Air intake for a stationary gas turbine engine

Abstract

The present invention relates to an air intake for a stationary gas turbine engine, in particular an air intake for a stationary gas turbine engine comprising a vertical duct having a front wall, a rear wall, side walls and a supply opening in the rear wall. The front wall and the rear wall are flat and parallel to each other. The side walls define a diverging diffuser section of the vertical duct configured to slow down an inlet air flow flowing through the vertical duct and a converging conveyor conveyor section of the vertical duct arranged downstream of the diverging diffuser section and surrounding the supply opening and configured to redirect a portion of the inlet air flow (QA) towards the supply opening. In the diverging diffuser section, the side walls are configured to deflect the inlet air flow (QA) away from a longitudinal median plane (P) of the vertical duct (15) by a Coanda effect, thereby preventing the inlet air flow (QA) from separating from the side walls (18).

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority from European Patent Application No. 20425021.1, filed on 6 July 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to an air inlet for a stationary gas turbine engine, and to a stationary gas turbine engine. Background Technology

[0004] As is known, stationary gas turbine engines have an air inlet that directs airflow to the inlet of a compressor, typically of the axial type. The air inlet is designed to optimize the air supply to the compressor based on mass flow rate, velocity, and direction across a wide range of operating conditions. The air inlet generally includes an air louver, an air filter, a horizontal duct also known as a "dust chamber," a silencer, and a vertical duct section including a lower conveyor and a supply opening that connects to the compressor inlet.

[0005] One problem often associated with known air inlets is that airflow conditions around the inlet guide vanes and supply openings of the first compressor stage are not uniform. For example, air velocities are higher in the upper portion of the supply passage than in the lower portion, where flow stagnation, recirculation, and vortices can occur. Differences in the direction and amplitude of velocity can lead to dangerous deviations in the angle of attack at the inlet guide vanes, resulting in flow separation that can propagate along the compressor. Flow separation not only affects the performance and efficiency of gas turbine engines but can also cause critical conditions and significant problems such as forced shutdown and engine damage. Therefore, a poor air supply can pose serious risks to the operability, performance, and lifespan of engine components. Summary of the Invention

[0006] Therefore, the objective of this invention is to provide an air inlet for a stationary gas turbine engine and a stationary gas turbine engine that allows overcoming or at least mitigating the aforementioned limitations.

[0007] According to the present invention, an air inlet for a stationary gas turbine engine is provided, the air inlet comprising a vertical duct having a front wall, a rear wall, a side wall and a supply opening located in the rear wall, the front wall and the rear wall being flat and parallel to each other;

[0008] Among them, the sidewall is limited to:

[0009] a diverging diffuser section of the vertical duct configured to slow down the inlet air flow flowing through the vertical duct; and

[0010] a converging conveyor section of the vertical duct arranged downstream of the diverging diffuser section and encircling the supply opening and configured to redirect the portion of the air flow towards the supply opening;

[0011] and wherein, in the diverging diffuser section, the side walls are configured to deflect the air flow away from the longitudinal median plane of the vertical duct by Coanda effect, thereby preventing the air flow from separating from the side walls.

[0012] The diverging diffuser section induces a double beneficial effect. On the first point, the velocity of the air flow is substantially reduced, thus also reducing the differences in terms of supply conditions encircling the supply opening. In addition, the portion of the air flow is actively deflected by the curved side walls via Coanda effect and thus diverted from the upper portion of the supply opening. The diverted portion of the air flow is then redirected towards the supply opening by the converging conveyor section of the vertical duct, rather than reaching the supply opening directly from above. At the same time, the deflection by Coanda effect avoids flow separation and does not require additional elements in the flow passage such as baffles or flow guides. Such elements would likely induce critical flow conditions, possible turbulence and pressure losses. As a result, the conditions of air supply to the first stage of the axial compressor are equal over the entire supply opening and the differences as well as stagnation and flow recirculation are attenuated. Performance and efficiency are thus improved and it is possible to avoid critical conditions that can be detrimental to the operability and life of the components.

[0013] The vertical duct and the size of the occupied space are relatively small due to the flat and parallel front and rear walls. This is important because the air intake is often arranged in the space between the gas turbine engine and the electric power generator (e.g. alternator) driven by the gas turbine engine.

[0014] According to an aspect of the present invention, the side walls are configured to impart respective opposite rotations to respective portions of the air flow.

[0015] The opposite rotations help to spread the air flow symmetrically and uniformly in the diverging diffuser section and, after passing in close proximity to the supply opening, to collect the air flow components in the converging conveyor section.

[0016] According to an aspect of the present invention, the side walls have respective curved diverging portions in the diverging diffuser section and the local diverging radius of curvature of the curved diverging portions is selected to prevent flow separation in the diverging diffuser section at the maximum rated velocity of the inlet air flow.

[0017] Thus, flow separation is avoided even in the worst flow conditions, and thus over the entire operating range of the associated gas turbine engine.

[0018] According to an aspect of the application, the side wall has, downstream of the respective curved diverging portion, a respective straight diverging portion located in the diverging diffuser section.

[0019] The use of straight diverging portions makes the design of the vertical duct more flexible. Straight diverging portions can be introduced according to design preferences to obtain a desired degree of divergence also related to the height of the diverging diffuser section. Straight portions do not entail a considerable risk of flow separation.

[0020] According to an aspect of the application, the side wall has, in the converging conveyor section, a respective converging curved portion with a local converging radius of curvature, wherein the ratio of the maximum value of the local diverging radius of curvature to the minimum value of the local converging radius of curvature is comprised between 0.5 and 10.

[0021] The shape of the converging conveyor section allows to collect the air flow deflected in the diverging diffuser section and to redirect it without causing turbulence, and thus to optimize the supply of the compressor of the associated gas turbine engine.

[0022] According to an aspect of the application, the converging conveyor section comprises conveyor lobes arranged symmetrically with respect to the longitudinal median plane of the vertical duct.

[0023] According to an aspect of the application, the conveyor lobes project from the bottom of the vertical duct towards the supply opening.

[0024] The lobes help to redirect the air flow collected by the converging conveyor section towards the supply opening without causing turbulence.

[0025] According to an aspect of the application, the conveyor lobes are provided with a rounded apex with a lobe radius of curvature and are joined by a respective curved base connector with an equal base radius of curvature.

[0026] According to an aspect of the application, the ratio of the lobe radius of curvature to each of the base radius of curvature is comprised between 0.9 and 1.1, and the lobe radius of curvature and the base radius of curvature are preferably equal to or greater than 200 mm.

[0027] The positive influence of the lobes is thus optimized. Moreover, due to the shape of the diverging diffuser section and the shape of the converging conveyor section, the air flow reaching the zone of the lobes is relatively ordered and has low turbulence. Thus, the small and smooth bumpers provide a sufficient redirection of the flow and cause negligible pressure losses, which in contrast can be considerable with respect to directing elements such as the tip of a separator.

[0028] According to an aspect of the application, the diverging diffuser section has a minimum width at the upstream end, a maximum width at the downstream end, and a diffuser height from the upstream end to the downstream end, and a divergence parameter is between 0.02 and 0.5, preferably between 0.05 and 0.2, the divergence parameter being defined by WMax, WMin and HDiff are the maximum width, the minimum width and the diffuser height of the diverging diffuser section, respectively.

[0029] The lower extreme of this range is sufficient to cause a significant deflection of the air flow and an improvement in the conditions of the air flow fed to the compressor as a result. Within the upper extreme, safety conditions are defined which prevent separation of the air flow.

[0030] According to an aspect of the application, the maximum width is not more than twice the minimum width.

[0031] The risk of separation is thus negligible.

[0032] According to an aspect of the application, the supply opening is arranged symmetrically with respect to the longitudinal median plane.

[0033] According to an aspect of the application, the side wall is specularly symmetrical with respect to the longitudinal median plane.

[0034] The symmetry of this arrangement favours a uniform supply condition, and to a lesser extent, the risk of undesirable effects such as turbulence.

[0035] According to an aspect of the application, the vertical duct comprises an inlet section upstream of the diverging diffuser section, the side wall being straight and parallel in the inlet section.

[0036] According to an aspect of the application, the air intake further comprises an air conditioning hole, an air filter, a silencer and a horizontal duct upstream of the vertical duct.

[0037] According to an aspect of the application, there is also provided a stationary gas turbine engine comprising:

[0038] an air intake as defined above;

[0039] an axial compressor having a compressor inlet coupled to the air intake and configured to receive an inlet air flow from the air intake. BRIEF DESCRIPTION OF DRAWINGS

[0040] The application will now be described with reference to the accompanying drawings, which illustrate some non-limiting embodiments of the application, in which:

[0041] - Figure 1 is a schematic view of a power plant;

[0042] - Figure 2 is a cross-sectional elevation view of a portion of an air intake made in a power plant and according to an embodiment of the present application taken along line II-II of Figure 1 Figure 1

[0043] - Figure 3 is an enlarged detail of a portion of a vertical duct of Figure 2

[0044] - Figure 4 is a cross-sectional elevation view of a portion of an air intake made for a stationary gas turbine engine and according to a different embodiment of the present application; and

[0045] - Figure 5 is a cross-sectional elevation view of a portion of an air intake made for a stationary gas turbine engine and according to another embodiment of the present application. DETAILED DESCRIPTION

[0046] With reference to Figure 1 , a power plant is indicated by the reference number 1 and comprises a stationary gas turbine engine 2 and an alternator 3 driven by a shaft 4 of the gas turbine engine 2. The stationary gas turbine engine 2, in turn, comprises an air intake 5, a compressor 7 of axial type, a combustion chamber 8 and a turbine 10.

[0047] An inlet of the compressor 7, in particular a first stage of orientable inlet guide vanes 7a, is coupled to the air intake 5 for receiving an inlet air flow QA, which is added with a fuel flow QF and burnt in the combustion chamber 8. An exhaust gas flow QE is expanded in the turbine 10 to extract mechanical energy for driving the alternator 3.

[0048] The inlet air flow QA is supplied to the compressor 7 through the air intake 5, which is partly arranged around the shaft 4 between the alternator 3 and the compressor 7.

[0049] In one embodiment of the present application, the air intake 5 comprises an air conditioning aperture 11, a filtering section 12, a horizontal duct 13 and a vertical duct 15. As illustrated in Figure 2 , air is sucked from the outside through the air conditioning aperture 11 and the filtering section 12, flows through the horizontal duct 13 and the vertical duct 15 and is delivered to the compressor 7 through a supply opening 50 provided in the vertical duct 15. A silencer 14 Figure 1 may be arranged in the horizontal duct 13 or in the vertical duct 15 according to design preferences as in the embodiments of Figure 1 and Figure 2 .

[0050] ​​​The vertical duct 15 is arranged between the alternator 3 and the compressor 7 and has a front wall 16 facing the alternator 3, a rear wall 17 facing the compressor 7, and side walls 18. Figure 2 Figure 1 As illustrated in the figures, the front wall 16 and the rear wall 17 are flat and parallel to each other. The side walls 18 are specularly symmetrical with respect to a longitudinal median plane P of the vertical duct 15.

[0051] The vertical duct 15 comprises, successively along a flow direction of the inlet air flowing through the air inlet 5, an inlet section 19, a diverging diffuser section 20, and a converging conveyor section 21.

[0052] In the inlet section 19, which is connected to the horizontal duct 13 by a bend, the side walls 18 are straight and parallel to each other. Moreover, in the inlet section 19, the vertical duct 15 has a minimum width WMin. In a not shown embodiment, there is no inlet section, and the diverging diffuser section 20 is directly connected to the bend and to the horizontal duct 13.

[0053] In the diverging diffuser section 20, the side walls 18 have curved diverging portions 18a configured to impart opposite diverging rotations to respective portions of the inlet air flow QA. In the converging conveyor section 21, the side walls 18 have curved converging portions 18b configured to impart respective converging opposite rotations to respective portions of the inlet air flow QA, thus opposite to each other and to the curved diverging portions 18a of the respective side walls 18.

[0054] The diverging diffuser section 20 is configured to slow down the inlet air flow QA flowing through the vertical duct 15. In particular, in the diverging diffuser section 20, the side walls 18 are configured to deflect portions of the inlet air flow QA away from the longitudinal median plane P by Coanda effect, so as to prevent the air flow from separating from the side walls 18. In one embodiment, the diverging curved portions 18a of the side walls 18 extend throughout the diverging diffuser section 20. In any case, a local diverging radius of curvature Rl of the side walls 18 is selected to prevent flow separation in the diverging diffuser section 20 at the maximum rated speed of the inlet air flow QA. The term "diverging" applied to the radius of curvature will be understood to mean that the curvature of the side walls 18 is such that a small portion of the inlet air flow QA flowing along the side walls 18 is deflected away from the longitudinal median plane P. The local diverging radius of curvature Rl need not be constant in the diverging diffuser section 20 and can vary from an upstream end 20a located at the junction with the inlet section 19 to a downstream end 20b located at the junction with the converging conveyor section 21.

[0055] ​The diverging diffuser section has a minimum width WMin at the upstream end 20a and a maximum width WMax at the downstream end 20b and a diffuser height HDiff from the upstream end 20a to the downstream end 20b. For example, if the divergence parameter D defined by If the divergence parameter D defined is between 0.02 and 0.5, the air flow can be prevented from separating from the side wall 18 and, if the divergence parameter D is between 0.05 and 0.2, the flow conditions are optimized. Furthermore, the maximum width WMax is not more than twice the minimum width WMin.

[0056] The converging conveyor section 21 of the vertical duct 15 is arranged downstream of the diverging diffuser section 20 and the supply opening 50 is formed in the back wall 18 symmetrically with respect to the longitudinal median plane P in the converging conveyor section 21. Thus, the converging conveyor section 21 extends around the supply opening 50.

[0057] The converging conveyor section 21 is configured to redirect portions of the inlet air flow QA towards the supply opening 50. In particular, the converging conveyor section 21 collects small portions of the inlet air flow QA that are deflected by the diverging diffuser section 20 and pass the supply opening 50 without entering directly. To this end, the converging curved portion 18b of the side wall 18 in the converging conveyor section 21 has a local converging radius of curvature R2. The term "converging" applied to the radius of curvature will be understood to mean that the curvature of the side wall 18 locally deflects small portions of the inlet air flow QA flowing along the side wall 18 towards the longitudinal median plane P. Furthermore, since the side wall 18 joins at the bottom of the converging conveyor section 21 at the longitudinal median plane P, the small portions of the inlet air flow QA are finally redirected from below towards the supply opening 50. The local converging radius of curvature R2 can be constant or variable along the converging curved portion 18b according to design preferences. For example, in the converging conveyor section 21, the local converging radius of curvature R2 is chosen such that the ratio of the maximum of the local diverging radius of curvature Rl to the minimum of the local converging radius of curvature R2 is comprised between 0.5 and 10. In some embodiments, not shown here, the converging curved portion 18b can also comprise straight portions according to design preferences.

[0058] No edge is provided in the diverging diffuser section 20 or in the converging conveyor section 21.

[0059] The converging conveyor section 21 comprises a conveyor bump 22 arranged symmetrically with respect to the longitudinal median plane P of the vertical duct 15. The conveyor bump 22 protrudes from the bottom of the converging conveyor section 21 of the vertical duct 15 towards the supply opening 50 and is configured to deflect portions of the inlet air flow QA upwards to the supply opening 50.

[0060] The conveyor bump 22 has a circular vertex 22a with a bump curvature radius R3, and the curved convergent portion 18b of the sidewall 18 in the convergent conveyor section 21 is smoothly connected by a corresponding curved base connector 22b with an equal base curvature radius R4. Furthermore, the ratio of each of the bump curvature radius R3 and the base curvature radius R4 is included between 0.9 and 1.1, and the curvature radius R3 and the base curvature radius R4 are preferably equal to or greater than 200 mm.

[0061] according to Figure 4 The embodiment of the invention shown is replaced by an air inlet indicated by reference numeral 105. Figures 1-3 The vertical duct 115 includes a vertical duct 115 having sidewalls 118, and for the remainder is similar to the disclosed air inlet 5. The vertical duct 115 has an inlet section 119, a diffuser section 120, and substantially as already described for… Figures 1-3 The converging conveyor section 21 is discussed in relation to the converging conveyor section 121. In the diverging diffuser section 120, the sidewall 118 has a corresponding curved diverging portion 118a and a corresponding straight diverging portion 118c located downstream of the corresponding curved diverging portion 118a.

[0062] according to Figure 5 In one embodiment, in the air inlet 205 for a stationary gas turbine engine, the vertical duct 215 has a sidewall 218 and includes an inlet section 219, a convergent conveyor section 221, and a divergent diffuser section 220, which is substantially as already described. In the convergent conveyor section 221, the sidewall 218 is connected to the longitudinal midline plane P without any protrusions.

[0063] Ultimately, it is evident that changes and modifications can be made to the illustrated air inlet without departing from the scope of protection of the appended claims.

Claims

1. An air inlet for a stationary gas turbine engine, comprising a vertical duct (15; 115; 215) having a front wall (16), a rear wall (17), side walls (18; 118; 218) and a supply opening (50) located in the rear wall (17), the front wall (16) and the rear wall (17) being flat and parallel to each other; in, The sidewalls (18; 118; 218) define: The divergence diffuser section (20; 120; 220) of the vertical duct (15; 115; 215) is configured to slow the inlet airflow (QA) through the vertical duct (15; 115; 215); and The convergent conveyor section (21; 121; 221) of the vertical duct (15; 115; 215) is arranged downstream of the divergent diffuser section (20; 120; 220) and around the supply opening (50), and is configured to redirect a portion of the inlet airflow (QA) toward the supply opening (50). Furthermore, in the diffuser section (20; 120; 220), the sidewall (18; 118; 218) is configured to deflect the inlet airflow (QA) away from the longitudinal midplane (P) of the vertical duct (15; 115; 215) via the Coanda effect, thereby preventing the inlet airflow (QA) from separating from the sidewall (18; 118; 218); The sidewalls (18; 118; 218) have corresponding curved diverging portions (18a; 118a) in the diverging diffuser sections (20; 120; 220), and the local diverging radius of curvature (R1) of the curved diverging portions (18a; 118a) is selected to prevent flow separation in the diverging diffuser sections (20; 120; 220) at the maximum rated velocity of the inlet airflow (QA).

2. The air inlet according to claim 1, wherein, The sidewalls (18; 118; 218) are configured to impart a corresponding opposite rotation to the corresponding portion of the inlet airflow (QA).

3. The air inlet according to claim 1, wherein, The sidewall (118) has a corresponding straight diverging portion (118c) located in the diverging diffuser section (120) downstream of the corresponding curved diverging portion (118a).

4. The air inlet according to claim 1, wherein, The sidewall (18) has a corresponding convergent bend (18b) in the convergent conveyor section (21; 121; 221) having a local convergent radius of curvature (R2), wherein the ratio of the maximum value of the local divergent radius of curvature (R1) to the minimum value of the local convergent radius of curvature (R2) is included between 0.5 and 10.

5. The air inlet according to claim 1, wherein, The convergent conveyor section (21; 121) includes a conveyor bump (22) which is arranged symmetrically with respect to the longitudinal midplane (P) of the vertical conduit (15; 115).

6. The air inlet according to claim 5, wherein, The conveyor protrusion (22) protrudes from the bottom of the vertical conduit (15; 115) toward the supply opening (50).

7. The air inlet according to claim 5, wherein, The conveyor bump (22) has a circular vertex (22a) with a bump curvature radius (R3) and the sidewall (18) is connected by a corresponding curved base connector (22b) with an equal base curvature radius (R4).

8. The air inlet according to claim 7, wherein, The ratio of each of the bump curvature radius (R3) and the base curvature radius (R4) is included between 0.9 and 1.

1.

9. The air inlet according to claim 7, wherein, The radius of curvature (R3) and the radius of curvature of the base (R4) are equal to or greater than 200 mm.

10. The air inlet according to claim 1, wherein, The diverging diffuser sections (20; 120; 220) have a minimum width (WMin) at the upstream end (20a), a maximum width (WMax) at the downstream end (20b), and a diffuser height (HDiff) from the upstream end (20a) to the downstream end (20b), wherein the divergence parameter (D) is between 0.02 and 0.5, the divergence parameter (D) being determined by... WMax, WMin, and HDiff are defined as the maximum width, minimum width, and diffuser height of the divergent section (20; 120; 220), respectively.

11. The air inlet according to claim 10, wherein, The divergence parameter (D) is between 0.05 and 0.

2.

12. The air inlet according to claim 10, wherein, The maximum width (WMax) is no greater than twice the minimum width (WMin).

13. The air inlet according to claim 1, wherein, The supply opening (50) is arranged symmetrically with respect to the longitudinal central plane (P), and the sidewalls (18; 118; 218) are mirror-symmetrical with respect to the longitudinal central plane (P).

14. The air inlet according to claim 1, wherein, The vertical duct (15; 115; 215) includes an inlet section (19; 119; 219) located upstream of the divergent section (20; 120; 220), and the sidewalls (18; 118; 218) are straight and parallel in the inlet section (19; 219).

15. The air inlet according to claim 1, further comprising an air conditioning hole (11), an air filter (12), a silencer (14), and a horizontal duct (13) located upstream of the vertical duct (15; 115; 215).

16. A stationary gas turbine engine, comprising: The air inlet (5; 105;) according to any of the preceding claims 205)； An axial compressor (7) has a compressor inlet (7a) connected to the air inlet (5; 105; 205) and configured to receive an inlet airflow (QA) from the air inlet (5; 105; 205).

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