The overall aim of this project was a novel approach for increased sensitivity of laminar wings to ice accretion in all flight phase. The CfP topic will therefore address three main objectives:
- Development of a system architecture model for an active ice protection system;
- Development of innovative sensing options to support the active ice protection strategy;
- Overall aircraft model that demonstrates the effectiveness of the new ice protection system.
The wing of an aircraft is a key component to improved noise and efficiency characteristics of today's air transport. Yet, airplane wings are prone to and adversely affected by the formation of ice on their surface, which seriously compromises flight safety. The detection of ice on the wing surface and the existence of a reliable de-icing concept are therefore essential, especially for new laminar wing concepts that are particularly sensitive to the presence of ice.
Whilst current ice-detection systems use a remotely mounted probe to assess ice accretion, the approach of the Clean Sky JU project InAIPS was based on aero-conformal optical ice detection sensors, which are integrated directly into the leading edge of the wing at the relevant portions for ice accretion. The project tackled the problem of ice-accretion on a laminar flow wing with a semi-empirical approach, using measurements as well as mathematical modelling. The developed system model was assembled of data from the optical sensors, an ice detection algorithm determining ice thickness and ice type from the sensor data, and aerodynamic simulations to estimate the lift and drag forces on the wing section.
The response of the sensors to the ice accretion was measured as an electrical signal which depends on the intensity of reflections and backscattering from the ice. To capture the ice accretion under different flight conditions in terms of angle of attack, two optical sensors were installed on the wing, one on the stagnation line looking forward and the other angled upwards. The signals were then processed with an Ensemble-Kalman-filter based algorithm, which translates the signal into ice thickness and ice type, the latter depending on the outside air temperature. From data constituted from wind tunnel experiments within the project, a best estimate for the corresponding ice shape and angle of attack was determined. Based on this information, lift and drag forces on the wing sections including ice were evaluated using CFD simulations. With this information, the impact of the icing at a wing section on the asymmetry of the wing can be assessed under different flight conditions.
In conjunction with the aero-conformal ice detector developed in the EU FP7 projects ACIDS and ON-WINGS, the evaluation of the ice shapes in different flight conditions and the simulations of their impact on the aerodynamic behaviour of the entire airplane enabled the setup of a full system model for ice accretion and ice detection. Putting all pieces together a system model for icing and its impact on the wing performance was attained. In combination with a de-icing process it was an approach to a primary, closed-loop control system for ice protection.