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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 73 records · Page 4

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NASA NTRS2011

Jet engine nozzle exit configurations and associated systems and methods

Nozzle exit configurations and associated systems and methods are disclosed. An aircraft system in accordance with one embodiment includes a jet engine exhaust nozzle having an internal flow surface and an exit aperture, with the exit aperture having a perimeter that includes multiple projections extending in an aft direction. Aft portions of individual neighboring projections are spaced apart from each other by a gap, and a geometric feature of the multiple can change in a monotonic manner along at least a portion of the perimeter.

Mengle, Vinod G.↗

NASA NTRS2012

Jet engine nozzle exit configurations, including projections oriented relative to pylons, and associated systems and methods

Mengle, Vinod G.↗

NASA NTRS2012

Jet Exit Rig Six Component Force Balance

A new six axis air balance was delivered to the NASA Glenn Research Center. This air balance has an axial force capability of 800 pounds, primary airflow of 10 pounds per second, and a secondary airflow of 3 pounds per second. Its primary use was for the NASA Glenn Jet Exit Rig, a wind tunnel model used to test both low-speed, and high-speed nozzle concepts in a wind tunnel. This report outlines the installation of the balance in the Jet Exit Rig, and the results from an ASME calibration nozzle with an exit area of 8 square-inches. The results demonstrated the stability of the force balance for axial measurements and the repeatability of measurements better than 0.20 percent.

Castner, Raymond↗

NASA NTRS2013

Jet Engine Nozzle Exit Configurations and Associated Systems and Methods

Mengle, Vinod G.↗

NASA NTRS2021

DGEN Aeropropulsion Research Turbofan Core/Combustor-Noise Measurements-Experiment and Modal Structure at Core-Nozzle Exit

Data from a recent core/combustor-noise source-diagnostic test utilizing a small turbo-fan engine are analyzed. The campaign continued the exploration begun in a baseline test, but with more extensive acoustic instrumentation. Both tests were aimed at developing a better understanding of propulsion-noise sources and their impact on the farfield noise signature, in order to enable improved turbofan noise-prediction methods and noise-mitigation techniques. Simultaneous high-data-rate acoustic measurements (93 channels in total) were obtained using a circumferential sensor array at the core-nozzle exit in conjunction with sideline and farfield microphone arrays for several relevant engine operational points. Measurements were repeated for different circumferential and sideline array configurations, as well as for redundancy. The unsteady pressure field at the core-nozzle exit is documented in detail. Previous work suggested that the±1azimuthal duct mode could be cut-on at this location, which would have implications for combustor-noise modeling and prediction. The modal decomposition of the combustor noise at the core-nozzle exit verifies this observation. Select farfield sound-pressure-level spectra are also presented.

Aeroacoustics↗

DOE OSTI2011

Determining when a set of compute nodes participating in a barrier operation on a parallel computer are ready to exit the barrier operation

Methods, apparatus, and products are disclosed for determining when a set of compute nodes participating in a barrier operation on a parallel computer are ready to exit the barrier operation that includes, for each compute node in the set: initializing a barrier counter with no counter underflow interrupt; configuring, upon entering the barrier operation, the barrier counter with a value in dependence upon a number of compute nodes in the set; broadcasting, by a DMA engine on the compute node to each of the other compute nodes upon entering the barrier operation, a barrier control packet; receiving, by the DMA engine from each of the other compute nodes, a barrier control packet; modifying, by the DMA engine, the value for the barrier counter in dependence upon each of the received barrier control packets; exiting the barrier operation if the value for the barrier counter matches the exit value.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2016

Gas turbine combustor exit piece with hinged connections

An exit piece (66) with an inlet throat (67) that conducts a combustion gas flow (36A) in a path (82) from a combustor (63) to an annular chamber (68) that feeds the first blade section (37) of a gas turbine (26). The exit piece further includes an outlet portion (69) that forms a circumferential segment of the annular chamber. The outlet portion interconnects with adjacent outlet portions by hinges (78A, 78B, 80A, 80B). Each hinge may have a hinge axis (82A, 82B) parallel to a centerline (21) of the turbine. Respective gas flows (36A) are configured by an assembly (60) of the exit pieces to converge on the feed chamber (68) into a uniform helical flow that drives the first blade section with minimal circumferential variations in force.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2018

Internal cooling system with converging-diverging exit slots in trailing edge cooling channel for an airfoil in a turbine engine

An airfoil (10) is disclosed for a gas turbine engine in which the airfoil (10) includes an internal cooling system (14) with one or more converging-diverging exit slots (20) configured to increase the effectiveness of the cooling system (14) at the trailing edge (34) of the airfoil (10) by increasing the contact of cooling fluids with internal surfaces (24, 30) of the pressure and suction sides (36, 38) of the airfoil (10). In at least one embodiment, the trailing edge cooling channel (18) may include one or more converging-diverging exit slots (20) to further pressurize the trailing edge cooling channel (18) and may be formed by a first and second ribs (80, 82) extending between an outer walls (13, 12) forming the pressure and suction sides (36, 38). The converging-diverging exit slot (20) may be formed from a first converging section (84) having an inlet (86) with a larger cross-sectional area than an outlet (88) and is formed from a second diverging section (90) having an inlet (92) with a smaller cross-sectional area than an outlet (94).

42 ENGINEERING↗

DOE OSTI2019

Effect of a Diffuser on Conditioning Flow Field Fluctuations at the Exit of a Rotating Detonation Combustor

Pressure gain combustion (PGC) seeks to convert fuel’s chemical energy simultaneously into thermal energy and mechanical energy, thereby reducing the entropy production in the process. Recent research has shown that the rotating detonation combustion or combustor (RDC) can provide excellent specific thrust, specific impulse, and large pressure gain through rapid energy release by continuous detonation in the circumferential direction. In this study, we present experimental results from RDC operated on methane and oxygen-enriched air to represent reactants used in gas turbines for land-based power generation. A thorough understanding of the velocity flow field exiting the combustor is important to develop future rotating detonation engine (RDE) designs, as well as to successfully implement the flow conditioning devices to power generating turbine hardware located downstream. The RDC is operated at high pressures in two ways through this study: 1) placing a back-pressure plate (BPP) downstream of the annular combustor, and 2) placing a diffuser downstream of the annular combustor. Time-resolved particle image velocimetry (TR-PIV) is applied at a frame rate of 50 kHz to quantify the RDC exit flow. A qualitative analysis is presented with vector data obtain from experimental testing. Results show that for the BPP configuration the highly periodic exit flow tilts in the azimuthal direction, indicating a significant circumferential velocity component. For the diffuser configuration the flow is dominantly axial, with an insignificant circumferential velocity component. The flow field undergoes cyclic fluctuations with the BPP, but not so with the diffuser. Results also show the challenges associated with achieving uniform seed distribution in this highly transient and rapidly changing flow field.

03 NATURAL GAS↗

DOE OSTI2018

Exit Flow Field of Methane-Fueld Rotating Detonation Engine Measured by Time Resolved Particle Image Velocimetry

Pressure gain combustion (PGC) seeks to convert fuel’s chemical energy simultaneously into thermal energy and mechanical energy, thereby reducing the entropy production in the process. Recent research has shown that the rotating detonation combustion or combustor (RDC) can provide excellent specific thrust, specific impulse, and large pressure gain through rapid energy release by continuous detonation in the circumferential direction. However, few past studies have employed fuels relevant to power generation gas turbines, since RDC research has focused mainly on aerospace applications. In this study, we present experimental results from RDC operated on methane and oxygen-enriched air to represent reactants used in gas turbines for land-based power generation. The RDC is operated at high pressures by placing a back-pressure plate downstream of the annular combustor. We apply time-resolved particle image velocimetry (PIV) technique, for the first time, to quantify the RDC exit flow at framing rate of 30 kHz. Results show that even though the exit flow is dominantly axial, a significant circumferential velocity component is also present, highlighting the need to condition the flow between RDE exit and turbine inlet. The flow field undergoes cyclic fluctuations, and the key features of the flow field repeat during each cycle. Interestingly, the circumferential velocity shows a reversal in the direction during the cyclic process. Results also show noticeable cycle-to-cycle variations, related to changes in the detonation wave speed, ultimately caused by the rapid fuel-air mixing process at the RDC inlet prior to detonation.

03 NATURAL GAS↗

DOE OSTI2021

A Feynman-Kac based numerical method for the exit time probability of a class of transport problems

The exit time probability, which gives the likelihood that an initial condition leaves a prescribed region of the phase space of a dynamical system at, or before, a given time, is arguably one of the most natural and important transport problems. In this work, we present an accurate and efficient numerical method for computing this probability for systems described by non-autonomous (time-dependent) stochastic differential equations (SDEs) or their equivalent Fokker-Planck partial differential equations. The method is based on the direct approximation of the Feynman-Kac formula that establishes a link between the adjoint Fokker-Planck equation and the forward SDE. The Feynman-Kac formula is approximated using the Gauss-Hermite quadrature rules and piecewise cubic Hermite interpolating polynomials, and a GPU accelerated matrix representation is used to compute the entire time evolution of the exit time probability using a single pass of the algorithm. The method is unconditionally stable, exhibits second order convergence in space, first order convergence in time, and it is straightforward to parallelize. Applications are presented to the advection diffusion of a passive tracer in a fluid flow exhibiting chaotic advection, and to the runaway acceleration of electrons in a plasma in the presence of an electric field, collisions, and radiation damping. Benchmarks against analytical solutions as well as comparisons with explicit and implicit finite difference standard methods for the adjoint Fokker-Planck equation are presented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS2015

Terra Constellation Exit (Part 2)

The Terra Constellation Exit power point presentation will discuss the baseline and proposed constellation exit plan and debris concerns.

Exit Plan↗

DOE OSTI2019

Highly resolved Eulerian simulations of fuel spray transients in single and multi-hole injectors: Nozzle flow and near-exit dynamics

In high pressure fuel injectors, needle opening and closing transients cause complex off-design fluid dynamics behaviors that profoundly impact the spray and mixture formation processes. These dynamics are completely different from what is known to occur in steady state conditions. In this study, diesel spray transients have been investigated in single-hole and 3-hole nozzles, encompassing internal and external nozzle flow and including needle motion, performing highly resolved (2.5 μm) computational fluid dynamics (CFD) simulations. We focused on end-of-injection (EOI) and start-of-injection (SOI) processes, in order to provide insights in to the physics. The liquid fuel, vapor and gas species are modeled with a single-fluid multiphase mixture approach, with diffuse interface, and with large eddy simulations (LES) of the turbulence. Occurrence of phase change due to cavitation is accounted for, and the spray dispersion is described with a turbulent dispersion model. Detailed needle motion data and orifice internal surface are available from xray synchrotron source measurements carried out at Argonne National Laboratory, and shared through the Engine Combustion Network (ECN) community. Simulations are compared against x-ray phase contrast imaging and radiography of the internal and near-exit flow, in addition to optical microscopy data of the near-exit sprays. Simulation results are found to agree well with available experimental data, and are able to realistically capture local and global features. The simulations allow to gain insight into the physics of gas ingestion and dribbles at EOI, for different hole diameters, operating conditions and number of holes. At SOI, timing of liquid appearance out of the injector and spray tip penetration are adequately predicted, by using the EOI flow field as in-nozzle initialization, and by prescribing the measured tip needle displacement with an informed effective valve opening point inferred from the x-ray observations. Lastly, the variation of spreading angle over time is also discussed in detail for the multi-hole case, including hole-to-hole variations. Due to real geometry features and asymmetric needle motion with eccentric components, it is found that the three holes exhibit swirling flows of increasing intensity as the lift decreases, causing the near cone angle to open and spread, in a quasi-hollow cone structure. These features are not observed in axial single-hole injectors because of their relative simplicity and intrinsic symmetry.

42 ENGINEERING↗

DOE OSTI2015

Simulation of stochastic diffusion via first exit times

In molecular biology it is of interest to simulate diffusion stochastically. In the mesoscopic model we partition a biological cell into unstructured subvolumes. In each subvolume the number of molecules is recorded at each time step and molecules can jump between neighboring subvolumes to model diffusion. The jump rates can be computed by discretizing the diffusion equation on that unstructured mesh. If the mesh is of poor quality, due to a complicated cell geometry, standard discretization methods can generate negative jump coefficients, which no longer allows the interpretation as the probability to jump between the subvolumes. We propose a method based on the mean first exit time of a molecule from a subvolume, which guarantees positive jump coefficients. Two approaches to exit times, a global and a local one, are presented and tested in simulations on meshes of different quality in two and three dimensions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2025

Investigation of CrMnV and CrMnTiV multi principal element alloys thin films for use as exit windows of electron beam accelerators

Here, this study explores CrMnV and CrMnTiV multi principal element alloy (MPEA) films as candidates for electron beam exit windows in industrial, high-power accelerators. Films were deposited via magnetron sputtering on various substrates and exposed to 66 kGy of 10 MeV e-beam irradiation. Structural and mechanical properties were analyzed using FESEM, XRD, and nanoindentation. CrMnTiV films exhibited superior grain uniformity and hardness, regardless of the substrate type. Compared to bulk materials, both MPEA films demonstrated higher hardness and excellent radiation resistance. These results highlight the potential of MPEA films as durable, radiation-tolerant materials for high-performance accelerator exit window applications.

Electron Beam Irradiation↗

DOE OSTI2012

The all-trans retinoic acid (atRA)-regulated gene Calmin (Clmn) regulates cell cycle exit and neurite outgrowth in murine neuroblastoma (Neuro2a) cells

The vitamin A metabolite all-trans retinoic acid (atRA) functions in nervous system development and regulates cell proliferation and differentiation. Neuroblastoma cells (SH-SY5Y and Neuro2a or N2A) exposed to atRA undergo growth inhibition and neuronal differentiation, both of which are preceded by an increase in Clmn mRNA. Treatment of N2A cells with atRA produces a reduction in phosphohistone 3 immunostaining and BrdU incorporation, both indicators of a reduction in cell proliferation. These effects are nearly eliminated in atRA-treated shClmn knockdown cells. Loss of Clmn in the mouse N2A cell line also results in a significant reduction of atRA-mediated neurite outgrowth, a response that can be rescued by reintroduction of the Clmn sequence. In contrast, ectopic overexpression of Clmn produces an increase in the cyclin dependent kinase inhibitor, p21{sup Cip1}, a decrease in cyclin D1 protein and an increase in hypophosphorylated Rb, showing that Clmn participates in G{sub 1}/S arrest. Clmn overexpression alone is sufficient to inhibit N2A cell proliferation, whereas both Clmn and atRA must be present to induce neurite outgrowth. This study shows that the atRA-responsive gene Clmn promotes exit from the cell cycle, a requisite event for neuronal differentiation. -- Highlights: Black-Right-Pointing-Pointer Calmin is a retinoic acid-responsive gene. Black-Right-Pointing-Pointer Calmin promotes cell cycle exit in N2A cells. Black-Right-Pointing-Pointer Calmin overexpression increases p21Cip1 and decreases cyclin D1. Black-Right-Pointing-Pointer Calmin is required for RA-induced growth inhibition and neurite outgrowth.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2023

Swift and extensive Omicron outbreak in China after sudden exit from ‘zero-COVID’ policy

In late 2022, China transitioned from a strict ‘zero-COVID’ policy to rapidly abandoning nearly all interventions and data reporting. This raised great concern about the presumably-rapid but unreported spread of the SARS-CoV-2 Omicron variant in a very large population of very low pre-existing immunity. By modeling a combination of case count and survey data, we show that Omicron spread extremely rapidly, at a rate of 0.42/day (95% credibility interval: [0.35, 0.51]/day), translating to an epidemic doubling time of 1.6 days ([1.6, 2.0] days) after the full exit from zero-COVID on Dec. 7, 2022. Consequently, we estimate that the vast majority of the population (97% [95%, 99%], sensitivity analysis lower limit of 90%) was infected during December, with the nation-wide epidemic peaking on Dec. 23. Overall, our results highlight the extremely high transmissibility of the variant and the importance of proper design of intervention exit strategies to avoid large infection waves.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2017

Structure of the Cyanuric Acid Hydrolase TrzD Reveals Product Exit Channel

Cyanuric acid hydrolases are of industrial importance because of their use in aquatic recreational facilities to remove cyanuric acid, a stabilizer for the chlorine. Degradation of excess cyanuric acid is necessary to maintain chlorine disinfection in the waters. Cyanuric acid hydrolase opens the cyanuric acid ring hydrolytically and subsequent decarboxylation produces carbon dioxide and biuret. In the present study, we report the X-ray structure of TrzD, a cyanuric acid hydrolase from Acidovorax citrulli. The crystal structure at 2.19 Å resolution shows a large displacement of the catalytic lysine (Lys163) in domain 2 away from the active site core, whereas the two other active site lysines from the two other domains are not able to move. The lysine displacement is proposed here to open up a channel for product release. Consistent with that, the structure also showed two molecules of the co-product, carbon dioxide, one in the active site and another trapped in the proposed exit channel. Previous data indicated that the domain 2 lysine residue plays a role in activating an adjacent serine residue carrying out nucleophilic attack, opening the cyanuric acid ring, and the mobile lysine guides products through the exit channel.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗