Comparison of Flame Dynamics at Stable and Near-LBO Conditions for Swirl-Stabilized Kerosene Spray Combustion

Abstract

An experimental investigation was conducted to characterize the flame structures and dynamics at stable and near-lean blowout (LBO) conditions. The current experiments were carried out using a laboratory-scale aero-combustor with an internally-staged dome. The internally-staged injector consisted of pilot and main swirlers, and the pilot swirler was fueled with Chinese kerosene RP-3 while the main injector was chocked. The resulting spray flame was confined within a quartz tube under atmosphere pressure. In the present study, the influence of swirl intensity of the pilot swirler was also investiagted. The OH* chemiluminescence of the flame was recorded by a high-speed camera at a frequency of 2000 Hz. From the high-speed OH* images, the reaction zone was marked and the fluctuation of the reaction zone along axial direction was observed, showing that it became stronger at near-LBO condition than at stable condition. Proper Orthogonal Decomposition (POD) analysis was further used to provide insights into the characteristics of flame dynamics. Based on the POD results, the difference of the flame dynamics between the stable and near-LBO combustion was distinct. While the major Mode l of the flame under stable condition was rotation representing the rotation motion in the swirl flame, at near-LBO condition the flame dynamics included three modes — vibration, rotation, and flame shedding. In addition, for swirl-stabilized kerosene spray combustion investigated herein, the fluctuation of the reaction zone in axial direction became stronger with decreasing equivalence ratio when approaching LBO, and the POD analysis indicated that the Mode l of flame dynamics transitions from the rotation mode to the vibration mode. Although the change of pilot swirl number was found to have little influence on the Mode l of flame dynamics, it was noted to vary the fluctuation energy of the flame.

Investigation of differences in lean blowout of liquid single-component fuels in a gas turbine model combustor

“…In the past, various aspects of spray combustion were studied using laboratory scale model combustors with prefilming airblast atomisers, more or less similar to the one used in this study. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] The majority of the investigations used kerosene or a kerosene surrogate as a fuel. To the authors' knowledge, the influence of different single component hydrocarbon fuels on airblast atomised swirling spray flames, has not been investigated in detail.…”

“…Yang et al 44 found atomisation performance of their pilot spray to dominate the lean blowout process. Regarding flame dynamics, Zhang et al 18 indentified several fluctuation modes of the pilot flame of a staged injector at near lean blowout conditions with the axial oscillation being the most dominant mode. The specific influence of different liquid fuels on lean blowout of swirl-stabilised spray flames has been investigated by Burger et al 45,46 From their tests with a laboratory scale swirl-stabilised spray flame they concluded that lean blowout limits are potentially influenced by both physical and chemical fuel properties.…”

Experimental Investigation on Auto-Ignition Characteristics of Kerosene Spray Flames

“…However, only a few fundamental studies focused on the ignition and combustion performance of RP-3 spray. Zhang et al [23] investigated the ignition limit of RP-3 spray at both stable and near-lean blowout conditions. They found that the rotation mode in the swirl flame is primary under stable conditions, while three modes of the flame dynamics, including vibration, rotation, and flame shedding, can be found at near-lean blowout conditions.…”

Experimental and numerical study of the effect of main stage stratifier length on lean blow-out performance for a stratified partially premixed injector

“…Liu et al 14 experimentally investigated the ignition and LBO performance of a fuel-staged multi-injection combustor by comparing two different pilot atomizer designs, and the results showed that matching the pilot spray with swirling air streams was an effective method to improve stable combustion of the pilot stage. Zhang et al 15 analyzed the flame dynamics in a lean staged injector and concluded that the swirl-stabilized flame at near-LBO conditions consisted of three parts: axial oscillation mode, circumferential rotation mode, and flame shedding mode, and the axial oscillation mode took over the circumferential rotation mode when transitioning from stable to near-LBO flames.…”