| dc.description.abstract | Most practical propulsion and power generation systems based on gas turbine engines operate at elevated combustor pressures. For example, the turbine inlet pressures of modern gas turbine engines used in airplanes typically vary between 30–50 bar. Therefore, innovative diagnostics
methods are needed to understand the temporally and spatially resolved flame dynamics inside combustors at high pressures in order to increase the combustion efficiency and flame stability, and also reduce pollutant formations. Hence, the objective of this thesis research is to establish a
laboratory-scale high-pressure burner facility suitable for incorporating non-intrusive, spatially,and temporally resolved optical diagnostics up to pressures of 50 bar. The high-pressure facility and the development of the supporting engineering systems are discussed in detail. High-speed
chemiluminescence imaging of OH* and CH* is used to characterize and reduced flame instabilities. Following these studies, a stainless-steel disk was mounted above the burner surface
to stabilize the flames. Subsequently, the laser diagnostics method, hydroxyl radical planar laser-induced fluorescence (OH-PLIF) imaging, is used to study the spatially resolved flame structure, combustion zones, and temperature distribution in the high-pressure flames. The flames studies
are premixed CH4/air mixtures with equivalence ratios ranging from 0.7–1.3. Initial experiments were conducted up to pressures of 10 bar. Laser pulses of approximately 10-ns duration at the wavelength of 283.305 nm were used to excite the Q1(7) rotational line of the A2Ʃ<-X2∏ (1, 0)
band of the OH radical, followed by fluorescence detection from the A<-X (1, 1) and (0,0) bands. Also, the Q1(5) and Q1(14) rotational lines of the OH radical were used for two-color OH-PLIF thermometry measurements. The laser energy dependence and the effects of collisional quenching
on the measured fluorescence signal interpretation at elevated pressures are discussed. The OH radical number density distributions are compared with equilibrium flame calculations in the range of flame equivalence ratios from 0.8–1.2. The present study establishes a robust burner configuration for high-pressure combustion studies such as soot and NOx formation, as well as a
testbed for advanced optical diagnostic development using nonlinear spectroscopic techniques. | en |
