Size scaling of a burner

Abstract

A method for upscaling the size of a burner of a gas turbine engine including a burner housing is provided. The burner is provided with a mixture of fuel and air at an upstream end from a premixing channel that sustains a main flame at a downstream end of the burner. The premixing channel is defined at the exit by a circular inner wall formed by an inner quarl section and a circular outer wall formed by an outer quarl section. The burner may be increased in size by adding a quarl section outside and circumferentiating the quarl section and forming an annular space between the added quarl section and the existing outer quarl section and by adding a premixing channel defined at the exit by a circular inner wall formed by the previously outmost quarl section and the circular outer wall formed by the added quarl section.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is the US National Stage of International Application No. PCT / EP2009 / 053555, filed Mar. 26, 2009 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 08006666.5 EP filed Apr. 1, 2008. All of the applications are incorporated by reference herein in their entirety.TECHNICAL FIELD[0002]The present invention refers to quarls in a burner preferably for use in gas turbine engines, and more particularly to quarls in a burner adapted to stabilize engine combustion, and further to a burner that use a pilot combustor to provide combustion products to stabilize main lean premixed combustion.TECHNICAL BACKGROUND[0003]Gas turbine engines are employed in a variety of applications including electric power generation, military and commercial aviation, pipeline transmission and marine transportation. In a gas turbine engine which operates in LPP mode, fuel and air are ...

AI Technical Summary

Benefits of technology

[0014]Disclosed is a lean-rich partially premixed low emissions burner for a gas turbine combustor that provides stable ignition and combustion process at all engine load conditions. This burner operates according to the principle of “supplying” heat and high concentration of free radicals from a pilot combustor exhaust to a main flame burning in a lean premixed air / fuel swirl, whereby a rapid and stable combustion of the main lean premixed flame is supported. The pilot combustor supplies heat and supplements a high concentration of free radicals directly to a forward stagnation point and a shear layer of the main swirl induced recirculation zone, where the main lean premixed flow is mixed with hot gases products of combustion provided by the pilot combustor. This allows a leaner mix and lower temperatures of the main premixed air / fuel swirl combustion that otherwise would not be self-sustaining in swirl stabilized recirculating flows during the operating conditions of the burner.

[0018]The burner utilizes:A swirl of air / fuel above swirl number (Sn) 0.7 (that is above critical Sn=0.6), generated-imparted into the flow, by a radial swirler;active species—non-equilibrium free radicals being released close to the forward stagnation point,particular type of the burner geometry with a multi quarl device, andinternal staging of fuel and air within the burner to stabilize combustion process at all gas turbine operating conditions.In short, the disclosed burner provides stable ignition and combustion process at all engine load conditions. Some important features related to the inventive burner are:the geometric location of the burner elements;the amount of fuel and air staged within the burner;the minimum amount of active species—radicals generated and required at different engine / burner operating conditions;fuel profile;mixing of fuel and air at different engine operating conditions;imparted level of swirl;multi (minimum double quarl) quarl arrangement.

[0027]provides a flame front (main recirculation zone) anchoring the flame in a defined position in space, without a need to anchore the flame to a solid surface / bluff body, and in that way a high thermal loading and issues related to the burner mechanical integrity are avoided;

[0030]optimal quarl half angle α should not be smaller then 20 and larger then 25 degrees, allows for a lower swirl before decrease in stability, when compared to a less confined flame front; and

[0031]has the important task to control the size and shape of the recirculation zone as the expansion of the hot gases as a result of combustion reduces transport time of free radicals in the recirculation zone.

Problems solved by technology

The major problems associated with the combustion process in gas turbine engines, in addition to thermal efficiency and proper mixing of the fuel and the air, are associated to flame stabilization, the elimination of pulsations and noise, and the control of polluting emissions, especially nitrogen oxides (NOx), CO, UHC, smoke and particulated emission

A less stable, easy to move flame front of a pre-mixed flame results in a periodic heat release rate, that, in turn, results in movement of the flame, unsteady fluid dynamic processes, and thermo-acoustic instabilities develop.

When the heat required for reactions to occur is the stability-limiting factor, very small temporal fluctuations in fuel / air equivalence ratios (which could either result either from fluctuation of fuel or air flow through the Burner / Injector) can cause flame to partially extinguish and re-light.

When the flame can, more easily, occur in multiple positions, it becomes more unstable.

Images