System and method for detecting hydrogen leakages in a turbomachine enclosure

Abstract

Described herein is a turbomachine system comprising a turbomachine and an enclosure surrounding the turbomachine and containing at least one duct adapted to contain a flammable gas. An ultrasonic gas leak detector arrangement housed in the enclosure is adapted to detect flammable gas leakages in the enclosure. Disclosed herein is also a method for detecting gas leakages in an enclosure housing a turbomachine.

Description

SYSTEM AND METHOD FOR DETECTING HYDROGEN LEAKAGES IN A TURBOMACHINE ENCLOSUREDESCRIPTIONTECHNICAL FIELD

[0001] The present disclosure concerns turbomachines. Embodiments disclosed herein concern safety instrumentalities adapted to improve the operating safety of turbomachines involving flammable gases and specifically gas turbine engine supplied with a gaseous fuel.BACKGROUND ART

[0002] In view of increasing concerns about climate changes a general trend towards reduction of carbon dioxide emissions characterizes recent researches in the field of power generation equipment and devices. In particular, gas turbine manufacturers are working to reduce the CO2 emissions of gas turbine engines. One approach is to use hydrogen as an alternative to natural gas (mainly methane) as fuel for gas turbine engines. Combustion of hydrogen generates water and does not generate carbon dioxide.

[0003] -The introduction of hydrogen as fuel for a gas turbine requests to evaluate the safety of the entire gas turbine package, that consists of auxiliary systems, instruments and other equipment required for the functioning thereof.

[0004] A gas turbine and part of the auxiliary systems are usually installed inside an acoustic enclosure. Among the auxiliary systems housed in the enclosure, it is worth mentioning the fuel gas line, which supplies the gas turbine combustor, and the connections thereof, which could be potential source of leak. This creates an additional issue to be evaluated in terms of safety.

[0005] In order to dilute possible fuel gas leaks a ventilation system is one of the essential auxiliary systems provided in a gas turbine package. Beyond ventilation, gas sensors and detectors are required to detect the presence of an unexpected leakage.

[0006] Gas leaks can occur from flanged or threated connection. In such cases, the response time of the detection system is crucial to limit the potential risk.to have aflammable mixture inside the gas turbine enclosure.

[0007] Nowadays, the most common used gas detectors are based on the infrared (IR) technology. They can be installed both at the ventilation outlet of the enclosure, where it is possible to monitor any leak inside the gas turbine enclosure. Alternatively, or in combination the detectors can be housed inside the enclosure, closer to the potential leak source in order to anticipate the detection. Infrared detectors are not able to detect hydrogen, The most common alternative to infrared gas detectors in the oil&gas sector are so-called catalytic detectors, which are adapted to detect any percentage of hydrogen. However, catalytic detectors have a much longer response time compared to infrared detectors.

[0008] A more efficient and safe detection arrangement for hydrogen-fueled gas turbine engines would therefore be welcomed in the art.SUMMARY

[0009] To alleviate the drawbacks of the prior art gas leakage detections systems, according to the present disclosure, the gas turbine engine system includes an ultrasonic gas leak detector arrangement adapted to detect hydrogen leakages. The ultrasonic gas leak detector arrangement is housed in the enclosure of the gas turbine engine.

[0010] Ultrasonic gas leak detectors are based on microphone sensing elements and are typically used to detect outdoor leaks by sensing the distinct high frequency ultrasound (from 20 kHz to 100 kHz) emitted by all high-pressure gas leaks (natural gas and H2). They have a nearly instantaneous response within 1-3 seconds and they are less prone to malfunctioning due to environmental factors such as wind. Moreover, they do not need to be in physical contact with the gas leak and no routine calibration is required.

[0011] Ultrasonic gas leak detectors are not able to detect gas concentrations and are sensitive to background noise like the one generated by a gas turbine engine during running.

[0012] Tests performed on a gas turbine engine system including an enclosurehousing ultrasonic gas leak detectors, reported below in more detail, have surprisingly shown that in spite of their sensitivity to background noise, ultrasonic gas leak detectors are capable of distinguishing ultrasound waves generated by hydrogen leakages in a very noise environment such as the gas turbine enclosure and are therefore a safe a and efficient alternative to state of the art detectors in safely and promptly detecting hydrogen leakages in the turbine enclosures.

[0013] Currently preferred embodiments are based on ultrasonic gas leak detectors are adapted to provide signals in a range frequency typically above 10 kHz, or above 20 Hz, or above 25 kHz, and preferably below 100 kHz, or below 70 kHz. Tests performed on gas turbine systems including an enclosure which houses a gas turbine engine show that the ultrasonic gas leak detectors operating in the above-mentioned frequency ranges can generate a useful signal in case of hydrogen leakages, despite the high background noise generated by the turbomachine in the enclosure. Sound waves at frequencies below 20 kHz are usually not affected by hydrogen leaks, while at higher ultrasonic frequencies the contribution of hydrogen leaks to the total detected sound pressure level is remarkable and can be distinguished from background noise, thus providing a useful information which can trigger a prompt alarm in case of gas leakage detection, with a reaction time which can be as low as 2 seconds.

[0014] In more general terms, disclosed herein is a system comprising a rotary turbomachine, specifically a gas turbine engine, housed in an enclosure, the enclosure containing at least one duct containing gaseous fuel to be supplied to the gas turbine engine . The system further comprises an ultrasonic gas leak detector arrangement in the enclosure, adapted to detect gaseous fuel leakages inside the enclosure, specifically while the gas turbine engine is operating, for instance.

[0015] While the use of ultrasonic gas leak detectors adapted to detect hydrogen leaks in a gas turbine engine system is particularly advantageous over the current art, for the reasons outlined above, the novel system described herein can provide some advantages also in applications where the flammable gas is not hydrogen or a blend containing hydrogen. For instance, the ultrasonic gas leak detector arrangement can be used to detect natural gas leakages in an enclosure housing a rotary turbomachine such as a gas turbine engine.

[0016] Moreover, while using ultrasonic gas leak detectors is particularly beneficial in combination with gas turbine engines, wherein the flammable gas is (part of) the fuel delivered to the turbine compressor, in other embodiments the novel features disclosed herein can be used in combination with a different turbomachine, for instance a compressor, such as a dynamic compressor processing hydrogen or a blend containing hydrogen, or another flammable gas, such as methane or the like. The flammable gas can be contained in a duct and can be the gas processed by the turbomachine, for instance methane, or hydrogen compressed by a compressor. In some embodiments, the flammable gas can be for instance contained in a suction duct, a flow path inside the turbomachine, or a delivery duct of a compressor and flows therein during operation of the compressor. The flammable gas can also be contained in other ducts of the turbomachine, such as ducts which deliver dry gas to dry gas seals of the turbomachine. This can be the case, for instance, when a flammable process gas processed by the compressor is also used as a dry gas for the dry gas seals.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Reference is now made briefly to the accompanying drawings, in which: Fig. l is a schematic showing a gas turbine system with relevant enclosure;Figs 2A, 2B, 2C, 3A, 3B, 3C are diagrams showing data collected during operation of the ultrasonic gas leakage detectors in various operating conditions of the gas turbine engine; andFigs, 4, 5(A), 5(B), 5(C), 6, 7(A) and 7(B) are diagrams showing further data collected during operation of the detectors under variable conditions of the gas turbine engine.DETAILED DESCRIPTION

[0018] The detailed description below specifically relates to the application of the novel features disclosed herein to a system including a gas turbine engine fueled with hydrogen or with a gaseous blend containing hydrogen, and housed in an enclosure.

[0019] Fig. l schematically shows a gas turbine engine system 1, which includes an enclosure 3 housing a gas turbine engine 5. The enclosure 3 includes a combustion air inlet 7 and a flue gas outlet 9. The enclosure further includes a ventilation air inlet 8and a ventilation air outlet 10.

[0020] The gas turbine engine 5 includes a compressor section 5.1, a combustor section 5.2 and a turbine section 5.3. The latter is drivingly coupled to a load 11, e.g., a compressor or an electric generator, through a shaft line 13.

[0021] The gas turbine engine 5 is fed with a fuel through a fuel line 15. The fuel can be hydrogen or a blend including hydrogen, for instance hydrogen and natural gas.

[0022] According to embodiments disclosed herein, an ultrasonic gas leak detector arrangement 17 is housed in the enclosure 3. In some embodiments, the ultrasonic gas leak detector arrangement 17 comprises a plurality of ultrasonic gas leak detectors 17.1, 17.2 arranged around an axis A-A of the gas turbine engine 5 and in one or more positions along the axial extension of the gas turbine engine. As will be described in greater detail below, in some embodiments the detectors are arranged approximately at mid-height along the vertical extension of the gas turbine engine, i.e., on or near a median vertical plane containing the rotation axis A-A of the turbomachine, preferably on both sides of the turbomachine, i.e. on both sides of a median vertical plane containing the axis A-A of the gas turbine engine. The option is not excluded, to arrange one or more detectors in different positions, for instance under the gas turbine engine or above the gas turbine engine, depending upon the aerodynamic conditions, the noise reflections, and temperature distribution in the enclosure. Additionally, while it is possibly more appropriate to place the detectors at or near the forward end of the gas turbine engine, i.e. in an area around the compressor section, where the temperature is lower than around the combustor or the most aft section, i.e. the turbine section, of the gas turbine engine, the option of arranging the detectors nearer to the combustor or to the aft end of the gas turbine engine shall not be ruled out. The choice of the most appropriate position may depend upon the ultrasound detection efficiency, the temperature distribution in the enclosure, as well as the geometry of the turbine and of the enclosure.

[0023] The ultrasonic gas leak detectors can be functionally connected to a controller 18, adapted to receive and process the signals from the detectors, and to trigger an alarm or possibly shut down the turbomachine if a hydrogen leak is detected.

[0024] In some embodiments, at least one ultrasonic gas leak detector on each side, left and right, of a median vertical plane containing the rotation axis A-A of the gas turbine engine, can be provided. In currently preferred embodiments the ultrasonic gas leak detectors are placed at an intermediate height, i.e., approximately on a horizontal plane containing the rotation axis A-A of the gas turbine engine. This position provides a good compromise between the need of protecting the detectors from excessive thermal load and the need to place the detectors in a position wherefrom ultrasonic waves generated in any angular position around the rotation axis A-A of the gas turbine engine can be detected.

[0025] In Fig.1 only ultrasonic gas leak detector(s) on one side of the gas turbine engine are shown, the other(s) not being visible in the side view.

[0026] To prevent adverse effects of temperature on the ultrasonic gas leak detectors, the latter can be positioned towards the cold side of the gas turbine engine 5, i.e. around the compressor section 5.1 thereof. This position is still sufficiently near to the position of the combustor section, where the major part of the fuel ducts are positioned, but sufficiently distanced therefrom to avoid over-heating of the detectors.

[0027] During operation, the gas turbine engine 3, the ventilation and other auxiliary systems generate sound vibrations in the audible and ultrasound ranges. Simulation tests have been carried out on a gas turbine engine and relevant enclosure to check if leakages of low molecular weight gas, such as hydrogen, can be detected by an ultrasonic gas leak detector, despite the very noisy background and if the detection is sufficiently fast (e.g., with a reaction time of less than 4 seconds) which would be required for safety reasons in case of highly flammable gases, such as hydrogen.

[0028] Technical features of these gas detectors have to be analyzed in the real operation environment to evaluate the performances of this technology. Special attention is focused on the filtering of background noise and its reflections in indoor environment, in order to isolate the signal of H2 leakages from the gas turbine noise emissions. A test campaign was performed, during which the Sound Pressure Level (SPL) of gas turbines and auxiliary systems in the range of ultrasonic frequencies has been measured. It is important to remark that different engines could have dissimilar spectrums, so this process of characterization of the background noise in the ultrasonic frequencieshas to be repeated for each model of gas turbine.

[0029] Tests were performed on aNovaLT12 turbine package, available from Nuovo Pignone s.p.a., Firenze, Italy. The gas turbine engine is located within an acoustic enclosure, which is a parallelepiped box including the gas turbine engine and hosting auxiliary skids necessary for the correct operation. During testing, the gas turbine engine drives an electric generator which power is dissipated on cooled resistances.

[0030] To evaluate which ultrasonic gas leak detector fits better in the gas turbine environment, different manufacturers of the same technology have been tested to compare performances. The detectors differ mainly in geometry, ambient temperature range, certifications, response time and sensitivity. Two models have been selected as Devices Under Test (DUT) for further testing.

[0031] A first model provides a signal which is proportional to the average value of SPL % over time, whereas the second model provides a signal which shows the frequency spectrum of the detected sound wave received in real time at the audible and ultrasonic frequencies. Two units of each detector model were installed in the enclosure, one on each side (left and right) of a median vertical plane containing the rotation axis of the gas turbine engine.

[0032] For safety reasons of the test bench, Helium (He?) was used as a surrogate of hydrogen for safety reasons. Helium has a molecular weight of 4 g / mol and, like hydrogen, is lighter than air. While helium is not as light as hydrogen, it is inert and nonflammable so it is safer than hydrogen, which is highly flammable. The ultrasonic spectrum generated by helium leaks highly similar to the spectrum generated by hydrogen leaks.

[0033] Leaks in the gas turbine enclosure were simulated by using helium contained in tanks connected to a tubing ending with orifices with different sizes. During the tests gas pressure and orifice sizes were varied to evaluate the response of ultrasonic gas leak detectors with different flow rate leakages in terms of amplitude and frequency values. The test bench was adapted in order to achieve mass flow rate values shown in Table 1 at minimum and maximum design pressure values. Typical operative pressures of the fuel gas system vary from 10 bar to 30 bar, which guarantee the emission in theultrasonic spectrum in case of a chocked flow.Table 1

[0034] Gas leaks are simulated on the gas turbine baseplate close to the fuel skid gas, since this is an area with numerous fuel gas connections.

[0035] The tests were divided in the following three phases, summarized in Table 2:Phase a: during this initial phase, at the beginning of the test, both the gas turbine engine and auxiliary systems (ventilation, lube oil, etc. . .) were off and no helium leaks were released.Phase b: during the second phase, auxiliary systems were started but the gas turbine engine were maintained non-operative. In a first stage of this second step the response of the ultrasonic gas detectors has been evaluated with no leaks, to analyze the spectrum of sound emitted by auxiliary systems without the rotation of the engine to distinguish and isolate it from the ones generated by leaks.Phase c: during the third test phase the gas turbine engine was started and accelerated till Full Speed Full Load (FSFL) conditions. In this third phase of the test the contributions to the Sound Pressure Level were from the auxiliary systems and from the gas turbine engine. The detector signals were recorded both with and without gas leak simulation (helium leak).Table 2 Test phases

[0036] The results of the tests are summarized below and shown in Figs 2A, 2B, 2C,3 A, 3B and 3C. Figs. 2A, 2B and 2C relate to step phases a and b. Figs. 3A, 3B and 3C relate to phase c.

[0037] In Figs. 2A and 3A, the intensity of the acoustic wave detected by the ultrasonic gas leak detectors of the first model are plotted on the y-axis against time. The acquisition scan time was 1 second. The acquisition signal is proportional to the intensity received from the ultrasonic gas leak detector under test and is correlated to the gas turbine engine test parameters.

[0038] In Figs. 2B, 2C and 3B, 3C the signal of the ultrasonic gas leak detectors of the second model is plotted as a function of frequency.

[0039] Fig.2A, Fig.2B and 2C show the measurement made during Phases a and b as outlined above, where the gas turbine engine is at the rest and auxiliary systems are off (Phase a) and on (Phase b), respectively. The aim of Phase b is to evaluate the background noise generated by the auxiliary.

[0040] In Fig.2A the average SPL over time is shown for the first ultrasonic gas leak detector model. Two detectors of this model were installed on each side (left and right) of a median vertical plane containing the rotation axis A-A of the gas turbine engine. Curves Cl and C2 represent the signal of the left-hand and right-hand side ultrasonic gas leak detectors of the first model. C3 is the ventilation signal.

[0041] In Figs. 2B and 2C the spectra captured in different time frames are shown. Specifically, Fig.2B shows the data collected with ventilation is off (Phase a) and Fig.2C show the data collected with ventilation on.

[0042] The window W plotted in Figs. 2B and 2C frames the ultrasonic frequencies (frequency above 20 kHz) on the x-axis and the set alarm threshold on SPL on the y- axis.

[0043] When the gas turbine engine is not running and the ventilation is off, the SPL of ultrasonic gas leak detector of the first model (providing the average value of SPL % over time) is constant and equal to 20.8%, which value is the minimum full-scale value of the instrument, see Fig.2A.

[0044] In Fig.2B the Sound Pressure Level vs. frequency on the x-axis shows small variations between 16% and 20.6%. This indicates that when the ventilation system is off and the gas turbine engine is at the rest, the background noise is negligible and no spurious alarms are detected.

[0045] When the gas turbine engine is not running and the ventilation system is on, the signal of the ventilation is activated (curve C3 in Fig.2A), the intensity of the signal increases to 22.55% for to 25% for the left-hand side (curve Cl) and right-hand side (curve C2) detectors of the first model. This means that both detectors detect the noise generated by the ventilation system which is running, but the one on the left side (curve Cl) “hears” a higher sound than the right one, because it is closer to simulated He leaks. In Fig.2C the Sound Pressure Level rises to 37% in the audible frequencies and to 26% in the ultrasonic frequencies (above 20 kHz). Therefore, the background noise generated by the activation of the ventilation system impacts mainly on the audible spectrum.

[0046] In Fig.3A, 3B and 3C, the results of measurements during Phase c are illustrated, when the auxiliary systems are on and the gas turbine engine is running up to FSFL. Measurements with and without helium leaks are plotted in all figures.

[0047] In detail, the average SPL over time is shown for the first model of ultrasonic gas leak detectors in Fig.3A, while Figs. 3B and 3C show the spectra captured in different time frame (without He leak in Fig.3B and with He leak in Fig.3C) by the ultrasonic gas leak detectors of the second model.

[0048] Specifically, when the gas turbine engine runs and there is no helium leak (left side of Fig.3A, and Fig.3B) the Sound Pressure Level achieves higher values compared to Figs. 2Aand 2B, because the noise contributions generated by the gas turbine engine rotation are added. In particular, in Fig.3Bit is possible to notice that the intensity increases homogeneously on all frequencies but with major contributions to audible frequencies.

[0049] While the gas turbine engine was running, different lines with orifices were activated to simulate He leaks. See second dotted area of Fig.3 A and Fig.3C. In Fig.3 A the signal of one ultrasonic gas leak detector (curve Cl) increases following apertureof a helium releasing orifice. The SPL bolts from 45% of the background noise to 97%. When the ultrasonic gas leak detector reaches the alarm threshold, the output signal thereof is maintained at the full scale till the alarm status is present. It is interesting to remark that the ultrasonic gas leak detector on the other side of the gas turbine engine (curve C2) does not hear the He leak and the signal thereof remains constant at the background noise level of 45%. This difference between the signals received by leftside and right-side detectors is due to the presence of the gas turbine engine, which prevents the propagation of the ultrasound wave.

[0050] Referring to Fig.3C, it is noted that the major contribution of the chocked leak is in the range of ultrasonic frequencies, because they increase more than the audible ones. In particular, many bands exceed the alarm threshold set at 52.1% so the alarm is sent to the control system. The background noise is present and it is measured, but it does not affect the gas leak detection.

[0051] Several test points have been executed varying He leaks, orifices size and gas pressure, to evaluate the impact on SPL intensity and frequencies. All the ultrasonic gas leak detectors detect gas leaks at maximum pressure value and with the biggest orifice size. On the contrary at minimum pressure and with the minimum orifice size the detector arranged opposite the leaking orifice hears only the background noise and not the sound emitted by the leak. So, the ultrasonic gas leak detector model that measures the average value of the SPL shows a difference in the detection between the device installed on the right side of the engine and the other one on the left side.

[0052] In summary, the tests performed on the NovaLT12 turbine package show that ultrasonic gas leak detectors are capable of detecting ultrasound waves generated by low-molecular weight gas leakages, such as in particular H2 leakages in a gas turbine enclosure during turbine operation, despite the high level of noise present therein. Ultrasonic gas leak detection technology is therefore a promising new approach to safe and fast gas leak detection, and meets the safety requirements for hydrogen leak detection in gas turbine engines.

[0053] Since the ultrasonic gas leak detector(s) is(are) arranged in an enclosure surrounding the gas turbine engine, it may be necessary to find the most appropriate location for the detectors inside the enclosure, where they are capable of detectinghydrogen leakages despite the strong background noise, and where the temperature conditions do not adversely affect the detection or cause damages to the detector.

[0054] In general terms, setting up an enclosure with an ultrasonic gas leak detector arrangement for detecting fuel leakages from the gas turbine engine may require a preliminary step of finding the most appropriate position of one or more detectors inside the enclosure. The most appropriate position may depend, among others, upon features of the enclosure and of the gas turbine engine, which impact on the acoustic wave distribution in the enclosure in different operating conditions of the turbomachine.

[0055] A set-up method for setting up the system including the enclosure and the turbomachine housed therein may therefore comprise the following steps. Once a set of ultrasonic gas leak detectors has been arranged in tentative positions inside the enclosure, measurements of audible and ultrasound waves through the detectors are performed under the following conditions:- ancillary devices on, gas turbine off, no gas leaks;- ancillary devices on, gas turbine off, gas leaks simulation;- ancillary devices on, gas turbine on, no gas leaks;- ancillary devices on, gas turbine on, gas leaks simulation.

[0056] The same steps can be repeated several times with different detector positions inside the enclosure, until the optimum location of the detector is found, where the ultrasonic signal generated by the simulated gas leaks is stronger and best distinguishable from the background noise. This location will be adopted as the final position for the detectors in the enclosure.

[0057] Figs. 4 to 7(C) illustrate further data collected from ultrasonic gas leak detectors in various operating conditions of the gas turbine engine.

[0058] More specifically, Fig.4 illustrates signals collected with the gas turbine engine not running and operative ancillary components in operation, specifically with ventilation and lubrication circuits in operating conditions. Time is plotted on the horizontal axis and the sound pressure level (in percentage) detected by two detectors isplotted on the vertical axis. Curves CIO and Cl 1 are the signals of two ultrasonic gas leak detectors operating in the time domain and symmetrically arranged on two opposite sides of the gas turbine engine. In the diagram of Fig.4 three time intervals are highlighted, during which He leaks through respective orifices of variable dimensions and under different He pressure conditions were generated to simulate fuel leakage. The time intervals are labeled P2, P3 and P4. The orifice diameter and helium pressure used in each leak simulation where as follows:Table 3

[0059] As shown in Fig. 4, both detectors detect the gas leakage, i.e. irrespective of whether the detector is arranged on the side of the leak, or on the opposite side.

[0060] Figs. 5(A) to 5(C) illustrate three diagrams showing the signal generated by an ultrasonic gas leak detector operating in the frequency domain. In each diagram the frequency is plotted on the horizontal axis and the sound pressure level (in percentage) detected by the detector is plotted on the vertical axis. The sequences of diagrams in Figs. 5(A), 5(B) and 5(C) correspond to the leaking conditions P2, P3, P4 listed in Table 3 above. Each diagram shows an increased signal at frequencies above 10-15 kHz, caused by the detected leakages. The frequency response is dependent upon the leaking conditions, in terms of pressure and flowrate.

[0061] The same measurements were repeated with the gas turbine engine in operation at full load and full speed. In Fig.6 time is plotted on the horizontal axis. Curves C15 and C16 are the signals from two ultrasonic gas leak detectors, arranged respectively on the same side of the leaking orifice and on the opposite side with respect to the turbine body. The leak conditions summarized in Table 4 were tested.Table 4

[0062] The diagram of Fig.6 illustrates the detector signal in the time domain for the leak simulations P27, P28 and P32 (see Table 4). The results show that the ultrasonic gas leak detectors positioned on the same side of the turbine where the leaking orifice is positioned can detect both large as well as small leakages, despite the background noise generated by the gas turbine engine. The detector positioned on the side opposite the leaking orifice is able to detect only larger leakages, due to the background noise.

[0063] Figs. 7(A) and 7(B) show diagrams of the sound pressure signal generated by a detector operating in the frequency domain and corresponding to the conditions P31 and P32 (see Table 4). Each diagram shows the detector signal on the vertical axis (sound pressure level expressed in percentage), as a function of the frequency, which is plotted on the horizontal axis. The diagrams of Figs. 7(A) and 7(B) show that the frequency-domain detector measures different sound pressure levels for different leak rates.

[0064] Summarizing, the tests discussed above show evidence that leaking helium (as a surrogate of hydrogen) inside a gas turbine enclosure can be detected with ultrasonic gas leak detectors when the auxiliary systems (ventilation and lube oil system) are operating and the gas turbine engine is shut down. In this case the ultrasonic gas leak detectors are able to detect the presence of leaks in spite of the background noise generated by the running ventilation and lubrication systems. The ultrasonic gas leak detectors are capable of detect different sound pressure generated by variable leak mass flow rates, regardless of their location. Both the time-domain signal as well as the frequency domain system provide different sound pressure level intensity values when the leak rate changes. The pressure upstream of the orifice influences the sound pressure level system similarly to the leak rate.

[0065] The same results are achieved also with the gas turbine engine running at full speed and full load. The ultrasonic gas leak detectors are able to detect the leaks in the majority of the cases. However, the detectors are not able to detect different sound pressure levels at variable leak mass flow rate in time domain, since the sound pressure signal is saturated when the gas leak is detected against a high background noise generated by the running gas turbine engine. On the other hand, however, ultrasonic gasleak detectors operating in the frequency domain are able to detect different leak flow rates since the spectrum of the signal in the frequency domain at high frequencies, typically above 10 kHz, varies as a function of the leaking flowrate.

[0066] These results surprisingly show that ultrasonic gas leak detectors can be used as reliable detectors in an enclosure of a gas turbine engine, despite the heavy noise generated therein by the gas turbine engine.

[0067] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the scope of the invention as defined in the following claims.

Claims

CLAIMS1. A turbomachine system comprising: a gas turbine engine; an enclosure surrounding the gas turbine engine and containing at least one fuel delivery duct adapted to supply a gaseous fuel to the gas turbine engine; and an ultrasonic gas leak detector arrangement housed in the enclosure and adapted to detect leakages in the enclosure of the gaseous fuel supplied to the gas turbine engine during operation of the gas turbine engine.

2. The system of claim 1, wherein the gaseous fuel comprises hydrogen.

3. The system of claim 1 or 2, wherein the ultrasonic gas leak detector arrangement comprises a plurality of ultrasonic gas leak detectors arranged around an axis of the gas turbine engine.

4. The system of any one of the preceding claims, wherein the ultrasonic gas leak detector arrangement is adapted to detect ultrasound waves around a detection frequency comprised between 20 kHz and 100 kHz, preferably between 25 kHz and 70 kHz.

5. A method for detecting flammable gas leakages in an enclosure housing a gas turbine engine, wherein the method comprises the steps of: supplying a gaseous fuel to the gas turbine engine; and detecting a leakage of the gaseous fuel in the enclosure during operation of the gas turbine engine through an ultrasonic gas leak detector arrangement.

6. The method of claim 5, wherein the gaseous fuel comprises hydrogen.

7. The method of any one of claims 5 to 6, wherein the ultrasonic gasleak detector arrangement comprises a plurality of ultrasonic gas leak detectors arranged around an axis of the gas turbine engine.

8. The method of any one of claims 5 to 7, wherein the ultrasonic gas leak detector arrangement is adapted to detect ultrasound waves around a detection frequency comprised between 10 kHz and 100 kHz, preferably between 20 kHz and 70 kHz, more preferably between 25 kHz and 70 kHz.

9. A method for setting up a system comprising: an enclosure, a gas turbine engine housed in the enclosure, and at least one duct adapted to deliver a gaseous fuel in the enclosure, the method comprising the following steps: a) positioning a set of ultrasonic gas leak detectors in the enclosure; b) collecting signals from the ultrasonic gas leak detectors under the following conditions:- ancillary devices of the gas turbine engine on, gas turbine engine off, no gas leaks;- ancillary devices of the gas turbine engine on, gas turbine engine off, gas leaks simulation;- ancillary devices of the gas turbine engine on, gas turbine engine on, no gas leaks;- ancillary devices of the gas turbine engine on, gas turbine engine on, gas leaks simulation. c) repeating steps (a) and (b) for different positions of the ultrasonic gas leak detectors; d) selecting the detector position which provides the strongest leak signal as the final position for the detectors in the enclosure.

10. The method of claim 9, wherein the gaseous fuel comprises hydrogen.

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