Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “AXIAL RATIO”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Importance of 3-D S{sub N} depletion in non-proliferation using BSOLVE

We present a single Pressurized Water Reactor (PWR) 3-D fuel rod design for depletion analysis using BSOLVE, our newly developed Runge-Kutta-Fehlberg based depletion code. BSOLVE is coupled with the deterministic 3-D S{sub N} particle transport code, PENTRAN, applied here with a 4-neutron energy group comparison to Continuous Energy (C/E) SERPENT2 Monte Carlo results. Differences are expected, as PENTRAN+BSOLVE retains full (multi-group) energy information for reactions, nuclide specific fission contributions, and energy dependent fission yields, using the latest available ENDF-BVIII data, important to retain accurate burned fuel inventories; SERPENT2 collapses burnup reactions to a single energy value. For depletion times up to ∼ 700 days and typical PWR power densities, relative differences between multigroup 3-D S{sub N} with full energy data and Monte Carlo one group burnup for trans-uranium nuclide concentrations and fission products are up to ∼20%. System eigenvalues are consistent, but with differences early and late in the cycle attributed to multigroup vs. C/E Monte Carlo cross sections. This work highlights the importance of low variance transport driven burnup for non-proliferation concerns, since plutonium quality varies significantly along axial lengths, and is more challenging to converge using Monte Carlo; details of depletion steps with spatial/zone dependent plutonium quality are provided. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1966

Transonic aerodynamic investigation of tension shell and blunted 100 deg conical shapes for unmanned entry vehicles

An experimental investigation of a spherically blunted 100° cone and two tension shell configurations with varying nose-bluntness ratios for use in unmanned entry into low -density planetary atmospheres has been conducted by the National Aeronautics and Space Administration at Mach numbers from 0.30 to 1.20 and at angles of attack from approximately O° to 40°. The results show that the models were longitudinally stable, with centers of pressure located rearward of the base at all test conditions. The tension shell configurations exhibited substantially higher axial-force coefficients than the 100° cone although the variation of axial-force coefficient with Mach number at zero angle of attack was similar for all configurations. An increase in tension shell body length resulted in a reduction of the axial-force coefficients and a more forward center-of-pressure location. Variation in nose bluntness had no significant effect on the longitudinal aerodynamic characteristics of the tension shell configurations.

TRANSONIC SPEED↗
NASA NTRS1986

Component testing of a ground based gas turbine steam cooled rich-burn primary zone combustor for emissions control of nitrogeneous fuels

This effort summarizes the work performed on a steam cooled, rich-burn primary zone, variable geometry combustor designed for combustion of nitrogeneous fuels such as heavy oils or synthetic crude oils. The steam cooling was employed to determine its feasibility and assess its usefulness as part of a ground based gas turbine bottoming cycle. Variable combustor geometry was employed to demonstrate its ability to control primary and secondary zone equivalence ratios and overall pressure drop. Both concepts proved to be highly successful in achieving their desired objectives. The steam cooling reduced peak liner temperatures to less than 800 K. This low temperature offers the potential of both long life and reduced use of strategic materials for liner fabrication. These degrees of variable geometry were successfully employed to control air flow distribution within the combustor. A variable blade angle axial flow air swirler was used to control primary zone air flow, while the secondary and tertiary zone air flows were controlled by rotating bands which regulated air flow to the secondary zone quench holes and the dilutions holes respectively.

Schultz, D. F.↗
NASA NTRS1953

Altitude Starting Characteristics of an Afterburner with Autoignition and Hot-streak Ignition

An investigation was conducted in an altitude test chamber at the NACA Lewis Laboratory to determine the altitude starting characteristics of an afterburner with autoignition and with hot-streak ignition. Transient afterburner ignition data were obtained over a range of altitudes from 30,000 to 50,000 feet at a flight Mach number of 0.60. Afterburner ignition with a torch igniter located axially at approximately the midpoint of the combustion chamber was possible over the entire range, but ignition ignition with a torch igniter located in the transition section 1 5/8 inches upstream of the turbine stators proved unsatisfactory at an altitude of 50,000 feet due to the inability to obtain flame through the turbine. Increasing the afterburner-inlet total pressure at a constant afterburner fuel-air ratio decreased the afterburner ignition time. Hot-streak ignition was possible within 2 seconds after the time required to obtain the preset, normal afterburner fuel pressure, whereas autoignition required 4 to 7 seconds for the range of altitudes investigated. Following the ignition there was a period of oscillatory operation existing in the engine-afterburner before steady-state operation was attained. The time required for steady-state stable operation decreased as afterburner inlet total pressure increased. The duration of oscillations also decreased with hot-streak ignition because the fuel-air mixture was ignited before a large volume of combustible mixture was accumulated in the afterburner.

Engines, Control - Turbojet↗
NASA NTRS1994

Magnetocentrifugally driven flows from young stars and disks. 2: Formulation of the dynamical problem

We formulate the dynamical problem of a cool wind centrifugally driven from the magnetic interface of a young star and an adjoining Keplerian disk. We examine the situation for mildly accreting T Tauri stars that rotate slowly as well as rapidly accreting protostars that rotate near break-up. In both cases a wind can be driven from a small X-region just outside the stellar magnetopause, where the field lines assume an open geometry and are rooted to material that rotates at an angular speed equal both to the local Keplerian value and to the stellar angular speed. Assuming axial symmetry for the ideal magnetohydrodynamic flow, which requires us to postpone asking how the (lightly ionized) gas is loaded onto field lines, we can formally integrate all the governing equations analytically except for a partial equation that describes how streamlines spread in the meridional plane. Apart from the difficulty of dealing with PDEs of mixed type, finding the functional forms of the conserved quantities along streamlines - the ratio beta of magnetic field to mass flux, the specific energy H of the fluid in the rotating frame, and the total specific angular momentum J carried in the matter and the field - constitutes a standard difficulty in this kind of (Grad-Shafranov) formalism. Fortunately, because the ratio of the thermal speed of the mass-loss regions to the Keplerian speed of rotation of the interface constitutes a small parameter epsilon, we can attack the overall problem by the method of matched asymptotic expansions. This procedure leads to a natural and systematic technique for obtaining the relevant functional dependences of beta, H, and J. Moreover, we are able to solve analytically for the properties of the flow emergent from the small transsonic region driven by gas pressure without having to specify the detailed form of any of the conserved functions, beta, H, and J. This analytical solution provides inner boundary conditions for the numerical computation in a companion paper by Najita & Shu of the larger region where the main acceleration to terminal speeds occurs.

Shu, Frank H.↗
DOE OSTI2023

Electric field gradients at rubidium sites in rubidium uranyl nitrate and quadrupole moments of 85 Rb and 87 Rb

The electronic structure along the axial direction of the uranyl ion in rubidium uranyl nitrate (RbUO 2 (NO 3 ) 3 ) has been studied by nuclear quadrupole resonance and nuclear magnetic resonance measurements of 85 Rb and 87 Rb quadrupole couplings. Here, the parameter of interest in these experiments is the electric field gradient at the Rb sites, which may be compared with values com- puted by various theoretical approaches. From this analysis an accurate ratio of the quadrupole moments of 85 Rb and 87 Rb has also been obtained.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1981

Reciprocating piston pump system with screw drive

A pump system of the reciprocating piston type is described, which facilitates direct motor drive and cylinder sealing. A threaded middle potion of the piston is engaged by a nut connected to rotate with the rotor of an electric motor, in a manner that minimizes loading on the rotor by the use of a coupling that transmits torque to the nut but permits it to shift axially and radially with respect to the rotor. The nut has a threaded hydrostatic bearing for engaging the threaded piston portion, with an oil-carrying groove in the nut being interrupted. A fluid emitting seal located at the entrance to each cylinder, can serve to center the piston within the cylinder, wash the piston, and to aid in sealing. The piston can have a long stroke to diameter ratio to minimize reciprocations and wear on valves at high pressures. The voltage applied to the motor can be reversed prior to the piston reaching the end of its stroke, to permit pressure on the piston to aid in reversing the motor.

Perkins, Gerald S.↗
NASA NTRS1984

Residual stresses in cross-ply composite tubes

The residual thermal stresses in 4-layer cross-ply tubes are studied. The tubes considered has a small radius to wall-thickness ratios and so elasticity solutions were used. The residual thermal stress problem was considered to be axisymmetric and three elasticity solutions were derived and the results compared with the results using classical lamination theory. The comparison illustrates the limitations of classical lamination theory. The three elasticity solutions derived were: plane stress, plane strain, and generalized plane strain, the latter being the most realistic. Residual stresses in both the hoop and axial direction is significant. Stacking arrangement effects the residual stress to some extent, as do the material properties of the individual lamina. The benefits of hybrid construction are briefly discussed.

Cohen, D.↗
NASA NTRS1948

Surface-pressure Distributions on a Systematic Group of NACA 1-series Cowlings with and Without Spinners

A method for calculating the flow fields of axially symmetric bodies from their pressure distributions is reported in NACA RM No. L8I17. In order to facilitate application of this method to the important case of the cowling-spinner combination, for use in the design of propellers, the present paper presents static-pressure distributions on the tops of 79 high-critical-speed NACA 1-series cowling-spinner combinations over wide ranges of inlet-velocity ratio at angles of attack of 0 degrees, 2 degrees, 4 degrees, and 6 degrees. Static-pressure distributions around the nose sections of several cowlings are given in greater detail to aid in estimating the pressures near the stagnation points and to show the effect of changes in the internal lip shape. The effects of the operation of a typical propeller on the surface pressures on the cowling are shown for one configuration. The pressure distributions over the nine NACA 1-series nose inlets used as the basic components of these combinations are also presented ro supplement the existing open-nose-cowling data of NACA ACR No. L5F30a which are applicable to the case of the rotating cowling.

Boswinkle, Robert W JR↗
NASA NTRS1948

Altitude-wind-tunnel investigation of Westinghouse 19B-2, 19B-8, and 19XB-1 jet-propulsion engines III : performance and windmilling drag characteristics

The performance characteristics of the 19B-8 and 19XB-1 turbojet engines and the windmilling drag characteristics of the 19B-8 engine were determined in the NACA Cleveland altitude wind tunnel. The 19B engine is one of the earliest experimental Westinghouse axial-flow engines. The 19XB-1 engine is an experimental prototype of the Westinghouse 19XB series, having a rated thrust of 1400 pounds. Improvements in performance and operational characteristics have resulted in the 19XB-2B engine with a rated thrust of 1600 pounds. The investigations were conducted on the 19B-8 engine at simulated altitudes from 5000 to 25,000 feet with various free-stream ram-pressure ratios and on the 19XB-1 engine at simulated altitudes from 5000 to 30,000 feet with approximately static free-stream conditions. Data for these two engines are presented to show the effect of altitude, free-stream ram-pressure ratio, and tail-pipe-nozzle area on engine performance.

Fleming, William A↗
NASA NTRS1973

Design and experimental performance of short curved wall diffusers with axial symmetry utilizing slot suction

The feasibility of designing short curved wall axially symmetrical subsonic diffusers utilizing suction through slots in the diffuser walls to prevent flow separation was investigated. A potential flow analysis was made, and a digital computer program was written for determining the diffuser wall contour for prescribed boundary conditions. The flow field included branch flow so that the suction slot geometry could be a part of the diffuser design. One bell shaped diffuser and three annular diffusers with area ratios of either 2.5:1 or 3:1 were designed, fabricated, and tested. Minimum suction requirements of metastable operation ranged from 6.3 percent to 12 percent when operating with inlet air velocities in the 1000 to 250 ft/sec (30 to 76 m/sec) range. For stable operation suction rates from 10 percent to 22 percent were required. In all cases the diffuser effectiveness was above 95 percent based on the conventional definition, and from 81 percent to 94 percent when the suction loss was accounted for. The exit velocity profiles were virtually flat with no more than + or - 9% variation over 95 percent of the exit area when operated with sufficient suction to prevent flow separation.

Yang, T.↗
NASA NTRS1990

Nature of convection-stabilized dc arcs in dual-flow nozzle geometry. I - The cold flow field and dc arc characteristics. II - Optical diagnostics and theory

Steady-state low-current air arcs in a dual-flow nozzle system are studied experimentally. The cold flow field with no arc is investigated using a 12.7-mm diameter dual-flow nozzle in a steady-flow facility. Mach number and mass flux distributions are determined for various nozzle-pressure ratios and nozzle-gap spacing. It is found that the shock waves in the converging-diverging nozzles result in a decrease in overal resistance by about 15 percent. Also, Schlieren and differential interferometry techniques are used to visualize the density gradients within the arc plasma and thermal mantle. Both optical techniques reveal a laminar arc structure for a reservoir pressure of 1 atm at various current levels. Experimentally determined axial static pressure and cold-flow mass flux rate distributions and a channel-flow model with constant arc temperatre are used to solve the energy integral for the arc radius as a function of axial distance. The arc electric field strength, voltage, resistance, and power are determined with Ohm's law and the total heat transfer is related to arc power.

Serbetci, Ilter↗
NASA NTRS1991

Measurement of the performance of a spiral wound polyimide regenerator in a pulse tube refrigerator

A regenerator for use in a pulse tube refrigerator has been constructed from a polyimide (polypyromellitimide or PPMI) whose small ratio of thermal conductivity to heat capacity make it a good candidate for a regenerator material in cryocoolers. The regenerator was fabricated using 25 micron thick photoresist strips bonded to a 50 micron thick sheet of PPMI. This composite sheet was wound in jelly-roll fashion around a mandrel and inserted into the regenerator housing. The photoresist strips, formed using a photolithographic technique, provided a 25 micron spacing for the axial flow of gas between each layer of PPMI. Ineffectiveness results are presented for this material under actual operating conditions in a pulse tube refrigerator and compared with a numerical model. The numerical model indicated that a polyimide regenerator would perform much better than one constructed of stainless steel screen, but the experimental results showed the opposite behavior. Measured values for the ineffectiveness were 0.003 for the stainless steel screen and 0.017 for the polyimide.

Rawlins, Wayne↗
NASA NTRS1961

Effects of Sting-Support Diameter on the Base Pressures of an Elliptic Cone at Mach Numbers from 0.60 to 1.40

Measurements were made to determine the effects of sting-support diameter on the base pressures of an elliptic cone with ratio of cross-section thickness to width of 1/3 and a plan-form, semi-apex angle of 15 deg. The investigation was made for model angles of attack from -2 deg to +20 deg at Mach numbers from 0.60 to 1.40, and for a constant Reynolds number of 1.4 million, based on the length of the model. The results indicated that the sting interference decreased the base axial-force coefficients by substantial amounts up to a maximum of about one-third the value of the coefficient for no sting interference. There was no practical diameter of the sting for which the effects of the sting on the base pressures would be negligible throughout the Mach number and angle-of-attack ranges of the investigation.

Stivers, Louis S., Jr.↗
DOE OSTI2024

Magneto-Stokes flow in a shallow free-surface annulus

In this study, we analyse ‘magneto-Stokes’ flow, a fundamental magnetohydrodynamic (MHD) flow that shares the cylindrical-annular geometry of the Taylor–Couette cell but uses applied electromagnetic forces to circulate a free-surface layer of electrolyte at low Reynolds numbers. The first complete, analytical solution for time-dependent magneto-Stokes flow is presented and validated with coupled laboratory and numerical experiments. Three regimes are distinguished (shallow-layer, transitional and deep-layer flow regimes), and their influence on the efficiency of microscale mixing is clarified. The solution in the shallow-layer limit belongs to a newly identified class of MHD potential flows, and thus induces mixing without the aid of axial vorticity. We show that these shallow-layer magneto-Stokes flows can still augment mixing in distinct Taylor dispersion and advection-dominated mixing regimes. The existence of enhanced mixing across all three distinguished flow regimes is predicted by asymptotic scaling laws and supported by three-dimensional numerical simulations. Mixing enhancement is initiated with the least electromagnetic forcing in channels with order-unity depth-to-gap-width ratios. If the strength of the electromagnetic forcing is not a constraint, then shallow-layer flows can still yield the shortest mixing times in the advection-dominated limit. Our robust description of momentum evolution and mixing of passive tracers makes the annular magneto-Stokes system fit for use as an MHD reference flow.

58 GEOSCIENCES↗
NASA NTRS1976

Measurements of acoustic responses of gaseous propellant injectors

Results are presented for an investigation intended to provide experimental data that can quantitatively describe the way in which various coaxial injector designs affect the stability of gaseous propellant rocket motors. The response factors of configurations that simulate the flow conditions in a gaseous-fuel injector element and a gaseous-oxidizer injector element are measured by using a modified impedance-tube technique and under cold-flow conditions simulating those observed in rocket motors with axial instability. The measured injector response factor data are presented and discussed. It is shown that there is reasonable agreement between the measured injector response factors and those predicted by the Feiler and Heidmann model (1967), and that the orifice length can be varied to shift the resonant frequency of the injector without any change in the magnitude of the response factor at resonance. A change in the injector open-area ratio is found to have a significant effect on the characteristics of the injector response factor.

Janardan, B. A.↗
NASA NTRS2005

Performance of a Checkerboard Liner With Uncertain Impedances

The current fleet of large commercial aircraft has successfully achieved FAA noise certifications because of, in part, the successful application of uniform passive duct liner treatments to control engine system noise. One goal of NASA's engine system noise reduction program is to develop technologies to improve the sound absorbing properties of duct liner treatments so that they remain effective in modern turbo fan engines. One such technology being studied is checkerboard or periodic axially and circumferentially segmented liners. A preliminary assessment of the potential of this technology was conducted by applying uncertainties associated with manufacturing, installation, source structure, and tonal frequency to a liner developed using deterministic design methods and generating a measure of improvement with respect to a uniform liner subjected to the same uncertainties. Deterministic design and analysis of the candidate checkerboard liner showed that it obtains a 1.5 dB per duct aspect ratio improvement in liner attenuation over a similarly designed uniform liner. When uncertainties in liner impedances, source structure, and frequency are considered, the performance of the checkerboard liner drops off dramatically. The final results of this paper show that the candidate checkerboard liner has a less than 25 percent chance of outperforming the uniform liner when moderate levels of uncertainty are considered. It is important to note that this study did not include the effects of mean flow on liner performance and, more important to note, that as a gradient based optimization process was used to design the checkerboard liner, it is almost certain that a global optimal design was not found for the candidate checkerboard liner. Had it been possible to find a better deterministically performing checkerboard liner, the probability that this candidate liner would outperform the uniform liner would certainly have been higher.

Robinson, J. H.↗
NASA NTRS2017

A Comparison of Combustion Dynamics for Multiple 7-Point Lean Direct Injection Combustor Configurations

The combustion dynamics of multiple 7-point lean direct injection (LDI) combustor configurations are compared. LDI is a fuel-lean combustor concept for aero gas turbine engines in which multiple small fuel-air mixers replace one traditionally-sized fuel-air mixer. This 7-point LDI configuration has a circular cross section, with a center (pilot) fuel-air mixer surrounded by six outer (main) fuel-air mixers. Each fuel-air mixer consists of an axial air swirler followed by a converging-diverging venturi. A simplex fuel injector is inserted through the center of the air swirler, with the fuel injector tip located near the venturi throat. All 7 fuel-air mixers are identical except for the swirler blade angle, which varies with the configuration. Testing was done in a 5-atm flame tube with inlet air temperatures from 600 to 800 F and equivalence ratios from 0.4 to 0.7. Combustion dynamics were measured using a cooled PCB pressure transducer flush-mounted in the wall of the combustor test section.

lean direct injection↗