Single-rotation Propeller Research Articles

The study of rotate speed influence on the performance of Contra-Rotation-Propeller in stratospheric airship

According to the requirements of a foreign high-altitude airship project, the Single-Rotation-Propeller (SRP) was designed under the maximum endurance factor criterion. The spacing influence on the Contra-Rotation-Propeller (CRP) was studied by numerical simulation analysis, the performance of front and rear propeller was compared with SRP. The result indicated that CRP was more efficient than SPR, the CRP has enormous potential in enhancing the aerodynamic performance.

The study of spacing influence on the performance of Contra-Rotation-Propeller in stratospheric airship

According to the requirements of a foreign high-altitude airship project, the Single-Rotation-Propeller (SRP) was designed under the maximum endurance factor criterion. The spacing influence on the Contra-Rotation-Propeller (CRP) was studied by numerical simulation analysis, the performance of front and rear propeller was compared with SRP. The result indicated that CRP was more efficient than SPR, the CRP has enormous potential in enhancing the aerodynamic performance.

Far-Field Sound Radiation Due to an Installed Open Rotor

Future single rotation propeller and contra-rotating advanced open rotor concepts promise a significant fuel efficiency advantage over current generation turbofan engines. The development of rotors which produce a minimum level of noise is a critical technical issue which needs to be resolved in order for these concepts to become viable aircraft propulsors. Noise and emissions are subject to stringent legislative requirements, thus accurate models are required in order to predict the noise radiated from aircraft engines. In this article, the development of a theoretical model to predict noise levels of an installed open rotor is reported. First a canonical problem is examined: how to predict the pressure field produced by a rotating ring of point sources adjacent to a rigid cylinder. Analytic expressions for the far-field pressure from a rotating ring of single-frequency monopole and dipole point sources, located near an infinitely long rigid cylinder, immersed in a constant axial mean flow, are explicitly formulated. Illustrative results show how the far-field pressure is affected by varying the source rotational direction, source location and source radius. Next the solution of the canonical problem is utilized to formulate a more advanced model to predict the noise due to an installed open rotor. In this model, the rotor noise sources are represented by a distribution of rotating sources. The adjacent aircraft fuselage is modeled by the rigid cylinder, and the effect of the fuselage boundary layer and other steady distortions are neglected. Also neglected is the scattering from other surfaces such as the pylon, wing and centerbody. This distributed source model can be used to calculate the effect of scattering of open rotor noise by an adjacent cylindrical fuselage. The model can be used to calculate both rotor-alone tones and tones produced by periodic unsteady loading on the rotor blades. Practical examples are provided which show how the effect of blade rotational direction and propeller location relative to the fuselage affect the sound produced by the interaction of a pylon wake with a rotor in a pusher configuration.

In-flight source noise of an advanced large-scale single-rotation propeller

Flight tests to define the far-field tone source at cruise conditions have been completed on the full-scale SR-7L advanced turboprop, which was installed on the left wing of a Gulfstream II aircraft. These measurements defined source levels for input into long-distance propagation models to predict en route noise. Infight data were taken for seven test cases. The sideline directivities measured showed expected maximum levels near 105 deg from the propeller upstream axis. However, azimuthal directivities based on the maximum observed sideline tone levels showed highest levels below the aircraft. The tone level reduction associated with reductions in propeller tip speed is shown to be more significant in the horizontal plane than below the aircraft.

Efficient hybrid scheme for the analysis of counter-rotating propellers

An efficient solution procedure has been developed for analyzing inviscid unsteady flow past counter rotating propellers. This scheme is first order accurate in time and second order in space, and has been extended to fourth order accuracy in the axial direction. The solution procedure has been applied to a 2-bladed SR-7 single rotation propeller and to a GE F7/A7 counter rotation propeller. The pressure coefficients and the global quantities, power and thrust, show good comparison with experimental measurements.

Asymptotic theory of propeller noise. II - Supersonic single-rotation propeller

This paper gives analytical formulas for the far-field harmonic components of the acoustic radiation from a B-bladed supersonic single-rotation propeller, in the asymptotic limit B —» °o. The dominant source, for radiation in a given direction, is identified as located at the Mach radius along the blade span, the radius that approaches the observer at precisely sonic speed, once in each rotation. Favorable agreement is found between the asymptotic prediction and the results of full numerical evaluation of the radiation integrals. Singular surfaces in the field are identified from the asymptotic formulas, which are extended to include chordwise noncompactness effects. These show, among other things, that supersonic propeller noise is an algebraically decreasing function of tip Mach number, once chordwise noncompactness effects are taken into account, in contrast to the exponential increase with tip Mach number of subsonic propeller noise.

An asymptotic theory of near-field propeller acoustics

This paper presents expressions for the harmonic components of the near-field acoustic pressure of a B-bladed unswept single-rotation propeller. These are derived using asymptotic approximations to the standard radiation integrals for steady loading and thickness noise, under the assumption that B is large. The dependence of the pressure on blade operating conditions (both supersonic and subsonic) is described by simple formulae, which provide significant insights into the mechanisms of sound generation by rotating bodies. For supersonic motion, the importance of sources satisfying the Ffowcs Williams & Hawkings sonic condition is demonstrated, whilst for subsonic blades the near-field noise is proved to be tip-dominated. Expressions for the noise (valid from close to the tips right out to infinity) are given in both cases, requiring matching across an Airy function smoothing region when the tips move subsonically. Excellent agreement between the asymptotic formulae and both full numerical evaluations (with a considerable saving in CPU time) and experimental data is achieved.

Panel method for counter-rotating propfans

A time domain source-doublet surface paneling method is developed for analyzing the unsteady loads on counter rotating propellers in incompressible irrotational flow. A scheme for treating the blade-wake interaction problem is described. Sample results for single rotation propellers are given, with comparisons to alternate theories and experiment. Finally, some preliminary results for quasi-steady and fully unsteady loads on counter rotating systems are presented.

Asymptotic theory of propeller noise. I - Subsonic single-rotation propeller

Asymptotic theory of propeller noise. I - Subsonic single-rotation propeller

Euler Analysis of the Three-Dimensional Flow Field of a High-Speed Propeller: Boundary Condition Effects

This paper presents the results of an investigation of the effects of far field boundary conditions on the solution of the three-dimensional Euler equations governing the flow field of a high-speed single rotation propeller. The results show that the solutions obtained with the nonreflecting boundary conditions are in good agreement with experimental data. The specification of nonreflecting boundary conditions is effective in reducing the dependence of the solution on the location of the far field boundary. Details of the flow field within the blade passage and the tip vortex are presented. The dependence of the computed power coefficient on the blade setting angle is examined.

低アスペクト比の回転翼面上の流れの可視化

Flow patterns on a rotary wing with low aspect ratio of 3.3 are experimentally investigated in the Göttingen type low speed wind tunnel. Single rotation propeller blade with radius of 0.3m is used as the model wing for the flow visualization. The flow phenomena on the blade are visualized by means of oil flow, tuft, mini-tuft and china clay methods, and recorded by the simultaneous photographs. The experimental results clearly show that the mini-tuft method is more suitable to visualize the flow on the rotary wing.

Noise radiation patterns of counter-rotation and unsteadily loaded single-rotation propellers

In order to understand the effects of installation on propeller noise, numerous measurements are required to define the directivity of the noise as well as the level. An experimental study was designed to map the noise radiation pattern for various single-rotation propeller (SRP) installations and one counter-rotation propeller (CRP) installation covering an area ± 60 deg from the propeller disk plane and ± 60 deg laterally. The configurations considered included an SRP at angle of attack and in tractor and pusher operations and a CRP. A firstprinciples linear theory was validated for the SRP tractor operation over the angle range mentioned above. The increases in noise that arise from an unsteady loading operation such as an SRP pusher or a CRP exceed 15 dB and depend on the observer location. In particular, the majority of the additional noise from the unsteady loading appears to radiate in the axial directions.

Counter-Rotating Propellers

AbstractThis paper is concerned mainly with that application of counter-rotating propellers referred to as “ dual-rotation ” propellers. This term is here defined to apply to a pair of oppositely-rotating propellers operating in close tandem, mounted on concentric shafts. Only the application to aeroplanes is discussed herein, for the application of these principles to helicopter design is considered another subject.This paper presents a summary of the development and background of dual-rotation propellers and the benefits that can be derived from their use. Complete references are furnished for designers, no attempt being made to reproduce the somewhat involved theory and lengthy reference data.A short history of the three applications of counter-rotating propellers is presented. The applications include multi-motored aeroplanes with oppositely-rotating propellers, aeroplanes with engines mounted in tandem (back to back) so that the propellers revolve in opposite directions, but primarily, aeroplanes with dual-rotation propeller installations.Most present-day aeroplanes with maximum velocities of 350 m.p.h. and over have single-rotation propellers. At this velocity the single propeller is operating past the peak of its efficiency. The loss in efficiency increases rapidly with increasing forward velocity. Dual-rotation propellers offer an excellent means of maintaining peak propeller efficiencies up to aeroplane velocities of about 450 m.p.h. by absorbing the rotational energy losses in the propeller slipstream. At velocities above 450 m.p.h. up to the limiting velocity there will be only a small reduction from the peak in dual-rotation propeller efficiencies.Sustained level flight aeroplane velocities appear to be limited to about 550 m.p.h. when propellers are used as the means of propulsion. The efficiency of a conventional single-rotation propeller will be so low, however, that this limiting velocity can be approached with such a propeller only at a prohibitive cost in engine horse-power. Any given velocity above 300 m.p.h. can be obtained with less horse-power if dual-rotation propellers are used to replace a single-rotation propeller with the same total number of blades. The percentage gain in performance will increase with increasing forward velocity when dual-rotation propellers are used.It is possible that single-rotation propellers with more than four blades will never be commonly used. Instead, dual-rotation propellers with a total of four, six or perhaps even eight blades, will be used in the next decade on many high performance aeroplanes, especially those operating at high altitudes. The types of aeroplanes will include small single-seater racers and fighters and high performance, long range bombers and transports, particularly those with supercharged cabins.The discussion brings forth the fact that there are few experimental data available in this country to allow a quantitative engineering evaluation to be made of the worth of dual-rotation propellers. Sufficient substantiated theory exists, however, to permit the general statements made above. An outline of the experimental tests that are required to check the theory is presented.Following the discussion of tests made by the U.S. Air Corps on a pursuit type aeroplane equipped with a dual-rotation propeller system, comments are made on the relative advantages and disadvantages of dual and single-rotation propellers as they affect aeroplane design. Hub design problems associated with dual-rotation propellers are discussed.Because of the increasing importance of dual-rotation propellers, additional pertinent references other than those used in this paper are presented in the Appendix.