Patent Application
20180142570
This invention relates generally to a fuel delivery system for a gas turbine engine and, more particularly, to a fuel delivery system for a gas turbine engine that includes a flow divider positioned downstream from a multifunction valve that allows purge water to be pumped upstream through the multifunction valve to a drain.
The world's energy needs continue to rise which provides a demand for reliable, affordable, efficient and environmentally-compatible power generation. A gas turbine engine is one known machine that provides efficient power, and often has application for an electric generator in a power plant, or engines in an aircraft or a ship. A typical gas turbine engine includes a compressor section, a combustion section and a turbine section. The compressor section provides a compressed airflow to the combustion section where the air is mixed with a fuel, such as natural gas, diesel fuel oil, etc. The combustion section includes a plurality of circumferentially disposed combustors that receive the fuel to be mixed with the air and ignited to generate a working gas. The working gas expands through the turbine section and is directed across rows of blades therein by associated vanes. As the working gas passes through the turbine section, it causes the blades to rotate, which in turn causes a shaft to rotate, thereby providing mechanical work.
Some gas turbine engines of the type referred to above include a fuel delivery system that delivers a liquid fuel oil under a suitable pressure and flow rate to the injectors associated with the combustors in the combustion section of the engine. Under certain operating conditions, such as low loads, the flow of the fuel oil to a particular combustor may be temporarily stopped. Because of the high temperatures in the combustion section of the engine, the fuel oil that may be standing in a fuel delivery tube may be significantly heated and, depending on its distance from the combustor, cause carbon deposits to form on the inside of the fuel delivery tube, thus causing flow and performance issues. Hence, during this and other system operation conditions, it is known in the art to purge the fuel delivery tubes using water so as to temporarily remove the fuel oil from the delivery tube and prevent such carbon deposits. However, known techniques for providing this water purge have certain drawbacks, such as not being able to know if a particular fuel delivery tube has a high enough flow rate of water to purge the fuel upstream from a location where the purge water is provided to the fuel delivery tube.
The present disclosure describes a fuel delivery system for a gas turbine engine that employs a technique for purging fuel oil from fuel delivery tubes in an effective manner. The fuel delivery system includes at least one multifunction valve that has a flow-through position and a bi-directional purge position, where fuel oil downstream from the valve can flow back through the valve to a drain. The fuel delivery system also includes at least one flow divider that is positioned downstream from the multifunction valve and divides the flow of fuel from the valve into a number of the fuel delivery tubes, where a separate fuel delivery tube is provided for each combustor in the engine. The flow divider acts as a pump for each of the fuel delivery tubes, which can operate in both a forward and a reverse direction. Purge water provided downstream from the flow divider for each of the fuel delivery tubes can be pumped by the flow divider when the multifunction valve is in the purge position so as to effectively purge all of the fuel delivery tubes.
Additional features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.
The following discussion of the embodiments of the invention directed to a fuel delivery system for a gas turbine engine is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. For example, as mentioned, the fuel delivery system has particular application for a gas turbine engine. However, the fuel delivery system of the invention may have application for other types of devices and power plants.
The fuel delivery system 14 receives, for example, liquid diesel fuel oil on line 40 at low pressure, which is filtered by a duplex filter assembly 42. The filtered fuel oil is then provided to a pump 44, such as a positive displacement pump, centrifugal pump, etc., operated by a motor 46 that pumps the liquid fuel oil up to a higher pressure and provides the higher pressure fuel oil on a fuel line 48. The system 14 includes a pump discharge regulator 50 that controls the pressure of the fuel oil in the line 48 from the pump 44, where the regulator 50 may draw some of the fuel oil from the line 48 into line 52 and return it to a sump (not shown) on line 54 to regulate the pressure. The flow of the fuel oil from the pump 44 in the line 48 is measured by a flow meter 56 and then sent through an emergency shut off valve 58 that can stop the flow of the fuel oil in the event of an emergency or otherwise.
The fuel oil flowing through the shut off valve 58 is then divided and sent to three separate stages 60 that provide the fuel oil flow to different locations in the combustors 30 in the engine 12, where one of the stages 60 is a pilot stage. Particularly, the fuel oil is selectively injected at one or more of three different locations in the combustor 30 in a manner well understood by those skilled in the art to provide improved combustor performance. The center stage 60 as shown in
As is well understood by those skilled in the art, the fuel oil in the tubes 82 is significantly heated by the combustion process in the combustors 30 depending on the distance from the combustor 30. As the fuel oil is being delivered to the combustor 30 for combustion therein, heating of the fuel oil in the tube 82 does not have adverse effects. However, heating of the fuel oil in the tube 82 when the combustor 30 is turned off and the fuel oil is standing therein may cause carbon deposits to form on the inside of the tube 82, which may cause the tube 82 to become clogged, thus affecting the flow rate and pressure of the fuel oil within the tube 82. Thus, for those times that the particular delivery tube 82 is not delivering fuel oil to the particular combustor 30 in the engine 12, which may occur during normal operation of the system 10, such at low loads where one or more of the stages 60 may be inactive, or at system shut down, it is necessary to selectively purge out the fuel oil from the particular tube 82 so as to prevent that fuel oil from heating and depositing carbon on the tube 82.
To perform this purge operation, it is known in the art to use the high pressure injection water available on the line 88 that otherwise would be mixed with the fuel oil as discussed above to purge out the fuel oil in the tube 84. The valve 64 can be positioned in the shut off position 68, where water injected into the tube 82 forces the fuel oil out of the tube 82 downstream of the injection junction 92 through the combustor 30. Further, it also may be desirable to purge the fuel oil out of the particular tube 82 upstream of the injection junction 92 because those areas of the tube 82 can also be subject to high temperatures.
In the known fuel delivery system designs, the flow divider 78 is positioned upstream of the multifunction valve 64 and as such, the flow delivery tubes 82 are coupled directly to the valve 64, where the purge position 76 causes the purged fuel oil to be sent to the drain 70 downstream of the flow divider 78. However, in that design, the flow of the purge water in the tubes 82 upstream of the injection junction 92 was not able to be suitably controlled, thus resulting in purge water possibly being mostly injected into the combustor 30 and not back though the valve 64. Particularly, when purging the fuel oil out of the particular tube 82 upstream of the injection junction 92, to ensure that the tube 82 is properly flushed, it often was necessary to provide a high enough pressure of the injection water that would overcome the check valve 86, which would cause a flow of water into the combustor 30 instead of back through the valve 64. Further, because the flow of the injected water upstream of the injection junction 92 was not controlled, it was not possible to know that all of the tubes 82 were being simultaneously purged during those full purge procedures. More particularly, the purge water that enters the line 88 is supplied by a manifold (not shown) that does not control the flow rate. Because there is no control for dividing the purge water, each tube 82 can receive different amounts of water, where the velocity of the water in the tube 82 is proportional to the flow rate. Since an adequate velocity of the water must be maintained to insure the oil is removed from the interior surface of the tube 82 it cannot be known if the oil has been effectively removed from the interior surface.
The present invention proposes using the flow divider 78 as a mechanism for controlling the flow of the purge water in the tubes 82 upstream of the injection junction 92. Particularly, by operating the motor 80 and the pump element 96 in the reverse direction during the water purge, it can be assured that there is enough flow in the flow delivery tubes 82 during the purge, where all of the tubes 82 can simultaneously be purged. In order to provide this control, the present invention proposes moving the flow divider 78 downstream of the multifunction valve 64 as shown in
With the control valve 62 closed, the multifunction valve 64 in the purge position 76, and the motor 80 operating at a controlled speed in the reverse direction, purge water from the line 88 flows backwards through the flow divider 78 and through the valve 64 into the drain 70, which pushes the fuel oil out of the tubes 82 and into the drain 70. Also, it is possible to split the flow at the junction 92 and simultaneously purge the particular tube 82 in both directions, i.e., to the drain 70 and out through the combustor 94, by controlling the pressure provided by the injection water on the line 88 and the speed of the motor 80 in the reverse direction. The percentage of purge water flowing to the drain 70 and through the combustor 94 can be controlled by controlling the water injection flow and the reverse speed of the motor 80. Thus, for the particular stage 60, at any given system operating condition, all of the tubes 82 for that stage can be purged as described. In this embodiment, during times of system shut off, the flow divider 78 will be full of water, instead of oil as was done in the past, which has advantages for long term life of the system.
The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/027862 | 4/28/2015 | WO | 00 |
