Heat release rate of the swirl flames is an important parameter for the gas turbine state. It plays an essential role in the study of combustion characteristics, combustion efficiency and chamber protection. Several swirling CH4/air diffusion flames were investigated in a gas turbine model combustor via the spatial flame mode transition. In the combustion mode transition, we utilized three-dimensional computed tomography of chemiluminescence (3D-CTC) technique due to the complexity of swirling combustion flow field. The 3D emissions of CH* were measured and taken as qualitative indicators of the heat release rate under three Reynolds number conditions. This 3D measurement method utilizes 8 multi-directional CH* images as inputs combined with tomographic algorithms to compute the 3D distribution of CH* intensities. In this study, the transitions of heat release area with Reynolds number were analyzed, and the results show that the heat release rate changing more obviously along the nozzle radial direction than the axis direction, and the largest heat release area moves forward significantly.
Multi-species measurements of N2O, CO, NO within an ammonium dinitramide (ADN) based thruster are presented using quantum cascade lasers, while gas temperature are obtained using near-infrared H2O two-line thermometry. ADN monopropellant represents a new generation of green propellant for spacecraft propulsion. Measurements using the developed mid-infrared diagnostic system provide an access to characterize the combustion process inside the ADN based thruster, while theoretical study of ADN monopropellant combustion is still under study. Both steady-state firing and pulse-mode firing for ADN based thruster operation are measured in the present experiments. Results of multispecies concentration agree well with the mechanism of the combustion process and divide the whole process into decomposition stage and combustion stage. Reaction (R1, NH4N( NO2)2→ NH3+N2O+HNO3 ) is the primary reaction branch as N2O generation is much higher and faster than NO generation in decomposition stage at the measured position. To the author’s knowledge, this work represents the first multispecies simultaneous measurements in an actual ADN based thruster using mid-infrared laser absorption spectroscopy. The time-resolved multispecies results aid in an improved understanding of the ADN monopropellant combustion and demonstrate mid infrared diagnostic technique’s practicality for small-sized ADN based thruster.
Tunable Diode Laser Absorption Spectroscopy (TDLAS) has been one of the most powerful techniques for combustion diagnostics in different kinds of burners. Combined with Hyperspectroscopy Tomography (HT), TDLAS can improve its spatial solution. This study reports a TDLAS-tomography system and its application in a swirl burner. The diagnostics system composed of sixteen beams (13X13, 13 parallel beams and 13 vertical beams). Four water vapor absorption lines, 7185.6 cm-1, 7444.3 cm-1, 7466.3 cm-1, and 6807.8 cm-1, were utilized in each beam using time-division-multiplexed (TDM) method at total measuring frequency of 2.5 kHz. A reconstruction routine based on simulated-annealing algorithm was used to deduce distributions of temperature T and water partial pressure PX. Dynamic data was obtained during the ignition of hydrogen fuel at the exit of the scramjet combustor. T and PX distribution of cross section indicate the flame location and its intensity. Successful experiments show great performance of this diagnostic method.
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