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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Dynamic loading on parallel shaft gears

A computer-based analysis of the dynamic effects of spur gear systems is presented. The method of analysis with its associated computer code is capable of determining the dynamic response of spur gear systems having involute tooth profiles and standard contact ratios. Various parameters affecting the system dynamic behavior are examined. Numerical results of the analysis are compared with semi-empirical formulae, AGMA (American Gear Manufacturers Association) formulae, and experimental data. A close correlation with the experimental data is obtained.

Lin, H. H. (edward)↗
NASA NTRS1987

Active-Control Bearings for Rotor Shafts

Vibrations suppressed by feedback control. Flexural forced vibrations or self-excited vibrations of rotating system suppressed by active elements. Instead of dissipating vibration forces through damped supports, active elements apply forces, through bearing housing, that cancel vibration displacements. Bearing systems incorporating such devices appropriately named active-control bearings. Active-controlbearing systems effective not only for imbalance forces but also for unstable or external forces transmitted from foundation. Damping ratios of system easily changed by modifying state-feedback control system.

Nonami, K.↗
NASA NTRS1987

Noncontacting Measurement of Shaft Angle

Fiber-optic transducer offers several advantages over mechanical linkages. Angular position of rotary valve measured by pair of optical-fiber deflectometers. Measurement device sensitive, immune to electromagnetic interference, and does not wear out since fibers do not make contact with valve. Device more rugged than linear or rotary variable-differential transformers it replaces.

Barkhoudarian, S.↗
NASA NTRS1987

Effect of shaft rotation on the incompressible flow in a labyrinth seal

The incompressible flow in a labyrinth seal at low leakage rates was computationally and experimentally investigated over a wide range of seal rotation rates. QUICK differencing was employed in the finite difference code to reduce the effects of false diffusion. The use of measured inlet boundary conditions for the axial and swirl velocity components and for the turbulent kinetic energy resulted in good agreement between velocity predictions and hot-film measurements. It was found that when the rotation rate is increased beyond a certain point, a second recirculation zone forms inside the seal cavity, altering the flow field in the cavity and resulting in a substantial increase in the pressure drop across it.

Demko, J. A.↗
NASA NTRS1989

Parallel processing of a rotating shaft simulation

A FORTRAN program describing the vibration modes of a rotor-bearing system is analyzed for parellelism in this simulation using a Pascal-like structured language. Potential vector operations are also identified. A critical path through the simulation is identified and used in conjunction with somewhat fictitious processor characteristics to determine the time to calculate the problem on a parallel processing system having those characteristics. A parallel processing overhead time is included as a parameter for proper evaluation of the gain over serial calculation. The serial calculation time is determined for the same fictitious system. An improvement of up to 640 percent is possible depending on the value of the overhead time. Based on the analysis, certain conclusions are drawn pertaining to the development needs of parallel processing technology, and to the specification of parallel processing systems to meet computational needs.

Arpasi, Dale J.↗
NASA NTRS1991

Actively controlled shaft seals for aerospace applications

The main objective is to determine the feasibility of utilizing controllable mechanical seals for aerospace applications. A potential application was selected as a demonstration case: the buffer gas seal in a LOX (liquid oxygen) turbopump. Currently, floating ring seals are used in this application. Their replacement with controllable mechanical seals would result in substantially reduced leakage rates. This would reduce the required amount of stored buffer gas, and therefore increase the vehicle payload. For such an application, a suitable controllable mechanical seal was designed and analyzed.

Salant, Richard F.↗
NASA NTRS1991

Actively controlled shaft seals for aerospace applications

Actively controlled mechanical seals have recently been developed for industrial use. This study investigates the feasibility of using such seals for aerospace applications. In a noncontacting mechanical seal, the film thickness depends on the geometry of the seal interface. The amount of coning, which is a measure of the radial convergence or divergence of the seal interface, has a primary effect on the film thickness. Active control of the film thickness is established by controlling the coning with a piezoelectric material. A mathematical model has been formulated to predict the performance of an actively controlled mechanical seal.

Salant, Richard F.↗
NASA NTRS1949

Performance of J33 turbojet engine with shaft-power extraction III : turbine performance

The performance of the turbine component of a J33 turbojet engine was determined over a range of turbine speeds from 8000 to 11,500 rpm.Turbine-inlet temperature was varied from the minimum required to drive the compressor to a maximum of approximately 2000 degrees R at each of several intermediate turbine speeds. Data are presented that show the horsepower developed by the turbine per pound of gas flow. The relation between turbine-inlet stagnation pressure, turbine-outlet stagnation pressure, and turbine-outlet static pressure was established. The turbine-weight-flow parameter varied from 39.2 to 43.6. The maximum turbine efficiency measured was 0.86 at a pressure ratio of 3.5 and a ratio of blade speed to theoretical nozzle velocity of 0.39. A generalized performance map of the turbine-horsepower parameter plotted against the turbine-speed parameter indicated that the best turbine efficiency is obtained when the turbine power is 10 percent greater than the compressor horsepower. The variation of efficiency with the ratio of blade speed to nozzle velocity indicated that the turbine operates at a speed above that for maximum efficiency when the engine is operated normally with the 19-inch-diameter jet nozzle.

Huppert, M C↗
NASA NTRS1942

Propeller blade stresses caused by periodic displacement of the propeller shaft

The present report deals with different vibration stresses of the propeller and their removal by an elastic coupling of propeller and engine. A method is described for protecting the propeller from unstable oscillations and herewith from the thus excited alternating gyroscopic moments. The respective vibration equations are set down and the amount of elasticity required is deduced.

Meyer, J↗
NASA NTRS1993

Actively controlled shaft seals for aerospace applications

An electronically controlled mechanical seal for use as the purge gas seal in a liquid oxygen turbo pump has been fabricated and tested under transient operating conditions. The thickness of the lubricating film is controlled by adjusting the coning of the carbon face. This is accomplished by applying a voltage to a piezoelectric actuator to which the carbon face is bonded. The seal has been operated with a closed-loop control system that utilizes either the leakage rate or the seal face temperature as the feedback. Both speed and pressure transients have been imposed on the seal. The transient tests have demonstrated that the seal is capable of maintaining low leakage rates while limiting the face temperatures.

Salant, Richard F.↗