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UBC Theses and Dissertations

A new framework for analysis of fully-premixed and stratified turbulent flames generated by an industrial injector Saca, Leslie


This thesis is concerned with the characterization of an industrial injector, whose modus operandi is turbulent stratified premixed combustion. For this mode of operation, the fuel and air are premixed at molecular level; however, the fuel-air equivalence ratio varies locally at larger scales. A burner was designed and manufactured to house a gaseous fuel/air injector, which was provided by the industrial partner. Both fully and stratified premixed flames of methane and air were tested for a range of mean bulk flow velocities varying between 5 and 50 m/s. The (global) fuel-air equivalence ratio of the (stratified) premixed flames was set to unity. The cross-wire anemometry technique was used to characterize the background turbulent flow; and, the laser Rayleigh scattering technique was employed to investigate both the fuel and air mixedness fields as well as the turbulent flames characteristics. Near the center of the injector lobes, a hydrodynamic instability exists and is accentuated as the mean bulk flow velocity is increased. Analysis of mixedness fields suggests that the amount of the injected fuel is similar for both lobes up to 25 m/s; however, the lobe on the left-hand-side injects more fuel compared to that on the right-hand-side for mean bulk flow velocities larger than or equal to 25 m/s. Traditionally, studying the flame structure for fully and stratified premixed flames requires information regarding the mixture composition across the flame, whose acquisition is challenging. To overcome this challenge, a new parameter, referred to as the reduced temperature was introduced and quantified. It was shown that the probability density function of this parameter is similar for all tested conditions, and was used to develop a method for quantifying the burning area of the tested flames. Assuming that the flame stretch is not significant, it is obtained that stratification can slightly increase the normalized flame burning area. This is in agreement with the results presented in [1]; however, those presented here extends the findings of [1] to conditions that are more industrially relevant.

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