Development of a fiber-optic sensor for the measurement of dynamic cylinder pressure in spark ignition engine

This paper describes a new design of in-cylinder pressure sensor for automotive applications using optical technology. The technology has been applied to a spark ignition engine and compared against piezoelectric sensor. The paper presents a fiber-optic interferometric sensor based on highly birefringent side-hole fibers. The sensing part is composed of a side-hole fiber characterized by a very high pressure-to-temperature sensitivity ratio equal to 25 degrees C/bar, which is about two orders of magnitude higher than in the case of other highly birefringent fibers. The research with positive laboratory verification has proven the usefulness of fiber optic sensor for diagnostics of combustion engine work cycle. Assumptions that the use of interferential fiber optic sensor shall enable pressure measurements and calculation of indices resulting from these measurements that is based on an obtained data as well as controling the engine the way have turned out to be true. The research revealed the relation between the track of interferential fiber optic sensor signal and work cycle parameters of SI engine. Also the thesis that the measurement signal of interferential fiber optic sensor can be the carrier of data about certain SI engine workcycle parameters had been proven. The initial results from the sensors show good performance against reference sensor. We compared the dynamic characteristics of the fiber-optic sensor to the responses of a calibrated and temperature-compensated piezoelectric sensor. The dynamic characteristics of the fiberoptic sensor are in good agreement with the reference piezoelectric sensor, which shows the great utility of the side-hole fibers in accurate measurements of high dynamic pressures.