DEGREE PROJECT IN MECHANICAL ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2020
Study and Design of an Axial Fan Safran Engineering Services / Airbus Helicopters
ALEXIS DORANGE
KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES
Study and Design of an Axial Fan Safran Engineering Services / Airbus Helicopters
Alexis Dorange
Master’s Degree Project Master in Aerospace Engineering
Academic supervisor and examiner: Evelyn Otero Sola Company supervisor: Jean-Christophe Coquillat
KTH Royal Institute of Technology Aeronautical and Vehicle Engineering Department SE-100 44, Stockholm, Sweden
i Abstract
The cooling system is a crucial part for helicopter operations. Without it, hovering flight could not be operated. The cooling system for the main gearbox of a helicopter is composed of radiators and a fan. A fan is an aerodynamic body and as such it can be improved in terms of aerodynamic e ciency. Therefore di↵erent parameters need to be taken into account when designing a new axial fan to have good aerodynamic performance. Simula- tions have been carried out to investigate the e↵ects of these parameters and come up with an optimal design based on the study requirements. The fan has to enable the cooling system to evacuate an amount of thermal power so that the helicopter can take o↵with high outside temperatures. This optimal design has shown an increase of the mass flow rate up to a factor of about two for a given pressure loss compared to the original fan.
ii Referat
Kylsystemet ¨ar en avg¨orande del f¨or en helikopters drift. Utan den kan helikoptern inte hovra. Kylsystemet f¨orhuvudv¨axeln hos en helikopter best˚ar av radiatorer och en fl¨akt. En fl¨akt ¨ar en aerodynamisk kropp och kan d¨arf¨or f¨orb¨attras g¨allande aerodynamisk e↵ektivitet. D¨arf¨orm˚aste olika parame- trar ¨overv¨agasn¨arman utformar en ny axialfl¨aktf¨oratt f˚agod aerody- namisk prestanda. Simuleringar genomf¨ordes f¨or att unders¨oka e↵ekterna av dessa parametrar och komma fram till en optimal utformning baserad p˚a unders¨okningskraven. Denna optimala utformning har visat en ¨okning av massfl¨odet upp till en faktor p˚acirka tv˚af¨oren given tryckf¨orlust j¨amf¨ort med den ursprungliga fl¨akten.
iii Acknowledgements
I wish to thank Mr. HONNORAT, project leader, for welcoming me in his department for this project. I wish to thank particularly Mr. COQUILLAT for mentoring me and guide me throughout this project with good advice, for trusting me to do the best I could and achieve the target fixed. For helping me when I needed help, whether in the professional or the personal domain. IalsothankMr.SERRforhelpingmeduringthetrainee,forhisexpertisein the helicopter domain and for his joy everyday that makes everyone want to work. I wish to thank both of them to have trusted me with this tremendous project and motivated me when I had hard times. I also want to thank Mr. BARRAUD for helping me with CAD software when I was struggling. I want to thank Mr. DELECROIX, Mr. BLANCHARD and Mr. BIANCO for my integration during the first month of my trainee period. I also want to thank all the people in the department for welcoming me and integrate me so quickly in the team. It has been a real pleasure to work with such a devoted and competent team. Finally I wish to thank Ms. OTERO SOLA for her advice, for the help provided and for her time and attention.
iv Contents
1 Introduction 1
2 Background 3 2.1 Safran Engineering Services ...... 3 2.2 AirbusHelicopters ...... 4 2.2.1 History...... 4 2.2.2 H130...... 6 2.3 Basics of aerodynamics ...... 6
3 Methodology 9 3.1 CFDTools...... 9 3.1.1 Governing equations ...... 9 3.1.2 The Case Study ...... 10 3.1.3 Turbulence model ...... 12 3.1.4 WallTreatment ...... 12 3.2 Mesh realization and control ...... 14
4 State Of The Art 18
5Parameterinvestigation 22 5.1 Parameter definition ...... 22 5.2 Blade thickness ...... 24 5.3 Blade angle ...... 25 5.4 Numberofblades ...... 26 5.5 Chord distribution ...... 27 5.6 Deflection ...... 27 5.7 Twisting law ...... 28
6 Fan Design Analysis 29 6.1 Low Power Consumption Based Design ...... 29 6.2 HighMassFlowRateBasedDesign ...... 30
v 6.2.1 New shape of the hub ...... 31 6.3 CFDCorrection...... 31
7 Mechanical Sizing 33 7.1 Beam Theory ...... 33 7.2 FiniteElementAnalysis ...... 34
8 Conclusion 35
vi List of Figures
2.1 Safran Engineering Services Logo...... 3 2.2 EurocopterEC665Tigre...... 4 2.3 Eurocopter logo...... 4 2.4 AirbusHelicopterslogo...... 5 2.5 H160 first pre series exemplar and military model ”Gu´epard”. 6 2.6 H130inflight ...... 6 2.7 Airfoilnomenclature[1]...... 7 2.8 Aerodynamicforces[2]...... 8
3.1 Domain of Computation...... 11 3.2 Torque and axial force created on the fan by air...... 11 3.3 Anexampleoflocalimpermeability...... 14 3.4 Skewness theory illustration with the ideal cell size (green), and the current cell created by the meshing tool (purple). . . . 15 3.5 Example of a skewness correction...... 15 3.6 Section of the volume mesh when cutting horizontally the do- main of computation at the middle of the fan...... 16 3.7 Continuity, velocity, energy, k and epsilon residuals...... 16
4.1 Given CAD (left) and more accurate (right) CAD of the stan- dardfanoftheH130...... 19 4.2 Complete fan (rotor, stator and grid) design with CAD (left) and simplified for CFD computation (right)...... 19 4.3 Target point, working curve of the original fan and aim of the study(thickredline)...... 20 4.4 Comparison between CFD computations and test on the orig- inal fan...... 20 4.5 Comparison of turbulence models in Ansys on the original fan. 21
5.1 Airfoiloftheoriginalfan...... 22 5.2 Thickness and curvature of an airfoil...... 23 5.3 Blade angle and twist t of a fan blade...... 23
vii 5.4 VelocitytrianglefortheH130fan...... 24 5.5 E↵ect of the blade thickness on the mass flow rate and the powerconsumed...... 24 5.6 E↵ect of the blade angle on the mass flow rate and the power consumed by the fan...... 25 5.7 Evolution of mass flow rate (left) and e ciency (right) with respect to the AoA at fixed pressure losses PL1 and PL2. . . . 26 5.8 E↵ect of the number of blades, namely 6 (T1C1 6B) and more than 6 (T1C1 B1) on the mass flow rate and power consumed bythefan...... 26 5.9 E↵ect of chord distribution on the mass flow rate and power consumed by the fan. With T2 the original chord distribution and T2 Chord the new chord distribution...... 27 5.10 E↵ect of the deflection on the mass flow rate and power con- sumed by the fan...... 27 5.11 E↵ect of twisting law on the mass flow rate and power con- sumed by the fan...... 28
6.1 Fan performance for a design based on low power consumption. 29 6.2 Fan performance for a design based on high mass flow rate. . . 30 6.3 Fan performance for a design based on high mass flow rate withanewhub...... 31 6.4 Corrected final design fan performance. The full lines being CFD results and the dashed the test and the scaled final design. 31
7.1 Geometry simplification of a fan blade...... 33
viii Nomenclature
Abbreviations
AH Airbus Helicopters
AoA Angle of Attack
CAD Computer-Aided Design
CETIAT Centre Technique des Industries A´erauliques et Thermiques
CFD Computational Fluid Dynamics
MRF Multiple Reference Frame
N-S Navier-Stokes
RANS Reynolds-Averaged Navier-Stokes
SES Safran Engineering Services
Symbols
↵ Angle of Attack