Acoustic Analysis of Counter-Rotating Open Rotors with a Locked Blade Row
Abstract
Counter-rotating open rotors (CRORs) have the potential to reduce environmental emissions thanks to their high propulsive efficiency. However, there are a number of concerns surrounding their acoustic emissions. This contribution presents a novel multiconfiguration CROR that offers considerable noise reductions. In particular, locking either the fore or aft rotor during takeoff is considered, with the running rotor providing the required thrust. During cruise, both rotors are operated to retain the high efficiency of the CROR. A coupled computational fluid dynamics/computational aeroacoustics analysis has shown the potential of this multiconfiguration concept to offer substantial noise reductions when compared to a baseline CROR. During a simulated constant-altitude flyover at takeoff conditions, reductions of 3.5 and 7.9 dBA have been demonstrated when either the fore or aft row is locked, respectively. Using the effective perceived noise level metric, this result corresponded to 7 and 12 Effective Perceived Noise Level (in Decibels), respectively, for the same flyover.
References
[1] , “Progress in Open Rotor Research: A U.S. Perspective,” ASME Turbo Expo 2015, ASME, New York, 2015, pp. 1–0. https://doi.org/10.1115/GT2015-42203
[2] , “On the Influence of Trailing-Edge Serrations on Open-Rotor Tonal Noise,” 18th AIAA/CEAS Aeroacoustics Conference, AIAA Paper 2012-2124, 2012. https://doi.org/10.2514/6.2012-2124
[3] , “Optimization of Trailing-Edge Serrations to Reduce Open-Rotor Tonal Interaction Noise,” Journal of Fluids Engineering, Vol. 140, No. 2, 2018, pp. 1–8. https://doi.org/10.1115/1.4037981
[4] , “Aerodynamic and Acoustic Impacts of a Single Protuberance Placed on the Leading Edge of the Front Blades of an Open Rotor,” 48th International Symposium of Applied Aerodynamics of Small Bodies and Details, Saint Louis, France, 2013.
[5] , “Open Rotor Interaction Noise Reduction Through Front Rotor Wake Modification,” International Journal of Aeroacoustics, Vol. 15, Nos. 1–2, 2016, pp. 207–227. https://doi.org/10.1177/1475472X16643461
[6] , “Open Rotor Designs for Low Noise and High Efficiency,” Proceedings of the ASME Turbo Expo, Vol. 6 C, ASME, New York, 2013, pp. 1–0. https://doi.org/10.1115/GT2013-94736
[7] , “Assessment of Front-Rotor Trailing-Edge-Blowing for the Reduction of Open Rotor Noise Emissions,” 19th AIAA/CEAS Aeroacoustics Conference, AIAA Paper 2013-2200, 2013. https://doi.org/10.2514/6.2013-2200
[8] , “Active Flow Control for Interaction Noise Reduction of Contra-Rotating Open Rotors,” 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, AIAA Paper 2013-3799, 2013. https://doi.org/10.2514/6.2013-3799
[9] , “Multidisciplinary Analysis of CROR Propulsion Systems: DLR Activities in the JTI SFWA Project,” CEAS Aeronautical Journal, Vol. 5, No. 3, 2014, pp. 265–277. https://doi.org/10.1007/s13272-014-0105-4
[10] , “Assessment of Front Rotor Trailing Edge Blowing for the Reduction of Open Rotor Interaction Noise,” New Results in Numerical and Experimental Fluid Mechanics IX, Vol. 124, Notes on Numerical Fluid Mechanics and Multidisciplinary Design, Springer, New York, 2014, pp. 609–618. https://doi.org/10.1007/978-3-319-03158-3_62
[11] , “Active Flow Control for Interaction Noise Reduction of Contra-Rotating Open Rotors,” AIAA Journal, Vol. 54, No. 4, 2016, pp. 1413–1423. https://doi.org/10.2514/1.J053756
[12] , “Contrarotating Open Rotor Operation for Improved Aerodynamics and Noise at Takeoff,” Journal of Turbomachinery, Vol. 135, No. 3, 2013, Paper 031010. https://doi.org/10.1115/1.4006778
[13] , “Influence of Torque Ratio on Counter-Rotating Open-Rotor Interaction Noise,” AIAA Journal, Vol. 53, No. 9, 2015, pp. 2726–2738. https://doi.org/10.2514/1.J053797
[14] “Propeller-Driven Aeroplanes Not Exceeding 8 618 kg,” ICAO Annex 16: Environmental Protection, Vol. 1, Aircraft Noise, International Civil Aviation Organization, Montreal, 2011, Chap. 10.
[15] , “Multi-Disciplinary Simulation of Propeller-Turboprop Aircraft Flight,” Aeronautical Journal, Vol. 116, No. 1184, 2012, pp. 985–1014. https://doi.org/10.1017/S0001924000007454
[16] , “Aircraft Noise: Noise Sources,” Advanced Aircraft Flight Performance, Cambridge Univ. Press, New York, 2012, pp. 470–532. https://doi.org/10.1017/CBO9781139161893
[17] , “Wind Tunnel Performance of Four Energy Efficient Propellers Designed for Mach 0.8 Cruise,” NASA TM-79124, 1979. https://doi.org/10.4271/790573
[18] , “Low Order Multidisciplinary Optimisation of Counter-Rotating Open Rotors,” European Rotorcraft Forum, Delft, The Netherlands, 2018, Paper 38.
[19] , “Development of CFD Capability for Full Helicopter Engineering Analysis,” 31st European Rotorcraft Forum, Florence, Italy, 2005, Paper 91.
[20] , “A Framework for CFD Analysis of Helicopter Rotors in Hover and Forward Flight,” International Journal for Numerical Methods in Fluids, Vol. 51, No. 8, 2006, pp. 819–847. https://doi.org/10.1002/fld.1086
[21] , “Towards Consistent Overset Mesh Methods for Rotorcraft CFD,” International Journal for Numerical Methods in Fluids, Vol. 74, No. 8, 2014, pp. 543–576. https://doi.org/10.1002/fld.3861
[22] , “An Arbitrary Lagrangian–Eulerian Computing Method for All Flow Speeds,” Journal of Computational Physics, Vol. 135, No. 2, 1997, pp. 203–216. https://doi.org/10.1006/jcph.1997.5702
[23] , “Two-Equation Eddy-Viscosity Turbulence Models for Engineering Applications,” AIAA Journal, Vol. 32, No. 8, 1994, pp. 1598–1605. https://doi.org/10.2514/3.12149
[24] , “Upwind Schemes and Boundary Conditions with Applications to Euler Equations in General Geometries,” Journal of Computational Physics, Vol. 50, No. 3, 1983, pp. 447–481. https://doi.org/10.1016/0021-9991(83)90106-7
[25] , “Towards the Ultimate Conservative Difference Scheme. V. A Second-Order Sequel to Godunov’s Method,” Journal of Computational Physics, Vol. 32, No. 1, 1979, pp. 101–136. https://doi.org/10.1016/0021-9991(79)90145-1
[26] , “A Comparative Study of Computational Methods in Cosmic Gas Dynamics,” Astronomy and Astrophysics, Vol. 108, No. 1, 1982, pp. 76–84. https://doi.org/10.1007/978-3-642-60543-7_6
[27] , Iterative Solution Methods, Cambridge Univ. Press, New York, 1994, pp. 504–557. https://doi.org/10.1016/j.apnum.2004.06.003
[28] , “Computational Aeroacoustic Analysis of Propeller Installation Effects,” 43rd European Rotorcraft Forum, Milan, Italy, 2017, Paper 521.
[29] , “Tiltrotor CFD Part I–Validation,” Aeronautical Journal, Vol. 121, No. 1239, 2017, pp. 577–610. https://doi.org/10.1017/aer.2017.17
[30] , “Low-Speed Wind-Tunnel Tests of Single- and Counter-Rotation Propellers,” NASA TM-87656, 1986.
[31] , “Linear Acoustic Formulas for Calculation of Rotating Blade Noise,” AIAA Journal, Vol. 19, No. 9, 1981, pp. 1122–1130. https://doi.org/10.2514/3.60051
[32] , “Sound Generation by Turbulence and Surfaces in Arbitrary Motion,” Philosophical Transactions of the Royal Society of London, Series A: Mathematical, Physical and Engineering Sciences, Vol. 264, No. 1151, 1969, pp. 321–342. https://doi.org/10.1098/rsta.1969.0031
[33] , “Relative Importance of Open Rotor Tone and Broadband Noise Sources,” 17th AIAA/CEAS Aeroacoustics Conference 2011 (32nd AIAA Aeroacoustics Conference), AIAA Paper 2011-2763, 2011. https://doi.org/10.2514/6.2011-2763
[34] , “Open Rotor Broadband Interaction Noise,” Journal of Sound and Vibration, Vol. 332, No. 17, 2013, pp. 3956–3970. https://doi.org/10.1016/j.jsv.2013.03.014
[35] , “Counter-Rotating Propeller Noise Directivity and Trends,” AIAA 10th Aeroacoustics Conference, AIAA Paper 1986-1927, 1986. https://doi.org/10.2514/6.1986-1927
[36] , “Propeller Performance,” Advanced Aircraft Flight Performance, Cambridge Univ. Press, New York, 2012, pp. 152–178, Chap. 6.
[37] , “Analysis of Advanced Open Rotor Noise Measurements,” 20th AIAA/CEAS Aeroacoustics Conference, AIAA Paper 2014-2745, 2014. https://doi.org/10.2514/6.2014-2745
[38] , “Counter-Rotation Propeller Tip Vortex Interaction Noise,” 15th AIAA/CEAS Aeroacoustics Conference (30th AIAA Aeroacoustics Conference), AIAA Paper 2009-3135, 2009. https://doi.org/10.2514/6.2009-3135
[39] , “An Objective Definition of a Vortex,” Journal of Fluid Mechanics, Vol. 525, Feb. 2005, pp. 1–26. 10.1017/S0022112004002526