CARS measurements of temperature and species concentrations in an IC engine

Abstract

Temperature measurements alone, and also simultaneous CO₂ concentration and temperature measurements, have been performed inside a fired IC engine. To tackle the two main problems encounted when making measurements in an engine (i.e., cycle-to-cycle variations and beam steering by density gradients), the shot-by-shot referencing technique and the in situ referencing technique using N₂ to determine [CO₂] were used. The temperature is deduced from the broadband N₂ CARS signal and narrow band detection is used for CO₂. A representative example of temperature measurements is given which shows a correlation between temperature and knocking intensity in the burnt gas of a knocking engine. The first simultaneous determinations of temperature and [CO₂] are also reported; so far these are reliable only during the compression stoke.