Patent Publication Number: US-2023151897-A1

Title: Fuel nozzle with reduced flow tolerance

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This patent application is a continuation of co-pending U.S. patent application Ser. No. 16/702,240, filed Dec. 3, 2019, the entire teachings and disclosure of which are incorporated herein by reference thereto. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to fuel nozzles for jet engines. 
     BACKGROUND OF THE INVENTION 
     Gas turbines for jet engines typically incorporate fuel nozzles arranged in a circumferentially uniform pattern around the engine&#39;s axis where fuel is introduced into the combustor via the nozzles. Furthermore, fuel nozzles with a “wide” flow range may be equipped with flow metering valves to optimize low and high flow rate spray quality. Fuel is regulated with valve ports designed to satisfy customer required fuel flow rates. Flow passage geometric variation and valve displacement non-uniformity (hysteresis) contribute to flow variability in each fuel nozzle. Valves are typically spring loaded and are actuated with increasing fuel flow pressure, initially to open, and subsequently displacing in response to higher pressure values. Valve displacement is generally unimpeded throughout the full range of imposed fuel flow pressure. 
     Jet engine operation typically requires that the fuel nozzles have a minimum nozzle flow tolerance, especially at higher engine power settings. Embodiments of the invention described below provide a fuel nozzle which improves the state of the art with respect to minimum flow tolerance. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect, embodiments of the invention provide a fuel nozzle metering valve that includes a spool having an inlet port and an outlet flow port, and a retainer assembled to one end of the spool. A valve liner which houses a portion of the spool. The spool is configured to move back and forth within the valve liner. The metering valve is biased in a closed position in which the outlet flow port is disposed entirely within the valve liner. The valve is opened when the spool slides within the valve liner such that some portion of the outlet flow port extends beyond an end of the valve liner. The retainer has a stepped portion configured to abut an end of the valve liner at a fuel flow pressure below the expected maximum fuel flow pressure to be used in the fuel nozzle metering valve. 
     In a particular embodiment, wherein the spool is configured to slide out of the valve liner when a fuel flow pressure from fuel flowing into the inlet port overcomes the closing bias on the metering valve. The retainer may be disc-shaped and, in certain embodiments, the stepped portion extends from a central region of the disc-shaped retainer. The stepped portion may be cylindrical or partially cylindrical. 
     In some embodiments, the valve liner is fixed within the fuel nozzle, and wherein the spool and retainer move relative to the valve liner. In a further embodiment, the metering valve is biased in a closed position by a spring. The spring may include a first end abutting a flange of the retainer and may have a second end abutting a flange of the valve liner. 
     In another aspect, embodiments of the invention provide a fuel nozzle check valve that includes a spool and a valve liner having an inlet port, and a retainer assembled to one end of the spool. A valve liner houses a portion of the spool. The spool is configured to move back and forth within the valve liner. The valve liner includes a valve liner port in fluid communication with an outlet flow port on the valve liner when the check valve is in the open position. The check valve is biased in a closed position in which the outlet flow port is disposed entirely within the valve liner. The valve is opened when the spool slides within the valve liner such that some portion of the outlet flow port opens to permit through flow. The retainer has a stepped portion configured to abut an end of the valve liner at a fuel flow pressure below the expected maximum fuel flow pressure to be used in the fuel nozzle check valve. 
     In a particular embodiment, the spool is configured to slide out of the valve liner when a fuel flow pressure from fuel flowing into the inlet port overcomes the closing bias on the check valve. The retainer may be disc-shaped and, in certain embodiments, the stepped portion extends from a central region of the disc-shaped retainer. The stepped portion may be cylindrical or partially cylindrical. 
     In some embodiments, the valve liner is fixed within the fuel nozzle, and wherein the spool and retainer move relative to the valve liner. In other embodiments, the check valve is biased in a closed position by a spring. In a particular embodiment, the spring has a first end abutting a flange of the retainer and a second end abutting a flange of the valve liner. 
     Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
         FIG.  1    is a cross-sectional view of a fuel nozzle metering valve with a flow-limiting feature, constructed in accordance with an embodiment of the invention; 
         FIG.  2    is a cross-sectional view of a fuel nozzle check valve with a flow-limiting feature, constructed in accordance with an embodiment of the invention; and 
         FIG.  3    is a graphical illustration showing an exemplary flow variation for an embodiment of the fuel nozzle disclosed herein. 
     
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     For any given flow device operating at a set condition, the flow rate through the device is proportional to the square root of the pressure difference across the device. The flow rate is also proportional to the device&#39;s flow path area. Any variation in the area of the flow path will thus cause flow variation at any set condition. Therefore, conventional jet engine fuel nozzles, with integral flow metering valves or check valves, tend to introduce additional flow path variations, and corresponding flow rate variations, due to the dynamic nature of each valve in each fuel nozzle within the jet engine. 
     As will be described below, embodiments of the present invention provide improved flow tolerances for any fuel nozzle equipped with a check valve or a metering valve, especially at high flow rates where combustor and turbine durability and reliability are most sensitive to flow non-uniformity. One of ordinary skill in the art will be able to recognize, from the embodiments shown, that valve flow port design configuration, and limiting the maximum valve displacement that can occur prior to maximum pressure, assures that fixed flow circuit geometry is achieved at all pressure points greater than maximum displacement. In this scenario, valve spring behavior, valve port geometry and valve clearance effects become fixed features within the fuel nozzle. This acts to limit variations in the flow rate and reduces the flow tolerance. 
       FIG.  1    is a cross-sectional view of a fuel nozzle metering valve  100  with a flow-limiting feature, constructed in accordance with an embodiment of the invention. The metering valve  100  has a spring-loaded poppet, or spool  102 , having one or more flow control ports  104 , which moves back and forth within a sleeve or valve liner  106  in response to fuel flow pressure. The valve liner  106  is fixed within the fuel nozzle. A spring retainer  108  is assembled to one end of the spool  102  such that when the spool  102  moves within the valve liner  106 , the spring retainer  108  moves with the spool  102 . The spring retainer  108  is machined to limit spool displacement at a specified flow and fuel flow pressure. When the fuel nozzle metering valve  100  is operated as described, the spring-loaded spool  102  and spring retainer  108  operate to accurately set valve flow in a fixed geometry state. 
     In operation, fuel flows into metering valve  100  via inlet port  112  and exits the metering valve  100  through the one or more flow control ports  104  when the valve  100  is in the open position. When the fuel flow pressure is relatively low, the metering valve  100  is biased in the closed position. While various means for biasing the metering valve  100  may be used,  FIG.  1    shows the biasing means as a spring  110  which closes the valve  100  such that there is no fuel flow through the metering valve  100 . One end of the spring  110  abuts a valve liner flange  122  while the other end of the spring  110  abuts a spring retainer flange  124 . In the embodiment of  FIG.  1   , fuel does not flow when the one or more flow control ports  104  are positioned inside of the valve liner  106 . When the bias pressure is such that the spool  102  unseats from the valve liner  106 , leakage flow occurs even though the one or more flow control ports  104  are still within the valve liner  106 . However, when the pressure from fuel flowing into inlet port  112  increases, the flow control ports  104  start to slide out of the valve liner  106 . As the flow control ports  104  extend beyond the second end  116  of the valve liner  106 , fuel can flow out from the metering valve  100 . 
     As the fuel flow pressure increases, a step  118  machined into the spring retainer  108  abuts the first end  114  of the valve liner  106  and acts as a flow-limiting feature. The step  118  portion of the spring retainer  108  extends toward the first end  114  of valve liner  106 . In a particular embodiment, the spring retainer  108  is disc-shaped, and the step  118  extends from a central portion of the disc toward first end  114 . The step  118  may be cylindrical or partially cylindrical. The spring retainer  108  is designed so that the step  118  abuts the first end  114 , after some amount of spool displacement due to fuel flow pressure, well before the maximum fuel flow pressure is reached. Thus, for some portion of the fuel flow pressure, the flow geometry of the metering valve  100  is fixed. As a result, the fuel flow rate through the metering valve  100  is more predictable than in conventional fuel nozzles with conventional metering valves. 
     The space  120  indicated on  FIG.  1    shows the maximum spool displacement. On one side of this space  120 , the first end of valve liner  106  which limits the spool  102  in the open position. At the other side of space  120 , spool displacement is limited by either the spool  102  abutting an interior portion of first end  114  maximum bias or by the maximum bias exerted by spring  110 . The dimensions of the step  118  are designed to provide a specific fuel flow profile for each individual fuel nozzle. 
       FIG.  2    is a cross-sectional view of a fuel nozzle check valve  200  with a flow-limiting feature, constructed in accordance with an embodiment of the invention. The check valve  200  has a similar arrangement, to that shown in  FIG.  1   , for limiting check valve assembly spool displacement. In this configuration, one or more outlet flow ports  204  are incorporated into the valve liner  206 , but the basic concept remains the same as in the metering valve  100  of  FIG.  1   . 
     The spool  202  moves back and forth within the valve liner  206  in response to fuel flow pressure. The valve liner  206  position is fixed within the fuel nozzle. A spring retainer  208  is assembled to one end of the spool  202  such that when the spool  202  moves within the valve liner  206 , the spring retainer  208  moves with the spool  202 . The spring retainer  208  is machined to limit spool displacement at a specified flow and fuel flow pressure. As in the embodiment of  FIG.  1   , when the fuel nozzle check valve  200  is operated, the spring-loaded spool  202  and spring retainer  208  operate to accurately set valve flow in a fixed geometry state at less than the maximum expected fuel pressure. 
     In operation, the downstream diameter of spool  202  extends beyond the one or more outlet flow ports  204 . Fuel flows into check valve  200  via inlet port  212  and exits the check valve  200  through one or more outlet flow ports  204  when the valve  200  is in the open position. When the fuel flow pressure is relatively low, the check valve  200  is biased in the closed position. Fuel does not flow when the check valve  200  is in the closed position due to the one or more outlet flow ports  204  being blocked by the spool  202 . While various means for biasing the check valve  200  may be used,  FIG.  2    shows the biasing means as a spring  210  which closes the valve  200  such that there is no fuel flow through the check valve  100 . One end of the spring  210  abuts a valve liner flange  222  while the other end of the spring  210  abuts a spring retainer flange  224 . 
     When the pressure from fuel flowing into inlet port  212  is sufficient to overcome the closing bias of spring  210 , the spool  202  starts to slide out of the valve liner  206  while the spring retainer  208  is pulled toward a first end  214  of the valve liner  206 . As the one or more outlet flow ports  204  extend beyond the second end  216  of the valve liner  206 , fuel can flow out from the check valve  200 . In the embodiment of  FIG.  2   , the one or more outlet flow ports  204  are disposed on a perimeter portion at an end of the valve liner  206 . This end of the valve liner includes four projections  226  arranged cylindrically with four equally-spaced gaps  228 , the four equally-spaced gaps  228  separating the four projections  226 . When the spool  202  slides a sufficient distance out from the valve liner  206 , fuel can flow from the one or more outlet flow ports  204  where the gaps  228  are situated. 
     As the fuel flow pressure increases, a step  218  machined into the spring retainer  208  abuts the first end  214  of the valve liner  206  and acts as a flow-limiting feature. The step  218  portion of the spring retainer  208  extends toward the first end  214  of valve liner  206 . 
     In a particular embodiment, the spring retainer  208  is disc-shaped, and the step  218  extends from a central portion of the disc toward first end  214 . The step  218  may be cylindrical or partially cylindrical. The spring retainer  208  is designed so that the step  218  abuts the first end  214 , after some amount of spool displacement due to fuel flow pressure, well before the maximum fuel flow pressure is reached. Thus, for some portion of the fuel flow pressure, the flow geometry of the check valve  200  is fixed, making the fuel flow rate through the check valve  200  more predictable than in conventional fuel nozzles with conventional check valves. 
     As with  FIG.  1   , the space  220  indicated on  FIG.  2    shows the maximum spool displacement. On one side of this space  220 , the first end of valve liner  206  which limits the spool  202  in the open position. At the other side of space  220 , spool displacement is limited by either the spool  202  abutting an interior portion of first end  214  maximum bias or by the maximum bias exerted by spring  210 . The dimensions of the step  218  are designed to provide a specific fuel flow profile for each individual fuel nozzle. 
     The fuel flow tolerances of nozzles constructed in accordance with an embodiment of the invention were tested against the tolerance specification requirement for such fuel nozzles. The average min-max flow variation of 20 tested fuel nozzle assemblies, constructed in accordance with an embodiment of the invention, was 42 percent less than nominal specification requirement at the highest inlet pressure. This average min-max flow variation for the set of twenty nozzle assemblies through the range of operating pressures is shown in the graphical illustration of  FIG.  3   . The graph shows the percentage of flow variation as it relates to inlet pressure. The upper curve  250  depicts the flow variation specification for a typical fuel nozzle. The lower curve  252  shows the average flow variation for the 20 fuel nozzles constructed in accordance with an embodiment of the invention described herein. 
     As explained above, the fuel nozzle flow tolerance reduction, shown in  FIG.  3   , is achieved with fixed valve geometry at higher flow rates. Limiting valve displacement before maximum inlet pressure reached is how the fuel nozzle valves function to achieve this fixed geometry. Maximum valve displacement for each assembly is set at target flow and pressure, enabling repeatable flow rates that would otherwise depend on the compounding effect of component geometry variations. 
     All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.