Session: 04-15: Combustor Flows

Paper Number: 81682

81682 - Study on the Non-Reacting Flowfield Characteristics of Lean Premixed Injector Modules With the Convergent Outlet 

Lean premixed combustion, which is still the mainstream way of reducing NOx emissions from land-based gas turbines, has reduced NOx emissions below 25ppm (@ 15% O₂). However, with increasingly stringent air quality rules, researchers continue to look for the new technology to meet lower NOx emissions target without exhaust gas aftertreatment system. Therefore, the paper proposes a new type of natural gas-fueled lean premixed injector module with a convergent outlet, which consists of swirler, fuel injection holes, premixing section and convergence outlet, and the fuel injection hole is located at swirler-vanes base.

In this paper, the effects of key structural parameters of injector modules (such as swirler-vanes angles, blade profiles and premixed section lengths) on non-reacting flowfield characteristics were studied by means of commercial numerical software and particle image velocimetry under atmospheric pressure condition. The numerical results were consistent with the experimental results: the stable central recirculation zones were formed downstream of any injector with different structural parameters, and they were separated from the injector outlet for a certain distance, which was conducive to the formation of detached flame and avoid the risk of auto-ignition and flashback. In addition, there were some differences in the non-reacting flowfield  characteristics under different structural parameters: For the injector modules with swirler-vanes angles of 30 °, 35 ° and 40 °, with the decrease of swirler-vanes angle, the swirl intensity at the injector outlet decreases greatly, and the peak value of axial velocity is closer to the central axis. Therefore, the smaller the swirler-vanes angle, the smaller the axial dimension, radial dimensions and axial velocity of the recirculation zone, and the stagnation point of the recirculation zone is farther away from the injector outlet. Compared with the flowfield of injector with straight swirler-vanes, the swirl number at the outlet of injector with curved swirler-vanes was slightly higher, so the size of the central recirculation zone and the distance from the injector outlet between them were almost the same. For the injector modules with premixed section length of 30mm, 45mm and 60mm, due to wall friction and turbulent dissipation, the swirl number at the outlet of injector module decreased gradually with the increase of premixed section length, so the longer the premixing length, the smaller the axial dimension and radial dimensions of the recirculation zone, and the stagnation point of the recirculation zone is farther away from the injector outlet.

The lean premixed injector module with the convergent outlet proposed in this paper can form the detached recirculation zone and avoid the risk of auto-ignition and flashback. In addition, the influence of the key structural parameters on non-reacting flowfield characteristics obtained in this paper can provide theoretical support for design and application of lean premixed injector modules

Presenting Author: Fujun Sun Northwestern Polytechnical University

Presenting Author Biography: My name is Fujun Sun. I am currently studying at Northwestern Polytechnical University. I am a Ph.D. student. The research direction is the flowfield and combustion performance of the land-based gas turbine combustion chamber. I am from a small rural village in Taikang County, Henan Province, China, 2009.9-2012.6 studied at the First High School of Taikang County, Henan Province. From September 2012 to June 2016, I studied at the School of Power and Energy, Northwestern Polytechnical University

Authors:

Fujun Sun Northwestern Polytechnical University
Jianqin Suo Northwestern Polytechnical University
Luhua Guo Northwestern Polytechnical University