MODELING AND EXPERIMENTAL TESTING OF A HYBRID IMPULSIVE-PNEUMATIC DE-ICING SYSTEM
Open Access
- Author:
- Forry, Carter Michael
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 10, 2019
- Committee Members:
- Jose Palacios, Thesis Advisor/Co-Advisor
- Keywords:
- De-icing
icing
impulsive
pneumatic - Abstract:
- This thesis designed and fabricated a scaled hybrid impulsive-pneumatic aircraft de-icing system. This system deformed a 0.01-in thick stainless steel leading edge shell producing transverse shear stresses capable of delaminating accreted ice. The system used pneumatic and impulsive aspects which together reduce the pressure required to delaminate accreted ice. Like a traditional pneumatic de-icing system, pressure is applied which deforms the shell around the leading edge. The impulsive aspect of the system constrains and releases two portions of the deformable shell, adding beneficial inertia effects. The impulsive sections of the deformable shell are constrained using electromagnets that can be precisely controlled using a microcontroller. The electromagnets can release the two portions of the shell in a symmetric or asymmetric fashion. A symmetric inflation releases the constraints on both sides of the airfoil at the same time while an asymmetric inflation releases one constraint and then the other after a controllable period. The hybrid de-icing system was tested at The Pennsylvania State University’s Adverse Environment Research Test Systems Icing Tunnel. The de-icing system, which uses static and impulsive aspects, was able to delaminate ice with a leading edge thickness in the range 0.11-in to 0.32-in with as little as 2.5 psi using the dynamic asymmetric inflation technique. The static inflation technique, which is widely used on small aircraft, alone was unable to delaminate the accreted ice for any leading edge ice thickness. A finite element analysis model was used to assist in the design of the physical hybrid impulsive-pneumatic de-icing system. Aspects of the physical hybrid de-icing system such as that electromagnet placement and propagation times are determined by the FEA model. The FEA model was inherently dynamic which was a new technique that was not implemented in previous literature. The ice/shell bonding interaction was simulated in Abaqus using cohesive zone methods. The model is mesh dependent due to the cohesive zone method used; therefore, interaction properties from separate experiments are used to characterize the cohesive behavior. A bench top flat plate experiment was conducted to experimentally determine a cohesive surface modulus for the 410 stainless steel. The flat plate device used the same stainless steel as the scaled hybrid system. Freezer ice was bonded to the flat plate and the pressure required to completely delaminate a range of ice thicknesses was recorded. Using the pressure values from the flat plate bench-top experiments, the FEA model’s cohesive surface modulus was corrected to yield the same delamination results. With the correct stainless steel cohesive surface modulus, the flat plate and FEA model required pressures differ on average by 23% for symmetric inflation and 20% for asymmetric inflation. Stress-strain laws were shown to be consistent between the FEA model and the flat plate bench-top experiment by comparing the deflection at the center of the plate. At a pressure less than 2 psi, the maximum percent difference between the model and experimental plate deflection was approximately 2%. The FEA model was used to compare impulsive shell inflation techniques: static, symmetric, and asymmetric. The performance of each technique was quantified by tracking the nodal separation of the ice and shell and the greatest nodal separation yielded the greatest de-icing potential. For the asymmetric inflation case, the FEA model was used to determine the time between shell constraints being released which result in the greatest nodal separation. The same cohesive behavior used in the flat plate FEA model was then implemented onto a NACA 0024 airfoil section. This FEA model was then used to predict ice delamination for the airfoil de-icing system icing tunnel tests. The FEA model was corrected to account for asymmetric drag during icing tunnel testing. Using the asymmetric drag correction, the percent difference between the FEA model and experimental results was approximately 18% for ice which did not fracture after pressure was applied.