Combustion Characteristics of Multicomponent Fuels Under Cold Starting Conditions in a Gas Turbine

This paper describes a theoretical study of combustion in mixtures of fuel vapour, droplets and air under conditions representative of cold starting in gas turbines. It combines two previously developed models — one for heterogeneous flame propagation and the other for describing the complex evaporative behaviour of real fuel blends. Both models have been validated against experimental data, and the combined model is used to investigate the effect of fuel properties and injection system performance on minimum ignition energy, blowout velocity, lean extinction limits and related aspects significant for cold starting. Conditions are identified when fuel volatility is important and single component approximations are unrepresentative of real fuel behaviour. Explicit equations are given which predict the vapour pressures of JP-4, Jet A1 and diesel fuel.

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Ignition and flame quenching of quiescent fuel mists

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1978.0201 ◽

1978 ◽

Vol 364 (1717) ◽

pp. 277-294 ◽

Cited By ~ 41

Keyword(s):

Reaction Rates ◽

Ignition Energy ◽

Minimum Ignition Energy ◽

Proposed Model ◽

Theoretical Predictions ◽

Quenching Distance ◽

Experimental Values ◽

Sole Criterion ◽

Fuel Vapour ◽

Level Of Agreement

A model is proposed for the ignition of quiescent multidroplet fuel mists which assumes that chemical reaction rates are infinitely fast, and that the sole criterion for successful ignition is the generation, by the spark, of an adequate concentration of fuel vapour in the ignition zone. From analysis of the relevant heat transfer and evaporation processes involved, expressions are derived for the prediction of quenching distance and minimum ignition energy. Support for the model is demonstrated by a close level of agreement between theoretical predictions of minimum ignition energy and the corresponding experimental values obtained using a specially designed ignition apparatus in which ignition energies are measured for several different fuels, over wide ranges of pressure, mixture composition and mean drop size. The results show that both quenching distance and minimum ignition energy are strongly dependent on droplet size, and are also dependent, but to a lesser extent, on air density, equivalence ratio and fuel volatility. An expression is derived to indicate the range of drop sizes over which the proposed model is valid.

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Fuel Flexibility at Ignition Conditions for Industrial Gas Turbines

Volume 1B: Combustion, Fuels and Emissions ◽

10.1115/gt2013-95536 ◽

2013 ◽

Cited By ~ 1

Author(s):

Anders Larsson ◽

Anton Berg ◽

Alessio Bonaldo

Keyword(s):

Mathematical Model ◽

Gas Turbine ◽

Gas Turbines ◽

Inert Gases ◽

Ignition Energy ◽

Minimum Ignition Energy ◽

Fuel Flexibility ◽

Start Up ◽

Gas Fuel ◽

The Mathematical Model

The variety of gaseous fuels that Siemens Industrial Turbomachinery (SIT) is requested to consider during sales enquiries has prompted product development projects that have allowed to continuously increase gas turbine fuel flexibility. The fuel flexibility often has to be guaranteed at all engine load conditions including ignition. The gas turbine ignition capabilities have therefore been analyzed in order to assess the engines current capabilities and identify further potentials. The authors’ approach for ignition fuel flexibility has been to model the minimum ignition energy (MIE) required for successful ignition and to validate the model by experiments conducted under test conditions reproducing engine start up flows at a combustion test rig. The experiments were performed using two hydrocarbon gases individually mixed with two inert gases at various concentrations. The mathematical model predicting the minimum ignition energy is applicable also to hydrocarbon and inert gases mixtures that were not used during the experimental campaign. The model was studied and developed in order to produce a tool for support of gas fuel enquiries received during the sales phase. In accordance to the predictions of the mathematical model, the experimental validation in the paper shows that the difference in MIE required to ignite the gas fuel composition depends on the inert gas used as well as the hydrocarbon used. The MIE model showed the capability of assessing if a specific gas composition can be used as a reliable start-up fuel.

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Potentially explosive atmospheres. Explosion prevention and protection. Determination of minimum ignition energy of dust/air mixtures

10.3403/02704478 ◽

2002 ◽

Cited By ~ 1

Keyword(s):

Ignition Energy ◽

Minimum Ignition Energy

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State of Art of Using Biofuels in Spark Ignition Engines

Energies ◽

10.3390/en14030779 ◽

2021 ◽

Vol 14 (3) ◽

pp. 779

Author(s):

Ashraf Elfasakhany

Keyword(s):

Engine Performance ◽

Spark Ignition ◽

Pollutant Emissions ◽

Spark Ignition Engines ◽

Engine Emissions ◽

Cold Starting ◽

Starting Conditions ◽

Unburned Hydrocarbons ◽

Scientific Attention ◽

State Of Art

Biofuels are receiving increased scientific attention, and recently different biofuels have been proposed for spark ignition engines. This paper presents the state of art of using biofuels in spark ignition engines (SIE). Different biofuels, mainly ethanol, methanol, i-butanol-n-butanol, and acetone, are blended together in single dual issues and evaluated as renewables for SIE. The biofuels were compared with each other as well as with the fossil fuel in SIE. Future biofuels for SIE are highlighted. A proposed method to reduce automobile emissions and reformulate the emissions into new fuels is presented and discussed. The benefits and weaknesses of using biofuels in SIE are summarized. The study established that ethanol has several benefits as a biofuel for SIE; it enhanced engine performance and decreased pollutant emissions significantly; however, ethanol showed some drawbacks, which cause problems in cold starting conditions and, additionally, the engine may suffer from a vapor lock situation. Methanol also showed improvements in engine emissions/performance similarly to ethanol, but it is poisonous biofuel and it has some sort of incompatibility with engine materials/systems; its being miscible with water is another disadvantage. The lowest engine performance was displayed by n-butanol and i-butanol biofuels, and they also showed the greatest amount of unburned hydrocarbons (UHC) and CO emissions, but the lowest greenhouse effect. Ethanol and methanol introduced the highest engine performance, but they also showed the greatest CO2 emissions. Acetone introduced a moderate engine performance and the best/lowest CO and UHC emissions. Single biofuel blends are also compared with dual ones, and the results showed the benefits of the dual ones. The study concluded that the next generation of biofuels is expected to be dual blended biofuels. Different dual biofuel blends are also compared with each other, and the results showed that the ethanol–methanol (EM) biofuel is superior in comparison with n-butanol–i-butanol (niB) and i-butanol–ethanol (iBE).

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Reduction of NOx Emission of Heavy Duty Gas Turbines by Improving Mixing Quality Using CFD Tools

Energy Conversion and Resources: Fuels and Combustion Technology, Energy, Nuclear Engineering, and Solar Engineering ◽

10.1115/imece2003-41268 ◽

2003 ◽

Author(s):

Weiqun Geng ◽

Douglas Pennell ◽

Stefano Bernero ◽

Peter Flohr

Keyword(s):

Gas Turbines ◽

Mass Fraction ◽

Cross Flow ◽

Nox Emission ◽

Injection System ◽

Water Tunnel ◽

Injection Hole ◽

Fuel Mass ◽

Mixing Quality ◽

Fuel Mass Fraction

Jets in cross flow are one of the fundamental issues for mixing studies. As a first step in this paper, a generic geometry of a jet in cross flow was simulated to validate the CFD (Computational Fluid Dynamics) tool. Instead of resolving the whole injection system, the effective cross-sectional area of the injection hole was modeled as an inlet surface directly. This significantly improved the agreement between the CFD and experimental results. In a second step, the calculated mixing in an ALSTOM EV burner is shown for varying injection hole patterns and momentum flux ratios of the jet. Evaluation of the mixing quality was facilitated by defining unmixedness as a global non-dimensional parameter. A comparison of ten cases was made at the burner exit and on the flame front. Measures increasing jet penetration improved the mixing. In the water tunnel the fuel mass fraction within the burner and in the combustor was measured across five axial planes using LIF (Laser Induced Fluorescence). The promising hole patterns chosen from the CFD computations also showed a better mixing in the water tunnel than the other. Distribution of fuel mass fraction and unmixedness were compared between the CFD and LIF results. A good agreement was achieved. In a final step the best configuration in terms of mixing was checked with combustion. In an atmospheric test rig measured NOx emissions confirmed the CFD prediction as well. The most promising case has about 40% less NOx emission than the base case.

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