Patent Application
20110240769
The subject matter disclosed herein relates to a variable area fuel nozzle.
Dry Low NOx (DLN) combustors are widely used for power generation as well as oil and gas production applications and are mainly designed for use with natural gas fuel and/or liquid fuels. New applications of the combustors are, however, beginning to demand that the combustors exhibit wider fuel flexibility. For example, in many cases currently operating combustors must have the capability to operate on natural gas fuels and then switch to low British Thermal Unit (BTU) fuels where fuel flow rates double and still meet emissions and operability requirements.
In these cases, as fuel flow rates of the alternate fuels can be significantly greater than those of other fuels, additional circuits need to be installed to maintain fuel side pressure ratios to satisfy fuel delivery specifications. These additional circuits often require active controls, purge circuits and/or additional equipment and are, therefore, expensive and costly to maintain. In addition, dynamics effects due to varying pressure levels within the circuits can be problematic.
According to one aspect of the invention, a nozzle is provided and includes a circuit by which fuel is delivered to a nozzle part and a valve, interposed between the circuit and the nozzle part and upon which the fuel impinges, an opening and closing of the valve being passively responsive to a fuel pressure in the circuit such that the valve thereby modulates a size of an area through which a corresponding quantity of the fuel flows from the circuit to the nozzle part.
According to another aspect of the invention, a nozzle is provided and includes a selectively operated circuit, including a body formed to define an orifice, by which fuel is delivered to a nozzle part and a valve, interposed between the circuit and the nozzle part and upon which the fuel impinges, which passively opens and closes the orifice in response to a fuel pressure in the circuit, the opening and closing of the orifice by the valve thereby modulating a size of an area through which a corresponding quantity of the fuel flows from the circuit to the nozzle part.
According to yet another aspect of the invention, a nozzle is provided and includes a selectively operated circuit, including a body formed to define one or more orifices, by which fuel is delivered to a nozzle part and a valve associated with each of the orifices, each valve being interposed between the circuit and the nozzle part and upon each of which the fuel impinges, which passively opens and closes the respective orifice in response to a fuel pressure in the circuit, the opening and closing of the respective orifices by each of the valves thereby modulating a size of an area through which a corresponding quantity of the fuel flows from the circuit to the nozzle part.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
A dual gas fuel nozzle allows for use of a relatively wide range of molecular wobbe index fuels in hardware geometries. This dual gas fuel nozzle can burn up to about 100% natural gas fuel to low British Thermal Unit (BTU) fuels having about 100 to about 400 BTUs per standard cubic foot, like high reactivity syngas or low reactivity highly diluted streams, by utilizing passively or actively controlled multiple internal fuel passages located within the fuel nozzle. For example, two circuits may be employed and joined internally to a fuel nozzle where one fuel stream provides shielding to the other and prevents it from direct exposure and ingestion of hot combustor flame or combustion products that, if remain unpurged, could result in hardware damage.
At least one of these circuits provides for a variable flow area that is regulated passively or actively actuated by the fuel side pressure. As the pressure in the fuel circuit rises due to increased mass flow, a valve or some other suitable device disposed with respect to the circuit opens and provides variable fuel flow area to meet the flow demand while maintaining reasonable fuel feed stream pressures. Valve settings and features can be custom designed based on the application demands.
With reference to
In accordance with embodiments, the second fuel is a relatively low BTU fuel as compared to the first fuel. For example, the first fuel may include natural gas or a combination of natural gas and synthetic gas (Syngas) whereas the second fuel may include only Syngas. The second and the first fuel can also be the same fuel such as low BTU Syngas. The second fuel circuit 30 may be selectively operated in accordance with internal and external conditions, such as the availability of certain fuels and, in a case where the fuel nozzle 10 is a component of a gas turbine engine, turbine loads that require a given level of energy production from the available fuels.
The first fuel circuit 20 and the second fuel circuit 30 may each be annular in shape with the second fuel circuit 30 disposed within the first fuel circuit 20. Each may terminate at similar axial locations proximate to the nozzle part 40. The second fuel circuit 30 may be defined through a circuit body 31 with the first fuel circuit 20 being defined through an annular space between the circuit body 31 and annular casing 21. The nozzle part 40 includes section 41 aligned with the annular casing 21 and partially surrounding an end of the circuit body 31.
The valve 50 may be spring-loaded and linearly responsive to a change in the second fuel pressure. That is, the valve 50 may open and close in direct proportion to increases or decreases in the second fuel pressure. In alternate embodiments, the valve 50 may be non-linearly responsive to the second fuel pressure changes. Here, the valve 50 opens and closes more or less responsively as the second fuel pressure increases or decreases significantly. In still further embodiments, the valve 50 may be linearly responsive to relatively small or large second fuel pressure changes and non-linearly responsive to relatively large or small second fuel pressure changes. In a similar manner, the spring-loaded valve 50 may be configured to at least one of linearly and non-linearly modulate the size of the area in passive response to second fuel pressure changes.
With reference now to
Referring to
With this construction, the valve 50 admits second fuel to the nozzle part 40 at a predefined second fuel pressure sufficient to energize the first elastic member 84 and continues to admit increasing quantities of the second fuel as the second fuel pressure increases and the downstream head 82 recedes from the valve seat 32.
As shown in
With reference to
As mentioned above and with reference to
The valve 50 may include a boss 150 disposed along the orifice 60, a valve body 160 having a surface 161, upon which the second fuel impinges, and a second elastic member 170, which may include a spring and which is passively responsive to the second fuel pressure. The second elastic member 170 serves to bias the valve body 160 toward the boss 150 to thereby urge closure of the orifice 60.
With this construction, the closure of the orifice 60 is achieved at predefined second fuel pressures insufficient to energize the second elastic member 170 such that complementary surface profiles 171, 172 of the valve body 160 and the boss 150 abut one another. The valve 50 admits second fuel to the nozzle part 40 at a predefined second fuel pressure sufficient to energize the second elastic member 170 and continues to admit increasing quantities of the second fuel as the second fuel pressure increases and the valve body 160 recedes from the boss 150.
Although the valve 50 is illustrated in
The boss 150 may be formed as a component of an insert 180 that is removably insertable into the radial or the axial component 142, 143. In this case, the insert 180 may include a screw-top 181 and both the insert and the sidewall of the orifice 60 may include complementary threading such that the insert 180 can be screwed into the orifice 60 for fastening. This is, of course, merely exemplary and it is understood that other fastening systems for the insert 180 may be provided.
The second elastic member 170 may be anchored to a second boss 190 downstream from the boss 150. Here, the second boss 190 may be formed as part of the sidewall of the orifice 60 or as a further separate component. In any case, the second boss 190 supports the second elastic member 170 and the valve body 160 against the second fuel pressure.
As shown in
The descriptions provided above can be applied to eliminate air purge requirements for DLN and/or multi-nozzle quiet combustors (MNQC), single nozzle arrays or any fuel nozzle that requires multiple fuels circuits in the combustor. Eliminating purge circuits and equipments can provide significant hardware and contractual cost savings that can multiply at fleet level. Also, passively controlled valves provide variable area geometry for changing a fuel wobbe index throughout the operating range of a system to thereby increase fuel flexibility of the system. Moreover, variable area geometries mitigate dynamics effects due to reduced fuel side pressure fluctuations.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
