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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 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Laser velocimeter measurements of the flow field generated by a forward-swept propfan during flutter

Results are presented from an investigation to measure the flow field generated by a forward-swept propfan operating in flutter at a low forward velocity. For comparison to the flutter condition, flow field data are also presented for a slightly reduced rotational speed just below flutter. The forward-swept propfan was tested as the front rotor of a counterrotating pusher propeller. A laser Doppler velocimeter (LDV) was used to measure the velocity field in planes normal to the model centerline downstream of the rotor and in planes of constant radius within the blade passages at each operating condition. A comparison of the data taken at the two different operating conditions indicated that the mean, time-averaged flow about the blades did not change drastically as the propfan rotational speed was increased from the stable operating point to the flutter condition. No regions of flow separation could be identified in the data plots of the mean intrablade flow field. The data also indicate that the relative flow about the blades remained subsonic during flutter operation. The blades were found to have a higher than expected tip loading at both operating conditions. This is thought to have been caused by the outer blade sections twisting under load to higher than expected effective blade angles. This high tip loading resulted in strong vortices and a very nonuniform flow downstream of the tips of the forward-swept blades. This high tip loading may also have caused the blade flutter.

Podboy, Gary G.↗
DOE OSTI2021

Beam Profile Measurements Utilizing an Amplitude Modulated Pulsed Fiber Laser at PIP2IT

Fermilab is undertaking the development of a new 800 MeV superconducting RF linac to replace its present normal conducting 400 MeV linac. The PIP-II linac consists of a warm front-end generating 2 mA of 2.1 MeV H⁻ followed immediately by a series of superconducting RF cryomodules to 800 MeV. To limit the potential damage to the superconducting RF cavities, PIP-II will utilize laser-based monitors to obtain beam profiles via photoionization. This paper will present the results of transverse and longitudinal beam profile measurements using a prototype profile monitor that was tested with 2.1 MeV H⁻ beam at the PIP-II Injector Test (PIP2IT) accelerator. This prototype profile monitor utilizes a high repetition rate fiber laser and fiber optic transport into the PIP2IT enclosure. In addition, results will be shown of narrow-band electron detection from amplitude modulated laser pulses.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Method for Rapid Modeling of Distortion in Laser Powder Bed Fusion Metal Additive Manufacturing Parts

The simulation and modeling of part-level distortion and residual stress in diverse metal additive manufacturing (AM) geometries has great potential to enable the rapid adoption of this technology in engineering design. Moreover, the use of additive manufacturing component libraries (CLs) offer a computationally efficient means of quantifying these part-level defects resultant from AM processing. We report on how the individual simulations of simple shapes, potential entries in a CL, can be superimposed to provide an indication of distortion and residual stresses in complex geometries. Laser powder bed fusion AM was used to construct test geometries of varied shapes and their combinations in the form of CLs in an effort to characterize location-dependent and feature-dependent distortion distributions. Blue light scanning was used to experimentally measure 3D distortions in order to investigate the interaction between the component shapes and local boundary conditions. Overall, part-level distortions were highly dependent on test component geometry, local boundary conditions, and shape combination. Commercial finite element software was used to verify experimental trends and to make predictions of distortion. The use of CLs resulted in over 20 times savings in computational cost while reproducing overall trends in distortion for test geometry assemblies. Therefore, it is anticipated that the use of CLs for L-PBF AM geometries has demonstrated potential to facilitate efficient simulations of full component AM assemblies, thereby reducing the need for costly trial-and-error-type experimental analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A shock tube study of ignition delay times in diluted methane, ethylene, propene and their blends at elevated pressures

Ignition delay times (IDT) of small hydrocarbons at elevated pressures provide a valuable constraint for the refinement of the core small-hydrocarbon sub-mechanisms used in all combustion kinetics. Current knowledge of these core mechanisms is based largely on low-pressure data, with only limited high-pressure data available. To remedy this, here the present study focuses on ignition delay times in methane, ethylene, propene and their blends at elevated pressures. IDT measurements were performed in 4% O 2 , balance Ar mixtures, over the temperature range of 950–1800 K, at pressures of 14–60 atm and equivalence ratios of 1 and 2. IDT was determined from recorded sidewall pressure, OH* emission measurements and fuel time-histories measured using laser absorption at 3.39 μm. These measurements extend the test conditions of earlier studies, with the advantage that they have all been performed at similar conditions and with the same facility and should provide a uniform set of kinetics targets for the evaluation of core small-hydrocarbon mechanisms. This dataset also allowed the temperature variation of the pressure and equivalence ratio scaling for methane and ethylene IDT to be investigated.

42 ENGINEERING↗
DOE OSTI2024

Hexamethyldisiloxane pyrolysis: probing H-atom initiation by femtosecond two-photon LIF

Previous experiments have led to the hypothesis that pyrolysis of silica nanoparticle precursors carried in an inert central gas jet surrounded by a laminar flame is initiated not by thermal decomposition (the measured jet temperatures are too low for pyrolysis), but by reactions with H-atoms diffusing from the surrounding flame into the jet. The current work tests this hypothesis using femtosecond two-photon laser-induced fluorescence (fs-TPLIF) to image H-atom concentrations in the same flame configuration as the previous experiments. Methane flames (ϕ = 0.83, 1.01 and 1.13) were generated using a multi-element diffusion (Hencken) burner equipped with a central tube through which the N2 jet was introduced. The fs-TPLIF line imaging showed significant concentrations of H-atoms in the nitrogen jets at heights above the burner (HAB) close to the methane flame front. The measurements indicate radial diffusion of the H atoms from the flame to the jet is significant. The H-atom concentrations in the jet increased with increasing stoichiometry of the methane flame. Additional experiments were performed with hexamethyldisiloxane entrained in the central jet flow. In each case, a diffusion flame producing silica nanoparticles was established at the boundaries between the central jet and the methane flames. The 2D H-atom images showed a transition from over-ventilated diffusion flames to under-ventilated diffusion flames with increasing equivalence ratio. Furthermore, the fs-TPLIF profiles show a significant production of H-atoms within the jet when the surrounding flame is lean. This knowledge contributes to a deeper understanding of the underlying mechanisms governing these synthesis flame systems and opens avenues for advancing silica nanoparticle synthesis techniques.

Kim, Keunsoo↗
DOE OSTI2016

Thermoacoustic and thermoreflectance imaging of biased integrated circuits: Voltage and temperature maps

In this work a combined thermoacoustic and thermoreflectance set-up was designed for imaging biased microelectronic circuits. In particular, it was used with polycrystalline silicon resistive tracks grown on a monocrystalline Si substrate mounted on a test chip. Thermoreflectance images, obtained by scanning a probe laser beam on the sample surface, clearly show the regions periodically heated by Joule effect, which are associated to the electric current distribution in the circuit. The thermoacoustic signal, detected by a pyroelectric/piezoelectric sensor beneath the chip, also discloses the Joule contribution of the whole sample. However, additional information emerges when a non-modulated laser beam is focused on the sample surface in a raster scan mode allowing imaging of the sample. The distribution of this supplementary signal is related to the voltage distribution along the circuit.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Laser-driven magnetized liner inertial fusion on OMEGA

Magneto-inertial fusion (MIF) combines the compression of fusion fuel, a hallmark of inertial confinement fusion (ICF), with strongly magnetized plasmas that suppress electron heat losses, a hallmark of magnetic fusion. It can reduce the traditional velocity, pressure, and convergence ratio requirements of ICF. The magnetized liner inertial fusion (MagLIF) concept being studied at the Z Pulsed-Power Facility is a key target concept in the U.S. ICF Program. Laser-driven MagLIF is being developed on OMEGA to test the scaling of MagLIF over a range of absorbed energy of the order of 1 kJ on OMEGA to 500 kJ on Z. It is also valuable as a platform for studying the key physics of MIF. An energy-scaled point design has been developed for OMEGA that is roughly 10 × smaller in linear dimensions than Z MagLIF targets. A 0.6-mm-outer-diameter plastic cylinder filled with 2.4 mg/cm3 of D2 is placed in a ∼10-T axial magnetic field, generated by a Magneto-inertial fusion electrical discharge system, the cylinder is compressed by 40 OMEGA beams, and the gas fill is preheated by a single OMEGA beam propagating along the axis. Preheating to >100 eV and axially uniform compression over 0.7 mm have been demonstrated, separately, in a series of preparatory experiments that meet our initial expectations. The preliminary results from the first integrated experiments combining magnetization, compression, and preheat demonstrating a roughly 2 x increase in the neutron yield will be reported here for the first time.

Barnak, D. H. (ORCID:0000000246467517)↗
DOE OSTI2019

Flat-field VLS spectrometer for a wavelength range of 50 – 275 Å

A flat-field VLS spectrograph for a wavelength range ∼50 – 275 Å with an average linear dispersion of 0.18 mm Å{sup −1}, which makes use of a grazing-incidence varied line-space (VLS) grating, was calculated and implemented (a spectrograph of Harada class). To fabricate the VLS grating by interference lithography technique, an algorithm was developed for calculating the writing configuration with an auxiliary aberrating mirror (the solution of the inverse problem of interference lithography). The spectrograph was put to a test and line spectra were recorded from the laser-produced plasma of lithium fluoride and teflon targets, which were excited by a focused laser beam (0.5 J, 8 ns, 1.06 μm). A resolving power λ/d l = 800 was demonstrated in a wavelength region of 135 Å. (x-ray spectrometry)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Quantum theory for 1D X-ray free electron laser

Classical 1D X-ray Free Electron Laser (X-ray FEL) theory has stood the test of time by guiding FEL design and development prior to any full-scale analysis. Future X-ray FELs and inverse-Compton sources, where photon recoil approaches an electron energy spread value, push the classical theory to its limits of applicability. After substantial efforts by the community to find what those limits are, there is no universally agreed upon quantum approach to design and development of future X-ray sources. We offer a new approach to formulate the quantum theory for 1D X-ray FELs that has an obvious connection to the classical theory, which allows for immediate transfer of knowledge between the two regimes. In conclusion, we exploit this connection in order to draw quantum mechanical conclusions about the quantum nature of electrons and generated radiation in terms of FEL variables.

42 ENGINEERING↗
DOE OSTI2018

A terahertz pump mega-electron-volt ultrafast electron diffraction probe apparatus at the SLAC Accelerator Structure Test Area facility

Here, we describe a new experimental setup capable of measuring structural dynamics following intense terahertz excitation. This system, developed at the SLAC Accelerator Structure Test Area facility, uses a high-energy ultrafast laser to produce intense terahertz pulses and femtosecond electron bunches that are accelerated to mega-electron-volt kinetic energies. The focused terahertz pulses have electric fields in excess of 600 kV/cm, and the resulting structural dynamics can be followed by electron diffraction. We also present some examples demonstrating its implementation where interactions between the THz pulses and the electron bunch are used to characterize the spatial and temporal characteristics of the THz field.

42 ENGINEERING↗
DOE OSTI2024

Gain Stability of Hamamatsu R5912-MOD Photo-Multipliers at Low Temperature

The Photon Detection System is a crucial component of the ICARUS detector in the Short Baseline Neutrino (SBN) Program at Fermi National Accelerator Laboratory (FNAL). It consists of 360 Photo Multiplier Tubes (PMTs) 8” Hamamatsu R5912-MOD and, since June 2020, it has been operated at the liquid Argon cryogenic temperature. During these years, the PMTs have shown gain losses as an aging effect. Using a climatic chamber at the INFN Sezione di Catania, we confirmed a stable gain for a single PMT 8” Hamamatsu 5912-MOD when operated at room temperature, and a persistent gain loss at temperatures around -70°C, although far from the liquid Argon one. No gain recovery was obtained bringing the PMT back to room temperature. We suspect that dynode deterioration due to temperature gradient plays a significant role in this phenomenon. During our test, the PMT was illuminated by a 520 nm laser source and operated in current mode. The laser beam was split into two optical fibers, the first one transmitting light through Neutral Density filters and then diffusing it over the surface of the PMT photocathode. The other optical fiber was used for an independent reference measurement of the injected light via a bolometric photodetector. In this presentation, the main technical characteristics of the measurement system are shown together with preliminary results which need further investigation to elucidate the underlying mechanisms driving the gain loss and to propose new mitigation strategies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Multichannel Fiber-Optic Silicon Fabry–Pérot Interferometric Bolometer System for Plasma Radiation Measurements

A single-channel fiber-optic bolometer system based on a high-finesse silicon Fabry–Pérot interferometer (FPI) was previously reported, intended to measure plasma radiation from the magnetically confined fusion chamber. Recently, we developed a multichannel fiber-optic bolometer system with five bolometers multiplexed using a coarse wavelength division multiplexer (CWDM) and interrogated with a white-light system involving a superluminescent light-emission diode source and a high-speed spectrometer. One of the bolometers was used as the reference bolometer to compensate for the ambient temperature variations, and the other four bolometers were used for radiation measurement. The bolometers have a simple structure with a silicon pillar at the end of the single-mode fiber and a gold disk on the other side of the silicon pillar. They are also easy to fabricate without stringent requirements on the optical alignment. Analysis of the system optimization was performed to improve the noise performance and to mitigate the vibration effect that may present in the practical application. The system had a significantly enhanced measurement range compared to the previous high-finesse FPI bolometer system for measuring radiation. Test results performed in air using a 405 nm laser as the radiation source showed that the temperature resolution and the noise-equivalent power density of the sensing bolometers connected to each channel of the CWDM were, respectively, ~0.4 mK and ~0.1 W/m2, with a time constant of ~220 ms, which is comparable to the previous more complicated fiber-optic bolometer systems based on high-finesse FPIs that were interrogated using wavelength-scanning lasers.

Uddin, Nezam↗
NASA NTRS1973

True airspeed measured by airborne laser Doppler velocimeter

Velocimeter utilizing carbon dioxide laser measures true airspeed of aircraft. Results of flight tests indicate that clear-weather airspeeds can be measured with accuracy better than 0.1% at altitudes up to 3000 meters; measurements can be made at much greater altitudes in cloudy or turbid air.

Munoz, R.↗
NASA NTRS1973

A comparison of a coaxial focused laser Doppler system in atmospheric measurements

Measurements of atmospheric velocities and turbulence with the laser Doppler system were obtained, and the results compared with cup anemometer and hot-wire measurements in the same wind field. The laser Doppler velocimeter (LDV) is described along with the test procedures. It was found that mean values determined from the LDV data are within 5% of other anemometer data for long time periods, and the LDV measures higher velocities.

Karaki, S.↗
NASA NTRS1975

Interaction of graphite and ablative materials with CO2-laser, carbon-arc, and xenon-arc radiation

The behavior of graphite and several charring ablators in a variety of high radiative heat flux environments was studied in various radiative environments produced by a CO2 laser and a carbon arc facility. Graphite was also tested in xenon arc radiation. Tests were conducted in air nitrogen, helium, and a mixture of CO2 and nitrogen, simulating the Venus atmosphere. The experimental results are compared with theoretical results obtained with a one dimensional charring ablator analysis and a two dimensional subliming ablator analysis. Photomicroscopy showed no significant differences in appearance or microstructure of the charring ablators or graphite after testing in the three different facilities, indicating that the materials respond fundamentally the same to the radiation of different frequencies. The performance of phenolic nylon and graphite was satisfactorily predicted with existing analyses and published material property data.

Brewer, W. D.↗
NASA NTRS1975

Investigation of rotor blade element airloads for a teetering rotor in the blade stall regime (second wind tunnel test)

A test was conducted in the NASA-Ames 7 x 10 ft low speed wind tunnel on a seven-foot diameter model of a teetering rotor. The objectives of the test were: (1) acquire pressure data for correlation with laser and flow visualization measurements; (2) explore rotor propulsive force limits by varying the advance ratio at constant lift and propulsive force coefficients; (3) obtain additional data to define the differences between teetering and articulated rotors; and (4) verify the acceleration sensitivity of experimental transducers. Results are presented.

Dadone, L. U.↗
NASA NTRS1980

Solar Power Satellite (SPS) fiber optic link assessment

A feasibility demonstration of a 980 MHz fiber optic link for the Solar Power Satellite (SPS) phase reference distribution system was accomplished. A dual fiber-optic link suitable for a phase distribution frequency of 980 MHz was built and tested. The major link components include single mode injection laser diodes, avalanche photodiodes, and multimode high bandwidth fibers. Signal throughput was demonstrated to be stable and of high quality in all cases. For a typical SPS link length of 200 meters, the transmitted phase at 980 MHz varies approximately 2.5 degrees for every deg C of fiber temperature change. This rate is acceptable because of the link length compensation feature of the phase control design.

Source record↗
NASA NTRS1982

Dynamic Isolation for Cryogenic Refrigerators

Prototype pressure-compensated mounting isolates a Tunable Diode Laser (TDL) housing from mechanical vibration. Mounting is being tested as part of Langley Research Center program for development of highly sensitive instruments that remotely measure important chemical constituents of atmosphere. Instruments typically have requirement for cryogenic cooling of sensitive detectors and components that are necessary to detect presence of tenuous constituents of atmosphere. Key elements of mounting are two bellows, reaction plate, flexible straps and vibration isolators.

Averill, R. D.↗