Characterization of a counterflow thrust vectoring scheme on a gas turbine engine exhaust jet

Counterflow thrust vectoring is an innovative technique that uses no movable components to redirect a thrust producing jet. This system relies on fixed curved surfaces and a secondary stream flowing in opposition to the main jet. This paper reports on experimental results of the application of 2-D counterflow tlirust vectoring to the exhaust of a gas turbine engine. Characterization of the jet response to counterflow is presented for different secondary flow gaps. Continuous and proportional control of the jet was demonstrated for vectoring angles up to 25°. The jet attaches to the collar wall for high counterflow levels. The secondary mass flux needed to vector the main jet is less than 6% before attachment, with thrust losses below 8%. The temperature in the vacuum line rises to the point where special caution must be taken when operating electronically controlled valves, which also proved to be affected by pressure losses in the vacuum line. Regarding the system dynamic response, a slew rate of 160°/s was observed. However, the counterflow thrust vectoring system operates in a very inhospitable environment regarding noise and interference, which degrades the measurement for high sampling rates. Based on these results an optimal gap size of 0.625 times the nozzle height was chosen for further studies concerning shear layer mixing enhancement, dynamics and controls.