Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “annular”

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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Three dimensional aerodynamics of an annular cascade in a non-uniform inlet flow

Three-dimensional viscous and inviscid numerical analyses are currently being developed to predict the complex flow through turbomachine blade passages. To be of value to the designer, these numerical solutions must be evaluated and subsequent refinements directed by correlating predicted flow fields with data obtained from experiments which model the fundamental three-dimensional flow phenomena inherent in blade rows. This paper describes a series of experiments to provide such data. In particular, the effect of a potential and a rotational inlet flow field on the detailed three-dimensional aerodynamic performance of an extensively instrumented cambered airfoil cascade has been determined at two levels of aerodynamic loading. Data presented quantify the pressure and suction surface static pressure chordwise distributions on the hub, mean, and tip streamlines; the velocity distribution in the cascade aft-passage region; and the cascade exit region flow field. Appropriate data are correlated with predictions.

Manwaring, S. R.↗
NASA NTRS1986

Equations for Annular-Heat-Transfer Coefficients

Tables of coefficients converted to algebraic expressions. Plot of Equation for Nusselt number agrees closely with points from tabulated data. Equation for Nusselt number and those for coefficients A and B obtained by regression analysis of data. Other plots also show close agreement for radius of 0.1 and 0.2. In equation form, coefficients incorporated into mathematical models more readily than as tabular data. Equations simplify design and analysis of heat exchangers.

Yao, B.↗
NASA NTRS1988

Modelling and Control of an Annular Momentum Control Device

The results of a modelling and control study for an advanced momentum storage device supported on magnetic bearings are documented. The control challenge posed by this device lies in its dynamics being such a strong function of flywheel rotational speed. At high rotational speed, this can lead to open loop instabilities, resulting in requirements for minimum and maximum control bandwidths and gains for the stabilizing controllers. Using recently developed analysis tools for systems described by complex coefficient differential equations, the closed properties of the controllers were analyzed and stability properties established. Various feedback controllers are investigated and discussed. Both translational and angular dynamics compensators are developed, and measures of system stability and robustness to plant and operational speed variations are presented.

Downer, James R.↗
NASA NTRS1987

Imaging performance of annular apertures. VI - Limitations by optical surface deviations

The performance of optical systems is limited by imperfect optical surfaces that degrade the images below the level set by wave theoretical limits. The central irradiance functions are derived for slit and circular apertures with five distributions of wavefront errors and for a range of maximal wavefront deviations. For practical frequency of occurrence distributions of wavefront deviations, the point spread and the image energy integral functions are determined. Practical performances of optical systems are derived and performance limits discussed.

Tschunko, Hubert F. A.↗
NASA NTRS1988

A new linearized theory of laminar film condensation of two phase annular flow in a capillary pumped loop

Future large space based facilities, such as Space Station, will require energy management systems capable of transporting tens of kilowatts of heat over a hundred meters or more. This represents better than an order of magnitude improvement over current technology. Two-phase thermal systems are currently being developed to meet this challenge. Condensation heat transfer plays a very important role in this system. The present study attempts an analytic solution to the set of linearized partial differential equations. The axial velocity and temperature functions were found to be Bessel functions which have oscillatory behavior. This result agrees qualitatively with the experimental evidence from tests at both NASA Goddard Space Flight Center and elsewhere.

Hsu, Y. K.↗
NASA NTRS1989

Numerical studies of convective heat transfer in an inclined semi-annular enclosure

Natural convection heat transfer in a two-dimensional differentially heated semiannular enclosure is studied. The enclosure is isothermally heated and cooled at the inner and outer walls, respectively. A commercial software based on the SIMPLER algorithm was used to simulate the velocity and temperature profiles. Various parameters that affect the momentum and heat transfer processes were examined. These parameters include the Rayleigh number, Prandtl number, radius ratio, and the angle of inclination. A flow regime extending from conduction-dominated to convection-dominated flow was examined. The computed results of heat transfer are presented as a function of flow parameter and geometric factors. It is found that the heat transfer rate attains a minimum when the enclosure is tilted about +50 deg with respect to the gravitational direction.

Wang, L.-W.↗
NASA NTRS1993

Hotfire testing of a SSME HPOTP with an annular hydrostatic bearing

A new fluid film bearing package has been tested in the SSME High Pressure Oxygen Turbopump (HPOTP). This fluid film element functions as both the pump end bearing and the preburner pump rear wear ring seal. Most important, it replaces a duplex ball bearing package which has been the primary life limiting component in the turbopump. The design and predicted performance of the turbopump are reviewed. Results are presented for measured pump and bearing performance. The most significant results were obtained from proximity probes located in the bearing bore which revealed large subsynchronous precession at 10 percent of shaft speed during engine start which subsided prior to mainstage power levels and reappeared during engine shutdown at equivalent power levels below 65 percent of nominal. This phenomenon has been attributed to rotating stall in the diffuser. The proximity probes also revealed the location of the bearing in the bore for different operating speeds. Pump vibration characteristics were improved as compared to pumps tested with ball bearings. After seven starts and more than 700 seconds of testing, the pump showed no signs of performance degradation.

Nolan, Steven A.↗