Out-of-Plane Fluidic Actuator for Curved Surface Applications
A novel bistable fluidic actuator design which uses naturally occurring fluid dynamic instabilities instead of moving parts to create an oscillating jet that is out-of-plane from the fluid inlet port.
Turbines are used to produce much of the world’s electricity, whether it be from nuclear, coal, or natural gas sources, as well as provide power for the vast majority of aircraft flying today. For many turbine applications, the first stage vane and blade just downstream of the combustor is a design limiting component. These airfoils must withstand the high temperature and high-pressure gas of the combustor to convert that energy into rotational energy. Attempts to use fluidic oscillators for producing an effective film cooling jet over the turbine blades have been unsuccessful because they cannot be positioned near the leading edge (which is associated with the highest temperatures) due to highly curved geometries. Similarly, attempts to operate various airfoils at a higher angle of attack (with attendant increases in lift performance) through the use of oscillating jets have been stymied. In both cases, the failure of earlier oscillators is due to geometries that don’t facilitate jet output near the leading edge where it is most needed. There is, therefore, a need for a fluidic actuator whose geometry allows the oscillating component to be positioned in more compact areas. Successful technologies would, thereby, extend the lifetime of turbine blades and increase the maximum unstalled angle of attack for numerous airfoil designs.
Researchers at The Ohio State University’s Aerospace Research Center Turbine Aerothermodynamics Lab, led by Dr. Mohammad Arif Hossain, have developed a bistable fluidic actuator that can deliver an oscillating jet 90° out-of-plane from the inlet plane. A jet enters the curved cavity of the design through a pressurized plenum via the inlet nozzle. Once inside the cavity, two vortex modes develop on each side of the chamber. The specialized geometry of the cavity utilizes the Coanda effect to create a feedback loop which alternates the angle of fluid ejection from the outlet, thereby creating an oscillating fluid flow. Due to its ability to work on a curved surface, the actuator may be placed near the leading edge of an airfoil or a turbine blade, providing boundary layer flow control or effective film cooling (respectively). The fluidic actuator has no moving parts and can be integrated into the surface of the turbine blade to aid with cooling of the suction surface. This passive approach does not require independent actuation and can be used in conjunction with other cooling methods to prolong the lifespan of turbine blades.