T HE E XPERIMENTAL I NVESTIGATION OF A R OTOR I CING M ODEL WITH S HEDDING Presentation to NASA Icing Branch April 8, 2010 Edward Brouwers Graduate Research Assistant The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Agenda • Background/Motivation • ARISP Rotor Icing Model • Understanding AERTS • ARISP Correlations to AERTS Experiments • Conclusions & Recommendations for Future Work The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Motivation • Flight into Icing Conditions is Dangerous – Reduced vehicle performance • Torque Rise • Stability & Control Issues • Excessive Vibration • Operational Limitations – Simply avoid ice – Few aircraft have limited icing clearances – Fewer have IPS • Rotorcraft Compounding Factors – Mission Urgency – Mission Profile – Vehicle Sensitivity to Ice – Shedding The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Rotor Icing Analysis • Test Facilities – NRC Helicopter Spray Rig – McKinley Climatic Chamber – NASA IRT – Army HISS • Modeling – Complex problem – No comprehensive model – Lack of validation data • Open Issues NASA Photo C-1993-3962 – Oscillatory Airfoils – Tip Shape Effects The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Research Objectives • Develop Rotor Icing Model (ARISP) • Develop Icing Test Facility (AERTS) • Correlate ARISP Model to Experiments in AERTS Facility The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Agenda • Background/Motivation • ARISP Rotor Icing Model – Program Design – Shedding/Performance Implementation – Validation • Understanding AERTS • ARISP Correlations to AERTS Experiments • Conclusions & Recommendations for Future Work The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
AERTS Rotor Icing, Shedding and Performance (ARISP) Model • Objectives – Aid AERTS Calibration – Uncover Icing Trends – Supplement NRA Activity • Simplified version of icing analysis effort • Primary Features – Prediction of ice accretion on rotor systems – Predict performance degradation – Evaluates effects of ice shedding – Provide interface for ice protection system evaluation The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Program Setup • Overall Setup – Analysis centered on the LEWis ICE Accretion Program (LEWICE) • Industry standard icing modeling software – extensively validated in IRT • ARISP uses LEWICE 3.0 – 2D version – Pre and post processing written in MATLAB – Generally similar to work by: • Britton, “Development of an Analytical Method to Predict Helicopter Main Rotor Performance in Icing Conditions, AIAA 92-0418 • Miller et al, “Analytical Determination of Propeller Performance Degradation Due to Ice Accretion” J. Aircraft Vol. 24 No. 11 • Fortin and Perron, “Spinning Rotor Blade Tests in Icing Wind Tunnel” AIAA 2009-4260 • Concept – Quasi-2D Analysis • Rotor performance calculated in BEMT • Ice accretions calculated at each station – Focused on hover due to AERTS Facility limitations The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Overall Program Flow Loop Until Analysis Complete The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
LEWICE Interface • Program Inputs – Rotor Geometry • Blade profile • Station properties (airfoil, material) • Analysis stations – Icing Conditions • LWC function of rotor radius • Mono-dispersed droplet distribution assumed • Ramping of temperature/LWC • Software Coupling – LEWICE time stepping logic is used to size number of analysis steps – Inputs for each station/timestep are created automatically • Airfoil Geometry – clean/iced airfoil • Icing Conditions – spanwise gradients in LWC etc – Series of batch files connect MATLAB and LEWICE • LEWICE runs “inside” of MATLAB script • ~0.5 seconds per LEWICE run • High fidelity test run requires about 10 minutes The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
ARISP BEMT Validation Dry BEMT Module Comparison Dry BEMT Module Comparison vs Prouty Tail Rotor vs NASA CR 2275 • BEMT currently corrected for AERTS Chamber per NASA TM 86754 • C81 Performance tables for NACA 0012, NACA 0015 included in ARISP The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
ARISP Ice Accretion Comparisons Model Scale • Model Scale – NASA TM 103712 • Tests conducted in NASA IRT (1989) – 6’ diameter NACA 0012 generic rotor – Ice tracings published at various rotor stations for many icing conditions – Rotor trimmed in ARISP model to match average station AoA The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Full Scale ARISP Ice Shape Validation • Full Scale – NASA CR 168332 – Tests conducted at Canadian NRC Helicopter Spray Rig with UH-1H – Results from Flight E Documented – Conditions • Temperature corrected from -19°C to -14°C • LWC = 0.7 gr/m 3 • MVD = 30 µm • Time = 3 min The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Ice Extent Calculations • Method of determining spanwise ice accretion – Based upon static temperature and ram temperature rise – Assumes thermodynamic recovery factor per NASA CR 3910 f ( LWC , M ) – Model validated to CR 3910 and UH-1H HIFT Data Validation Current Research The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Ice Accretion Comments • Overprediction of Ice at Rotor Tips NASA TM 103712 – Opposite of expectations – Seen in previous research • NASA TM 107312 • Gent, “Further Studies of Helicopter Rotor Ice Protection Accretion and Protection” Vertica Vol 11 Issue 3, 1987 – May be related to droplet bounce, centrifugal effects and LWC gradients – Shedding • 2D nature of shedding analysis may miss shedding of glaze ice horns The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Performance Degradation • Modeling – Primary metric is rotor torque • Dependent on sectional drag coefficients Gray Bragg Flemming • Lift degradation small Temperature ( ° C) – Empirically modeled based upon min -17.7 -17.7 -20.0 max -3.8 -12.2 7.7 published correlations MVD (µm) • Bragg’s and Flemming’s Correlations min 11.3 7.0 11.0 max 19.0 19.0 50.0 currently included in ARISP LWC (gr/m 3 ) • Implementation min 0.39 0.50 0.24 max 2.00 1.86 3.80 – Dynamic database of sectional drag Velocity (ft/sec) min 183.3 256.6 287.7 coefficients max 403.3 403.3 745.1 Icing Time (min) • Updated after each time step with Δ C d min 3.0 1.0 0.3 • If shedding occurs, clean airfoil max 17.7 27.0 5.0 performance is used The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Shedding Implementation A Differential Ice Element Ω A Analysis Direction Net Aerodynamic Ice Forces Force (negligible) Shear Adhesion Force Cohesion Force Z Y Centrifugal Force X Section A-A The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Shedding Progression The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Ice Details Ice Cross Typical Ice Shape, assumed quasi 2D Sectional Area Z s hi Impingement Limits X Y Calculated from s low LEWICE Centrifugal Force Ice Adhesion Area • Impingement Limit Tracker – Furthest aft impingement limits selected for each station (updated each time step, reset after shedding event) – Glaze ice feathers • Cross Ice Area Summation – Area calculated by LEWICE (integration of thickness) – Summed for each timestep, reset after shedding event The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
ARISP Model Loop Until Analysis Complete The Vertical Lift Research Center of Excellence Adverse Environment Rotor Test Stand
Recommend
More recommend
