scholarly journals Experimental investigation of the response of laminar premixed flames to equivalence ratio oscillations

2016 ◽  
Vol 167 ◽  
pp. 172-183 ◽  
Author(s):  
Holger Ax ◽  
Wolfgang Meier
Keyword(s):  
Experimental Investigation ◽  
Equivalence Ratio ◽  
Premixed Flames

Characteristics of Flame Bases for V-Gutters Stabilized Premixed Flames

2013 ◽  
Author(s):  
Fan Gong ◽  
Yong Huang
Keyword(s):  
Thermal Conductivity ◽  
Temperature Gradient ◽  
Equivalence Ratio ◽  
Premixed Flames ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Heat Conducting ◽  
Inlet Velocity ◽  
The Impact

The objective of this work is to investigate the flame stabilization mechanism and the impact of the operating conditions on the characteristics of the steady, lean premixed flames. It’s well known that the flame base is very important to the existence of a flame, such as the flame after a V-gutter, which is typically used in ramjet and turbojet or turbofan afterburners and laboratory experiments. We performed two-dimensional simulations of turbulent premixed flames anchored downstream of the heat-conducting V-gutters in a confined passage for kerosene-air combustion. The flame bases are symmetrically located in the shear layers of the recirculation zone immediately after the V-gutter’s trailing edge. The effects of equivalence ratio of inlet mixture, inlet temperature, V-gutter’s thermal conductivity and inlet velocity on the flame base movements are investigated. When the equivalence ratio is raised, the flame base moves upstream slightly and the temperature gradient dT/dx near the flame base increases, so the flame base is strengthened. When the inlet temperature is raised, the flame base moves upstream very slightly, and near the flame base dT/dx increases and dT/dy decreases, so the flame base is strengthened. As the V-gutter’s thermal conductivity increases, the flame base moves downstream, and the temperature gradient dT/dx near the flame base decreases, so the flame base is weakened. When the inlet velocity is raised, the flame base moves upstream, and the convection heat loss with inlet mixture increases, so the flame base is weakened.

An experimental investigation into the behavior of premixed flames of hydrogen/carbon monoxide/air mixtures in a half-open duct

Fuel ◽  
2019 ◽  
Vol 237 ◽  
pp. 619-629 ◽  
Author(s):  
Xufeng Yang ◽  
Minggao Yu ◽  
Kai Zheng ◽  
Shaojie Wan ◽  
Liang Wang
Keyword(s):  
Experimental Investigation ◽  
Carbon Monoxide ◽  
Premixed Flames

Numerical Analysis of Equivalence Ratio Fluctuations in a Partially Premixed Gas Turbine Combustor Using Large Eddy Simulations

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Ping Wang ◽  
Qian Yu ◽  
Prashant Shrotriya ◽  
Mingmin Chen
Keyword(s):  
Reaction Mechanism ◽  
Equivalence Ratio ◽  
Flame Temperature ◽  
Premixed Flames ◽  
Large Eddy Simulations ◽  
Combustion Model ◽  
Inlet Channel ◽  
Large Eddy ◽  
Partially Premixed Flames ◽  
Partially Premixed

In the present work, the fluctuations of equivalence ratio in the PRECCINSTA combustor are investigated via large eddy simulations (LES). Four isothermal flow cases with different combinations of global equivalence ratios (0.7 or 0.83) and grids (1.2 or 1.8 million cells) are simulated to study the mixing process of air with methane, which is injected into the inlet channel through small holes. It is shown that the fluctuations of equivalence ratio are very large, and their ranges are [0.4, 1.3] and [0.3, 1.2] for cases 0.83 and 0.7, respectively. For simulating turbulent partially premixed flames in this burner with the well-known dynamically thickened flame (DTF) combustion model, a suitable multistep reaction mechanism should be chosen aforehand. To do that, laminar premixed flames of 15 different equivalence ratios are calculated using three different methane/air reaction mechanisms: 2S_CH4_BFER, 2sCM2 reduced mechanisms and GRI-Mech 3.0 detailed reaction mechanism. The variations of flame temperature, flame speed and thickness of the laminar flames with the equivalence ratios are compared in detail. It is demonstrated that the applicative equivalence ratio range for the 2S_CH4_BFER mechanism is [0.5, 1.3], which is larger than that of the 2sCM2 mechanism [0.5, 1.2]. Therefore, it is recommended to use the 2S_CH4_BFER scheme to simulate the partially premixed flames in the PRECCINSTA combustion chamber.

scholarly journals An analytical model based on the G-equation for the response of technically premixed flames to perturbations of equivalence ratio

2017 ◽  
Vol 10 (2) ◽  
pp. 103-110 ◽  
Author(s):  
Alp Albayrak ◽  
Wolfgang Polifke
Keyword(s):  
Impulse Response ◽  
Time Scale ◽  
Equivalence Ratio ◽  
Premixed Flames ◽  
Flame Speed ◽  
Flame Surface ◽  
Heat Of Reaction ◽  
Local Behavior ◽  
Model Based ◽  
Flame Shape

A model for the response of technically premixed flames to equivalence ratio perturbations is proposed. The formulation, which is an extension of an analytical flame tracking model based on the linearized G-equation, considers the flame impulse response to a local, impulsive, infinitesimal perturbation that is transported by convection from the flame base towards the flame surface. It is shown that the contributions of laminar flame speed and heat of reaction to the impulse response exhibit a local behavior, i.e. the flame responds at the moment when and at the location where the equivalence ratio perturbation reaches the flame surface. The time lag of this process is related to a convective time scale, which corresponds to the convective transport of fuel from the base of the flame to the flame surface. On the contrary, the flame surface area contribution exhibits a non-local behavior: albeit fluctuations of the flame shape are generated locally due to a distortion of the kinematic balance between flame speed and the flow velocity, the resulting wrinkles in flame shape are then transported by convection towards the flame tip with the restorative time scale. The impact of radial non-uniformity in equivalence ratio perturbations on the flame impulse response is demonstrated by comparing the impulse responses for uniform and parabolic radial profiles. Considerable deviation in the phase of the flame transfer function, which is important for thermo-acoustic stability, is observed.

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