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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Rotor burst protection program - Statistics on aircraft gas turbine engine rotor failures that occurred in U.S. commercial aviation during 1973

This paper presents statistical information on the aircraft gas turbine engine rotor failures that occurred in U.S. commercial aviation during 1973. Based on FAA data, results are presented that establish (1) the incidence of rotor failure, (2) the type of fragments generated, (3) whether or not these fragments were contained, (4) the causes of failure, (5) where in the engine failure occurred, (6) what engines were affected, and (7) what flight conditions prevailed at failure. The rate of uncontained rotor burst was considered to be significantly high.

Mangano, G. J.↗
NASA NTRS1975

Investigation of rotor blade element airloads for a teetering rotor in the blade stall regime (second wind tunnel test)

A test was conducted in the NASA-Ames 7 x 10 ft low speed wind tunnel on a seven-foot diameter model of a teetering rotor. The objectives of the test were: (1) acquire pressure data for correlation with laser and flow visualization measurements; (2) explore rotor propulsive force limits by varying the advance ratio at constant lift and propulsive force coefficients; (3) obtain additional data to define the differences between teetering and articulated rotors; and (4) verify the acceleration sensitivity of experimental transducers. Results are presented.

Dadone, L. U.↗
NASA NTRS1976

Aerodynamic characteristics of a 1/6-scale model of the rotor systems research aircraft with the rotors removed

A wind-tunnel investigation was conducted to refine the aerodynamic characteristics of the rotor systems research aircraft. For the investigation, a 1/6-scale model without a main rotor or a tail rotor was used. The model provided the capability for testing different engine nacelle sizes, engine pylon fairings, and tail configurations. The engine thrust effects were modeled by small engine simulators (fans). Data were obtained primarily over an angle-of-attack range from -13 deg to 13 deg at several values of sideslip. Stability characteristics and control effectiveness were investigated. The model with the scaled engine nacelles and the combination T-tail and lower horizontal tail displayed longitudinal and lateral-directional stability. Results show that by reducing the horizontal or vertical-tail span the longitudinal stability is decreased. Reducing the engine nacelle size increases the static stability of the model. Effective dihedral is essentially zero at 0 deg angle of attack and 0 deg wing incidence.

Mineck, R. E.↗
NASA NTRS1976

An investigation of flap-lag stability of wind turbine rotors in the presence of velocity gradients and helicopter rotors in forward flight

The flap-lag equations of motion of a torsionally rigid and centrally hinged spring-restrained rigid blade are developed using quasi-steady blade-element aerodynamic theory. These equations have periodic coefficients and are applicable to both wind-turbine rotors with velocity gradients and helicopter rotors in forward flight. By solving these equations both by the Floquet-Liapunov method and by an approximate method, the range of applicability of the latter method is established. Flap-lag and pure flapping stability boundaries illustrating the effects of flow and rotor parameters are presented. Finally, some discussion on the techniques for generating the Floquet transition matrix and on the relative merits of the coordinate axes system is presented.

Kaza, K. R. V.↗
NASA NTRS1976

Wind tunnel test on a 1/4.622 Froude scale, hingeless rotor, tilt rotor model, volume 1

Wing tunnel test data on a 1/4.622 Froude scale, hingeless rotor, tilt rotor mode are reported for all potential flight conditions through hover and a wide envelope of transitions. A mathematical model was used to describe the rotor system in real time simulation by means of regression analyses. Details of the model, test program and data system are provided together with four data files for hover and transition.

Magee, J. P.↗
NASA NTRS1977

Airframe, wing, and tail aerodynamic characteristics of a 1/6-scale model of the rotor systems research aircraft with the rotors removed

A wind-tunnel investigation was conducted to determine the aerodynamic characteristics of the rotor systems research aircraft (RSRA) as the helicopter and the compound helicopter with the rotors removed. Data were obtained over ranges of angle of attack and angle of sideslip. Results are presented for the total loads on the airframe as well as the loads on the wing and the tail. The results indicate that the RSRA with the rotors removed has stable static longitidinal and directional characteristics and has stable effective dihedral.

Mineck, R. E.↗
NASA NTRS1976

Aeroelastic stability of complete rotors with application to a teetering rotor in forward flight

The derivation of a set of nonlinear coupled flap-lag-torsion equations of motion for moderately large deflections of an elastic, two bladed teetering helicopter rotor in forward flight is concisely outlined. The following degrees of freedom are included in the mathematical model: rigid body flapping, rigid body lead lag, elastic bending in flap and lead-lag blade root torsion and shaft torsion. Quasi-steady aerodynamic loads are considered and the effects of reversed flow are included. The aeroelastic stability of the complete rotor is investigated using a linearized system of equations of motion. The equilibrium position about which the equations are linearized is obtained by considering the trim state of the helicopter, in true or simulated forward flight conditions. The sensitivity of the aeroelastic stability boundaries to interblade structural and mechanical coupling is illustrated by comparing the complete rotor stability boundaries with those obtained from a single blade analysis for a number of hover and forward flight cases.

Shamie, J.↗
NASA NTRS1977

Aeroelastic stability of complete rotors with application to a teetering rotor in forward flight

The derivation of a set of non-linear coupled flap-lag-torsion equations of motion for moderately large deflections of an elastic, two-bladed teetering helicopter rotor in forward flight is concisely outlined. The following degrees of freedom are included in the mathematical model: rigid body flapping, rigid body lead-lag, elastic bending in flap and lead-lag, blade root torsion, and shaft torsion. Quasi-steady aerodynamic loads are considered and the effects of reversed flow are included. The aeroelastic stability of the complete rotor is investigated by using a linearized system of equations of motion. The equilibrium position about which the equations are linearized is obtained by considering the trim state of the helicopter, in true or simulated forward flight conditions. The sensitivity of the aeroelastic stability boundaries to interblade structural and mechanical coupling is illustrated by comparing the complete rotor stability boundaries with those obtained from a single blade analysis for a number of hover and forward flight cases.

Shamie, J.↗
NASA NTRS1981

Rotor wake characteristics relevant to rotor-stator interaction noise generation

Mean and turbulent wake properties at three axial locations behind the rotor of an aerodynamically loaded 1.2 pressure ratio fan were measured using a stationary cross film anemometer in an anechoic wind tunnel. Wake characteristics at four radial immersions across the duct at four different fan speeds were determined utilizing a signal enhancement technique. The shapes of the waveforms of the mean rotor relative and mean upwash velocities were shown to change significantly across the span of the blades. In addition, an increase in fan rotational speed caused an increase in the maximum wake turbulence intensity levels near the hub and tip. Spectral analysis was used to described the complex nature of the rotor wake.

Shaw, L. M.↗
NASA NTRS1981

Predesign study for a modern 4-bladed rotor for the NASA rotor systems research aircraft

Trade-off study results and the rationale for the final selection of an existing modern four-bladed rotor system that can be adapted for installation on the Rotor Systems Research Aircraft (RSRA) are reported. The results of the detailed integration studies, parameter change studies, and instrumentation studies and the recommended plan for development and qualification of the rotor system is also given. Its parameter variants, integration on the RSRA, and support of ground and flight test programs are also discussed.

Bishop, H. E.↗
NASA NTRS1981

Rotor fragment protection program: Statistics on aircraft gas turbine ngine rotor failures that occurred in U.S. commercial aviation during 1978

This report presents statistical information relating to the number of gas turbine engine rotor failures which occurred in commercial aviation service use. The predominant failure involved blade fragments, 82.4 percent of which were contained. Although fewer rotor rim, disk, and seal failures occurred, 33.3%, 100% and 50% respectively were uncontained. Sixty-five percent of the 166 rotor failures occurred during the takeoff and climb stages of flight.

Delucia, R. A.↗
NASA NTRS1981

Rotor wake characteristics relevant to rotor-stator interaction noise generation

Mean and turbulence wake properties at three axial locations behind the rotor of an aerodynamically loaded 1.2 pressure ratio fan were measured using a stationary cross film anemometer in an anechoic wind tunnel. Wake characteristics at four radial immersions across the duct at four different fan speeds were determined utilizing a signal enhancement technique. The shapes of the waveforms of the mean rotor relative and mean upwash velocities were shown to change significantly across the span of the blades. In addition, an increase in fan rotational speed caused an increase in the maximum wake turbulence intensity levels near the hub and tip. Spectral analysis was used to describe the complex nature of the rotor wake.

Shaw, L. M.↗
NASA NTRS1982

Rotor fragment protection program: Statistics on aircraft gas turbine engine rotor failures that occurred in US commercial aviation during 1979

Statistical information relating to the number of gas turbine engine rotor failures which occurred during 1979 in commercial aviation service use is provided. The predominant failure mode involved blade fragments, 84 percent of which were contained. No uncontained disk failures occurred and although fewer rotor rim and seal failures occurred, 100 percent and 50 percent, respectively, were uncontained. Sixty-eight percent of the 157 rotor failures occurred during the take-off and climb stages of flight.

Delucia, R. A.↗
NASA NTRS1986

Symbolic generation of elastic rotor blade equations using a FORTRAN processor and numerical study on dynamic inflow effects on the stability of helicopter rotors

The process of performing an automated stability analysis for an elastic-bladed helicopter rotor is discussed. A symbolic manipulation program, written in FORTRAN, is used to aid in the derivation of the governing equations of motion for the rotor. The blades undergo coupled bending and torsional deformations. Two-dimensional quasi-steady aerodynamics below stall are used. Although reversed flow effects are neglected, unsteady effects, modeled as dynamic inflow are included. Using a Lagrangian approach, the governing equations are derived in generalized coordinates using the symbolic program. The program generates the steady and perturbed equations and writes into subroutines to be called by numerical routines. The symbolic program can operate on both expressions and matrices. For the case of hovering flight, the blade and dynamic inflow equations are converted to equations in a multiblade coordinate system by rearranging the coefficients of the equations. For the case of forward flight, the multiblade equations are obtained through the symbolic program. The final multiblade equations are capable of accommodating any number of elastic blade modes. The computer implementation of this procedure consists of three stages: (1) the symbolic derivation of equations; (2) the coding of the equations into subroutines; and (3) the numerical study after identifying mass, damping, and stiffness coefficients. Damping results are presented in hover and in forward flight with and without dynamic inflow effects for various rotor blade models, including rigid blade lag-flap, elastic flap-lag, flap-lag-torsion, and quasi-static torsion. Results from dynamic inflow effects which are obtained from a lift deficiency function for a quasi-static inflow model in hover are also presented.

Reddy, T. S. R.↗
NASA NTRS1987

Prediction of unsteady transonic rotor loads with a full-potential rotor code

A new version of the full-potential rotor code (FPR) is described. This revised version contains improvements in code structure, algorithm implementation, and input/output options over the earlier version. The FPR code is coupled to a rotor-wake and trim model and the resulting combined code is used to predict surface pressures for three experimentally tested helicopter rotors. Generally good agreement is seen between computed and experimental results.

Strawn, Roger C.↗
NASA NTRS1988

Development of an advanced high-speed rotor - Final results from the Advanced Flight Research Rotor program

The final results of the Advanced Flight Research Rotor (AFRR) study, a NASA sponsored research program, are summarized. First, the results of the initial phase of the AFRR program, consisting of the definition of a conventional rotor with planform and prescribed twist distributions, are briefly reviewed. The mechanism of the calculated performance benefit is then explained, and a detailed analysis of the prescribed twist distribution is presented. Recommendations are made on the practical means of approximating the prescribed twist on the actual rotor.

Jenks, Mark↗
NASA NTRS1991

The effects of Reynolds number, rotor incidence angle and surface roughness on the heat transfer distribution in a large-scale turbine rotor passage

A combined experimental and computational program was conducted to examine the heat transfer distribution in a turbine rotor passage geometrically similar to the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP). Heat transfer was measured and computed for both the full span suction and pressure surfaces of the rotor airfoil as well as for the hub endwall surface. The objective of the program was to provide a benchmark-quality database for the assessment of rotor heat transfer computational techniques. The experimental portion of the study was conducted in a large scale, ambient temperature, rotating turbine model. The computational portion consisted of the application of a well-posed parabolized Navier-Stokes analysis of the calculation of the three-dimensional viscous flow through ducts simulating a gas turbine package. The results of this assessment indicate that the procedure has the potential to predict the aerodynamics and the heat transfer in a gas turbine passage and can be used to develop detailed three dimensional turbulence models for the prediction of skin friction and heat transfer in complex three dimensional flow passages.

Blair, M. F.↗
NASA NTRS1991

Numerical prediction of wakes in cascades and compressor rotors including the effects of mixing. II - Rotor passage flow and wakes including the effects of spanwise mixing

The results of a numerical investigation to predict the flow field including wakes and mixing in axial-flow compressor rotors are presented. The wake behavior in a moderately loaded compressor rotor is studied numerically using a 3D incompressible Navier-Stokes solver with a high Reynolds number form of a turbulence model. The equations are solved using a time dependent implicit technique. The agreement between the measured data and the predictions is good; including the blade boundary-layer profiles, wake mean-velocity profiles, and decay. The ability of the pseudocompressibility scheme to predict the entire flow field including the near and far wake profiles and its decay characteristics, effect of loading, and the viscous losses of a 3D rotor flow field are demonstrated. The mixing in the downstream regions away from the hub and annulus walls is dominated by wake diffusion. In regions away from the walls the radial mixing is predominantly caused by the transport of mass, momentum, and energy by the radial component of velocity in the wake.

Lakshminarayana, B.↗