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Results for “Effective Lewis number”

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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Well-designed Crosslinked Polymer Electrolyte Enables High Ionic Conductivity and Enhanced Salt Solvation

A new facile single-step method to fabricate crosslinked polymer electrolyte membranes consisting of branched poly(ethyleneimine), (PEI) and poly(ethylene oxide), (PEO) is demonstrated. The membranes exhibit excellent ionic conductivity (1.2 × 10 –3 S cm –1 at 80 °C) with minimal addition of plasticizer (20 wt%). The amine functional group in the PEI-PEO crosslinked matrix provides Lewis basic and hydrogen bonding characteristics that facilitate the dissolution of lithium salt and enables a higher cation transport number than a PEO crosslinked matrix. The glass transition temperature, degree of crystallinity, and room temperature storage modulus increases with decreasing crosslink density and increasing ratio of free amines. The resultant ionic conductivity and mechanical strength can be flexibly tailored by varying the molar ratio of free amine moieties in the crosslinked PEI-PEO matrix. This study provides an improved synthesis method, in-depth characterization, and fundamental insights on the effect of free amine moieties on the transport properties of a highly conductive gel polymer electrolyte.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Expanding the Solar Workforce through the Illinois Community College System

The Illinois Green Economy Network (IGEN) is a consortium of all 39 Illinois community college districts working to grow the green economy in the state. The network aims to build capacity in sustainability and transform education by connecting business/industry and educators to resources, curating information and tools, cultivating partnerships, and advocating for change. Led by IGEN, the goal of the “Expanding the Solar Workforce through the Illinois Community College System” project was to create and sustain a comprehensive, statewide strategy that equips education and training providers, workers, businesses, and communities with resources and tools to prepare a solar workforce. A cohort of five Illinois community colleges participated in the program based on their capacity and interest, as well as their potential for and proximity to industry growth in the state: City Colleges of Chicago, John A. Logan College, Kankakee Community College, Lewis and Clark Community College, and Lincoln Land Community College. The project had three Objectives, 1) Address an unmet need by increasing the pool of skilled solar workers, 2) Keep pace with evolving needs of the solar workforce by improving programs to be more accessible and industry-driven, 3) Strengthen IGEN’s capacity as a statewide resource for solar education, training, and workforce initiatives. Overall, over 400 students were trained in solar installation practices, with over 40 businesses engaged. Additionally. the project spurred a number of innovations and the development of effective practices related to establishing and maintaining a solar installation program at a community college. This project sought to identify effective and scalable practices for developing a solar installation program which included the following components: enrolling students into aligned programs; developing curriculum and courses which meet industry needs; placing students in solar installation or related employment; and sustaining programming past grant funding. Through this project- IGEN was able to identify critical components of a solar installation program. Detailed further in this report these components describe 1) Necessary conditions for establishing a solar installation program, 2) Program structures use cases for different contexts, 3) Effective practices related to student pipeline development and program throughout. As a result of this project- all five participating community colleges have expressed support for continuing to offer solar installation training to their students. Additionally, three nonparticipating colleges in IGEN have expressed interest in adopting practice, courses, or curriculum developed through this program. IGEN has also committed to making the curriculum, course structure and other materials available on their website for accelerated adoption of effective practices both state and nationwide.

14 SOLAR ENERGY↗
NASA NTRS1986

Application of a linearized unsteady aerodynamic analysis to standard cascade configurations

A linearized potential flow analysis, which accounts for the effects of nonuniform steady flow phenomena on the linearized unsteady aerodynamic response to prescribed blade motions, has been applied to five cascade configurations. These include the first, fifth, eighth and ninth standard configurations proposed as a result of the Second International Symposium on Aeroelasticity in Turbomachines and a NASA Lewis flutter cascade. Selected results from this study, including comparisons between analytical predictions and the experimental measurements submitted for three of the foregoing configurations, are described. The correlation between theory and experiment for the first standard configuration (a compressor cascade operating at low Mach number and frequency) is quite good. Moreover, the predictions and measurements for the NASA Lewis cascade of symmetric biconvex airfoils show good qualitative agreement. However, wide discrepancies exist between the theoretical predictions and the experimental measurements for the fifth standard configuration (a subsonic transonic fan tip cascade). These can be partially attributed to conditions being imposed in the experiment which differ from those commonly used in unsteady aerodynamic analyses.

Verdon, J. M.↗
NASA NTRS1997

Composite Matrix Regenerator for Stirling Engines

This project concerns the design, fabrication and testing of carbon regenerators for use in Stirling power convertors. Radial fiber design with nonmetallic components offers a number of potential advantages over conventional steel regenerators: reduced conduction and pressure drop losses, and the capability for higher temperature, higher frequency operation. Diverse composite fabrication methods are explored and lessons learned are summarized. A pulsed single-blow test rig has been developed that has been used for generating thermal effectiveness data for different flow velocities. Carbon regenerators have been fabricated by carbon vapor infiltration of electroflocked preforms. Performance data in a small Stirling engine are obtained. Prototype regenerators designed for the BP-1000 power convertor were fabricated and delivered to NASA-Lewis.

Knowles, Timothy R.↗
NASA NTRS1987

An analytical and experimental investigation of resistojet plumes

As a part of the electrothermal propulsion plume research program at the NASA Lewis Research Center, efforts have been initiated to analytically and experimentally investigate the plumes of resistojet thrusters. The method of Simons for the prediction of rocket exhaust plumes is developed for the resistojet. Modifications are made to the source flow equations to account for the increased effects of the relatively large nozzle boundary layer. Additionally, preliminary mass flux measurements of a laboratory resistojet using CO2 propellant at 298 K have been obtained with a cryogenically cooled quartz crystal microbalance (QCM). There is qualitative agreement between analysis and experiment, at least in terms of the overall number density shape functions in the forward flux region.

Zana, Lynnette M.↗
NASA NTRS1999

Thermomechanical Fatigue Durability of T650-35/PMR-15 Sheet-Molding Compound Evaluated

High-performance polymer matrix composites (PMC's) continue to be the focus of a number of research efforts aimed at developing cost-effective, lightweight material alternatives for advanced aerospace and aeropropulsion applications. These materials not only offer significant advantages in specific stiffness and strength over their current metal counterparts, but they can be designed and manufactured to eliminate joints and fasteners by combining individual components into integral subassemblies, thus making them extremely attractive for commercial applications. With much emphasis on the low-cost manufacturing aspects of advanced composite structures, there is heightened interest in high-performance sheet-molding compounds (SMC's). Researchers at the NASA Lewis Research Center, in cooperation with the Allison Advanced Development Company, completed an investigation examining the use of T650-35/PMR-15 SMC for a midstage inner-vane endwall application within a gas turbine engine compressor. This component resides in the engine flow path and is subjected not only to high airflow rates, but also to elevated temperatures and pressures. This application is unique in that it represents a very aggressive use of high-performance SMC's, raising obvious concerns related to durability and property retention in the presence of microstructural damage. Therefore, it was necessary to evaluate the fatigue behavior and damage tolerance of this material subjected to a representative thermomechanical fatigue (TMF) mission-cycle loading spectrum.

Castelli, Michael G.↗
NASA NTRS1973

Experimental study of supersonic laminar base flow with and without suction

Heat-transfer and pressure distributions in laminar separated flows downstream of rearward-facing steps with and without mass suction were investigated at Mach numbers around 4 for the conditions when the boundary-layer thickness was comparable to or larger than the step height. In both suction and no-suction cases, an increase of the step height resulted in a sharp drop of the base heating rates, which then gradually recovered to less than or near attached-flow values obtained with flat-plate configuration. Mass suction from the step base area increased the local heating rates; this effect, however, was relatively weak for laminar flows tested, and the competing effect of the step height clearly predominated. It was found that even removal of the entire incoming boundary layer was not sufficient to raise the poststep heating rates above the flat-plate values. The base pressure in the no-suction, solid-step case correlated reasonably well with the step height-to-boundary-layer thickness ratio and with the Reynolds number based on the step height.

Jakubowski, A. K.↗
NASA NTRS1970

Design problems of small turbomachinery

Advanced design and testing techniques developed at NASA Lewis to achieve high efficiency in small turbomachines are described. Small radial and axial turbines and compressors were built for space power systems and associated studies at the Lewis Research Center. A six stage axial compressor of 3.5 inches diameter and axial turbines of 5 and 8.5 inches diameter were included. Radial turbines and compressors ranged from 3.5 to 6 inches. Topics discussed include maximum efficiency as a function of speed, the effect of compressibility on passage size, the use of quasi-orthogonals to calculate cross-channel velocity gradients, a design point velocity diagram study for axial turbines, and estimating off-design performance. Special turbine instruments and calibration procedures were developed to test compressors and turbines, to determine Reynolds and size number effects clearance, specific speed effects, and compressor performance. Laboratory tests conducted to study system operation and shaft and bearing motions are also reviewed.

Rohlik, H. E.↗
NASA NTRS1987

An analytical and experimental investigation of resistojet plumes

As a part of the electrothermal propulsion plume research program at the NASA Lewis Research Center, efforts have been initiated to analytically and experimentally investigate the plumes of resistojet thrusters. The method of G.A. Simons for the prediction of rocket exhaust plumes is developed for the resistojet. Modifications are made to the source flow equations to account for the increased effects of the relatively large nozzle boundary layer. Additionally, preliminary mass flux measurements of a laboratory resistojet using CO2 propellant at 298 K have been obtained with a cryogenically cooled quartz crystal microbalance (QCM). There is qualitative agreement between analysis and experiment, at least in terms of the overall number density shape functions in the forward flux region.

Zana, L. M.↗
NASA NTRS1998

Mechanical Characterization of Thermomechanical Matrix Residual Stresses Incurred During MMC Processing

In recent years, much effort has been spent examining the residual stress-strain states of advanced composites. Such examinations are motivated by a number of significant concerns that affect composite development, processing, and analysis. The room-temperature residual stress states incurred in many advanced composite systems are often quite large and can introduce damage even prior to the first external mechanical loading of the material. These stresses, which are induced during the cooldown following high-temperature consolidation, result from the coefficient of thermal expansion mismatch between the fiber and matrix. Experimental techniques commonly used to evaluate composite internal residual stress states are non-mechanical in nature and generally include forms of x-ray and neutron diffraction. Such approaches are usually complex, involving a number of assumptions and limitations associated with a wide range of issues, including the depth of penetration, the volume of material being assessed, and erroneous effects associated with oriented grains. Furthermore, and more important to the present research, these techniques can assess only "single time" stress in the composite. That is, little, if any, information is obtained that addresses the time-dependent point at which internal stresses begin to accumulate, the manner in which the accumulation occurs, and the presiding relationships between thermoelastic, thermoplastic, and thermoviscous behaviors. To address these critical issues, researchers at the NASA Lewis Research Center developed and implemented an innovative mechanical test technique to examine in real time, the time-dependent thermomechanical stress behavior of a matrix alloy as it went through a consolidation cycle.

Castelli, Michael G.↗
NASA NTRS1955

Altitude Performance of Modified J71 Afterburner with Revised Engine Operating Conditions

An investigation was conducted in an altitude test chamber at the NACA Lewis laboratory to determine the effect of a revision of the rated engine operating conditions and modifications to the afterburner fue1 system, flameholder, and shell cooling on the augmented performance of the J71-A-2 (x-29) turbo jet engine operating at altitude . The afterburner modifications were made by the manufacturer to improve the endurance at sea-level, high-pressure conditions and to reduce the afterburner shell temperatures. The engine operating conditions of rated rotational speed and turbine-outlet gas temperature were increased. Data were obtained at conditions simulating flight at a Mach number of 0.9 and at altitudes from 40,000 to 60,000 feet. The afterburner modifications caused a reduction in afterburner combustion efficiency. The increase in rated engine speed and turbine-outlet temperature coupled with the afterburner modifications resulted in the over-all thrust of the engine and afterburner being unchanged at a given afterburner equivalence ratio, while the specific fuel consumption was increased slightly. A moderate shift in the range of equivalence ratios over which the afterburner would operate was encountered, but the maximum operable altitude remained unaltered. The afterburner-shell temperatures were also slightly reduced because of the modifications to the afterburner.

Useller, James W.↗
NASA NTRS1976

A high-pressure, high-temperature combustor and turbine-cooling test facility

NASA-Lewis Research Center is presently constructing a new test facility for developing turbine-cooling and combustor technology for future generation aircraft gas turbine engines. Prototype engine hardware will be investigated in this new facility at gas stream conditions up to 2480 K average turbine inlet temperature and 4,140,000 N per sq m turbine inlet pressure. The facility will have the unique feature of fully-automated control and data acquisition through the use of an integrated system of minicomputers and programmable controllers, which will result in more effective use of operating time, will limit the number of operators required, and will provide a built-in self-protection safety system. The paper describes the facility and the planning and design considerations involved.

Cochran, R. P.↗
NASA NTRS2001

Markstein Numbers of Negatively-Stretched Premixed Flames: Microgravity Measurements and Computations

The effect of flame stretch, composed of strain and curvature, plays a major role in the propagation of turbulent premixed flames. Although all forms of stretch (positive and negative) are present in turbulent conditions, little research has been focused on the stretch due to curvature. The present study quantifies the Markstein number (which characterizes the sensitivity of the flame propagation speed to the imposed stretch rate) for an inwardly-propagating flame (IPF). This flame is of interest because it is negatively stretched, and is subjected to curvature effects alone, without the competing effects of strain. In an extension of our previous work, microgravity experiments were run using a vortex-flame interaction to create a pocket of reactants surrounded by an IPF. Computations using the RUN-1DL code of Rogg were also performed in order to explain the measurements. It was found that the Markstein number of an inwardly-propagating flame, for both the microgravity experiment and the computations, is significantly larger than that of an outwardly-propagating flame. Further insight was gained by running the computations for the simplified (hypothetical) cases of one step chemistry, unity Lewis number, and negligible heat release. Results provide additional evidence that the Markstein numbers associated with strain and curvature have different values.

Ibarreta, Alfonso F.↗
NASA NTRS1997

Effects of Rotor Wake on Film Cooling Investigated

Through a combination of experimental and computational studies, researchers at the NASA Lewis Research Center investigated the effect of upstream blade-row wake passing on the showerhead (leading edge) film cooling of a downstream turbine. The experiments were performed in a steady-flow annular turbine cascade facility equipped with an upstream rotating row of cylindrical rods to produce a periodic wake field similar to that found in an actual turbine. Spanwise, chordwise, and temporal resolution of the blade surface temperature were achieved through the use of an array of nickel thin-film surface gauges covering one unit cell of a showerhead film hole pattern. Film effectiveness and Nusselt numbers were determined for a test matrix of various injectants, injectant blowing ratios, and wake Strouhal numbers (St).

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NASA NTRS1986

Isolated testing of highly maneuverable inlet con cepts

Ten percent scale models of a Mach 2.2 two dimensional inlet and a Mach 2.0 axisymmetric inlet were tested in the NASA Lewis Research Center 8'x6' Supersonic Wind Tunnel as part of a cooperative effort with the McDonnell Aircraft Company. The objective of this effort was to test methods designed to increase the maneuvering performance of fighter aircraft inlets. Maneuvering improvement concepts were tested up to 40-deg angle of attack for Mach numbers of 0.6 and 0.9, and up to 25 deg for Mach numbers 1.2 and 1.4. Maneuvering improvement concepts included a rotating cowl lip, auxiliary inlets aft of the inlet throat, and a retracting centerbody for the axisymmetric inlet. Test results show that the rotating cowl design was effective in improving subsonic maneuvering performance for both inlets. Auxiliary inlets did not produce significant performance increases for either model. The retracted centerbody resulted in some performance benefits at high angles of attack. None of the maneuvering improvement concepts were effective at Mach 1.2 and 1.4.

Norby, W. P.↗
DOE OSTI2023

Increasing the bulk of the 1TEL–target linker and retaining the 10×His tag in a 1TEL–CMG2-vWa construct improves crystal order and diffraction limits

TELSAM-fusion crystallization has the potential to become a revolutionary tool for the facile crystallization of proteins. TELSAM fusion can increase the crystallization rate and enable crystallization at low protein concentrations, in some cases with minimal crystal contacts [Nawarathnage et al. (2022), Open Biol. 12 , 210271]. Here, requirements for the linker composition between 1TEL and a fused CMG2 vWa domain were investigated. Ala-Ala, Ala-Val, Thr-Val and Thr-Thr linkers were evaluated, comparing metrics for crystallization propensity and crystal order. The effect on crystallization of removing or retaining the purification tag was then tested. It was discovered that increasing the linker bulk and retaining the 10×His purification tag improved the diffraction resolution, likely by decreasing the number of possible vWa-domain orientations in the crystal. Additionally, it was discovered that some vWa-domain binding modes are correlated with scrambling of the 1TEL polymer orientation in crystals and an effective mitigation strategy for this pathology is presented.

1TEL↗
NASA NTRS1984

An experimental investigation of the effect of boundary layer refraction on the noise from a high-speed propeller

Models of supersonic propellers were previously tested for acoustics in the Lewis 8- by 6-Foot Wind Tunnel using pressure transducers mounted in the tunnel ceiling. The boundary layer on the tunnel ceiling is believed to refract some of the propeller noise away from the measurement transducers. Measurements were made on a plate installed in the wind tunnel which had a thinner boundary layer than the ceiling boundary layer. The plate was installed in two locations for comparison with tunnel ceiling noise data and with fuselage data taken on the NASA Dryden Jetstar airplane. Analysis of the data indicates that the refraction increases with: increasing boundary layer thickness; increasing free stream Mach number; increasing frequency; and decreasing sound radiation angle (toward the inlet axis). At aft radiation angles greater than about 100 deg there was little or no refraction. Comparisons with the airplane data indicated that not only is the boundary layer thickness important but also the shape of the velocity profile. Comparisons with an existing two-dimensional theory, using an idealized shear layer to approximate the boundary layer, showed that the theory and data had the same trends. Analysis of the data taken in the tunnel at two different distances from the propeller indicates a decay with distance in the wind tunnel at high Mach numbers but the decay at low Mach numbers is not as clear.

Dittmar, J. H.↗
NASA NTRS2005

Heart Pump Design for Cleveland Clinic Foundation

Through a Lewis CommTech Program project with the Cleveland Clinic Foundation, the NASA Lewis Research Center is playing a key role in the design and development of a permanently implantable, artificial heart pump assist device. Known as the Innovative Ventricular Assist System (IVAS), this device will take on the pumping role of the damaged left ventricle of the heart. The key part of the IVAS is a nonpulsatile (continuous flow) artificial heart pump with centrifugal impeller blades, driven by an electric motor. Lewis is part of an industry and academia team, led by the Ohio Aerospace Institute (OAI), that is working with the Cleveland Clinic Foundation to make IVAS a reality. This device has the potential to save tens of thousands of lives each year, since 80 percent of heart attack victims suffer irreversible damage to the left ventricle, the part of the heart that does most of the pumping. Impeller blade design codes and flow-modeling analytical codes will be used in the project. These codes were developed at Lewis for the aerospace industry but will be applicable to the IVAS design project. The analytical codes, which currently simulate the flow through the compressor and pump systems, will be used to simulate the flow within the blood pump in the artificial heart assist device. The Interdisciplinary Technology Office heads up Lewis' efforts in the IVAS project. With the aid of numerical modeling, the blood pump will address many design issues, including some fluid-dynamic design considerations that are unique to the properties of blood. Some of the issues that will be addressed in the design process include hemolysis, deposition, recirculation, pump efficiency, rotor thrust balance, and bearing lubrication. Optimum pumping system performance will be achieved by modeling all the interactions between the pump components. The interactions can be multidisciplinary and, therefore, are influenced not only by the fluid dynamics of adjacent components but also by thermal and structural effects. Lewis-developed flow-modeling codes to be used in the pump simulations will include a one-dimensional code and an incompressible three-dimensional Navier-Stokes flow code. These codes will analyze the prototype pump designed by the Cleveland Clinic Foundation. With an improved understanding of the flow phenomena within the prototype pump, design changes to improve the performance of the pump system can be verified by computer prior to fabrication in order to reduce risks. The use of Lewis flow modeling codes during the design and development process will improve pump system performance and reduce the number of prototypes built in the development phase. The first phase of the IVAS project is to fully develop the prototype in a laboratory environment that uses a water/glycerin mixture as the surrogate fluid to simulate blood. A later phase of the project will include testing in animals for final validation. Lewis will be involved in the IVAS project for 3 to 5 years.

Source record↗