A fluidic sensor system for the reliable detection of flow separation at low speed was developed, manufactured and tested in view of flight application.
It comprised an optimised combination of fluidic micro sensors as well as a multichannel measurement system including sensor control and calibration as well as data acquisition and communication electronics.
Starting from different types of fluidic micro sensors and combinations thereof, the sensor system development was performed with the aim to provide a robust and reliable measurement tool for flow control operations in view of flight tests. Ability for flush mounting and easy integration was essential for the sensor front end. The readout electronics should be designed for minimum space and low power consumption. The whole sensor system was examined in view of reducing complexity and was integrated and tested in preparation of a large scale wind tunnel test and in view of flight.
Such a sensor system was expected to be the basis for monitoring and validation of the function of open loop separation control systems and at a later stage the essential control input for future closed loop flow control systems in high lift applications.
These provided a new potential for fuel saving, noise reduction and safety.
The VISION 2020 for European aeronautics is a “greener” aircraft and responds directly to global climate change and the ever increasing need to stay competitive in a global market. Ambitious aims are presented in this document: The 2020 aircraft is quieter and cleaner. A 50% reduction in fuel consumption per passenger kilometre would lead to 50% fewer emissions of CO2. An 80% cut in NOx emissions would significantly reduce the impact of civil air traffic on global warming and the damage to the higher atmosphere. Besides environmental aspects, another important goal for the 2020 aircraft of the European air transport system is their capability of flying safely in all weather conditions and running on schedule 99% of the time. In order to meet this vision leaps in technological developments have to be made. One was the improvement of the high-lift performance of airliners. One approach was the avoidance of turbulent flow separation using active flow control (AFC). An aircraft with an AFC trailing edge flap could depart and approach using steeper trajectories. Furthermore, the take off and landing distances could be shorter and the noise nuisance at ground could be reduced. Other aspects are enhancing maximum take off weight, improving safety, and reducing complexity, weight, and dimensions of flap systems and thereby lowering the direct operating cost (DOC). Those improvements would be beneficial during cruise as well and a reduction of fuel consumption is possible under certain conditions. A modern active flow control system commonly consists of three components: an actuator device that is capable of stabilizing wall-bounded flows in order to delay or suppress flow separation, an intelligent control system to realise to ensure the effective and efficient use of the energy invested, and a fluidic sensor system identify the local state of flow.
The aim of FlowSenSys was to develop such an adequate sensor system, which operates in concert with an active flow control system, while providing robustness and high reliability.
In the first period of this project, various sensors were tested in different flow conditions with and without separation to examine their capability of identifying the flow condition on a generic flap at moderate Reynolds and Mach numbers. The measurements were performed at the end of the first project period. In the second period the focus was on the analysis of the data recorded to evaluate the sensor performance in light of their ability to detect flow separation. Within the third and final reporting period a complex outer wing model was equipped with the most suitable sensor type and wind tunnel experiments were performed in order to validate those sensors' performance under more realistic flow conditions. It was found that the EADS micro-dot surface hot film sensors are capable of detecting the state of flow by evaluating either the DC or the AC signal, which qualifies them to fulfil the requirements imposed on such a flow sensing system.