Wing Performance Monitor

Abstract

An airfoil performance monitor includes a housing mounted on a low-pressure surface of an airfoil and defining a pitot tube pressure port and a static pressure port; an airspeed-dependent sensor for sensing airflow impinging on the pitot tube port and generating a digital airflow signal indicative of airflow turbulence; and a controller for deriving a turbulence intensity ratio by filtering a turbulence value calculated from the digital airflow signal.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and all benefits of U.S. Provisional Patent Application No. 62 / 887,418, filed on August 15, 2019, the entire contents of which are expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates to an airfoil performance monitor, and more particularly, such a monitor capable of sensing conditions at an airfoil working surface. Background Art

[0004] Aircraft are equipped with a variety of sensors that provide real-time feedback on various operator controls. For example, sensors can be surface-mounted to a flying wing to measure and provide data indicating lift and drag on the wing's airfoil. The measurements made by these sensors can explain the effects of contamination on any environmental conditions the aircraft, and specifically the wing, may experience. Sensors placed on the aircraft's wings allow actionable decisions to be made to improve the performance of the wing's airfoil. These airfoil performance sensors, designed and certified for aircraft wings, function as critical life-saving sensors for quantifying the effects of icing.

[0005] Besides fixed-wing aircraft, airfoils are used for a variety of purposes in many other applications. For example, the blades of a wind turbine are essentially airfoils. Air flowing over the airfoils creates lift on the blades, which in turn rotates the wind turbine, ultimately driving a generator, which generates electricity. Currently, the overall performance of a wind turbine is typically monitored using a "power curve," a measure of the power generated by the turbine, typically correlated with environmental sensors such as local wind speed. This method provides a rough overview of the performance of the entire wind turbine, but provides little insight into the specific causes of any performance losses that may be caused by issues with aerodynamics, mechanical, electrical, or control systems. Furthermore, power curves do not provide direct information about the possible aerodynamic degradation experienced by one or more individual rotor blades. The causes of such degradation may be numerous, including but not limited to manufacturing defects, leading edge erosion (caused by sand, water, or debris), acute damage (caused by hail, lightning, or bird strikes), or contamination from heavy rain, freezing rain, or accumulated ice deposits. Icing is a particularly serious problem because its aerodynamic effects depend on many factors (e.g. ice thickness, chordwise extent, vertical extent, spanwise extent, roughness, etc.), making them essentially unpredictable. The current state of the art includes the use of ice detectors and even some ice thickness sensors, but these are unable to predict the effect of the measured ice on the performance of the airfoil. Similar limitations apply to theoretical work to determine the effects of icing, such as computational fluid dynamics techniques. Therefore, the common approach to operating in icing conditions is to shut down the wind turbines, which has serious operational and financial consequences because the entire wind farm may be affected and shut down simultaneously due to severe icing conditions. All of these factors will have an immediate detrimental effect on the performance of individual wind turbines, but they can also lead to a shortened lifetime of the entire wind farm, significantly increased maintenance costs, and increased operating costs because these problems are difficult to isolate and solve with existing technologies. Summary of the Invention

[0006] The present invention relates to an airfoil performance monitor designed to overcome the shortcomings of the related art. Therefore, one embodiment of the airfoil performance monitor of the present invention includes a housing that can be mounted on the low-pressure surface of an airfoil. The housing includes at least one pitot tube pressure port for determining the total pressure at the airfoil performance monitor and at least one static pressure port for determining the static pressure at the airfoil performance monitor. The airfoil performance monitor includes at least one airspeed-related sensor that senses the total pressure at the airfoil performance monitor through the pitot tube pressure port and generates a digital airflow signal indicative of the dynamic pressure at the airfoil performance monitor. A controller derives a turbulence intensity ratio by processing and filtering a turbulence value calculated from the digital airflow signal.

[0007] The present invention also relates to an airfoil performance monitoring system comprising at least one airspeed-dependent sensor disposed on a low-pressure surface of an airfoil. The airfoil performance monitoring system includes at least one pitot tube pressure sensing port for determining a total pressure at the airfoil performance monitor, and at least one static pressure port disposed on the low-pressure surface of the airfoil for determining a static pressure at the airfoil performance monitor. The at least one airspeed-dependent sensor measures the total pressure at the pitot tube pressure port and generates a digital airflow signal indicative of a dynamic pressure measured at the at least one pitot tube pressure port.

[0008] Signals generated from the airspeed-dependent sensors are processed into digital airflow signals indicative of airflow turbulence. Furthermore, the present invention's airfoil performance monitoring system includes one or more inertial sensors that measure acceleration or other motion in up to three orientations relative to a mounting point. A controller derives the turbulence intensity by normalizing the measured turbulence intensity with the steady-state airflow signal, thereby generating a dimensionless turbulence intensity ratio of the turbulent component to the steady-state signal component. The controller also filters the signals from the airflow-dependent sensors using a frequency obtained from the inertial sensors to eliminate the effects of unwanted blade vibration on the turbulence intensity calculation.

[0009] The controller uses the processed turbulence intensity signal to monitor the aerodynamic performance of the airfoil and prevent exceeding a preset turbulence intensity threshold which would indicate an airfoil "stall" as discussed below.

[0010] Furthermore, the present invention relates to a blade performance monitoring system for a wind turbine. The system includes a housing mounted on a low-pressure surface of the blade. The housing defines at least one pitot tube pressure port and at least one static pressure port. At least one airspeed-related sensor is disposed on the low-pressure surface of the blade. Signals generated by the airspeed-related sensor as a result of airflow measured through the pitot tube static pressure port are processed into digital signals indicative of airflow turbulence. One or more inertial sensors measure blade pitch angle and motion in up to three directions from its mounting location based on mechanical motion mechanically transmitted to the housing by the blade. A controller, responsive to the blade pitch angle and the frequency and amplitude of acceleration from the one or more inertial sensors, filters a turbulence value using acceleration and correlates the filtered airflow turbulence signal with a steady-state airflow signal to derive a turbulence intensity ratio, thereby generating data that serves as a basis for commands for adjusting the blade pitch angle using a rotor control system.

[0011] The present invention also relates to a wind turbine comprising one or more blades that rotate a shaft, a generator that is connectable to the shaft via a gearbox and converts and stores energy, and a housing mounted on the low-pressure side of an airfoil. The housing defines at least one pitot tube pressure port for measuring total pressure at an airfoil performance monitor and at least one static pressure port for measuring static pressure at the airfoil performance monitor. At least one airspeed-related sensor is in fluid communication with the at least one pitot tube pressure port and converts the airflow measured by the pitot tube port and generates a digital airflow signal indicative of turbulence in the airflow. One or more inertial sensors are disposed on the low-pressure side of one of the blades and measure blade pitch angle and acceleration in up to three directions from a mounting location on the one or more blades, the acceleration being frequency and amplitude data. A controller derives a turbulence intensity ratio by correlating a filtered turbulence signal with a steady-state airflow signal and generates a command for adjusting the blade pitch angle using a rotor control system.

[0012] Other objects, features and advantages of the present invention will be readily apparent as they will be better understood after reading the ensuing description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a perspective view of a wind farm having a plurality of wind turbines;

[0014] Figure 2 is a side view of a wind turbine and rotor assembly;

[0015] Figure 2A is an enlarged cross-sectional side view depicting an airfoil defined by a turbine blade;

[0016] Figure 3A is a schematic diagram of a rotor of a wind turbine having blades with a mast-mounted sensor assembly;

[0017] Figure 3B is a schematic diagram of a mast-mounted sensor assembly;

[0018] Figure 4 is a perspective view of a mounting interface for a mast-mounted sensor assembly;

[0019] Figure 5 is a cross-sectional view of one embodiment of a mast-mounted sensor assembly of the present invention;

[0020] Figure 6 is a perspective view of another embodiment of a mast-mounted sensor assembly;

[0021] Figure 7 is a functional block diagram of a mast-mounted sensor assembly;

[0022] Figure 8 is a flow chart depicting the operation of a mast-mounted sensor assembly; and

[0023] Figure 9 is a flow chart depicting the operation of a heater for a mast-mounted sensor assembly. DETAILED DESCRIPTION

[0024] As described in more detail below, the present invention relates to an airfoil performance monitor. As a means of illustrating the inventive features of the present invention, the performance monitor is described in relation to use with a wind turbine. However, those skilled in the art will appreciate from the following description that this is merely one representative example of how the performance monitor of the present invention can be used to monitor and track environmental and operational performance conditions at an airfoil used in any number of applications.

[0025] Considering this representative environmental application, Figure 1 A representative perspective view of a wind farm 10 having a plurality of wind turbines 12 is depicted. Wind turbines 12 are arranged in an array 14. Wind turbines 12 convert kinetic energy from wind into electrical energy through an electromechanical system. As will be described in more detail below, wind flows through each wind turbine 12 within array 14, which causes blades 16 of each wind turbine 12 to rotate. Rotating blades 16 convert kinetic energy from the wind into mechanical power, which can be used to rotate a generator that produces electricity that can be stored as electrical energy from wind turbines 12 or transmitted to a power grid. Thus, each of the plurality of wind turbines 12 can be arranged in an array 14 based on wind patterns to enhance and maximize energy conversion within wind turbines 12.

[0026] As shown, the array 14 of multiple wind turbines 12 is oriented so that each wind turbine 12 has sufficient spacing to allow the blades 16 to rotate, while maximizing the number of individual wind turbines 12 within the array 14. In other words, the distance 18 between each turbine 12 can be set to maximize the number of wind turbines 12 arranged within the array 14 of multiple wind turbines 12. Furthermore, in order for the blades 16 of the wind turbines 12 to rotate, the plane of rotation of the wind turbines 12 needs to be oriented in a direction substantially perpendicular to the direction of the wind. Although described as being substantially perpendicular, each wind turbine 12 can be oriented within a range of angles depending on the direction and pattern of the wind flowing through the wind farm 10 to allow the blades 16 to rotate with optimal efficiency.

[0027] The array 14 of wind turbines 12 may be arranged in a shape intended to optimize the number of wind turbines 12 within the array 14 of the wind farm 10. The shape of the array 14 of wind turbines 12 positioned and arranged on the wind farm 10 may be based, at least in part, on the distance 18 (as described above) required between each other wind turbine 12 to allow the blades 16 to fully rotate, as well as the direction and pattern of wind passing through the wind farm 10. Additionally, the fore-aft distance 20 between each turbine 12 within the plurality of turbines 12 may influence the shape and orientation of the array 14 of the plurality of wind turbines 12. For example, minimizing the fore-aft distance 20 and the distance 18 between each wind turbine 12 may maximize the number of wind turbines 12 positioned within the array 14.

[0028] Likewise, optimizing the fore-aft distance 20 and the distance 18 between each wind turbine 12 may influence the shape of the array 14 to maximize the efficiency of the wind farm 10. Optimizing the fore-aft distance 20 between each wind turbine 12 may also take into account the strength, direction, and pattern of the wind across the wind farm 10. In other words, the direction and pattern of the wind blowing across the array 14 of wind turbines 12 may further provide data indicative of the optimal fore-aft distance 20 between each wind turbine 12 within the array 14 to maximize the efficiency of each wind turbine 12 in the array 14.

[0029] refer to Figure 2 , depicts a side view of a single wind turbine 12. Wind turbine 12 may include a generally vertical tower 13 that supports a housing (sometimes called a nacelle) 15, which in turn supports the turbine's internal components, such as a generator 32, a gearbox 30, associated shafts, a yaw drive, a yaw motor, etc. Housing 15 includes a rotor 24, which includes a hub 33 to which wind turbine blades 16 are mounted. Figure 2 The wind turbines 12 shown in FIG. 1 are shown with individual blades 16. Each turbine 12 may include a plurality of blades 16, with an optimal number of blades 16 being determined to maximize the energy generation efficiency of the wind turbine 12. The number of blades 16 arranged on the wind turbines 12 may also be determined based on the direction and pattern of wind blowing through the wind farm 10 to maximize the energy generation efficiency of the wind turbines 12 across the array 14 of wind turbines 12. The blades 16 are arranged on the wind turbines 12 so that, in response to wind flowing through the wind turbines 12, the blades 16 rotate about a horizontal axis 22 that intersects a centerline 25 of a rotor 24 of the wind turbine 12.

[0030] Specifically, wind flowing through each blade 16 is separated so that the blade 16 defines a high-pressure side 27 and a low-pressure side 29. The blades 16 rotate in response to a pressure differential between the high-pressure side 27 and the low-pressure side 29. For example, the pressure differential from the high-pressure side 27 to the low-pressure side 29 provides the force required to accelerate the blades 16 on the rotor 24 to rotate the shaft 28, which converts mechanical torque from wind energy into electrical energy via a generator 32, as will be described in more detail below. The rotor 24 can be controlled by a rotor control system 23 that is adapted to adjust the position and orientation of the blades 16 relative to the centerline 25 of the rotor 24. For example, the rotor control system 23 can adjust the pitch angle 36 of the blades 16 to optimize the performance of the wind turbine 12.

[0031] Rotor 24 rotates shaft 28, which is disposed within housing 15 of wind turbine 12. Shaft 28 can transmit torque from rotor 24 through a gearbox 30 connected to generator 32, or it can be directly connected to generator 32. Generator 32 converts the torque into electrical energy, which can be stored for later use or transmitted to a power grid. Thus, as described, when wind flows through wind turbine 12 and rotates blades 16, rotor 24 rotates shaft 28, transmitting power to generator 32, which generates electrical energy for use. The more revolutions shaft 28 undergoes as a result of blades 16 rotating rotor 24, the more electrical energy generator 32 generates. In other words, the performance of blades 16 determines the amount of electrical energy converted by generator 32, and providing adjustments to the orientation 34 of blades 16 and the pitch angle 36 of each blade 16 can further help improve the performance of each blade 16. Furthermore, in at least one other embodiment, the cone angle 38 between each blade 16 can be optimized based on the strength, direction, and pattern of the wind blowing through wind turbine 12.

[0032] The pitch angle 36 of each blade 16 helps the blade 16 rotate the rotor 24. The inventors have discovered that it is advantageous to monitor the pitch angle 36 of each blade 16 and provide adjustments to maximize efficiency. For example, as wind flows through the wind turbine 12 and across the blades 16 of the wind turbine 12, the pitch angle 36 of the blade 16 forces air around the flaps 40 of the blade 16, as previously described. The movement of air around the flaps 40 of the blade 16 pushes the blade 16 around the rotor 24. Thus, the pitch angle 36 of the blade 16 helps determine the efficiency and yield of the conversion of mechanical power transmitted through the rotor 24 and shaft 28 into electrical energy converted by the generator 32.

[0033] Each blade 16 includes a span length 42 and a chord length 43. The chord length 43 is the length of the cross-section of the blade 16 measured from the leading edge 45 to the trailing edge 47 of the cross-section of the blade 16. As wind flows over the blades, the forces generated on the blades cause a torque to be applied to the rotor 24, which rotates a shaft 28 connected to a generator. The wind turbine control system adjusts the pitch angle 36 of the blades 16 to optimize the performance of the wind turbine under existing wind conditions while keeping the wind turbine within its design operating limits (e.g., RPM, structural loads, etc.). As will be discussed in more detail below, the airfoil performance monitor and system of the present invention disposed on the blades 16 assists the control system in improving the overall performance of the wind turbine 12 under a wide range of operating conditions, including the presence of airfoil degradation, such as degradation caused by leading edge erosion or icing, typically in the presence of airfoil degradation. Figure 2A Indicated by 49.

[0034] Figure 3A and 3B A perspective view of blades 16 detached from rotor 24 and wind turbine 12 is depicted. Figure 3A An operational embodiment is depicted in which a blade 16 has four airfoil performance monitors 44 disposed between a blade root 46 and a blade tip 48, and in which the blade 16 is attached to the rotor 24 at the root 46. The blade 16 is attached to the rotor 24 at the root 46 using one or more fasteners (not shown). Alternatively, the blade 16 may be attached to the rotor 24 at the root 46 using any known mechanical fastening technique. The airfoil performance monitors 44 may also be referred to as an airfoil performance monitoring system 44. As will be described in more detail below, the airfoil performance monitors 44 may be mounted on a low pressure surface 52 of the airfoil 40. Securing the airfoil performance monitors 44 on the low pressure surface 52 of the airfoil 40 allows the airfoil performance monitors 44 to provide data indicative of the performance of the blade 16 of the wind turbine 12.

[0035] As shown, the blade performance monitors 44 may be spaced apart along the blade 16 between the blade root 46 and the blade tip 48. The blade performance monitors 44 may be affixed to the blade 16 at different predetermined locations 54, or may be spaced apart according to a set predetermined pattern (not shown). For example, depending on the shape and design of the wind turbine blades 16 or the pattern, direction, and intensity of the wind, as well as the design of the array 14 of wind turbines 12, the blade performance monitors 44 may be affixed at predetermined locations 54 that indicate a data set provided to the blade performance monitors 44 that can be used to optimize the performance of the blades 16 and wind turbine 12. The predetermined locations 54 of the blade performance monitors 44 may be determined through computational fluid dynamics analysis and / or through experimentation during initial setup to ensure that the predetermined locations 54 provide the blade performance monitors 44 with the best available data to optimize the performance of the wind turbine 12.

[0036] Alternatively, the blade performance monitors 44 may be evenly spaced between the root 46 and the tip 48 of the blade 16. For example, the blade performance monitors 44 may define an equal distance 56 between the center 58 of each blade performance monitor 44 disposed on the blade 16. Providing an equal distance 56 between the center 58 of each blade performance monitor 44 allows the blade performance monitor 44 to collect data in an evenly distributed section 60 on the blade 16. Collecting data in the distributed section 60 provides performance information for the blades 40 of the blade 16 as wind acts to rotate the blade 16 about the rotor 24. This data, indicative of the performance of the blade 16 at each section 60, allows the blade performance monitor 44 to provide an accurate analysis of the interaction between the blade 16 and the wind acting on the blade 16, and similarly helps optimize the performance and efficiency of each individual blade 16 on the wind turbine 12 to generate greater electrical energy from the wind farm 10.

[0037] As mentioned above, Figure 3A The embodiment shown in the figure includes four blade performance monitors 44 fixed to the blade 16. However, this is merely exemplary. The blade 16 can adopt any number of blade performance monitors 44 fixed between the root 46 and the tip 48 of the blade 16. The number of blade performance monitors 44 fixed to the blade 16 can depend on the shape and design of the wind turbine blade 16, and / or the direction, pattern and intensity of the wind interacting with the blade 16. The number of blade performance monitors 44 can also depend on the amount of data required to calculate and optimize the performance of the blade 16 and the wind turbine 12. For example, a single blade performance monitor 44 can provide enough data and processing power to effectively calculate and adjust the performance of the blade 16, thereby optimizing the generation of wind energy. Similarly, as shown in the figure, multiple blade performance monitors 44 can provide additional data to improve the sensitivity of the overall performance of the blade performance monitoring system 44.

[0038] refer to Figure 3B , depicts a schematic diagram of one embodiment of an airfoil performance monitor 44. Figure 4As shown, the airfoil performance monitor 44 includes a housing or mast 50. The mast 50 defines a fin portion 62 and a base portion 64. The fin portion 62 extends from the base portion 64 in a direction perpendicular to the airfoil 40. The base portion 64 is attached to the airfoil using mechanical fasteners (not shown) that extend through a plurality of holes 66 defined by the base portion 64. However, it will be understood by those skilled in the art that the base portion 64 can be mounted to the airfoil using any conventional fastening mechanism. The fin portion 62 is attached to the base portion 64 by welding, molding, bonding or any other known mechanical joining technology so that the fin portion 62 is sealed to the base portion 64. Alternatively, the fin portion and the base portion can be formed as an integral one-piece component. The base portion 64 can be substantially solid and formed to provide as much surface area contact as possible between the base portion 64 and the airfoil 40 to ensure greater stability of the mast 50 on the blade 16. The fin portion 62 is formed to be substantially hollow and may be in the shape of a streamlined airfoil so that air flows over each side 68 of the fin portion 62 as shown. Figure 3B Alternatively, the fin may be manufactured as an integral part of the wind turbine blade 16, in which case the fin portion 62 would be integrated into the wind turbine blade 16 without the base portion 64 being attached.

[0039] Figure 4 A perspective view of the fin housing or mast 50 of the airfoil performance monitor 44 is depicted, which includes a fin 62 and a base portion 64. The fin portion 62 is designed to house the components of the airfoil performance monitor 44. For example, Figure 5 A schematic perspective cross-sectional view of one embodiment of an airfoil performance monitor 44 is depicted as a single integrated unit housing all necessary electronics within a mast. Specifically, Figure 5 The interior 76 of the combined airfoil performance monitor 44 is depicted. Figure 5 As described in more detail, the fin portion 62 is designed to house at least one or more inertial sensors 70 (such as accelerometers), one or more airspeed related sensors 78, a controller 72, and associated electronics to provide data indicative of the performance and efficiency of the airfoils 40 of the blades 16 of the wind turbine 12.

[0040] exist Figure 5 In one embodiment shown, the fin portion 62 defines at least one pitot tube pressure port 74 and at least one static pressure port 75. However, the airfoil performance monitor 44 of the present invention may include a plurality of pitot tube ports 74 and a plurality of static pressure ports 75. For example, in Figure 5 In the embodiment shown, the pitot tube pressure port 74 is located on the front or leading edge 77 of the fin portion 62, while the static pressure port 75 is located on the trailing edge 79 of the fin portion 62. Figure 4As shown, the airfoil performance monitor 44 may include a plurality of static pressure holes 75. One of the static pressure holes may be located on the side 68 of the fin portion 62, and another may be located on the trailing edge 79 of the fin portion 62. These embodiments are merely exemplary, and the number and location of the pitot tube holes 74 and the static pressure holes 75 may vary depending, for example, on the strength, pattern, and direction of airflow at the location of the mast 50. The size and shape of the pitot tube holes 74 and the static pressure holes 75 may be adjusted to adjust the exposure of the airflow-dependent sensors and to adjust the sensitivity required to calculate the performance and efficiency of the blades 16 of the wind turbine 12. The pitot tube pressure holes 74 and the static pressure holes 75 may also be positioned at a 45-degree angle relative to a horizontal plane passing through the fin portion 62 to facilitate drainage of any liquid, such as water from rain or melting snow or ice, from the mast 50.

[0041] Each pitot tube pressure port 74 is in fluid communication with at least one airspeed-related sensor 78. The static pressure port 75 may also be in fluid communication with at least one airspeed-related sensor 78. Alternatively, the static pressure port 75 may be in fluid communication with the interior 76 of the mast 50, such that the internal pressure of the mast 50 reflects the external static pressure. In this configuration, the static pressure port is simply open to the interior 76 of the mast 50 to balance the internal pressure with the external static pressure. The pitot tube ports 74 and their associated airspeed-related sensors 78 are used to measure the total pressure impinging on the pitot tube ports 74. The static pressure port 75 is used to measure the static pressure impinging on the static pressure port 75. As will be discussed in more detail below, the static pressure measured at the static pressure port 75 is subtracted from the total pressure measured at the pitot tube pressure port 74 to obtain the dynamic pressure.

[0042] Continue to refer Figure 5 , one or more inertial sensors 70 and one or more airspeed related sensors 78 are shown stacked above the controller 72 within the interior 76 of the fin portion 62 of the mast 50. Figure 5 In the illustrated embodiment, the inertial sensor 70 may be an accelerometer. However, one of ordinary skill in the art will appreciate that any type of inertial sensor suitable for the purposes disclosed herein is acceptable. Stacking the inertial sensor 70, the airspeed-related sensor 78, and the controller 72 allows the mast 50 to efficiently package the electronics required to optimize the performance and efficiency of the wind turbine 12.

[0043] An inertial sensor in the form of an accelerometer 70 can be positioned above the airspeed-related sensor 78. In the embodiment shown, the airspeed-related sensor 78 is positioned above the controller 72. However, as described above, those skilled in the art will appreciate that these components can be arranged relative to each other in any number of configurations without departing from the scope of the present invention. This arrangement is merely exemplary. In at least one other embodiment, the airspeed-related sensor 78 can be positioned above the accelerometer 70, which is positioned above the controller 72. Similarly, the controller 72 can be stacked above both the accelerometer 70 and the airspeed-related sensor 78. The combination and orientation of the accelerometer 70, airspeed-related sensor 78, and controller 72 can be optimized based on sensor type, efficiency, and performance requirements. For example, the airspeed-related sensor 78 can be positioned and stacked within the interior 76 of the mast 50 in an orientation such that the airflow measured through the pitot tube aperture 74 in the mast 50 provides accurate airspeed-dependent data sensed by the airspeed-related sensor 78. In a similar manner, the accelerometer 70 may be positioned and stacked within the interior 76 of the mast 50 in an orientation such that the angle or pitch of the airfoil performance monitor 44 provides acceleration data of the blade 16 accurately sensed by the accelerometer 70. Similarly, the controller 72 may be arranged and stacked within the interior 76 of the mast 50 in an orientation that provides for efficient data processing and transmission.

[0044] The airspeed-related sensor 78 may be a pressure sensor. The pressure sensor used as the airspeed-related sensor 78 may be a sensor with a high-frequency response, such as, but not limited to, a piezoresistive film sensor. One of ordinary skill in the art may also consider any other type of pressure sensor suitable for measuring different airflow pressures or velocities, such as sealed and non-sealed ones. Similarly, an inertial sensor (such as an accelerometer 70) may be a sensor for measuring the vibration of the blade 16. The accelerometer 70 may be a high-impedance piezoelectric sensor or a low-impedance piezoelectric sensor. As described above, the accelerometer 70 may be replaced with or supplemented by an alternative inertial measurement sensor to also include a 6-axis or 3-axis gyroscope suitable for measuring vibrations from the blade 16 through the mast 50. The operation of the inertial sensor 70, the airspeed-related sensor 78, and the controller 72 will be explained in more detail with reference to other figures.

[0045] Figure 5The illustrated airfoil performance monitor also includes a heater element 80. The heater element 80 may be supported within the interior 76 of the mast 50 on either side of the accelerometer 70, the airspeed-related sensor 78, and the controller 72. Although illustrated and described as being positioned on either side of the accelerometer 70, the airspeed-related sensor 78, and the controller 72, the heater element 80 may be a single heater element 80 positioned on a single side of the accelerometer 70, the airspeed-related sensor 78, and the controller 72. The heater element 80 may be any element suitable for radiating heat into the mast 50, such as, but not limited to, a resistive heating element 80 that generates heat in response to an electrical current. The heater element 80 is configured to prevent ice from accumulating on the mast 50, the accelerometer 70, the airspeed-related sensor 78, and the controller 72 during inclement weather conditions and blocking the pitot tube port 74 and the static pressure port 75.

[0046] The mast 50 may also include a power supply 82 disposed within the interior 76 of the mast 50. The power supply 82 may be located on a single side of the interior 76 of the mast 50 or disposed on either side of the interior 76 of the mast 50, depending on the amount of power required. The power supply 82 is adapted to provide power to the accelerometer 70, the airspeed-related sensor 78, and the controller 72 according to their required power usage. The power provided by the power supply 82 may be optimized based on the type of accelerometer 72, the airspeed-related sensor 78, the heater 80, and the processing requirements of the controller 72.

[0047] Figure 6 Another embodiment of the blade performance monitor 44 is depicted in which the controller 72 is separate from the accelerometer 70 and the airspeed-related sensor 78. By separating the controller 72 from the accelerometer 70 and the airspeed-related sensor 78, a smaller footprint for the mast 50 can be achieved. Furthermore, because the controller 72 is separate from the accelerometer 70 and the airspeed-related sensor 78, the mast 50 has greater installation flexibility on the blades 16 of the wind turbine 12 based on the smaller footprint. Specifically, in Figure 6 In the embodiment shown, the mast 50 may include a pitot tube port 74 and a static pressure port 75, an accelerometer 70, and an airspeed related sensor 78. The controller 72 may be located remotely from the mast 50. Figure 6 The mast 50 shown. As shown, the controller 72 is set below the mast 50. This is only exemplary and indicates that the controller 72 is away from the mast 50. Similarly, Figure 6 Another embodiment of the airfoil performance monitor 44 is depicted that allows the mast 50 to have a smaller footprint, thereby making the mast 50 easier to install on the blade 16 .

[0048] refer to Figure 7, depicts a functional block diagram of the operation of the airfoil performance monitor 44 . Figure 7 The functional block diagram shown in depicts the interaction between the accelerometer 70, the airspeed related sensor 78 disposed within the mast 50, the controller 72, and the display 84. Figure 7 In the illustrated embodiment, it can be seen that the mast 50 includes an airspeed-related sensor 78, an accelerometer 70, and a heater element 80. As will be described in more detail with reference to other figures, the heater element 80 can be operated as a closed loop with a switch 86, such that the switch 86 is used to regulate the heat from the heater element 80. For example, as shown, the heater element 80 receives approximately 28 volts of direct current for operation. However, this is merely exemplary, and depending on the type and arrangement of the heater element 80, the voltage required to operate the heater element 80 may be greater or less than 28 volts.

[0049] Figure 7 Also depicted are an accelerometer 70 and an airspeed-related sensor 78 in communication with the controller 72. As shown, the airspeed-related sensor 78 sends sensor voltage data that is generated by and indicative of the airflow pressure and velocity measured by the pitot tube pressure ports 74 and possibly the static pressure ports 75. The inertial sensor 70, such as an accelerometer, provides acceleration data indicative of the mechanical motion of the blade 16 and can be used to infer the pitch angle 36 of the blade 16 of the wind turbine 12. The controller 72 uses both the acceleration data from the inertial sensor 70 and the sensor voltage data from the airspeed-related sensor 78 to calculate a turbulence value for the airflow passing through the blade 12. Specifically, the acceleration data from the inertial sensor 70 (which will be described in more detail below) is used to filter vibration noise detected by the airfoil performance monitor 44, and the sensor voltage data from the airspeed-related sensor 78 is used to calculate the dynamic pressure at the blade 16 of the wind turbine 12. Likewise, as Figure 7 As shown, a power supply 82 is connected to the sensors in the mast 50, particularly the airspeed-related sensor 78, to provide power to the mast 50. As shown, the power supply 82 provides 28 volts of DC power to the airspeed-related sensor 78. The airspeed-related sensor 78 can also be adapted to be powered by any number of voltages from the power supply 82.

[0050] The controller 72 also communicates with the inertial sensor 70, the airspeed-related sensor 78, and the power supply 82. The power supply 82 is adapted to supply power to the controller 72 to allow the controller 72 to have sufficient processing power to calculate the digital airflow signal. Finally, the controller 72 is configured to calculate a filtered turbulent airflow signal. This turbulent airflow signal is used to calculate the airflow and turbulence intensity ratio, as will be described in more detail with reference to other figures. Specifically, the airspeed-related sensor 78 provides data indicating the total pressure at the blade 16 measured at the pitot tube orifice 74 of the airfoil performance monitor 44. The static pressure orifice 75 is used to measure the static pressure at the airfoil performance monitor 44. The measured static pressure is subtracted from the total pressure to obtain the dynamic pressure at the airfoil performance monitor 44. The inertial sensor 70 provides the controller 72 with data indicating the vibration frequency and amplitude of the vibrations on the blade 16 passing through the mast 50 to calculate the turbulence intensity ratio. Additionally, if necessary, the data from the inertial sensor 70 is corrected for the orientation of the blade 16 by the blade incidence angle (not shown) so that the signature, vibration frequency, and amplitude are extracted from the filtered turbulence signal using the controller 72. Gains are set in the controller 72 taking into account the blade pitch angle 36, which can be set to any pitch angle independent of the local airspeed.

[0051] Vibration frequency and amplitude data from inertial sensor 70 is used to filter a digital airflow signal derived from data indicating turbulent airflow from airspeed-related sensor 78 to eliminate noise caused by vibration of mast 50 on blades 16 of wind turbine 12. Specifically, as air impacts pitot tube aperture 74 and static pressure aperture 75, as the angle of attack of blade 16 increases, airspeed-related sensor 78 is excited by the increase in turbulence to generate an alternating current (AC) signal indicative of turbulent airflow. Changes in the aerodynamics of blade 16 due to contamination, damage, defects, or one or more other airflow-modifying factors may also increase airflow turbulence. Airspeed-related sensor 78 is excited by this increase in turbulence to generate an AC signal as data indicative of turbulent airflow. In the absence of mechanical vibration, since blade 16 is not moving mechanically, inertial sensor 70 provides a relatively small or zero oscillation signal, and it can be determined that the AC signal accurately indicates increased turbulence.

[0052] Conversely, if mechanical motion, such as vibration, is induced on blade 16, the mechanical motion relative to the airflow measured at pitot tube aperture 74 and static pressure aperture 75 generates an AC signal that falsely indicates increased turbulence. Inertial sensor 70 is adapted to record the mechanical motion during the vibratory oscillations as frequency and amplitude data so that the frequencies of these spurious vibration-induced turbulence signals can be determined and filtered out of the airflow signal. As described, controller 72 is configured to identify and filter frequency and amplitude data indicative of mechanical motion on blade 16 from the AC signal, such that the filtered digital airflow signal can be determined to accurately indicate increased turbulence. Controller 72 may include a filter that employs a fast Fourier transform method to identify characteristic frequencies caused by mechanical vibration. The filter may include a notch, bandpass, high-pass, low-pass, low-pass parabolic filter, or any other filter or filters to filter the undesirable vibration-induced signals from the digital airflow signal, thereby obtaining a correct measure of airflow turbulence. More specifically, the controller 72 may apply a fast Fourier transform to the accelerometer signal to determine the fundamental vibration frequency of the unwanted noise caused by the mechanical vibration of the blade performance monitor 44 at the mast 50. The controller 72 then uses filtering techniques, which may include, but are not limited to, one or more of a notch, bandpass, high-pass, low-pass, or low-pass parabolic filter, to remove the unwanted vibration-induced noise from the desired air turbulence signal. Under steady-state conditions, where the airflow measured by the pitot tube aperture 74 and the static pressure aperture 75 is laminar and the blade 16 is not vibrating, both signals provide minimal turbulence or motion signals, which are represented by a smooth direct current (hereinafter referred to as "DC") component of the digital airflow signal.

[0053] The controller 72 normalizes the filtered frequency and amplitude AC signal by dividing it by the DC component of the frequency and amplitude data from the airspeed-dependent sensor 78. The controller 72 also normalizes the input from one or more inertial sensors 70 (such as accelerometers) to acceleration components parallel to and perpendicular to the plane of rotation of the rotor 24 in response to the blade pitch angle 36. The controller 72 calculates the turbulence intensity ratio R by dividing the alternating airflow component (AC signal) by the steady-state component (DC signal). Thus, each airfoil performance monitor 44 generates a turbulence intensity ratio R at the location of the mast 50 on the blade 16. The controller 72 compares the turbulence intensity ratio R from each mast 50 located along the blade 16 with a threshold turbulence intensity ratio R' that is specific to the location of each airfoil performance monitor and the airspeed-dependent sensor associated with a given pitot tube pressure port, and represents the desired stall warning threshold for the blade section at that location. The airflow completely separates from the low-pressure side 29 of the affected section of the airfoil, resulting in a rapid reduction in blade thrust accompanied by a rapid increase in blade drag, which can have serious consequences for the operation of the wind turbine. The unstable airflow characteristics that typically accompany a stall can also lead to severe vibrations that jeopardize the integrity of the wind turbine and certainly affect the wear experienced by drive components.

[0054] Stall can be caused by operating at too high a blade pitch angle 36, or by environmental factors (such as icing) reducing the airflow over the airfoil, resulting in a premature stall at an otherwise "safe" blade pitch angle 36. Stall is always accompanied by an increase in the relative turbulence seen on the low pressure side 29 as the lift on the blade begins to decrease. The stall phenomenon of a rotating airfoil is complex. Different spanwise portions of a wind turbine airfoil may stall at different times; one blade may stall while another does not (for example, if ice breaks off asymmetrically from different blades); and the stall phenomenon may be periodic - for example, each blade may stall as it rotates past the wind turbine tower. It is these phenomena that the proposed invention addresses.

[0055] In the case of the wind turbine 12, as the blades 16 rotate about the rotor 24, stall conditions that reduce the lift of the blades 16 can reduce the rotational efficiency. In other words, the term stall refers to the reduction in lift and increase in drag caused by the pressure differential between the low-pressure side 29 and the high-pressure side 27 of the blade 16 collapsing due to the excessive angle of attack of the blade 16, which results in a significant increase in turbulence on the low-pressure side 29 of the blade 16. In extreme cases, these conditions can cause the rotational efficiency of the blade 16 to drop below the level required to keep the rotation of the wind turbine self-sustaining. The controller 72 can be further configured to adjust the threshold R' to account for changing conditions. For example, the controller 72 can use the blade pitch angle 36 measured using the accelerometer 70 to scale the turbulence intensity ratio R, thereby adjusting the threshold R' based on the angle of the blade 16.

[0056] The controller 72 may also be configured to transmit data indicating the turbulence intensity ratio R through various interfaces. Figure 7 As shown, the controller 72 can communicate with a memory card 88 to transmit a digital airflow signal including frequency and amplitude data, a steady-state component, and a turbulence intensity ratio R to a file management system (not shown). The memory card 88 can be removable or fixed with the controller 72 to allow the turbulence intensity ratio R to be transmitted and used in various control systems of the wind turbine 12 or for data analysis purposes. For example, the controller 72 can transmit the turbulence intensity ratio R as feedback input to the rotor control system 23 to optimize the aerodynamic efficiency of the rotor 24 of the rotor control system 23. In addition, the controller 72 can transmit vibration frequency and amplitude data as feedback input to the rotor control system 23 to minimize vibration of the rotor 24 of the rotor control system 23.

[0057] The controller 72 may communicate with the rotor control system 23 via a network interface 90. The network interface 90 may be a wireless network interface, a local area network interface, or any other data transmission interface configured to receive the turbulence intensity ratio R, the accelerometer frequency and amplitude data, the airflow data, and any other data generated by the airfoil performance monitor. Figure 7 As seen in FIG, the rotor control system 23 includes a corresponding network interface 92 to receive communications from the controller 72. In addition, the rotor control system 23 may be adapted to store user-defined preferences and calibration coefficients, receive and decode the turbulence intensity ratio R and associated data, and display the turbulence intensity ratio R and associated data for each airspeed-related sensor 78. The rotor control system 23 may also include a log file that records the turbulence intensity ratio R and associated data.

[0058] Figure 8A flow chart is depicted indicating the control logic used by controller 72 to calculate the turbulence intensity ratio R from airspeed-related sensor 78 and inertial sensor 70. As depicted, controller 72 receives airflow data generated by airspeed-related sensor 78 at 102, and blade vibration and rotational speed data generated by inertial sensor 70 (e.g., accelerometer) or provided from an existing wind turbine 12 control system at 104 and 106. Controller 72 filters rotational speed noise indicated by the rotational speed data at 106 from the digital airflow signal at 108, which may be provided from accelerometer 70. Controller 72 also filters vibration noise indicated by blade vibration noise at 104 measured from accelerometer 70 from the digital airflow signal at 110. As described above, the filters at 108 and 110 may be any type of filter configured to process vibration and rotational speed data, such as, but not limited to, notch, bandpass, high-pass, low-pass, or low-pass parabolic filters, and may determine the fundamental vibration frequency from the accelerometer signal using a fast Fourier transform.

[0059] Filtering blade vibration and rotational speed at 108 and 110 allows controller 72 to calculate turbulence intensity ratio R at 112 from the AC and steady-state signals (DC) of the digital airflow signal. As described, controller 72 calculates turbulence intensity ratio R at 112. Similarly, this allows controller 72 to communicate with rotor control system 23 to optimize blade pitch for maximum power and efficiency, which may be to improve the lift / drag ratio of the blades under prevailing wind conditions. In addition, controller 72 may communicate with rotor control system 23 to optimize blade pitch to minimize damaging vibrations or, in the worst case, vibrations that could lead to blade-tower collisions. Controller 72 may also use turbulence intensity ratio R and accompanying data to identify the incidence of contamination (such as icing) and activate heater 80 or other de-icing systems (not shown) on wind turbine blades. Specifically, controller 72 may use turbulence intensity ratio R to optimize the use of de-icing systems to avoid shutting down wind turbine 12. Controller 72 outputs turbulence intensity ratio R to rotor control system 23 at 114 to optimize rotor control system 23. In addition, as previously described, the controller 72 may also output the turbulence intensity ratio R to a display (not shown).

[0060] refer to Figure 9, a flow chart depicting the control logic of de-icing system 116 in communication with controller 72 is shown. For illustrative purposes, de-icing system 116 is configured to maintain the temperature of mast 50 between 35°F and 55°F. At 118, de-icing system 116 reads the temperature provided by controller 72. At 120, the de-icing system determines whether the temperature is greater than or less than 35°F. If the temperature is greater than 35°F at 120, de-icing system 116 continues to monitor the temperature from the controller at 118. If the temperature is less than 35°F at 120, de-icing system 116 activates heater element 80 at 122. At 124, the de-icing system reads the temperature from controller 72. At 126, the de-icing system determines whether the temperature is greater than or less than 55°F. If the temperature is less than 55°F at 126, de-icing system 116 continues to monitor the temperature from the controller at 124. If the temperature is greater than 55°F at 126, de-icing system 116 deactivates heater element 80 at 128. Activation of mast de-icing system 116 can be used in parallel to trigger activation of a blade de-icing system (if installed) to prevent ice from accumulating on blades 16 of wind turbine 12. Similarly, operation of de-icing system 116 prevents wind turbine 12 from shutting down due to ice accumulating on blades 16. In addition to facilitating de-icing of any blade, the blade performance monitor of the present invention can also be used to detect contamination or any type of environmental condition that causes blade performance degradation, which, in the representative embodiment described herein, can also result in degraded wind turbine performance. This information can be used to improve efficiency, schedule maintenance, or for any other purpose deemed beneficial by the end user.

[0061] The present invention has been described in an illustrative manner. It should be understood that the terminology used is intended to be descriptive rather than restrictive. Many modifications and variations of the present invention are possible in light of the foregoing teachings. Therefore, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.

Claims

1. A blade performance monitor, comprising: a housing mounted on a low pressure side of an airfoil and including at least one pitot tube pressure port for determining a total pressure at the airfoil performance monitor and at least one static pressure port for determining a static pressure at the airfoil performance monitor; at least one airspeed-dependent sensor that measures a total pressure at the airfoil performance monitor and determines a dynamic pressure as a difference between the total pressure and the static pressure, and generates a dynamic pressure signal indicative of the dynamic pressure at the airfoil performance monitor, the dynamic pressure signal comprising a steady-state airflow signal indicative of a steady-state airflow and a turbulence signal indicative of a turbulence value of the airflow; one or more inertial sensors that measure and identify vibration frequency and amplitude data due to mechanical motion on the housing; and a controller that normalizes the turbulence value of the dynamic pressure signal using the steady-state airflow signal and filters the turbulence value from the dynamic pressure signal using frequency and amplitude data from the one or more inertial sensors to determine the actual turbulent airflow over the airfoil by distinguishing between actual turbulent airflow over the airfoil and apparent turbulence caused by structural vibration of the airfoil to eliminate the effects of structural vibration on the turbulence intensity calculation to derive a turbulence intensity ratio, the controller using the determination of the actual turbulent airflow over the airfoil to generate a signal for adjusting the pitch angle of the airfoil to optimize aerodynamic efficiency.

2. The airfoil performance monitor of claim 1 , wherein the airspeed-related sensor is a pressure sensor, and the at least one pitot tube pressure port is in fluid communication with an associated pressure sensor to measure a total pressure acting on the airfoil performance monitor. 3 . The airfoil performance monitor of claim 1 , wherein the controller uses the vibration frequency data to filter the dynamic pressure signal.

4. The airfoil performance monitor of claim 1 , wherein the airfoil defines a chord, and the controller, in response to input from the one or more inertial sensors, normalizes the vibration signal to components parallel and perpendicular to the chord of the airfoil. 5 . The airfoil performance monitor of claim 1 , wherein the controller calculates the turbulence intensity ratio by dividing the turbulence signal by the steady-state airflow signal.

6. The airfoil performance monitor of claim 1 wherein the controller uses a threshold turbulence intensity ratio to provide an indication of blade stall. 7 . The airfoil performance monitor of claim 6 , wherein the controller uses a pitch angle of the airfoil measured by the one or more inertial sensors to adjust the threshold turbulence intensity ratio as a function of the pitch angle.

8. The airfoil performance monitor of claim 1, wherein the controller uses the turbulence intensity ratio as a feedback input to a rotor control system to optimize the aerodynamic efficiency of the airfoil.

9. The airfoil performance monitor of claim 1, wherein the controller filters the turbulence values using a Fast Fourier Transform method.

10. The airfoil performance monitor of claim 9, wherein the controller comprises a notch, bandpass, highpass, lowpass or lowpass parabolic filter to filter the turbulence value.

11. A blade performance monitoring system comprising: a housing mounted on a low pressure surface of the airfoil, the housing defining at least one pitot tube pressure sensing hole and at least one static pressure hole, the at least one pitot tube pressure sensing hole being used to determine a total pressure at an airfoil performance monitor, the at least one static pressure hole being used to determine a static pressure at the airfoil performance monitor; at least one airspeed-related sensor that measures the total pressure at the pitot tube pressure port and generates a dynamic pressure signal indicative of a dynamic pressure measured at the at least one pitot tube pressure port, the dynamic pressure signal comprising a steady-state airflow signal indicative of a steady-state airflow and a turbulence signal indicative of a turbulence value of the airflow; one or more inertial sensors that measure acceleration due to mechanical motion at the housing in up to three orientations from their mounting location; and a controller that derives a dimensionless turbulence intensity ratio of the turbulence value to a steady-state airflow component and filters the turbulence value from the dynamic pressure signal using the measured acceleration from the one or more inertial sensors to determine the actual turbulent airflow over the airfoil by distinguishing between actual turbulent airflow over the airfoil and apparent turbulence caused by structural vibrations of the airfoil to eliminate the effects of unwanted structural vibrations on the turbulence intensity calculation, the controller using the determination of the actual turbulent airflow over the airfoil and the turbulence intensity calculation to generate a signal for adjusting the pitch angle of the airfoil to optimize aerodynamic efficiency.

12. The airfoil performance monitoring system of claim 11, wherein the airspeed-related sensor is a pressure sensor, and the at least one pitot tube pressure port is in fluid communication with an associated pressure sensor to measure the total pressure acting on the airfoil performance monitor.

13. The airfoil performance monitoring system of claim 11, wherein the one or more inertial sensors include an accelerometer that measures frequency and amplitude of acceleration on a casing mounted on the low pressure face of the airfoil.

14. The airfoil performance monitoring system of claim 11, wherein the controller uses a threshold turbulence intensity ratio to give an indication of a stall condition at the airfoil.

15. The airfoil performance monitoring system of claim 14, wherein the controller uses the threshold turbulence intensity ratio as a feedback input to a blade pitch control system to optimize the aerodynamic efficiency of the airfoil and the efficiency of the overall rotor operation of a rotor control system.

16. The airfoil performance monitoring system of claim 11, wherein the controller uses the frequency and amplitude of the acceleration due to mechanical motion at the casing as feedback input to a rotor control system to minimize vibration of the rotor of the rotor control system.

17. A blade performance monitoring system for a wind turbine, comprising: a housing mounted on a low pressure side of the airfoil, the housing defining at least one pitot tube pressure port for measuring total pressure at an airfoil performance monitor and at least one static pressure port for measuring static pressure at the airfoil performance monitor; at least one airspeed-related sensor in fluid communication with the at least one pitot tube pressure port, the at least one airspeed-related sensor converting airflow measured through the pitot tube port and generating a dynamic pressure signal indicative of turbulence of the airflow, the dynamic pressure signal comprising a steady-state airflow signal indicative of steady-state airflow and a turbulence signal indicative of a turbulence value of the airflow; one or more inertial sensors that measure the pitch angle of the fin and movement in up to three orientations from its mounting location based on mechanical motion of the fin mechanically transmitted to the housing; a rotor control system that controls the pitch angle of the blades; and a controller that, in response to the pitch angle of the airfoil and the frequency of the acceleration of the airfoil's motion measured by the one or more inertial sensors, filters a turbulence value using the acceleration measured by the inertial sensors to determine actual turbulent airflow over the airfoil by distinguishing between actual turbulent airflow over the airfoil and apparent turbulence caused by structural vibration of the airfoil to eliminate the effects of structural vibration on a turbulence intensity ratio, and correlates the filtered turbulence value with a steady-state airflow signal to derive the turbulence intensity ratio, the controller using the determination of actual turbulent airflow over the airfoil to generate a signal to the rotor control system, the rotor control system acting in response to the signal from the controller to adjust the pitch angle of the airfoil to optimize aerodynamic efficiency.

18. An airfoil performance monitoring system according to claim 17, wherein the airspeed-related sensor is a pressure sensor and the at least one pitot tube pressure port is in fluid communication with an associated pressure sensor to measure the total pressure acting on the airfoil performance monitor.

19. The blade performance monitoring system of claim 17, wherein the controller normalizes acceleration signals into components parallel and perpendicular to a plane of rotation of the wind turbine blade in response to the pitch angle input measured by the one or more inertial sensors.

20. The airfoil performance monitoring system of claim 17, wherein the controller uses the pitch angle of the airfoil measured by the one or more inertial sensors to adjust a threshold turbulence intensity ratio indicative of a stall condition based on the pitch angle of the airfoil.

21. The airfoil performance monitoring system of claim 17, wherein the controller uses the turbulence intensity ratio as a feedback input to the rotor control system to optimize the aerodynamic efficiency of the airfoil.

22. A wind turbine comprising: one or more blades that rotate the shaft; a generator operatively connected to the shaft to convert mechanical energy into electrical energy; an airfoil performance monitor comprising a housing mounted on a low pressure surface of the one or more blades, the housing defining at least one pitot tube pressure port and at least one static pressure port; at least one airspeed-related sensor in fluid communication with the at least one pitot tube pressure port, measuring a total pressure of the airflow at the at least one pitot tube pressure port and generating a dynamic pressure signal indicative of turbulence of the airflow, the dynamic pressure signal comprising a steady-state airflow signal indicative of steady-state airflow and a turbulence signal indicative of a turbulence value of the airflow; one or more inertial sensors disposed on the low pressure side of the one or more blades that measure blade pitch angle and measure acceleration, frequency, and amplitude data in up to three orientations from a mounting location of one of the blades based on vibration of the blade through the housing; a rotor control system that controls the pitch angle of the one or more blades; and a controller that filters a turbulence value using the acceleration measured by the inertial sensors in response to the pitch angle of the at least one or more blades and the frequency of the acceleration of the movement of the at least one or more blades measured by the one or more inertial sensors to determine the actual turbulent airflow by distinguishing between actual turbulent airflow over the one or more blades and apparent turbulence caused by structural vibration of the at least one or more blades to eliminate the effects of structural vibration on the turbulence intensity ratio, and correlating the filtered turbulence value with the steady-state airflow signal to derive the turbulence intensity ratio, the controller using the determination of the actual turbulent airflow over the at least one or more blades to generate a signal to the rotor control system, the rotor control system acting in response to the signal from the controller to adjust the pitch angle of the one or more blades to optimize aerodynamic efficiency.

23. The wind turbine of claim 22, wherein the airspeed-related sensor is a pressure sensor and the at least one pitot tube pressure port is in fluid communication with an associated pressure sensor to measure the total pressure acting on the airfoil performance monitor.

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