Image Processing for Measurement Analysis of the AV-8B F-402 Hot Nozzle

The Rotating Hot Exhaust Nozzles of the F402 Turbofan engine are two of four Exhaust Nozzles that produce thrust, allowing the AV-8B Harrier Jet to perform vertical and short take-off and landing. Handling damage and weld repairs during maintenance and transport have affected the Nozzle’s throat area. A deformed throat area has caused a production of thrust outside of tolerances required for normal engine performance. A metal trimmer or compensator may be fitted to an oversized nozzle to control thrust by reducing the throat area. The trimmer’s size may be changed or removed in the case of an undersized nozzle. Precise measurement of the Nozzle’s throat area is critical to adjusting with trimmers as necessary. One of Sweet Briar College’s Senior Capstone teams has been tasked with addressing a technical need of the U.S. Navy. The goal is to design a Throat Area Measurement System for the F402 Rotating Hot Exhaust Nozzle. Requirements defined by the client and the Sweet Briar College team led to the evaluation of concepts and selection of an image processing method to obtain the throat area value. This technique involves capturing an image of the Nozzle at a calibrated camera position, then uploading it to a MATLAB program written by the team. The program runs necessary functions to binarize the image, then calculate a throat area value in square inches. Image processing requires high contrast for accuracy; therefore, a background has been designed to accommodate this specification. The team has included code to mitigate unwanted image noise and output a value. Construction of a physical prototype has allowed for an analysis of the design process and an understanding of where alterations must be made. With this code and prototype, the team has taken the first steps to automating and improving the process to obtain area values for the Hot Exhaust Nozzle.