Phosphor Thermometry: Advances in Technique Development and Applications

Sammanfattning: Understanding the mechanisms that govern the combustion processes is important for being able to further increase the efficiency ofcombustion devices. Temperature is considered to be one of the most important parameters controlling the progression and finalproducts of combustion. Regulating the temperature in combustion devices enables higher degrees of efficiency to be achieved. Theengine components in combustion devices are subjected to high levels of thermal load. These can strain many of the engine componentsand if it is unattended to can lead to catastrophic engine failure. Temperature information can help to assess the thermal load the engineis experiencing and as a result can increase the longevity of the engine while at the same time enabling higher levels of efficiency to beattained. In addition, the production of emission gases is closely correlated to the temperature present during the combustion of fuel.Comprehending the spatial and temporal distribution of temperature can aid in finding measures to reduce the levels of emissiongenerated by a combustion engine.Although several different temperature-probing techniques that can provide temperature information are available, the harsh andreactive nature of the experimental conditions present within combustion engines can severely limit the applicability of such techniques.Phosphor thermometry excels in delivering precise and accurate temperature information concerning harsh environments such as thosepresent in combustion engines. It is a remote technique that is minimally intrusive and is highly robust. Phosphor thermometry utilizesthe temperature-dependent characteristic emission of thermographic phosphors to retrieve temperature information concerning asurface or a fluid. The temperatures can be determined either on the basis of the temperature dependence of the decay time of thephosphorescence or on the basis of temperature-dependent changes in the spectral distribution of the phosphorescence.The thesis presents the efforts that were made to develop the phosphor thermometry technique further. It involves demonstrations ofuse of this technique in combustion engines of different types. The results of the thesis work are reported in two major parts. In thefirst part, developments that were made in regard to certain fundamentals of the technique so as to improve its accuracy and precisionare documented. This includes the development of an automatic calibration routine, a more precise characterization of the detectorresponse, and investigation of the effects of engine lubricant oil on the performance of several different thermographic phosphors. Thesecond part of the thesis reports on several applications of phosphor thermometry technique to remote probing of the temperature ofdifferent motor components, such as the piston, the cylinder wall, and the burner tip of the combustor. The overall aim of the workconducted was to improve the precision and the accuracy of decay time-based phosphor thermometry as well as to enhance itsapplicability under a wider range of experimental conditions than studied previously.