Patent Description:
In general, performance of gas turbine systems may degrade over time. Certain systems, such as an industrial control system, may provide for capabilities that enable the control and analysis of a gas turbine system. For example, the industrial control system may include controllers, field devices, and sensors storing data used in controlling the turbine system. Certain industrial control systems may use modeling for enhancing the industrial control system. For example, model-based controls (e.g., an onboard, real time gas turbine model) may be utilized to calculate parameters for direct boundary control for parameters that are not directly measured. However, certain gas turbine systems may lack these model-based controls. It would be beneficial to provide an alternative control strategy for these gas turbine systems lacking model-based controls to enable these gas turbine systems to run to various boundary constraints at full power to provide maximum performance over a wide range of operating conditions.

A system in accordance with the invention as hereinafter claimed includes the features of claim <NUM> below.

A method in accordance with the invention as hereinafter claimed includes the features of claim <NUM> below.

A non-transitory computer-readable medium in accordance with the invention as hereinafter claimed includes the features of claim <NUM> below.

One or more specific embodiments of the present subject matter will be described below. It should be appreciated that in the development of any such actual implementation, as in any engineering project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the present subject matter, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements.

Many current heavy duty gas turbine systems run to various boundary constraints at full power in order to provide maximum performance over a wide range of operating conditions. Typically, a key element to achieving this performance level is the utilization of model-based control (MBC) strategy where a real time model of a gas turbine is embedded (onboard model) in a control system that provides accurate calculations for direct boundary control parameters (e.g., turbine exit Mach number (Mn)). The absence of a MBC strategy, in certain gas turbine systems, hinders the ability to achieve full performance potential.

The present disclosure is directed towards systems and methods that provide an accurate and robust (as well as easily constructed) turbine exit Mn surrogate that may be utilized for limit control on heavy duty gas turbines that do not have MBC control. In certain embodiments, the non-MBC strategy utilizing the turbine exit Mn surrogate may also be utilized on gas turbine systems that have an onboard model where the model lacks any provision for turbine exit Mn control. The turbine exit Mn surrogate is calculated based on feedback ( measured parameters) from sensors within the gas turbine system. These measured parameters ( compressor discharge pressure, exhaust section exit pressure, and exhaust temperature adjusted for radial profile effects) correlate to parameters related to turbine exit corrected flow function (which is strongly correlated to turbine exit Mn) that otherwise would be utilized directly calculate the turbine exit Mn but that are not measured on the gas turbine system (e.g., turbine exit flow, turbine exit total pressure, and turbine exit temperature). The turbine exit Mn surrogate limit level functionally corresponds to an equivalent Mn based on cycle performance with the limit defined in surrogate space. The turbine exit Mn surrogate may be utilized to derive and perform a control action (e.g., on an actuator of inlet guide vane (IGV). The utilization of the turbine exit Mn surrogate may enable hardware upgrades on gas turbine systems that are more cost effective than a full MBC upgrade to support the hardware upgrade.

With the forgoing in mind, <FIG> is a block diagram of an embodiment of a turbine system <NUM> (e.g., gas turbine system) that may use the presently disclosed techniques for calculating a turbine exit Mn surrogate and utilizing the turbine exit Mn surrogate in controlling the performance of the turbine system <NUM>. The illustrated turbine system <NUM> includes a gas turbine engine <NUM> coupled to a load <NUM>, such as an electrical generator. The gas turbine engine <NUM> includes a compressor <NUM>, a plurality of combustors <NUM> each having at least one fuel nozzle <NUM>, a turbine <NUM>, and an exhaust section <NUM> (e.g., diffuser section). As illustrated, one or more shafts <NUM> connect the load <NUM>, compressor <NUM>, and turbine <NUM>. The compressor <NUM> includes at least one row of inlet guide vanes (IGVs) <NUM>. The compressor <NUM> and the turbine <NUM> each include a rotor with blades, which rotate within a stator or shroud. In operation, the compressor <NUM> receives air <NUM> and delivers compressed air <NUM> to the combustors <NUM> and/or fuel nozzles <NUM>, which then inject fuel <NUM> (or an air-fuel mixture) into a combustion region in the combustors <NUM>. In turn, the air-fuel mixture combusts in the combustors <NUM> to produce hot combustion gases <NUM>, which drive blades within the turbine <NUM>. As the turbine <NUM> is driven to rotate the shaft <NUM>, the compressor <NUM> is driven to compress the air <NUM> into the combustors <NUM> and/or fuel nozzles <NUM>.

Additionally, the illustrated turbine system <NUM> includes a controller <NUM> that may generally control the operations of the turbine system <NUM>. For example, in certain embodiments, the controller <NUM> may be coupled to a number of sensors <NUM> (e.g., temperature sensors, pressure sensors, flow rate sensors, or other suitable sensors) disposed throughout the gas turbine engine <NUM>. The controller <NUM> may communicate (e.g., via a network or bus) with the sensors <NUM> to receive information regarding the turbine engine <NUM>. For example, the controller <NUM> may communicate with a temperature sensor <NUM> coupled to the exhaust section <NUM> of the gas turbine engine <NUM> to receive a temperature of the exhaust gases (e.g., measured along a control exhaust temperature measurement plane). By further example, a pressure sensor <NUM> coupled to the compressor <NUM> may communicate to the controller <NUM> a compressor discharge pressure. By even further example, a pressure sensor <NUM> coupled to the exhaust section <NUM> may communicate to the controller <NUM> an exhaust pressure at the exit of the exhaust section <NUM>. Furthermore, in certain embodiments, the controller <NUM> may also communicate with certain components of the turbine system (e.g., the compressor <NUM>, the combustor <NUM>, the turbine <NUM>, intake vanes (e.g., IGVs <NUM>), valves, pumps, actuators, or other suitable components) to control or alter the operation of the gas turbine engine <NUM>. For example, the controller <NUM> may communicate with the compressor <NUM> of the gas turbine engine <NUM> to instruct the field device to open or close an air intake to allow more or less air <NUM> into the compressor <NUM>. Additionally, the controller <NUM> may communicate with a fuel actuator on the gas turbine engine <NUM> to selectively regulate fuel flow, fuel splits, and/or a type of fuel channeled between the fuel supply <NUM> and the combustors <NUM>. Further, the controller <NUM> may communicate with additional actuators to adjust a relative position of the IGVs, adjust inlet bleed heat, or activate other control settings on the gas turbine engine <NUM>.

In addition, operations executed by the controller <NUM> include determining or calculating a surrogate value for the turbine exit Mn based on the feedback from the sensors <NUM>. For example, as described in greater detail below, the surrogate value for the turbine exit Mn may be calculated based on compressor discharge pressure, exhaust section exit pressure, and exhaust temperature adjusted for radial profile effects. The surrogate value for the turbine exit Mn serves as a boundary control or operational limit for the gas turbine engine <NUM>. Operations executed by the controller <NUM> also include utilizing the surrogate value for the turbine exit Mn to derive a control action for the gas turbine engine <NUM>. In particular, the surrogate value may be utilized as an input to a compressor IGV, closed loop max open effector control constraint.

Furthermore, the controller <NUM> includes a processor <NUM> and a memory <NUM> (e.g., a non-transitory computer-readable medium/memory circuitry) communicatively coupled to the processor <NUM>, storing one or more sets of instructions (e.g., processor-executable instructions) implemented to perform operations related to the gas turbine system <NUM> in <FIG>. More specifically, the memory <NUM> may include volatile memory, such as random-access memory (RAM), and/or non-volatile memory, such as read-only memory (ROM), optical drives, hard disc drives, or solid-state drives. Additionally, the processor <NUM> may include one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more general purpose processors, or any combination thereof. Furthermore, the term "processor" is not limited to just those integrated circuits referred to in the art as processors, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits, and other programmable circuits.

<FIG> is a graphical representation <NUM> of exit flow function to turbine exit Mn. The graphical representation <NUM> includes an X-axis <NUM> representing turbine exit axial Mn and a Y-axis <NUM> representing turbine exit flow function. The turbine exit flow function for a fixed last stage of a turbine of a gas turbine is a function of a flow component (Wx) or turbine exit flow, a pressure component (PT3) or total pressure, and a temperature component (TT3) or total temperature. As shown in plot <NUM> in the graphical representation <NUM>, the turbine exit flow function is strongly correlated to turbine exit Mn and may serve as turbine exit Mn surrogate in a non-MBC strategy. More specifically, the turbine exit Mn is highly proportional to the product of turbine exit flow and the square root of the turbine exit absolute temperature divided by the turbine exit pressure. In addition, the turbine exit Mn surrogate limit level functionally corresponds to an equivalent Mn based on cycle performance with the limit defined in surrogate space. The turbine exit Mn surrogate is capable of regulating the operating point to a limiting turbine exit Mn at least as well as (if not better) than utilizing the actual turbine exit Mn in a MBC strategy. In particular, the turbine exit Mn surrogate is robust enough to handle variation in ambient conditions, exhaust system design pressure drop variation, component performance variation, and control sensor uncertainty.

Turbine exit flow, total pressure, and total temperature at the turbine exit are not readily measured or available. However, turbine exit flow, total pressure, and total temperature have strong correlations to control measured parameters as illustrated in <FIG>. It should be noted that in certain embodiments, other parameters and/or additional parameters to those in <FIG> may be utilized in determining the turbine exit Mn surrogate. <FIG> is a graphical representation <NUM> of turbine exit flow to compressor discharge pressure. The graphical representation <NUM> includes an X-axis <NUM> representing compressor discharge pressure and a Y-axis <NUM> representing turbine exit flow. Since turbine exit flow is proportional to compressor inlet flow, there is a strong correlation between the turbine inlet pressure and compressor flow for a fixed design of compressor extractions and turbine first stage geometry. For a given combustion system, this can be extended to a show similarly strong proportionality between turbine inlet pressure and compressor discharge pressure. Plot <NUM> illustrates that the flow component or turbine exit flow has a strong correlation to the pressure at the compressor discharge. Thus, compressor discharge pressure (a measured parameter) may serve as a surrogate for turbine exit flow in calculating the turbine exit Mn surrogate.

<FIG> is a graphical representation of turbine exit temperature to exhaust temperature. The graphical representation <NUM> includes an X-axis <NUM> representing exhaust temperature and a Y-axis <NUM> representing turbine exit temperature (as measured in the exhaust section at a control exhaust temperature frame and adjusted for radial profile effects). Turbine exit total temperature is strongly related to a typical exhaust temperature measurement. They differ by the dilution effect of exhaust frame cooling introduced between the turbine exit and the control exhaust temperature measurement plane in the exhaust section. Plot <NUM> illustrates that the temperature component or turbine exit temperature has a strong correlation to the exhaust temperature as measured in the exhaust section. This is expected given that the exhaust temperature is the turbine exit temperature plus frame blower dilution. Thus, exhaust temperature (a measured parameter) may serve as a surrogate for turbine exit temperature in calculating the turbine exit Mn surrogate.

<FIG> is a graphical representation of turbine exit total pressure to exhaust pressure at exhaust section exit. The graphical representation <NUM> includes an X-axis <NUM> representing exhaust pressure at the exhaust section exit and a Y-axis <NUM> representing turbine exit total pressure. Turbine exit pressure is strongly related to the measured pressure at the exit of the exhaust section or exhaust diffuser section and correlated primarily by exhaust system pressure recovery. For a fixed design with the intended used of the surrogate over a limited range of turbine exit Mn conditions related to full load operation, variation in this pressure recovery will be fairly limited. These boundary conditions are related through the exhaust system pressure recovery and the range of interest will have limited variation in swirl angle and Mn. Plot <NUM> illustrates that the pressure component or turbine exit total pressure has a strong correlation to the exhaust pressure as measured at the exit of the exhaust section. Thus, exhaust pressure (a measured parameter) may serve as a surrogate for turbine exit total pressure in calculating the turbine exit Mn surrogate.

As noted above in <FIG>, turbine exit flow function is strongly correlated to turbine exit Mn and may serve as turbine exit Mn surrogate in a non-MBC strategy. Thus, a turbine exit Mn surrogate may be based on turbine pressure times the square root of the turbine exit absolute temperature. <FIG> is a graphical representation <NUM> of turbine exit Mn surrogates (derived from components of a turbine exit flow function or measured parameters strongly correlated to the components of the turbine exit flow function) to turbine exit Mn. The graphical representation <NUM> includes an X-axis <NUM> representing turbine exit axial Mn and a Y-axis <NUM> representing turbine exit Mn surrogate (PR*Sqrt(T)), where PR equals pressure ratio and T equals temperature. Plot <NUM> represents the turbine exit Mn surrogate as calculated for the components of a turbine exit flow function (e.g., as gathered in a system that utilizes an MBC to derive the values for turbine exit total pressure (PT3) and turbine exit absolute temperature (TT3)) relative to turbine exit axial Mn. Plot <NUM> represents the turbine exit Mn surrogate as calculated utilizing measured parameters strongly correlated (and utilized as surrogates) to the components of the turbine exit flow function such as turbine exhaust temperature (Tx) as measured in the control exhaust temperature measurement plane in the exhaust section and the exhaust pressure (Px) as measured at the exit of the exhaust section relative to turbine exit axial Mn. As depicted in the graphical representation <NUM>, utilizing the surrogate measured parameters for the turbine exit Mn surrogate in plot <NUM> are as correlated to turbine exit axial Mn as utilizing the components of turbine exit flow function in plot <NUM>. Thus, a turbine exit Mn surrogate derived from the following equation (PCD/PX)*(TTXM_R), where PCD represents the measured compressor discharge pressure and TTXM_R represents the Rankine adjusted turbine exhaust temperature, is strongly related to turbine exit Mn and may provide a reasonable boundary control surrogate.

<FIG> is a graphical representation <NUM> of turbine exit Mn surrogate (Y-axis <NUM>) (derived from measured parameters strongly correlated to components of a turbine exit flow function) to turbine exit Mn (X-axis <NUM>) over multiple load sweeps. The multiple load sweeps were conducted with a gas turbine system over based Mn sweeps at different ambient pressure conditions (e.g., ranging from <NUM> to <NUM> pound-force per square inch (psia) or approximately <NUM> to <NUM> Kilopascals (kPa) assuming normal cycle performance. In addition, the multiple load sweeps were conducted with the gas turbine system over different extreme cold ambient temperatures (e.g., ranging from -<NUM> to -<NUM>°F or approximately -<NUM> to -<NUM>) expected for turbine exit Mn control with nominal cycle performance and Tfire suppression. Plot <NUM> illustrates that turbine exit Mn surrogate (derived from measured parameters strongly correlated to components of a turbine exit flow function) has a strong correlation to the turbine exit Mn.

<FIG> is a functional block diagram of an embodiment for turbine exit Mn boundary control utilizing a turbine exit Mn surrogate. Dashed section <NUM> represents control code for the surrogate turbine exit Mn and dashed section <NUM> represents control code for IGV con to Min, Max, and Path constraints. As depicted in the dashed section <NUM>, a turbine exit Mn limit (Mn,x Limit) is provided to a control curve <NUM> or table (relating the turbine exit Mn surrogate (Mn,x surrogate) to the turbine exit Mn limit) to generate a turbine exit Mn surrogate limit (Mn,xSurrogate Limit). The turbine exit surrogate limit (which may be constant limit or a variable limit) is provided to a comparator <NUM>. Also, as depicted in the dashed section <NUM>, the measured compressor discharge pressure (Pcd) is divided (as indicated at reference numeral <NUM>) by the measured exhaust pressure at the exit of the exhaust section to obtain the turbine pressure ratio (TPR). The turbine exhaust temperature (Tx) as measured in the control exhaust temperature measurement plane in the exhaust section is provided to a comparator <NUM> that adds the standard day temperature (e.g., <NUM>) to provide an absolute turbine exit temperature. The square root (as indicated by reference numeral <NUM>) of the output of the comparator <NUM> provides the Rankin turbine exhaust temperature (TxRankine) which is multiplied (as indicated by reference numeral <NUM>) by the TPR obtain the turbine exit Mn surrogate. The turbine exit Mn surrogate is provided to the comparator <NUM> along with the turbine exit surrogate limit to generate an output that is provided as an input to a controller (e.g., proportional integral controller) <NUM> in the dashed section <NUM>. The controller provides a compressor IGV, closed loop max open effector constraint (IGVMn,x) derived from the turbine exit Mn surrogate to an IGV loop prioritization and select logic <NUM>. In addition, other max open IGV constraints or IGV requests from other boundaries, schedules, and path (e.g., maximum compressor discharge temperature, compressor operability, aero constraints, mechanical limits, etc.) are provided to the IGV loop prioritization and select logic <NUM>. The IGVMn,x and the other max open IGV contraints go thru a priority select and the IGV loop prioritization and select logic <NUM> outputs an IGV setting or IGV request.

<FIG> is a flow diagram of a method <NUM> for utilizing a turbine exit Mn surrogate for controlling a turbine engine system. The steps of the method <NUM> are performed by a controller of a gas turbine system (e.g., controller <NUM> in <FIG>). The method <NUM> includes receiving feedback from sensors coupled to components of a gas turbine system (block <NUM>). Feedback is received from sensors coupled to a compressor and a turbine, and optionally to an exhaust section. The feedback includes measured parameters such as compressor discharge pressure, exhaust section exit pressure, and exhaust temperature (e.g., measured along a control exhaust temperature measurement plane in the exhaust section). The measured parameters correlate to (and serve as surrogates) to parameters related to turbine exit flow function that would otherwise be utilized to directly calculate the turbine exit Mn surrogate but that are not measured on the gas turbine system or are not available. The method <NUM> also includes calculating a surrogate value for the turbine exit Mn based on the feedback from the sensors (block <NUM>). The surrogate value for the turbine exit Mn is calculated based on the measured compressor discharge pressure, exhaust section exit pressure, and exhaust temperature as described above. The surrogate value for the turbine exit Mn serves as boundary control for the gas turbine system. The method <NUM> further comprises utilizing the surrogate value for the turbine exit Mn to derive a control action for the gas turbine system (block <NUM>). The control action is derived as described above in <FIG>. The method <NUM> even further includes providing a control signal (based on the surrogate value) to an actuator coupled to the IGV within the compressor to control the actuator (block <NUM>). The turbine exit Mn surrogate may be utilized in a non-MBC strategy. In certain embodiments, the turbine exit MN surrogate on gas turbine systems (e.g., legacy systems) that include MBC but lack MBC for turbine exit Mn.

The non-MBC strategy for utilizing a surrogate for turbine exit Mn may also be utilized for other parameters that provide boundary control. <FIG> is a flow diagram of a method <NUM> for utilizing a surrogate for a parameter for direct boundary control for controlling a turbine engine system. One or more steps of the method <NUM> may be performed by a controller of a gas turbine system (e.g., controller <NUM> in <FIG>). The method <NUM> includes receiving feedback from sensors coupled to components of a gas turbine system (block <NUM>). For example, feedback may be received from sensors coupled to a compressor, a combustor, a turbine, an exhaust section, or other component of a gas turbine system. The measured parameters may correlate to (and serve as surrogates) to parameters related to a surrogate for a desired boundary control parameter that would otherwise be utilized to directly calculate the surrogate but that are not measured on the gas turbine system or are not available. The method <NUM> also includes calculating a surrogate value for the desired boundary control parameter based on the feedback from the sensors (block <NUM>). The method <NUM> further comprises utilizing the surrogate value for the desired boundary control parameter to derive a control action for the gas turbine system (block <NUM>). The method <NUM> even further includes providing a control signal (based on the surrogate value) to a component of the gas turbine system or an actuator coupled to the component to control the component or the actuator (block <NUM>).

Technical effects of the disclosed embodiments include providing an accurate and robust (as well as easily constructed) turbine exit Mn surrogate that may be utilized for limit control on heavy duty gas turbines that do not have MBC control. In certain embodiments, the non-MBC strategy utilizing the turbine exit Mn surrogate may also be utilized on gas turbine systems that have an onboard model where the model lacks any provision for turbine exit Mn control. The utilization of the turbine exit Mn surrogate may enable hardware upgrades on gas turbine systems that are more cost effective than a full MBC upgrade to support the hardware upgrade. The turbine exit Mn surrogate is capable of regulating the operating point to a limiting turbine exit Mn at least as well as (if not better) than utilizing the actual turbine exit Mn in a MBC strategy. In particular, the turbine exit Mn surrogate is robust enough to handle variation in ambient conditions, exhaust system design pressure drop variation, component performance variation, and control sensor uncertainty.

This written description uses examples to disclose the subject matter, including the best mode, and also to enable any person skilled in the art to practice the subject matter, including making and using any devices or systems and performing any incorporated methods. The scope of the herein claimed subject matter is defined by the claims, and may include other examples that occur to those skilled in the art.

Claim 1:
A system, comprising:
a gas turbine system (<NUM>) comprising a compressor (<NUM>), combustor (<NUM>), a turbine (<NUM>), and an exhaust section (<NUM>);
a plurality of sensors (<NUM>) coupled to components of the gas turbine system (<NUM>);
a controller (<NUM>) communicatively coupled to the gas turbine system (<NUM>) and the plurality of sensors (<NUM>) and configured to control operations of the gas turbine system (<NUM>), wherein the controller (<NUM>) is configured to calculate a surrogate value for turbine exit Mach number based on the feedback from the plurality of sensors (<NUM>) and to utilize the surrogate value to derive a control action for the gas turbine system (<NUM>); wherein
the plurality of sensors (<NUM>) are coupled to the compressor (<NUM>) and the turbine (<NUM>); and
the feedback comprises measured parameters for compressor discharge pressure, exhaust section exit pressure, and exhaust temperature adjusted for radial profile effects; characterized in that
the measured parameters correlate to parameters related to turbine exit flow function that would otherwise be utilized to directly calculate the turbine exit Mach number but that are not measured on the gas turbine system (<NUM>).