Measurements of Gas Temperatures in Combustion Engines by Ultrasound

Abstract

The possibility of measuring gas temperatures in internal combustion engines during actual operation has been studied at the Sloan Laboratories for Automotive and Aircraft Engines under the supervision of Professor C. F. Taylor. Barium titanate transducers are used at 2 mcps to produce short ultrasonic pulses in the combustion chamber through metallic coupling rods. The transit time of the sound signal is measured electronically and related to the absolute temperature of the gas mixture. The accuracy of temperature measurement in the unburned charge at about 1500°F is about 20°F. No complete evaluation of the accuracy has yet been made inside of the flame region. Sonic temperature measurements are expected to be particularly useful in studies of the antiknock properties of fuel. Real-gas behavior and thermal relaxation are the limiting factors in other applications. [This work was initiated by the Coordinating Research Council, Inc. and has been carried out with the support of the U. S. Army Ordnance.]