Gas turbine temperature measurement

Abstract

The disclosure relates to a method for determining a temperature in a pressurized flow path of a gas turbine comprising the steps of sending an acoustic signal from an acoustic signal emitting transducer across a section of the pressurized flow path, detecting the acoustic signal with a receiving transducer, measuring the time needed by the acoustic signal to travel from the acoustic signal emitting transducer to the receiving transducer, calculating the speed of sound, and calculating the temperature as a function of the speed of sound, the heat capacity ratio (□) and a specific gas constant (R.sub.spec) of the gas flowing in the pressurized flow path. Besides the method, a gas turbine with a processor and transducers arranged to carry out such a method is disclosed.

Claims

1. A method for determining a temperature in a pressurized flow path of a gas turbine downstream of a compressor and upstream of a turbine, comprising: sending an acoustic signal from an acoustic signal emitting transducer arranged to send an acoustic signal across at least a section of a cross section of the pressurized flow path; detecting the acoustic signal with a receiving transducer arranged to receive the acoustic signal after the acoustic signal crossed the section; measuring the time needed by the acoustic signal to travel from the acoustic signal emitting transducer to the receiving transducer; calculating the speed of sound based on the measured traveling time and distance between acoustic signal emitting transducer and the receiving transducer; providing a heat capacity ratio (κ) and a specific gas constant (R.sub.spec) of a gas flowing in the pressurized flow path; and calculating the temperature of the gas in the section of the pressurized flow path as a function of the speed of sound, the heat capacity ratio (κ) and the specific gas constant (R.sub.spec) of the gas flowing in the pressurized flow path, wherein a combustion pulsation pressure is measured over frequency, a maximum pulsation pressure is determined, and a frequency of the acoustic signal emitting transducer is tuned to a frequency, with a combustion pulsation pressure, which is less than 20% of the maximum pulsation pressure.

2. The method for determining a temperature according to claim 1, wherein the combustion pulsation pressure is measured as a function of the frequency of the acoustic signal emitting transducer and the frequency of the acoustic signal emitting transducer is tuned to a frequency, which is free of pulsations and/or engine noise.

3. The method for determining a temperature according to claim 1, wherein the signal received by the receiving transducer is filtered for noise produced by the gas turbine and/or the acoustic signal sent by the acoustic signal emitting transducer is pulsed or sent with a frequency modulation.

4. The method for determining a temperature according to claim 1, wherein the combustion pulsation pressure is measured at an emitting frequency of the acoustic signal emitting transducer, and an acoustic signal pressure emitted by the acoustic signal emitting transducer is controlled to a predetermined multiple of the combustion pulsation pressure at the emitting frequency.

5. The method for determining a temperature according to claim 1, wherein gas composition of the gas flowing in the pressurized flow path is determined and the heat capacity ratio (κ) and/or specific gas constant (R.sub.spec) is determined based on the gas composition.

6. The method for determining a temperature according to claim 1, wherein the gas composition of the gas flowing in the pressurized flow path is approximated by an iteration, comprising: a) measuring the temperature upstream of a flame of combustion of the gas turbine; b) determining the gas composition upstream of the flame; c) using a starting value for the gas composition downstream of the flame; d) determining the heat capacity ratio (κ) and/or specific gas constant (R.sub.spec) for the starting composition; e) determining the hot gas temperature (T.sub.hot) after the flame based on the measured propagation speed of the acoustic signal, the heat capacity ratio (κ) and specific gas constant (R.sub.spec) for the starting composition; f) calculating the temperature increase in the combustor in the flame as a temperature difference (ΔT) between the hot gas temperature (T.sub.hot) after the flame and the temperature upstream of the flame (T.sub.2); g) determining the change in gas composition during combustion based on the temperature increase in the combustor (ΔT), a fuel composition and calculating the hot gas composition based on the gas composition upstream of the flame and on the change in gas composition during combustion; h) determining corrected iterated heat capacity ratio (κ.sub.i) and/or specific gas constant (R.sub.spec,i); i) recalculating an iterated hot gas temperature (T.sub.hot,i) after the flame based the iterated heat capacity ratio (κ.sub.i) and/or specific gas constant (R.sub.spec,i); and j) continue iterating at step e) until a convergence criterion is met.

7. The method for determining a temperature according to claim 1, comprising: a plurality of transducers used to determine an average temperature in the cross section and/or to determine a temperature profile in the cross section.

8. The method for determining a temperature in a pressurized flow path of a gas turbine according to claim 1, wherein the frequency of the acoustic signal emitting transducer is tuned to a frequency, with a combustion pulsation pressure, which is less than 10% of the maximum pulsation pressure.

9. The method for determining a temperature according to claim 1, wherein a pulsation probe used to monitor combustor pulsations is used as receiving transducer.

10. The method for determining a temperature according to claim 9, wherein the gas composition of a compressor inlet gas, the pressurized gas or an exhaust gas is measured, and the measured composition is corrected for changes in compositions due to addition of fluids and/or changes in composition due to combustion between the measurement point and the section in which the speed of acoustic signal is determined.

11. A method for determining a temperature in a pressurized flow path of a gas turbine downstream of a compressor and upstream of a turbine, comprising: sending an acoustic signal from an acoustic signal emitting transducer arranged to send an acoustic signal across at least a section of a cross section of the pressurized flow path; detecting the acoustic signal with a receiving transducer arranged to receive the acoustic signal after the acoustic signal crossed the section; measuring the time needed by the acoustic signal to travel from the acoustic signal emitting transducer to the receiving transducer; calculating the speed of sound based on the measured traveling time and distance between acoustic signal emitting transducer and the receiving transducer; providing a heat capacity ratio (κ) and a specific gas constant (R.sub.spec) of the gas flowing in the pressurized flow path; and calculating the temperature of the gas in the section of the pressurized flow path as a function of the speed of sound, the heat capacity ratio (κ) and the specific gas constant (R.sub.spec) of the gas flowing in the pressurized flow path, wherein a combustion pulsation pressure is measured as a function of a frequency of the acoustic signal emitting transducer and the frequency of the acoustic signal emitting transducer is tuned to a frequency, which is free of pulsations and/or engine noise.

12. The method for determining a temperature according to claim 11, wherein the signal received by the receiving transducer is filtered for noise produced by the gas turbine and/or the acoustic signal sent by the acoustic signal emitting transducer is pulsed or sent with a frequency modulation.

13. The method for determining a temperature according to claim 11, wherein the combustion pulsation pressure is measured at an emitting frequency of the acoustic signal emitting transducer, and an acoustic signal pressure emitted by the acoustic signal emitting transducer is controlled to a predetermined multiple of the combustion pulsation pressure at the emitting frequency.

14. The method for determining a temperature according to claim 11, wherein a gas composition of the gas flowing in the pressurized flow path is determined and the heat capacity ratio (κ) and/or specific gas constant (R.sub.spec) is determined based on the gas composition.

15. The method for determining a temperature according to claim 11, wherein the gas composition of the gas flowing in the pressurized flow path is approximated by an iteration, comprising: a) measuring the temperature upstream of a flame of combustion of the gas turbine; b) determining the gas composition upstream of the flame; c) using a starting value for the gas composition downstream of the flame; d) determining the heat capacity ratio (κ) and/or specific gas constant (R.sub.spec) for the starting composition; e) determining the hot gas temperature (T.sub.hot) after the flame based on the measured propagation speed of the acoustic signal, the heat capacity ratio (κ) and specific gas constant (R.sub.spec) for the starting composition; f) calculating the temperature increase in the combustor in the flame as a temperature difference (ΔT) between the hot gas temperature (T.sub.hot) after the flame and the temperature upstream of the flame (T.sub.2); g) determining the change in gas composition during combustion based on the temperature increase in the combustor (ΔT), a fuel composition and calculating the hot gas composition based on the gas composition upstream of the flame and on the change in gas composition during combustion; h) determining corrected iterated heat capacity ratio (κ.sub.i) and/or specific gas constant (R.sub.spec,i); i) recalculating an iterated hot gas temperature (T.sub.hot,i) after the flame based the iterated heat capacity ratio (κ.sub.i) and/or specific gas constant (R.sub.spec,i); and j) continue iterating at step e) until a convergence criterion is met.

16. The method for determining a temperature according to claim 11, wherein a pulsation probe used to monitor combustor pulsations is used as receiving transducer.

17. The method for determining a temperature according to claim 16, wherein the gas composition of a compressor inlet gas, the pressurized gas or an exhaust gas is measured, and the measured composition is corrected for changes in compositions due to addition of fluids and/or changes in composition due to combustion between the measurement point and the section in which the speed of acoustic signal is determined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention, its nature as well as its advantages, shall be described in more detail below with the aid of the accompanying drawings. Referring to the drawings:

(2) FIG. 1 schematically shows an example of a gas turbine according to the present invention.

(3) FIG. 2a schematically shows the cross section II-II of the first combustion chamber of the gas turbine from FIG. 1 with exemplary arrangements of transducers for measurement of a temperature.

(4) FIG. 2b schematically shows the cross section II-II of the first combustion chamber of the gas turbine from FIG. 1 with an exemplary arrangement of transducers for measurement of a temperature profile.

(5) FIG. 2c schematically shows the cross section II-II of the first combustion chamber of the gas turbine from FIG. 1 with an exemplary arrangement of transducers for measurement of averaged temperatures.

(6) FIG. 3 schematically shows the cross section III-III of the sequential combustion chamber of the gas turbine from FIG. 1 with an exemplary arrangement of transducers for measurement of a temperature profile.

(7) FIG. 4 schematically shows an exemplary arrangement of transducers connected to a processor for determining the temperature upstream of the first or second turbine of a gas turbine.

DETAILED DESCRIPTION

(8) The same or functionally identical elements are provided with the same designations below. The examples do not constitute any restriction of the invention to such arrangements.

(9) An exemplary arrangement is schematically shown in FIG. 1. The gas turbine 10 is supplied with compressor inlet gas 11. In the gas turbine 10 a compressor 12 is followed by a first combustor comprising a first burner 24 and a first combustion chamber 13. In the first burner 34 fuel 37 is added to the compressed gas and the mixture burns in the first combustion chamber 13. Hot combustion gases are fed from the first combustion chamber 13 into a first turbine 14 which is followed by a second combustor comprising a sequential burner 25 (also known as second burner) and a sequential combustion chamber 15 (also known as second combustion chamber). Fuel 37 can be added to the gases leaving the first turbine 14 in the sequential burner 35 and the mixture burns in the sequential combustion chamber 15. Hot combustion gases are fed from the sequential combustion chamber 15 into a second turbine 16.

(10) Steam and/or water 38 can be injected into the first and/or sequential burner for emission control and to increase the power output. Water 36 can also be injected into the compressor or upstream of the compressor for inlet cooling and power augmentation.

(11) In the example shown in FIG. 1 transducers 20, 21 are arranged in the compressor plenum 26, and the sequential burner 25 to measure the inlet temperature of the first, respectively the sequential combustion chamber 13, 15. To measure the hot gas temperature at vane one 18 of first turbine 14, respectively at vane one 19 of the second turbine 16 transducers 20, 21 are arranged in the downstream end region of first and sequential combustion chamber 13, 15, respectively. Transducers 20 are arranged on the inner walls towards the machine axis 28 and transducers 21 are arranged on the outer walls towards the casing 17 of the gas turbine.

(12) Exhaust gas 17 leaves the second turbine 16. The exhaust gas 17 is typically used in a heat recovery steam generator to generate steam for cogeneration or for a water steam cycle in a combined cycle (not shown).

(13) Optionally, part of the exhaust gas 17 can be branched off in a flue gas recirculation 34 (typically downstream of heat recovery steam generator) and admixed to the inlet air 35. Typically the recirculation 34 comprises a recooler for cooling the recirculated flue gas.

(14) FIG. 2a schematically shows the cross section II of the first combustion chamber 13 of the gas turbine 10 from FIG. 1 with first exemplary arrangements of transducers 20, 21.

(15) In a first example the acoustic signal emitting transducers and receiving transducers 20a, 21a are arranged on the inner wall 22, respectively outer wall 24 of the first combustion chamber 13 such that they face each other at the same circumferential position. In each case they are arranged downstream of a first burner 24.

(16) In a second example the acoustic signal emitting transducer and receiving transducers 20b, 21b are arranged on the inner wall 22, respectively outer wall 24 of the first combustion chamber 13 such that they face each other at the same on circumferential position. In each case they are arranged downstream and between two first burners 24.

(17) In a third example the acoustic signal emitting transducer and receiving transducer is combined in one device 20c, 21c. The transducer 20c is arranged on the inner wall 22, respectively the transducer 21c on the outer wall 24 of the first combustion chamber 13. The acoustic signal send by a transducer 20c, 21c is reflected by the opposite side wall facing the transducer, and the reflected acoustic signal is detected by the transducer 20c, 21c.

(18) FIG. 2b shows a cross section of the first combustion chamber 13 of the gas turbine 10 from FIG. 1 with exemplary arrangements of transducers 20, 21 for measurement of a temperature profile.

(19) The acoustic signal emitting transducer 20 can for example be arranged circumferentially distributed along the inner wall 22 of the first combustion chamber 13. The receiving transducers 21 can for example be arranged circumferentially distributed along the outer wall 23 of the first combustion chamber 13. For each acoustic signal emitting transducer 20 a plurality of receiving transducers 21 i, ii, ii . . . v is arranged along a section of the outer wall 23 facing a corresponding acoustic signal emitting transducer 20. The average speed of sound between each acoustic signal emitting transducer 20 and corresponding receiving transducers 21 i, ii, ii . . . v can be measured and the corresponding temperature can be derived, thus leading to a temperature distribution. An average temperature can be calculated based on the individual measurements for the section between the emitting transducer 20 and each receiving transducer 21 i, ii, ii . . . v. For temperature averaging the mass flow passing each section can be used.

(20) The acoustic signal emitting transducer 21 can also be distributed on the outer wall 23 and the receiving transducers 20 on the inner wall 22. In an alternative embodiment the plurality of transducers 21 i, ii, ii, v can also be acoustic signal emitting transducer 21 and the transducer 20 a receiving transducer.

(21) If the acoustic signal from more than one acoustic signal emitting transducer 20, 21 is received by a receiving transducer 20, 21 a synchronization of the acoustic signal emitting transducers 20, 21 can be advantageous to easier allocate the received signal to the emitted acoustic signals. Alternatively a sequenced pulsing of the acoustic signal emitting transducers can be carried out.

(22) In a further alternative different emitting frequencies are used for the plurality of acoustic signal emitting transducers 20, 21.

(23) For any arrangement with a plurality of acoustic signal emitting transducers different frequencies for the different acoustic signal emitting transducers can be used. Also frequency modulations of the acoustic signal emitting transducers can be applied. The modulations of the different acoustic signal emitting transducers can be time shifted to facilitate allocation of the received signals to the emitting transducers.

(24) FIG. 2c shows a cross section of the first combustion chamber 13 of the gas turbine 10 from FIG. 1 with exemplary arrangements of transducers 20, 21 for measurement of averaged temperatures.

(25) In this example the acoustic signal emitting transducers 21a are arranged in opposite locations on the outer wall 23 of the annular cross section of the combustion chamber 13. Between two acoustic signal emitting transducers 21a a receiving transducer 21b is arranged on the outer wall 23. In this example the flow path of the combustion chamber 13 is high enough that in an equidistant alternating arrangement of two acoustic signal emitting transducers 21a and two receiving transducers 21b on the outer wall 23 can be arranged such that each receiving transducer is in a line of sight of the neighboring acoustic signal emitting transducers 21a. The average speed of sound and thereby the average temperature along each line of sight can be determined with this arrangement. The overall average temperature can be estimated by averaging the temperatures determined for all for sections.

(26) In FIG. 3 the cross section III-III of the sequential combustion chamber of the gas turbine from FIG. 1 is schematically shown. It shows another exemplary arrangement of transducers 20, 21 for measurement of a temperature distribution. At a location between every other sequential burner 25 a transducer 21 is arranged on the outer wall and staggered relative to the transducers 20 on the inner wall. The transducers 20 are arranged on the inner wall at a location between every other sequential burner 25. The acoustic signal emitting transducers can be arranged on the outer wall and the receiving transducers on the inner wall or vice versa. The average temperature can be determined for each section between each acoustic signal emitting transducers 20, 21 and receiving transducer 20, 21 for each sequential burner 25 leading to a temperature distribution in circumferential direction. The average hot gas temperature can be calculated based on the individual averages downstream of each sequential burner 25.

(27) FIG. 4 shows an exemplary arrangement of transducers connected to a processor for determining the temperature upstream of the vane one 18, 19 of turbine a gas turbine. The processor 30 controls an acoustic signal emitting transducer 20 arranged on the inner wall 22 of the combustion chamber 13, 15 of the gas turbine. It is controlled to send a pulsed sound 33. The receiving transducer 20, 21 detects the sound pressure on the outer wall 23 of the combustion chamber 13, 15 converts it into an electric or optical signal and transmits the measured value to the processor 30. The processor 30 filters the signal corresponding to the emitted acoustic signal. Based on the filtered signal corresponding to the emitted acoustic signal the hot gas temperature 32 is determined and used for the gas turbine control. Based on the acoustic sound level 29 a pulsation signal 31 is determined and used for control and protection of the gas turbine.

(28) The arrangements shown as example for the first combustor in FIGS. 2a to 2c can be directly applied to a second combustor, and the example for FIG. 3 can be directly applied to a first combustor.

(29) In the FIG. 2a) to 2c) and FIG. 3 examples with annular combustion chambers are shown. The disclosed method can analogously be applied to gas turbines with can combustors. Transducers in burners as well as in can combustors do not have to be placed on inner, respectively outer walls but can be placed anywhere on the perimeter of the burner or combustion chamber.