Title: Direct numerical simulation of flame stabilization assisted by autoignition in a reheat gas turbine combustor

Abstract

A three-dimensional direct numerical simulation (DNS) is performed for a turbulent hydrogen-air flame, represented with detailed chemistry, stabilized in a model gas-turbine combustor. The combustor geometry consists of a mixing duct followed by a sudden expansion and a combustion chamber, which represents a geometrically simplified version of Ansaldo Energia’s GT26/GT36 sequential combustor design. In this configuration, a very lean blend of hydrogen and vitiated air is prepared in the mixing duct and convected into the combustion chamber, where the residence time from the inlet of the mixing duct to the combustion chamber is designed to coincide with the ignition delay time of the mixture. The results show that when the flame is stabilized at its design position, combustion occurs due to both autoignition and flame propagation (deflagration) modes at different locations within the combustion chamber. A chemical explosive mode analysis (CEMA) reveals that most of the fuel is consumed due to autoignition in the bulk-flow along the centerline of the combustor, and lower amounts of fuel are consumed by flame propagation near the corners of the sudden expansion, where the unburnt temperature is reduced by the thermal wall boundary layers. An unstable operating condition is also identified, wherein periodic auto-ignitionmore » events occur within the mixing duct. These events appear upstream of the intended stabilization position, due to positive temperature fluctuations induced by pressure waves originating from within the combustion chamber. This DNS investigation represents the initial step of a comprehensive research effort aimed at gaining detailed physical insight into the rate-limiting processes that govern the sequential combustor behavior and avoid the insurgence of the off-design auto-ignition events.« less

Authors:

Aditya, Konduri  ^[1];

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Gruber, Andrea ^[2]; Xu, Chao ^[3]; Lu, Tianfeng ^[3]; Krisman, Alex ^[1]; Bothien, Mirko R. ^[4]; Chen, Jacqueline H. ^[1]

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+ Show Author Affiliations

1. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Combustion Research Facility
2. SINTEF Energy Research, Trondheim (Norway)
3. Univ. of Connecticut, Storrs, CT (United States). Dept. of Mechanical Engineering
4. Ansaldo Energia Switzerland AG, Baden (Switzerland)

Publication Date:

Sun Jul 29 00:00:00 EDT 2018

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1466998

Alternate Identifier(s):

OSTI ID: 1694199

Report Number(s):

SAND-2017-13327J
Journal ID: ISSN 1540-7489; 659379

Grant/Contract Number:  

AC04-94AL85000; 257579/E20; NA-0003525; AC02- 05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Proceedings of the Combustion Institute

Additional Journal Information:

Journal Volume: 37; Journal Issue: 2; Journal ID: ISSN 1540-7489

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; 20 FOSSIL-FUELED POWER PLANTS; Sequential combustor; Flame stabilization; Autoignition; Hydrogen; Direct numerical simulation