Abstract:
A device and method for cleaning a surface using dry steam is disclosed. A dry steam wand is fitted with a custom nozzle that permits the dry steam to be angled to clean difficult to access surfaces of a gas turbine. The nozzle includes a slit that is configured to maintain sufficient temperature and pressure to effectively remove contaminants found on gas turbines.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to cleaning surfaces, including internal surfaces of gas turbines. 
         [0002]    During operation of certain gas turbines, contaminants are often pulled into the turbine through inlets and may accumulate in internal, difficult to access places, such as rotors, compressors, lower and upper half shells and the like. Additionally, combustion byproducts of the consumed fuel may also accumulate in these places. Contaminants may negatively impact the efficiency of the turbine. 
         [0003]    To maximize the efficiency of the turbine, it is desirable to periodically clean the internal, difficult to access places of the turbine. As cleaning necessarily results in downtime as the turbine is taken offline, it is desirable to minimize downtime by rapidly, yet thoroughly, cleaning the turbine. 
         [0004]    Conventional cleaning techniques include hand-cleaning, dry ice cleaning and cleaning with wet steam. Hand-cleaning is the most common technique, but also the least effective. A significant amount of contaminants often remain in the difficult to access places. Dry ice cleaning is more effective than hand-cleaning but requires the use of several thousand pounds of dry ice be consumed. The logistics of keeping such a large amount of dry ice is problematic due to constant sublimation and large storage space. Wet steam cleaning is also more effective than hand-cleaning, but produces many gallons of waste water. The removal of such a large volume of waste water is a significant problem as the water is slow to evaporate. 
         [0005]    The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    A device and method for cleaning a surface using dry steam is disclosed. A dry steam wand is fitted with a custom nozzle that permits the dry steam to be angled to clean difficult to access surfaces of a gas turbine. The nozzle includes a slit that is configured to maintain sufficient temperature and pressure to effectively remove contaminants found on gas turbines. An advantage that may be realized in the practice of some disclosed embodiments of the nozzle is that gas turbine contaminants may be efficiently removed from difficult to access surfaces. Conventional nozzles were found to be ineffective for such an application. 
         [0007]    In one embodiment, a method of cleaning a surface is disclosed. The method comprises conducting dry steam through a wand, and directing the dry steam at an acute angle relative to a longitudinal axis of the wand to clean the surface. 
         [0008]    In another embodiment, a method of cleaning an internal surface of a gas turbine is disclosed. The method comprises conducting dry steam through a wand, directing, with a nozzle fluidly connected to the wand, the dry steam at an acute angle relative to a longitudinal axis of the wand to clean the surface, and positioning the nozzle proximate to the internal surface to maintain a temperature of greater than 350 degrees C. at the internal surface. 
         [0009]    In yet another embodiment, a nozzle for a dry steam cleaner is disclosed. The nozzle comprises a cavity having a central longitudinal axis, and a slit in the nozzle that is spaced apart from the central longitudinal axis and accesses the cavity. 
         [0010]    This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which: 
           [0012]      FIG. 1  depicts an exemplary system for dry steam cleaning a surface; 
           [0013]      FIG. 2  is a flow diagram of an exemplary method for cleaning a surface. 
           [0014]      FIG. 3  is a perspective view of an exemplary nozzle for a dry steam cleaner; 
           [0015]      FIG. 4  is a side view of the nozzle of  FIG. 3 ; 
           [0016]      FIG. 5  is a front view of the nozzle of  FIG. 3 ; 
           [0017]      FIG. 6  is a top view of the nozzle of  FIG. 3 ; 
           [0018]      FIG. 7  is a bottom view of the nozzle of  FIG. 3 ; 
           [0019]      FIG. 8  is a side view of the nozzle of  FIG. 3  showing certain parameters; and 
           [0020]      FIG. 9  is a top view of the nozzle of  FIG. 3  showing a dovetail pattern of dry steam. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Disclosed in this specification is a method and device for cleaning a surface using dry steam. Dry steam is a term of art that refers to steam with a low (e.g., less than about 3%) moisture content. The method uses a specially designed nozzle to deliver dry steam to a surface for the purpose of removing contaminants deposited thereon. The nozzle permits the dry steam to be delivered at a certain pressure (e.g., greater than about 160 pounds per square inch (psi) or 1103 kPa (kilopascals)) and at a certain temperature (e.g., greater than about 350° C.). Conventional nozzles are unable to achieve these pressures and temperatures. The method and device are particularly suitable for cleaning internal surfaces of gas turbines. 
         [0022]      FIG. 1  depicts an exemplary system  100  for dry steam cleaning a surface. The system  100  comprises a dry steam boiler  102  for producing dry steam. Such dry steam boilers are commercially available. An elongated wand  104  is in fluid communication with the dry steam boiler  102  by a hose  106 , the elongated wand  104  having a longitudinal axis  108 . A nozzle  110  is connected to the wand  104 . The nozzle  110  has a slit (not shown) that directs dry steam at an angle  112  relative to the longitudinal axis  108  of the wand  104 .  FIG. 1  also depicts a pair of substrates  114 ,  116  separated by a narrow gap  118 . In use, the nozzle  110  may be inserted into the narrow gap  118 . Since the dry steam is directed at an angle  112 , difficult to access surfaces (e.g.,  115 ,  117 ) may be cleaned. The nozzle  110  permits the dry steam to be delivered at a certain pressure (e.g., greater than about 160 pounds per square inch (psi) or 1103 kPa (kilopascals))) and at a certain temperature (e.g. greater than about 350° C.). Conventional nozzles have openings that do not satisfy the parameters discussed in this specification and proved to be ineffective for this purpose as the proper temperature and pressure could not be maintained. The nozzle  110  may be formed of any suitable material including, but not limited to, metals such as stainless steel. 
         [0023]      FIG. 2  is a flow diagram of an exemplary method  200  for cleaning a surface. In one embodiment, the surface is an internal surface of a gas turbine. Examples of internal surfaces include rotors, compressors, lower and upper half shells, etc. The method  200  comprises a step  202  of obtaining a baseline measurement of the amount of contaminants on a surface of a substrate. For example, the thickness of the surface may be measured using a caliper or other suitable measuring device. The thickness includes the thickness of both the substrate and the contaminants. The method  200  also comprises a step  204  of providing dry steam from a dry steam boiler. In step  206 , the dry steam is conducted into a wand through a hose. The wand has a longitudinal axis and a nozzle, such as nozzle  300  of  FIG. 3 , at a terminal end of the wand that directs the dry steam. In step  208 , the dry steam is directed by the nozzle at an acute angle relative to the longitudinal axis of the wand. In step  210 , the nozzle is positioned proximate the surface to be cleaned. In one embodiment, the nozzle is positioned within one inch (2.54 cm) of the surface to be cleaned. In step  212  a new measurement of the amount of contaminants on the surface is obtained. The new measurement may be compared to the baseline measurement to provide a quantitative indication of the success of the cleaning method. 
         [0024]      FIGS. 3-7  are various views of an exemplary nozzle  300  for a dry steam cleaner. The nozzle  300  has a cavity  302  that is defined by at least one sidewall  304 , an open bottom face  306  and a top face  308 . The inner surface of the cavity  302  has threads  303  for connecting to a wand (not shown). The cavity  302  defines a central longitudinal axis  310 . The nozzle  300  has a slit  312  that is spaced from the central longitudinal axis  310  and fluidly connects to the cavity  302 . In this fashion, dry steam that is introduced to the cavity  302  exits the slit  312  and is directed toward a surface to be cleaned. In the embodiment of  FIG. 7 , the nozzle  300  comprises six flat sidewalls disposed at angles to provide a hexagonal nozzle and is well suited for use with a wrench. In alternate embodiments, more or fewer sidewalls may be present to provide nozzles with other shapes. For example, a single sidewall that is curved may be present to provide a cylindrical nozzle. The exemplary nozzle  300  is shown wherein the slit  312  has an opening  313  at an interface  315  formed by the sidewall  304  and the top face  308 . In alternate embodiments, the slit opens on the sidewall. 
         [0025]    In the embodiment of  FIG. 8 , the slit  312  is spaced apart from the central longitudinal axis  310  by a distance  314 . The slit  312  forms an angle  316  with the central longitudinal axis. In one embodiment, the angle  316  is an acute angle. In another embodiment, the angle  316  is between about thirty-five and fifty-five degrees. In the exemplary embodiment of  FIG. 8 , the angle  316  is about forty-five degrees. 
         [0026]    The slit  312  has a depth  318  of between about 20% and 50% of a nozzle width  320  of the nozzle  300  such that the slit  312  extends into the sidewall  104 . For example, the nozzle width  320  may be 0.625 inches (15.9 mm) and the depth  318  may be about 0.25 inches (6.4 mm), which is approximately 40% of the nozzle width  320 . The slit has a slit width  322  that is between about 15% and about 30% of the depth  318 . For example, when the depth  318  is about 0.25 inches (6.4 mm) the slit width  322  may be about 0.063 inches (1.6 mm, 25%). By way of further example, when the depth  318  is about 0.25 inches (6.4 mm) the slit width  322  may be about 0.045 inches (1.1 mm, 18%). The slit  312  has a length  326  (see  FIG. 5 ) that traverses at least 50% of the nozzle width  320 . As shown in  FIG. 9 , the slit  312  is configured to project dry steam in a dovetail pattern  324 . The dovetail pattern  324  exposes a relatively wide area of the surface to be cleaned to the dry steam. 
         [0027]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.