Abstract:
The invention relates generally to gas turbine engines used for electrical power generation. More specifically, embodiments of the present invention provide ways for improving gas turbine engine performance by reducing ice build-up on the inlet filter housing through heated air injection.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 62/207,209 filed on Aug. 19, 2015, which is herein incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates generally to electrical power systems, including generating capacity of a gas turbine, and more specifically to a system and method for reducing ice presence at an inlet filter housing of a gas turbine engine. 
       BACKGROUND OF THE INVENTION 
       [0003]    Gas turbine engines are commonly used in land-based power plants for generating electricity. These land-based power plants take atmospheric air, increase its pressure through a compression process, mix fuel with the compressed air and ignite the mixture to generate hot combustion gases which drive a turbine coupled to the compression system. The mechanical work from the gas turbine engine is used to drive a generator for producing electricity. The exhaust from the gas turbine engine can also be used for producing steam in a combined cycle operation. A representative gas turbine engine is shown in  FIG. 1 . 
         [0004]    The atmospheric air for use in the gas turbine engine  100  is first drawn into an inlet filter housing  102 , which is typically elevated above ground level, as shown in  FIG. 1 . The inlet filter housing  102  is elevated to help reduce dirt and debris from being drawn into the gas turbine engine  100 . Furthermore, the inlet filter housing  102  provides a clean and steady air flow to the gas turbine engine  100 . These housings contain filters (not shown) which clean the incoming air flow of any dirt, debris or other objects which could damage the gas turbine engine  100 . 
         [0005]    Unfortunately, many inlet filter housings  102  experience icing on the filters when operating near or below freezing temperatures. Presently, there is no solution to this problem. Icing can also occur due to the freezing of water vapor from nearby power plant cooling towers (not shown). To reduce this tendency, power plant designers have often positioned cooling towers downwind of the inlet filter housing  102 , based on the prevailing wind direction, so as to reduce the likelihood of water vapors entering the inlet filter housing and freezing. However, icing on the inlet filter housing during engine operation continues to occur, resulting in ice build-up which creates an excessive pressure drop across the filters due to the blockage in the inlet area. Gas turbine engine control equipment is used to monitor the inlet filter pressure drop as catastrophic structural failure can occur if the pressure drop is too large. 
         [0006]    As will be discussed in more detail below, many gas turbine engines use an inlet bleed heat system  110  to help improve engine performance by taking a small portion of heated compressed air from the compressor discharge plenum  112  and directing the heated air through pipes  114  and injecting the heated air into an inlet air system  116  upstream of the engine compressor  118 . Injecting heated air through injection tubes  124  helps to raise the temperature of the air entering the compressor  118 , but there is a corresponding power loss from the gas turbine engine  100 , when working fluid is withdrawn from the compressor discharge plenum  112 . 
       SUMMARY 
       [0007]    The present invention relates to systems and methods for improving the performance of the gas turbine engine by reducing icing at the gas turbine engine inlet. In an embodiment of the present invention, a gas turbine engine is provided comprising an inlet filter housing, an inlet air system coupled thereto, a compressor in fluid communication with the inlet air system, a compressor discharge plenum in communication with the compressor, an inlet bleed heat system in fluid communication with the inlet air system, the compressor discharge plenum, and an auxiliary source of compressed air. Heated air is capable of being directed to the inlet filter housing to raise its operating temperature and thereby reduce ice formation on the air filters and housing. 
         [0008]    In an alternate embodiment of the present invention, a power augmentation and deicing system is provided comprising an inlet filter housing, an inlet air system coupled thereto, a compressor in fluid communication with the inlet air system, a compressor discharge plenum in communication with the compressor, an auxiliary source of compressed air external to a gas turbine engine system, and a plurality of feed pipes and control valves selectively connecting the compressor discharge plenum, the auxiliary source of compressed air, the inlet air system and the inlet filter housing. 
         [0009]    In another embodiment of the present invention, a gas turbine deicing system is provided comprising a first series of air pipes in communication with a compressor discharge plenum where the first series of pipes have an isolation valve. A second series of pipes, which include a deicing valve, are in communication with the first series of air pipes such upon opening of the isolation valve and the deicing valve, air from the compressor discharge plenum is directed to the inlet filter housing for heating the inlet filter housing. 
         [0010]    In yet another embodiment of the present invention, a method of reducing ice build-up on an inlet filter housing of a gas turbine engine is provided. The method comprises producing a supply of heated air through an auxiliary source external to the gas turbine engine and flowing the supply of heated air through a plurality of feed pipes and towards the inlet filter housing. The flow of heated air is then divided into injection tubes proximate the inlet filter housing and the heated air is injected into the inlet filter housing. 
         [0011]    Other advantages, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure and the combination of parts will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    The present invention is described in detail below with reference to the attached drawing figures, wherein: 
           [0013]      FIG. 1  is a schematic drawing of a gas turbine engine in accordance with the prior art. 
           [0014]      FIG. 2  is a power augmentation and deicing system for a gas turbine engine in accordance with an embodiment of the present invention. 
           [0015]      FIG. 3  is a power augmentation and deicing system for a gas turbine engine in accordance with an alternate embodiment of the present invention. 
           [0016]      FIG. 4  is a detailed view of a portion of the power augmentation and deicing system for a gas turbine engine in accordance with the embodiment of the present invention of  FIG. 3 . 
           [0017]      FIG. 5  is a flow chart depicting yet another alternate embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Embodiments of the present invention are described below with respect to  FIGS. 2-5 . Referring initially to  FIG. 2 , a gas turbine engine  200  is provided comprising an inlet filter housing  202 , an inlet air system  204  in fluid communication with the inlet filter housing  202 . The inlet air system  204  directs an incoming airflow  206  from the inlet filter housing  202  to the compressor  208 . The gas turbine engine  200  also comprises a compressor discharge plenum  210  which is in fluid communication with the compressor  208 . The compressor discharge plenum  210  provides a large volume in which the compressed air from the compressor  208  is directed prior to entering one or more combustors (not shown). Compressed air from the compressor discharge plenum  210  can be withdrawn and used for cooling a turbine  212  or for a variety of other applications. 
         [0019]    One such application to which air from the compressor discharge plenum  210  can be used is for an inlet bleed heat system  220 , which preheats air prior to entering the compressor  208 . The inlet bleed heat system  220  is in fluid communication with the inlet air system  204  and the compressor discharge plenum  210  through a first series of air pipes  222  and an inlet bleed heat control valve  224 . In this operation, when it is desirable for compressor discharge air to be used for inlet bleed heating to raise the temperature of air to the compressor  208 , the inlet bleed heat valve  224  and isolation valve  226  are opened, permitting a portion of the air from the compressor discharge plenum  210  to be directed through the first series of pipes  222  and to a series of air injection pipes  228 , where the air is injected into the inlet air system  204 . In this configuration, a portion of the approximately 600-800 degree Fahrenheit compressor discharge air is directed to upstream of the compressor  208 . 
         [0020]    Another application to which air from the compressor discharge plenum  210  can be utilized is to flow to the inlet filter housing  202  to aid in deicing the inlet filter housing  202  by raising the operating temperature of the inlet filter housing  202 . In this embodiment of the present invention, compressed air from the compressor discharge plenum  210  flows through an open isolation valve  226 , through a portion of the first series of air pipes  222  and into a second series of air pipes  230 , and through an open deicing valve  232  to the inlet filter housing  202 . In this embodiment, a portion of the approximately 600-800 degree Fahrenheit compressor discharge air is directed to the inlet filter housing  202  in order to raise its operating temperature and prevent ice formation. However, as discussed above with respect to inlet bleed heat systems, air taken from the compressor discharge plenum  210  for the inlet filter housing  202  draws working fluid out of the gas turbine engine  200 , thus reducing its overall power output. 
         [0021]    The present invention also provides an improved way of providing the necessary preheating without performance reduction through an auxiliary source of compressed air  240 . Heated air is generated external to the engine and directed to the inlet filter housing  202  to raise its operating temperature and reduce ice formation in the inlet filter housing  202 . 
         [0022]    In one embodiment of the present invention, an auxiliary source of compressed air  240  can be provided to the gas turbine engine  200 . The auxiliary source of compressed air  240  provides heated air at a temperature of approximately 500-700 degrees Fahrenheit to the engine  200  without adversely affecting engine performance since it is not taken from elsewhere in the engine. Flow of the auxiliary source of compressed air  240  to the gas turbine engine is regulated by an auxiliary control valve  242 . 
         [0023]    The auxiliary source of compressed air  240  can be supplied to the inlet filter housing  202  as a source of heated air to raise its operating temperature and prevent ice formation at the inlet filter housing  202 . In this embodiment, the isolation valve  226  may be open or closed, and while the inlet bleed heat valve  224  remains closed while the auxiliary control valve  242  and deicing valve  232  are open, such that heated air from the auxiliary source of compressed air  240  flows through at least the second series of pipes  230  and into the inlet filter housing  202 . 
         [0024]    The auxiliary source of compressed air  240  can take on a variety of embodiments, such as an auxiliary supply tank or separate generating body. One such separate generating body is a separate compressed air source  250 , as depicted in  FIG. 3 . An acceptable option for the separate compressed air source  250 , is one or more TurboPHASE™ units, a commercial air injection unit provided by PowerPHASE of Jupiter, Fla., an embodiment of which is disclosed in U.S. Pat. No. 9,388,737. 
         [0025]    In this embodiment of the present invention, a fueled engine  252  receives air  254  and fuel  256  to operate the fueled engine  252  and generate mechanical output in the form of power to shaft  258  and heated exhaust  260 . As used herein, the term “fueled engine” means a heat engine, such as a piston driven or rotary (e.g. Wankel) internal combustion engine (e.g. gasoline engine, diesel engine, natural gas fired engine, or similar fuels, or a combination of such fuels) or a gas turbine, that produces work by combusting a fuel with air to heat a working fluid which then drives blades or the like. The shaft  258  turns a mutli-stage auxiliary compressor  262  which compresses the air, and as a result, also raises the air temperature. Depending on the configuration of the separate compressed air source, the compressor  262  may be an intercooled compressor, where the air is cooled between each stage of the compressor, thereby allowing for further compression of the air over more typical compression systems. According to one embodiment, the auxiliary compressor  262  is a multistage compressor having at least one upstream compression stage and at least one downstream compression stage fluidly downstream of the upstream compression stage, and the step of operating the fueled engine to drive the auxiliary compressor to produce compressed air from the auxiliary compressor includes the step of cooling the compressed air exiting the upstream compression stage before delivering it to the downstream compression stage. Preferably, the apparatus further comprises an intercooler heat exchanger fluidly connected to at least one of the stage inlets and at least one of the stage outlets to cool the compressed air exiting the at least one of the stage outlets prior to delivering the compressed air to the at least one of the stage inlets downstream thereof. 
         [0026]    Air  264  from the compressor  262  is then directed to a recuperator  266  where it is heated with exhaust heat  260  from the fueled engine  252 . Waste heat  268  from the recuperator  266  is discharged to the atmosphere while the heated compressed air  270  is ready to be used in the gas turbine engine  200 . As discussed above, the heated compressed air  270  forms the auxiliary source of compressed air  240  which is directed through the second series of air pipes  230  and to the inlet filter housing  202  for deicing of the inlet filter housing  202 . 
         [0027]    In yet another embodiment of the present invention, the heated compressed air  270  from the separate compressed air source  250  can be used as a source of inlet bleed heat by directing the heated compressed air  270  through an open auxiliary control valve  242 , through the first series of pipes  222  and through an open inlet bleed heat control valve  224  and to the series of air injection pipes  228 . 
         [0028]    Referring now to  FIG. 4 , further details of the way the heated air is injected into the inlet filter housing  202  is depicted. Atmospheric air  206  is drawn into the inlet filter housing  202  through a plurality of openings. When a predetermined pressure drop occurs in the inlet filter housing  202 , indicating icing of the inlet filters, the deicing system of the present invention is activated. Heated compressed air is passed through the second series of pipes  230  and to a plurality of injector pipes  234  proximate the openings to the filter housing  202 . The exact quantity of injector pipes  234  can vary depending on the inlet configuration of the gas turbine engine. For the embodiment shown in  FIG. 4 , multiple rows of injector holes are positioned within each injector pipe  234  for injecting the heated compressed air into the inlet filter housing  202 . However, as with the quantity of pipes  234 , the quantity of holes, spacing, and orientation can vary depending on the engine configuration and inlet filter housing heating requirements. It is preferred that the heated air being injected in a way to raise the temperature of the inlet housing uniformly. Alternatively, heated air can be targeted to specific areas of the inlet know for ice build-up through injection hole location, size, and injection angle. 
         [0029]    Referring now to  FIG. 5 , a method of reducing ice build-up on an inlet filter housing of a gas turbine engine is depicted. In this alternate embodiment of the present invention, the method  500  comprises, in a step  502 , producing a supply of heated air through an auxiliary source that is external to the gas turbine engine. Then, in a step  504 , the supply of heated air generated in step  502  is flowed through one or more feed pipes and towards the inlet filter housing. In a step  506 , the heated air is divided into injection tubes proximate the inlet filter housing. As discussed above, the exact quantity of injection tubes can vary as required in order to provide the required amount of heated air to the inlet filter housing to reduce the tendency for ice build-up. Then, in a step  508 , the supply of heated air is injected into the inlet filter housing. A series of control valves are operated by a control system to regulate the source of heated air as well as volume of heated air being injected into the inlet filter housing. 
         [0030]    As those skilled in the art will readily appreciate, each of the embodiments of the present invention includes flow control valves, backflow prevention valves, and shut-off valves as required to insure that the flow of air, auxiliary compressed air, and compressor discharge air flow only in the directions described herein. While the particular systems, components, methods, and devices described herein and described in detail are fully capable of attaining the above-described objects and advantages of the invention, it is to be understood that these are but embodiments of the invention and are thus representative of the subject matter which is broadly contemplated by the present invention. The scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims. It will be appreciated that modifications and variations of the invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.