Self-oscillating-impinging-jet as a gas turbine cooling enhancement system

Impinging jets are widely used in local enhancement of heat removed from internal passages of gas turbine blades. Arrays of stationary jets are usually impinged on inner surfaces of gas turbine blades exposed to severe thermal/hydrodynamic environment of hot mainstream gases. The current practice is to benefit from the high heat transfer coefficients existing in the immediate vicinity of the jet impingement region on a target wall. The present study shows that a self-oscillating impinging-jet configuration can be extremely beneficial in enhancing the heat removal performance of a conventional stationary impinging jet. In addition to a highly elevated stagnation line Nusselt number, the area coverage of the impingement zone is significantly enlarged because of the sweeping motion of the oscillating coolant jet. When an oscillating jet (Re=14,000) is impinged on a plate normal to the jet axis (x/d=24 hole to plate distance), a typical enhancement of Nu number on the stagnation line is shown to be 70 Vo. The present paper explains detailed fluid dynamics structure of the oscillating jet by using a triple decomposition technique on a crossed hot wire signal. High resolution heat transfer measurements are also presented in a Re number range between 7,500 and 14,000 (24<x/d<60). The current heat transfer enhancement levels achieved suggest that it is possible to implement the present self-oscillating-impinging-jet concept in future gas turbine cooling systems, on rotating disks, in electronic equipment cooling, aircraft de-icing systems and heat exchanger systems.