Radial Swirler Designs for Ultra-Low NOx Gas Turbine Combustion

Abstract

Four radial swirler vane passage designs were investigated for low NOx lean well mixed combustion of natural gas at simulated gas turbine primary zone conditions in terms of reference velocities and 600–740K air inlet temperatures at atmospheric pressure. Each radial swirler had eight vane passages and the four passage designs were curved, aerodynamic tapered flat bladed, rectangular and circular passage cross sections. The first two designs had an area that decreased towards the passage outlet and the last two designs were constant area vane passages. The swirler exit diameter d (76mm) to the combustor diameter D (140mm) expansion ratio, D/d, was 1.84. Three methods of fuel injection were investigated: eight single fuel holes per radial vane passage injection, swirler outlet throat 8 hole wall injection and 8 hole radially outward central injection. The results showed that the different radial swirler designs did not have a strong influence on the NOx emissions, compared with the stronger influence of the fuel injection location. All radial vane swirler passage designs gave minimum NOx emissions in the 1–2 ppm range. The radial swirler design influenced which fuel injection location, passage or exit throat wall, gave the lowest NOx emissions. The results were compared with the CPMCP ultra-low NOx emissions concept to show that the present rapid fuel and air mixing radial swirler results are equal to the best premixed low NOx designs.