Multicolor Techniques for Identification and Filtering of Burst Signals in Jet Engine Pyrometers

Abstract

A Defense Advanced Research Projects Agency (DARPA)funded multicolor pyrometry (MCP) experiment was carried out on a governmentprovided aircraft engine to study the nature of hot particulate bursts generated from the combustor at certain engine conditions. These bursts of hot particulates lead to intermittent highvoltage signal output from the lineofsight (LOS) pyrometer that is ultimately detected and used by the onboard digital engine controller (DEC). The investigation used a highspeed MCP system designed to detect bursts and identify their properties. Results of the radiant temperature, multicolor temperature, and apparent emissivity are presented. The results indicated that the apparent emissivity calculated during the signal burst was lower than that of the blade. The root cause for the signal burst was identified as soot particles generated as a byproduct of combustion under certain conditions. This conclusion was drawn based on both experimental and simulation results. Technical strategies to separate, reduce, or remove the burst signal are proposed.