Aerodynamic and Structural Analysis of the Kaman K-16B

Healy, Elizabeth; Daly, Shannon; Heginbotham, Naoki; Punjabi, Viren; Yarlagadda, Akhilesh; Shirakura, Douglas; Ogbebor, Cyril; Carlton, Andrew

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Aerodynamic and Structural Analysis of the Kaman K-16B

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The Kaman K-16B was an experimental aircraft that was significant in the development of aircraft capable of Vertical or Short Takeoff and Landing (V/STOL). In the 1950s, the K-16B was developed by the Kaman Corporation in partnership with the United States Navy as a prototype to test the ability of a propeller with flaps on each blade, partially tilting main wing, and full-span wing flaps to achieve and improve upon common V/STOL performance problems of the time. The only existing K-16B is stored at the New England Air Museum (NEAM) in Windsor Locks, CT. This work presents a study to evaluate the thrust performance of the K-16B’s unique “rotoprops” as well as the induced stresses on the rotoprop blades when operating over a range of blade pitch and collective flap deflection angles. The thrust analysis was performed using a computational fluid dynamic (CFD) simulation whereas the structural analysis was performed using finite element analysis (FEA). The fact no digital model of the rotoprops exist posed a unique challenge as one had to be created to perform the CFD and FEA. The methodology used to create the solid models used a combination of archival plans, that were photographed and imported into SolidWorks as 2D “sketches,” in addition to onsite measurements of key components. These 2D digital sketches were then used to create the 3D geometry for the solid model. The solid model was imported into Ansys Fluent, where the thrust was evaluated at blade pitch angles of 15, 30, and 45 degrees, collective flap angles of 0 and 13 degrees, and a rotational velocity of 725 rpm. Results support a finding that the K-16B with its tilted wing could have produced sufficient thrust to takeoff over a short distance with the blade pitch set at 30 and 45 degrees, regardless of the collective flap angle. Results also showed that the thrust decreases with collective flap angles of 7 and 13 degrees. These findings are presented and discussed. For the structural analysis, we calculated the equivalent stresses in simplified rotoprop blade model that included a central, metal actuator control rod with a primary blade structure and collective flap made of spruce. Stresses were evaluated using a combination of static pressure loads, calculated in the Fluent simulations, and centrifugal stresses on the material due to the blade rotation. Considering the combined effects of pitch angle and collective flap angle on the stress distribution, the least stress-inducing case from the seven cases run was the 30-degree pitch angle and 7-degree collective flap angle. These results, including the location of peak stresses for each case are presented and discussed. In addition to the results of numerical analysis using CFD and FEA, an analysis of the takeoff performance of the K-16B was attempted using a standard analytical methodology. Despite access to numerous archival reports documenting the aircraft performance and test history, we were not able to locate all the performance coefficients that would be needed to apply the analytical approach to this unique aircraft, specifically because of complexity related to the tilted wing, large wing flaps, and unknown thrust coefficients for the rotoprop. Finally, we evaluated the use of 3D scanning technology as an alternative approach to create a solid model of structures several feet in length and completed the preliminary design of a translating tripod for blueprints (TTB). The need for a TTB became evident as the team photographed large format blueprints onsite at the museum using a conventional tripod. This work is summarized in the report.

This report represents the work of one or more WPI undergraduate students submitted to the faculty as evidence of completion of a degree requirement. WPI routinely publishes these reports on its website without editorial or peer review.

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