Flame-Millimeter-Wave-Interactions: A Radar-based Sensor Concept

This paper investigates the effects of an ethanol flame on an electromagnetic wave in the frequency range of 68-92 GHz. For a better understanding of the interaction between fire and radar signals, a dielectric model of the flame must be considered. Three main mechanisms were identified: The absorption of the ionized gas, the relative permittivity of the reaction products and the influence of incomplete combustion. Subsequently, measurements were made with two FMCW radar sensors to analyse the different zones of the fire. The measurements show that the influences of the fire are very small, but detectable and must be considered for larger fire dimensions. Due to the highly precise phase evaluation of the measurement signal, a flame supervision via FMCW radar can be considered.