Analysis of length effect on thermodynamic characteristics in a Z-shaped evaporating flameholder. (January 2020)

• Record Type: Journal Article
• Authors: Miao, Junjie; Fan, Yuxin; Liu, Tianchi; Wu, Weiqiu
• Is Part Of: Acta astronautica. Volume 166(2020)
• Page Start: 369
• Page End: 376
• Publication Date: 2020-01
• Subjects: Z-shaped evaporating flameholder -- Length effect -- Ignition -- Flame-holding -- Turbine-based combined cycle; Astronautics -- Periodicals; Outer space -- Exploration -- Periodicals; Astronautics; Periodicals; 629.405
• DOI: 10.1016/j.actaastro.2019.10.033
• Languages: English
• ISSNs: 0094-5765

Abstract

Abstract: In this paper, the length effects on thermodynamic characteristics of a Z-shaped evaporating flameholder are studied to optimize the ignition and flame-holding performance. The characteristics of ignition kernel, flamelet propagation, and flame stability under the operating conditions of turbine-based combined cycle combustors are experimentally investigated. The numerical flow fields are performed to explain the experimental results. Furthermore, the droplet distribution and flame equivalence ratio are acquired using image-processing to interpret the length effects. The results indicate that optimizing the structure can achieve a better matching of flow pattern and fuel mist, and a more uniform spatial distribution of flame equivalence ratio, attributed to the improved fuel-air mixing. The optimization of the L/H ratio can reduce the ignition delay time and increase the premixed degree during the ignition process, thereby owning the superior ignition and blowout performance within the wide-range operation. Changing the L/H ratio alters the double-reaction-zone morphology, and the contribution of the second reaction zone to sustain flame rises with the reduced L/H ratio. The optimal structure can consequently decrease the lean ignition and blowout equivalence ratio by 29.3% and 39.0%, respectively. The results provide a theoretical basis for the optimization of pilot-ignition structure employed in afterburner/ramjet combustors. Highlights: The length effect on thermodynamic characteristics is investigated. The droplet distribution and equivalence ratio are studied by image-processing. The ignition kernel, flamelet propagation, and flame stability are analyzed. The performance of Z-shaped evaporating pilot-flameholder is optimized.