scholarly journals Radical Overshoot Phenomena in Liquid Fueled Gas Turbine Combustors

1977 ◽  
Author(s):  
R. Kollrack ◽  
L. D. Aceto
Keyword(s):  
Gas Turbine ◽  
Residence Time ◽  
Gas Turbines ◽  
Combustion Zone ◽  
Equivalence Ratio ◽  
Drop Size ◽  
Formation Rate ◽  
Liquid Fuels ◽  
No Production ◽  
No Formation

A detailed analysis is presented of the processes involved in the production of NO during the combustion of liquid fuels in gas turbines. With O and OH concentrations in excess of the equilibrium values the NO production rate displays a temporary overshoot within the primary combustion zone residence time. The contributions of temperature and reaction kinetics to this overshoot are assessed. This overshoot is strongly dependent on equivalence ratio and on pressure, with the minimum overshoot occurring at ϕ = 0.9. It increases more strongly for richer than for leaner combustion. Increasing drop size at lean or stoichiometric conditions tends to retard and diminish the overshoot of the NO formation rate while increasing its duration. At rich conditions, however, increasing drop size can cause overshoot increases. Changing degrees of premixedness for a given drop size, produces a timewise shifting of this overshoot. An assessment is made of the influences and interrelation of drop size distribution, degree of premixedness and staged fuel addition.

Evaluation of Combustion and Emissions Using Biodiesel and Blends With Kerosene in a Low NOx Gas Turbine Combustor

2010 ◽  
Author(s):  
Hu Li ◽  
Mohamed Altaher ◽  
Gordon E. Andrews
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Equivalence Ratio ◽  
Fuel Injection ◽  
Waste Cooking Oil ◽  
Industrial Applications ◽  
Liquid Fuels ◽  
Gaseous Emissions ◽  
Gas Turbine Combustor ◽  
Industrial Gas Turbines

Biofuels offer reduced CO2 emissions for both industrial and aero gas turbines. Industrial applications are more practical due to low temperature waxing problems at altitude. Any use of biofuels in industrial gas turbines must also achieve low NOx and this paper investigates the use of biofuels in a low NOx radial swirler, as used in some industrial low NOx gas turbines. A waste cooking oil derived methyl ester biodiesel (WME) has been tested on a radial swirler industrial low NOx gas turbine combustor under atmospheric pressure and 600K. The pure WME and its blends with kerosene, B20 and B50 (WME:kerosene = 20:80 and 50:50 respectively), and pure kerosene were tested for gaseous emissions and lean extinction as a function of equivalence ratio. The co-firing with natural gas (NG) was tested for kerosene/biofuel blends B20 and B50. The central fuel injection was used for liquid fuels and wall injection was used for NG. The experiments were carried out at a reference Mach number of 0.017. The inlet air to the combustor was heated to 600K. The results show that B20 produced similar NOx at an equivalence ratio of ∼0.5 and a significant low NOx when the equivalence ratio was increased comparing with kerosene. B50 and B100 produced higher NOx compared to kerosene, which indicates deteriorated mixing due to the poor volatility of the biofuel component. The biodiesel lower hydrocarbon and CO emissions than kerosene in the lean combustion range. The lean extinction limit was lower for B50 and B100 than kerosene. It is demonstrated that B20 has the lowest overall emissions. The co-firing with NG using B20 and B50 significantly reduced NOx and CO emissions.

Development and Integration of the Dual Fuel Combustion System for the MGT Gas Turbine Family

2021 ◽  
Author(s):  
Bernhard Ćosić ◽  
Frank Reiss ◽  
Marc Blümer ◽  
Christian Frekers ◽  
Franklin Genin ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Distribution System ◽  
Gas Turbines ◽  
Liquid Fuel ◽  
Fuel Injection ◽  
Liquid Fuels ◽  
Dual Fuel ◽  
Gaseous Fuels ◽  
Supply And Distribution ◽  
Industrial Gas Turbines

Abstract Industrial gas turbines like the MGT6000 are often operated as power supply or as mechanical drives. In these applications, liquid fuels like 'Diesel Fuel No.2' can be used either as main fuel or as backup fuel if natural gas is not reliably available. The MAN Gas Turbines (MGT) operate with the Advanced Can Combustion (ACC) system, which is capable of ultra-low NOx emissions for gaseous fuels. This system has been further developed to provide dry dual fuel capability. In the present paper, we describe the design and detailed experimental validation process of the liquid fuel injection, and its integration into the gas turbine package. A central lance with an integrated two-stage nozzle is employed as a liquid pilot stage, enabling ignition and start-up of the engine on liquid fuel only. The pilot stage is continuously operated, whereas the bulk of the liquid fuel is injected through the premixed combustor stage. The premixed stage comprises a set of four decentralized nozzles based on fluidic oscillator atomizers, wherein atomization of the liquid fuel is achieved through self-induced oscillations. We present results illustrating the spray, hydrodynamic, and emission performance of the injectors. Extensive testing of the burner at atmospheric and full load high-pressure conditions has been performed, before verification within full engine tests. We show the design of the fuel supply and distribution system. Finally, we discuss the integration of the dual fuel system into the standard gas turbine package of the MGT6000.

The Effect of Transient Fuel Staging on Self-Excited Instabilities in a Multi-Nozzle Model Gas Turbine Combustor

2017 ◽  
Author(s):  
Wyatt Culler ◽  
Janith Samarasinghe ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca ◽  
Jacqueline O’Connor
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Equivalence Ratio ◽  
Growth Time ◽  
Stable Operation ◽  
Time Constants ◽  
Decay Times ◽  
Fuel Staging ◽  
Passive Techniques

Combustion instability in gas turbines can be mitigated using active techniques or passive techniques, but passive techniques are almost exclusively used in industrial settings. While fuel staging, a common passive technique, is effective in reducing the amplitude of self-excited instabilities in gas turbine combustors at steady-state conditions, the effect of transients in fuel staging on self-excited instabilities is not well understood. This paper examines the effect of fuel staging transients on a laboratory-scale five-nozzle can combustor undergoing self-excited instabilities. The five nozzles are arranged in a four-around-one configuration and fuel staging is accomplished by increasing the center nozzle equivalence ratio. When the global equivalence ratio is φ = 0.70 and all nozzles are fueled equally, the combustor undergoes self-excited oscillations. These oscillations are suppressed when the center nozzle equivalence ratio is increased to φ = 0.80 or φ = 0.85. Two transient staging schedules are used, resulting in transitions from unstable to stable operation, and vice-versa. It is found that the characteristic instability decay times are dependent on the amount of fuel staging in the center nozzle. It is also found that the decay time constants differ from the growth time constants, indicating hysteresis in stability transition points. High speed CH* chemiluminescence images in combination with dynamic pressure measurements are used to determine the instantaneous phase difference between the heat release rate fluctuation and the combustor pressure fluctuation throughout the combustor. This analysis shows that the instability onset process is different from the instability decay process.

scholarly journals Prediction of Auto-Ignition Temperatures and Delays for Gas Turbine Applications

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Roda Bounaceur ◽  
Pierre-Alexandre Glaude ◽  
Baptiste Sirjean ◽  
René Fournet ◽  
Pierre Montagne ◽  
...  
Keyword(s):  
High Temperature ◽  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Equivalence Ratio ◽  
Process Conditions ◽  
Piping System ◽  
Gaseous Fuels ◽  
Auto Ignition ◽  
Wide Range

Gas turbines burn a large variety of gaseous fuels under elevated pressure and temperature conditions. During transient operations, variable gas/air mixtures are involved in the gas piping system. In order to predict the risk of auto-ignition events and ensure a safe operation of gas turbines, it is of the essence to know the lowest temperature at which spontaneous ignition of fuels may happen. Experimental auto-ignition data of hydrocarbon–air mixtures at elevated pressures are scarce and often not applicable in specific industrial conditions. Auto-ignition temperature (AIT) data correspond to temperature ranges in which fuels display an incipient reactivity, with timescales amounting in seconds or even in minutes instead of milliseconds in flames. In these conditions, the critical reactions are most often different from the ones governing the reactivity in a flame or in high temperature ignition. Some of the critical paths for AIT are similar to those encountered in slow oxidation. Therefore, the main available kinetic models that have been developed for fast combustion are unfortunately unable to represent properly these low temperature processes. A numerical approach addressing the influence of process conditions on the minimum AIT of different fuel/air mixtures has been developed. Several chemical models available in the literature have been tested, in order to identify the most robust ones. Based on previous works of our group, a model has been developed, which offers a fair reconciliation between experimental and calculated AIT data through a wide range of fuel compositions. This model has been validated against experimental auto-ignition delay times corresponding to high temperature in order to ensure its relevance not only for AIT aspects but also for the reactivity of gaseous fuels over the wide range of gas turbine operation conditions. In addition, the AITs of methane, of pure light alkanes, and of various blends representative of several natural gas and process-derived fuels were extensively covered. In particular, among alternative gas turbine fuels, hydrogen-rich gases are called to play an increasing part in the future so that their ignition characteristics have been addressed with particular care. Natural gas enriched with hydrogen, and different syngas fuels have been studied. AIT values have been evaluated in function of the equivalence ratio and pressure. All the results obtained have been fitted by means of a practical mathematical expression. The overall study leads to a simple correlation of AIT versus equivalence ratio/pressure.

Implication of Different Fuel Injector Configurations for Hydrogen Fuelled Micromix Combustors

2011 ◽  
Author(s):  
Bhupendra Khandelwal ◽  
Yingchun Li ◽  
Priyadarshini Murthy ◽  
Vishal Sethi ◽  
Riti Singh
Keyword(s):  
Gas Turbine ◽  
Thermal Energy ◽  
Combustion Zone ◽  
Equivalence Ratio ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Gas Turbine Combustors ◽  
The Impact

A design of a hydrogen fuelled micromix concept based combustor is proposed in this paper. The proposed micromix concept based combustor yields improved mixing, which leads to wider flammability range of the hydrogen-air flames compared to conventional kerosene and micromix concept based combustors. This improved mixing allows the combustion zone to operate at a much lower equivalence ratio than the conventional kerosene based and micromix concept based combustors considered in this study. Furthermore, when burning hydrogen the thermal energy radiated to the surroundings is lower (as the result of using lower equivalence ratio) than that of kerosene, consequently resulting in an increased liner life and lower cooling requirement. The aim of this paper is to highlight the impact of using hydrogen as a fuel in gas turbine combustors. It is perceived that this new micromix concept based combustor would also help in achieving low emissions and better performance. Possibilities for lowering NOx emissions when using hydrogen as a fuel in new designs of micromix combustor are also discussed.

scholarly journals Combustion and Oxidation Kinetics of Alternative Gas Turbines Fuels

2014 ◽  
Author(s):  
Pierre-Alexandre Glaude ◽  
Baptiste Sirjean ◽  
René Fournet ◽  
Roda Bounaceur ◽  
Matthieu Vierling ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Ignition Temperature ◽  
Alternative Fuels ◽  
Flame Temperature ◽  
Liquid Fuels ◽  
Heavy Oils ◽  
Process Gas ◽  
Auto Ignition

Heavy duty gas turbines are very flexible combustion tools that accommodate a wide variety of gaseous and liquid fuels ranging from natural gas to heavy oils, including syngas, LPG, petrochemical streams (propene, butane…), hydrogen-rich refinery by-products; naphtha; ethanol, biodiesel, aromatic gasoline and gasoil, etc. The contemporaneous quest for an increasing panel of primary energies leads manufacturers and operators to explore an ever larger segment of unconventional power generation fuels. In this moving context, there is a need to fully characterize the combustion features of these novel fuels in the specific pressure, temperature and equivalence ratio conditions of gas turbine combustors using e.g. methane as reference molecule and to cover the safety aspects of their utilization. A numerical investigation of the combustion of a representative cluster of alternative fuels has been performed in the gas phase, namely two natural gas fuels of different compositions, including some ethane, a process gas with a high content of butene, oxygenated compounds including methanol, ethanol, and DME (dimethyl ether). Sub-mechanisms have specifically been developed to include the reactions of C4 species. Major combustion parameters, such as auto-ignition temperature (AIT), ignition delay times (AID), laminar burning velocities of premixed flames, adiabatic flame temperatures, and CO and NOx emissions have then been investigated. Finally, the data have been compared with those calculated for methane flames. These simulations show that the behaviors of alternative fuels markedly differ from that of conventional ones. Especially, DME and the process gases appear to be highly reactive with significant impacts on the auto-ignition temperature and flame speed data, which justifies burner design studies within premixed combustion schemes and proper safety considerations. The behaviors of alcohols (especially methanol) display some commonalities with those of conventional fuels. In contrast, DME and process gas fuels develop substantially different flame temperature and NOx generation rates than methane. Resorting to lean premix conditions is likely to achieve lower NOx emission performances. This review of gas turbine fuels shows for instance that the use of methanol as a gas turbine fuel is possible with very limited combustor modifications.

Numerical Simulation to Characterize Homogeneity of Air-Fuel Mixture for Premixed Combustion in Gas Turbine Combustor

2012 ◽  
Author(s):  
Kamalika Chatterjee ◽  
Arkadeep Kumar ◽  
Souvick Chatterjee ◽  
Achintya Mukhopadhyay ◽  
Swarnendu Sen
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Flow Rate ◽  
Combustion Zone ◽  
Equivalence Ratio ◽  
Fuel Mixture ◽  
Premixed Combustion ◽  
Internal Diameter ◽  
Gas Turbine Combustor ◽  
Ansys Fluent

Homogeneity in mixing of air and fuel in premixed combustion for a gas turbine combustor is a critical criterion to ensure efficient combustion and less environmental hazards. The current work deals with determining this homogenous characteristic of air-fuel mixture through computational simulation to specify homogeneity for a particular premixing length and equivalence ratio required for gas turbine combustion. A 3-D geometry of combustion chamber with combustion zone of internal diameter 6 cm is constructed. A premixing tube is augmented with the combustion chamber which has one air inlet port at the bottom and 3 fuel inlet ports. Air-fuel mixture is considered to enter the combustion zone with inlet swirl. The homogeneity of the mixture is found out at the dump plane and other important planes from simulation done with ANSYS FLUENT® for the meshed geometry. The results show whether mixing of air and fuel is full or partial and the extent of partial premixing. The parameters varied in the ANSYS FLUENT®. based simulation are the premixing length i.e. port of entry of fuel, the fuel flow rate i.e. the equivalence ratio and the air flow rate.

Low-Order Modelling of the Response of Ducted Flames in Annular Geometries

2012 ◽  
Author(s):  
Owen S. Graham ◽  
Ann P. Dowling
Keyword(s):  
Heat Release ◽  
Gas Turbine ◽  
Network Model ◽  
Time Domain ◽  
Acoustic Waves ◽  
Gas Turbines ◽  
Equivalence Ratio ◽  
Fuel Injectors ◽  
Thermoacoustic Instabilities ◽  
Lean Premixed

The adoption of lean premixed prevaporised combustion systems can reduce NOx emissions from gas turbines, but unfortunately also increases their susceptibility to thermoacoustic instabilities. Initially, acoustic waves can produce heat release fluctuations by a variety of mechanisms, often by perturbing the equivalence ratio. If correctly phased, heat release fluctuations can subsequently generate more acoustic waves, which at high amplitude can result in significant structural damage to the combustor. The prediction of this phenomenon is of great industrial interest. In previous work, we have coupled a physics based, kinematic model of the flame with a network model to provide the planar acoustic response necessary to close the feedback loop and predict the onset and amplitude of thermoacoustic instabilities in a lab-scale, axisymmetric single burner combustor. The advantage of a time domain approach is that the modal interaction, the influence of harmonics, and flame saturation can be investigated. This paper extends this approach to more realistic, annular geometries, where both planar and circumferential modes must be considered. In lean premixed prevaporised combustors, fluctuations in equivalence ratio have been shown to be a dominant cause of unsteady combustion. These can occur, for example, due to velocity perturbations in the premix ducts, which can lead to equivalence ratio fluctuations at the fuel injectors, which are subsequently convected downstream to the flame surfaces. Here, they can perturb the heat release by locally altering the flame speed, enthalpy of combustion, and, indirectly, the flame surface area. In many gas turbine designs, particularly aeroengines, the geometries are composed of a ring of premix ducts linking a plenum and an annular combustor. The most unstable modes are often circumferential modes. The network model is used to characterise the flow response of the geometry to heat fluctuations at an appropriate location, such as the fuel injectors. The heat release at each flame holder is determined in the time domain using the kinematic flame model derived, as a function of the flow perturbations in the premix duct. This approach is demonstrated for an annular ring of burners on a in a simple geometry. The approach is then extended to an industrial type gas turbine combustor, and used to predict the limit cycle amplitudes.

scholarly journals Combustion of Liquid Fuels in the Well Stirred Reactor

1996 ◽  
Author(s):  
J. Zelina ◽  
J. W. Blust ◽  
D. R. Ballal
Keyword(s):  
Gas Turbine ◽  
Equivalence Ratio ◽  
Equilibrium Concentration ◽  
Liquid Fuels ◽  
Jet Fuels ◽  
Stirred Reactor ◽  
Primary Zone ◽  
Appreciable Increase ◽  
Performance And Emissions ◽  
Industrial Gas Turbine

The design and development of low-emissions, lean premixed aero, or industrial gas turbine combustors is very challenging because of a need to satisfy conflicting requirements of combustion performance and emissions. A toroidal well stirred reactor (WSR) provides a laboratory idealization of an efficient, highly compact primary zone of a gas turbine combustor and facilitates the study of combustion and emissions. The WSR was used to study emissions from heptane and JP-7 fuels. It was found that the measured concentrations of CO2 and O2 agreed closely with the predictions of the equilibrium concentration. CO emissions for ϕ > 0.77 followed the equilibrium predictions reasonably well. But for ϕ < 0.77, the measured CO values were much higher than the equilibrium values. NOx emission increased as equivalence ratio approaches unity. Tests conducted at a constant equivalence ratio and residence time demonstrated an appreciable increase in CO and a modest increase in NOx with an increase in the (C/H) mole ratio. Therefore, a combustor designer should be concerned that jet fuels with lower hydrogen content will produce increased emissions of gaseous pollutants.

Nox emission control in gas turbines for combined cycle gas turbine plant

1997 ◽  
Vol 211 (1) ◽  
pp. 43-52 ◽  
Author(s):  
M J Moore
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Catalytic Reduction ◽  
Water Injection ◽  
Emission Control ◽  
Combined Cycle ◽  
Liquid Fuels ◽  
Gas Combustion ◽  
Natural Gas Combustion

The increase, in recent years, in the size and efficiency of gas turbines burning natural gas in combined cycle has occurred against a background of tightening environmental legislation on the emission of nitrogen oxides. The higher turbine entry temperatures required for efficiency improvement tend to increase NOx production. First-generation emission control systems involved water injection and catalytic reduction and were relatively expensive to operate. Dry low-NOx combustion systems have therefore been developed but demand more primary air for combustion. This gives added incentive to the reduction of air requirements for cooling the combustor and turbine blading. This paper reviews the various approaches adopted by the main gas turbine manufacturers which are achieving very low levels of NOx emission from natural gas combustion. Further developments, however, are necessary for liquid fuels.

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