Effects of fluidic control of air-flow distribution on staged lean engine burner

Abstract

In this study, the effects of air-flow shifting between the pilot and main stages of a staged lean jet engine burner were investigated. A fluidic element attached in front of the swirlers was used to alter the air-flow split ratio between them, and the swirler and nozzle exit-section pressure loss behind the fluidic element was measured using an atmospheric isothermal test. The fluidic element did not fully recover the pressure loss in the burner inlet. However, it can also affect the losses, and cause an air shift between the pilot and main stage. Therefore, further combustion tests were conducted under two operating conditions: ground idle at 7% maximum take-off thrust and scaled cruise condition. Under ground idle conditions, increased pilot air flow improved the combustion efficiency for high fuel flow, and reduced pilot air flow improved it for low fuel flow. Staged and unstaged operations were also investigated under cruise conditions. In the staged operation, reduced pilot air flow increased the combustion efficiency, whereas in the unstaged operation, greater pilot air flow increased the combustion efficiency near the fueling mode switch-over point.