Results for “PROPELLER” — Page 19

NASA NTRS1984

Noise generated by a propeller in a wake

Propeller performance and noise were measured on two model scale propellers operating in an anechoic flow environment with and without a wake. Wake thickness of one and three propeller chords were generated by an airfoil which spanned the full diameter of the propeller. Noise measurements were made in the relative near field of the propeller at three streamwise and three azimuthal positions. The data show that as much as 10 dB increase in the OASPL results when a wake is introduced into an operating propeller. Performance data are also presented for completeness.

Block, P. J. W.↗

NASA NTRS1981

Acoustic flight testing of advanced design propellers on a JetStar aircraft

Advanced turboprop-powered aircraft have the potential to reduce fuel consumption by 15 to 30 percent as compared with an equivalent technology turbofan-powered aircraft. An important obstacle to the use of advanced design propellers is the cabin noise generated at Mach numbers up to .8 and at altitudes up to 35,000 feet. As part of the NASA Aircraft Energy Efficiency Program, the near-field acoustic characteristics on a series of advanced design propellers are investigated. Currently, Dryden Flight Research Center is flight testing a series of propellers on a JetStar airplane. The propellers used in the flight test were previously tested in wind tunnels at the Lewis Research Center. Data are presented showing the narrow band spectra, acoustic wave form, and acoustic contours on the fuselage surface. Additional flights with the SR-3 propeller and other advanced propellers are planned in the future.

Lasagna, P.↗

NASA NTRS1985

Coated oxidizers for combustion stability in solid-propellant rockets

Experiments are conducted in a laboratory-scale (6.25-cm diameter) end-burning rocket motor with state-of-the-art, ammonium perchlorate hydroxy-terminated polybutadiene (HTPB), nonmetallized propellants. The concept of tailoring the stability characteristics with a small amount (less than 1 percent by weight) of COATING on the oxidizer is explored. The thermal degradation characteristics of the coat chemical are deduced through theoretical arguments on thermal diffusivity of the composite material (propellant). Several candidate coats are selected and propellants are cast. These propellants (with coated oxidizers) are fired in a laboratory-scale end-burning rocket motor, and real-time pressure histories are recorded. The control propellant (with no coating) is also tested for comparison. The uniformity of the coating, confirmed by SEM pictures and BET adsorption measurements, is thought to be an advance in technology. The frequency of bulk mode instability (BMI), the pressure fluctuation amplitudes, and stability boundaries are correlated with parameters related to the characteristic length (L-asterisk) of the rocket motor. The coated oxidizer propellants, in general, display greater combustion stability than the control (state-of-the-art). The correlations of the various parameters are thought to be new to a field filled with much uncertainty.

Helmy, A. M.↗

NASA NTRS1985

Some design philosophy for reducing the community noise of advanced counter-rotation propellers

Advanced counter-rotation propellers have been indicated as possibly generating an unacceptable amount of noise for the people living near an airport. This report has explored ways to reduce this noise level, which is treated as being caused by the interaction of the upstream propeller wakes and vortices with the downstream propeller. The noise reduction techniques fall into two categories: (1) reducing the strength of the wakes and vortices, and (2) reducing the response of the downstream blades to them. The noise from the wake interaction was indicated as being reduced by increased propeller spacing and decreased blade drag coefficient. The vortex-interaction noise could be eliminated by having the vortex pass over the tips of the downstream blade, and it could be reduced by increased spacing or decreased initial circulation. The downstream blade response could be lessened by increasing the reduced frequency parameter omega or by phasing of the response from different sections to have a mutual cancellation effect. Uneven blade to blade spacing for the downstream blading was indicated as having a possible effect on the annoyance of counter-rotation propeller noise. Although there are undoubtedly additional methods of noise reduction not covered in this report, the inclusion of the design methods discussed would potentially result in a counter-rotation propeller that is acceptably quiet.

Dittmar, J. H.↗

NASA NTRS1986

Pusher propeller noise directivity and trends

The effects of pylon wake interaction on far-field propeller noise are studied using a model scale SR-2 propeller in a low-speed anechoic wind tunnel. The variation in the pusher noise penalty with axial angle theta and circumferential angle phi is compared to that of the tractor noise penalty; and the former exhibits minima occurring in the propeller plane and maxima occurring toward the propeller axis. The magnitude of the pusher installation noise penalty decreased with in increase in shaft horsepower and tip Mach number. Directivity comparisons revealed that both a noise reduction and a directivity pattern change resulted when the pylon was moved farther from the propeller. Noise emerging from the wake interaction was distinguished from that of the propeller by means of a modal decomposition.

Block, P. J. W.↗

NASA NTRS1987

Advanced propeller research

Resent results of aerodynamic and acoustic research on both single and counter-rotation propellers are reviewed. Data and analytical results are presented for three propellers: SR-7A, the single rotation design used in the NASA Propfan Test Assessment (PTA); and F7-A7, the 8+8 counterrotating design used in the proof-of-concept Unducted Fan (UDF) engine. In addition to propeller efficiencies, cruise and takeoff noise, and blade pressure data, off-design phenomena involving formation of leading edge vortices are described. Aerodynamic and acoustic computational results derived from three-dimensional Euler and acoustic radiation codes are presented. Research on unsteady flows, which are particularly important for understanding counterrotation interaction noise, unsteady loading effects on acoustics, and flutter or forced response is described. The first results of three-dimensional unsteady Euler solutions are illustrated for a single rotation propeller at an angle of attack and for a counterrotation propeller. Basic experimental and theoretical results from studies of the unsteady aerodynamics of oscillating cascades are outlined. Finally, advanced concepts involving swirl recovery vanes and ultra bypass ducted propellers are discussed.

Groeneweg, John F.↗

NASA NTRS1987

STS propellant scavenging systems study. Part 2, volume 2: Cost and WBS/dictionary

Presented are the results of the cost analysis performed to update and refine the program phase C/D cost estimates for a Shuttle Derived Vehicle (SDV) tanker. The SDV tanker concept is an unmanned cargo vehicle incorporating a set of propellant tanks in the vehicle's payload module. The tanker will be used to meet the demand for a cryogenic propellant supply in orbit. The propellant tanks are delivered to a low Earth orbit or to an orbit in the vicinity of the Space Station. The intent of the economic analysis is to provide NASA with economic justification for the propellant scavenging concept that minimizes the total Space Transportation System life cycle cost. The detailed costs supporting the concept selection process are presented with descriptive text to aid in forecasting the phase C/D project and program planning. Included are all propellant scavenging costs as well as all SDV, STS and Orbital Maneuvering Vehicle charges to deliver the propellants to the Space Station.

Williams, Frank L.↗

NASA NTRS1988

Porous wind tunnel corrections for counterrotation propeller testing

Wind tunnel interference corrections have direct impact on measured propeller efficiency. A systematic series of wind tunnel tests was done in the porous-wall NASA Lewis 8- by 6-Foot Wind Tunnel to determine the wind tunnel interference corrections to the NASA Lewis counterrotation propeller test data. The test results were compared with calculations from a potential flow code to determine the interference corrections. At a Mach number of 0.8, the interference corrections resulted in a -0.008 Mach number correction which reduced the counterrotation propeller net efficiency data by 0.46 percent at the reduced Mach number. Additional wind tunnel tests were done to measure the effect of propeller thrust on wind tunnel wall interference. No wall interference corrections due to propeller thrust were found necessary for the high speed counterrotation propeller data obtained in the porous wall NASA Lewis 8- by 6-Foot Wind Tunnel.

Stefko, George L.↗

NASA NTRS1988

Porous wind tunnel corrections for counterrotation propeller testing

Wind tunnel interference corrections have direct impact on measured propeller efficiency. A systematic series of wind tunnel tests was done in the porous-wall NASA Lewis 8- by 6-Foot Wind Tunnel to determine the wind tunnel interference corrections to the NASA Lewis counterrotation propeller test data. The test results were compared with calculations from a potential flow code to determine the interference corrections. At a Mach number of 0.8, the interference corrections resulted in a -0.008 Mach number correction which reduced the counterrotation propeller net efficiency data by 0.46 percent at the reduced Mach number. Additional wind tunnel tests were done to measure the effect of propeller thrust on wind tunnel wall interference. No wall interference corrections due to propeller thrust were found necessary for the high speed counterrotation propeller data obtained in the porous wall NASA Lewis 8- by 6-Foot Wind Tunnel.

Stefko, George L.↗

NASA NTRS1989

Unsteady blade pressure measurements on a model counterrotation propeller

In an exploratory effort an advanced counterrotation propeller instrumented with blade-mounted pressure transducers was tested in the NASA Lewis 9- by 15-Foot Anechoic Wind Tunnel at a simulated takeoff and landing speed of Mach 0.20. The propeller's aft diameter was reduced to investigate possible noise reductions resulting from reduced blade row interaction with the tip vortex. The propeller was tested at three blade row spacings at fixed blade setting angles, at the maximum blade row spacing at higher blade setting angles and at propeller axis angles attack to the flow up to + or - 16 deg. A limited number of unsteady blade surface pressure measurements were made on both rotors of the model counterrotation propeller. Emphasis was placed on determining the effects of rotor-rotor interactions on the blade surface pressures. A unique method of processing the pressure signals was developed that enables even weak interaction waveforms and spectra to be separated from the total signal. The interaction on the aft rotor was many times stronger than that on the forward rotor. The fundamental rotor interaction tone exhibited complicated behavior but generally increased with rotational speed and blade setting angle and decreased with rotor spacing. With the propeller axis at an angle to the flow, the phase response of the aft rotor appeared to be significantly affected by the presence of the forward rotor.

Heidelberg, Laurence J.↗

NASA NTRS1988

In-situ propellant advantages for fast transfer to Mars

The advantages of in situ propellant for a fast transfer to Mars were studied as compared to all earth-based propellants and other options for reduction of total masss in low earth orbit. For a 10-year, 10-mission model and a baseline vehicle taken from the literature, the total reduction in number of earth launches was calculated. The scenario in which the return propellants are transferred to Mars on a slow cargo vehicle provides a 29-percent reduction in ALS launches over the baseline scenario in which all propellants are brought directly from earth. The scenarios in which in situ propellants are used for a successively greater portion of the total mission continue to reduce the number of launches required. With Mars propellant used for the Mars ascent vehicle and the return leg of the mission, a 59-percent reduction in launches is obtained. Finally, if the oxygen, or oxygen and fuel, for the outbound leg of the mission is also obtained by in situ production, from the moon for example, then the total reduction in number of earth launches is more than 80 percent.

Galecki, Diane L.↗

NASA NTRS1989

Unsteady blade pressure measurements on a model counterrotation propeller

In an exploratory effort an advanced counterrotation propeller instrumented with blade-mounted pressure transducers was tested in the NASA Lewis 9- by 15-Foot Anechoic Wind Tunnel at a simulated takeoff and landing speed of Mach 0.20. The propeller's aft diameter was reduced to investigate possible noise reductions resulting from reduced blade row interaction with the tip vortex. The propeller was tested at three blade row spacings at fixed blade setting angles, at the maximum blade row spacing at higher blade setting angles and at propeller axis angles attack to the flow up to + or - 16 deg. A limited number of unsteady blade surface pressure measurements were made on both rotors of the model counterrotation propeller. Emphasis was placed on determining the effects of rotor-rotor interactions on the blade surface pressures. A unique method of processing the pressure signals was developed that enables even weak interaction waveforms and spectra to be separated from the total signal. The interaction on the aft rotor was many times stronger than that on the forward rotor. The fundamental rotor interaction tone exhibited complicated behavior but generally increased with rotational speed and blade setting angle and decreased with rotor spacing. With the propeller axis at an angle to the flow, the phase response of the aft rotor appeared to be significantly affected by the presence of the forward rotor.

Heidelberg, Laurence J.↗

NASA NTRS1990

Propeller tip vortex interactions

Propeller wakes interacting with aircraft aerodynamic surfaces are a source of noise and vibration. For this reason, flow visualization work on the motion of the helical tip vortex over a wing and through the second stage of a counterrotation propeller (CRP) has been pursued. Initially, work was done on the motion of a propeller helix as it passes over the center of a 9.0 aspect ratio wing. The propeller tip vortex experiences significant spanwise displacements when passing across a lifting wing. A stationary propeller blade or stator was installed behind the rotating propeller to model the blade vortex interaction in a CRP. The resulting vortex interaction was found to depend on the relative vortex strengths and vortex sign.

Johnston, Robert T.↗

NASA NTRS1990

Acoustic and aerodynamic study of a pusher-propeller aircraft model

An aerodynamic and acoustic study was made of a pusher-propeller aircraft model in the NASA-Ames 7 x 10 ft Wind Tunnel. The test section was changed to operate as an open jet. The 591 mm diameter unswept propeller was operated alone and in the wake of three empennages: an I tail, Y tail, and a V tail. The radiated noise and detailed wake properties were measured. Results indicate that the unsteady blade loading caused by the blade interactions with the wake mean velocity distribution had a strong effect on the harmonics of blade passage noise. The blade passage harmonics above the first were substantially increased in all horizontal directions by the empennage/propeller interaction. Directivity in the plane of the propeller was maximum perpendicular to the blade surface. Increasing the tail loading caused the propeller harmonics to increase 3 to 5 dB for an empennage/propeller spacing of 0.38 mean empennage chords. The interaction noise became weak as empennage propeller spacing was increased beyond 1.0 mean empennage chord lengths. Unlike the mean wake deficit, the wake turbulence had only a small effect on the propeller noise, that effect being a small increase in the broadband noise.

Soderman, Paul T.↗

NASA NTRS1990

Helium Saturation of Liquid Propellants

The research is in three areas which are: (1) techniques were devised for achieving the required levels of helium (He) saturation in liquid propellants (limited to monomethylhydrazine (MMH) and nitrogen tetroxide (NTO)); (2) the values were evaluated for equilibrium solubilities of He in liquid propellants as currently used in the industry; and (3) the He dissolved in liquid propellants were accurately measured. Conclusions drawn from these studies include: (1) Techniques for dissolving He in liquid propellants depending upon the capabilities of the testing facility (Verification of the quantity of gas dissolved is essential); (2) Until greater accuracy is obtained, the equilibrium solubility values of He in MMH and NTO as cited in the Air Force Propellant Handbooks should be accepted as standard (There are still enough uncertainties in the He saturation values to warrant further basic experimental studies); and (3) The manometric measurement of gas volume from a frozen sample of propellant should be the accepted method for gas analysis.

Yavrouian, A. H.↗

NASA NTRS1991

Method of injecting fluid propellants into a rocket combustion chamber

A rocket injector is provided with multiple sets of manifolds for supplying propellants to injector elements. Sensors transmit the temperatures of the propellants to a suitable controller which is operably connected to valves between these manifolds and propellant storage tanks. Additional valves are opened to furnish propellants to more of the manifolds when cryogenic propellant temperatures are sensed. Only a portion of the valves are opened to furnish propellants to some of the manifolds when lower temperatures are sensed.

Schneider, Steven J.↗

NASA NTRS1991

The NASA aircraft noise prediction program improved propeller analysis system

The improvements and the modifications of the NASA Aircraft Noise Prediction Program (ANOPP) and the Propeller Analysis System (PAS) are described. Comparisons of the predictions and the test data are included in the case studies for the flat plate model in the Boundary Layer Module, for the effects of applying compressibility corrections to the lift and pressure coefficients, for the use of different weight factors in the Propeller Performance Module, for the use of the improved retarded time equation solution, and for the effect of the number grids in the Transonic Propeller Noise Module. The DNW tunnel test data of a propeller at different angles of attack and the Dowty Rotol data are compared with ANOPP predictions. The effect of the number of grids on the Transonic Propeller Noise Module predictions and the comparison of ANOPP TPN and DFP-ATP codes are studied. In addition to the above impact studies, the transonic propeller noise predictions for the SR-7, the UDF front rotor, and the support of the enroute noise test program are included.

Nguyen, L. Cathy↗

NASA NTRS1992

Noise of two high-speed model counter-rotation propellers at takeoff/approach conditions

This paper presents acoustic results for two model counter-rotation propellers which were tested in the NASA Lewis 9- x 15-ft Anechoic Wind Tunnel. The propellers had a common forward rotor, but the diameter of the aft rotor of the second propeller was reduced in an effort to reduce its interaction with the forward rotor tip vortex. The propellers were tested at Mach 0.20, which is representative of takeoff/approach operation. Acoustic results are presented for these propellers which show the effect of rotor spacing, reduced aft rotor diameter, operation at angle-of-attack, blade loading, and blade number. Limited aerodynamic results are also presented to establish the propeller operating conditions.

Woodward, Richard P.↗