Experimental and Computational Investigation of a Dual-Throat Fluidic Thrust-Vectoring Nozzle

The dual-throat fluidic thrust-vectoring nozzle concept is of particular interest because of its ability to provide large vector angles with minimal losses in thrust. This work investigates the performance of a dual-throat fluidic thrust vectoring nozzle over a range of three secondary injection geometries: two (V1, V2) spanwise oriented rectangular slots of different thicknesses and (V3) a single spanwise oriented array of circular holes. Baseline testing at a nozzle pressure ratio (NPR) of 2 showed that the presence of the injection geometry alone had a noticeable impact in vectoring the primary flow. Specifically, the smaller slot, larger slot, and hole geometries deflected the primary flow by 2, 0.5 and 4 degrees, respectively. When secondary injection was introduced the smaller slot displayed better vector performance across the entire range of secondary injection mass flow rates as compared to the larger slot configuration. The circular hole geometry was less effective at low secondary injection flow rates, but came close to surpassing the performance of both slot geometries at 5% secondary injection. Increasing the NPR to 4 for all three cases greatly reduced the influence of the secondary injection geometry on the baseline nozzle performance. Specifically, the smaller slot geometry displayed a drop in thrust vectoring angle from 12 to 8 degrees when NPR was increased from 2 to 4. Finally, using the experimental and computational data collected during this study, a method was developed to predict vector angle from the wall static-pressure distributions internal to the nozzle. This was accomplished through integrating the pressure profiles, applying a correction factor derived from computational results, and calculating the total thrust based upon the core mass flow rate and exit pressure. The predicted thrust-vector angle matched the angles measured from the schlieren photographs to within measurement uncertainty across the range of injection mass flow rates tested