BOLT ON FUEL NOZZLE TIP
Publication Date: 2012-Dec-31
The IP.com Prior Art Database
The present invention relates to a bolt on nozzle tip for gas turbines. The bolt on nozzle tip can be retrofitted and comprises a spring energized c-seal. Bolt on design applies a uniform axial load on the c-seals thereby eliminating spalling of silver coating on the c-seal due to shearing. Spring-energized c-seal provides better sealing due to its higher stiffness and spring back. The stiffer spring energized seal works well provides a bubble tight seal. The bolted tip design stops overboard fuel leaks that cause higher CO emissions during gas turbine operation.
The present invention relates generally to fuel nozzle tips for gas turbines and more particularly to a bolt on fuel nozzle tip with a spring energized c-seal.
In general, c-seals used in fuel nozzle tips are metal seals with a threaded design that requires seal surface to move relative to the seal to crush it. Such a design strips the seal coating. Also, conventional c-seal applications utilize high pressure differential to apply normal force to sealing surfaces. However, the aforementioned application requires low-pressure differential sealing. Under such requirement typical c-seals do not provide a bubble tight seal. Such design utilized a large thread in fuel nozzle tip, in which both male and female threads are made from stainless steel that has a tendency to gall, additionally it is easy for assemblers to over-torque the nozzle tip and cause thread deformation and subsequent cross-threading. Further, anti-seize mask leaks that would otherwise be noticed during assembly leak checks, once the parts are fired in a unit.
Furthermore, conventional designs have an anti-rotational staked lock plate. The lock plate becomes movable during operation allowing unthreading of nozzle tip and potentially leading to a liberated part sent into gas turbine hot gas path. To prevent such undesired nozzle unthreading events, several service centres apply tack welds to the lock plate. However, the lock plate is located close to seal surface and application of heat in this location may warp the seal surface and promote leaks. Such design requires one of the two seal surfaces to be prominent in the main component of the assembly leading to damage of the sealing surface due to component handling. Damage of sealing surface promotes leaks.
Conventional nozzle tip design requirements suffer several disadvantages including additional processes such as extensive welding of boss features, subsequent machining and huge cost. Different designs were developed to increase the sealing surface area and improve the surface finish on threaded design but none were completely effective due to recurring spalling of silver coating. Further, a bigger c-seal is used in such conventional designs to improve the spring back and bigger c-seal further promotes spalling of silver coating.
Therefore, it would be desirable to have an improved design for fuel nozzle tips that reduces spalling of silver coating, fuel leaks and provides bubble tight sealing.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a bolt on design of fuel nozzle tip with spring energized c-seal.
Figure 2 illustrates spalling of silver coating on c-seal.
Figure 3 illustrates an assembled bolted nozzle.
Figure 4 illustrates a 6b primary nozzle assembly.
Figure 5 illustrates a model of 6b primary nozzle tip.
The present invention could apply to c-seals of E-class combustors. The invention disclosed herein is a design to bolt...