Abstract:
A test device for a compressor has a valve and ducting connected to the valve. A flow nozzle connected to the ducting has a corresponding coefficient of flow. A pressure sensor connected to the flow nozzle measures a pressure of a working fluid, and a flow rate of the working fluid is calculated using the pressure and the coefficient of flow. A method for testing a compressor includes operating the compressor at a first power level, measuring a flow rate of a working fluid at the first power level, adjusting a pressure of the working fluid to equal a first predetermined pressure, and measuring operating parameters of the compressor at the first power level. The method also includes adjusting the pressure of the working fluid to equal a second predetermined pressure and measuring operating parameters of the compressor at the first power level with the pressure of the working fluid at the second predetermined pressure.

Description:
FIELD OF THE INVENTION 
     The present invention generally involves a test device for a compressor. More particularly, the present invention describes a calibrated flow control module for testing a compressor. 
     BACKGROUND 
     Compressors are widely used in gas turbines, jet engines, and various other industrial applications. A typical compressor includes multiple stages of aerofoils to progressively compress the working fluid. The multiple stages of aerofoils include rotating aerofoils, also known as blades or rotors, to accelerate the working fluid. Stationary aerofoils, also known as stators or vanes, decelerate and redirect the flow direction of the working fluid to the rotating aerofoils of the next stage. In this manner, the compressor produces a continuous flow of compressed working fluid for subsequent combustion and expansion to produce work. 
     Various devices exist to test the operational performance of compressors. For example, U.S. Pat. No. 6,220,086 describes a method and apparatus for testing the surge pressure ratio in compressors for turbines. The apparatus includes ducting that supplies the working fluid to the compressor inlet through a throttle valve. The position of the throttle valve is temporarily changed to briefly decrease the flow of working fluid into the compressor inlet during the testing. 
     The test device described in U.S. Pat. No. 6,220,086 does not include the ability to accurately measure the flow of working fluid into the compressor inlet. In addition, the test device does not include the ability to control the temperature of the working fluid prior to entry into the compressor inlet. Therefore, if the transient change in the flow of working fluid is not sufficient to perform the desired test, the process must be repeated, and the throttle valve must be temporarily changed to further briefly decrease the flow of working fluid into the compressor inlet to perform the desired test. Therefore, the test device may require a repetitive process to determine the correct throttle position to sufficiently reduce the flow of working fluid into the compressor inlet to perform the desired test. 
     Therefore, the need exists for a test device that can accurately deliver a desired flow of working fluid to a compressor for testing. In addition, the need exists for a test device that can increase the temperature of the working fluid prior to entry into the compressor inlet. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one embodiment of the present invention, a test device for a compressor includes a valve connected to the compressor and ducting connected to the valve. A flow nozzle connects to the ducting, and the flow nozzle has a corresponding coefficient of flow. A pressure sensor connected to the flow nozzle measures a pressure of a working fluid flowing through the flow nozzle, and a flow rate of the working fluid is calculated using the pressure of the working fluid and the coefficient of flow for the flow nozzle. 
     In another embodiment of the present invention, a test device for a compressor includes a valve connected to the compressor, and ducting connected to the valve. A flow nozzle connects to the ducting, and the flow nozzle has a corresponding coefficient of flow. Means for measuring a flow rate of a working fluid through the flow nozzle is connected to the flow nozzle. 
     The present invention also includes a method for testing a compressor. The method includes operating the compressor at a first power level, measuring a flow rate of a working fluid to the compressor at the first power level, and adjusting a pressure of the working fluid until the pressure of the working fluid entering the compressor equals a first predetermined pressure. The method further includes measuring operating parameters of the compressor at the first power level with the pressure of the working fluid entering the compressor at the first predetermined pressure. The method also includes adjusting the pressure of the working fluid until the pressure of the working fluid entering the compressor equals a second predetermined pressure and measuring operating parameters of the compressor at the first power level with the pressure of the working fluid entering the compressor at the second predetermined pressure. 
     Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
         FIG. 1  is a simplified plan view of an embodiment of a flow control module that may be included in a compressor test device; 
         FIG. 2  is a simplified plan view of a test device according to one embodiment of the present invention; and 
         FIG. 3  is a simplified block diagram of a test device according to an alternate embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. 
     Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIG. 1  provides a simplified plan view of an embodiment of a flow control module  10  that may be included in a compressor test device. As shown, the flow control module  10  generally includes a valve  12 , ducting  14 , a flow nozzle  16 , and means  18  for measuring the flow rate of the working fluid through the flow nozzle  16 . 
     The valve  12  may be any structure known to one of ordinary skill in the art for permitting and preventing flow. In particular embodiments, the valve  12  may also be capable of throttling to reduce the inlet pressure to the compressor being tested. For example, the valve  12  may be a globe valve, a throttle valve, a ball valve, a gate valve, a butterfly valve, or any equivalent structure. The particular type of valve selected will depend on operational factors, such as the anticipated flow rate, temperature, and/or inlet pressure at the compressor. For example, a 36 inch, flanged end, resilient seated butterfly valve is a suitable valve that permits sufficient flow of the working fluid, produces a minimal pressure drop across the valve, and provides a throttling capability. 
     The valve  12  may further include an actuator  20  for remote operation. The actuator  20  may be an electric motor, air motor, hydraulic motor, or any other equivalent device for remotely operating the valve  12 . 
     The ducting  14  connects the flow nozzle  16  to the valve  12  and provides a flow path for the working fluid. The ducting  14  may be made of any suitable material, such as sheet metal, plastic, urethane, or polyvinyl chloride. The ducting  14  is sized to obtain a desired Beta ratio based on the ASME nozzle throat diameter. For example, suitable ducting  14  for a 24 inch ASME long radius flow nozzle and a desired Beta of 0.5 may have a 48 inch inner diameter. Additional fittings  21  may be necessary to connect the ducting  14  to the flow nozzle  16  or valve  12 . 
     The flow nozzle  16  directs the flow of the working fluid into the ducting  14 . The flow nozzle  16  generally includes an inlet  22  and a throat  24  through which the working fluid flows. A suitable flow nozzle  16  within the scope of the present invention may be a 24 inch ASME long radius flow nozzle. 
     The flow control module  10  is calibrated to accurately measure the flow rate of the working fluid through the flow nozzle  16 , and thus into the compressor. Calibration of the flow control module  10  determines a flow coefficient (c) verses Reynold&#39;s Number (Rd) relationship for the flow control module  10 . 
     The means  18  for measuring the flow rate of the working fluid may include one or more pressure sensors, differential pressure sensors, pitot tubes, impulse tubes, or similar devices known to one of ordinary skill in the art for measuring fluid flow. For example, the flow nozzle  16  may include one or more pressure sensors  26 , such as an impulse tube, at the inlet  22  and throat  24  of the flow nozzle  16 . The pressure sensors  26  may be used to generate a differential pressure signal  28  which may then be used with the flow coefficient to calculate the flow of the working fluid through the flow control module  10 . The flow nozzle  16  may also include one or more temperature sensors  30  that measure the temperature of the working fluid so that the calculated flow rate may be adjusted for changes in temperature of the working fluid. 
       FIG. 2  is a simplified plan view of a test device  32  according to one embodiment of the present invention. In this embodiment, the test device  32  includes multiple flow control modules  34  connected by a plenum  36  to a compressor  38 . The actual number of flow control modules  34  in the test device depends on the flow requirements of the compressor being tested and can range from one to twenty-four or more. The total flow rate of the working fluid is calculated as the sum of the flow rates through each flow control module  34 . 
     As shown in  FIG. 2 , the test device  32  may include a silencer  40  at the inlet to the flow control modules  34 . The silencer  40  may include a screen, parallel baffle, muffler, or suitable equivalent structure known in the art for attenuating noise and/or preventing foreign objects from entering the test device  32 . A silencer duct  42  connects the silencer  40  to the flow control modules  34 . 
     Each flow control module  34  includes a valve  44 , ducting  46 , flow nozzle  48 , and means  50  for measure flow rate as previously described with respect to  FIG. 1 . 
     The plenum  36  connects the flow control modules  34  to the compressor  38 . The plenum  36  may be made of any suitable material, such as sheet metal, plastic, urethane, or polyvinyl chloride, and is sized to accommodate the desired flow rates anticipated for the compressor  38 . The plenum  36  should be capable of withstanding pressure and vacuum changes caused by the compressor testing. For example, typical compressor testing may produce pressure transients of approximately 1.5 atmospheres and vacuum transients of 200 inches of water column in the plenum  36  downstream of the flow control modules  34 . 
     The plenum  36  may include a baffle or perforated plates  52  to direct the flow of working fluid to attain the desired flow velocities downstream of the flow control modules  34 . A suitable arrangement may include, for example, three staggered perforated plates  52  with a perforated area of approximately 48.5%. 
       FIG. 3  is a simplified block diagram of a test device  54  connected to a compressor  56  according to an alternate embodiment of the present invention. The test device  54  includes a silencer  58 , one or more flow control modules  60 , and a plenum  62  as previously discussed with respect to  FIGS. 1 and 2 . The working fluid flows through the silencer  58  to the flow control modules  60 . The flow control modules  60  accurately measure the flow of the working fluid, and the positions of the valves  64  are adjusted to obtain the desired pressure of the working fluid at the inlet of the compressor  56  being tested. Perforated plates  66  in the plenum  62  direct the flow of working fluid to the compressor  56  through various elbows  68  and transition pieces  70  that connect the plenum  62  to the compressor  56 . 
     The test device  54  shown in  FIG. 3  further includes a bleed system  72  to heat the working fluid prior to entry into the compressor  56 . A first end  74  of the bleed system  72  connects to the discharge of the compressor  56 , and a second end  76  of the bleed system  72  connects to the test device  54 . The bleed system  72  diverts a portion of the compressed and heated working fluid back to the test device  54 , for example to the plenum  62  downstream of the flow control modules  60 . The bleed system  72  may include a flow control valve  78  remotely operable to regulate the amount of diverted air supplied to the test device  54 . 
     The test devices described in the present invention may be coupled to the inlet of a compressor to accurately measure the flow rate of the working fluid and adjust the pressure of the working fluid entering the compressor as the compressor operates at various power levels. For example, with the compressor operating at a first power level as required by a particular test, the test devices can accurately measure the flow rate of the working fluid to the compressor and adjust the valves until the pressure of the working fluid entering the compressor equals a first predetermined pressure. Operating parameters of the compressor, such as exhaust temperature, exhaust pressure, and compression ratio, may be measured and recorded at the first power level with the pressure of the working fluid at the inlet of the compressor at the first predetermined pressure. The test devices may then adjust the valves until the pressure of the working fluid entering the compressor equals a second predetermined pressure, and operating parameters of the compressor may again be measured and recorded. 
     The testing may then be repeated with the compressor operating at a second power level. As before, the test devices accurately measure the flow rate and adjust the pressure of the working fluid entering the compressor to third and fourth predetermined pressures to test the operating performance of the compressor. The third and fourth predetermined pressures may be the same as the first and second predetermined pressures, respectively. 
     During the compressor testing, the test device may further measure the temperature of the working fluid at the various power levels of the compressor. If the compressor test requires a particular temperature of the working fluid, the test device may further use the bleed system to heat the working fluid prior to entry into the compressor. Furthermore, the test device may pass the working fluid through perforated plates prior to entry into the compressor to regulate the flow of the working fluid into the compressor. 
     It should be appreciated by those skilled in the art that modifications and variations can be made to the embodiments of the invention set forth herein without departing from the scope and spirit of the invention as set forth in the appended claims and their equivalents.