Patent Publication Number: US-2019186269-A1

Title: Modulated Cooling Air Control System and Method for a Turbine Engine

Description:
CROSS REFERENCE 
     This application is related to and concurrently filed with co-pending U.S. patent application Ser. No. ______, filed Dec. 14, 2017, entitled “Flow Control in Modulated Air Systems”, bearing Docket Number G2640-00151/RCA11999, with named inventors Michael Grzelecki, Michael Monzella and Renee M. Wiley, and U.S. patent application Ser. No. ______, filed Dec. 14, 2017, entitled “Turbine Engine Cooling with Substantially Uniform Cooling Air Flow Distribution”, bearing Docket Number G2640-000148/RCA11988, with named inventors Matthew M. Miller and Renee M. Wiley. The entirety of each of these applications is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to turbine engine cooling systems, and more specifically to turbine engine cooling systems configured to modulate the flow of cooling air delivered to a cooled region based on temperature readings obtained from within the cooled region. 
     BACKGROUND 
     Certain known gas turbine engines include cooling systems configured to direct air from the compressor stage of the engine to the turbine stage of the engine to cool the components in the turbine stage, such as the turbine discs and blades. Since the cooling air is typically bled from the compressor, the work required to compress the cooling air is lost and thus the efficiency of the engine decreases as more cooling air is diverted from the compressor stage to the turbine stage. There is a continuing need to minimize the amount of air diverted from the compressor stage to the turbine stage for cooling. 
       FIG. 1  is a simplified partial cutaway view of an example gas turbofan engine  10  (sometimes referred to as the “engine” for brevity) having a rotational axis X-X. The engine  10  includes an air intake  11 , a propulsive fan  12 , an intermediate-pressure compressor  13 , a high-pressure compressor  14 , a combustor  15 , a high-pressure turbine  16 , an intermediate-pressure turbine  17 , a low-pressure turbine  18 , and an exhaust nozzle  19 . The high-pressure compressor  14  and the high-pressure turbine  16  are connected via a shaft  20  and rotate together about the rotational axis X-X. The intermediate-pressure compressor  13  and the intermediate-pressure turbine  17  are connected via a shaft  21  and rotate together about the rotational axis X-X. The fan  12  and the low-pressure turbine  18  are connected via a shaft  22  and rotate together about the rotational axis X-X. A fan nacelle  24  generally surrounds the fan  12  and defines the air intake  11  and a bypass duct  23 . Fan outlet guide vanes  25  secure the fan nacelle  24  to the core engine casing. 
     In operation, the fan  12  compresses air entering the air intake  11  to produce a bypass air flow that passes through the bypass duct  23  to provide propulsive thrust and a core air flow into the intermediate-pressure compressor  13 . The intermediate-pressure compressor  13  compresses the air before delivering the air to the high-pressure compressor  14 . The high-pressure compressor  14  further compresses the air and exhausts the compressed air into the combustor  15 . The combustor  15  mixes the compressed air with fuel and ignites the fuel/compressed air mixture. The resultant hot combustion products then expand through—and thereby drive—the high-, intermediate-, and low-pressure turbines  16 ,  17 , and  18  before being exhausted through the exhaust nozzle  19  to provide additional propulsive thrust. The high-, intermediate-, and low-pressure turbines  16 ,  17 , and  18  respectively drive the high-pressure compressor  14 , the intermediate-pressure compressor  13 , and the fan  12  via the respective shafts  20 ,  21 , and  22 . 
     SUMMARY 
     Various embodiments of the present disclosure provide a turbine engine cooling system configured to provide cooling air to a particular region of the engine to cool that region of the engine. The cooling system is configured to modulate the flow of cooling air to reduce the amount of cooling air flowing to that region of the engine during periods in which less cooling is needed to avoid providing more cooling air than is needed to adequately cool that region of the engine. The cooling system is configured to determine when to modulate the flow of cooling air based on temperature readings obtained from within the cooled region. 
     An embodiment of disclosed subject matter includes a turbine engine having a turbine section defining a first and second cavity, a cooling system having a modulation active mode and a modulation off mode; the cooling system supplying a first feed of cooling air to the first and second cavities in the modulation off mode and a second feed of cooling air to the first and second cavities in the modulation active mode and the first feed having a greater mass flow rate than a mass flow rate of the second feed. The disclosed turbine engine also including a first turbine disc defining a portion of the first cavity and a first rim defining another portion of the first cavity; a second turbine disc defining a portion the second cavity, a second rim defining another portion of the second cavity. The turbine engine further including a first temperature sensor configured to sense a temperature within the first cavity at the first rim of the first turbine disc; and a controller configured to monitor the sensed temperature; and place the cooling system in the modulation off mode based on a at least a determination that the sensed temperature exceeds a first threshold temperature. 
     The disclosed subject matter also includes a method for controlling the modulation cooling air flow in a turbine engine. An embodiment of the method including sensing, by a first temperature sensor, a temperature within a first cavity at a rim of a first turbine section, the first cavity defined in part by the first turbine section; generating, by the first temperature sensor, a signal representative of the sensed temperature; and sending, by the first temperature sensor and to a controller, the signal representative of the sensed temperature. The method further includes monitoring, by the controller, the sensed temperature; determining if the sensed temperature is greater than a first temperature threshold; and, controlling, by the controller, a flow control device to enable cooling air to flow at a first mass flow rate from a cooling air source into the first cavity and a second cavity, based on at least the determination the sensed temperature is greater than the first temperature threshold wherein the second cavity is defined in part by a second turbine section. 
     Another embodiment of the disclosed subject matter includes a method of controlling the modulation state of a cooling system in a turbine engine, wherein the cooling system has a first modulation state in which cooling air is provided to cool a plurality of turbine section rims at a first mass flow rate and a second modulation state in which cooling air is provided to cool the plurality of turbine section rims at a second mass flow rate. The method includes monitoring a first temperature of a first rim of the plurality of turbine section rims; and switching the operation of the cooling system from the second modulation state to the first modulation state when the monitored first temperature rises through a first temperature threshold; wherein the second mass flow rate is less than the first mass flow rate. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a partial cutaway view of one example embodiment of a turbofan gas turbine engine of the present disclosure. 
         FIG. 2  is a block diagram of one example embodiment of a turbine engine cooling system of the present disclosure. 
         FIG. 3  is a fragmentary cross-sectional view of part of the engine of  FIG. 1 . 
         FIG. 4  is a flowchart of one example method for modulating cooling air flow in a turbine engine of the present disclosure. 
         FIG. 5  is a flowchart of another example method for modulating cooling air flow in a turbine engine of the present disclosure. 
         FIG. 6  is a chart illustrating the effect of threshold selection on temperature cycling in a modulated cooling system. 
     
    
    
     DETAILED DESCRIPTION 
     While the features, methods, devices, and systems described herein may be embodied in various forms, the drawings show and the detailed description describes some exemplary and non-limiting embodiments. Not all of the components shown and described in the drawings and the detailed descriptions may be required, and some implementations may include additional, different, or fewer components from those expressly shown and described. Variations in the arrangement and type of the components; the shapes, sizes, and materials of the components; and the manners of attachment and connections of the components may be made without departing from the spirit or scope of the claims as set forth herein. This specification is intended to be taken as a whole and interpreted in accordance with the principles of the invention as taught herein and understood by one of ordinary skill in the art. 
     As used herein, “downstream” means in the direction of air flow, and “upstream” means opposite the direction of airflow. 
     Various embodiments of the present disclosure provide a turbine engine cooling system (sometimes referred to as the “cooling system” for brevity) configured to provide cooling air to a particular region of the engine  10  to cool that region of the engine  10 . The cooling system  100  is configured to modulate the flow of cooling air to reduce the amount of cooling air flowing to that region of the engine  10  during periods in which less cooling is needed to avoid providing more cooling air than is needed to adequately cool that region of the engine  10 . The cooling system is configured to determine when to modulate the flow of cooling air based on temperature readings obtained from within the cooled region. 
       FIG. 2  shows one example embodiment of a cooling system  100  fluidly connectable to a cooling air source  92  and a cooled region  96 . In this example embodiment, the cooling air source  92  is one the compressor stage (such as the high-pressure compressor stage) of the engine  10 , though the cooling air source may be any suitable source of cooling air in other embodiments. As shown in  FIG. 3 , the cooled region  96  includes a first cavity defined in part by the turbine disc and rim of the high-pressure turbine  16  (left arrow) and by the second turbine disc and rim of the intermediate-pressure turbine  17  (right arrow), and a second cavity defined in part by the second turbine disc and rim of the intermediate-pressure turbine  17 . However, the cooled region  96  may be any suitable region of the engine  10  to-be-cooled by cooling air from the cooling air source  92 , such as the low pressure turbine stages  18 . 
     The cooling system  100  includes a first cooling air tube (conduit, pipe, line, feed or duct)  102 , a flow control device  110 , a second cooling air tube  104 , a first temperature sensor  120 , a second temperature sensor  130 , and a controller  140 . The cooling system may include any suitable quantity of cooling air tubes configured to (as explained below) direct cooling air from the cooling air source  92  into the cooled region  96 , even though only one set of cooling air tubes is shown in  FIG. 2  for clarity. 
     The flow control device  110  is a suitable device configured to control whether and how much cooling air can flow from the cooling air source  92  to the cooled region  96 . The flow control device  110  has a cooling air inlet and a cooling air outlet (not labeled). In one example embodiment, the flow control device  110  includes a valve. In another example embodiment, the flow control device  110  includes a valve and a vortex amplifier fluidly connectable to a control air source, as described in U.S. Pat. No. 7,712,317, the entire contents of which are incorporated herein by reference. 
     The first and second temperature sensors  120  and  130  are thermocouples or any other suitable sensors configured to sense the temperature of a fluid and to generate and send signals that correspond to the sensed temperature to the controller  140  (described below). Suitable sensors may include strain gages, transducers or electromagnetic transceivers. 
     The controller  140  includes a central processing unit (CPU) (not shown) communicatively connected to a memory (not shown). In certain embodiments, the engine control system of the aircraft functions as the controller  140 , while in other embodiments the controller  140  is a dedicated controller of the cooling system  100 . The CPU is configured to execute program code or instructions stored on the memory to control operation of the cooling system  100 . The CPU may be a microprocessor; a content-addressable memory; a digital-signal processor; an application-specific integrated circuit; a field-programmable gate array; any suitable programmable logic device, discrete gate, or transistor logic; discrete hardware components; or any combination of these. The CPU may also be implemented as a combination of these devices, such as a combination of a digital signal processor and a microprocessor, a plurality of microprocessors, or one or more microprocessors in conjunction with a digital signal processor core. 
     The memory is configured to store, maintain, and provide data as needed to support the functionality of the cooling system  100 . For instance, in various embodiments, the memory stores program code or instructions executable by the CPU to control operation of the cooling system  100 . The memory includes any suitable data storage device or devices, such as volatile memory (e.g., random-access memory, dynamic random-access memory, or static random-access memory); non-volatile memory (e.g., read-only memory, mask read-only memory, programmable read-only memory, erasable programmable read-only memory, electrically erasable programmable read-only memory); and/or non-volatile random-access memory (e.g., flash memory, solid-state storage). 
     One end of the first cooling air tube  102  is in fluid communication with the cooling air source  92 , and the other end of the first cooling air tube  102  is in fluid communication with the cooling air inlet of the flow control device  110 . One end of the second cooling air tube  104  is in fluid communication with the cooling air outlet of the flow control device  110 , and the other end of the second cooling air tube  104  is in fluid communication with the cooled region  96 . The first cooling air tube  102 , the flow control device  110 , and the second cooling air tube  104  define a cooling air path between the cooling air source  92  and the cooled region  96 . 
     As best shown in  FIG. 3 , the first temperature sensor  120  is positioned at the rear rim  162  of the high-pressure turbine section  16  such that the first temperature sensor  120  can sense the temperature of the fluid within the cavity  161  defined by the rear rim  162  and the high-pressure turbine disc  163 . As also shown in  FIG. 3 , the second temperature sensor  130  is positioned in the cavity  171  defined by the front rim  172  and the intermediate-pressure turbine disc  173  (i.e., downstream of the first temperature sensor  120 ) such that the second temperature sensor  130  can sense the temperature of the fluid within the cavity  171  of the intermediate-pressure turbine section  17 . 
     As shown in  FIG. 2 , the controller  140  is operatively connected to the flow control device  110  to control the flow control device  110  to control the amount of cooling air that can flow through the first cooling air path, as described below in accordance with  FIGS. 4 and 5 . The controller  140  is communicatively connected to the first and second temperature sensors  120  and  130  to receive the signals from the temperature sensors that correspond to the sensed temperatures. While not shown it is equally envisioned that additional temperature sensors position in cavities of additional turbine sections may also be implemented. 
     In operation, initially, the controller  140  controls the flow control device  110  such that cooling air flows from the cooling air source  92  through the first cooling air passage and into the cooled region  96  at a first mass flow rate. During operation, the first and second temperature sensors  120  and  130  periodically sense the fluid temperature at the rear rim of the high-pressure turbine section  16  and the front rim of the intermediate-pressure turbine section  17 , respectively; generate signals corresponding to the sensed temperatures; and send the signals to the controller  140 . 
     The controller  140  monitors the sensed temperatures to (in part) determine whether a modulation condition is satisfied. When the modulation condition is satisfied, less cooling air is required to adequately cool the cooled region  96 . In this example embodiment, the modulation condition is satisfied when both: (1) the sensed temperature at the rear rim  162  of the high-pressure turbine section  16  (the “first sensed temperature”) is below a first low temperature threshold  602  and (2) the sensed temperature at the front rim  172  of the intermediate-pressure turbine section  17  (the “second sensed temperature”) is below a second low temperature threshold (that may be less than the first temperature threshold, given the nature of the materials used in the intermediate pressure turbine section vs. those used in the high pressure turbine section). 
     Responsive to determining that the modulation condition is satisfied, the controller  140  controls the flow control device  110  such that cooling air flows from the cooling air source  92  through the first cooling air passage  104  and into the cooled region  96  (cavities  161  and  171 ) at a second mass flow rate that is less than the first mass flow rate. The controller  140  continues to monitor the sensed temperatures to (in part) determine whether a non-modulation condition is satisfied. When the non-modulation condition is satisfied, more cooling air is required to adequately cool the cooled region  96 . In this example embodiment, the non-modulation condition is satisfied when the first of: (1) the first sensed temperature exceeds a first high temperature threshold that is greater than the first low temperature threshold; and (2) the second sensed temperature exceeds a second high temperature threshold that likewise is greater than the second low temperature threshold (and may be less than the first high temperature threshold). The high temperature thresholds are a function of at least the materials and structures in the respective high pressure and intermediate pressure turbine sections. For example, the high pressure turbine section may be formed from a nickel alloy with high heat tolerance while the intermediate pressure turbine section by use a less expensive alloy with less heat tolerance. 
     Responsive to determining that the non-modulation condition is satisfied, the controller  140  controls the flow control device  110  such that cooling air flows from the cooling air source  92  through the first cooling air passage and into the cooled region  96  at the first mass flow rate. At this point, the controller  140  continues to monitor the sensed temperatures to (in part) determine whether the modulation condition is satisfied. 
       FIG. 4  is a flowchart illustrating a method  400  for modulating cooling air flow from a cooling air source to a turbine section cavity of a turbine engine. In various embodiments, instructions stored in the memory of the controller  140  and executed by the CPU of the controller  140  represent the method  400 . Although the method  400  is described with respect to the flowchart shown in  FIG. 4 , other methods of performing the acts described below may be employed. In certain embodiments, the blocks or diamonds are performed in the order in which they are shown, while in other embodiments the blocks or diamonds are performed in different orders. 
     The method  400  starts responsive to activation of the turbine engine or receipt of an input to activate the modulation system. In response, a first temperature sensor begins periodically sensing a first temperature at a rim of a first turbine in the turbine section cavity, as block  402  indicates, and a second temperature sensor begins periodically sensing a second temperature at a rim of a second turbine in the turbine section cavity, as block  404  indicates. The first and second temperature sensors generate signals representative of the first and second sensed temperatures, respectively, and send the signals to a controller. The controller monitors the first and second sensed temperatures, as block  406  indicates. 
     Also in response to receipt of the instructions to begin directing cooling air from the cooling air source to the turbine section cavity, the controller controls a flow control device to enable the cooling air to flow at a first mass flow rate from the cooling air source into the turbine section cavity, as block  408  indicates. The controller determines whether a modulation condition is satisfied based in part on the first and second sensed temperatures, as diamond  410  indicates. 
     Responsive to determining at diamond  410  that the modulation condition is satisfied, the controller controls the flow control device to enable the cooling air to flow at a second mass flow rate that is less than the first mass flow rate from the cooling air source into the turbine section cavity, as block  412  indicates. The controller determines whether a non-modulation condition is satisfied based in part on one of the first and second sensed temperatures, as diamond  414  indicates. Responsive to determining at diamond  414  that the non-modulation condition is satisfied, the process  400  returns to block  408  and the controller again controls the flow control device to enable the cooling air to flow at the first mass flow rate from the cooling air source to the turbine section cavity. 
     Generally, the turbine section cavity heats up when the cooling air is flowing into the turbine section cavity at the second mass flow rate and cools down when the cooling air is flowing into the turbine section cavity at the first mass flow rate. This causes the turbine cavity to experience cyclical heating and cooling as the cooling system turns cooling air modulation on and off. In certain embodiments, the controller  140  is configured with a low temperature threshold selected to prevent excessive cycling of the system (e.g. selection of a threshold that is lower than required) to prevent damages to components of the engine  10 .  FIG. 6  illustrates the deleterious cycling that may occur if the low temperature threshold selected is too high. The first high temperature threshold is shown as line  601 . When the sensed temperature of the cavity reaches the first high temperature threshold the modulation system turns OFF (enters OFF state/mode). With the introduction of cooling air, the sensed temperature falls until it reaches the low temperature limit at which time the modulation system turns ON (enters the Active state/mode).  FIG. 6  also illustrates the behavior of the modulated cooling system with two different low temperature thresholds. The first low temperature threshold  602  causes excessive cycling of the system, whereas a lower low temperature threshold  603  may be selected to reduce the cycling. 
     In other embodiments, the cooling system includes a single temperature sensor  120 . In operation, initially, the controller  140  controls the flow control device  110  such that cooling air flows from the cooling air source  92  through the first cooling air passage and into the cooled region  96  at a first mass flow rate. During operation, the first temperature sensor  120  periodically senses the fluid temperature of the cavity  161  at the rear rim  162  of the high-pressure turbine section  16 , generates a signal corresponding to the sensed temperature, and sends the signal to the controller  140 . 
     The controller  140  monitors the sensed temperature to (in part) determine whether a modulation condition is satisfied. When the modulation condition is satisfied, less cooling air is required to adequately cool the cooled region  96  (cavities  161  and  171 ). In this example embodiment, the modulation condition is satisfied when: (1) the sensed temperature in the cavity  161  at the rear rim  162  of the high-pressure turbine section  16  (the “first sensed temperature”) is below a first low temperature threshold. In these embodiments employing a single temperature sensor to control cooling air flow modulation, the first low temperature threshold may be lower than the first threshold temperature in embodiments employing multiple temperature sensors to control cooling air flow modulation. This accounts for the fact that the temperature of the cavity  171  at the front rim of the intermediate-pressure turbine section  17  is not measured and thus the first low temperature threshold must be established with the intermediate pressure turbine section  17  in mind, in addition to provide additional leeway to reduce or eliminate the potential for the front rim of the intermediate-pressure turbine section  17  to reach failure temperature. 
     Responsive to determining that the modulation condition is satisfied, the controller  140  controls the flow control device  110  such that cooling air flows from the cooling air source  92  through the first cooling air passage and into the cooled region  96  at a second mass flow rate that is less than the first mass flow rate. The controller  140  continues to monitor the sensed temperature to (in part) determine whether a non-modulation condition is satisfied. When the non-modulation condition is satisfied, more cooling air is required to adequately cool the cooled region  96 . In this example embodiment, the non-modulation condition is satisfied when the first sensed temperature exceeds a first high temperature threshold that again would be necessarily greater than the first low temperature threshold. 
     Responsive to determining that the non-modulation condition is satisfied, the controller  140  controls the flow control device  110  such that cooling air flows from the cooling air source  92  through the first cooling air passage and into the cooled region  96  at the first mass flow rate. At this point, the controller  140  continues to monitor the sensed temperature to (in part) determine whether the modulation condition is satisfied. 
       FIG. 5  is a flowchart illustrating a method  500  for modulating cooling air flow from a cooling air source to a turbine section cavity of a turbine engine. In various embodiments, instructions stored in the memory of the controller  140  and executed by the CPU of the controller  140  represent the method  500 . Although the method  500  is described with respect to the flowchart shown in  FIG. 5 , other methods of performing the acts described below may be employed. In certain embodiments, the blocks or diamonds are performed in the order in which they are shown, while in other embodiments the blocks or diamonds are performed in different orders. 
     The method  500  starts responsive to activation of the turbine engine or receipt of an input to activate the modulation system. In response, a first temperature sensor begins periodically sensing a first temperature at a rim of a first turbine in the turbine section cavity, as block  502  indicates. The first temperature sensor generates a signal representative of the first sensed temperature and sends the signals to a controller. The controller monitors the first sensed temperature, as block  504  indicates. 
     Also in response to receipt of the instructions to begin directing cooling air from the cooling air source to the turbine section cavity, the controller controls a flow control device to enable the cooling air to flow at a first mass flow rate from the cooling air source into the turbine section cavity, as block  506  indicates. The controller determines whether a modulation condition is satisfied based in part on the first sensed temperature, as diamond  508  indicates. 
     Responsive to determining at diamond  508  that the modulation condition is satisfied, the controller controls the flow control device to enable the cooling air to flow at a second mass flow rate that is less than the first mass flow rate from the cooling air source into the turbine section cavity, as block  510  indicates. The controller determines whether a non-modulation condition is satisfied based in part on the first sensed temperature, as diamond  512  indicates. Responsive to determining at diamond  512  that the non-modulation condition is satisfied, the process  500  returns to block  506  and the controller again controls the flow control device to enable the cooling air to flow at the first mass flow rate from the cooling air source to the turbine section cavity. 
     An aspect of the disclosed subject matter also includes the use of a control parameter that is a function of cavity temperature and other system characteristics such as cavity pressure, core flow temperature, core flow pressure, or time (duration). While the temperature measurement in the cooled region is a primary way to control the system since the temperatures it measures are likely the most sensitive in the cooling air system, the controlled parameter could be varied based on a schedule with the other reference parameter which could allow for high fidelity limits and the ability to detect failures in both the modulated and non-modulated state of the air system by comparing measured temperatures against the scheduled air system temperatures. 
     Various modifications to the embodiments described herein will be apparent to those skilled in the art. These modifications can be made without departing from the spirit and scope of the present disclosure and without diminishing its intended advantages. It is intended that such changes and modifications be covered by the appended claims.