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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Development of Efficient Real-Fluid Model in Simulating Liquid Rocket Injector Flows

The characteristics of propellant mixing near the injector have a profound effect on the liquid rocket engine performance. However, the flow features near the injector of liquid rocket engines are extremely complicated, for example supercritical-pressure spray, turbulent mixing, and chemical reactions are present. Previously, a homogeneous spray approach with a real-fluid property model was developed to account for the compressibility and evaporation effects such that thermodynamics properties of a mixture at a wide range of pressures and temperatures can be properly calculated, including liquid-phase, gas- phase, two-phase, and dense fluid regions. The developed homogeneous spray model demonstrated a good success in simulating uni- element shear coaxial injector spray combustion flows. However, the real-fluid model suffered a computational deficiency when applied to a pressure-based computational fluid dynamics (CFD) code. The deficiency is caused by the pressure and enthalpy being the independent variables in the solution procedure of a pressure-based code, whereas the real-fluid model utilizes density and temperature as independent variables. The objective of the present research work is to improve the computational efficiency of the real-fluid property model in computing thermal properties. The proposed approach is called an efficient real-fluid model, and the improvement of computational efficiency is achieved by using a combination of a liquid species and a gaseous species to represent a real-fluid species.

Cheng, Gary↗
DOE OSTI2019

lNAC's OPTIMUS{sup TM}-L Package - the Next Transformation - 19396

NAC has developed the OPTIMUS{sup TM}-L package, the newest addition to the OPTIMUS{sup TM} packaging product line. OPTIMUS{sup TM}-L is a Type B(U)F-96 transportation package designed for maximum flexibility and cost-efficiency to support shipment of a wide range of challenging low-activity wastes. The OPTIMUS{sup TM}-L package utilizes the same cask containment vessel (CCV) as its predecessor, OPTIMUS{sup TM}-H, packaged inside lightweight outer packaging. The large cavity size of the CCV, which can accommodate a 110-gallon drum, combined with the small size and modularity of the OPTIMUS{sup TM}-L package provides unmatched flexibility for the user. OPTIMUS{sup TM}-L can accommodate more radioactive waste in each drum (up to a Fissile Gram Equivalent (FGE) limit of 395 g Pu-239) than larger packages can in 10 drums. Furthermore, because of its small size and weight, up to ten (10) OPTIMUS{sup TM}-L packages can be accommodated per legal-weight truck shipment. Thus, one Legal Weight Truck (LWT) shipment of 10 OPTIMUS{sup TM}-L packages can accommodate more than 10 times the FGE as a large package containing 10 drums. OPTIMUS{sup TM}-L contents include low level waste, mixed low-level waste, intermediate level waste and contact handled transuranic (CH-TRU) waste. Furthermore, all contents can include aerosol cans with compressed gas and liquefied gas propellants and standard Department of Transportation (DOT) 3E lecture bottles for shipment to treatment facilities. The OPTIMUS{sup TM}-L is also designed to accommodate irradiated fuel debris and other fissile material waste, which may be packaged inside shield inserts if required for supplemental radiation shielding. In this paper, NAC provides a technical overview of the OPTIMUS{sup TM}-L package and identifies the design features and technology advancements that makes the OPTIMUS{sup TM} product line a readily adaptable and flexible solution for packaging DOE and other orphan wastes and enables the integration of these wastes into the waste management system process and disposition infrastructure. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Ion Solvation-Driven Liquid–Liquid Phase Separation in Divalent Electrolytes with Miscible Organic Solvents

Liquid–liquid phase separation (LLPS) is a common phenomenon, but LLPS of electrolytes prepared in miscible organic solvents is rarely documented. Here we report four cases of LLPS that occur in MgTFSI 2 or ZnTFSI 2 electrolytes in mixed organic solvents. The conditions for the formation of this LLPS share four common features: cations with high charge density; bulky anions with low charge density; a strongly coordinating solvent with high compressibility; and a relatively weak coordinating solvent with low relative permittivity and high mobility. With these conditions, the cations tend to draw the strongly coordinating solvents together to form a densely-packed, energetically-favorable ion solvation region, while the cosolvents with low relative permittivity tend to repel ions to form an ion-depleted dilute phase. Furthermore, in the dilute upper layer with more than 300 solvent molecules per cation, ion pairs and large ion aggregates are clearly evidenced, due to the incomplete screening of electrostatic interactions by the weaker cosolvent. This LLPS driven by ion solvation may be more common in multivalent electrolytes and is a design consideration with mixed solvents that should not be overlooked.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Mitigating CO 2 emissions of concrete manufacturing through CO 2 -enabled binder reduction

Abstract Past studies on CO 2 utilization in the concrete industry have primarily focused on maximizing sequestered CO 2 , while focusing less on CO 2 avoidance possible by reducing binder use through the addition of CO 2 to concrete formulations. In this paper, we study the net CO 2 reduction and cost benefits achievable by reducing binder loading while adding CO 2 via three approaches: carbonation during curing, carbonation during mixing, or carbonation with recycled concrete aggregate. These techniques are evaluated for a cohort of concrete formulations representing the diverse mixture designs found in the US ready-mixed and precast industries. Each formulation is optimized for reduced binder loading where the use of CO 2 directly in the formulation recovers the lost compressive strength from reduced binder. We show that over an order of magnitude more CO 2 can be avoided when binder reduction is jointly implemented with CO 2 utilization compared to utilizing CO 2 alone. As a result, nearly 40% of the annual CO 2 emissions from the US concrete industry could, in principle, be eliminated without relying on novel supplemental materials, alternative binder, or carbon capture and sequestration. The recently amended 45Q tax credit will not incentivize this strategy, as it only considers carbon sequestration. However, we find that the saved material cost from reduced binder use on its own may provide a significant economic incentive to promote the joint strategy in practice. We conclude that the real value of CO 2 utilization in concrete hinges on exploiting CO 2 -induced property changes to yield additional emission reduction, not by maximizing absorbed CO 2 .

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

Preliminary feasibility analysis of a pressure modulator radiometer for remote sensing of tropospheric constituents

A pressure modulator radiometer operated in a nadir viewing mode from the top of a midlatitude summer model of the atmosphere was theoretically studied for monitoring the mean volumetric mixing ratio of carbon monoxide in the troposphere. The mechanical characteristics of the instrument on the Nimbus 7 stratospheric and mesospheric sounder experiment are assumed and CO is assumed to be the only infrared active constituent. A line by line radiative transfer computer program is used to simulate the upwelling radiation reaching the top of the atmosphere. The performance of the instrument is examined as a function of the mean pressure in and the length of the instrument gas correlation cell. Instrument sensitivity is described in terms of signal to noise ratio for a 10 percent change in CO mixing ratio. Sensitivity to mixing ratio changes is also studied. It is concluded that tropospheric monitoring requires a pressure modulator drive having a larger swept volume and producing higher compression ratios at higher mean cell pressures than the Nimbus 7 design.

Orr, H. D., III↗
NASA NTRS1986

Remotely controllable mixing system

This invention relates to a remotely controllable mixing system in which a plurality of mixing assemblies are arranged in an annular configuration, and wherein each assembly employs a central chamber and two outer, upper and lower chambers. Valves are positioned between chambers, and these valves for a given mixing assembly are operated by upper and lower control rotors, which in turn are driven by upper and lower drive rotors. Additionally, a hoop is compressed around upper control rotors and a hoop is compressed around lower control rotors to thus insure constant frictional engagement between all control rotors and drive rotors. The drive rollers are driven by a motor.

Belew, R. R.↗
NASA NTRS1986

A review of aerothermal problems associated with hypersonic flight

A review is presented of some important aerothermal problems associated with hypersonic flight with emphasis on those involved with viscous/inviscid interaction. The flow regimes of importance to hypersonic vehicles of current interest are discussed and the performance of experimental facilities currently available to study real gas phenomena associated with hypervelocity flight are briefly reviewed. Viscous interaction and real gas effects in hypervelocity flight at high altitudes are discussed with reference to measurements which are required to support the development of improved prediction capabilities in this regime. Theoretical and experimental research on 2D and 3D shock wave/laminar boundary layer interaction relevant to the performance of control surfaces and inlets in hypersonic flight at high altitudes is reviewed. The characteristics of transition regions in hypersonic flows are discussed with particular reference to transitional flows over nosetips and swept leading edges. Studies of shock interaction phenomena on indented nosetips are discussed, followed by a review of the surface roughness and blowing effects. Research to describe the characteristics of 2D and 3D regions of shock wave/turbulent boundary layer interaction in hypersonic flow is reviewed with particular reference to intrinsic unsteadiness and potential compressibility effects in these flows. This review is concluded with a brief discussion of observations suggesting a decrease in the spreading rate in shear layer mixing in hypersonic flow.

Holden, M. S.↗
NASA NTRS1992

Bandwidth compression of noisy signals with square-wave subcarrier

This article discusses a method for downconverting the square-wave subcarrier of spacecraft signals, such as the one from Galileo, which results in a compression bandwidth that lowers the sample rate significantly. The study is focused on three issues. The first is the selection of an adequate down-mixing signal for the resulting signal to have a format similar to that of the original signal, except at a lower subcarrier frequency. The second is the control of the noise level so that the signal to noise ratio is not degraded due to the downconversion. The third is to determine the bandwidth of the downconverted signal considering the uncertainty of the residual carrier frequency.

Feria, Y.↗
NASA NTRS2004

NASA Tech Briefs, December 2004

opics include: High-Rate Digital Receiver Board; Signal Design for Improved Ranging Among Multiple Transceivers; Automated Analysis, Classification, and Display of Waveforms; Fast-Acquisition/Weak-Signal-Tracking GPS Receiver for HEO; Format for Interchange and Display of 3D Terrain Data; Program Analyzes Radar Altimeter Data; Indoor Navigation using Direction Sensor and Beacons; Software Assists in Responding to Anomalous Conditions; Software for Autonomous Spacecraft Maneuvers; WinPlot; Software for Automated Testing of Mission-Control Displays; Nanocarpets for Trapping Microscopic Particles; Precious-Metal Salt Coatings for Detecting Hydrazines; Amplifying Electrochemical Indicators; Better End-Cap Processing for Oxidation-Resistant Polyimides; Carbon-Fiber Brush Heat Exchangers; Solar-Powered Airplane with Cameras and WLAN; A Resonator for Low-Threshold Frequency Conversion; Masked Proportional Routing; Algorithm Determines Wind Speed and Direction from Venturi-Sensor Data; Feature-Identification and Data-Compression Software; Alternative Attitude Commanding and Control for Precise Spacecraft Landing; Inspecting Friction Stir Welding using Electromagnetic Probes; and Helicity in Supercritical O2/H2 and C7H16/N2 Mixing Layers.

Source record↗
DOE OSTI2023

Simulation of a rapid compression machine for evaluation of ignition chemistry and soot formation using gasoline/ethanol blends

Due to the projected decline of demand for gasoline in light duty engines and the advent of ethanol as a green fuel, the use of gasoline/ethanol blend fuels in heavy duty applications are being investigated as they are projected to have lower cost and lower lifecycle green house gas (GHG) emissions. In heavy duty engines, the primary mode of combustion is mixing controlled combustion where wide range of mixture conditions (equivalence ratio) exist. Soot emissions of these fuels in richer conditions are not well understood. The goal of this research is to evaluate some commercially available soot modeling codes for the particulate matter emissions from gasoline/ethanol fuel blends, especially at fuel rich conditions. A Rapid Compression Machine (RCM) is modeled in a three-dimensional numerical simulation using CONVERGE computational software using a reduced chemical kinetic mechanism with SAGE chemistry solver and a RANS k-ϵturbulence model with a sector model including the creviced piston. The creviced piston is used in the experimental setup to reduce boundary layer effects and to maintain a homogeneous core in the reaction cylinder. Computational fluid dynamics simulations are conducted for different gasoline-ethanol fuel blends from E10 (10% ethanol v/v) to E100. The fuel blend is modeled as a surrogate mixture of toluene, iso-octane, n-heptane for gasoline content, and ethanol. The computational results were validated against experimental results using pressure measurements and laser extinction diagnostics. Different soot models are investigated to evaluate their capability of predicting the sooting tendencies of fuel blends, especially in richer conditions experienced during mixing-controlled combustion. The experimental combustion characteristics such as the ignition delay of different blends of fuel are reasonably well predicted. The Particulate Size Mimic (PSM) model accurately predicts the soot generation characteristics of the different fuels, but the Hiroyasu-NSC model falls short in this regard. For accurate prediction of soot with the PSM model, the thermodynamic conditions during combustion must be accurately modeled. While the current computational modeling tools can produce accurate results for the prediction of particulate matter emissions, there is much work to be done in improving our understanding of the underlying fundamental processes.

Energy & Fuels↗
NASA NTRS2016

Multiscale Static Analysis of Notched and Unnotched Laminates Using the Generalized Method of Cells

The generalized method of cells (GMC) is demonstrated to be a viable micromechanics tool for predicting the deformation and failure response of laminated composites, with and without notches, subjected to tensile and compressive static loading. Given the axial [0], transverse [90], and shear [+45/-45] response of a carbon/epoxy (IM7/977-3) system, the unnotched and notched behavior of three multidirectional layups (Layup 1: [0,45,90,-45](sub 2S), Layup 2: [0,60,0](sub 3S), and Layup 3: [30,60,90,-30, -60](sub 2S)) are predicted under both tensile and compressive static loading. Matrix nonlinearity is modeled in two ways. The first assumes all nonlinearity is due to anisotropic progressive damage of the matrix only, which is modeled, using the multiaxial mixed-mode continuum damage model (MMCDM) within GMC. The second utilizes matrix plasticity coupled with brittle final failure based on the maximum principle strain criteria to account for matrix nonlinearity and failure within the Finite Element Analysis--Micromechanics Analysis Code (FEAMAC) software multiscale framework. Both MMCDM and plasticity models incorporate brittle strain- and stress-based failure criteria for the fiber. Upon satisfaction of these criteria, the fiber properties are immediately reduced to a nominal value. The constitutive response for each constituent (fiber and matrix) is characterized using a combination of vendor data and the axial, transverse, and shear responses of unnotched laminates. Then, the capability of the multiscale methodology is assessed by performing blind predictions of the mentioned notched and unnotched composite laminates response under tensile and compressive loading. Tabulated data along with the detailed results (i.e., stress-strain curves as well as damage evolution states at various ratios of strain to failure) for all laminates are presented.

GMC↗
NASA NTRS1961

Applicability of Mixing Length Theory to a Turbulent Vortex System

The ability of mixing length theory to correlate vortex data is evaluated. Expressions are derived for eddy diffusivity by applying the techniques of von Karman and Prandtl which have been established for pipe flow. Total and static pressures were measured from the outer radius to the exhaust-nozzle radius of a vortex generator for a range of mass flows. These data are combined with Navier-Stokes solutions for this region of a compressible vortex to determine turbulent Reynolds numbers. The Reynolds number is related to Prandtl and Karman functions for various assumed boundary conditions, and the experimental data are used to determine the usefulness of these expressions. The following conclusions were reached: (1) Mixing length functions developed by applying von Karman's similarity hypothesis to vortex motion correlate the data better than do Prandtl functions obtained with the assumption that mixing length is proportional to radius. (2) Some of the expressions developed do not adequately represent the experimental data. (3) The data are correlated with acceptable scatter by evaluating the fluid radial inertia at the outer boundary and the shear stress at the inner boundary. The universal constant K was found to be 0.04 to 0.08, rather than the value of 0.4 which is accepted for rectilinear flow. (4) The data are best correlated by a modified Karman expression which includes an effect of radial inertia, as well as shear stress, on eddy diffusivity.

Ragsdale, Robert G.↗
DOE OSTI2019

Experimental observations of large changes in electron density distributions in β - Ge

We report the electron density distributions in β-Ge have been experimentally determined at in situ high-pressure conditions using synchrotron diffraction techniques in a diamond anvil cell. Upon decompression, the electron density along the $c$ axis in tetragonal β-Ge displays a sudden drop at 10–11 GPa close to that of the structural α-β transition, while the β-Ge samples remain as single crystals until transforming to metastable Ge phases around 6.7–8.5 GPa. In contrast to the covalently bonded α-Ge that displays only a weak participation of $d$ electrons in the valence band under compression above 7.7 GPa, our experimental results suggest that a large change in $d$-orbital participation can occur in the β-Ge lattice which has mixed covalent and metallic bonding. The β-Ge below 10 GPa may display large fluctuations in electronic properties, which sheds light for exploring novel materials with intriguing electronic and optical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Viscosity Measurements in Extreme Conditions

Radiation-hydrodynamics simulations are critical to the NNSA complex for understanding high energy density physics and for addressing problems in national security science. However, current rad-hydro codes typically do not account for viscosity, which generally leads to large uncertainties in problems involving mixing of materials under shock loading. This report details progress made towards experimental measurements of fluid viscosity at high pressures and temperatures achieved by shock wave compression techniques, as well as complementary material model development and hydrodynamic simulations.

36 MATERIALS SCIENCE↗
NASA NTRS1986

Comparisons between thermodynamic and one-dimensional combustion models of spark-ignition engines

Results from a one-dimensional combustion model employing a constant eddy diffusivity and a one-step chemical reaction are compared with those of one-zone and two-zone thermodynamic models to study the flame propagation in a spark-ignition engine. One-dimensional model predictions are found to be very sensitive to the eddy diffusivity and reaction rate data. The average mixing temperature found using the one-zone thermodynamic model is higher than those of the two-zone and one-dimensional models during the compression stroke, and that of the one-dimensional model is higher than those predicted by both thermodynamic models during the expansion stroke. The one-dimensional model is shown to predict an accelerating flame even when the front approaches the cold cylinder wall.

Ramos, J. I.↗
NASA NTRS1997

Large Scale Turbulent Structures in Supersonic Jets

Jet noise is a major concern in the design of commercial aircraft. Studies by various researchers suggest that aerodynamic noise is a major contributor to jet noise. Some of these studies indicate that most of the aerodynamic jet noise due to turbulent mixing occurs when there is a rapid variation in turbulent structure, i.e. rapidly growing or decaying vortices. The objective of this research was to simulate a compressible round jet to study the non-linear evolution of vortices and the resulting acoustic radiations. In particular, to understand the effect of turbulence structure on the noise. An ideal technique to study this problem is Direct Numerical Simulations (DNS), because it provides precise control on the initial and boundary conditions that lead to the turbulent structures studied. It also provides complete 3-dimensional time dependent data. Since the dynamics of a temporally evolving jet are not greatly different from those of a spatially evolving jet, a temporal jet problem was solved, using periodicity in the direction of the jet axis. This enables the application of Fourier spectral methods in the streamwise direction. Physically this means that turbulent structures in the jet are repeated in successive downstream cells instead of being gradually modified downstream into a jet plume. The DNS jet simulation helps us understand the various turbulent scales and mechanisms of turbulence generation in the evolution of a compressible round jet. These accurate flow solutions will be used in future research to estimate near-field acoustic radiation by computing the total outward flux across a surface and determine how it is related to the evolution of the turbulent solutions. Furthermore, these simulations allow us to investigate the sensitivity of acoustic radiations to inlet/boundary conditions, with possible appli(,a- tion to active noise suppression. In addition, the data generated can be used to compute, various turbulence quantities such as mean velocities, turbulent stresses, etc. which will aid in turbulence modeling. This report will be presented in two chapters. The first chapter describes some work on the linear stability of a supersonic round jet and the implications of this for the jet noise problem. The second chapter is an extensive discussion of numerical work using the spectral method which we use to solve the compressible Navier-Stokes equations to study turbulent jet flows. The method uses Fourier expansions in the azimuthal and streamwise direction and a 1-D B-spline basis representation in the radial direction. The B-spline basis is locally supported and this ensures block diagonal matrix equations which can be solved in O(N) steps. This is a modification of a boundary layer code developed by Robert Moser. A very accurate highly resolved DNS of a turbulent jet flow is produced.

Rao, Ram Mohan↗
NASA NTRS1997

Large Scale Turbulent Structures in Supersonic Jets

Jet noise is a major concern in the design of commercial aircraft. Studies by various researchers suggest that aerodynamic noise is a major contributor to jet noise. Some of these studies indicate that most of the aerodynamic jet noise due to turbulent mixing occurs when there is a rapid variation in turbulent structure, i.e. rapidly growing or decaying vortices. The objective of this research was to simulate a compressible round jet to study the non-linear evolution of vortices and the resulting acoustic radiations. In particular, to understand the effect of turbulence structure on the noise. An ideal technique to study this problem is Direct Numerical Simulations(DNS), because it provides precise control on the initial and boundary conditions that lead to the turbulent structures studied. It also provides complete 3-dimensional time dependent data. Since the dynamics of a temporally evolving jet are not greatly different from those, of a spatially evolving jet, a temporal jet problem was solved, using periodicity ill the direction of the jet axis. This enables the application of Fourier spectral methods in the streamwise direction. Physically this means that turbulent structures in the jet are repeated in successive downstream cells instead of being gradually modified downstream into a jet plume. The DNS jet simulation helps us understand the various turbulent scales and mechanisms of turbulence generation in the evolution of a compressible round jet. These accurate flow solutions will be used in future research to estimate near-field acoustic radiation by computing the total outward flux across a surface and determine how it is related to the evolution of the turbulent solutions. Furthermore, these simulations allow us to investigate the sensitivity of acoustic radiations to inlet/boundary conditions, with possible application to active noise suppression. In addition, the data generated can be used to compute various turbulence quantities such as mean velocities, turbulent stresses, etc. which will aid in turbulence modeling. This report will be presented in two chapters. The first chapter describes some work on the linear stability of a supersonic round jet and the implications of this for the jet noise problem. The second chapter is an extensive discussion of numerical work using the spectral method which we use to solve the compressible Navier-Stokes equations to study turbulent jet flows. The method uses Fourier expansions in the azimuthal and streamwise direction and a 1-D B-spline basis representation in the radial direction. The B-spline basis is locally supported and this ensures block diagonal matrix equations which can be solved in O(N) steps. This is a modification of a boundary layer code developed by Robert Moser. A very accurate highly resolved Direct Numerical Simulation (DNS) of a turbulent jet flow is produced.

Rao, Ram Mohan↗
DOE OSTI2020

Ducted Fuel Injection vs. Free-Spray Injection: A Study of Mixing and Entrainment Effects Using Numerical Modeling

Diesel engines are an important technology for transportation of both people and goods. However, historically they have suffered a significant downside of high soot and nitrogen oxides (NO x ) emissions. Recently, ducted fuel injection (DFI) has been demonstrated to attenuate soot formation in compression-ignition engines and combustion vessels by 50% to 100%. This allows for diesel engines to be run at low-NO x emissions that would have otherwise produced significantly more soot due to the soot/NO x tradeoff. Currently the root causes of this soot attenuation are not well understood. To be able to better optimize DFI for use across a variety of engines and conditions, it is important to understand clearly how it works. This study expands on the current understanding of DFI by using numerical modeling under nonreacting conditions to provide insights about the roles of entrainment and mixing that would have been much more challenging to obtain experimentally. We report this study found that DFI enhances charge gas entrainment upstream of the duct and blocks entrainment inside of the duct. Mixing is enhanced by the duct, which results in lower peak equivalence ratios at the exit of the duct.

42 ENGINEERING↗