Patent Publication Number: US-2004050055-A1

Title: Gas turbine power augmenting spray nozzle assembly

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates generally to liquid spray nozzles, and more particularly, to spray nozzle assemblies particularly adapted for directing a fine water spray into the inlet air streams of gas powered turbines for enhanced power output.  
       BACKGROUND OF THE INVENTION  
       [0002] Gas fired turbines typically draw an air stream through a series of compressor stages that compress the air. The compressed air is directed into a combustion chamber and heated, and the rapidly expanding heated gases drive turbine blades that generate power. To enhance output power, it is known to spray fine water particles into the inlet air stream which cools the air to increase its density, and hence, enables increased subsequent gas expansion for driving the turbine blades.  
       [0003] Heretofore, existing liquid spray systems for gas turbines have been subject to a variety of design and operational problems. While it is desirable that the water spray introduced into the inlet air stream have substantially uniform small liquid particles, it has been difficult and expensive to manufacture spray nozzles which will reliably produce such spray patterns. Indeed, the discharge orifice of such nozzles must be on the order of 0.01 inch in diameter, and imperfections in the machined surfaces that define the discharge orifice can create undesirable streaking in the discharging liquid spray pattern, i.e., substantially larger, unequal liquid particles in portions of the spray pattern. Costly lapping and polishing of the machined surfaces for eliminating such surface imperfections tend to round the downstream edge or corner of the discharge orifice, which further deteriorates the desired spray performance. Since it is common to use deionized and de-chemicalized water during such spraying, over time, chemical reactions can further adversely affect metal orifice defining surfaces and the resulting liquid spray distribution. Moreover, even metal orifice defining members can be subject to extensive wear and require costly periodic replacement.  
       OBJECTS AND SUMMARY OF THE INVENTION  
       [0004] It is an object of the present invention to provide an improved spray nozzle assembly adapted for producing a discharging spray pattern of fine fog-like liquid particles within a narrow size spectrum.  
       [0005] Another object is to provide a spray nozzle assembly as characterized which is operable for more effectively enhancing the output power of gas turbines.  
       [0006] A further object is to provide a spray nozzle assembly of the foregoing type which is designed for discharging a hollow cone spray pattern and in which the discharge orifice has enhanced surface and edge characteristics.  
       [0007] Yet another object is to provide a spray nozzle assembly of the above kind which can be used over prolonged periods without deterioration of the discharge orifice-defining surfaces or edges.  
       [0008] Still a further object is to provide a spray nozzle assembly of the foregoing type which has an orifice-defining member or tip that is chemically inert to deionized or de-chemicalized liquids directed through the nozzle assembly during spraying.  
       [0009] Another object is to provide such a spray nozzle assembly in which the orifice defining member or tip is made of a hard material that resists wear, and hence, minimizes the necessity for replacement.  
       [0010] Still another object is to provide a spray nozzle assembly of the foregoing type which is adapted for economical manufacture and long term reliable usage.  
       [0011] Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012]FIG. 1 is a diagrammatic depiction of a gas-fired turbine having a power augmenting liquid spray system with spray nozzle assemblies in accordance with the present invention;  
     [0013]FIG. 2 is an enlarged longitudinal section of one of the illustrated spray nozzle assemblies, taken in the plane of line  2 - 2  in FIG. 1;  
     [0014]FIG. 3 is an enlarged longitudinal section of the illustrated spray nozzle assembly, taken in the plane of line  3 - 3  in FIG. 2;  
     [0015]FIG. 4 is a fragmentary transverse section of the illustrated spray nozzle assembly, taken in the plane of line  4 - 4  in FIG. 3;  
     [0016]FIG. 5 is an enlarged longitudinal section of an orifice defining insert member of the illustrated spray nozzle assembly; and  
     [0017]FIG. 6 is an upstream end view of the illustrated orifice defining insert member, taken in the plane of line  6 - 6  in FIG. 5. 
    
    
     [0018] While the invention is susceptible of various modifications and alternative constructions, a certain illustrative embodiment thereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention.  
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0019] Referring now more particularly to the drawings, there is shown an illustrative gas turbine  10  which includes a power augmenting liquid spray system  11  having a plurality of spray nozzle assemblies  12  in accordance with the invention disposed at an air inlet end  13  of the turbine  10 . The illustrative gas turbine  10 , which is of a known type, draws air into the inlet end  13  by means of an appropriate fan. The inlet air is compressed in a series of compressor stages  14  to pressures typically up to 40 times higher than atmospheric conditions. Following this, the highly compressed air enters a combustion chamber  15  where fuel is mixed with the air and burned. The burning fuel causes rapid expansion of gases within the combustion chamber  15 , which rotatably drives downstream turbine blades  16 , an output shaft  17  and an electrical generator  18  which generates power, that in this case is supplied to power lines  19 . It should be understood that while the spraying system  11  of the present invention is illustrated for use with a gas turbine, the spray nozzles assemblies  12  may have utility in connection with other types of turbines and in connection with other uses in which it is desired to spray a fog of fine liquid particles within a narrow spectrum of sizes.  
     [0020] To enhance gas expansion in the combustion chamber, and hence, augment output power of the turbine, the spray nozzle assemblies  12  are adapted for discharging sprays of fine fog-like liquid particles into the air stream entering the turbine  10 . The illustrated nozzles  12  are mounted on a common header or supply pipe  20  into which a liquid, preferably deionized water, is directed by a pump  21 . It will be understood that while the illustrated spraying system  11  includes a plurality of spray nozzle assemblies  12 , in some applications in which lesser amounts of liquid are required, a single spray nozzle assembly  12  may be employed. Since the nozzle assemblies  12  are identical in construction, only one need be described in detail.  
     [0021] Each spray nozzle assembly  12  comprises an elongated hollow nozzle body  24  that supports and holds a generally cylindrically configured orifice-defining insert member  25  adjacent an outwardly flared conical opening  26  in a downstream end of the nozzle body  24 . The orifice defining insert member  25  defines an elongated liquid discharge orifice  28  in axial alignment with the nozzle body opening  26  and an upstream, inwardly tapered conical whirl chamber  29  communicating with the discharge orifice  28 . The orifice insert member  25  is supported within a counter bore  30  in the nozzle body  24  and is retained therein by a back-up member  31  which is supported within an enlarged diameter cylindrical bore  32  of the nozzle body  24  and is forced against the insert member  25  by pressurized liquid directed through the nozzle assembly  12 . The back-up member  31  in this instance has a hex-shaped cross section and is supported within the bore  32  such that flat surfaces  34  of the back-up member  31  and the cylindrical bore  32  of the nozzle body define a plurality of circumferentially spaced, longitudinal liquid flow passages  35  communicating between an upstream inlet end of the nozzle body  24  and the orifice member  25 .  
     [0022] For straining liquid entering the nozzle assembly  12 , a strainer subassembly  38  is mounted on an upstream end of the nozzle body  24 . The strainer subassembly  38  includes an elongated strainer support  39  which is threadedly supported within an upstream end of the nozzle body  24  and is formed with a axial flow passage  40  communicating with the nozzle body inlet end and a plurality of radial flow passages  41  communicating with the axial passage  32 . The strainer support  39  carries a cylindrical strainer screen  42  interposed between an upstream end of the nozzle body  24  and a shoulder  43  of the support  39 . The support  39  in this case has a diagonal slot  44  in an upstream end to facilitate screwing of the support  39  into engagement with the nozzle body  24 . It will be seen that liquid directed through the header  20  will communicate through the screen  42 , the radial and axial passages  41 ,  40  of the support  39  into the nozzle body  24 , and through the longitudinal passages  35  about the back-up member  31  to the orifice defining insert member  25 .  
     [0023] For generating a hollow cone discharge spray pattern, the upstream end of the orifice-defining insert member  25  is formed with a pair of diametrically opposed cross slots  45 , which together with the downstream end of the back-up member  31  defines a pair of opposed tangential passages for directing liquid from the longitudinal passages  35  tangentially into the conical whirl chamber  29  in a swirling fashion. The swirling liquid in turn communicates through the discharge orifice  28  and out of the spray nozzle assembly  12  in a hollow cone spray pattern. As indicated previously, while it is desirable that the spray pattern be in the form of fine fog-like liquid particles in a narrow size spectrum, heretofore imperfections in the surface of the discharge orifice and the sharpness of the downstream corner or annular edge  46  of the discharge orifice  28  can create undesirable streaking in the discharging spray. Prior orifice-defining members, furthermore, have been susceptible to excessive wear which can further deteriorated spray performance and necessitated periodic replacement.  
     [0024] In accordance with the invention, the orifice-defining member is made of a corundum material having a hardness of about 9 MOHS, and the discharge orifice is defined by precision surfaces and edges such that the discharging hollow cone spray pattern has fine liquid particles within a narrow spectrum of sizes. Preferably, the orifice member is made of a synthetic corundum, typically synthetic sapphire or ruby, which has a surface hardness of 9 MOHS and which permits precision formation of the discharge orifice and resists wear and chemical degradation. Synthetic sapphire and ruby gemstones of such type, which are commercially available, have a hardness of 9 MOHS. One commercially available synthetic sapphire has the following further properties.  
                                                      Chemical Composition   Al 2 0 3             Physical properties           Crystal structure   Hexagonal rhombohedral           Specific gravity   3.99 ÷ 3.98           Thermal properties           Melting point   2050° C.           Thermal expansion   5.4 − 10 6 /° C. face perp. C axis               6.2 − 10 6 /° C. face parall. C axis           Mechanical properties           Hardness mohs   9           knoop   1800 face perp. C axis               2200 face parall. C axis           Modulus of elasticity   4.4 × 10 6  kg/cm 2 / ± 1% young               E.           Chemical properties           Acids and alkalis attack   0 at 300° C.           Porosity   0           Electrical properties           Dielectric constant   9.4 at 11.3           Electrical resistance   10 11  ohm/cm at 500° C.               10 6  ohm/cm at 1000° C.               10 3  ohm/cm at 2000° C.                      
 
     [0025] The cylindrical discharge orifice  28  may be formed with precision smoothness and a sharp corner or edge  46  at the downstream end which facilitates the generation and direction of a fine liquid particle spray pattern without undesirable streaking, typical of conventional machined metal orifice defining members.  
     [0026] It will be appreciated by one skilled in the art that unlike synthetic diamond gemstones, sapphire and ruby gemstones can be economically processed and manufactured with precision surfaces and edges by economical, known processing techniques. Such gemstones, furthermore, are free from acidic and alkali attack at temperatures up to 300° C. and have a porosity of 0. It has been unexpectedly found that orifice members manufactured by such gemstones may be formed with discharge orifices, on the order of 0.01 inch, with substantially imperfection-free surfaces and edge characteristics for enhanced fine liquid particle discharge. Spray nozzles with such orifice members are effective for discharging a consistent fine liquid spray. Indeed, the spray nozzle assemblies of the present invention have particular utility for directing liquid sprays into the inlet air streams of gas fired turbines for enhanced power augmentation. The sapphire and ruby gemstone material further is resistant to chemical attack from deionized water used in such gas turbine liquid spray systems and is substantially more resistant to wear than metal.  
     [0027] From the foregoing, it can be seen that the spray nozzle assembly of the present invention is adapted for producing a fine fog-like hollow cone liquid spray pattern with a narrow sized spectrum of liquid particles for more effectively enhancing the output power of gas turbines. The orifice defining insert members, furthermore, are adapted for prolonged usage without deterioration of the discharge orifice-defining surfaces and edges which reduces the necessity for replacement.