Venturi

Abstract

A venturi is disclosed, the venturi comprising a mixing cavity surrounded circumferentially by an annular venturi wall, and a swirler having a plurality of vanes arranged circumferentially around a swirler axis, wherein the swirler and the annular venturi wall have a unitary construction. In another exemplary embodiment the venturi comprises an annular venturi wall, a swirler located at an axially forward portion of the venturi, the swirler having a plurality of vanes arranged circumferentially around a swirler axis, and a heat shield located axially aft from the swirler, wherein the annular venturi wall, the swirler and the heat shield have a unitary construction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This Application claims priority to U.S. Provisional Application Ser. No. 61 / 044,116, filed Apr. 11, 2008, which is herein incorporated by reference in its entirety.BACKGROUND OF THE INVENTION[0002]This invention relates generally to venturis, and more specifically to unitary venturis having swirlers for promoting mixing of fuel and air and a heat shield for protection from combustion heat in fuel nozzles used in gas turbine engines.[0003]Turbine engines typically include a plurality of fuel nozzles for supplying fuel to the combustor in the engine. The fuel is introduced at the front end of a burner in a highly atomized spray from a fuel nozzle. Compressed air flows around the fuel nozzle and mixes with the fuel to form a fuel-air mixture, which is ignited by the burner. Because of limited fuel pressure availability and a wide range of required fuel flow, many fuel injectors include pilot and main nozzles, with only the pilot nozzles bei...

AI Technical Summary

Problems solved by technology

Because of limited fuel pressure availability and a wide range of required fuel flow, many fuel injectors include pilot and main nozzles, with only the pilot nozzles being used during start-up, and both nozzles being used during higher power operation.

For example, one way in which the problem of minimizing the emission of undesirable gas turbine engine combustion products has been attacked is the provision of staged combustion.

It will be appreciated that balancing the operation of the first and second stage burners to allow efficient thermal operation of the engine, while simultaneously minimizing the production of undesirable combustion products, is difficult to achieve.

In that regard, operating at low combustion temperatures to lower the emissions of NOx, can also result in incomplete or partially incomplete combustion, which can lead to the production of excessive amounts of HC and CO, in addition to producing lower power output and lower thermal efficiency.

Over time, continued exposure to high temperatures during turbine engine operations may induce thermal gradients and stresses in the conduits and fuel nozzles which may damage the conduits or fuel nozzle and may adversely affect their operation.

For example, thermal gradients may cause fuel flow reductions in the conduits and may lead to excessive fuel maldistribution within the turbine engine.

Exposure of fuel flowing through the conduits and orifices in a fuel nozzle to high temperatures may lead to coking of the fuel and lead to blockages and non-uniform flow.

To provide low emissions, modern fuel nozzles require numerous, complicated internal air and fuel circuits to create multiple, separate flame zones.

Furthermore, over time, continued operation with damaged fuel nozzles may result in decreased turbine efficiency, turbine component distress, and / or reduced engine exhaust gas temperature margin.

Conventional gas turbine engine components such as, for example, fuel nozzles and their associated swirlers, conduits, distribution systems, venturis and mixing systems are generally expensive to fabricate and / or repair because the conventional fuel nozzle designs having complex swirlers, conduits and distribution circuits and venturis for transporting, distributing and mixing fuel with air include a complex assembly and joining of more than thirty components.

More specifically, the use of braze joints can increase the time needed to fabricate such components and can also complicate the fabrication process for any of several reasons, including: the need for an adequate region to allow for braze alloy placement; the need for minimizing unwanted braze alloy flow; the need for an acceptable inspection technique to verify braze quality; and, the necessity of having several braze alloys available in order to prevent the re-melting of previous braze joints.

Moreover, numerous braze joints may result in several braze runs, which may weaken the parent material of the component.

The presence of numerous braze joints can undesirably increase the weight and manufacturing cost of the component.

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