Natural gas ignition delay times behind reflected shock waves: Application to modelling and safety

Ignition delay times have been measured behind reflected shock waves in ethane-oxygen-argon mixtures at temperatures between 1150 and 1500 K and pre-ignition pressures between 10 and 14 atm. Delay times have been measured both by pressure rise and OH absorption at 307 nm. Kinetic modelling of the ignition delays has been made using the GRIMech 3.0 mechanism which with addition of several reactions involving HO

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Ignition delay times of conventional and alternative fuels behind reflected shock waves

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2014.05.034 ◽

2015 ◽

Vol 35 (1) ◽

pp. 241-248 ◽

Cited By ~ 36

Author(s):

Yangye Zhu ◽

Sijie Li ◽

David F. Davidson ◽

Ronald K. Hanson

Keyword(s):

Shock Waves ◽

Ignition Delay ◽

Alternative Fuels ◽

Reflected Shock ◽

Ignition Delay Times ◽

Delay Times

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Ignition delay times of methyl oleate and methyl linoleate behind reflected shock waves

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2012.05.084 ◽

2013 ◽

Vol 34 (1) ◽

pp. 419-425 ◽

Cited By ~ 36

Author(s):

M.F. Campbell ◽

D.F. Davidson ◽

R.K. Hanson ◽

C.K. Westbrook

Keyword(s):

Methyl Oleate ◽

Methyl Linoleate ◽

Shock Waves ◽

Ignition Delay ◽

Reflected Shock ◽

Ignition Delay Times ◽

Delay Times

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

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Wind Turbine Technology ◽

10.1115/gt2011-46238 ◽

2011 ◽

Cited By ~ 3

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.

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Alternative Fuels Based on Biomass: An Experimental and Modeling Study of Ethanol Cofiring to Natural Gas

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4029625 ◽

2015 ◽

Vol 137 (9) ◽

Cited By ~ 5

Author(s):

Marina Braun-Unkhoff ◽

Jens Dembowski ◽

Jürgen Herzler ◽

Jürgen Karle ◽

Clemens Naumann ◽

...

Keyword(s):

Power Generation ◽

Natural Gas ◽

Gas Turbine ◽

Kinetic Modeling ◽

Ignition Delay ◽

Chemical Kinetic ◽

Parameter Range ◽

Ignition Delay Times ◽

Combustion Properties ◽

Delay Times

In response to the limited resources of fossil fuels as well as to their combustion contributing to global warming through CO2 emissions, it is currently discussed to which extent future energy demands can be satisfied by using biomass and biogenic by-products, e.g., by cofiring. However, new concepts and new unconventional fuels for electric power generation require a re-investigation of at least the gas turbine burner if not the gas turbine itself to ensure a safe operation and a maximum range in tolerating fuel variations and combustion conditions. Within this context, alcohols, in particular, ethanol, are of high interest as alternative fuel. Presently, the use of ethanol for power generation—in decentralized (microgas turbines) or centralized gas turbine units, neat, or cofired with gaseous fuels like natural gas (NG) and biogas—is discussed. Chemical kinetic modeling has become an important tool for interpreting and understanding the combustion phenomena observed, for example, focusing on heat release (burning velocities) and reactivity (ignition delay times). Furthermore, a chemical kinetic reaction model validated by relevant experiments performed within a large parameter range allows a more sophisticated computer assisted design of burners as well as of combustion chambers, when used within computational fluid dynamics (CFD) codes. Therefore, a detailed experimental and modeling study of ethanol cofiring to NG will be presented focusing on two major combustion properties within a relevant parameter range: (i) ignition delay times measured in a shock tube device, at ambient (p = 1 bar) and elevated (p = 4 bar) pressures, for lean (φ = 0.5) and stoichiometric fuel–air mixtures, and (ii) laminar flame speed data at several preheat temperatures, also for ambient and elevated pressure, gathered from literature. Chemical kinetic modeling will be used for an in-depth characterization of ignition delays and flame speeds at technical relevant conditions. An extensive database will be presented identifying the characteristic differences of the combustion properties of NG, ethanol, and ethanol cofired to NG.

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Shockless Explosion Combustion: Experimental Investigation of a New Approximate Constant Volume Combustion Process

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2016-57680 ◽

2016 ◽

Cited By ~ 1

Author(s):

Thoralf G. Reichel ◽

Bernhard C. Bobusch ◽

Christian Oliver Paschereit ◽

Jan-Simon Schäpel ◽

Rudibert King ◽

...

Keyword(s):

Shock Waves ◽

Ignition Delay ◽

Gas Turbines ◽

Control Algorithm ◽

Ambient Pressure ◽

Pressure Sensors ◽

Constant Volume ◽

Ignition Delay Times ◽

Delay Times ◽

Constant Volume Combustion

Approximate constant volume combustion (aCVC) is a promising way to achieve a step change in the efficiency of gas turbines. This work investigates a recently proposed approach to implement aCVC in a gas turbine combustion system: shockless explosion combustion (SEC). The new concept overcomes several disadvantages such as sharp pressure transitions, entropy generation due to shock waves, and exergy losses due to kinetic energy which are associated with other aCVC approaches like, e.g., pulsed detonation combustion. The combustion is controlled via the the fuel/air mixture distribution which is adjusted such that the entire fuel/air volume undergoes a spatially quasi-homogeneous autoignition. Accordingly, no shock waves occur and the losses associated with a detonation wave are not present in the proposed system. Instead, a smooth pressure rise is created due to the heat release of the homogeneous combustion. An atmospheric combustion test rig is designed to investigate the autoignition behavior of relevant fuels under intermittent operation, currently up to a frequency of 2Hz. Application of OH*- and dynamic pressure sensors allows for a spatially- and time-resolved detection of ignition delay times and locations. Dimethyl ether (DME) is used as fuel since it exhibits reliable autoignition already at 920K mixture temperature and ambient pressure. First, a model-based control algorithm is used to demonstrate that the fuel valve can produce arbitrary fuel profiles in the combustion tube. Next, the control algorithm is used to achieve the desired fuel stratification, resulting in a significant reduction in spatial variance of the auto-ignition delay times. This proves that the control approach is a useful tool for increasing the homogeneity of the autoignition.

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Experimental Study and Modeling of Autoignition of Natural Gas/Air-Mixtures Under Gas Turbine Relevant Conditions

Volume 2: Turbo Expo 2005 ◽

10.1115/gt2005-68405 ◽

2005 ◽

Cited By ~ 2

Author(s):

Andreas Koch ◽

Clemens Naumann ◽

Wolfgang Meier ◽

Manfred Aigner

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Ignition Delay ◽

Delay Time ◽

High Speed ◽

Ignition Delay Time ◽

Evaluation Procedure ◽

Ignition Process ◽

Ignition Delay Times ◽

Delay Times

The objective of this work was the improvement of methods for predicting autoignition in turbulent flows of different natural gas mixtures and air. Measurements were performed in a mixing duct where fuel was laterally injected into a turbulent flow of preheated and pressurized air. To study the influence of higher order hydrocarbons on autoignition, natural gas was mixed with propane up to 20% by volume at pressures up to 15 bar. During a measurement cycle, the air temperature was increased until autoignition occurred. The ignition process was observed by high-speed imaging of the flame chemiluminescence. In order to attribute a residence time (ignition delay time) to the locations where autoignition was detected the flow field and its turbulent fluctuations were simulated by numerical codes. These residence times were compared to calculated ignition delay times using detailed chemical simulations. The measurement system and data evaluation procedure are described and preliminary results are presented. An increase in pressure and in fraction of propane in the natural gas both reduced the ignition delay time. The measured ignition delay times were systematically longer than the predicted ones for temperatures above 950 K. The results are important for the design process of gas turbine combustors and the studies also demonstrate a procedure for the validation of design tools under relevant conditions.

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