Experimental Study of Fuel-Air Mixing and Dilution Jets on Outlet Temperature Distribution in a Small Gas Turbine Combustor

Experimental analysis was conducted to study the impact of fuel-air mixing and dilution jet on the temperature distribution in a small gas turbine combustor using various optical diagnostic techniques. The strength and velocity of the swirler at the venturi exit were adjusted to modify the fuel-air mixture, which is presumed to dominate the heat release of the main combustion zone. Additionally, the dilution hole configuration, including the number and size of the holes, was varied to investigate the dilution effect on outlet temperature distribution. Various optical diagnostic techniques, such as particle image velocimetry, planar Mie scattering, and OH* chemiluminescence, were used to measure the flow field, fuel spray distribution, and flame structure, respectively. A reduction in swirling strength led to a decrease in the average flow rate in the throat, which improved the structure and symmetry of the axial vortex system in the sleeve, enhanced the mixing of fuel and gas in the dome swirling air, and ultimately, improved the temperature uniformity of the heat release zone. Compared to larger and sparse dilution jets, smaller and dense dilution jets tended to generate hot spots shifted towards the radial middle area.