Development and Application of Laser Diagnostics for Studies of Phenomena Related to IC Engine Combustion

Abstract: Various laser diagnostic techniques have been developed and demonstrated for engine, or engine-related measurements. The experimental work is presented in Chapter 3 and in Papers I-VII. In Chapter 3, imaging of soot in a running compression-ignition (CI) is described. Four different approaches were applied with the aim of investigating the applicability of these approaches in a running engine. In Paper I, Planar Laser-Induced Fluorescence (PLIF) was applied in a running spark ignition (SI) engine for measurements of the fuel concentration and homogeneity in the vicinity of the spark gap prior to ignition. The aim was to find out how the fuel distribution influences the cycle-to-cycle variations of the engine. In Paper II, PLIF of water was applied in a running engine to investigate the influence of residual gases in the vicinity of the spark gap prior to ignition. In Paper III is reported a basic investigation of the potential of PLIF for the study of water as a marker for residual gas in engines. Special care was taken in studying the effects of a focused laser beam in combination with a two-photon transition which arises in the excitation of water at 248 nm. In Paper IV is described how a combination of PLIF and spontaneous Raman scattering can be used for simultaneous imaging of vapour and liquid phase water. In Paper V, the application of PLIF to investigate the emissions of hydrocarbons in the exhaust of small two-stroke engines is described. Cycle-resolved, 2D measurements were conducted in order to find out when, during the stroke, the hydrocarbons are emitted. Cycle-resolved spectral measurements gave information on the species emitted at different crank angle positions. In Paper VI is demonstrated how phosphor thermometry can be applied to measure the temperature of a falling water droplet. Finally, in Paper VII, phosphor thermometry was applied to perform two-dimensional surface temperature measurements in a running optically accessible engine.