Combustion Imaging in Engines Using Electrical Impedance Measurements

This paper describes how the image of a flame within an enclosure can be reconstructed from multiple measurements of capacitive impedance, between non-intrusive sensing electrodes distributed around the combustion zone. Measurements across the combustion zone respond to the ionisation inherent in the combustion process, which changes the permittivity and hence the capacitance measured between electrodes. For this feasibility study, experimental data is presented from a laboratory analogue of an engine combustion chamber, demonstrating flames being imaged in real time. The sensing system is modelled using 3-D finite element methods, enabling analysis of practical electrode geometries for engine combustion chambers.