scholarly journals High Amplitude Combustion Instabilities in an Annular Combustor Inducing Pressure Field Deformation and Flame Blow Off

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Guillaume Vignat ◽  
Daniel Durox ◽  
Antoine Renaud ◽  
Sébastien Candel
Keyword(s):  
Velocity Field ◽  
Pressure Distribution ◽  
Pressure Field ◽  
High Amplitude ◽  
Nodal Line ◽  
Operating Conditions ◽  
Injection System ◽  
Combustion Instabilities ◽  
Wide Range ◽  
Annular Combustor

Abstract This article reports experiments carried out in the laboratory scale annular combustor MICCA-spray equipped with multiple swirling spray injectors. The experimental setup consists in an air plenum connected to a combustion chamber formed by two concentric cylindrical quartz tubes, allowing full optical access to the flames. A new injection system is introduced and characterized. For a wide range of operating conditions, strong combustion instabilities are observed, but the focus of this article is placed on very high amplitude combustion instabilities coupled by a standing azimuthal mode. New results are obtained using a higher order reconstruction method for the pressure field: its shape is shown to be modified during high amplitude oscillation, leading to asymmetries of the pressure distribution in the system. Flame blow off occurs near the pressure nodal line when a critical level of oscillation is reached. A method is proposed to reconstruct the acoustic velocity field just before blow off occurs and in this way determine the blow off threshold. It is found that the pressure distribution, velocity field, and blow off pattern become asymmetric as the amplitude of oscillation increases and that this process is accompanied by a rapid shift in frequency of oscillation. Another notable result is that the heat release rate in the flames on the same side of the nodal line is not perfectly in phase and that the phase differences become larger as the amplitude of oscillation increases.

scholarly journals High Amplitude Combustion Instabilities in an Annular Combustor Inducing Pressure Field Deformation and Flame Blow-Off

2019 ◽  
Author(s):  
Guillaume Vignat ◽  
Daniel Durox ◽  
Antoine Renaud ◽  
Sébastien Candel
Keyword(s):  
Velocity Field ◽  
Pressure Field ◽  
High Amplitude ◽  
Nodal Line ◽  
Operating Conditions ◽  
Injection System ◽  
Reconstruction Method ◽  
Combustion Instabilities ◽  
Wide Range ◽  
Annular Combustor

Abstract This article reports experiments carried out in the laboratory scale annular combustor MICCA-Spray equipped with multiple swirling spray injectors. The experimental setup consists in an air plenum connected to a combustion chamber formed by two concentric cylindrical quartz tubes, allowing full optical access to the flames. A new injection system is introduced and characterized. For a wide range of operating conditions, strong combustion instabilities are observed, but the focus of this article is placed on very high amplitude combustion instabilities coupled by a standing azimuthal mode. It is found that the frequency decreases as the amplitude of the thermoacoustic oscillation grows. New results are obtained using a higher order reconstruction method for the pressure field: its shape is shown to be modified during high amplitude oscillation, leading to asymmetries of the pressure distribution in the system. Flame blow-off occurs near the pressure nodal line when a critical level of oscillation is reached. A method is proposed to reconstruct the acoustic velocity field just before blow-off occurs. Both the velocity field and the blow-off pattern are skewed. The effect of flame blow-off on the frequency of the oscillation is discussed, and it is shown that it leads to the distortion of the pressure field. A new result is also that the phase of the flame response to acoustic perturbation can vary among flames on the same side of the nodal line.

A Novel Strategy for Passive Control of Combustion Instabilities Through Modification of Flame Dynamics

2008 ◽  
Author(s):  
Nicolas Noiray ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Se´bastien Candel
Keyword(s):  
Passive Control ◽  
Full Range ◽  
Premixed Flames ◽  
Perforated Plate ◽  
Operating Conditions ◽  
System Stability ◽  
Injection System ◽  
Coherent Motion ◽  
Dynamical Response ◽  
Combustion Instabilities

Passive control of combustion instabilities is explored in the case of systems featuring a collection of premixed flames. The method devised in this research differs from the general strategies employed to passively hinder the growth of acoustic-combustion oscillations by augmenting acoustic damping. Dissipation of acoustic energy is usually obtained by connecting Helmholtz resonators or quarter wave type cavities or by placing perforated plate linings around the system. While these systems effectively reduce pressure oscillations, optimum performance is not always obtained over the full range of operating conditions and their implementation requires substantial space which is not often available in practice. Conceptually, these standard techniques deal with the consequences of combustion instabilities but not with the driving sources. It is shown here that an alternative solution may be to directly act on the causes of the onset of thermo-acoustic coupling. The basic idea is to modify the flames dynamics using the dynamical response of the injection system. The principle of the passive control strategy proposed on this basis is to counteract the onset of oscillations by tackling the underlying causes. The injection system is modified to avoid a coherent motion of the flames when they are submitted to an acoustic modulation and reduce the coupling between acoustic perturbations and heat release fluctuations. Numerical simulations and experimental data are presented and one may infer that the method could bring a substantial improvement to the system stability. The efficiency of this technique is demonstrated in the case of small premixed flames anchored on a multipoint injection system (the configuration is that of a premixed gaseous-fueled multipoint dump combustor), but the principle is more general and can be extended to larger scale turbulent combustors featuring a collection of flames.

Conjugate Heat Transfer Analysis of a Small Annular Combustor With Centrifugal Fuel Injection System

2019 ◽  
Author(s):  
Rampada Rana ◽  
Alosri Prajwal ◽  
Gullapalli Sivaramakrishna ◽  
Raju Dharappa Navindgi ◽  
Nagalingam Muthuveerappan
Keyword(s):  
Structural Integrity ◽  
Fuel Injection ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Injection System ◽  
Maximum Temperature ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Ansys Fluent ◽  
Annular Combustor

Abstract Over the years, the requirements of higher specific thrust and lower specific fuel consumption have been necessitating a continual increase in the maximum temperature and pressure in gas turbine engines. However, such an increase has a direct impact on the structural integrity of various modules of the engine; combustor being one of the severely affected modules. This makes the combustor designer’s task of achieving the targeted life of liner, the hottest component of combustor, a challenging one. Estimation of liner metal temperature, thereby arriving at the combustor life, is an essential part of the design process. In the present study, CHT analysis of a radial annular combustor has been carried out. RANS based analysis of a sector combustor with periodicity in flow and geometry has been performed at realistic engine operating conditions using ANSYS Fluent. Predicted liner metal temperatures have been compared with the measured data and a close agreement has been noted between them, the maximum variation being ± 10%.

Experimental Investigation of Self-Excited Combustion Instabilities in a Lean, Premixed, Gas Turbine Combustor at High Pressure

2017 ◽  
Author(s):  
Timo Buschhagen ◽  
Rohan Gejji ◽  
John Philo ◽  
Lucky Tran ◽  
J. Enrique Portillo Bilbao ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Operating Conditions ◽  
Chamber Pressure ◽  
Dynamic Mode ◽  
Combustion Instabilities ◽  
Compression Phase ◽  
Wide Range ◽  
Lower Amplitude ◽  
Lean Premixed

An experimental investigation of self-excited combustion instabilities in a high pressure, single-element, lean, premixed, natural gas dump-combustor is presented in this paper. The combustor is designed for optical access and is instrumented with high frequency pressure transducers at multiple axial locations. A parametric survey of operating conditions including inlet air temperature and equivalence ratio has been performed, which presents a wide range of peak to peak pressure fluctuations (p′) of the mean chamber pressure (pc). Two cases, Flame A and B with p′ /pc = 28% and p′/pc = 15% respectively, both presenting self-excited instabilities at the fundamental longitudinal (1L) mode of the combustion chamber, are discussed to study the coupling mechanism between flame-vortex interactions and the acoustic field in the chamber. OH*-chemiluminescence is used to obtain a map of global heat release distribution in the combustor. Phase conditioned analysis and Dynamic Mode Decomposition (DMD) analysis is performed, to highlight the contrasting mechanisms that lead to the two distinct instability regimes. Flame interactions with shear layer vortex structures just downstream of the dump plane during the compression phase of the acoustic cycle are found to augment the instability amplitude. Flame A engages strongly in this coupling, whereas Flame B is less affected and establishes a lower amplitude limit cycle.

Impact of Heat Release Distribution on the Spinning Modes of an Annular Combustor With Multiple Matrix Burners

2016 ◽  
Author(s):  
Davide Laera ◽  
Kevin Prieur ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Sergio M. Camporeale ◽  
...  
Keyword(s):  
Heat Release ◽  
Operating Conditions ◽  
Test Facility ◽  
Combustion Instabilities ◽  
Nonlinear Stability Analysis ◽  
Rate Fluctuation ◽  
Annular Combustor ◽  
Adequate Representation ◽  
Aero Engines ◽  
Flame Describing Function

Annular combustors of aero-engines and gas turbine are often affected by thermo-acoustic combustion instabilities coupled by azimuthal modes. Previous experiments as well as theoretical and numerical investigations indicate that the coupling modes involved in this process may be standing or spinning but they provide diverse interpretations of the occurrence of these two types of oscillations. The present article reports a numerical analysis of instability coupled by a spinning mode in an annular combustor. This corresponds to experiments carried out on the MICCA test facility equipped with 16 matrix burners. Each burner response is represented by means of a global experimental flame describing function (FDF) and it is considered that the flames are sufficiently compact to interact with the mode without mutual interactions with adjacent burning regions. A harmonic balance nonlinear stability analysis is carried out by combining the FDF with a Helmholtz solver to determine the system dynamics trajectories in a frequency-growth rate plane. The influence of the distribution of the volumetric heat release corresponding to each burner is investigated in a first stage. Even though the 16 burners are all compact with respect to the acoustic wavelength considered and occupy the same volume, simulations reveal an influence of this volumetric distribution on frequencies and growth rates. This study emphasizes the importance of providing a suitable description of the flame zone geometrical extension and correspondingly an adequate representation of the level of heat release rate fluctuation per unit volume. It is found that these two items can be deduced from a knowledge of the heat release distribution under steady state operating conditions. Once the distribution of the heat release fluctuations is unequivocally defined, limit cycle simulations are performed. For the conditions explored, simulations retrieve the spinning nature of the self-sustained mode that was identified in the experiments both in the plenum and in the combustion chamber.

The Effect of Elastic Distortions on Journal Bearing Performance

1967 ◽  
Vol 89 (4) ◽  
pp. 409-415 ◽  
Author(s):  
J. O’Donoghue ◽  
D. K. Brighton ◽  
C. J. K. Hooke
Keyword(s):  
Exact Solution ◽  
Pressure Distribution ◽  
Elastic Deformation ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Wide Range ◽  
Constant Viscosity ◽  
Outside Diameter

This paper presents a solution to the problem of hydrodynamic lubrication of journal bearings taking into account the elastic distortions of the shaft and the bearing. The exact solution for determining the elastic deformation for a given pressure distribution around a bearing is given, together with the reiterative procedure adopted to find the pressure distribution which satisfies both the hydrodynamic and elastic requirements of the system. Results are given which have been derived for a material with a Poisson’s ratio of 0.28, but other values such as 0.33 do not incur substantial errors. The results can be applied to a wide range of operating conditions using the nondimensional group of terms suggested in the paper. The bearing is assumed to be infinite in length, and infinite in thickness. The latter assumption is shown to be valid for a particular case where the outside diameter of the bearing shell is 3.5 times the shaft diameter. A further assumption in the calculation is a condition of constant viscosity of the lubricant existing around the bearing.

Methods for Specific Emission Evaluation in SI Engines Based on Calculation Procedures of Air-Fuel Ratio: Development, Assessment and Critical Comparison

2003 ◽  
Author(s):  
Stefano d’Ambrosio ◽  
Ezio Spessa ◽  
Alberto Vassallo
Keyword(s):  
Operating Conditions ◽  
Sensor Data ◽  
Injection System ◽  
Specific Mass ◽  
Nox Formation ◽  
Exhaust Gases ◽  
Wide Range ◽  
Specific Emissions ◽  
Ic Engines ◽  
Working Parameters

New computational procedures are proposed for evaluating the exhaust brake specific mass emissions of each pollutant species in IC engines. The procedures start from the chemical reaction of fuel with combustion air and, basing on the measured exhaust raw emissions THC, CH4, NOx, CO, O2, CO2, calculate the volume fractions of the compounds in the exhaust gases, including those that are not usually measured, such as water, nitrogen and hydrogen. The method also takes the effects of various fuel and combustion air compositions into account, with particular reference to different natural gas blends as well as to the presence of water vapor, CO2, Ar and He in the combustion air. The molecular mass of the exhaust gases is then evaluated and the brake specific emissions can be obtained if the exhaust flow rate and the engine power output are measured. The methods stem from the extension of the different procedures that are used in the literature to evaluate α from measured raw volume emissions of IC engines running on conventional fuels. In the present study, a new algorithm is developed so as to generalize and refine all the mentioned α evaluation procedures, keeping conventional and alternative fuel compositions into account. First, the algorithm is applied to the evaluation of α in an automotive bi-fuel SI engine running on gasoline and CNG under a wide range of operating conditions. The α evaluation tests were carried out with a carefully controlled multipoint sequential injection system for both gasoline and CNG fueling. The results are compared to those obtained from the directly measured air and fuel mass flow rates as well as from more conventional UEGO sensor data. The algorithm is then applied to the evaluation of the brake specific mass emission of each pollutant species under gasoline and CNG engine operations for different steady-state working conditions. The sensitivity of results to the main engine working parameters, the influence of environmental conditions (in particular the effect of air humidity on NOx formation) and the experimental uncertainties are determined. The specific emissions calculated from the proposed algorithm are finally compared to those obtained by applying SAE and ISO recommended practices.

Experimental Investigation of Self-Excited Combustion Instabilities in a Lean, Premixed, Gas Turbine Combustor at High Pressure

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Timo Buschhagen ◽  
Rohan Gejji ◽  
John Philo ◽  
Lucky Tran ◽  
J. Enrique Portillo Bilbao ◽  
...  
Keyword(s):  
High Pressure ◽  
Combustion Chamber ◽  
Operating Conditions ◽  
Chamber Pressure ◽  
Dynamic Mode ◽  
Single Element ◽  
Combustion Instabilities ◽  
Wide Range ◽  
Lower Amplitude ◽  
Lean Premixed

Self-excited combustion instabilities in a high pressure, single-element, lean, premixed, natural gas (NG) dump-combustor are investigated. The combustor is designed for optical access and instrumented with high frequency pressure transducers at multiple axial locations. A parametric survey of operating conditions including inlet air temperature and equivalence ratio has been performed, resulting in a wide range of pressure fluctuation amplitudes (p′) of the mean chamber pressure (pCH). Two representative cases, flames A and B with p′/pCH=23% and p′/pCH=12%, respectively, both presenting self-excited instabilities at the fundamental longitudinal (1L) mode of the combustion chamber, are discussed to study the coupling mechanism between flame-vortex interactions and the acoustic field in the chamber. 10 kHz OH*-chemiluminescence imaging was performed to obtain a map of the global heat release distribution. Phase conditioned and Rayleigh index analysis as well as dynamic mode decomposition (DMD) is performed to highlight the contrasting mechanisms that lead to the two distinct instability regimes. Flame interactions with shear layer vortex structures downstream of the backward-facing step of the combustion chamber are found to augment the instability magnitude. Flame A engages strongly in this coupling, whereas flame B is less affected and establishes a lower amplitude limit cycle.

Effect of Natural Gas Composition on Low NOx Burners Operation in Heavy Duty Gas Turbine

2019 ◽  
Author(s):  
Serena Romano ◽  
Matteo Cerutti ◽  
Giovanni Riccio ◽  
Antonio Andreini ◽  
Christian Romano
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Operating Conditions ◽  
Fuel Composition ◽  
Gas Composition ◽  
Heavy Duty ◽  
Wide Range ◽  
Annular Combustor ◽  
Heavy Duty Gas Turbine ◽  
The Impact

Abstract Development of lean-premixed combustion technology with low emissions and stable operation in an increasingly wide range of operating conditions requires a deep understanding of the mechanisms that affect the combustion performance or even the operability of the entire gas turbine. Due to the relative wide range of natural gas composition supplies and the increased demand from Oil&Gas customers to burn unprocessed gas as well as LNG with notable higher hydrocarbons (C2+) content; the impact on gas turbine operability and combustion related aspects has been matter of several studies. In this paper, results of experimental test campaign of an annular combustor for heavy-duty gas turbine are presented with focus on the effect of fuel composition on both emissions and flame stability. Test campaign involved two different facilities, a full annular combustor rig and a full-scale prototype engine fed with different fuel mixtures of natural gas with small to moderate C2H6 content. Emissions trends and blowout for several operating conditions and burner configurations have been analyzed. Modifications to the burner geometry and fuel injection optimization have shown to be able to reach a good trade-off while keeping low NOx emissions in stable operating conditions for varying fuel composition.

Experimental and Numerical Investigations of Flowpath Profiling on Secondary Flow Losses in a Turbine Control Stage

2013 ◽  
Author(s):  
Nils Moser ◽  
Peter Steinhoff ◽  
Franz Joos
Keyword(s):  
Pressure Distribution ◽  
Secondary Flow ◽  
Guide Vane ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Formation Mechanisms ◽  
Guide Vanes ◽  
Numerical Investigations ◽  
Control Stage ◽  
Wide Range

The numerically and experimentally investigated industrial steam turbine control stage is derived from a real design. Due to the production process and costs of the guide vanes for control stages of steam turbines the flowpath profiling is rotationally symmetric. However the combination of the two-dimensional shroud contour and the flow deflection in the guide vane results in a fully three-dimensional end wall contour having a strong influence on the secondary flow features in the turbine control stage. To obtain an improved profile for the nozzle shroud the reduction of the total pressure loss over the guide vanes is taken as an optimization criterion. The three-dimensional contour generates a diffuser flowpath between the suction and the pressure side of two guide vanes perpendicular to the main flow direction. This diffuser geometry affects the pressure distribution over the guide vane and therefore the formation mechanisms of secondary flows. For the experimental and numerical investigations a baseline shroud design and two additional profiled contours are analyzed in detail. The control stage test rig is operated with air and is capable to represent a wide range of operating conditions. The measurements show a considerable increase of the stage efficiency and power output. The effect of the flowpath profiling on the pressure distribution over the guide vane is clearly proved.

Sign in / Sign up

Export Citation Format

Share Document