Influence of Fluidic Control in a Staged Lean Jet Engine Burner on Combustor Performance

Seiji Yoshida,Johannes Heinze,Michael Schroll,Takeshi Yamamoto,Christoph Hassa

doi:10.3390/fluids4040188

Seiji Yoshida, Johannes Heinze + Show 3 more

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https://doi.org/10.3390/fluids4040188

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Abstract

To improve the turn-down ratio of a lean combustor, which has the greatest potential for reducing NOx emissions from jet engines, fuel staging is commonly employed. To further extend the stable operation range, air staging with a fluidic element is also considered. The influence of fluidic control on combustion was analyzed to better understand fluidic element-burner interactions. The pressure loss of each fluidic element was determined by measuring the pressure at the element exits. The effect of fluidic control on the atomization, fuel distribution, and flow field was investigated using optical, noninvasive techniques. The combustion performance of the burner with the fluidic element was evaluated using exhaust gas analyses. The pressure losses of the swirlers and fuel mixers were varied depending on the bleed air from the fluidic element. Under the idle condition, the reduction of pressure loss in the pilot fuel mixer resulted in inferior atomization due to the reduced gas velocity around the fuel film, which had a positive effect on lean blowout. Under the cruise condition and the staged mode, the reduction of the pilot air flow increased the equivalence ratio of the lean pilot stage and resulted in higher combustion efficiency.

Highlights

Lean premixed combustion is currently the best technique for reducing NOx emissions from jet engines
When burner air flow is in the neutral position, the ratio of the pilot air-flow rate is 13.9%, from Table 3; the burner air–fuel ratio (AFR) of 107 (= 14.9/13.9%) corresponds to the stoichiometry of the pilot stage
As the reduction of mass flow is linked to a reduction of pressure loss (Figure 6), lean blowout (LBO) is improved in accordance with commonly used LBO

Summary

Introduction

Lean premixed combustion is currently the best technique for reducing NOx emissions from jet engines. For small engines of regional aircraft, lower combustor temperatures during cruise conditions exacerbate this problem [2]. To obtain a lean combustor with the necessary turn-down ratio for gas turbine operation, fuel staging is used as a standard solution. Only a pilot stage operates with a diffusion flame for stable combustion. A main stage operating in premixed mode yields low-NOx combustion, while the pilot stage remains in operation to guarantee stable flame holding of the main stage. As the size of the pilot burner must be limited to prevent excessive NOx formation, a single staging point might not be sufficient; instead, circumferential staging of burner groups in the annular combustor or additional fueling devices may be required [3]

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