Signal Reconstruction Applied to a Fast Response Flame Ionisation Detector

The Fast-response Flame Ionisation Detector is used to measure levels of un-burnt hydrocarbons in the cylinder and exhaust of engines. Its fast response allows uHC emission processes to be resolved within an engine cycle.

This paper describes a method for obtaining even greater detail by post-processing the output of the device using a Finite-Impulse Response (FIR) digital filter. The specification of the filter can be obtained by understanding the flow regimes within the sampling system. Examples from in-cylinder and exhaust sampling are presented with suggestions for implementation and further improvement.