Digital Breakthrough Detection using laser-Induced, Thermal Diffusion Shock Waves

The efficiency of a jet engine is improved by increasing the temperature in the engine combustion components. Combustion chamber temperatures have increased up to 1600° C over the past decade. Therefore, jet engine combustion components must deal with high temperatures. Free-air-flow cooling holes are critical for cooling the components. But the process of drilling cooling holes has numerous problems, and back wall strike is the major problem that must be solved. This thesis presents innovative approaches to designing controllers to process the output of the sensor that receives laser-induced, thermal diffusion shock waves during the laser percussion drilling process. The controllers process the sensor output digitally to determine the exact moment of breakthrough to eliminate back wall strike, which damages the adjacent surface of jet-engine turbine components. There were two methods to process the sensor output digitally; the software method and the hardware method. In the software method, LabVIEW was used to extract pulse signal components from the sensor output and the laser power output. In the hardware method, operational amplifiers were used to extract pulse signal components from the sensor output and the laser power output. The test results proved that both approaches were promising and had unique advantages and disadvantages.