Effect of plug and shroud geometry variables on plug-nozzle performance at transonic speeds
Plug and shroud geometry variables on plug nozzle performance at transonic speeds
Berrier, B. L.↗
SEARCH · Search NASA
Results for “Variable Speed”
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.
Effect of design variables, temperature gradients, and speed on life and reliability of a rotating disk
A generalized methodology to predict the fatigue life and reliability of a rotating disk such as used for aircraft engine turbines and compressors is advanced. The approach incorporates the computed life of elemental stress volumes to predict system life and reliability. Disk speed and thermal gradients as well as design varibles such as disk diameter and thickness and bolt hole size, number and location are considered.
Zaretsky, E. V.↗
Propeller rotation noise due to torque and thrust
Sound pressure of the first four harmonics of rotation from a full-scale two-blade propeller were measured and are compared with values calculated from theory. The comparison is made (1) for the space distribution with constant tip speed and (2) for fixed space angles with variable tip speed. A relation for rotation noise from an element of radius developed by Gutin is given showing the effect of number of blades on the rotation noise.
Deming, Arthur F↗
Stability Characteristics at Low Speed of a Variable-sweep Airplane Model Having a Partially Cambered Wing with Several Chord-extension Configurations
Explore the source record for details and available documents.
Becht, Robert E↗
Stepanyan's star - A new eclipsing cataclysmic variable
High-speed photometry of the nova-like variable Stepanyan's star shows a 3-hr 48-min orbital period marked by a 2.2-mag eclipse which spans orbital phases 0.91-0.09. The uneclipsed light is variable by typically 0.15 mag on time scales of minutes to seconds and shows no obvious modulation with orbital phase. Intermediate-band colors show an enhancement in Balmer continuum emission and in red light during the eclipse.
Horne, K.↗
Rolling stability derivatives of a variable- sweep tactical fighter model at subsonic and transonic speeds
Rolling stability derivatives of variable sweep tactical fighter aircraft model at subsonic and transonic speeds
VARIABLE SWEEP↗
Advanced Transonic Aerodynamic Technology
Supercritical airfoils and their applications to wings for various types of aircraft are studied. The various wings discussed were designed for a subsonic jet transport with increased speed, a variable sweep fighter with greater transonic maneuverability, a high subsonic speed STOL jet transport with improved low speed characteristics, and a subsonic jet transport with substantially improved aerodynamic efficiency. Results of wind tunnel and flight demonstration investigations are described. Also discussed are refinements of the transonic area rule concept and methods for reducing the aerodynamic interference between engine nacelles and wings at high subsonic speeds.
Whitcomb, R. T.↗
A study of light airplane pilot landing performance
The results of a total of 289 landings performed with a low-wing aircraft by a group of private pilots on long and short runways have been analyzed to determine the landing performance of these pilots. Both the long- and short-runway landings show significant variation from straight or uniformly curved trajectories, denoting considerable 'jockeying' on the part of the pilot during approach. The long-runway approach speeds were variable and higher than recommended. Considerable float followed by touchdown at speeds well above stall were noted. The short-runway landings were quite similar, except that approach speeds were slightly lower as a result of the use of two-thirds to full flaps, and touchdown occurred closer to the threshold.
Obryan, T. C.↗
The selective use of functional optical variables in the control of forward speed
Previous work on the perception and control of simulated vehicle speed has examined the contributions of optical flow rate (angular visual speed) and texture, or edge rate (frequency of passing terrain objects or markings) on the perception and control of forward speed. However, these studies have not examined the ability to selectively use edge rate or flow rate. The two studies presented here show that this ability is far greater for pilots than non-pilots, as would be expected since pilots must control vehicular speed over a variety of altitudes where flow rates change independently of forward speed. These studies also show that this ability to selectively use these variables is linked to the visual contextual information about the relative validity (linkage with speed) of the two variables. Subjective judgment data also indicated that awareness of altitude and ground texture density did not mediate ground speed awareness.
Johnson, Walter W.↗
Reaction wheels for kinetic energy storage
In contrast to all existing reaction wheel implementations, an order of magnitude increase in speed can be obtained efficiently if power to the actuators can be recovered. This allows a combined attitude control-energy storage system to be developed with structure mounted reaction wheels. The feasibility of combining reaction wheels with energy storage wwheels is demonstrated. The power required for control torques is a function of wheel speed but this energy is not dissipated; it is stored in the wheel. The I(2)R loss resulting from a given torque is shown to be constant, independent of the design speed of the motor. What remains, in order to efficiently use high speed wheels (essential for energy storage) for control purposes, is to reduce rotational losses to acceptable levels. Progress was made in permanent magnet motor design for high speed operation. Variable field motors offer more control flexibility and efficiency over a broader speed range.
Studer, P. A.↗
Variable frequency inverter for ac induction motors with torque, speed and braking control
A variable frequency inverter was designed for driving an ac induction motor which varies the frequency and voltage to the motor windings in response to varying torque requirements for the motor so that the applied voltage amplitude and frequency are of optimal value for any motor load and speed requirement. The slip frequency of the motor is caused to vary proportionally to the torque and feedback is provided so that the most efficient operating voltage is applied to the motor. Winding current surge is limited and a controlled negative slip causes motor braking and return of load energy to a dc power source.
Nola, F. J.↗
The influence of subsonic mission segments on the use of variable-sweep wings for high speed civil transport configurations
A Mach-3.0, 250-passenger, 6500-n. mi. range SST configuration's alternative use of fixed-planform or variable-sweep wings is presently evaluated, with a view to effects on aerodynamics, mission performance, and sizing. After preliminary design, the fixed and variable-wing configurations were resized to perform missions incorporating subsonic cruise segments of as much as 4000 n. mi.; the effect of subsonic segment length on design gross weight and block time was then ascertained. Due to the reduced supersonic efficiency of the variable-sweep aircraft, over one-half of the 6500-n. mi. mission would have to be flown subsonically for its sizing to reach a lower ramp weight than that of its fixed-geometry counterpart.
Martin, Glenn L.↗
The earth resources technology satellite - Photographic facility quality control program
A detailed description is given of the quality control program used in the photographic laboratory of the NASA-ERTS Ground Data Handling System. The product response variables measured include tone reproduction, resolution, and low spatial frequency noise. In addition to product response variables, certain performance parameters of the laboratory printers and processors are frequently measured in order to produce consistent duplications of archival photography. A description is given of the operation and use of a densitometer/computer interface which is used to calculate three tone reproduction response variables - film speed, average gradient, and base plus fog density. This procedure eliminates the need for any hand plotting of D log E curves to manually determine response variables.
Shaffer, R. M.↗
Conceptual Design Trade Studies for Acoustic Predictions of the NASA UAM Tiltrotor Reference Vehicle
A toolchain of low-and mid-fidelity tools is applied to NASA’s Urban Air Mobility tiltrotor reference vehicle to quantify trades in sizing, performance, and noise at the conceptual design level. The process includes conceptual sizing, comprehensive analysis, and acoustic analysis to design and analyze versions of the concept tiltrotor with differing design variables. Rotor tip speed is the primary design variable studied, with blade twist, blade taper, and blade number also considered. The noise metrics used are the FAA/EASA certification Effective Perceived Noise Levels for takeoff, flyover, and approach. Certification condition noise is calculated for all conditions in both conversion and airplane flight modes, with airplane mode flight resulting in noise 10-25EPNdB quieter than conversion mode and tip speed variation providing noise reduction up to 9EPNdB.
Acoustic↗
Ceramics for the advanced automotive gas turbine engine: A look at a single shaft design
The results of a preliminary analysis of a single shaft regenerative design with a single stage radial turbine are presented to show the fuel economy that can be achieved at high turbine inlet temperatures, with this particular advanced design, if the turbine tip speed and regenerator inlet temperature are not limited. The engine size was 100 hp for application to a 3500 lb auto. The fuel economy was analyzed by coupling the engine to the auto through a continuously variable speed-ratio transmission and operating the system at constant turbine inlet temperature over the Composite Driving Cycle. The fuel was gasoline and the analysis was for a 85 F day. With a turbine inlet temperature of 2500 F the fuel economy was 26.2 mpg, an improvement of 18 percent over that of 22.3 mpg with a turbine inlet temperature of 1900 F. The turbine tip speed needed for best economy with the 2500 F engine was 2530 ft/sec. The regenerator temperature was approximately 2200 F at idle. Disk stresses were estimated for one single stage radial turbine and two two-stage radial-axial turbines and compared with maximum allowable stress curves estimated for a current ceramic material. Results show a need for higher Weibull Modulus, higher strength ceramics.
Nosek, S. M.↗
Effect of a part span variable inlet guide vane on TF34 fan performance
Experimental aerodynamic and performance data were obtained from a TF34 engine. Part span variable inlet guide vanes mounted in front of the fan on the TF34 engine were tested to demonstrate the feasibility of modulating air flow and thrust for vertical takeoff aircraft systems. The fan was mapped to stall for a range of speeds and variable inlet guide were settings. Modulated fan tip performance and unmodulated hub performance were evaluated with a without an extended fan bypass splitter. The effect of a crosswind distortion screen on performance was also evaluated.
Alvarez, J.↗
Wind-tunnel Studies at Subsonic and Transonic Speeds of a Multiple-mission Variable-wing-sweep Airplane Configuration
Wind tunnel studies at supersonic and transonic speeds to determine aerodynamic characteristics of variable sweep wing aircraft - configuration
TRANSONIC WIND TUNNEL↗
Concepts for Multi-Speed Rotorcraft Drive System - Status of Design and Testing at NASA GRC
In several studies and on-going developments for advanced rotorcraft, the need for variable multi-speed capable rotors has been raised. Speed changes of up to 50 have been proposed for future rotorcraft to improve vehicle performance. A rotor speed change during operation not only requires a rotor that can perform effectively over the operating speedload range, but also requires a propulsion system possessing these same capabilities. A study was completed investigating possible drive system arrangements that can accommodate up to a 50 speed change. Key drivers were identified from which simplicity and weight were judged as central. This paper presents the current status of two gear train concepts coupled with the first of two clutch types developed and tested thus far with focus on design lessons learned and areas requiring development. Also, a third concept is presented, a dual input planetary differential as leveraged from a simple planetary with fixed carrier.
transmission↗