DESCRIPTION

TECHNICAL FIELD Embodiments of the subject matter disclosed herein correspond to gas turbine fuel nozzles with integrated flame ionization sensor and gas turbine engines.

BACKGROUND ART

It is known that the generation and the movement of ions in a flame are very useful parameters for monitoring the flame and the combustion and the use of sensors therefor.

In principle, a single flame ionization sensor may replace a whole set of sensors dedicated to a corresponding set of flame and/or combustion indicators.

Anyway, incorporating a flame ionization sensor in a combustor of a gas turbine engine is not trivial at all; in fact, in such applications, any component facing the combustion chamber is critical from the shape point of view due to the gasses flows and risks of being damaged by the hostile environment (high temperature, high pressure, aggressive gasses, etc.) present in the combustion chamber. Another requirement for such sensor is its placing so that it can be replaced easily. Furthermore, in the field of "Oil & Gas", a very high reliability is required to the machines in general and consequently to their components, including sensors.

Therefore, in the field of "Oil & Gas", flame ionization sensors are quite seldom used in gas turbine engines.

SUMMARY It is to be noted that in a gas turbine engine having a combustor with a single annular-shaped chamber and a plurality of fuel nozzles one or few (for example two or three or four or more) flame ionization sensors may be sufficient for serving the whole turbine diagnosis and control; anyway, such sensors have never been used for such applications. Therefore, there is a general need for a gas turbine fuel nozzle with integrated flame ionization sensor and a corresponding gas turbine engine. This need is particularly felt in gas turbine engines comprising a combustor with a single annular-shaped chamber.

First embodiments of the subject matter disclosed herein relate to a gas turbine fuel nozzle.

According to such nozzle, there is a sleeve with an internal duct for premixed fuel gas flow; it further comprises a flame ionization sensor located on said sleeve externally to the duct.

Second embodiments of the subject matter disclosed herein relate to a gas turbine engine.

According to such gas turbine engine, there is a combustor with a single annular- shaped chamber; it further comprises a plurality of fuel nozzles with one or more integrated flame ionization sensors.

BRIEF DESCRIPTION OF DRAWINGS The accompanying drawings, which are incorporated herein and constitute an integral part of the present specification, illustrate exemplary embodiments of the present invention and, together with the detailed description, explain these embodiments. In the drawings:

Fig. 1 shows a partial cross-section view of an embodiment of a combustor of a gas turbine engine;

Fig. 2 shows a cross-section view of an embodiment of a fuel nozzle; Fig. 3 shows a schematic front view of an embodiment of a combustor of a gas turbine engine;

Fig. 4 shows a schematic front view of an embodiment of a fuel nozzle;

Fig. 5 shows a partial cross-section view of a first embodiment of a fuel nozzle with one integrated flame ionization sensor;

Fig. 6 shows a partial cross-section view of a second embodiment of a fuel nozzle with one integrated flame ionization sensor;

Fig. 7 shows a partial cross-section view of a third embodiment of a fuel nozzle with one integrated flame ionization sensor; Fig. 8 shows a partial cross-section view of a fourth embodiment of a fuel nozzle with one integrated flame ionization sensor; and

Fig. 9 shows a partial cross-section view of a fifth embodiment of a fuel nozzle with two integrated flame ionization sensors.

DETAILED DESCRIPTION The following description of exemplary embodiments refers to the accompanying drawings.

The following description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. Figure 1 shows a partial cross-section view of an embodiment of a combustor 101 of a gas turbine engine 100; a single annular-shaped chamber 102 is located inside a case 103.

Figure 3 shows a schematic front view of the combustion chamber 102 of Figure 1.

The combustor 101 comprises a plurality of fuel nozzles 1 (shown both in Figure 1 and in Figure 3).

The fuel nozzles 1 have one or more integrated flame ionization sensors; this is schematically shown in Figure 2 where the sensor is associated to reference 4.

An embodiment of a fuel nozzle 1 is shown both in Figure 2 (cross-section view) and in Figure 4 (schematic front view).

The gas turbine fuel nozzle 1 comprises a cylindrical metallic sleeve 2 with an internal circular (cross-section) duct 3 for premixed fuel gas flow. A plurality of ducts 21 for fuel gas flow are arranged as a crown inside the peripheral wall of sleeve 2 and end on a front side of sleeve 2. Inside duct 3, coaxially to sleeve 2, there is a body 22. Ducts 21 are in fluid communication with a conduit 23 for air gas flow. A conduit 24 ends at a back side of sleeve 2 so to feed premixed fuel gas flow. A conduit 25 feeds an air gas flow to body 22 so to eject air inside duct 3 close to the end of sleeve 2. There is a support arm 6 integrated with sleeve 2; support arm 6 houses conduit 23 and conduit 24; in general, nozzle support may partially or completely house at least one gas flow conduit for the nozzle.

A nozzle like the one shown in the figures, in particular Figure 2, is described and shown in detail in US patent n° 6,363,725, assigned to the present Applicant, that is incorporated herewith by reference.

As schematically shown for example in Figure 2, nozzle 1 further comprises a flame ionization sensor 4 located on sleeve 2 externally to duct 3. The flame ionization sensor is advantageously located at an end zone of the sleeve where premixed fuel gas flow is ejected - see e.g. Figure 2.

In particular, flame ionization sensor may be located on a external lateral side or on a front side of the sleeve. In the embodiment of Figure 2, the sensor 4 is located on a external lateral side. In the embodiments of Figures 5-9, the sensor 4 is located on a front side of the sleeve; in particular, sensor 4 is located on a front side of sleeve 2 at an outer portion of said sleeve 2.

The flame ionization sensor 4 of the embodiments of Figures 5-9 comprises a metallic (full or partial) annulus 41 being an electrode of the sensor. Annulus 41 may be electrical isolated from sleeve 2 e.g. by an underlying isolating (full or partial) annulus 42; the material of annulus 42 may be for example ceramic or ceramic oxide. Such design of sensor 4 may be used also for sensor 5 in Figure 9.

The flame ionization sensor is to be electrically connected to an electric cable for feeding the generated signal to a monitoring and/or controlling electronic unit.

Preferably, the electric cable is a rigid shielded mineral- insulated cable (schematically shown in Figures 5-7 as element 43). Shielding the cable is very advantageous due to the "noisy" environment of a gas turbine engine; shielding may be done through a metal cladding, for example made of AISI 316 or INCONEL 600.

The electric cable may be fixed to support arm 6. In general, nozzle support may partially or completely house at least one (shielded) electric cable for a sensor.

In the embodiment of Figure 9, there is another flame ionization sensor 5 located on a front side of sleeve 2 and externally to duct 3, preferably at an inner portion sleeve 2.

The sensor 5 of the embodiment of Figure 9 comprises a metallic (full or partial) annulus 51 being an electrode of the sensor. Annulus 51 may be electrical isolated from sleeve 2 e.g. by an underlying isolating (full or partial) annulus 52; the material of annulus 52 may be for example ceramic or ceramic oxide.

In the embodiment of Figure 9, sensor 4 is preferably used as a primary flame ionization sensor and sensor 5 is preferably used as flashback flame ionization sensor.

In figures 5-9, an end portion of a duct 21 inside sleeve 2 (surrounding duct 3) is shown that ends with a conical outlet ("T" degrees wide) for a pilot flame.

In the embodiment of Figure 5, a metallic component 41 of the flame ionization sensor 4 forms part of the external lateral side of sleeve 2, part of the front side of sleeve 2 (i.e. part of the conical outlet), and part of the surface of duct 21.

In the embodiment of Figure 6, a metallic component 41 of the flame ionization sensor 4 forms part of the external lateral side of sleeve 2, part of the front side of sleeve 2 (i.e. part of the conical outlet), and is spaced from the surface of duct 21 through e.g. isolating component 42.

In the embodiment of Figure 7, a metallic component 41 of the flame ionization sensor 4 forms part of the external lateral side of sleeve 2, and is spaced from the front side of sleeve 2 (i.e. part of the conical outlet) through e.g. only isolating component 42, and from the surface of duct 21 through e.g. isolating component 42.

In the embodiment of Figure 8, a metallic component 41 of the flame ionization sensor 4 forms only part of the front side of sleeve 2 (i.e. part of the conical outlet) and is surrounded by isolating component 42.

In the embodiment of Figure 9, a metallic component 41 of a first flame ionization sensor 4 forms part of the external lateral side of sleeve 2, part of the front side of sleeve 2 (i.e. part of the conical outlet), and part of the surface of duct 21; and a metallic component 51 of a second flame ionization sensor 5 forms part of the internal lateral side of sleeve 2, part of the front side of sleeve 2 (i.e. part of the conical outlet), and part of the surface of duct 21. Embodiments of the gas turbine fuel nozzle disclosed herein may be used for monitoring combustion in a gas turbine engine, in particular flashback combustion.