Laser-Induced Phosphorescence and the Impact of Phosphor Coating Thickness on Crank-Angle Resolved Cylinder Wall Temperatures

Abstract

In order to further improve the energy conversion efficiency in reciprocating engines, detailed knowledge about the involved processes is required. One major loss source in internal combustion engines is heat loss through the cylinder walls. In order to increase the understanding of heat transfer processes and to validate and generate new heat transfer correlation models it is desirable, or even necessary, to have crank-angle resolved data on in-cylinder wall temperature.Laser-Induced Phosphorescence has proved to be a useful tool for surface thermometry also in such harsh environments as running engines. However, the ceramic structure of most phosphor coatings might introduce an error, due to its thermal insulation properties, when being exposed to rapidly changing temperatures. In this article the measurement technique is evaluated concerning the impact from the thickness of the phosphorescent layer on the measured temperature. Experiments with different layer thicknesses are performed both during motored and fired operation of a HCCI engine. The results reveal a need for caution when applying the technique for in-cylinder measurements.

Planar measurements of spray-induced wall cooling using phosphor thermometry

“…These materials possess the primary characteristic of temperature-sensitive luminescence emission following laser excitation. By coating the phosphor to the surface of interest, the coating temperature can be remotely probed, thereby allowing in-situ application in internal combustion engines (Aizawa and Kosaka 2008;Fuhrmann et al 2011Fuhrmann et al , 2013Husberg et al 2005;Kashdan and Bruneaux 2011;Knappe et al 2011). …”

Investigation and compensation of the nonlinear response in photomultiplier tubes for quantitative single-shot measurements

“…The experiment is set up in a way that an ideal time gated PMT, switched on only during the evaluated time window, should have no means to distinguish the two different phosphorescence emissions. However the PMT used here also recorded a peak voltage prior to the evaluation window, that was about 54 times higher for the La 2 O 2 S:Eu phosphor than for CdWO 4 . In Figure 9, the results for the two cases are displayed, showing a horizontal response distribution for CdWO 4 in contrast to the results obtained with La 2 O 2 S:Eu.…”

“…4,15,16 Both phosphors combined have a common range of decay times from 10 μs down to 100 ns. This broad overlap region is beneficial as it allows achieving similar decay times by keeping the two phosphors at different temperatures.…”

“…Low laser pulse energies between 70 and 140 μJ were used in order to avoid saturating the phosphor. The resulting phosphorescence was imaged onto a photomultiplier module (Hamamatsu H6780-04) after passing an interference filter, centered at 540 nm (FWHM = 10 nm) for the La 2 O 2 S:Eu phosphor and 450 nm for CdWO 4 (FWHM = 40 nm). The filters were placed in front of the detector to eliminate spurious laser radiation and to spectrally isolate the phosphorescence emission.…”

“…[2][3][4] The PMT provides opto-electrical conversion combined with internal electrical amplification, see Figure 1, making it suitable for low light level measurements. They are temporally resolved detectors; depending on circuitry they can resolve, in real time, the impingement of single photons on the detector, or measure continuous streams of photons.…”