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.

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

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Davide Laera ◽  
Kevin Prieur ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Sergio M. Camporeale ◽  
...  
Keyword(s):  
Heat Release ◽  
Harmonic Balance ◽  
Transverse Mode ◽  
Operating Conditions ◽  
Test Facility ◽  
Nonlinear Stability Analysis ◽  
Rate Fluctuation ◽  
Annular Combustor ◽  
Adequate Representation ◽  
Flame Describing Function

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). 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 each of the 16 burners is compact with respect to the transverse mode wavelength, and the 16 flames occupy the same volume, this distribution of heat release is not compact in the azimuthal direction and 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.

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.

Experimental Inverstigations On the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals with Embedded Pressure Sensors

2021 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB, the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

scholarly journals Flame Dynamics Intermittency in the Bi-Stable Region Near a Subcritical Hopf Bifurcation

2017 ◽  
Author(s):  
D. Ebi ◽  
A. Denisov ◽  
G. Bonciolini ◽  
E. Boujo ◽  
N. Noiray
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Acoustic Pressure ◽  
Oscillation Amplitude ◽  
Stable Region ◽  
Describing Function ◽  
Acoustic Damping ◽  
Intermittent Behavior ◽  
Flame Describing Function

We report experimental evidence of thermoacoustic bi-stability in a lab-scale turbulent combustor over a well-defined range of fuel-air equivalence ratios. Pressure oscillations are characterized by an intermittent behavior with “bursts”, i.e. sudden jumps between low and high amplitudes occurring at random time instants. The corresponding probability density functions of the acoustic pressure signal show clearly separated maxima when the burner is operated in the bi-stable region. A flame describing function, which links acoustic pressure to heat release rate fluctuations, is estimated at the modal frequency from simultaneously recorded flame chemiluminescence and acoustic pressure. The representation of its statistics is new and particularly informative. It shows that this describing function is characterized, in average, by a nearly constant gain and by a significant drift of the phase as function of the oscillation amplitude. This finding suggests that the bi-stability does not result from an amplitude-dependent balance between flame gain and acoustic damping, but rather from the non-constant phase difference between the acoustic pressure and the coherent fluctuations of heat release rate.

scholarly journals Measurement of Air-Fuel Ratio Fluctuations Caused by Combustor Driven Oscillations

1998 ◽  
Author(s):  
Rajiv Mongia ◽  
Robert Dibble ◽  
Jeff Lovett
Keyword(s):  
Power Spectrum ◽  
Mole Fraction ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Premixed Combustion ◽  
Pollutant Emissions ◽  
Combustion Instabilities ◽  
Pressure Oscillations ◽  
Lean Premixed Combustion ◽  
Lean Premixed

Lean premixed combustion has emerged as a method of achieving low pollutant emissions from gas turbines. A common problem of lean premixed combustion is combustion instability. As conditions inside lean premixed combustors approach the lean flammability limit, large pressure variations are encountered. As a consequence, certain desirable gas turbine operating regimes are not approachable. In minimizing these regimes, combustor designers must rely upon trial and error because combustion instabilities are not well understood (and thus difficult to model). When they occur, pressure oscillations in the combustor can induce fluctuations in fuel mole fraction that can augment the pressure oscillations (undesirable) or dampen the pressure oscillations (desirable). In this paper, we demonstrate a method for measuring the fuel mole fraction oscillations which occur in the premixing section during combustion instabilities produced in the combustor that is downstream of the premixer. The fuel mole fraction in the premixer is measured with kHz resolution by the absorption of light from a 3.39 μm He-Ne laser. A sudden expansion combustor is constructed to demonstrate this fuel mole fraction measurement technique. Under several operating conditions, we measure significant fuel mole fraction fluctuations that are caused by pressure oscillations in the combustion chamber. Since the fuel mole fraction is sampled continuously, a power spectrum is easily generated. The fuel mole fraction power spectrum clearly indicates fuel mole fraction fluctuation frequencies are the same as the pressure fluctuation frequencies under some operating conditions.

Life Prediction of Directionally Solidified Air Cooled HPT Gas Turbine Blade Used in a Supersonic Aircraft Using FEM

2013 ◽  
Author(s):  
S. Esakki Muthu ◽  
S. Dileep ◽  
S. Saji Kumar ◽  
D. K. Girish
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Operating Conditions ◽  
Test Facility ◽  
Time To Failure ◽  
Generation Process ◽  
Gas Turbine Blade ◽  
Directionally Solidified ◽  
Life Estimation ◽  
Supersonic Aircraft

Life estimation of Directionally Solidified (DS) MARM-247 HPT gas turbine blade used in a turbofan engine of a supersonic aircraft is presented. These blades were drafted into the engine as a replacement for the polycrystal (NIMONIC) blades since a more efficient, reliable and durable material with high strength and temperature resistance was required to further enhance the life of the turbine blade and the efficiency of the power generation process. The supersonic aircraft is having a repeated mission cycle of a fast acceleration from idle, a 1hr cruise at Mach 1.5 and a fast deceleration to idle. The mission cycle which is a repetition of acceleration, cruise and deceleration cycles can produce wide variety of complex loading conditions which can result in HCF, LCF and creep damage of the turbine blade. Empirical equation of the universal slope developed by Manson was used to estimate the damage component due to LCF. The cumulative stresses and strains due to creep as a function of time was determined using Time hardening rule. Creep data for MARM-247 was correlated using LMP to predict the lives to 1% of creep strain at worst possible combination of temperature and stress value. Damage due to creep per mission cycle was determined using Life fraction Rule proposed by Robinson and Taira. The vibration characteristics of the turbine blade were predicted using Modal analysis. Campbell diagram was plotted to ascertain whether any nozzle passing frequency fall within the working range of the blade. Harmonic analysis was carried out to evaluate the magnitude of the alternating stresses resulting from the blade vibrations at resonance during the acceleration and deceleration cycle. HCF life of the turbine blade was assessed using Goodman diagram. The total damage of the turbine blade per mission cycle due to the above loading was assumed as the combination of the individual damage due to fatigue and creep. Time to failure under combined creep and fatigue damage was estimated using linear damage rule. Non linear features of FEA tool ANSYS12.0 was exploited to calculate the stress distribution, creep, plastic and the total strain encountered by the turbine blade as a function of mission cycle time. The loading spectrum associated with the mission cycle which includes the temperature, gas pressure and the speed profiles were obtained from a sophisticated engine ground test facility which was configured to simulate actual engine operating conditions. The proposed method of cyclic life estimation using FEM was validated by performing various component and engine level tests. A good agreement was observed between the calculated and observed blade lives.

Combustion Improvement System in Boilers and Incinerators

2003 ◽  
Author(s):  
Wlodzimierz Blasiak ◽  
Weihong Yang
Keyword(s):  
Temperature Distribution ◽  
Heat Release ◽  
Combustion Chamber ◽  
Flue Gas ◽  
Operating Conditions ◽  
Waste Incinerator ◽  
The Novel ◽  
Biomass Waste ◽  
Injection Angle ◽  
Waste Incinerators

This work presents the main features, advantages and evaluation of applications of the novel “Ecotube” combustion improvement and emission reduction system by Ecomb AB of Sweden and Synterprise, LLC of Chattanooga, Tennessee. In the Ecotube system, the nozzles used for mixing are put on the suitable position inside the combustion chamber to control uniformity of temperature, mixing and reactants distribution in boilers and incinerators since the formation and reduction of pollutants (NO, CO and VOC) and in-furnace reduction processes (Air/Fuel staging, SNCR, flue gas recirculation and SOx reduction by dry sorbent injection) are related directly to mixing in a combustion chamber. The novel Ecotube combustion improvement system allows better control of mixing of the gases for example from a primary combustion zone with secondary combustion air or a recirculated flue gas. By means of the novel system it is possible to better control the residence time and to some degree gas phase temperature distribution as well as the heat release distribution in the furnace of the waste incinerators or boilers. This new combustion improvement system can be applied to supply different gas or liquid media — for example air, fuel, urea or even solid powder. Using the system a more efficient and environmentally clean combustion or incineration process can be performed. The Ecotube System may be used to meet increasingly stringent environmental emissions regulations, such as NOx SIP Call, while it delivers added benefits of reduced and stabilized CO and reduced fly ash and improved boiler efficiency. The study tool used in this work to present influence of the Ecotube system design on temperature as well as uniformity of reactants and flow field is numerical modeling. Using this tool, the influence of the position of the Ecotube system and the injection angle of the nozzles are studied. The studied boilers included the biomass waste incinerator, municipal solid waste incinerator and coal fired boiler. The concept of the Heat Release Distribution Ratio is proposed to classify the heat release inside the upper furnace of the boilers or incinerators. The results show that Ecotube spreads reaction zone over a larger furnace volume. The furnace flame occupation coefficient can be as high as 45% with the Ecotube system and it is around 40% higher comparing with the conventional multinozzle mixing system. Ecotube system allows keeping far more uniform heat release distribution, more uniform temperature distribution, and thus longer life of the heat transfer surfaces inside the furnace. Position of the Ecotube system and the injection angle of the nozzles are of primary importance and can be used as a technical parameter to control the boiler operation at different loads and varying operating conditions.

The Effect of Heat Transfer Coefficient Increase on Tip Clearance Control in H.P. Compressors in Gas Turbine Engine

2013 ◽  
Author(s):  
Godwin Ita Ekong ◽  
Christopher A. Long ◽  
Peter R. N. Childs
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Time Constant ◽  
Gas Turbine Engine ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Test Facility ◽  
Turbine Engine

Compressor tip clearance for a gas turbine engine application is the radial gap between the stationary compressor casing and the rotating blades. The gap varies significantly during different operating conditions of the engine due to centrifugal forces on the rotor and differential thermal expansions in the discs and casing. The tip clearance in the axial flow compressor of modern commercial civil aero-engines is of significance in terms of both mechanical integrity and performance. In general, the clearance is of critical importance to civil airline operators and their customers alike because as the clearance between the compressor blade tips and the casing increases, the aerodynamic efficiency will decrease and therefore the specific fuel consumption and operating costs will increase. This paper reports on the development of a range of concepts and their evaluation for the reduction and control of tip clearance in H.P. compressors using an enhanced heat transfer coefficient approach. This would lead to improvement in cruise tip clearances. A test facility has been developed for the study at the University of Sussex, incorporating a rotor and an inner shaft scaled down from a Rolls-Royce Trent aero-engine to a ratio of 0.7:1 with a rotational speed of up to 10000 rpm. The idle and maximum take-off conditions in the square cycle correspond to in-cavity rotational Reynolds numbers of 3.1×106 ≤ Reφ ≤ 1.0×107. The project involved modelling of the experimental facilities, to demonstrate proof of concept. The analysis shows that increasing the thermal response of the high pressure compressor (HPC) drum of a gas turbine engine assembly will reduce the drum time constant, thereby reducing the re-slam characteristics of the drum causing a reduction in the cold build clearance (CBC), and hence the reduction in cruise clearance. A further reduction can be achieved by introducing radial inflow into the drum cavity to further increase the disc heat transfer coefficient in the cavity; hence a further reduction in disc drum time constant.

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