Effect of fuel/air ratio on air blast simplex nozzle performance

Abstract

The Air-Blast Simplex (ABS) nozzle may have significant mechanical design advantages when compared to Pure Air-Blast (PAB) designs, and attractive cost benefits. The major barrier to implementing ABS nozzles is spray collapse at high ambient pressures. The present study addresses this issue, and presents the results in a manner that is useful to the gas turbine combustor designer. The results reveal that spray collapse is not significant as long as the fuel-to-air mass ratio is maintained below about 0.3. The results also reveal two distinct curves for air effective area that are attributed to the presence or lack of flow separation in the vane/shroud assembly. In the case of the separated flow, a larger rate of decrease in effective area with increasing fuel air mass or momentum ratio is observed. These results help address ABS spray angle collapse at high pressure, and identify strategies that may adequately mitigate, or even eliminate, spray collapse in a suitably designed combustor.