Effect of Different Fuels on Combustion Instabilities in an Annular Combustor

2020 ◽  
Author(s):  
Preethi Rajendram Soundararajan ◽  
Guillaume Vignat ◽  
Daniel Durox ◽  
Antoine Renaud ◽  
Sébastien Candel
Keyword(s):  
Fuel Injection ◽  
Thermal Power ◽  
Time Lag ◽  
Liquid Fuels ◽  
Jet Engines ◽  
Combustion Instabilities ◽  
Annular Combustor ◽  
Coupling Mode ◽  
Instability Map ◽  
The Difference

Abstract Combustion instabilities in annular combustors of jet engines is a recurring issue. In the present study, the characteristics of instabilities for different fuels are investigated by combining the instability maps obtained in an annular combustor equipped with multiple swirling spray injectors (MICCA-Spray) and flame describing functions (FDFs) from a single sector configuration (SICCA-Spray). Two types of liquid fuels are injected as hollow cone sprays: heptane, which is fairly volatile, and dodecane, which is less volatile. Experiments are also conducted with gaseous propane, perfectly premixed with air, which serves as a reference. An instability map is systematically drawn by varying the global equivalence ratio and thermal power. The data indicate that the amplitude and frequency of instabilities depend, for the same operating point, on the fuel injection conditions (premixed or spray) and fuel type. Overall trends show that premixed propane is unstable in a broad operating domain. Injection of liquid fuels induces changes in time lag that modify the unstable regions. For heptane the instability map is closer to the propane reference map whereas dodecane exhibits wider stable regions. Variations can also be observed in the behavior of spin ratio that characterizes the azimuthal structure of the coupling mode. An attempt is made to understand these features by examining the FDF, which gives the ratio of relative fluctuations in heat release rate to the relative fluctuations in velocity. The FDFs measured in a single sector configuration gives access to gain and phase information that can be used to determine unstable bands. It is found that based on whether the MICCA-Spray instability frequency is within these bands, the instability amplitude can be high or low. This indicates that the difference in instabilities between the three fuels can be linked to the variations in FDFs.

Effect of Different Fuels On Combustion Instabilities in an Annular Combustors

2021 ◽  
Author(s):  
Preethi Rajendram Soundararajan ◽  
Vignat Guillaume ◽  
Daniel Durox ◽  
Antoine Renaud ◽  
Sebastien Candel
Keyword(s):  
Fuel Injection ◽  
Thermal Power ◽  
Time Lag ◽  
Liquid Fuels ◽  
Jet Engines ◽  
Combustion Instabilities ◽  
Describing Functions ◽  
Annular Combustor ◽  
Instability Map ◽  
Reference Map

Abstract Combustion instability in annular combustors of jet engines is a recurring issue. In the present study, the characteristics of instabilities for different fuels are investigated by combining the instability maps obtained in a laboratory-scale annular combustor equipped with multiple swirling spray injectors (MICCA-Spray) and flame describing functions (FDFs) from a single sector configuration (SICCA-Spray). Two types of liquid fuels are injected as hollow cone sprays: heptane, which is fairly volatile, and dodecane, which is less volatile. Experiments are also conducted with gaseous propane, premixed with air, which serves as a reference. An instability map is systematically drawn by varying the global equivalence ratio and thermal power. The data indicate that the amplitude and frequency of instabilities depend, for the same operating point, on the fuel injection conditions and fuel type. Overall trends show that premixed propane is unstable in a broad operating domain. Injection of liquid fuels induce changes in flame time lag that modify the unstable regions. For heptane, the instability map is closer to the propane reference map, whereas dodecane exhibits wider stable regions. An attempt is made to understand these features by examining the FDF, which gives the ratio of relative fluctuations in heat release rate to the relative fluctuations in velocity. The FDFs measured in a single sector configuration give access to gain and phase information that can be used to determine unstable bands and calculate an instability index guiding the interpretation of the differences in instabilities of the three fuels.

Liquid Fuelled Low NOx Radial Swirlers With Central Pilot Combustion

2007 ◽  
Author(s):  
Gordon E. Andrews ◽  
M. N. Kim ◽  
Mike C. Mkpadi ◽  
Sheriff A. Akande
Keyword(s):  
Natural Gas ◽  
Liquid Fuel ◽  
Fuel Injection ◽  
Liquid Fuels ◽  
Lean Combustion ◽  
Auto Ignition ◽  
Primary Zone ◽  
Low Nox Combustion ◽  
The Difference ◽  
Injection Location

Radial swirlers have proved effective in achieving low NOx using natural gas and this work investigates their use with kerosene with and without a central NG pilot. Two kerosene fuel injection locations were compared: at the inlet to the vane passages on the centreline with co-flow injection and 20mm downstream of the 76mm diameter swirler exit through the wall of a 76mm diameter 40mm long discharge duct. Flash back and auto ignition problems cannot occur with the downstream wall fuel injection location. All configurations were also tested with natural gas so that the difference in emissions due to the change from gas to liquid fuel could be established. The results show that ultra low NOx emissions can be achieved for kerosene with vane passage injection and that the use of a central pilot increases the NOx but improves the flame stability and power turndown. However, on liquid fuels the pilot to main flame propagation was not as good as when natural gas was used as the main fuel. Liquid fuel injection at the radial swirler wall outlet was effective but had slightly higher NOx for lean mixtures and worse HC and CO emissions. However, for richer primary zone mixtures the NOx was lower than for vane passage injection and this indicated that rich/lean combustion was occurring, without the uniform mixing and low NOx combustion that occurred with natural gas injection at this location.

MECHANISM AND CHARACTERISTICS OF GEL FUEL IGNITION

2020 ◽  
Author(s):  
O. S. Gaydukova ◽  
◽  
D. O. Glushkov ◽  
A. G. Nigay ◽  
A. G. Kosintsev ◽  
...  
Keyword(s):  
Thermal Power ◽  
Aerospace Industry ◽  
Theory Development ◽  
Liquid Fuels ◽  
Ignition Characteristics ◽  
Deformable Materials ◽  
Combustion Processes ◽  
Thermal Power Engineering ◽  
Storage Processes ◽  
Emulsions And Suspensions

Recently, prospective direction of the combustion theory development is the preparation of fuel compositions and study of the composite fuels ignition characteristics, for example, in the form of emulsions and suspensions. Such fuels and their combustion processes are characterized by higher environmental, energy, economic, and operational properties. Of great interest is the use of gel fuels prepared by thickening emulsions and suspensions to the state of elastically deformable materials for the aerospace industry and thermal power engineering. Gel fuels have advantages over widespread liquid fuels in environmental and fire safety aspects of storage processes, transportation, and combustion.

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.

Fuel Atomization in Small Jet Engines

2002 ◽  
Author(s):  
Yeshayahou Levy ◽  
Semion Lipkin ◽  
Valery Nadvany ◽  
Valery Sherbaum
Keyword(s):  
Fuel Injection ◽  
High Energy ◽  
Operating Conditions ◽  
Fuel Vapor ◽  
Ignition Process ◽  
Jet Engines ◽  
Alternative Design ◽  
Fuel Supply ◽  
Small Engines ◽  
Supply Systems

Small and inexpensive jet engines are usually equipped with vaporizing fuel supply systems. This is in order to deliver low fuel flow-rates from relatively low-pressure fuel supply systems and the need for simple configuration. The difficulties associated with small engines are mainly during ignition or at high altitude re-lights, when the combustor is cold, air supply is poor, and fuel demand and pressure are low. Such conditions lead to poor atomization within the vaporizer resulting in very large droplets at its exit tip or even to a pool of liquid fuel within the combustor. Thus, there is no fuel vapor for ignition. Ignition is very difficult or even impossible under such conditions. Therefore, small engines are commonly equipped with dual fuel supply systems, either in the form of gaseous fuel for the ignition stage or with an additional higher-pressure supply line to the dedicated fuel nozzles for the purpose of ignition. Additional solutions involve the use of a large glow plug or high-energy pyrotechnic cartridges in the kilo-Joule range, to heat the combustor casing prior to ignition. The present work is concerned with the development of alternative and novel atomization systems, which would improve atomization at low pressures and consequently facilitate the ignition process, thus minimizing the need for supporting systems. The work refers to an alternative design for an existing vaporizer system of a small jet engine with 400 Nt of thrust. It focuses on an alternative design for the fuel injection within the vaporizer housing while maintaining all external dimensions and operating conditions unchanged. Three types of fuel nozzles were investigated: • a special impact atomizer, • a miniature pressure swirl atomizer, • a doublet atomizer involving two swirling nozzles (preliminary study only). Droplet size distribution under various nozzle pressure drops and air velocities were measured with Phase Doppler Particle Anemometry (PDPA) and global spray characteristics were obtained by photography. All modified atomization systems demonstrated improved performance and better atomization than the existing system. Initially, water was used as a liquid. At a later stage, the modified impact atomizer was tested and successful spark ignition was demonstrated.

Ignition Dynamics in an Annular Combustor With Gyratory Flow Motion

2018 ◽  
Author(s):  
Chenran Ye ◽  
Gaofeng Wang ◽  
Yuanqi Fang ◽  
Chengbiao Ma ◽  
Liang Zhong ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Velocity Component ◽  
Thermal Power ◽  
Propagation Speed ◽  
Circumferential Velocity ◽  
Bulk Velocity ◽  
Ignition Process ◽  
Flow Motion ◽  
Annular Combustor ◽  
Flame Propagation Speed

In concepts of integrated design of combustor and turbine, an annular combustor model is developed and featured with multiple oblique-injecting swirling injectors to introduce gyratory flow motion in the combustion chamber. The ignition process is experimentally investigated to study the effects of introducing circumferential velocity component Uc to the light-round sequence. Experiments are carried out with premixed propane/air mixture in ambient conditions. The light-round sequence is recorded by a high-speed camera, which provides detailed flame azimuthal positions during the sequence and gives access to the light-round time τ and the circumferential flame propagation speed Sc. The results have also been compared with that obtained from a straight-injecting annular combustor. The effects of bulk velocity Ub, thermal power P and equivalence ratio Φ are also explored. Due to the gyratory flow motion induced by oblique injection, the flame fronts only propagate along the direction of circumferential flow. Both of the circumferential flame propagation speed increase with increasing bulk velocity in two injection types. It seems mainly to depend on bulk velocity, regardless of Φ, in oblique-injecting combustor when compared with the straight one. It indicates that the circumferential velocity component would play a dominant role in light-round sequence when it is sufficient higher than the displacement flame speed.

scholarly journals Application of a three-step approach for prediction of combustion instabilities in industrial gas turbine burners

2017 ◽  
Vol 1 ◽  
pp. JCW78T
Author(s):  
Dmytro Iurashev ◽  
Giovanni Campa ◽  
Vyacheslav V. Anisimov ◽  
Ezio Cosatto ◽  
Luca Rofi ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Time Lag ◽  
High Amplitude ◽  
Combustion Regime ◽  
Industrial Test ◽  
Distributed Model ◽  
Combustion Instabilities ◽  
Acoustic Oscillations ◽  
Analytical Time

Abstract Recently, because of environmental regulations, gas turbine manufacturers are restricted to produce machines that work in the lean combustion regime. Gas turbines operating in this regime are prone to combustion-driven acoustic oscillations referred as combustion instabilities. These oscillations could have such high amplitude that they can damage gas turbine hardware. In this study, the three-step approach for combustion instabilities prediction is applied to an industrial test rig. As the first step, the flame transfer function (FTF) of the burner is obtained performing unsteady computational fluid dynamics (CFD) simulations. As the second step, the obtained FTF is approximated with an analytical time-lag-distributed model. The third step is the time-domain simulations using a network model. The obtained results are compared against the experimental data. The obtained results show a good agreement with the experimental ones and the developed approach is able to predict thermoacoustic instabilities in gas turbines combustion chambers.

scholarly journals Replacement depreciation and price regulation

2006 ◽  
Vol 17 (3) ◽  
pp. 10-20
Author(s):  
IJ Lambrechts
Keyword(s):  
The United States ◽  
Natural Monopoly ◽  
Price Regulation ◽  
Liquid Fuels ◽  
Economic Regulation ◽  
Tax Rates ◽  
Historical Cost ◽  
Investment Rates ◽  
The Difference ◽  
The Moment

Price regulation occurs quite commonly amongst natural monopolies which frequently include public utilities. In South Africa and in certain countries in Africa, there has recently been a revival of price regulation in certain industries and enterprises, where competition is limited or non-existent. Price regulation can be applied in a multitude of ways. Because of the importance of the price levels (historical and replacement) in the price setting exercise, the focus in this paper will be on the issue of depreciation to arrive at the final prices. The electricity utility industry was historically viewed as a highly mature and heavily regulated natural monopoly. In many parts of the world, electricity utilities have already been deregulated to a large extent and in the United States the process was preceded by a process of unbundling or ringfencing of the main divisions, i.e. generation and distribution. Even the network component of transmission, traditionally seen as natural monopolies, was deregulated to a large extent. The deregulation process, whether fully or partially, emphasised the requirement for a detailed explanation for a specific price level. The need for acceptable and transparent selling prices has, therefore, not disappeared. Regulatory pricing is consequently a vital component of pricing at this stage and in the restructured industry it will continue to play an important role because of a limited number of participants. In other sectors of the South African energy industry too, the deregulation process has either not started or has not been completed. Price regulation is presently and will in future be applicable to the liquid fuels industry, which includes the pipeline of Petronet as well as gas pipelines. Other industries which are being price regulated at the moment include water, medicine, telecommunication (fixed lines) and postal rates. Although the economic regulation for these industries may differ substantially, the principles applying to depreciation calculations would be similar. Replacement depreciation produces lower profit figures during periods of inflation. Quoted companies often oppose this system because of a lack of taxation recognition on income and the adverse effect on earnings per share. This paper covers the calculation of depreciation by price regulators where assets are not diversified (single assets). Shorter depreciation lifetimes based on historical cost result in an automatic provision for replacement depreciation. The extent of the provision would be a function of the difference between the actual and selected lifetimes, income tax rates, re-investment rates and the extent of the financial gearing ratio. Provision for replacement depreciation may be reduced significantly, if not reduced completely, by reducing depreciation lifetimes.

scholarly journals Corrosion resistance of metalized layers on steel parts in ventilation mill

10.30544/340 ◽  
2018 ◽  
Vol 24 (2) ◽  
pp. 123-132
Author(s):  
Bore V. Jegdic ◽  
Bojana M. Radojković ◽  
Biljana M. Bobić ◽  
Marija M. Krmar ◽  
Slavica Ristić
Keyword(s):  
Corrosion Rate ◽  
Base Metal ◽  
Galvanic Corrosion ◽  
Thermal Power ◽  
Electrochemical Techniques ◽  
General Corrosion ◽  
Hvof Process ◽  
The Difference ◽  
Local Dissolution ◽  
Oxygen Fuel

Corrosion behavior of metalized layers, obtained by Plasma Transferred Arc (PTA) process and by High-Velocity Oxygen Fuel (HVOF) process with the purpose to improve the wear resistance of vital parts of ventilation mill in a thermal power plant, has been tested. The test is performed using three electrochemical techniques, in a solution containing chloride and sulfate ions. It is shown that the steel surface (base metal) dissolves uniformly, without pitting or other forms of local dissolution. Morphology of metalized layers surface indicates that dissolution is non-uniform, but it still can be considered as general corrosion. The corrosion rate of base metal and metalized layer obtained by PTA process is rather low, while the corrosion rate of the metalized layer obtained by HVOF process is much higher. Also, the difference in corrosion potentials between the base metal and the HVOF layer is pretty high but slightly less than maximum allowed difference (prescribed by the standard), to avoid excessive galvanic corrosion. The values of corrosion rate obtained by different electrochemical techniques are in excellent agreement.

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