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(11) | EP 2 573 318 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A blade for a turbomachine comprising temperature and expansion sensors |
| (57) A blade (1) for a turbomachine includes at least one temperature sensor (4) adapted
to measure temperature of the blade, at least one expansion sensor (5) adapted to
measure expansion of the blade, and a module (6) for controlling the sensors (4,5),
adapted to simultaneously measure the expansion and temperature of the blade (1).
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[0001] The present invention relates to a component for a turbomachine and more particularly to a blade for the turbomachine.
[0002] In modern day turbomachines various components of the turbomachine operate at very high temperatures. These components include the blade or vane component, which are in shape of an airfoil. In the present application, only the term "blade" is used, but the specifications can be transferred to a vane. The high temperatures during operation of the turbomachine may damage the blade or vane component; therefore it is important to know the temperature profiles and the corresponding expansions of the blades for making a predication about the life span of the blade and for evaluating the current operational state of the blade.
[0003] One way to analyze the temperature was deriving the value from theoretical calculations or through physical parameters such as the β-phase depletion of the MCrAlY coating which is applied on a component of the turbomachine to protect it from hot environment. Another technique to analyze the temperature of the component was through use of y modification.
[0004] Currently, methods such as calculating a light emission from doped ceramic surfaces are used to analyze the temperatures of the blade or vane component. Furthermore, the temperatures are also determined by spraying thermo-elements. However, in the above mentioned methods, only the temperatures of the blade or vane component can be determined. These methods are unable to provide information regarding expansion of the components and thus are unable to provide prediction on the life span of the component.
[0005] It is therefore an object of the present invention to provide information on temperature as well as the expansion of the component operating at high temperatures.
[0007] According to the invention, a blade for a turbomachine is provided. The blade includes at least one temperature sensor present in the airfoil portion of the blade adapted to measure the temperature of the blade, at least one expansion sensor present in the airfoil portion adapted to measure the expansion of the blade and a module for controlling the sensors to simultaneously measure the temperature and expansion of the blade. By simultaneously measuring the temperature profile and expansion of the blade a prediction can be made regarding life span of the blade as well as the current operational state of the blade. Furthermore, expansion of the blade is dependent on the temperature of the blade hence, expansion at a particular temperature is determined with the help of the above arrangement.
[0008] From the values of the expansion and temperature that are obtained, resistivity is calculated for the material of the blade.
[0009] In one embodiment, the module is adapted to supply electric current to the expansion sensor to measure the resistance of the expansion sensor.
[0010] According to an embodiment, the temperature sensor and the expansion sensor are made of metal capable of withstanding the operating temperature of the turbomachine.
[0011] In another embodiment, the temperature sensor and the expansion sensor are made of metal alloy capable of withstanding the high temperatures, without exhibiting a change in resistivity.
[0012] In one embodiment, the expansion sensor extends at least partially along the airfoil portion along a longitudinal axis of the blade since the airfoil portion is subjected to a harsh environment due to hot gases. Extent of the expansion sensor along the airfoil portion increases sensitivity in measurement of resistance. An accurate determination of resistance is achieved even if there are considerable changes in the structure of the blade at the time of the molding.
[0013] In one embodiment, the temperature sensor is located close to the expansion sensor such that the measurement parameters, such as current and voltage can be separated from each other without ambiguity. The temperature sensor should be as close as possible to the expansion sensor to ensure that no temperature induced failure will be measured. It may be noted that the term "close" as used herein means a distance in the range from about 1 mm to about 3 mm. Use of constant current ensures that only the voltage will be measured which is related to temperature and expansion.
[0014] In another embodiment, the expansion sensor is connected to the module through a 4 way circuit. The 4-way circuit enables measurement of resistance at different points, thus obviating the need of placing multiple expansion sensors in the blade. In addition use of a 4-way circuit ensures that a cable resistivity is not measured. As used herein the term "cable resistivity" is the resistance of a cable, which results in voltage drop when the current flows through the cable.
[0015] In one embodiment, the module is adapted to generate pulses to the expansion sensor which reduces power consumption as well as the measurement losses.
[0016] In another embodiment, a high frequency system is used to transmit the measurement signal out of the blade. The use of a high frequency system facilitates sending the measurement signal accurately which is then used for analysis.
[0018] In one embodiment, the sensor is located at the base material of the blade. In another embodiment, the sensor is located on a tie layer of the blade. In yet another embodiment, the sensor is located at a thermal insulation layer of the blade depending on the region of the blade for which the expansion and temperature has to be determined. This enables predicting the life span and the current state of the above mentioned layers of the blade.
[0019] The above-mentioned and other features of the invention will now be addressed with reference to the accompanying drawings of the present invention. The illustrated embodiments are intended to illustrate, but not to limit the invention. The drawings contain the following figures, in which like numbers refer to like parts, throughout the description and drawings.
FIG 1 is a schematic diagram of an exemplary blade for a turbomachine, and
FIG 2 is a sectional view depicting layers in the blade, in accordance with aspects of the present technique.
[0020] Embodiments of the present invention generally relate to a component of a turbomachine which is subjected to harsh environment due to the presence and impact of hot gases which are sometimes above the operating temperature of the turbomachine. More particularly, embodiments of the present invention are related to a blade or vane of the turbomachine. In the description provided hereinafter, the invention will be described with reference to a blade. However, the details of the embodiments described in the following can be transferred to a vane component without modifications, that is the terms "blade" or "vane" can be used in conjunction, since they both have the shape of an airfoil. It may further be noted that the turbomachine may include a gas turbine, a steam turbine, a turbofan and the like.
[0021] FIG 1 is a schematic diagram of an exemplary blade 1 of a rotor (not shown) of a turbomachine, such as a gas turbine. The blade 1 includes an airfoil portion 2 and a root portion 3. The airfoil portion 2 projects from the root portion 3 in a radial direction as depicted, wherein the radial direction means a direction perpendicular to the rotation axis of the rotor. Thus, the airfoil portion 2 extends radially along a longitudinal direction of the blade 1. The blade 1 is attached to a body of the rotor (not shown), in such a way that the root portion 3 is attached to the body of the rotor whereas the airfoil portion 2 is located at a radially outermost position.
[0022] In accordance with aspects of the present technique, the airfoil portion 2 of the blade 1 includes a temperature sensor 4 and an expansion sensor 5. The temperature sensor 4 is adapted to measure the temperature of the blade 1 and the expansion sensor 5 is adapted to measure the expansion of the blade 1 at a particular temperature. It may be noted that platinum or palladium bases sensors, ceramic sensors or sensors made of semiconductors may be used as expansion sensors.
[0023] In accordance with aspects of the present technique, the expansion sensor 5 and the temperature sensor 4 are formed of a metal or metal alloy capable of withstanding high temperatures. More particularly, the temperatures during the operation of the turbomachine may be in the range of about 800 degree centigrade. Therefore, the expansion sensor 5 and the temperature sensor 4 are made of metal such as, but not limited to platinum, palladium or tungsten. Additionally, the temperature sensor 4 and the expansion sensor 5 may be formed of metal alloys such as, but not limited to a platinum-palladium alloy, a platinum-rhenium alloy or a platinum-rhodium alloy.
[0024] It may further be noted that the material of the temperature sensor 4 and the expansion sensor 5 are chosen such that the temperature sensor 4 and the expansion sensor 5 have a resistance from about 100 ohm to about 1000 ohm at room temperature. As used herein, the term "room temperature" is indicative of a temperature of about 20 degree centigrade to about 25 degree centigrade.
[0025] The expansion sensor 5 and the temperature sensor 4 may be placed on a surface of the blade 1 for which measurement has to be made. As an example, the sensors may be placed on a base material of the blade, on a tie layer which is also the adhesion promoting layer or on the thermal insulation layer depending on where the temperature and expansion has to be measured.
[0026] Additionally, the expansion sensor 5 extends at least partially along the airfoil portion 2 of the blade 1. In one embodiment, the expansion sensor 5 may extend to cover the entire length of the airfoil portion 2. However, the temperature sensor 4 is present at a specific location in the blade 1 so as to measure the temperature at that particular location. More particularly, the expansion sensor 5 extends at least partially along a longitudinal axis of the blade 1 in the airfoil portion 2.
[0027] It may be noted that the temperature sensor 4 and the expansion sensor 5 are located proximal to each other. As used herein the term proximal is indicative of a distance from about 1 mm to about 3 mm with respect to each other.
[0028] The root portion 3 of the blade 1 includes a module 6, which in the presently contemplated configuration is a measurement and transmission module. The module 6 is adapted to control the temperature sensor 4 and the expansion sensor 5 and thereby simultaneously measure the temperature and the expansion of the blade 1. The information collected by the module 6 is transmitted to a control unit for analysis. The module 6 is connected to the expansion sensor 5 and the temperature sensor 4 via a 4-way circuit arrangement.
[0029] The module 6 is connected to the expansion sensor 5 via 4-way circuit arrangement. The 4-way circuit is used to control a device from multiple points. Use of 4-way circuit ensures that the cable resistivity is not measured and only the resistance of the sensors is taken into account for measuring the voltage. The module 6 includes a current source 9 adapted to apply a constant current to the expansion sensor 5. The module 6 electronically controls the amount of current supplied to the expansion sensor 5. It may be noted that the current may be in the range of milliampere or microampere. A voltage measuring device 10 is present in the module 6 which measures the voltage drop at the expansion sensor 5 due to the change in resistance at operating temperatures. In case of an expansion of the expansion sensor 5 its electrical resistance changes resulting in a voltage drop. The 4-way circuit ensures that the voltage drop due to the cables or wires is not measured.
[0030] A direct current (DC) or a low frequency alternating current (AC) may be supplied in the 4-way circuit to measure the voltage drop at the expansion sensor 5 and the temperature sensor 4.
[0031] In accordance with aspects of the present technique, the voltage measuring device 10 measures the voltage drop across the expansion sensor 5 and captures it as a signal. The alternating current part and the direct current part of the signal from the expansion sensor 5 may be separated to capture the dynamic properties of the component such as the blade. These dynamic properties may include the vibrations occurring during the operation of the turbomachine. For separating the two different signals from the alternating current part and the direct current part a condenser coupling or a high pass filter may be used.
[0032] The signal from the direct current is used for measuring the expansion and temperature of the blade, whereas the signal from the alternating current provides information about the vibration frequency of the blade.
[0033] It may also be noted that the module 6 may also be adapted to generate current pulses to the expansion sensor 5, this enables minimising the losses and also the power consumption. The signal which is received from the expansion sensor 5 is transmitted to a control unit 12 via a High frequency (HF) system 8 in form of data. The HF system 8 is located in the colder region of the blade 1 such as the root portion 3 which is generally less subjected to the hot gases. As used herein the term "high frequency" is used for frequency in the range from about 1 kHz to 1000 kHz when a radio frequency identification device (RFID) technique is used. However, the term "high frequency" is used for frequency in the range of about 100 MHz to about 150 MHz when using other techniques. As an example data from the blade 1 out of the housing to the control unit 12 is transmitted at a frequency of 125 kHz using the RFID technique.
[0034] The module 6 also includes a multiplexer 11 for selecting one of the signals from the expansion sensor 5 and the temperature sensor 4, which is then sent to the control unit 12 via the HF system 8. The control unit 12 examines the trend in the signal and monitor any change in the signal received from the module 6.
[0035] It may be noted that the control unit 12 may be present locally at the operating site of the turbomachine or at a distant location for monitoring the change in the signals.
[0036] Data sent out to the control unit 12 is analyzed to measure the expansion at a particular temperature. This data may be used to determine low cycle fatigue (LCF) affect in the blade 1, which results in initiation of cracks in the high stress region of the blade 1. In addition, the data may also be analyzed to determine creep, which is a tendency of a solid material to deform permanently under the influence of stress.
[0037] Referring now to FIG 2, a sectional view 20 depicting layers of the blade 1 is depicted. As previously noted, the blade 1 includes one or more layers coated on a base material 22, thereby providing protection to the base material 22 of the blade 1. The base material 22 of the blade 1 may be made up of a super alloy.
[0038] A tie layer 24 is applied over the surface of the base material 22. The tie layer 24 is also referred to as adhesion promoting layer. On top of the tie layer is the thermal insulation layer 26 which protects the base material from high temperatures which may exceed 800 degree centigrade for example. The sensors 4, 5 may be placed at the base material 22, or at the tie layer 24 or alternately at the thermal insulation layer 26 of the blade 1. Presence of sensors at the thermal insulation layer 26 provides information on temperature at the thermal insulation layer which could be used to determine the life time of the coating.
1. A blade (1) for a turbomachine, comprising:
- at least one temperature sensor (4) adapted to measure temperature of the blade,
- at least one expansion sensor (5) adapted to measure expansion of the blade, and
- a module (6) for controlling the sensors (4, 5), adapted to simultaneously measure the expansion and temperature of the blade (1).
2. The blade (1) according to claim 1,
wherein the sensors (4, 5) are located in an airfoil portion (2) of the blade (1).
wherein the sensors (4, 5) are located in an airfoil portion (2) of the blade (1).
3. The blade (1) according to claim 1 and 2,
wherein the module (6) is adapted to supply electric current to the expansion sensor (5).
wherein the module (6) is adapted to supply electric current to the expansion sensor (5).
4. The blade (1) according to claim 1,
wherein the temperature sensor (4) and/or the expansion sensor (5) comprise a metal capable of withstanding an operating temperature of the turbomachine.
wherein the temperature sensor (4) and/or the expansion sensor (5) comprise a metal capable of withstanding an operating temperature of the turbomachine.
5. The blade (1) according to claim 1,
wherein the temperature sensor (4) and/or the expansion sensor (5) comprise a metal alloy capable of withstanding the operating temperature of the turbomachine.
wherein the temperature sensor (4) and/or the expansion sensor (5) comprise a metal alloy capable of withstanding the operating temperature of the turbomachine.
6. The blade (1) according to any of the claims 4 or 5,
wherein the metal and/or the metal alloys have an electrical resistance from about 100 ohm to about 1000 ohm.
wherein the metal and/or the metal alloys have an electrical resistance from about 100 ohm to about 1000 ohm.
7. The blade (1) according to any of the claims 1 to 6,
wherein the expansion sensor (5) is located at least partially along a longitudinal axis of the blade.
wherein the expansion sensor (5) is located at least partially along a longitudinal axis of the blade.
8. The blade (1) according to any of the claim 1 to 7,
wherein the expansion sensor (5) and the temperature sensor (4) are connected to the module (6) through a 4-way circuit arrangement.
wherein the expansion sensor (5) and the temperature sensor (4) are connected to the module (6) through a 4-way circuit arrangement.
9. The blade (1) according to any of the claims 1 to 8,
wherein the module (6) is adapted to generate pulses to the expansion sensor (5).
wherein the module (6) is adapted to generate pulses to the expansion sensor (5).
10. The blade (1) according to any of the claims 1 to 9,
wherein the module (6) comprises a high frequency system (8) for transmitting a signal to a control unit (12).
wherein the module (6) comprises a high frequency system (8) for transmitting a signal to a control unit (12).
11. The blade (1) according to any of the claims 1 to 10, wherein the module (6) comprises
a multiplexer (11) for selecting one or more signals from the sensors (4, 5).
12. The blade (1) according to any of the claims 1 to 11, wherein the sensors are located
at a base material (22) of the blade (1).
13. The blade (1) according to any of the claims 1 to 11, wherein the sensors are located
on a tie layer (24) of the blade (1).
14. The blade (1) according to any of the claims 1 to 11, wherein the sensors are located
at a thermal insulation layer (26) of the blade (1).
15. A turbomachine comprising a blade (1) according to any of the above claims 1 to 14.