Propellers. Modeling Conforming Folding. OpenVSP Workshop PM Thursday, August 31, Joseph Derlaga NASA LaRC, CAB

Transcription

1 Modeling Conforming Folding Propellers OpenVSP Workshop PM Thursday, August 31, 2017 Brandon Litherland NASA LaRC, ASAB Michael Patterson NASA LaRC, ASAB Joseph Derlaga NASA LaRC, CAB Nicholas Borer NASA LaRC, ASAB

2 Introduction The X-57 Maxwell, NASA s next manned X-plane, uses relatively small diameter, distributed, electrically-driven propellers that provide lift augmentation at low speeds. Image Source: NASA brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

3 Motivation Video Source: NASA Modeling Conforming Folding Propellers OpenVSP Workshop of 32

4 Motivation Takeoff & Climb: High-Lift Propellers Active Modeling Conforming Folding Propellers OpenVSP Workshop of 32

5 Motivation Cruise: High-Lift Propellers Stowed Modeling Conforming Folding Propellers OpenVSP Workshop of 32

6 Objectives Image Source: NASA 1. No appreciable performance losses from non-folding blade design. 2. Single-axis folding mechanism. 3. Blades designed to emphasize performance over conformity. 4. Blades should be able to smoothly conform to the nacelle. 5. Applies to most blades about axisymmetric body Modeling Conforming Folding Propellers OpenVSP Workshop of 32

7 Modification First steps: Choose a driving blade location Determine the folding parameters a Φ Folding axis,, and folding angle,. brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

8 Modification First steps: Choose a driving blade location Determine the folding parameters a and Φ Unfolded Blade Configuration (away from nacelle) Thrust Blade Rotation brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

9 Modification First steps: Folded Blade Configuration (along nacelle) Choose a driving blade location Determine the folding parameters a and Φ brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

10 Modification First steps: Choose a driving blade location Determine the folding parameters a and Φ brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

11 Modification Front First View steps: Choose a driving blade location Determine the folding parameters a Φ Folding axis,, and folding angle,. Top View Side View Perspective View brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

12 Modification Conforming the blade to the nacelle Adjust rake and skew such that Local chord is tangent to the nacelle surface, and Rotating blade incidence to air remains unchanged Adjust rake to achieve desired blade depth Stowed Blade Configuration Modeling Conforming Folding Propellers OpenVSP Workshop of 32

13 Modification Conforming the blade to the nacelle Adjust rake and skew such that Local chord is tangent to the nacelle surface, and Rotating blade incidence to air remains unchanged Adjust rake to achieve desired blade depth Stowed Blade Configuration Modeling Conforming Folding Propellers OpenVSP Workshop of 32

14 Modification Conforming the blade to the nacelle Adjust rake and skew such that Local chord is tangent to the nacelle surface, and Rotating blade incidence to air remains unchanged Adjust rake to achieve desired blade depth Modeling Conforming Folding Propellers OpenVSP Workshop of 32

15 Modeling Open Vehicle Sketch Pad (OpenVSP) includes a Prop component that uses the design parameters required to model the folding blade. brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

16 Modeling Open Vehicle Sketch Pad (OpenVSP) includes a Prop component that uses the design parameters required to model the folding blade. brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

17 Modeling Under the Blade tab, the user defines the radial distribution of chord, twist, rake, and skew. The lofting between control points is performed using a linear, Cubic Bezier, or PCHIP interpolation. brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

18 Modeling The folding axis, a = {a x, a y, a z } can be translated into OpenVSP Prop parameters using geometric relationships. The folding angle, Φ, is equivalent to Angle. Radial/R sets the hinge location relative to the propeller center of rotation. Using neg. a to determine axis. brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

19 Modeling The user can alter almost any blade design to conform to an axisymmetric surface. Below are two different blade designs attached to the same nacelle. Notional X-57 high-lift propeller MIL propeller blades Modeling Conforming Folding Propellers OpenVSP Workshop of 32

20 Modeling 1. Demonstration 2. Files Modeling Conforming Folding Propellers OpenVSP Workshop of 32

21 Performance The unmodified and folding blade performances were simulated using OVERFLOW (OVERset grid FLOW solver). Blade performances were compared using induced velocity profiles as this is strongly tied to the wing lift augmentation. Modeling Conforming Folding Propellers OpenVSP Workshop of 32

22 Performance Takeoff Conditions 4549 RPM The images below show a geometric comparison between the unmodified baseline blade (left) and the folding blade (right). 58 KCAS 0 Nacelle AoA 3,300 lb target lift brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

23 Performance Takeoff Conditions 4549 RPM 58 KCAS 0 Nacelle AoA 3,300 lb target lift These images show the blade and nacelle pressure coefficient and the axial velocity distribution halfway along the nacelle. brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

24 Performance These images show the circumferentially-averaged axial velocity distributions at four locations downstream of the propeller disk. We found that the folded-blade velocity profiles almost exactly match those of the unmodified blade. Modeling Conforming Folding Propellers OpenVSP Workshop of 32

25 Performance Parameter Unmodified Blade Folding Blade % Change Thrust (N) % Power (kw) % Torque (N-m) % Avg. Axial ΔV (m/s) % Very little performance loss by modifying the propeller for folding. Less than 4% difference in power and torque. Approximately 2% difference in thrust and average axial velocity. A slight increase to the propeller RPM could likely equate these values to the unmodified propeller performance. brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

26 Prototype A functional model was created to include folding, rotating blades. Model generation and fit checks performed in PTC Creo CAD suite The model was manufactured using 3-D printing resources at NASA LaRC. re:3d Gigabot and LulzBot Taz-6 printers PLA filament from various suppliers in several colors brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

27 Prototype Modeling Conforming Folding Propellers OpenVSP Workshop of 32

28 Prototype Modeling Conforming Folding Propellers OpenVSP Workshop of 32

29 Conclusions Initial blade designed for performance over conformity. Produces nacelle-conforming, single-axisfolding propeller blades. Minimal performance loss compared to unmodified baseline blade. Method is systematic and lends itself to diverse designs and automation. Future Work Incorporate folding and conformity into propeller and nacelle design space Automate the design process from known propeller geometry Conduct additional study of folding blade performance comparisons Experiment with physical models to verify the computational performance results Modeling Conforming Folding Propellers OpenVSP Workshop of 32

30 Acknowledgments NASA s Aeronautics Research Mission Directorate Transformational Aeronautics Concepts Program Convergent Aeronautics Solutions Project Transformational Tools and Technologies Project Integrated Aviation Systems Program Flight Demonstrations and Capabilities Project SCEPTOR Subproject Advanced Air Vehicle Program Revolutionary Vertical Lift Project brandon.l.litherland@nasa.gov Modeling Conforming Folding Propellers OpenVSP Workshop of 32

31 Reference Much of the material for this presentation is sourced from the associated paper and presentation for AIAA Aviation Brandon L. Litherland, Michael D. Patterson, Joseph M. Derlaga, and Nicholas K. Borer. "A Method for Designing Conforming Folding Propellers", 17th AIAA Aviation Technology, Integration, and Operations Conference, AIAA AVIATION Forum, (AIAA ) Modeling Conforming Folding Propellers OpenVSP Workshop of 32

32 Thank you! Questions? Brandon Litherland NASA LaRC, ASAB Michael Patterson NASA LaRC, ASAB Joseph Derlaga NASA LaRC, CAB Nicholas Borer NASA LaRC, ASAB