Simulation of the Self-Ignition of a Cold Premixed Ethylene-Air Jet in Hot Vitiated Crossflow
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Simulation of the Self‑Ignition of a Cold Premixed Ethylene‑Air Jet in Hot Vitiated Crossflow Roberto Solana‑Pérez1 · Oliver Schulz1 · Nicolas Noiray1 Received: 10 December 2019 / Accepted: 18 August 2020 © The Author(s) 2020
Abstract The aim of this paper is to analyze the self-ignition of a jet flame in hot vitiated cross flow using Large Eddy Simulation with analytically reduced chemistry. A rich premixed ethylene-air mixture ( 𝜙 = 1.2 ) at 300 K is injected into a hot vitiated crossflow at 1500 K. The simulated reacting flow steady-state was validated against experiments in previous publications and the focus of the present work is the transient self-ignition of the jet. It is shown that spontaneous ignition occurs at very lean mixture fractions in the form of reacting patches in the windward jet mixing layer. These patches grow, laterally wrap the jet and extend into the recirculation region. Chemical explosive mode analysis is performed to identify the chemically active regions that are precursors of the patches undergoing spontaneous ignition. It is shown that the self-ignition occurs at very lean fuel concentrations regions, which are leaner and hotter than the most reactive mixture fraction of the jet and crossflow. This is explained by the fact that the scalar dissipation is significantly lower in these very lean regions. Ultimately, the peak heat release moves toward the richer regions and an autoignition cascade governs the steady state flame anchoring. Keywords Reactive jet in crossflow · CEMA · Autoignition · Sequential combustion · LES
1 Introduction The jet in crossflow (JICF) configuration has been widely studied over the past 80 years, see Margason (1993), due to its significant technological interest. This configuration generates a complex flow field allowing for fast mixing rates of 2 streams. This is useful in lean combustion technology, for instance, where a compact mixing section upfront of the flame is highly desirable. The JICF configuration has been extensively used in aeronautic and power applications (Karim et al. 2017; Pennell et al. 2017), examples include fuel and dilution air injection at staged combustors and effusion holes for turbine blade cooling * Roberto Solana‑Pérez [email protected] * Nicolas Noiray [email protected] 1
CAPS Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
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Flow, Turbulence and Combustion
(Marr et al. 2012; Roa et al. 2012). Most of the research in the literature focuses on nonreacting JICF, see the reviews from Karagozian (2010), and Mahesh (2013). Less is known about reactive JICF (RJICF), where experimental studies have been mainly conducted for non-premixed configurations with jets being composed of pure fuel or N 2-diluted fuel, e.g. Sidey and Mastorakos (2015), and Steinberg et al. (2013). Fleck et al. (2013) showed ignition kernels that do not always anchor the flame. Sullivan et al. (2014) proposed autoignition as flame stabilization mechanism after measuring ignition lo
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