Experimental data for two 1400-feet per second tip speed compressor rotors operated with inlet flow distortions
Performance data for high tip speed compressor rotor operated with radial and inlet airflow distortions
Bailey, E. E.↗
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Broadband Noise Prediction of Two Small Hovering Rotors using FUN3D-ANOPP2
A computational study was performed on two small hovering rotors, the ideally twisted rotor and the optimum hovering 2-bladed rotor, using FUN3D-ANOPP2. The effects of different inviscid upwinding techniques and temporal resolutions on aerodynamic performance and acoustic prediction were compared against experimental data obtained in the Small Hover Anechoic Chamber facility at the NASA Langley Research Center. Decreasing the numerical dissipation with 𝜅 tuning or by using a higher-order inviscid flux reconstruction scheme was shown to improve aerodynamic performance predictions when compared to measured data for most cases. The effect of dissipation on the vorticity field was also seen to influence the amount of turbulence surrounding the vortex core of the first blade-vortex interaction (BVI), the coherence of the second and higher BVI vortex cores, and the downstream breakdown of the rotor wake for both rotor geometries. Tonal and broadband noise predictions from simulation cases with lower dissipation were seen to agree better with the experiment for the ideally twisted rotor, whereas temporal resolution differences had negligible impact on the broadband noise results. Similar fundamental BPF directivity patterns were obtained by all simulation cases for the optimum hovering 2-bladed rotor, while the most accurate 2*BPF directivity trend, compared to the experiment, was predicted by the lower-dissipation case at the coarse temporal resolution, albeit with an amplitude underprediction. Broadband noise spectral roll-off behavior was seen to occur at a higher frequency when using a finer temporal resolution for the optimum hovering 2-bladed rotor, unlike for the ideally twisted rotor geometry. The broadband noise prediction for the optimum hovering 2-bladed rotor from the higher-dissipation case at the coarse temporal resolution was also seen to predict a tone centered around approximately 8.5 kHz, which was similar in amplitude to the measured tone around 16.5 kHz.
Christopher S. Thurman↗
Single-stage experimental evaluation of tandem-airfoil rotor stator blading for compressors. Part 6: Data and performance for stage D
An axial flow compressor stage, having single-airfoil blading, was designed for zero rotor prewhirl, constant rotor work across the span, and axial discharge flow. The stage was designed to produce a pressure ratio of 1.265 at a rotor tip velocity of 757 ft/sec. The rotor had an inlet hub/tip ratio of 0.8. The design procedure accounted for the rotor inlet boundary layer and included the effects of axial velocity ratio and secondary flow on blade row performance. The objectives of this experimental program were: (1) to obtain performance with uniform and distorted inlet flow for comparison with the performance of a stage consisting of tandem-airfoil blading designed for the same vector diagrams; and (2) to evaluate the effectiveness of accounting for the inlet boundary layer, axial velocity ratio, and secondary flows in the stage design. With uniform inlet flow, the rotor achieved a maximum adiabatic efficiency of 90.1% at design equivalent rotor speed and a pressure ratio of 1.281. The stage maximum adiabatic efficiency at design equivalent rotor speed with uniform inlet flow was 86.1% at a pressure ratio of 1.266. Hub radial, tip radial, and circumferential distortion of the inlet flow caused reductions in surge pressure ratio of approximately 2, 10 and 5%, respectively, at design rotor speed.
Clemmons, D. R.↗
Penn State axial flow turbine facility: Performance and nozzle flow field
The objective is to gain a thorough understanding of the flow field in a turbine stage including three-dimensional inviscid and viscid effects, unsteady flow field, rotor-stator interaction effects, unsteady blade pressures, shear stress, and velocity field in rotor passages. The performance of the turbine facility at the design condition is measured and compared with the design distribution. The data on the nozzle vane static pressure and wake characteristics are presented and interpreted. The wakes are found to be highly three-dimensional, with substantial radial inward velocity at most spanwise locations.
Lakshminarayana, B.↗
A study of the effects of disk flexibility on the rotordynamics of the space shuttle main engine turbo-pumps
Rotor dynamical analyses are typically performed using rigid disk models. Studies of rotor models in which the effects of disk flexibility were included indicate that is may be an important effect for many systems. This issue is addressed with respect to the Space Shuttle Main Engine high pressure turbo-pumps. Finite element analyses have been performed for a simplified free-free flexible disk rotor model and the modes and frequencies compared to those of a rigid disk model. The simple model was then extended to a more sophisticated HPTOP rotor model and similar results were observed. Equations were developed that are suitable for modifying the current rotordynamical analysis program to account for disk flexibility. Some conclusions are drawn from the results of this work as to the importance of disk flexibility on the HPTOP rotordynamics and some recommendations are given for follow-up research in this area.
Flowers, George T.↗
An Exploration of the Performance and Acoustic Characteristics of UAV-Scale Stacked Rotor Configurations
As interest grows in rotor- and propeller-driven electric vertical takeoff and landing (eVTOL) aircraft for the Urban Air Mobility market, there is a potential for previously studied concepts to reemerge due to the opportunities afforded by novel technologies and operating modes. One such concept is the “stacked” rotor, which consists of multiple co-rotating rotors positioned co-axially with a small axial offset. The goal of the work presented in this paper is to determine whether stacked rotors offer a compelling advantage for eVTOL aircraft in terms of both performance and acoustic characteristics. Results are presented for new experimental tests and computational modeling of multiple stacked rotor configurations, and comparisons are made with conventional rotor configurations. Testing of thirteen separate configurations— each using the same blade shape—revealed a configuration that resulted in an increase in the rotor power loading efficiency by more than 7% and reduced noise by more than 3 dBA when compared with a conventional rotor with all blades located in the same rotational plane.
Whiteside, Siena K. S.↗
Overall and blade-element performance of a multiple-circular-arc bladed transonic compressor rotor with tip speed of 1375 feet per second
The design and experimental performance of a 20-inch-diameter multiple-circular-arc bladed axial-flow transonic compressor rotor is presented. Radial surveys of the flow conditions were made. At design speed the peak efficiency was 0.882 and occurred at a weight flow of 64.0 pounds per second. At this point the total-pressure and total-temperature ratios were 1.79 and 1.205, respectively. The stall margin at design speed was 8 percent based on weight flows and total-pressure ratios at experimental peak efficiency and near stall. The measured stall margin was 20 percent at design weight flow and speed.
Kovich, G.↗
Design and performance of a 0.9 hub-tip-ratio axial flow pump rotor with a blade-tip diffusion factor of 0.63
Design and performance of 0.9-hub-tip-ratio axial flow pump rotor with blade-tip diffusion factor of 0.63
Urasek, D. C.↗
Performance and Environmental Assessment of an Advanced Aircraft with Open Rotor Propulsion
Application of high speed, advanced turboprops, or "propfans," to transonic transport aircraft received significant attention during the 1970s and 1980s when fuel efficiency was the driving focus of aeronautical research. Unfortunately, after fuel prices declined sharply there was no longer sufficient motivation to continue maturing this technology. Recent volatility in fuel prices and increasing concern for aviation s environmental impact, however, have renewed interest in unducted, open rotor propulsion. Because of the renewed interest in open rotor propulsion, the lack of publicly available up-to-date studies assessing its benefits, and NASA s focus on reducing fuel consumption, a preliminary aircraft system level study on open rotor propulsion was initiated to inform decisions concerning research in this area. New analysis processes were established to assess the characteristics of open rotor aircraft. These processes were then used to assess the performance, noise, and emissions characteristics of an advanced, single-aisle aircraft using open rotor propulsion. The results of this initial study indicate open rotor engines have the potential to provide significant reductions in fuel consumption and landing-takeoff cycle NOX emissions. Noise analysis of the study configuration indicates that an open rotor aircraft in the single-aisle class would be able to meet current noise regulations with margin.
Guynn, Mark D.↗
Aeroelastic control of stability and forced response of supersonic rotors by aerodynamic detuning
Aerodynamic detuning, defined as designed passage-to-passage differences in the unsteady aerodynamic flow field of a rotor blade row, is a new approach to passive flutter and forced response control. In this paper, a mathematical model for aerodynamic detuning is developed and utilized to demonstrate the aeroelastic stability enhancement due to aerodynamic detuning of supersonic blade rows. In particular, a model is developed to analyze both the torsion mode and the coupled bending-torsion mode unstalled supersonic flutter and torsion mode aerodynamically forced response characteristics of an aerodynamically detuned rotor operating in a supersonic inlet flow field with a subsonic leading edge locus. As small solidity variations do not have a dominant effect on the steady-state performance of a rotor, the aerodynamic detuning mechanism considered is nonuniform circumferential spacing of adjacent blades.
Hoyniak, Daniel↗
BVI impulsive noise reduction by higher harmonic pitch control - Results of a scaled model rotor experiment in the DNW
Results are presented of a model rotor acoustics test performed to examine the benefit of higher harmonic control (HHC) of blade pitch to reduce blade-vortex interaction (BVI) impulsive noise. A dynamically scaled, four-bladed, rigid rotor model, a 40-percent replica of the B0-105 main rotor, was tested in the German Dutch Wind Tunnel. Noise characteristics and noise directivity patterns as well as vibratory loads were measured and used to demonstrate the changes when different HHC schedules were applied. Dramatic changes of the acoustic signatures and the noise radiation directivity with the HHC phase variations are found. Compared to the baseline conditions (without HHC), significant mid-frequency noise reductions of locally 6 dB are obtained for low-speed descent conditions where GVI is most intense. For other rotor operating conditions with less intense BVI there is less or no benefit from the use of HHC. LF noise and vibratory loads, especially at optimum noise reduction control settings, are found to increase.
Splettstoesser, Wolf R.↗
DESIGN AND EXPERIMENTAL INVESTIGATION OF A SINGLE-STAGE TURBINE WITH A ROTOR ENTERING RELATIVE MACH NUMBER OF 2
Design of single-stage turbine for rotor entering at supersonic speed - performance characteristics
PERFORMANCE CHARACTERISTICS↗
Summary of low-speed wind tunnel results of several high-speed counterrotation propeller configurations
The low speed aerodynamic performance characteristics of several advanced counterrotation pusher propeller configurations with cruise design Mach numbers of 0.72 and 0.80 were investigated in the NASA Low Speed Wind Tunnel. The tests were conducted at Mach numbers representative of the takeoff and landing flight regime. The investigation included: (1) the propeller performance characteristics over a range of blade angle settings and rotational speeds at a Mach number of 0.20; (2) the effect on the propeller performance of varying the axial rotor spacing and mismatching the power and rotational speeds on the propeller rotors; (3) determining the reverse thrust performance characteristics at Mach numbers of 0.0, 0.10, 0.15 and 0.20. The results of the investigation indicated that the overall low speed performance of the counterrotation propeller configurations was reasonable.
Hughes, Christopher E.↗
Aerodynamic detuning for aeroelastic control of stability and forced response of supersonic rotors
An unsteady aerodynamic model is developed to analyze flutter and aerodynamically forced response of aerodynamically detuned supersonic axial flow rotors. Alternate blade aerodynamic detuning is considered, accomplished by alternating the circumferential spacing of adjacent blades as small solidity variations which do not have a dominant effect on the steady performance of a rotor. The unsteady aerodynamics are determined by developing an influence coefficient technique which is appropriate for both aerodynamically tuned and detuned rotor configurations. Torsion mode rotor stability and aerodynamically forced response are then analyzed with this unsteady aerodynamic model by combining it with a single-degree-of-freedom structural model. The effects of this detuning on the flutter and forced response characteristics of supersonic axial flow rotors is then demonstrated by considering baseline twelve bladed rotors.
Spara, Karen M.↗
Navier-Stokes calculations of rotor-airframe interaction in forward flight
A method for analyzing the mutual aerodynamic interaction between a rotor and an airframe model has been developed. This technique models the rotor implicitly through the source terms of the momentum equations. A three-dimensional, incompressible, laminar, Navier-Stokes solver in cylindrical coordinates was developed for analyzing the rotor-airframe problem. The calculations are performed on a simplified rotor-airframe model at an advance ratio of 0.1. The airframe surface pressure predictions are found to be in good agreement with wind tunnel test data. Results are also presented for velocity and pressure field distributions in the wake of the rotor.
Zori, Laith A. J.↗
The Three Dimensional Flow Field at the Exit of an Axial-Flow Turbine Rotor
A systematic and comprehensive investigation was performed to provide detailed data on the three dimensional viscous flow phenomena downstream of a modem turbine rotor and to understand the flow physics such as origin, nature, development of wakes, secondary flow, and leakage flow. The experiment was carried out in the Axial Flow Turbine Research Facility (AFTRF) at Penn State, with velocity measurements taken with a 3-D LDV System. Two radial traverses at 1% and 10% of chord downstream of the rotor have been performed to identify the three-dimensional flow features at the exit of the rotor blade row. Sufficient spatial resolution was maintained to resolve blade wake, secondary flow, and tip leakage flow. The wake deficit is found to be substantial, especially at 1% of chord downstream of the rotor. At this location, negative axial velocity occurs near the tip, suggesting flow separation in the tip clearance region. Turbulence intensities peak in the wake region, and cross- correlations are mainly associated with the velocity gradient of the wake deficit. The radial velocities, both in the wake and in the endwall region, are found to be substantial. Two counter-rotating secondary flows are identified in the blade passage, with one occupying the half span close to the casino and the other occupying the half span close to the hub. The tip leakage flow is well restricted to 10% immersion from the blade tip. There are strong vorticity distributions associated with these secondary flows and tip leakage flow. The passage averaged data are in good agreement with design values.
Lakshminarayana, B.↗
An overview of NASA intermittent combustion engine research
This paper overviews the current program, whose objective is to establish the generic technology base for advanced aircraft I.C. engines of the early 1990's and beyond. The major emphasis of this paper is on development of the past two years. Past studies and ongoing confirmatory experimental efforts are reviewed, which show unexpectly high potential when modern aerospace technologies are applied to inherently compact and balanced I.C. engine configurations. Currently, the program is focussed on two engine concepts the stratified-charge, multi-fuel rotary, and the lightweight two-stroke diesel. A review is given of contracted and planned high performance one-rotor and one-cylinder test engine work addressing several levels of technology. Also reviewed are basic supporting efforts, e.g., the development and experimental validation of computerized airflow and combustion process models, being performed in-house at Lewis Research Center and by university grants.
Willis, E. A.↗
An overview of NASA intermittent combustion engine research
This paper overviews the current program, whose objective is to establish the generic technology base for advanced aircraft I.C. engines of the early 1990's and beyond. The major emphasis of this paper is on development of the past two years. Past studies and ongoing confirmatory experimental efforts are reviewed, which show unexpectedly high potential when modern aerospace technologies are applied to inherently compact and balanced I.C. engine configurations. Currently, the program is focussed on two engine concepts, the stratified-charge, multi-fuel rotary and the lightweight two-stroke diesel. A review is given of contracted and planned high performance one-rotor and one-cylinder test engine work addressing several levels of technology. Also reviewed are basic supporting efforts, e.g., the development and experimental validation of computerized airflow and combustion process models, being performed in-house at Lewis Research Center and by university grants. Previously announced in STAR as N84-24583
Willis, E. A.↗