The Experts below are selected from a list of 2574 Experts worldwide ranked by ideXlab platform
Hao Guo - One of the best experts on this subject based on the ideXlab platform.
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Performance of Contra-Rotating Propellers for Stratospheric Airships
International Journal of Aeronautical and Space Sciences, 2015Co-Authors: Zhihao Tang, Peiqing Liu, Jingwei Sun, Yaxi Chen, Hao GuoAbstract:Small advance ratio and low Reynolds number of stratospheric propulsion system bring lots of challenges to the design of Propellers. Contra-Rotating Propeller configuration is proposed to improve the propulsion efficiency. In this paper, the feasibility of contra-Rotating Propeller for stratospheric airship has been assessed and its performance has been investigated by wind tunnel tests. The experimental results indicate, at relatively low Reynolds number, although the advance ratio is fixed, the performance of Propellers is different with variation of Reynolds number. Moreover, at the same Reynolds number, the efficiency of contra-Rotating Propeller achieved appears to be a few percent greater than that for a standard conventional propulsion system. It can be concluded that contra-Rotating Propellers would be an efficient means to improve the performance of stratospheric airship propulsion system.
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Experimental Feasibility Assessment of Counter-Rotating Propellers for Stratospheric Airships
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Peiqing Liu, Zhihao Tang, Yaxi Chen, Hao GuoAbstract:A series of systematic wind tunnel tests of a given stratospheric airship counter-Rotating Propeller have been conducted in this paper. The basic aerodynamic performance of the stratospheric airship counter-Rotating Propeller has been explored. In addition, different from conventional Propellers, the effect of low Reynolds number has been illustrated. Compared with single-Rotating Propellers, the interference between front and rear Propeller has also been discussed. The experimental results indicate that low Reynolds number would strongly reduce the efficiency of counter-Rotating Propellers. Due to the interference between a pair of Propellers, the performance of front Propeller gets slightly worse, whereas the performance of rear Propeller turns much better. A significant improvement of efficiency of overall CRP would be gained. By comparison with other configuration of Propeller propulsion system, it indicates the counter-Rotating Propeller would be a wise option applied on stratospheric airships.
A. B. Parry - One of the best experts on this subject based on the ideXlab platform.
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Time-domain analysis of contra-Rotating Propeller noise: wake interaction with a downstream Propeller blade
Journal of Fluid Mechanics, 2020Co-Authors: Michael Kingan, A. B. ParryAbstract:This paper describes a theoretical study – in the time domain – of sound from the interaction of the steady component of the viscous wakes of an upstream Propeller with a downstream contra-Rotating Propeller blade. The study incorporates a two-dimensional model of the upstream Propeller wakes and a quasi-three-dimensional blade response function that accounts for downstream blade sweep. For a blade with a straight leading edge, the sound at the observer location, radiated from each blade radius, consists of a series of impulses whose peaks are shown to be influenced by micro Doppler effects and to correspond to the impingement of the Propeller wake centrelines on the leading edge of the downstream blade. For radiation from the entire blade span, it is shown that constructive interference of the impulses from all radii can produce impulsive sound of very high amplitude, whereas dephasing of these impulses can reduce significantly the total acoustic signal. For a downstream Propeller blade with a swept leading edge, it is shown how the sweep can be designed to ensure that these impulses are de-phased, resulting in significantly lower-amplitude sound at selected observer locations. Finally, to guarantee that the radiated sound is reduced at all possible observer locations, it is shown that the blade leading-edge sweep must be large enough that the trace velocity of the wake centreline, across the leading edge of the downstream Propeller blade, is subsonic across the entire span. The benefits are demonstrated for representative blade designs.
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Acoustic theory of the many-bladed contra-Rotating Propeller: analysis of the effects of blade sweep on wake interaction noise
Journal of Fluid Mechanics, 2019Co-Authors: Michael Kingan, A. B. ParryAbstract:An analytical model is presented for the wake interaction tones produced by a contra-Rotating Propeller. We re-cast the usual far-field radiation formulae as a double integral over a nominal Propeller source annulus. Assuming that the number of blades on both Propellers is large, we evaluate the integral asymptotically in terms of its leading-order contributions from interior stationary or boundary critical points which represent the specific locations on the Propeller annulus that dominate the sound radiation. The asymptotic approach is powerful producing results in the form of one-line algebraic formulae that contain no integrals or special functions yet remain accurate. The asymptotics show that sweep is not necessarily beneficial and can cause the blade design to become critical for particular tones and directions in terms of a continuum of interior points distributed along a line on the Propeller source annulus producing a higher-order result and thus an enhanced radiated sound field. The paper also shows how the interior points are completely consistent with the sub- or super-critical gust response of a swept blade. Tones with low and zero azimuthal mode order are treated as special cases and the asymptotics show that, as the mode order reduces, the radiated sound becomes concentrated around the flight axis where even higher-order solutions are possible, including rings and annuli of stationary points around the Propeller annulus. Full numerical calculations confirm the accuracy of the asymptotic approach.
Michael Kingan - One of the best experts on this subject based on the ideXlab platform.
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Time-domain analysis of contra-Rotating Propeller noise: wake interaction with a downstream Propeller blade
Journal of Fluid Mechanics, 2020Co-Authors: Michael Kingan, A. B. ParryAbstract:This paper describes a theoretical study – in the time domain – of sound from the interaction of the steady component of the viscous wakes of an upstream Propeller with a downstream contra-Rotating Propeller blade. The study incorporates a two-dimensional model of the upstream Propeller wakes and a quasi-three-dimensional blade response function that accounts for downstream blade sweep. For a blade with a straight leading edge, the sound at the observer location, radiated from each blade radius, consists of a series of impulses whose peaks are shown to be influenced by micro Doppler effects and to correspond to the impingement of the Propeller wake centrelines on the leading edge of the downstream blade. For radiation from the entire blade span, it is shown that constructive interference of the impulses from all radii can produce impulsive sound of very high amplitude, whereas dephasing of these impulses can reduce significantly the total acoustic signal. For a downstream Propeller blade with a swept leading edge, it is shown how the sweep can be designed to ensure that these impulses are de-phased, resulting in significantly lower-amplitude sound at selected observer locations. Finally, to guarantee that the radiated sound is reduced at all possible observer locations, it is shown that the blade leading-edge sweep must be large enough that the trace velocity of the wake centreline, across the leading edge of the downstream Propeller blade, is subsonic across the entire span. The benefits are demonstrated for representative blade designs.
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Acoustic theory of the many-bladed contra-Rotating Propeller: analysis of the effects of blade sweep on wake interaction noise
Journal of Fluid Mechanics, 2019Co-Authors: Michael Kingan, A. B. ParryAbstract:An analytical model is presented for the wake interaction tones produced by a contra-Rotating Propeller. We re-cast the usual far-field radiation formulae as a double integral over a nominal Propeller source annulus. Assuming that the number of blades on both Propellers is large, we evaluate the integral asymptotically in terms of its leading-order contributions from interior stationary or boundary critical points which represent the specific locations on the Propeller annulus that dominate the sound radiation. The asymptotic approach is powerful producing results in the form of one-line algebraic formulae that contain no integrals or special functions yet remain accurate. The asymptotics show that sweep is not necessarily beneficial and can cause the blade design to become critical for particular tones and directions in terms of a continuum of interior points distributed along a line on the Propeller source annulus producing a higher-order result and thus an enhanced radiated sound field. The paper also shows how the interior points are completely consistent with the sub- or super-critical gust response of a swept blade. Tones with low and zero azimuthal mode order are treated as special cases and the asymptotics show that, as the mode order reduces, the radiated sound becomes concentrated around the flight axis where even higher-order solutions are possible, including rings and annuli of stationary points around the Propeller annulus. Full numerical calculations confirm the accuracy of the asymptotic approach.
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Relative importance of open rotor tone and broadband noise sources
17th AIAA CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference), 2011Co-Authors: Michael Kingan, Vincent P. Blandeau, Brian J. Tester, Phillip Joseph, Anthony B. ParryAbstract:A study is made of the noise levels and spectral characteristics of three contra-Rotating Propeller rigs: rig 140 tested in 1989, rig 145 build 1 tested in 2008, and rig 145 build 2 tested in 2010. We use tone deletion techniques, applied to the inflow microphone data, to show the relative importance of Propeller broadband noise to Propeller tones with increasing frequency and, in particular, that by the time we reach only moderate frequencies, the one third octave spectra become dominated by the broadband noise components. We also show that the broadband noise continues to be important as blade speed and rig thrust are varied and that these spectral characteristics are present on both modern and older contra-Rotating Propeller designs – even those with a profusion of tones and strong tone protusion. We also show how the tone and broadband noise levels have reduced with more recent, and aeroacoustically improved, blade designs
Peiqing Liu - One of the best experts on this subject based on the ideXlab platform.
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Performance of Contra-Rotating Propellers for Stratospheric Airships
International Journal of Aeronautical and Space Sciences, 2015Co-Authors: Zhihao Tang, Peiqing Liu, Jingwei Sun, Yaxi Chen, Hao GuoAbstract:Small advance ratio and low Reynolds number of stratospheric propulsion system bring lots of challenges to the design of Propellers. Contra-Rotating Propeller configuration is proposed to improve the propulsion efficiency. In this paper, the feasibility of contra-Rotating Propeller for stratospheric airship has been assessed and its performance has been investigated by wind tunnel tests. The experimental results indicate, at relatively low Reynolds number, although the advance ratio is fixed, the performance of Propellers is different with variation of Reynolds number. Moreover, at the same Reynolds number, the efficiency of contra-Rotating Propeller achieved appears to be a few percent greater than that for a standard conventional propulsion system. It can be concluded that contra-Rotating Propellers would be an efficient means to improve the performance of stratospheric airship propulsion system.
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Experimental Feasibility Assessment of Counter-Rotating Propellers for Stratospheric Airships
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Peiqing Liu, Zhihao Tang, Yaxi Chen, Hao GuoAbstract:A series of systematic wind tunnel tests of a given stratospheric airship counter-Rotating Propeller have been conducted in this paper. The basic aerodynamic performance of the stratospheric airship counter-Rotating Propeller has been explored. In addition, different from conventional Propellers, the effect of low Reynolds number has been illustrated. Compared with single-Rotating Propellers, the interference between front and rear Propeller has also been discussed. The experimental results indicate that low Reynolds number would strongly reduce the efficiency of counter-Rotating Propellers. Due to the interference between a pair of Propellers, the performance of front Propeller gets slightly worse, whereas the performance of rear Propeller turns much better. A significant improvement of efficiency of overall CRP would be gained. By comparison with other configuration of Propeller propulsion system, it indicates the counter-Rotating Propeller would be a wise option applied on stratospheric airships.
Zhihao Tang - One of the best experts on this subject based on the ideXlab platform.
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Performance of Contra-Rotating Propellers for Stratospheric Airships
International Journal of Aeronautical and Space Sciences, 2015Co-Authors: Zhihao Tang, Peiqing Liu, Jingwei Sun, Yaxi Chen, Hao GuoAbstract:Small advance ratio and low Reynolds number of stratospheric propulsion system bring lots of challenges to the design of Propellers. Contra-Rotating Propeller configuration is proposed to improve the propulsion efficiency. In this paper, the feasibility of contra-Rotating Propeller for stratospheric airship has been assessed and its performance has been investigated by wind tunnel tests. The experimental results indicate, at relatively low Reynolds number, although the advance ratio is fixed, the performance of Propellers is different with variation of Reynolds number. Moreover, at the same Reynolds number, the efficiency of contra-Rotating Propeller achieved appears to be a few percent greater than that for a standard conventional propulsion system. It can be concluded that contra-Rotating Propellers would be an efficient means to improve the performance of stratospheric airship propulsion system.
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Experimental Feasibility Assessment of Counter-Rotating Propellers for Stratospheric Airships
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Peiqing Liu, Zhihao Tang, Yaxi Chen, Hao GuoAbstract:A series of systematic wind tunnel tests of a given stratospheric airship counter-Rotating Propeller have been conducted in this paper. The basic aerodynamic performance of the stratospheric airship counter-Rotating Propeller has been explored. In addition, different from conventional Propellers, the effect of low Reynolds number has been illustrated. Compared with single-Rotating Propellers, the interference between front and rear Propeller has also been discussed. The experimental results indicate that low Reynolds number would strongly reduce the efficiency of counter-Rotating Propellers. Due to the interference between a pair of Propellers, the performance of front Propeller gets slightly worse, whereas the performance of rear Propeller turns much better. A significant improvement of efficiency of overall CRP would be gained. By comparison with other configuration of Propeller propulsion system, it indicates the counter-Rotating Propeller would be a wise option applied on stratospheric airships.
