scholarly journals A Preliminary Calculation of the Combustion Recirculating Flow Behind Flame-Holders

1985 ◽  
Author(s):  
C. F. Zeng ◽  
J. X. Zhao ◽  
Z. T. Ding
Keyword(s):  
Flow Field ◽  
Equivalence Ratio ◽  
Variable Density ◽  
Combustion Model ◽  
Preliminary Calculation ◽  
Flame Spreading ◽  
Inlet Velocity ◽  
Recirculating Flow ◽  
Combustion Flow ◽  
Recirculation Length

In this paper the numerical method is adopted to predict the combustion recirculating flow behind flame-holders. A modified k-ε turbulence model and Magnussen’s combustion model are employed. Becouse of the large variation of density in combustion flow field, the influences of variable density have been considered. The results predicted include: the combustion recirculating flow field and the flame spreading; the variation of recirculation length with equivalence ratio, and inlet velocity, etc. All of these are qualitatively good comparing with experimental results.

Study of Combustion Instabilities Imposed by Inlet Velocity Disturbance in Combustor Using LES

2009 ◽  
Author(s):  
Kenji Sato ◽  
Ed Knudsen ◽  
Heinz Pitsch
Keyword(s):  
Transfer Function ◽  
Flow Field ◽  
Heat Release ◽  
Combustion Chamber ◽  
Combustion Process ◽  
Variable Density ◽  
Combustion Model ◽  
Combustion Instabilities ◽  
Inlet Velocity ◽  
Good Agreement

Stable combustion is one of the most important requirements for the development of heavy duty gas turbine engines that comply with stringent environmental regulations at high firing temperatures. In this research, one of the typical combustion instabilities which is caused by an acoustically forced velocity disturbance is investigated using variable density LES simulations. The G-equation approach for LES is used as the combustion model [1], and an experiment by Balachandran et al. [2, 3] is selected for case study. The velocity profiles in the experimental combustion chamber are compared with experimentally measured data at non-reacting conditions and it is confirmed that these are in good agreement. At the reacting conditions, predicted flame shapes are compared with OH PLIF measurements. The transfer function of the heat release due to inlet velocity forcing at 40 Hz and 160 Hz frequencies is also compared with the experimental data. These are in good agreement, including the nonlinear response of heat release. The transfer function is highly related to the flow field. The non-linearity of the transfer function can be traced to the interaction of the flow field in the combustion chamber with the combustion process itself.

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.

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.

Ozone-Assisted Combustion—Part I: Literature Review and Kinetic Study Using Detailed n-Heptane Kinetic Mechanism

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Christopher Depcik ◽  
Michael Mangus ◽  
Colter Ragone
Keyword(s):  
Ignition Delay ◽  
Equivalence Ratio ◽  
Atomic Oxygen ◽  
Direct Injection ◽  
Kinetic Mechanism ◽  
Combustion Model ◽  
Ozone Decomposition ◽  
Compression Ignition ◽  
Review Of The Literature ◽  
Compression Ignition Engine

In this first paper, the authors undertake a review of the literature in the field of ozone-assisted combustion in order to summarize literature findings. The use of a detailed n-heptane combustion model including ozone kinetics helps analyze these earlier results and leads into experimentation within the authors' laboratory using a single-cylinder, direct-injection compression ignition engine, briefly discussed here and in more depth in a following paper. The literature and kinetic modeling outcomes indicate that the addition of ozone leads to a decrease in ignition delay, both in comparison to no added ozone and with a decreasing equivalence ratio. This ignition delay decrease as the mixture leans is counter to the traditional increase in ignition delay with decreasing equivalence ratio. Moreover, the inclusion of ozone results in slightly higher temperatures in the cylinder due to ozone decomposition, augmented production of nitrogen oxides, and reduction in particulate matter through radial atomic oxygen chemistry. Of additional importance, acetylene levels decrease but carbon monoxide emissions are found to both increase and decrease as a function of equivalence ratio. This work illustrates that, beyond a certain level of assistance (approximately 20 ppm for the compression ratio of the authors' engine), adding more ozone has a negligible influence on combustion and emissions. This occurs because the introduction of O3 into the intake causes a temperature-limited equilibrium set of reactions via the atomic oxygen radical produced.

Simulation of Two-Dimensional Turbulent Recirculating Flow Field Behind a V-Shaped Bluff Body

1994 ◽  
Author(s):  
Z. Gu ◽  
M. A. R. Sharif
Keyword(s):  
Flow Field ◽  
Bluff Body ◽  
Flame Stabilization ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Combustion Chambers ◽  
Recirculating Flow ◽  
Conservative Form ◽  
Curvilinear Grid ◽  
Predictor Corrector

Abstract The two-dimensional turbulent recirculating flow fields behind a V-shaped bluff body have been investigated numerically. Similar bluff bodies are used in combustion chambers for flame stabilization. The governing transport equations in conservative form are solved by a pressure based predictor-corrector method. The standard k-ϵ turbulence closure model and a boundary fitted multi-block curvilinear grid system are used in the computation. The code is validated against turbulent flow over a backward facing step problem. The predicted flow field behind the bluff body is also compared with experiment. It is found that while the qualitative features of the flow are well predicted, there is quantitative disagreement between the measurement and prediction. This disagreement can be partially attributed to the k-ϵ turbulence model which is known to be inadequate for recirculating flows. Parametric investigation of the flow field by varying the shape and size of the bluff body is also performed and the results are reported.

Absorption Model of Wavelength Modulation Spectroscopy in Combustion Flow Field

2019 ◽  
Vol 46 (7) ◽  
pp. 0711001
Author(s):  
张步强 Buqiang Zhang ◽  
许振宇 Zhenyu Xu ◽  
刘建国 Jianguo Liu ◽  
夏晖晖 Huihui Xia ◽  
聂伟 Wei Nie ◽  
...  
Keyword(s):  
Flow Field ◽  
Wavelength Modulation Spectroscopy ◽  
Absorption Model ◽  
Wavelength Modulation ◽  
Modulation Spectroscopy ◽  
Combustion Flow

scholarly journals Research on combustion flow field imaging method based on ray casting algorithm

AIP Advances ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 055022 ◽  
Author(s):  
Min Yao ◽  
Yueqi Zhang ◽  
Min Zhao ◽  
Ruipeng Guo ◽  
Jun Xu
Keyword(s):  
Flow Field ◽  
Imaging Method ◽  
Ray Casting ◽  
Combustion Flow ◽  
Ray Casting Algorithm ◽  
Field Imaging

Mean Flow Measurements Near the Plane of an Open Rotor Operating with an Inlet Velocity Gradient

1981 ◽  
Vol 103 (2) ◽  
pp. 445-450
Author(s):  
M. L. Billet
Keyword(s):  
Flow Field ◽  
Velocity Profile ◽  
Velocity Gradient ◽  
Vortex Motion ◽  
Field Measurements ◽  
Velocity Data ◽  
Mean Flow ◽  
Flow Measurements ◽  
Inlet Velocity ◽  
Open Rotor

As part of a study on the structure of a trailing vortex, laser doppler anemometer (LDA) measurements were made of the flow field near an open rotor having an inlet velocity gradient. The measurements were made in the 1.22 m dia water tunnel of the Applied Research Laboratory at The Pennsylvania State University. Velocity data were obtained for rotor inlet and outlet flow fields for several different inlet velocity gradients. Velocity data were also obtained downstream of the rotor plane that shows the vortex structure. Flow field measurements show the development of the downstream vortex motion. Small variations in the inlet velocity gradient near the rotor wall caused large differences in the structure of the trailing vortex. In addition, a measured downstream velocity profile is compared with a calculated velocity profile.

STAGNATION LAMINAR PREMIXED CH4/AIR FLAME SUBJECTED TO THE EQUIVALENCE RATIO OSCILLATIONS

2015 ◽  
Vol 76 (1) ◽  
Author(s):  
Mohd Rosdzimin Abdul Rahman ◽  
Hishashi Tomita ◽  
Takeshi Yokomori ◽  
Toshihisa Ueda
Keyword(s):  
Flow Field ◽  
Equivalence Ratio ◽  
Reduction Method ◽  
The Other ◽  
Stagnation Flow ◽  
Velocity Perturbation ◽  
Sinusoidal Shape ◽  
Premixed Laminar ◽  
Oscillation Frequencies ◽  
Flame Position

The effect of the equivalence ratio oscillation on a premixed laminar CH4/air flame motion was studied experimentally with equivalence ratio oscillation frequencies of 2 to 15 Hz at lean equivalence ratio using stagnation flow field burner. Novel oscillator does the oscillation conditions and turbulence reduction method is used to suppress the velocity perturbation. The flame position variations at 2, 5, 10 and 15 Hz oscillation frequencies were significantly small when the amplitude of the equivalence ratio oscillation was zero. On the other hand, increase in amplitudes of the equivalence ratio oscillation increased the flame position variation significantly. The flame moved in sinusoidal shape and it can be clearly seen that the flame movement’s amplitude was proportional to the amplitudes of the equivalence ratio variations. This result showed that the velocity perturbation is significantly suppressed by turbulence reduction method in the examination range.

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