Characterization of a two-dimensional temperature field within a rapid compression machine using a toluene planar laser-induced fluorescence imaging technique

Abstract

The homogeneous charge compression ignition (HCCI) combustion process is an advanced operating mode for automotive engines. The self-ignition mechanisms that occur within the combustion chamber exhibit extreme temperature dependence. Therefore, the thorough understanding of corresponding phenomena requires the use of diagnostic methods featuring a sufficient thermal sensitivity, applicable in severe conditions similar to those encountered within engines. In this respect, toluene planar laser-induced fluorescence (PLIF) is applied to the inert compression flow generated within an optical rapid compression machine (RCM). A relatively simple diagnostic system is retained: a single wavelength excitation device (266 nm) and a single (filtered) collection system. This diagnostic system is associated with an image processing strategy specifically adapted to RCM devices. Despite the severe conditions under consideration (40 bar, 700–950 K), the method allows us to obtain relatively large two-dimensional temperature fields that display a level of description seldom achieved in such devices. In particular the temperature gradients, which play a crucial role in HCCI combustion processes, can be estimated. The present experimental results confirm the good reliability and accuracy of the method. The information gathered with this toluene PLIF method puts in evidence its high potentialities for the study of aero-thermal-reactive processes as they take place in real engine conditions. The retained strategy also brings new possibilities of non-intrusive analysis for flows practically encountered within industrial devices.

Application of planar laser-induced fluorescence measurement techniques to study the heat transfer characteristics of parallel-plate heat exchangers in thermoacoustic devices

“…In standard applications such as internal combustion engines or jet flows, the temperature fields are investigated within relatively unobstructed imaging domains; and although the temperature distributions may have large temperature gradients (cf. reference [31]), the main focus is the nature of the temperature distribution, not an accurate estimation of the temperature gradient for heat transfer calculations. In the thermoacoustic systems, complex internal solid structures (stacks and heat exchangers) form a set of narrow channels, in which the temperature gradients in very thin thermal boundary layers have to be accurately estimated in order to obtain reliable values of the gas-solid heat transfer rates.…”

Temperature measurements in a rapid compression machine using anisole planar laser-induced fluorescence

“…Similar approaches have been described in the literature. Strozzi et al [10] used PLIF to characterize a two-dimensional temperature field in an RCM, with a single-excitation, two-colour detection technique, relying on the temperature dependence of toluene fluorescence established by Koban et al [11], at atmospheric pressure and for the temperature range 300-950 K. These authors obtained temperature fields that clearly revealed a distorted structure, in particular at the boundary between the hot and cold zones. In-cylinder temperature imaging using a shock tube or spray has also been applied to the study of IC engines.…”

Using rapid compression machines for chemical kinetics studies

“…As noted earlier, the temperature field recorded by Mittal and Sung [34] for compression with a creviced piston was much more uniform compared to its flat piston counterpart. In a recent study, Strozzi et al [82] used toluene PLIF to characterize an RCM temperature field for inert mixtures. However, in LIF studies, markers like toluene or acetone are not always present in combustible mixtures tested in RCMs; in addition, pyrolysis of these markers pose an additional complexity in the LIF measurements at higher temperatures.…”