Dynamic Effects of Temperature on FBG Pressure Sensors Used in Combustion Engines

In this work, we described a study of the influence of dynamical temperatures on pressure measurements in two different packaging types used in FBG pressure sensors. We developed these sensors to measure internal combustion pressure in closed-loop control of thermoelectric engines. The packaging techniques development considered the available monitoring points in the thermoelectric engine and the harsh environment of the monitoring points. In a monitoring point, the temperature can exceed 300 °C and the pressure can reach 250 bar. We detailed the use of single-ended and double-ended FBG fixation methods as packaging techniques. The FBG pressure sensors using these techniques were tested in the laboratory and a thermoelectric engine. The results demonstrated that the dynamical behavior of the high-temperature gas originated from the combustion chamber affects the dynamical pressure measurements performed by the single-ended FBG pressure sensors when they were exposed to the hot gas. This effect can be suppressed by using a double-ended FBG pressure sensor mainly due to its packaging method. Its signal shape is comparable to a reference sensor used in the same condition became this FBG packaging solution the most suitable to use in the closed-loop control of thermoelectric engines.