Preheating and premixing effects on NO_x emissions in a high-pressure axially staged combustor

Journal Article · 30 August 2021 · Combustion and Flame

DOI: https://doi.org/10.1016/j.combustflame.2021.111710 · OSTI ID:1844552

Genova, Tommy ^[1]; Otero, Michelle ^[2]; Morales, Anthony ^[2]; Stiehl, Bernhard ^[2]; Martin, Scott ^[3]; Ahmed, Kareem ^[2]

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1. Univ. of Central Florida, Orlando, FL (United States); Embry-Riddle Aeronautical University
2. Univ. of Central Florida, Orlando, FL (United States)
3. Embry-Riddle Aeronautical University, Cincinnati, OH (United States)

NO_x emissions remain a primary concern for modern and future gas turbines, particularly as we progress towards a net-zero carbon future. It is critical to identify novel strategies to mitigate environmental pollutants for both modern turbines operated on natural gas and future turbines projected to use carbon-free fuels (such as hydrogen). In the current study, NO_x emissions of a reacting methane-air jet in a vitiated crossflow are experimentally investigated in a model axially staged combustor at 5 atm. The combustion products from the main stage combustor flow into the axial stage at temperatures ranging from 1580 to 1650 °C. The axial stage contains a reacting jet in crossflow, which provides an overall temperature rise ranging from 50 to 220 °C to generate exit temperatures similar to gas turbine engines. The focus of this paper is to explore the effects of flame liftoff and ignition timescales on the NO_x contribution of this secondary jet. This is done by varying the premixed level and preheat temperature of the axial jet. The effects are explored at different momentum flux ratios (J), jet equivalence ratios (φ_jet), exit temperatures (T_exit), and main stage (headend) temperatures (T_HE). High-speed CH* chemiluminescence imaging is employed for each test case to determine the flame stabilization point. For a given temperature rise and combustor exit temperature, an increase in ignition delay was observed with a decrease in jet temperature. This provided a NO_x benefit, particularly for jets that are injected at or close to an ignitable mixture fraction. Similarly, the coaxial injector caused a significant ignition delay compared to the fully premixed injector; this also led to a NO_x benefit. Overall, the results show that a thermally driven delay in the axial stage provides a greater NO_x reduction than a mixing delay.

• Research Organization: Embry-Riddle Aeronautical University, Cincinnati, OH (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC)
• Grant/Contract Number: FE0031227
• OSTI ID: 1844552
• Journal Information: Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: January 2022 Vol. 235; ISSN 0010-2180
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English