, post-manufacturing, vibration, thermal vacuum, and prelaunch checkout activities are described. Capabilities and limitations of the test complex and its use of automation are discussed. Experiences with the organizational principle of using a dedicated test team for all checkout activities are reported. Material on the development of the ATM subsystems, the experimental program and the requirements of the scientific community, and the integration and verification of the complex systems/subsystems of the ATM are presented. The performance of the ATM test program in such areas as alignment, systems and subsystems, contamination control, and experiment operation is evaluated. The conclusions and recommendations resulting from the ATM test program are enumerated.

Moore, J. W.↗
NASA NTRS1993

Corrections to fringe distortion due to flow density gradients in optical interferometry

An analytical method is formulated to account for distortions of optical interferograms used for studies of flow over airfoils experiencing dynamic stall. It is shown that such distortions are generated primarily due to optical path deflections in the test flow, caused by large density gradients. Such in-flow optical path deflections are neglected in conventional optical techniques for flow studies. The present method employs a ray analysis to determine these in-flow optical path deflections, and accurately predicts the interferogram distortions.

Cho, Y. C.↗
NASA NTRS2005

The Importance of Detailed Component Simulations in the Feedsystem Development for a Two-Stage-to Orbit Reusable Launch Vehicle

To meet the requirements for the 2nd Generation Reusable Launch Vehicle (RLV), a unique propulsion feed system concept was identified using crossfeed between the booster and orbiter stages that could reduce the Two-Stage-to-Orbit (TSTO) vehicle weight and development cost by approximately 25%. A Main Propulsion System (MPS) crossfeed water demonstration test program was configured to address all the activities required to reduce the risks for the MPS crossfeed system. A transient, one-dimensional system simulation was developed for the subscale crossfeed water flow tests. To ensure accurate representation of the crossfeed valve's dynamics in the system model, a high-fidelity, three-dimensional, computational fluid-dynamics (CFD) model was employed. The results from the CFD model were used to specify the valve's flow characteristics in the system simulation. This yielded a crossfeed system model that was anchored to the specific valve hardware and achieved good agreement with the measured test data. These results allowed the transient models to be correlated and validated and used for full scale mission predictions. The full scale model simulations indicate crossfeed is ' viable with the system pressure disturbances at the crossfeed transition being less than experienced by the propulsion system during engine start and shutdown transients.

Mazurkivich, Pete↗
DOE OSTI2022

Thermal hydraulic analysis of the AFIP-7 irradiation test in the Advanced test Reactor – Model correlation and performance evaluation

We report as a system level code, RELAP5 is widely used in the nuclear field for the reactor hydraulic analysis. In the component/experimental level, it is frequently employed as well. This paper demonstrates that the RELAP5 flow simulation of the AFIP-7 irradiation experiment which has a complicated 3D geometry/flow path deviates by ~28% from the flow evaluation through a computational fluid dynamics (CFD) simulation, which has been validated against a flow test performed at Oregon State University. Thermal safety compliance analysis of an experiment planned to be irradiated in the Advanced Test Reactor is usually performed using the finite element analysis code, Abaqus. This research reveals the disadvantages of the Abaqus simulation in the flow instability and departure from nucleate boiling evaluations via a conjugate heat transfer analysis of the AFIP-7 irradiation experiment. As a result, a detailed CFD simulation is suggested for irradiation experiments with complicated flow paths, rather than a simplified RELAP5 simulation or hand calculations. The validated simulation approach will be integrated with the Boehmite correlations to investigate the oxide growth prediction on the fuel cladding in Part II of this research.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1986

Laminar flow integration: Flight tests status and plans

Under the Aircraft Energy Efficiency - Laminar Flow Control Program, there are currently three flight test programs under way to address critical issues concerning laminar flow technology application to commercial transports. The Leading-Edge Flight Test (LEFT) with a JetStar aircraft is a cooperative effort with the Ames/Dryden Flight Research Facility to provide operational experience with candidate leading-edge systems representative of those that might be used on a future transport. In the Variable Sweep Transition Flight Experiment (VSTFE), also a cooperative effort between Langley and Ames/Dryden, basic transition data on an F-14 wing with variable sweep will be obtained to provide a data base for laminar flow wing design. Finally, under contract to the Boeing Company, the acoustic environment on the wing of a 757 aircraft will be measured and the influence of engine noise on laminar flow determined with a natural laminar flow glove on the wing. The status and plans for these programs are reported.

Wagner, R. D.↗
DOE OSTI2019

Akutan Geothermal: Resource Report

Geothermal energy resources are present in the Hot Springs Bay Valley geothermal area, and the City has invested considerable money and time in the exploration of the resource for future use. Exploration activities funded primarily through a grant the City was awarded from Alaska Energy Authority and later supplemented by the U. S. Department of Energy (DOE), with cost share from the City. The exploration led to the development of a geothermal resource conceptual model that was built and refined between 2008 and 2018. During this period, geological and geophysical studies, exploration drilling and other activities were completed, including a preliminary feasibility study for a power project, investigations of the terrain for suitability for access and development, environmental and archeological review, plus TG well abandonment and a review of economic considerations. The model of the resource predicts that there is a viable geothermal resource in two general areas: on the northwest edge of Hot Springs Bay Valley going northwest of the valley (hot springs area) and southwest of the Valley (fumarole area). The resource temperature for the valley area is expected to be about 170°C (340°F) and given the size and permeability estimates (with a factor for the level of confidence in the estimates), the mean power capacity of the outflow resource is 3 MWe and the P50 (most likely) power capacity is 1 MWe. The fumarole area has an expected resource temperature of 240°C (464°F) and given the size and permeability estimates mean capacity is 20 MWe and the P50 (most likely) capacity is 9 MWe. Permeability is the most difficult factor to predict and has a significant impact on the available geothermal fluids and therefore the amount of power that can be generated. The uncertainty in this value is the main reason for lower confidence in the likelihood of exploration success and the wide range in predicted MW values. The permeability has been difficult to locate as indicated by the results of the flow test at AK-3 in 2017. The test resulted in the production of some fluid, but due to low permeability, the recharge to the wellbore was too slow to sustain flow. The greatest probability of overall MWe production is in the fumarole region, but development is hampered by poor accessibility. The extremely high cost of road building for exploratory drilling, put an end to planning at an intermediate stage of the project and refocused attention on the viability of development in the hot spring outflow part of the resource. The City will be determining what the next steps are with AK-3, which is still that is still open and maintained in a suspended status in HSBV. While AK-3 remains accessible (not plugged with cement) it will need to be maintained. The City has a bond with AOGCC that will remain in place until the well is abandoned. GRG recommends that the well be maintained open as an asset for the foreseeable future.

15 GEOTHERMAL ENERGY↗
NASA NTRS1982

Experiment measurement of Alford's force in axial-flow turbomachinery

Results of experimental measurements made on a small high speed, axial flow test apparatus are presented to verify the existence of Alford's force (that circumferential variation of blade-tip clearances in axial-flow turbomachinery will produce cross-coupled (normal to the eccentricity) aerodynamic forces on the rotor) and to investigate the validity of his mathematical prediction model.

Vance, J. M.↗
NASA NTRS1983

Design, fabrication and testing of porous tungsten vaporizers for mercury ion thrusters

The dispersions in the characteristics, performance and reliability of vaporizers for early model 30-cm thrusters were investigated. The purpose of the paper is to explore the findings and to discuss the approaches that were taken to reduce the observed dispersion and present the results of a program which validated those approaches. The information that is presented includes porous tungsten materials specifications, a discussion of assembly procedures, and a description of a test program which screens both material and fabrication processes. There are five appendices providing additional detail in the areas of vaporizer contamination, nitrogen flow testing, bubble testing, porosimeter testing, and mercury purity. Four neutralizers, seven cathodes and five main vaporizers were successfully fabricated, tested, and operated on thrusters. Performance data from those devices is presented and indicates extremely repeatable results from using the design and fabrication procedures.

Zavesky, R.↗
NASA NTRS1991

Experimental study of a vortex-shedding flowmeter

A prototype of a vortex-shedding flowmeter with no moving parts is investigated for the loading of hypergolic fuels into the Space Shuttle Orbiter. Eliminating moving parts is intended to reduce the need for servicing the meter, and the vortex shedder is compared to the turbine flowmeter presently in use. A flow test loop is designed and employed to conduct experimental investigations in which the output characteristics are examined. The relationship between vortex frequency and flow rate is almost linear, as is the relationship between vortex shedding frequency and the Reynolds and Strouhal numbers. The results are consistent with calculations and suggest that the flowmeter is a possible replacement for measuring the loading of hypergols into the Space Shuttle Orbiter.

Thinh, Ngo D.↗
NASA NTRS1998

Analysis of Linear Aerospike Plume Induced X-33 Base Heating Environment

Computational analysis is conducted to study the effect of an linear aerospike engine plume on the X-33 base-heating environment during ascent flight. To properly account for the freestream-body interaction and to allow for potential plume-induced flow-separation, the thermo-flowfield of the entire vehicle at several trajectory points is computed. A sequential grid-refinement technique is used in conjunction with solution-adaptive, patched, and embedded grid methods to limit the model to a manageable size. The computational methodology is based on a three-dimensional, finite-difference, viscous flow, chemically reacting, pressure-based computational fluid dynamics formulation, and a three-dimensional, finite-volume, spectral-line based weighted-sum-of-gray-gases absorption, computational radiation heat transfer formulation. The computed forebody and afterbody surface pressure coefficients and base pressure characteristic curves are compared with those of a cold-flow test. The predicted convective and radiative base-heat fluxes, the effect of base-bleed, and the potential of plume-induced flow separation are presented.

Wang, Ten-See↗
NASA NTRS2012

Characterization of Deficiencies in the Frequency Domain Forced Response Analysis Technique for Turbine Bladed Disks

Turbine blades in rocket and jet engine turbomachinery experience enormous harmonic loading conditions. These loads result from the integer number of upstream and downstream stator vanes as well as the other turbine stages. The standard technique for forced response analysis to assess structural integrity is to decompose a CFD generated flow field into its harmonic components, and to then perform a frequency response analysis at the problematic natural frequencies. Recent CFD analysis and water-flow testing at NASA/MSFC, though, indicates that this technique may miss substantial harmonic and non-harmonic excitation sources that become present in complex flows. These complications suggest the question of whether frequency domain analysis is capable of capturing the excitation content sufficiently. Two studies comparing frequency response analysis with transient response analysis, therefore, have been performed. The first is of a bladed disk with each blade modeled by simple beam elements. It was hypothesized that the randomness and other variation from the standard harmonic excitation would reduce the blade structural response, but the results showed little reduction. The second study was of a realistic model of a bladed-disk excited by the same CFD used in the J2X engine program. The results showed that the transient analysis results were up to 10% higher for "clean" nodal diameter excitations and six times larger for "messy" excitations, where substantial Fourier content around the main harmonic exists.

Brown, Andrew M.↗
NASA NTRS2005

Cold Flow Plume Entrainment Test Final Report NTF Test Number 2456

As part of the Space Shuttle Return to Flight (RTF) program, Marshall Space Flight Center (MSFC) performed computational fluid dynamics (CFD) analysis to define the velocity flowfields around the Shuttle stack at liftoff. These CFD predicted velocity flowfields were used in debris transport analysis (DTA). High speed flows such as plumes induce or 'entrain' mass from the surrounding environment. Previous work had shown that CFD analysis over-predicts plume induced flows. Therefore, the DTA would tend to 1) predict more debris impacts, and 2) the debris velocity (and kinetic energy) of those impacts would be too high. At a November, 2004 peer-review it was recommended that the Liftoff DTA team quantify the uncertainty in the DTA caused by the CFD's over prediction of plume induced flow. To do so, the Liftoff DTA team needed benchmark quality data for plume induced flow to quantify the CFD accuracy and its effect on the DTA. MSFC's Nozzle Test Facility (NTF) conducted the "Nozzle Induced Flows test, P#2456" to obtain experimental data for plume induced flows for nozzle flow exhausting into q quiescent freestream. Planning for the test began in December, 2004 and the experimental data was obtained in February and March of 2005. The funding for this test was provided by MSFC's Space Shuttle Propulsion Systems Integration and Engineering office.

Ruf, Joseph H.↗
DOE OSTI2012

Benchmark specifications for EBR-II shutdown heat removal tests

Argonne National Laboratory (ANL) is hosting an IAEA-coordinated research project on benchmark analyses of sodium-cooled fast reactor passive safety tests performed at the Experimental Breeder Reactor-II (EBR-II). The benchmark project involves analysis of a protected and an unprotected loss of flow tests conducted during an extensive testing program within the framework of the U.S. Integral Fast Reactor program to demonstrate the inherently safety features of EBR-II as a pool-type, sodium-cooled fast reactor prototype. The project is intended to improve the participants' design and safety analysis capabilities for sodium-cooled fast reactors through validation and qualification of safety analysis codes and methods. This paper provides a description of the EBR-II tests included in the program, and outlines the benchmark specifications being prepared to support the IAEA-coordinated research project. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1990

A laser-sheet flow visualization technique for the large wind tunnels of the National Full-Scale Aerodynamics Complex

A flow visualization technique for the large wind tunnels of the National Full Scale Aerodynamics Complex (NFAC) is described. The technique uses a laser sheet generated by the NFAC Long Range Laser Velocimeter (LRLV) to illuminate a smoke-like tracer in the flow. The LRLV optical system is modified slightly, and a scanned mirror is added to generate the sheet. These modifications are described, in addition to the results of an initial performance test conducted in the 80- by 120-Foot Wind Tunnel. During this test, flow visualization was performed in the wake region behind a truck as part of a vehicle drag reduction study. The problems encountered during the test are discussed, in addition to the recommended improvements needed to enhance the performance of the technique for future applications.

Reinath, M. S.↗