A Thermocouple System for Measuring Turbine-Inlet Temperatures

A fast-response, unique thermoelement combination of platinum-15 per cent iridium and palladium, whose emf output is about three fourths that of Chromel/Alumel at 2000 F (1093 C), has been found reliable from 1800 to 2300 F (982 to 1260 C) for more than 400 hours in a combustion atmosphere. A new, stable nickel-4.3 per cent silicon matching-lead-wire alloy was prepared for use up to an ambient temperature of 1400 F (760 C). Additional tests provided the best choice of insulation, thermocouple dimensions, sheath material, connectors, and harness design for aircraft jet engines. While it has heretofore been impractical or very difficult to determine turbine-inlet temperatures above 1600 F (871 C), this system is capable of measuring directly the most critical of all operational variables and accordingly allows safe potential increases in engine performance.