Abstract:
A multiple-passage turbine nozzle with desired predetermined flow properties may be provided with an adjustment member in one or more of its passages to limit the flow therethrough. Turbine nozzle flow is an important performance characteristic that may be difficult to control by conventional drilling or machining manufacturing methods. The adjustment member may protrude into a nozzle passage, thereby reducing airflow through the nozzle passage. The amount of protrusion is variable and is selected to provide a desired partial or total occlusion of an associated passage at the time of manufacture of the turbine nozzle to compensate for variations produced by the conventional manufacturing techniques. The turbine nozzle according to the present invention provides simple and convenient calibrated adjustment of the predetermined flow that may be allowed to pass through a turbine nozzle onto a turbine wheel of a turbo machine.

Description:
BACKGROUND OF THE INVENTION 
   The present invention generally relates to turbine nozzles and, more particularly, to variably adjustable flow turbine nozzles. 
   In an air cycle machine or other turbomachinery, a turbine may include a turbine nozzle at the turbine inlet that may channel the combustion gases between the turbine rotor blades that extract energy therefrom for powering the compressor. 
   Turbine nozzle flow is an important performance characteristic in most turbomachinery and specifically in an air cycle machine. It is difficult to manufacture drilled or machined nozzles that have small nozzle-to-nozzle variation. This difficulty results in significant rework and/or expensive manufacturing processes. Conventional turbine nozzles may be manufactured by first drilling or machining the nozzle flow passages, measuring the nozzle flow and adjusting the nozzle flow by extrude honing. A typical extrude honing process may, for example, pump clay and abrasive through the nozzle passageways to make the passages larger in size, thereby increasing nozzle flow. The airflow measurement step and the airflow adjustment step are repeated until the desired nozzle flow is achieved. Typically, nozzle flow must be controlled to within about +/−1%. 
   A variable geometry turbine has been disclosed in U.S. Pat. No. 6,652,224. The turbine described in the &#39;224 patent has nozzle vanes that are displaceable across the turbine inlet flow path into slots. The vanes have cut-outs which reduce the vane cord and permit peak turbine efficiency over a range of geometries. Nozzle flow may be adjusted by controlling the axial position of a nozzle ring. Unfortunately, additional components, such as axially extending pins and stirrup members may be necessary to control the nozzle ring&#39;s axial position (col. 4, lines 1–17). 
   As can be seen, there is a need for an improved turbine nozzle and method for adjusting the flow through the turbine nozzle. 
   SUMMARY OF THE INVENTION 
   In one aspect of the present invention, a turbine nozzle comprises a plurality of nozzle passages; and at least one flow adjustment member in at least one of the plurality of nozzle passages, the flow adjustment member capable of providing an adjustable airflow through the turbine nozzle. 
   In another aspect of the present invention, an adjustable flow turbine nozzle for regulating airflow to a turbine wheel of a turbo machine comprises a plurality of nozzle passages; and a flow adjustment member in each of at least two of the nozzle passages, the flow adjustment member capable of providing an adjustable airflow through the turbine nozzle, the at least two of the nozzle passages being equally spaced about the adjustable flow turbine nozzle. 
   In still another aspect of the present invention, a drilled adjustable flow turbine nozzle comprises about 20 to about 60 nozzle passages; at least one flow adjustment member in at least one of the nozzle passages, each flow adjustment member capable of providing an adjustable airflow through the drilled adjustable flow turbine nozzle; and a cross-drilled hole in the drilled adjustable flow turbine nozzle, the hole communicating an exterior of the drilled adjustable flow turbine nozzle with one of the nozzle passages, the hole capable of receiving the flow adjustment member, wherein the hole forms an angle with the nozzle passage to which it communicates of less than 90 degrees. 
   In yet another aspect of the present invention, a vaned adjustable flow turbine nozzle comprises about 20 to about 60 nozzle passages formed as vanes on a surface of the vaned adjustable flow turbine nozzle; and at least one flow adjustment member in at least one of the vanes, each flow adjustment member capable of providing an adjustable airflow through the vaned adjustable flow turbine nozzle. 
   In another aspect of the present invention, a turbo-machine comprises a compressor wheel; a turbine wheel; a shaft rotationally connecting the compressor wheel with the turbine wheel; and a turbine nozzle for directing an airflow on the turbine wheel, the turbine nozzle having a plurality of nozzle passages and at least one flow adjustment member in at least one of the plurality of nozzle passages, each flow adjustment member capable of providing an adjustable airflow through the turbine nozzle 
   In a further aspect of the present invention, a method for regulating airflow onto a turbine wheel of a turbo machine comprises passing the airflow through a turbine nozzle to provide a regulated airflow, the turbine nozzle having a plurality of nozzle passages and at least one flow adjustment member in at least one of the plurality of nozzle passages, the flow adjustment member capable of providing an adjustable airflow through the turbine nozzle; and directing the regulated air to contact the turbine wheel. 
   These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of an air cycle machine having a turbine nozzle according to an embodiment of the present invention; 
       FIG. 2  is a sectional view of a drilled turbine nozzle according to an embodiment of the present invention; and 
       FIG. 3  is a sectional view of a vaned turbine nozzle according to another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
   The present invention generally provides an adjustable flow turbine nozzle having at least one flow adjustment member for providing a regulated airflow therethrough. The present invention further provides a method for regulating airflow onto a turbine wheel of a turbo machine by providing at least one flow adjustment member in a turbine nozzle airflow path. The turbine nozzle may be a drilled nozzle, having air passages drilled therethrough. Alternatively, the turbine nozzle may be a vaned nozzle, having vanes therein for directing airflow. The adjustable flow turbine nozzle may be useful on any turbine machine, including an air cycle machine and a gas turbine engine. 
   Unlike conventional turbine nozzles that may rely on accurate machining and/or drilling for proper airflow, the adjustable flow turbine nozzle of the present may use one or more flow adjustment members, such as an adjustment screw, to regulate the air flow through the turbine nozzle. Thus, airflow may be adjusted simply, without requiring additional reworking of the turbine nozzle. 
   Referring to  FIG. 1  there is shown a schematic drawing of an air cycle machine  10  in which the present invention may be employed. The usual compression cooling and expansion seen in any refrigeration cycle may be accomplished in the air cycle machine  10  by a compressor  12 , an exchanger  14 , and an expansion turbine  16 . The work extracted by the expansion turbine  16  may be transmitted by a shaft  18  to the compressor  12 . An adjustable flow turbine nozzle  20 , as described in greater detail below with reference to  FIGS. 2 and 3 , may be located in airflow path  22  to channel air at the appropriate angle and flow volume/speed onto the expansion turbine  16 . The particular angle and flow volume/speed of the airflow may vary with the size of the turbo machine (in this case, the air cycle machine  10 ), type of turbo machine, and the like. 
   While  FIG. 1  describes the adjustable flow turbine nozzle  20  of the present invention used in the air cycle machine  10 , the invention is not meant to be so limited. The adjustable flow turbine nozzle  20  may be useful in any turbo machine, including gas turbine engines, gas turbine generators, and the like. 
   Referring to  FIG. 2 , there is shown a sectional view of a segment of a drilled adjustable flow turbine nozzle  20   a , according to one embodiment of the present invention. As discussed above, conventional drilled turbine nozzles may have a nozzle passage drilled therethrough which is brought to the correct size via an extrude honing process with, for example, clay and abrasive. This conventional process may be used to control the nozzle flow to be within the required +/−1%. This conventional process, however, requires significant rework and/or expensive manufacturing processes. 
   The drilled adjustable flow turbine nozzle  20   a , according to one embodiment of the present invention, may have a plurality (typically from about 20 to about 60, more typically from about 40 to about 55) of nozzle passages  24  cut therethrough. The nozzle passages  24  may be formed in a single row or may be formed in multiple rows in drilled adjustable flow turbine nozzle  20   a . The nozzle passages  24  may have an inlet diameter d 2  that is between about 2 to about 4 times, typically between about 2 to about 3 times, an outlet diameter d 1  as shown in  FIG. 2 . Outlet diameter d 1  may vary depending on the application of the turbo machine. In the case of the air cycle machine  10  described in  FIG. 1 , outlet diameter d 1  may range between about 1/16 to about ½ inch, typically between about ⅛ to about ¼ inch. 
   At least one of the nozzle passages  24  may have a flow adjustment member  26 , which may adjustably or controllably protrude therein to disrupt the flow of air therethrough. The flow adjustment member  26  may be, for example, a plug-like member adapted for controllable protrusion into at least one of the nozzle passages  24 . The flow adjustment member  26  may partially occlude at least one of the nozzle passages  24 . The flow adjustment member  26  may be disposed in the drilled adjustable flow turbine nozzle  20   a  by any conventional means, for example, by cross-drilling a hole  28  in the drilled adjustable flow turbine nozzle  20   a  to communicate an exterior  44  of drilled adjustable flow turbine nozzle  20   a  with one of the nozzle passages  24 . The flow adjustment member  26  may fit into the hole  28  by friction fit, or, alternatively, the flow adjustment member  26  and the hole  28  may be formed with mating male threads  40  and female threads  42 , respectively. 
   In the case where the flow adjustment member  26  and the hole  28  are threaded, a thread locking means, such as Spiroloc® or a thread locking compound may be used to prevent unintentional adjustment of the flow adjustment member  26 . 
   The flow adjustment member  26  can vary a single nozzle passage  24  from completely closed to fully open. In the example of a 50-hole nozzle, a single flow adjustment member  26  may therefore allow for a total flow adjustment of two percent. In order to maintain an even flow of air through the drilled adjustable flow turbine nozzle  20   a , thereby reducing blade vibrations, a plurality of flow adjustment members  26  may be evenly spaced circumferentially in a corresponding plurality of nozzle passages  24  of the drilled adjustable flow turbine nozzle  20   a . For example, if a 2% reduction in flow is desired in a 50-hole nozzle, four flow adjustment members  26  may be placed at 90 degree intervals around the drilled adjustable flow turbine nozzle  20   a , each of the four flow adjustment members  26  reducing the flow through their respective nozzle passages  24  by 25%. In other words, a desired calibration of one of the turbine nozzles  20   a  a may achieved by providing adjustment members  26  for only about 8% to about 10% of the nozzle passages  24 . If a total occlusion of one or more of the nozzle passages  24  is performed, then a desired 2% calibration can be accomplished by providing adjustment members  26  for only 2% of a total number of the nozzle passages. 
   The hole  28  may be drilled at an angle θ with respect to a central axis  38  of the nozzle passage  24 . The angle θ may be less than 90 degrees, typically less than about 70 degrees, in order to reduce flow disturbances through the nozzle passage  24 . To further reduce flow disturbances through the nozzle passage  24 , the flow adjustment member  26  may have a radius r at its leading end  30 . The flow adjustment member  26  may be tapered at leading end  30 , as shown in  FIG. 2 , or the flow adjustment member  26  may have a uniform radius r along its entire length L. 
   The flow adjustment member  26  may be made of a material having the same hardness as the material of the drilled adjustable flow turbine nozzle  20   a , thereby preventing erosion over time. The flow adjustment member  26  and the drilled adjustable flow turbine nozzle  20   a  may be composed of, for example, chromium nickel alloy, moly-chrome nickel steel, a Nimonic® alloy, or the like. 
   Referring now to  FIG. 3 , there is shown a sectional view of a vaned adjustable flow turbine nozzle  20   b  according to another embodiment of the present invention. A flow adjustment member  26   b  may be placed at a throat  32  of a nozzle passage  24   b  to reduce the flow area between vanes  34  of vaned adjustable flow turbine nozzle  20   b . The flow adjustment member  26   b  may function in a manner similar to that of flow adjustment member  26  as described above in reference to  FIG. 2 , that is, by protruding into the nozzle passage  24   b  to disrupt the flow of air therethrough. Airflow passing into the nozzle passage  24   b  may be reduced by the flow adjustment member  26   b  prior to exiting through a turbine wheel outlet  36 . 
   Similar to the flow adjustment member  26  in  FIG. 2 , the flow adjustment member  26   b  may be placed in a plurality of nozzle passages  24   b , equally spaced around the vaned adjustable flow turbine nozzle  20   b.    
   As can be appreciated by those skilled in the art, the present invention provides improved turbine nozzles and methods for their use in turbo machines. A flow adjustment member is provided to regulate the flow through the turbine nozzle without requiring labor- and time-intensive reworking and/or manufacturing. 
   It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.