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CRANFIELD UNIVERSITY Martin Mccarthy CONTRA-ROTATING CRANFIELD UNIVERSITY Martin McCarthy CONTRA-ROTATING OPEN ROTOR REVERSE THRUST AERODYNAMICS SCHOOL OF ENGINEERING MSc by Research Academic Year: 2010 - 2011 Supervisor: Dr D.G.MacManus June 2011 CRANFIELD UNIVERSITY SCHOOL OF ENGINEERING MSc by Research Academic Year 2010 - 2011 MARTIN MCCARTHY CONTRA-ROTATING OPEN ROTOR REVERSE THRUST AERODYNAMICS Supervisor: Dr D.G.MacManus June 2011 © Cranfield University 2011. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. ABSTRACT Reverse thrust operations of a model scale Contra-Rotating Open Rotor design were numerically modelled to produce individual rotor thrust and torque results comparable to experimental measurements. The aims of this research were to develop an understanding of the performance and aerodynamics of open rotors during thrust reversal operations and to establish whether numerical modelling with a CFD code can be used as a prediction tool given the highly complex flowfield. A methodology was developed from single rotor simulations initially before building a 3D‘frozen rotor’ steady-state approach to model contra-rotating blade rows in reverse thrust settings. Two different blade pitch combinations were investigated ( β1,2 =+30˚,- 10˚ and β1,2 =-10˚,-20˚). Thrust and torque results compared well to the experimental data and the effects of varying operating parameters, such as rpm and Mach number, were reproduced and in good agreement with the observed experimental behaviour. The main flow feature seen in all the reverse thrust cases modelled, both single rotor and CROR, is a large area of recirculation immediately downstream of the negative pitch rotor(s).This is a result of a large relative pressure drop region generated by the suction surfaces of the negative pitch blades. An initial 3D unsteady sliding-mesh calculation was performed for one CROR reverse thrust case. The thrust and torque values were in poor agreement with experimental values and the disadvantages relating to time costs and required computational resources for this technique were illustrated. However, the results did yield a nominal unsteady variation of thrust and torque due to rotor phase position. Overall the work shows that it may be possible to develop a CROR reverse thrust prediction tool of beneficial quality using CFD models. The research also shows that the frozen rotor approach can be adopted without undermining the fidelity of the results. Keywords: CFD, propfan, negative pitch, dual propeller, counter-rotating iii ACKNOWLEDGEMENTS I would like to thank Dr David MacManus for his invaluable guidance throughout this rewarding project. He is one of the best educators I have had and his generosity with his time and advice has been greatly appreciated. Although I never expected that my command of the English language would be honed by a Galway man. I wish to thank Rolls Royce for providing experimental data on the topic of this research. Final thanks go to Gill for her love and encouragement as well as my family for their never-ending support, and to all my friends both inside and outside of the Cranfield bubble. iv TABLE OF CONTENTS ABSTRACT ......................................................................................................... iii ACKNOWLEDGEMENTS ................................................................................... iv LIST OF FIGURES ............................................................................................. vii LIST OF TABLES ................................................................................................ ix NOMENCLATURE .............................................................................................. x GREEK SYMBOLS .............................................................................................. xi ACRONYMS ....................................................................................................... xi 1 Introduction .................................................................................................. 1 1.1 Project motivation .................................................................................... 2 1.2 Project description ................................................................................... 3 1.3 Aim and objectives .................................................................................. 4 2 Literature Review .......................................................................................... 5 2.1 Propeller theory ....................................................................................... 5 2.2 Effect of blade angle on propeller performance ........................................... 8 2.3 Propeller performance prediction ............................................................. 11 2.4 Contra-rotating propellers ....................................................................... 15 2.5 Advanced propeller backround ................................................................ 20 2.5.1 Allison 501-M78 ............................................................................. 22 2.5.2 GE-36 UDF .................................................................................... 23 2.5.3 PW-Allison 578DX ......................................................................... 24 2.5.4 Ivchenko Progress D-27 ................................................................... 25 2.5.5 NK-93 ............................................................................................ 26 2.6 Propeller reverse thrust ........................................................................... 27 3 CFD Methodology ....................................................................................... 33 3.1 Investigative approach ............................................................................ 33 3.2 Grid strategy ......................................................................................... 35 3.3 Single rotor simulation ........................................................................... 36 3.3.1 Domain & grid generation ................................................................ 39 3.3.2 Solver settings & turbulence model ................................................... 42 3.3.3 Boundary & zone conditions ............................................................ 43 3.3.4 Iterative convergence ....................................................................... 44 3.3.5 Grid convergence ............................................................................ 45 3.4 Contra-rotation modelling: ‘Frozen Rotor’ approach .................................. 46 3.4.1 Domain & grid generation ................................................................ 47 3.4.2 Solver settings & turbulence model ................................................... 48 3.4.3 Boundary & zone conditions ............................................................ 49 3.4.4 Iterative convergence ....................................................................... 50 3.4.5 Grid convergence ............................................................................ 50 4 Post-processing Methodology ....................................................................... 52 4.1 Rotor performance ................................................................................. 52 4.2 Blade distribution of thrust and torque ..................................................... 52 4.3 CFD contours and streamlines ................................................................. 53 5 Results ........................................................................................................ 55 5.1 Single rotor CFD results ......................................................................... 55 5.1.1 Performance analysis ....................................................................... 55 v 5.1.2 Flowfield assessment ....................................................................... 60 5.1.3 Summary of findings ....................................................................... 62 5.2 CROR frozen rotor CFD and experimental results ..................................... 63 5.2.1 Initial analysis of β1,2 = +30˚, -10˚ ..................................................... 63 5.2.2 Rotor interaction for β1,2 = +30˚, -10˚ ................................................ 69 5.2.3 Mach number variation for β1,2 = +30˚, -10˚ ..................................... 71 5.2.4 Front rotor rpm variation for β1,2 = +30˚, -10˚ ..................................... 76 5.2.5 Aft rotor rpm variation for β1,2 = +30˚, -10˚ ........................................ 82 5.2.6 Summary of findings (CROR at β1,2 =+30˚,-10˚) ................................. 87 5.2.7 Initial analysis for β1,2 = -10˚, -20˚ ..................................................... 88 5.2.8 Mach number variation for β1,2 = -10˚, -20˚ ........................................ 91 5.2.9 Rotor interaction for β1,2 = -10˚, -20˚ ................................................. 95 5.2.10 Aft rpm variation for β1,2 = -10˚, -20˚ ................................................. 97 5.2.11 Summary of findings (CROR at β1,2 =-10˚,-20˚) ................................ 103 5.3 CROR unsteady full rotor CFD results ................................................... 104 5.3.1 Performance analysis ..................................................................... 104 5.3.2 Flowfield assessment ..................................................................... 107 5.3.3
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