Taitech (United States)

View Video Presentation: https://doi.org/10.2514/6.2021-0849.vid Structures and expansion processes of two-phase flows within the aluminum nozzle of an aerated-liquid injector were explored using the x-ray fluorescence technique at the Advanced Photon Source at Argonne National Laboratory. The aluminum nozzle has a convergent-divergent (CD) contour and is capable of modulating the expansion processes of a compressible two-phase flow. Water and nitrogen were doped with potassium iodine and xenon, respectively, at low concentrations, in order to facilitate pathlength-integrated x-ray fluorescence measurements for simultaneous time-averaged characterization of liquid and gas mass distribution. Averaged flow properties, including liquid volume frac-tion, density and velocity of each phase, local pressure, mixture speed of sound, and mixture momentum flux, were also derived from the present measurements, in order to characterize both the expansion processes of and the flow structures in the two-phase mixtures. The present results were combined with previous measurements made using beryllium nozzles with variations in nozzle contour (CD vs. plain orifice (PO)) and passage length, in order to explore the effects of nozzle design on two-phase structures inside metal nozzles. It was found that the expansion processes mainly take place within the divergent section of the CD nozzle, with significant reductions in liquid volume fraction and both liquid and gas densities. Continuous increases in liquid and gas velocities could not be achieved, probably due to an excessive increase in the cross-sectional area of the CD contour design. Local pressure could be significantly reduced at the CD nozzle exit for a small pressure drop across the nozzle and limited lateral dispersion of the dis-charged plume. An increase in liquid aeration level leads to increases in gas density, local pressure, and momentum flux, and decreases in liquid volume fraction and liquid density for the present CD contour. The expansion processes of the two-phase mixture are highly sensitive to the contour passage design and are less sensitive to the passage length. Comparisons between the CD and PO nozzles show that the CD contour is capable of enhancing the expansion pro-cesses, resulting in lowered liquid volume fraction, liquid and gas densities, and local pressure at the nozzle exit.

Aerated-liquid atomization involves the injection of a small amount of gas into a liquid stream to initiate primary breakup within the injector itself. The sprays that result have good penetration and lateral dispersion characteristics, and are suitable for fueling high-speed air-breathing propulsion systems. In this study, the flow within aerated-liquid injectors featuring both inside-out and outside-in aeration schemes is simulated using an implicit large-eddy simulation method equipped with a sharp phase-interface-capturing technique and a continuum model for surface tension. Results are compared with time-averaged and time-resolved X-ray measurements of liquid-phase density and imaging obtained at the 7-BM beamline at Argonne National Laboratory using beryllium injector models. A good agreement between computational predictions and experimental measurements is generally achieved, with each indicating that the end state of the aeration process for both injector designs is the formation of a core-annular two-phase flow in the nozzle portion of the injectors. The numerical model is less successful in predicting the structure of the separated two-phase flows observed before the expansion of the mixture through the nozzle. One-dimensionalized liquid-phase density, velocity, and momentum flux distributions obtained from the numerical model and the experiment display a close agreement for all injector configurations.

Gas and liquid mass distributions within the near field of aerated-liquid jets were characterized using the X-ray fluorescence technique. The X-ray source available at the 7-BM beamline at the Argonne National Laboratory was used for the present study. Krypton and bromine were added into nitrogen and water, respectively, at low concentrations for fluorescence generation along a well-focused X-ray beam positioned inside the aerated-liquid jet. The obtained line-of-sight fluorescence signals were further processed to account for photon trapping to give quantitative liquid and gas mass distributions at various injection conditions. An axisymmetric aerated-liquid injector fitted with an exchangeable adaptor was used to generate an aerated-liquid jet at the desired liquid flow rate and aeration level. Several adaptors with various internal contours and lengths were used to further modulate the aerated-liquid jet. It was found that the gas plume is separated from the liquid plume within the aerated-liquid jet, regardless of the adaptor configuration. The width of the gas plume is narrower than that of the liquid plume, especially at the downstream locations for well-dispersed sprays. The potential mechanisms for the separation of liquid and gas plumes are proposed and discussed. It was also found that the liquid mass distribution within the aerated-liquid jet transitions from a coannular-like structure to a uniform structure as both liquid flow rate and aeration level increase. For the adaptor with a constant diameter for the final passage, a variation in adaptor length from L/D=2.5 to 10 creates similar spray structures. For the adaptor with a convergent-divergent contour, the expansion rate of the liquid plume is closely defined by the exit slope of the internal contour. No additional lateral expansion of the liquid plume was observed. NOMENCLATURE

This investigation concerns the design, build, and testing of a new class of skin friction sensors capable of performing favorably in high-speed, high-enthalpy flow conditions, such as those experienced by atmospheric re-entry vehicles, scramjets, jet engines, material testing, and industrial processes. Fully understanding and optimizing these complex flows requires knowledge of the relevant aerodynamic properties, which, in turn, requires numerical and analytical modeling as well as reliable diagnostic instrumentation. A rigorous, multistep approach was developed to systematically test the present skin friction sensors through various facilities, where flow enthalpy and run duration were progressively increased, culminating in simulated scramjet flight conditions at the Air Force Research Laboratory (AFRL). At AFRL, nominal Mach 2.0 to 2.2 flows were studied at stagnation pressures and temperatures ranging from 172 to 995 kPa (25 to 144 psia) and 294 to 1000 K (530 to 1800 °R), respectively. The skin friction sensors made static wall shear stress measurements between 94 and 600 Pa (1.96 and 12.5 psf) and skin friction coefficient measurements between 0.00158 and 0.00280. In addition, the sensors were able to clearly indicate the transient flow conditions of a full scramjet combustion operability cycle to include shock train movement, separation zones, and reverse flow along the isolator wall. The sensor demonstrated full functionality under sustained high-enthalpy flow conditions upward of 1053 kJ/kg (453 Btu/lbm). Issues with pressure disturbance impingement on the sensor were identified and discussed. The total uncertainty of the present skin friction sensor was determined to be ±8.7% at 95% confidence. The experimental wall shear data demonstrated good agreement with simple, flat-plate analytical estimations. Numerical estimations of the scramjet flow path resulted in favorable results for steady coldand hot-flow conditions, but had to be refined to handle the various fueling injection schemes with burning in the downstream combustor and surface roughness models.

The analysis presented in Part I of this study is extended to investigate ignition transients and flame development in an ethylene-fueled scramjet engine. Unheated gaseous ethylene is transversely injected into the combustor upstream of a recessed cavity flameholder. Immediately after the ethylene–air mixture reaches its steady state in the combustor, a hotspot igniter is activated in the cavity to initiate chemical reactions. Cases both with and without air throttling downstream of the cavity during the engine startup stage are examined in detail. Successful ignition can only be achieved with the aid of air throttling under the present flow conditions. As a consequence of the backpressurization by the throttling air, a shock train is generated in the isolator, which then decelerates the high-speed main stream, enhances the fuel mixing efficiency, and increases the temperature and pressure in the combustor. Chemical reactions are intensified and produce sufficient heat release to maintain a flow environment conducive to flame stabilization. A self-sustaining mechanism is thus established between the flow and flame development. Stable flames are achieved even after the deactivation of air throttling. The predicted pressure distribution along the entire flowpath agrees well with experimental measurements.

Direct-connect wind-tunnel facilities that produce uniform flow entering the test section are generally used for scramjet-component (isolator/combustor) studies. In freejet experiments and flight tests, however, air enters the engine through an inlet, and flow entering the isolator and combustor is typically distorted. The distortion effects can include nonuniform boundary-layer thicknesses on the walls and relatively strong oblique shock waves. This research focuses on the effects of inlet distortion on a round scramjet isolator. A numerical study was performed using various distortion devices, including ramps, injector ports, and injector slots, that were placed downstream of the direct-connect facility nozzle to simulate a distorted flowfield from a prescribed inlet. The computational results provided a methodology for simulating flow distortion in direct-connect testing. Based on the numerical findings, experimental testing was conducted in the supersonic wind-tunnel facility to validate the numerical results and determine the impact of flow distortion. In addition, this paper focuses on design, fabrication, and execution of flow-distortion experiments. Air injection in the distortion section was used to create the flow distortion, and shock angle increases with the injection flow. Comparisons of wall pressure, exit flow profiles, and shock-holding capability are made from the experimental and numerical results. Good agreement between these data on wall pressures and flow profiles was found.

This paper presents an initial conceptual design of a wearable manipulator for supporting astronaut extravehicular activity (EVA). The proposed robot system acts as a third hand or eye of astronauts, and supports them by handling tools or recording their tasks using camera during EVA with the manipulator itself attached to the space suit or handrail. The initial conceptual design includes the system concept, requirements, elemental technologies and operational scenarios which are defined on the basis of the interviews to astronauts and operators. The prototype of the manipulator, especially robotic hand or end effector is also discussed in this paper for estimating the feasibility of the proposed robot system in the future manned space activities.

Direct-connect wind-tunnel facilities that produce uniform flow entering the test section are generally used for scramjet-component (isolator/combustor) studies. In freejet experiments and flight tests, however, air enters the engine through an inlet, and flow entering the isolator and combustor is typically distorted. The distortion effects can include nonuniform boundary-layer thicknesses on the walls and relatively strong oblique shock waves. This research focuses on the effects of inlet distortion on a round scramjet isolator. A numerical study was performed using various distortion devices, including ramps, injector ports, and injector slots, that were placed downstream of the direct-connect facility nozzle to simulate a distorted flowfield from a prescribed inlet. The computational results provided a methodology for simulating flow distortion in direct-connect testing. Based on the numerical findings, experimental testing was conducted in the supersonic wind-tunnel facility to validate the numerical...

Imaginary-time Nambu-Bethe-Salpeter (NBS) wave function is introduced to extend our previous approach for hadron-hadron interactions on the lattice. Scattering states of hadrons with different energies encoded in the NBS wave-function are utilized to extract non-local hadron-hadron potential. "The ground state saturation", which is commonly used in lattice QCD but is hard to be achieved for multi-baryons, is not required. We demonstrate that the present method works efficiently for the nucleon-nucleon interaction (the potential and the phase shift) in the 1S_0 channel.