Predicting Flameholding for Hydrogen and Natural Gas Flames at Gas Turbine Premixer Conditions

2015 ◽  
Author(s):  
Elliot Sullivan-Lewis ◽  
Vincent McDonell
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Free Stream ◽  
Experimental Studies ◽  
Temperature Variations ◽  
Auto Ignition ◽  
Chamber Temperature ◽  
Transient Events ◽  
Significant Effort

Lean premixed gas turbines are one of the most common methods for stationary power generation. By creating a homogeneous mixture of fuel and air upstream of the combustion chamber, temperature variations are reduced within the combustor, which reduces emissions of nitrogen oxides. However, by premixing fuel and air, a potentially flammable mixture is established in a part of the engine not designed to contain a flame. If the flame propagates upstream from the combustor (flashback), significant engine damage can result. While significant effort has been put into developing flashback resistant combustors, these combustors are only capable of preventing flashback during steady operation of the engine. Transient events (e.g. auto ignition within the premixer, pressure spikes during ignition) can trigger flashback that cannot be prevented with even the best combustor design. In these cases, preventing engine damage requires designing premixers that will not allow a flame to be sustained. Experimental studies were conducted to determine under what conditions premixed flames of hydrogen and natural gas can be anchored in a simulated gas turbine premixer. Tests have been conducted at pressures up to 9 atm, temperatures up to 750 K, and free stream velocities between 20 and 100 m/s. Flames were anchored in the wakes of features typical of premixer passageways, including cylinders, steps and airfoils. The results of this study have been used to develop tools that predict when a flame remains anchored to a particular feature.

Predicting Flameholding for Hydrogen and Natural Gas Flames at Gas Turbine Premixer Conditions

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Elliot Sullivan-Lewis ◽  
Vincent McDonell
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Experimental Studies ◽  
Temperature Variations ◽  
Auto Ignition ◽  
Chamber Temperature ◽  
Transient Events ◽  
Significant Effort

Lean-premixed gas turbines are now common devices for low emissions stationary power generation. By creating a homogeneous mixture of fuel and air upstream of the combustion chamber, temperature variations are reduced within the combustor, which reduces emissions of nitrogen oxides. However, by premixing fuel and air, a potentially flammable mixture is established in a part of the engine not designed to contain a flame. If the flame propagates upstream from the combustor (flashback), significant engine damage can result. While significant effort has been put into developing flashback resistant combustors, these combustors are only capable of preventing flashback during steady operation of the engine. Transient events (e.g., auto-ignition within the premixer and pressure spikes during ignition) can trigger flashback that cannot be prevented with even the best combustor design. In these cases, preventing engine damage requires designing premixers that will not allow a flame to be sustained. Experimental studies were conducted to determine under what conditions premixed flames of hydrogen and natural gas can be anchored in a simulated gas turbine premixer. Tests have been conducted at pressures up to 9 atm, temperatures up to 750 K, and freestream velocities between 20 and 100 m/s. Flames were anchored in the wakes of features typical of premixer passageways, including cylinders, steps, and airfoils. The results of this study have been used to develop an engineering tool that predicts under what conditions a flame will anchor, and can be used for development of flame anchoring resistant gas turbine premixers.

DME as a Potential Alternative Fuel for Gas Turbines: A Numerical Approach to Combustion and Oxidation Kinetics

2011 ◽  
Author(s):  
Pierre A. Glaude ◽  
Rene´ Fournet ◽  
Roda Bounaceur ◽  
Michel Molie`re
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Heat Input ◽  
Ignition Delay ◽  
Gas Turbines ◽  
Ignition Temperature ◽  
Alternative Fuels ◽  
Ignition Delay Times ◽  
Auto Ignition ◽  
Delay Times

Many investigations are currently carried out in order to reduce CO2 emissions in power generation. Among alternative fuels to natural gas and gasoil in gas turbine applications, dimethyl ether (DME; formula: CH3-O-CH3) represents a possible candidate in the next years. This chemical compound can be produced from natural gas or coal/biomass gasification. DME is a good substitute for gasoil in diesel engine. Its Lower Heating Value is close to that of ethanol but it offers some advantages compared to alcohols in terms of stability and miscibility with hydrocarbons. While numerous studies have been devoted to the combustion of DME in diesel engines, results are scarce as far as boilers and gas turbines are concerned. Some safety aspects must be addressed before feeding a combustion device with DME because of its low flash point (as low as −83°C), its low auto-ignition temperature and large domain of explosivity in air. As far as emissions are concerned, the existing literature shows that in non premixed flames, DME produces less NOx than ethane taken as parent molecular structure, based on an equivalent heat input to the burner. During a field test performed in a gas turbine, a change-over from methane to DME led to a higher fuel nozzle temperature but to a lower exhaust gas temperature. NOx emissions decreased over the whole range of heat input studied but a dramatic increase of CO emissions was observed. This work aims to study the combustion behavior of DME in gas turbine conditions with the help of a detailed kinetic modeling. Several important combustion parameters, such as the auto-ignition temperature (AIT), ignition delay times, laminar burning velocities of premixed flames, adiabatic flame temperatures, and the formation of pollutants like CO and NOx have been investigated. These data have been compared with those calculated in the case of methane combustion. The model was built starting from a well validated mechanism taken from the literature and already used to predict the behavior of other alternative fuels. In flame conditions, DME forms formaldehyde as the major intermediate, the consumption of which leads in few steps to CO then CO2. The lower amount of CH2 radicals in comparison with methane flames seems to decrease the possibility of prompt-NO formation. This paper covers the low temperature oxidation chemistry of DME which is necessary to properly predict ignition temperatures and auto-ignition delay times that are important parameters for safety.

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.

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.

Operability Limits of Tubular Injectors With Vortex Generators for a Hydrogen Fuelled Recuperated 100kW Class Gas Turbine

2016 ◽  
Author(s):  
Stefan Bauer ◽  
Balbina Hampel ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Bulk Flow ◽  
Vortex Generators ◽  
Test Rig ◽  
Temperature Range ◽  
Auto Ignition ◽  
Wide Range

Vortex generators are known to be effective in augmenting the mixing of fuel jets with air. The configuration investgated in this study is a tubular air passage with fuel injection from one single orifice placed in the side wall. In the range of typical gas turbine combustor inlet temperatures, the performance vortex generator premixers (VGPs) have already been investigated for natural gas as well as for blends of natural gas and hydrogen. However, for highly reactive fuels, the application of VGPs in recuperated gas turbines is particularly challenging because the high combustor inlet temperature leads to potential risk with regard to premature self-ignition and flame flashback. As the current knowledge does not cover the temperature range far above the self-ignition temperature, an experimental investigation of the operational limits of VGPs is currently being conducted at the Thermodynamics Institute of the Technical University of Munich, which is particularly focused on reactive fuels and the thermodynamic conditions present in recuperated gas turbines with pressure ratios of 4–5. For the study presented in the paper, an atmospheric combustion VGP test rig has been designed, which facilitates investigations in a wide range of operating conditions in order to comply with the situation in recuperated micro gas turbines, namely global equivalence ratios between 0.2 and 0.7, air preheating temperatures between 288K and 1100K, and air bulk flow rates between 6–16 g/s. Both the entire mixing zone in the VGP and the primary combustion zone of the test rig are optically accessible. High speed OH* chemiluminescence imaging is used for the detection of the flashback and blow-off limits of the investigated VGPs. Flashback and blow-off limits of hydrogen in a wide temperature range covering the auto-ignition regime are presented, addressing the influences of equivalence ratio, air preheating temperature and momentum ratio between air and hydrogen on the operational limits in terms of bulk flow velocity. It is shown that flashback and blow-off limits are increasingly influenced by auto-ignition in the ultra-high temperature regime.

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

2015 ◽  
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 ◽  
Large Temperature ◽  
Individual Species ◽  
Gaseous Fuels ◽  
Auto Ignition ◽  
Wide Range

Gas turbines burn a large variety of gaseous fuels under elevated pressure and temperature conditions. During transient operations like maintenance, start-ups or fuel transfers, variable gas/air mixtures are involved in the gas piping system. Therefore, in order to predict the risk of auto-ignition events and ensure a safe and optimal 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. AIT data correspond to temperature ranges in which fuels display an incipient reactivity, with time scales 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, especially those involving peroxy radicals, 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. In this context, a numerical approach addressing the influence of process conditions on the minimum auto-ignition temperature of different fuel/air mixtures has been developed. For that purpose, 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 covering a large temperature range 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 (AID) 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 CO/H2 syngas fuels originating from a blast furnace (BFG) have namely been studied. Globally, the individual species covered are: H2, CO, CO2, N2, CH4, C2H6, C3H8, C4H10, and C5H12. 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 that may be of fruitful use for the engineering community.

scholarly journals Natural Gas

2011 ◽  
Vol 133 (04) ◽  
pp. 52-52
Author(s):  
Rainer Kurz
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Oil And Gas ◽  
Electrical Power ◽  
Offshore Platforms ◽  
Electric Motors ◽  
Turbine Generator ◽  
Associated Gas ◽  
Generator Sets

This article discusses the importance of gas turbines, centrifugal compressors and pumps, and other turbomachines in processes that bring natural gas to the end users. To be useful, the natural gas coming from a large number of small wells has to be gathered. This process requires compression of the gas in several stages, before it is processed in a gas plant, where contaminants and heavier hydrocarbons are stripped from the gas. From the gas plant, the gas is recompressed and fed into a pipeline. In all these compression processes, centrifugal gas compressors driven by industrial gas turbines or electric motors play an important role. Turbomachines are used in a variety of applications for the production of oil and associated gas. For example, gas turbine generator sets often provide electrical power for offshore platforms or remote oil and gas fields. Offshore platforms have a large electrical demand, often requiring multiple large gas turbine generator sets. Similarly, centrifugal gas compressors, driven by gas turbines or by electric motors are the benchmark products to pump gas through pipelines, anywhere in the world.

Ignition Studies of C1-C7 Natural Gas Blends At Gas-Turbine Relevant Conditions

2021 ◽  
Author(s):  
Amrit Sahu ◽  
A.A.E.S Mohamed ◽  
Snehashish Panigrahy ◽  
Gilles Bourque ◽  
Henry Curran
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Mixtures ◽  
Rapid Compression Machine ◽  
Temperature Range ◽  
Auto Ignition ◽  
Wide Range ◽  
Model Predictions ◽  
Detailed Kinetic Model ◽  
Sensitization Effect

Abstract New ignition delay time measurements (IDT) of natural gas mixtures enriched with small amounts of n-hexane and n-heptane were performed in a rapid compression machine to interpret the sensitization effect of heavier hydrocarbons on auto-ignition at gas-turbine relevant conditions. The experimental data of natural gas mixtures containing alkanes from methane to n-heptane were carried out over a wide range of temperatures (840-1050 K), pressures (20-30 bar), and equivalence ratios (f = 0.5 and 1.5). The experiments were complemented with numerical simulations using a detailed kinetic model developed to investigate the effect of n-hexane and n-heptane additions. Model predictions show that the addition of even small amounts (1-2%) of n-hexane and n-heptane can lead to an increase in reactivity by ~40-60 ms at a temperature of 700 K. The IDTs of these mixtures decrease rapidly with an increase in the concentration of up to 7.5% but becomes almost independent of the C6/C7 concentration >10%. This sensitization effect of C6 and C7 is also found to be more pronounced in the temperature range 700-900 K compared to that at higher temperatures (>900 K). The reason is attributed to the dependence of IDT primarily on H2O2(+M)??H+?H (+M) at higher temperatures while the fuel-dependent reactions such as H-atom abstraction, RO2 dissociation, or Q OOH+O2 reactions are less important compared to the temperature range 700-900 K, where they are very important.

Ignition Studies of C1–C7 Natural Gas Blends at Gas-Turbine Relevant Conditions

2020 ◽  
Author(s):  
Amrit Bikram Sahu ◽  
A. Abd El-Sabor Mohamed ◽  
Snehasish Panigrahy ◽  
Gilles Bourque ◽  
Henry Curran
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Gas Mixtures ◽  
Auto Ignition ◽  
Wide Range ◽  
Detailed Kinetic Model ◽  
Sensitization Effect

Abstract New ignition delay time measurements of natural gas mixtures enriched with small amounts of n-hexane and n-heptane were performed in a rapid compression machine to interpret the sensitization effect of heavier hydrocarbons on auto-ignition at gas-turbine relevant conditions. The experimental data of natural gas mixtures containing alkanes from methane to n-heptane were carried out over a wide range of temperatures (840–1050 K), pressures (20–30 bar), and equivalence ratios (φ = 0.5 and 1.5). The experiments were complimented with numerical simulations using a detailed kinetic model developed to investigate the effect of n-hexane and n-heptane additions. Model predictions show that the addition of even small amounts (1–2%) of n-hexane and n-heptane can lead to increase in reactivity by ∼40–60 ms at compressed temperature (TC) = 700 K. The ignition delay time (IDT) of these mixtures decrease rapidly with an increase in concentration of up to 7.5% but becomes almost independent of the C6/C7 concentration beyond 10%. This sensitization effect of C6 and C7 is also found to be more pronounced in the temperature range 700–900 K compared to that at higher temperatures (> 900 K). The reason is attributed to the dependence of IDT primarily on H2O2(+M) ↔ 2ȮH(+M) at higher temperatures while the fuel dependent reactions such as H-atom abstraction, RȮ2 dissociation or Q.OOH + O2 reactions are less important compared to 700–900 K, where they are very important.

Optimizing Maintenance for Multi-Unit Industrial Gas Turbine Installations

2010 ◽  
Author(s):  
Markus Bohlin ◽  
Mathias Wa¨rja
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Preventive Maintenance ◽  
Gas Turbines ◽  
Economic Effects ◽  
Negative Effects ◽  
Component Level ◽  
Maintenance Schedule ◽  
Natural Gas Pipelines ◽  
Oil Platforms

High levels of availability and reliability are essential in many industries where production is subject to high costs due to downtime. Examples where gas turbines are used include the mechanical drive in natural gas pipelines and power generation on oil platforms, where it is common to use redundant gas turbines to mitigate the effects of service outage. In this paper, component-level maintenance of parallel multi-unit systems is considered, allowing production at a reduced level when some of the units are not operational. Units are themselves assumed to be composed out of components in a serial configuration; maintenance of one component implies shutdown of the unit. Parallel installations allow maintenance to be performed on one or a few gas turbines without taking down the entire installation. This allows maintenance to be optimized even further than in a serial system. However, the maintenance optimization process is made more complicated, since there now exist both positive and negative grouping effects. The positive grouping effects come from shared setup activities and costs, and the negative effects come from resource limitations, in this case the limited number of gas turbines which can be maintained at the same time. In the approach presented in this paper, each component has its individual preventive maintenance schedule, which is updated at inspections, changes in production and when indicated using remote condition monitoring. A minimal repair model for noncritical routine inspections and service tasks is assumed, which does not affect component state. In addition, previously developed procedures for estimating and measuring residual component lifetime for individual components during operation are used. The procedures are based on a Retirement For Cause (RFC) approach where components are not replaced until a potential failure has been detected. To maximize revenues for an operator, the available information is evaluated using software where scenario analysis and optimization is performed. To show the possible economic effects, gas turbine operation data is used together with maintenance and operator requirements as input for optimization of a production line consisting of a natural-gas compressor station having three SGT-600 gas turbines. Savings can be substantial compared to a traditional preventive maintenance plan.

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