Applications of Laser Based Measurements to Combustion Related Fluid Dynamics

Abstract: This thesis is concerned with laser based techniques for the measurement of fluid dynamical properties and their application to combusting flowfields or flowfields related to combustion. As an introduction, the theory of turbulent flows and combustion is shortly presented. An overview of laser based measuring techniques is given. Next, seven papers are included. The main topic of papers 1 and 2 is the measurements of swirling pipe flows with sudden axi-symmetric expansions. These flowfields are related to the flowfields of gas turbine combustors. Measurements and computations using commercial software are compared. Papers 3 and 7 deal with an laser Doppler anemometry based method for the measurement of the turbulent dissipation rate and its application to an axi-symmetric free jet, respectively. The measurements rely on two-point measurements with high spatial resolution. Also three-component one-point measurements are used to obtain the triple velocity correlations. Together these measurements are sufficient to present the energy balance, if pressure effects are neglected. Papers 4, 5 and 6 are concerned with the turbulent flame speed under premixed conditions. Papers 4 and 5 present flame speed measurements from a stationary burner using methane and Danish natural gas. Particle image velocimetry and one- and two-point Laser Doppler anemometry is used to measure flame speed and turbulent quantities, including integral length scales. Paper 7 presents measurements of flame speed and turbulence parameters in an spark ignition engine. Here heat release analyses from pressure measurements are combined with one- and two-point laser Doppler anemometry to analyze influence of turbulence on flame propagation.