Experimental and numerical study of MILD combustion for gas turbine applications. (15th June 2015)

• Record Type: Journal Article
• Authors: Kruse, Stephan; Kerschgens, Bruno; Berger, Lukas; Varea, Emilien; Pitsch, Heinz
• Is Part Of: Applied energy. Volume 148(2015:Jun. 15)
• Page Start: 456
• Page End: 465
• Publication Date: 2015-06-15
• Subjects: MILD combustion -- Flameless combustion -- Ultra low NOx and CO emission -- Gas turbines; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2015.03.054
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Effect of pressure, mixing on stability of MILD combustion studied for gas turbines. High pressure increases NO x emissions and destabilizes MILD combustion mode. Enhanced mixing stabilizes MILD combustion and lowers NO x emission. Mixing is key parameter to control and stabilize MILD combustion. Abstract: In this paper, the pressure influence on the MILD combustion process and on emissions is examined. Experiments were performed in a combustion chamber based on the reverse flow configuration to enhance mixing of fresh and burnt gases. First, investigations under atmospheric pressure were performed to determine the regime of jointly low NO x and CO emissions. Afterwards, the effects of burnt gas recirculation and mixing under ambient pressure were evaluated by decreasing the inlet nozzle diameter without changing the residence time. In the second step, measurements were conducted under higher pressure while keeping the mass flow rates constant. Thereby, the residence time is extended, the NO x formation chemistry is changed. These effects result in a strong rise in NO x emissions and simulations indicate that at higher pressure a flame is established at the nozzle exit for higher equivalence ratios. In order to decrease the Damköhler number and shift the combustion process to the well-stirred reactor regime, the inlet nozzle diameter was decreased without changing the residence time. Thereby, burnt gas recirculation and gas mixing is enhanced, while simultaneously extending the chemical time scales. A significant decrease in NO x emissions was detected.