Phosphor thermometry for in-cylinder surface temperature measurements in diesel engines

This is the authors' abstract. We don't add key points for this paper.

Phosphor thermometry is a temperature measurement technique that has previously been employed in technically relevant applications to obtain surface temperature. The technique is based on temperature-dependent changes in a phosphor's luminescence. To improve the accuracy and precision of temperature measurements with this technique, the present study considers, by way of example, the impact of conditions inside the cylinder of a diesel engine on decay time based single-shot phosphor thermometry measurements. After an initial, general assessment of the effect of prevailing measurement conditions, this research investigates errors caused by soot luminosity, extinction, signal trapping and changes of phosphors' luminescence properties due to exposure to the harsh environment. Furthermore, preferable properties of phosphors which are suitable for in-cylinder temperature measurements are discussed. 16 phosphors are evaluated, including LaAlGe2O7:Tm, YVO4:(Dy,Ce), ZnS:(Tm,Ag), and ZnS:(Tm,Li) which – to the authors' knowledge – have previously not been used in thermometry. Results indicate that errors due to photocathode bleaching, extinction, signal trapping and changes of luminescence properties may cause an erroneous temperature evaluation with temperature errors in the order of several tens of Kelvin.