WO2017222516A1

WO2017222516A1 - Method and system for reducing liquid droplet impact damage by superhydrophobic surfaces

Info

Publication number: WO2017222516A1
Application number: PCT/US2016/038707
Authority: WO
Inventors: Pawel JEDRZEJOWSKI; Walter Kasimierz Omielan; Ali Dolatabadi; Mason MARZBALI; Moussa TEMBELY
Original assignee: Siemens Aktiengesellschaft
Priority date: 2016-06-22
Filing date: 2016-06-22
Publication date: 2017-12-28

Abstract

The present disclosure is directed to systems and processes which prevent fluid droplet impact damage by surface engineering a respective component (2) to exhibit a water receding contact angle ≥ about 120 degrees upon contact with droplets (6) having a Weber number ≤ 2. The system may comprise a gas turbine engine with a water injection device for wet air compression.

Description

METHOD AND SYSTEM FOR REDUCING LIQUID DROPLET IMPACT DAMAGE BY SUPERHYDROPHOBIC SURFACES

FIELD

The present disclosure relates generally to engineered surfaces, and also to systems and processes for reducing or preventing erosion stemming from fluid droplets.

BACKGROUND

Turbine power plants, such as gas turbines, are used in a variety of useful applications. Aviation, shipping, power generation, and chemical processing have all benefited from turbine power plants of various designs. Turbine power plants (e.g., combustion turbines) typically have a compressor section for compressing inlet air, a combustion section for combining the compressed inlet air with fuel and oxidizing that fuel, and a turbine section where the energy from the hot gas produced by the oxidation of the fuel is converted into work. Typically, natural gas (mostly methane), kerosene, or synthetic gas (such as carbon monoxide) is fed as fuel to the combustion section, but other fuels may be used. The rotor - defined by a rotor shaft, attached turbine section rotor blades, and attached compressor section rotor blades - mechanically powers the compressor section and, in some cases, a compressor used in a chemical process or an electric generator. The exhaust gas from the turbine section can be used to achieve thrust; it also can be a source of heat and energy or, in some cases, it is discarded.

It is known that materials, such as water, can also be added when a turbine power plant is operating to augment the power output capability of the turbine power plant, thereby increasing the power output capability above that achievable with normally humidified or ambient air. Such a procedure is known as wet compression. Wet compression enables power augmentation in turbine power plants by reducing the work required for compression of the inlet air. This thermodynamic benefit is realized within the compressor of a gas turbine through "latent heat intercooling." In latent heat intercooling, water (or some other appropriate liquid) added to the air and inducted into the compressor cools the air through evaporation as the air is being compressed. The added water can be conceptualized as an "evaporative liquid heat sink".

The wet compression approach thus saves an incremental amount of work (which would have been needed to compress air not containing the added water) and makes the incremental amount of work available to either drive the load attached to the gas turbine (in the case of a single shaft machine) or to increase the compressor speed to provide more mass flow (which can have value in both single shaft and multiple shaft machines). Thus, by introducing droplets into the flowing air stream in the compressor section of turbine, the temperature of the air stream may be reduced as it is being compressed, thereby decreasing the energy required for compression therein, and thereby increasing power output and efficiency of the associated turbine. Various methods and apparatuses have been employed to facilitate the introduction of fluid (i.e. , water) to the working fluid of turbine power plants so as to realize the benefits of wet compression.

SUMMARY

While the benefits of wet compression are many, the present inventors have found that the introduction of fluid droplets during wet compression may result in erosion damage due to the coalescence of the smaller droplets into larger droplets on component surfaces in the compressor. Once formed, the larger droplets may re-enter the flowing gas stream from such component surfaces, and cause greater damage to component(s) than the originally-sized smaller droplets upon contact therewith. While one approach may be to apply a hydrophobic coating to retard droplet coalescence, aspects of the present invention are directed to the finding that not all hydrophobic coatings are equally efficient. In particular, in certain environments, not all hydrophobic coatings will prevent or reduce impact or related damage from certain fluid droplets. In particular, in accordance with one aspect, the present inventors have found through significant analytical and numerical modeling along with experimental testing that in order to have sufficient mobility of droplets on the wetted surface for droplets having a Weber number, We, of less than or equal to about 2, a substrate will need to have a surface modification that exhibits a water receding contact angle > about 120° upon contact with the droplets to prevent coalescence of the droplets thereon. If the water droplet receding contact angle on the surface is less than about 120° in such cases, the substrate will be insufficient to prevent or sufficiently reduce droplet coalescence on a surface thereof. At higher Weber numbers, the rebound can happen for receding angles as low as 1 10°. In certain embodiments, the surface modification comprises a hydrophobic coating on the surface of the substrate.

Thus, in accordance with an aspect of the present invention, there is provided a method for reducing or eliminating damage to a component being subjected to droplets having a Weber number (We) of about 2 or less, the method comprising modifying a surface of the component such that the surface exhibits a water receding contact angle≥ about 120° upon contact with said droplets.

As mentioned above, one exemplary application for the systems and processes described herein is in the area of gas turbine engines, including those comprising a wet compression system as is known in the art.

Specifically, the present inventors have found that one issue associated with the operation of a wet compression system is that fluid droplets introduced into a flowing air stream of the compressor may coalesce into larger droplets following contact with components downstream from their point of

introduction, such as on static components of the compressor section. In some instances, these droplets may increase in size, mobilize or re-atomize from the component, and re-enter the flowing air stream being compressed. These coalesced fluid droplets may travel at high speeds and impact a second component, such as a rotating blade, of the compressor section and cause considerable damage thereto. Although the principles of the present invention are discussed in the context of a gas turbine and, by way of example, a compressor section of a gas turbine having a wet air compression system, it is appreciated that the present invention is not so limited and the principles and embodiments described may be applied in and to other suitable systems and components.

In accordance with another aspect, there is provided method for reducing or eliminating damage to a second component in a system comprising a first component and the second component, at least the first component being subjected to first fluid droplets having a Weber number (We) < 2, the method comprising:

modifying a surface of the first component such that the surface exhibits a water receding contact angle≥ 120° upon contact with the first fluid droplets and such that the modified surface is effective to prevent or reduce coalescence of the first fluid droplets into a film or into second fluid droplets larger than the first fluid droplets on the first component;

wherein, but for the modified surface, the film or second fluid droplets would form to a greater degree, enter the flowing air stream, and impact the second component, thereby causing damage thereto.

In accordance with another aspect, the coatings with large receding contact angles described herein increase droplet mobility and reduce opportunity for fluid coalescence on the first component. In this way, the formation of larger particles on the first component, which may cause significant damage downstream, is avoided. In certain embodiments, droplets having a greatest dimension of > 100 μιη are hereby avoided by application of the coating to the first component. The present inventors have found, in fact, that increased droplet size may exponentially increase component damage. Therefore, reducing fluid droplet coalescence may have substantial impact toward reducing component damage and increasing product lifetime.

In accordance with another aspect, there is provided a method for reducing liquid impingement damage in an engine having a compressor section, a combustor section, and a turbine section, the compressor section comprising repeating stages of at least one stationary component and of at least one rotating component for compression of a flowing air stream, the method comprising:

providing the at least one stationary component with a surface which exhibits a water receding contact angle > about 120° upon contact with first fluid droplets having a Weber number < about 2;

operating the compressor section to generate an amount of compressed air; and

injecting the first fluid droplets into the flowing air stream in an amount effective to provide an amount of cooling to the flowing air stream, the fluid droplets having the Weber number < about 2 upon contact with the at least one stationary component;

wherein the surface of the at least one stationary component is effective to limit fluid droplet coalescence on the at least one stationary component, thereby reducing or eliminating a likelihood of downstream fluid droplet impact damage to the at least one rotating component.

In accordance with another aspect, there is provided a component comprising a surface that exhibits a water receding contact angle≥ about 120 degrees upon contact with droplets having a Weber number (We)≤ 2. In an embodiment, the surface modification comprises a hydrophobic coating on a surface of the component.

In accordance with another aspect, there is provided a system for reducing liquid impingement damage comprising:

a first component, a second component, a flowing gas stream over the first and second component, and a source of first fluid droplets in

communication with the flowing gas stream for introducing the first fluid droplets into the flowing gas stream;

wherein the first component comprises a surface that exhibits a water receding contact angle > about 120 degrees upon contact with the first fluid droplets, the first fluid droplets having a Weber number (We) < 2, thereby preventing coalescence of the first fluid droplets on the surface of the first component.

In accordance with another aspect, there is provided a gas turbine engine comprising:

a compressor section comprising at least one stationary component and at least one rotating component configured to generate compressed air at an outlet thereof;

a combustion section for combusting fuel and an amount of the compressed air from the compressor section to produce a working gas;

a turbine section downstream of the combustor section receiving the working gas; and

a wet air compression system configured for introducing a plurality of fluid droplets into a flowing air stream of the compressor section;

wherein the at least one stationary component of the compressor section comprises a coating that exhibits a water receding contact angle > about 120 degrees upon contact with first fluid droplets having a Weber number (We) < 2, thereby preventing coalescence of the first fluid droplets on a surface of the at least one stationary component. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a system for reducing liquid impingement damage in accordance with an aspect of the present invention.

FIG. 2 is schematic of a gas turbine engine configured to reduce liquid impingement damage therein in accordance with an aspect of the present invention.

FIG. 3 illustrates a portion of a gas turbine engine having a wet compression system in accordance with an aspect of the present invention.

FIG. 4 illustrates the formation of larger damage-causing droplets in a typical prior art system.

FIG. 5 illustrates a turbine vane having a coating in accordance with an aspect of the present invention. FIG. 6 illustrates a plot of Weber number vs. receding angle in accordance with an aspect of the present invention.

DETAI LED DESCRI PTION

The present inventors have developed systems and processes to reduce damage caused by impacting fluid droplets via increasing droplet mobility and reducing fluid droplet coalescence on subject component(s). Referring to the figures, there is shown in FIG. 5 an exemplary component, e.g., component 2, in accordance with an aspect of the present invention. As will be explained in further detail below, the component 2 includes a surface, e.g., engineered surface 8, that exhibits a water receding contact angle > about 120 degrees upon contact with moving droplets having a Weber number (We)≤ 2. In this way, the likelihood that such droplets will coalesce and form either larger droplets or a thin film on the component is substantially eliminated or reduced. Instead, the fluid droplets may readily slide (rebound) off the surface 8 when contacting the same. In some embodiments, the component 2 is at least slightly tilted or angled when exposed to a flow of a flowing gas stream.

In accordance with one aspect, the engineered surface 8 comprises a coating 7 as shown in FIG. 5 which is applied to an outer portion of a body of the component 2 and forms an external surface thereon. The coating 7 may be any suitable material providing the desired properties described herein (a water receding contact angle≥ about 120° upon contact with moving droplets having a We≤ 2).

The coating 7 may comprise any suitable thickness effective to provide the desired water receding contact angle. Without limitation, the coating 7 may have a thickness of from about 0.001 mm to about 3 mm. As used herein, the term "about" refers to a value which is ± 5% of the stated value. Further, when a coating 7 is present, the coating 7 may be applied on an outer portion of the component 2 by any suitable method such as by a chemical vapor deposition (CVD), physical vapor deposition (PVD), thermal spraying, slurry or paint application. Of note, in the embodiment shown in FIG. 5, the component 2 is illustrated as being a turbine component, e.g., a vane 20, as is known in the art. However, it is understood that the present invention is not so limited.

To reiterate, the present inventors have found that a surface must have a minimum receding angle in order to properly dispel fluid droplets having a relatively small Weber number, e.g. < about 2. If the receding angle is not large enough, the coating will simply be ineffective or not as effective as desired when being contacted by such droplets. To explain the concept of a Weber number further, fluid droplet impact conditions on a given component can be characterized by the Weber number (We) as follows:

We=p_wv²Da^"1 ,

where p_w is the water density, v is a droplet velocity component normal to the surface, D is droplet diameter, and σ is surface tension. As the Weber number increases, the droplets become more difficult to disperse from a surface.

For purposes of the invention, the Weber number for the subject droplets may be measured by any suitable technique known in the art. In an embodiment, the droplet diameter may be measured using a laser diffraction technique. Further, the water receding contact angle of the surface 8 may be measured by any suitable technique known in the art. By way of example, the water receding contact angle may be determined by procedures as disclosed in Burnett et al, J. Vac. Sci. Techn. B, 23(6), pages 2721-2727 (Nov/Dec 2005).

In one aspect, discrete phase modeling of air and water droplets in a compressor showed a We below 8 in front of the first static component in the compressor. The values were confirmed by extensive experimentation and measurements in a compressor rig operating under the same conditions in terms of air flow, air speed, volume of injected water and droplet sizes as a real turbine engine. During such experimentation, the present inventors have found via simulating water droplet impact and film formation, a relationship between We values and minimum receding contact angle 6_R that will prevent film formation on components.

Referring to FIG. 6, for example, there was shown that when the We was < about 2, the water receding contact angle, 0_R, needs to be > about 120° in order to fully remove the droplets from the subject surface. These values are higher than typical hydrophobic coatings wherein 9_R < 1 10 degrees, for example. FIG. 6 presents results of numerical simulation of droplet impact for different impact speeds and surface properties. In the figure, empty symbols represent wetting behavior where the droplet either splashes or stays on a surface. Full symbols represent droplets rebounding from a surface. The dashed line represents the numerical solution of the rebound condition.

As shown, the ability for a droplet to rebound from a surface may be influenced by both its respective Weber number (We) and a receding contact angle for the surface. As shown in FIG. 6, for low Weber numbers (x axis), a droplet rebounds only for high receding contact angles (y axis). Overall, the lower the We number, the higher the receding contact angle should be in order for the droplet to rebound. For moderate We (e.g., ~5) impacts, the receding contact angle plays a role in determining the wetting region. For a Weber number We > 2, rebound can occur for receding contact angles as low as 1 10°. Very large Weber numbers may also lead to droplet splashing. Again, for lower Weber numbers, higher receding contact angles are necessary for rebound.

In accordance with another aspect, the present invention is not so limited to forming the subject receding angle of≥ 120° by applying a coating thereto. In other embodiments, it is also understood that the term "engineered surface" as used herein may also refer to a surface which has been physically or chemically modified to achieve the desired surface properties required herein. Exemplary surface modifications include, but are not limited to: laser patterning; electro-deposition; surface etching or engraving; surface patterning by additive manufacturing; and overlay coating with materials having a desired surface morphology or a combination of all those methods. FIG. 1 illustrates a component 2 described above in a system 1 for reducing fluid droplet impact damage in accordance with an aspect of the present invention. In the embodiment shown, the system 1 comprises the component 2 (first component), a second component 3, a flowing gas stream 4 from a suitable source (not shown) which may flow past or over the first component 2 and the second component 3 at a suitable flow rate. A source 5 of first fluid droplets is in communication with the flowing gas stream 4 and may be configured to introduce first fluid droplets 6 into the flowing gas stream 4.

In this embodiment, the first component 2 comprises an engineered surface 8 as described above that exhibits a water receding contact angle greater than about 120° upon contact with droplets having a Weber number > 2. The surface 8 is effective to increase mobility of the first fluid droplets 6 upon contact of such droplets with the surface 8. This means that instead of resting on a surface 8 of the first component 2 and coalescing into larger droplet fluid particles or a continuous film, the engineered surface 8 (e.g., a surface coated with a coating 7 as described herein) helps maintain the original droplet size distribution of the first fluid droplets 6, or minimally larger ones, moving into the flowing gas stream 4 as shown in FIG. 1 .

In contrast, without the engineered surface 8, as shown in FIG. 4, droplets may coalesce on the first component 2 into larger droplets or a continuous film which may be carried and/or re-atomize into flowing stream 4 and contact the second component 3. Since larger droplets or the continuous film tend to cause further downstream damage, damage to the second component 3 would occur. However, since such coalescence into larger droplets or a continuous film is prevented by aspects of the present invention, impact by such larger droplets 9 is hereby reduced since the larger droplets 9 are substantially prevented from forming on the first component 2. It is noted for purposes of illustration, larger droplets 9 are shown on component 2; however, by "coalesce" it is also understood, however, that droplets may instead form a continuous film on the component 2 that could result in the formation of larger droplets 9 therefrom which re-enter the flowing stream 4.

In certain embodiments, the first component 2 may be a stationary component while the second component 3 may be a rotating component, although it is understood the present invention is not so limited. Rotating components which are themselves moving, may be particularly prone to stress, strain, erosion, and damage caused by impact of fluid droplets, especially those with a Weber number≥ 2. In other embodiments, the first component 2 may be a rotating component and the second component 3 may be a stationary or a rotating component.

By way of example, FIG. 2 illustrates a more particular embodiment of a system and process for reducing fluid droplet impact damage involving a stationary component and a rotating component in a gas turbine engine environment. In particular, FIG. 2 shows a gas turbine engine 10 employing aspects of the present invention and including an inlet section 1 1 , a compressor section 12, a combustor section 14, a turbine section 16, and an exhaust 17.

The compressor section 12 compresses ambient air 18 that enters the inlet section 1 1 . Within the compressor section 12, there are rows of vanes 20 and rows of rotating blades 22 coupled to a rotor that may define a first component 2 and a second component 3, respectively. Each pair of rows of vanes 20 and blades 22 forms a stage in the compressor section 12. In an embodiment, the vane 20 may comprise a VSV (Variable Stator Vane) which may be more static compared to the rotor, but articulates on its own axis to control the air flow into the compressor

The compressor section 12 serves as an air pump, converting low pressure, low density ambient air drawn into the compressor section 12 into high pressure air prior to delivering the high pressure air to the combustor section 14. The high pressure air 18 flowing through the compressor section 12 may define a flowing gas stream 4 as described above. In some embodiments, the compressor section 12 raises the temperature of the air by about 550°F as the air is compressed.

In an exemplary axial flow compressor, the compressor section 12 includes fourteen stages. Each stage incrementally boosts the pressure from the previous stage. Within each stage, one or more vanes 20 may be positioned at an angle such that the exiting air is directed toward one or more rotor blades 22 of the next stage at the most efficient angle. By way of example, the process may be repeated fourteen times as the air flows from the first stage through the fourteenth stage.

In addition to the fourteen stages of blades and vanes, the inlet section

1 1 and/or the compressor section 12 may also include inlet vanes 24, e.g. , variable inlet guide vanes, and outlet guide vanes (not shown). The inlet vane 24 may neither be divergent or convergent. I n an embodiment, the inlet guide vanes 24 direct air to the first stage compressor blades at the "best" angle. The outlet guide vanes, on the other hand, "straighten" the air to provide the combustor section 14 with the proper airflow direction.

In certain embodiments, the turbine 1 0 may employ a wet air compression system 26, such as an Inlet Spray Intercooling (ISI) System, configured to introduce a plurality of droplets 6 of a fluid, such as water, into the flowing gas stream 4 of the compressor section 12. The system 26 may thus define a first fluid droplet source 5 as described above. In a particular embodiment, the system 26 introduces first fluid droplets 6 to the flowing gas stream 4 upstream of the compressor section 12 or within the inlet section 1 1 . Referring to FIG. 3, there is shown an exemplary system 26, e.g., an ISI system, comprising a spray bar 28 which is configured to deliver a plurality of first fluid droplets 6 toward flowing gas stream 4 flowing through a portion of the compressor section 12.

The first fluid droplets 6 may be of any suitable size, composition, and may be in any suitable form. In certain embodiments, the droplets comprise water. In addition, in certain embodiments, the droplets 6 may have a particle size of 0.01 to 0.10 mm. In this context, the first fluid droplets 6 may be effective to reduce ambient inlet temperature to the compressor section 12 and decrease the energy required for compression of the air stream therein, thereby increasing power output and efficiency of the turbine 10, for example. For purposes of showing the utility of the present invention in different turbine systems, a different turbine from that of FIG. 2 is shown in FIG. 3.

Referring again to FIG. 2, once compressed, the combustor section 14 combines the compressed air with a fuel and ignites the mixture creating combustion products comprising a hot working gas defining a working fluid. The working fluid then travels to the turbine section 16. Within the turbine section 16 are rows of stationary vanes 32 and rows of rotating blades 34 coupled to a rotor. Each pair of rows of vanes 32 and blades 34 may similarly form a stage in the turbine section 16. The rows of vanes 32 and rows of blades 34 extend radially into an axial flowpath extending through the turbine section 16. The working fluid expands through the turbine section 16 and causes the blades 34, and therefore the rotor to rotate. The rotor extends into and through the compressor 12, and may provide power to the compressor section 12 and output power to an electrical generator, compressor, pump, or other equipment.

The present inventors have recognized that not all of the added first fluid droplets 6 will be evaporated, and that without intervention the first fluid droplets 6 may tend to coalesce and form even larger second fluid droplets 9 or a continuous film on components of the compressor section 12. In addition, the present inventors have found that without intervention such larger second fluid droplets may be carried or re-atomized by the flowing gas stream 4 off a first component 2, such as vane 20 or 24, and impact a second component 3, such as blade 22, thereby causing damage to the second component 3. This may particularly be the case at the high velocities of the air stream (flowing gas stream 4) being compressed in the compressor section 12. The above phenomenon is again depicted by way of example in FIG.4. As mentioned, in certain embodiments, the second component 3 may comprise a rotating component, such as blade 22, of the compressor section 12 while the first component 2 may comprise a stationary component thereof, such as a stationary vane 20 or 24. In some instances, the second fluid droplets 9 may comprise coalesced fluid droplets on the surfaces of a stationary component of the inlet section 1 1 and/or compressor section 12. These coalesced droplets 9 may become increasingly more destructive the larger they grow. In fact, there is an exponential relationship between droplet size and component damage - meaning the larger the droplet size formed, the vastly greater amount of damage which may be brought about by the large droplets.

Accordingly, aspects of the present invention again aim to reduce and/or substantially eliminate the coalescence of water droplets on the surface of a first component 2, which could result in the formation of larger- sized second fluid droplets 9 that may cause damage to components downstream of the first component 2. In particular, aspects of the present invention propose to accomplish the same by surface engineering

component(s) of the associated system. For example, in the above-discussed gas turbine 10, any components of the inlet section 1 1 and/or compressor section 10 may be surface engineered, such as by applying a suitable coating 7 thereto, to exhibit a high water fluid receding contact angle as described herein in order to reduce and/or prevent the coalescence of first fluid droplets 6 into larger second fluid droplets or a continuous film.

By way of example and referring again to FIG. 5, there is shown a vane 20 of the compressor section 12 comprising an engineered surface 8, e.g., coating 7, to effect a water receding contact angle≥ about 120 degrees upon contact with droplets having a Weber number < about 2. The coating 7 may thus be effective to prevent the coalescence of fluid droplets thereon into larger droplets or a film thereon. In the gas turbine engine 10 described, the smaller droplet sizes thus maintained in the compressor section 12 may thus result in considerably less damage to components of the gas turbine 10, such as rotating components of the compressor section 12, since the larger the fluid particles formed, the larger the damage caused by impact by the fluid particles.

It is again appreciated that although the engineered surfaces 8 described herein are shown in a gas turbine 10 comprising a wet air compression system 26, the present invention is not so limited and this example is merely illustrative. It is appreciated that the principles applied herein may be applied in other applications. For example, the coating 7 may be applied on a static component of a low pressure steam turbine to avoid condensation as illustrated in FIG. 4 and erosion of a downstream steam turbine blade. The engineered surfaces 8 may also be brought about in other applications, such as in within aeroengines to reduce the erosion of the engine core components when exposed to snow, rain, and the like. In another exemplary application, the engineered surfaces 8 described herein may be utilized so as to decrease damage due to ice accretion (due to the reduced ability of water to accumulate on the surface 8 due to the coating 7 or the like).

The function and advantages of these and other embodiments of the present invention will be more fully understood from the following examples. These examples are intended to be illustrative in nature and are not considered to be limiting the scope of the invention.

While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.

Claims

CLAIMS The invention claimed is:

1 . A method for reducing or eliminating damage to a component (2) being subjected to droplets (6) having a Weber number (We)≤ 2, the method comprising:

modifying a surface of the component (2) such that the surface (8) exhibits a water receding contact angle > about 120° upon contact with said droplets (6).

2. The method of claim 1 , wherein the modifying comprises providing a coating (7) on said component (2) which exhibits a water receding contact angle≥ about 120° upon contact with said droplets (6).

3. The method of claim 2, wherein the coating (7) comprises a thickness of from about 0.001 to 3.000 mm.

4. The method of claim 1 , wherein the modifying comprises a physical modification to a surface (8) of the component (2).

5. The method of claim 1 , wherein the component (2) comprises a component of a gas turbine engine (1 0).

6. A method for reducing or eliminating damage to a second component (3) in a system (1 ) comprising a first component (2) and the second component (3), at least the first component (2) being subjected to first fluid droplets (6) having a Weber number (We)≤ 2, the method comprising: modifying a surface of the first component (2) such that the surface exhibits a water receding contact angle > 120° upon contact with said first fluid droplets (6) and such that the modified surface (8) is effective to prevent or reduce coalescence of the first fluid droplets (2) into a film or into second fluid droplets (9) larger than the first fluid droplets (2) on the first component; wherein, but for the modified surface, the film or second fluid droplets

(9) would form to a greater degree, enter the flowing air stream (4), and impact the second component (3), thereby causing damage thereto.

7. The method of claim 6, wherein the first component (2) comprises a static component within a compressor section(12) of a gas turbine engine (10), and wherein the second component (3) comprises a rotating component within the compressor section (12) of the gas turbine engine (10).

8. The method of claim 6, wherein the system (1 ) comprises a gas turbine engine (10) and a source of fluid droplets (5), and wherein the source of fluid droplets (5) comprises a wet compression system (26) for a compressor section (12) of the gas turbine engine (10).

9. The method of claim 6, wherein the modifying comprises providing a coating (7) on said component (2) which exhibits a water receding contact angle > about 120° upon contact with said droplets (6).

10. The method of claim 6, wherein the coating (7) comprises a thickness of from about 0.001 to 3.000 mm.

1 1 . A method for reducing liquid impingement damage in an engine (10) having a compressor section (12), a combustor section (14), and a turbine section (16), the compressor section (14) comprising repeating stages of at least one stationary component (2) and of at least one rotating component (3) for compression of a flowing air stream (4), the method comprising:

providing the at least one stationary component (2) with a surface (8) which exhibits a water receding contact angle≥ about 120° upon contact with first fluid droplets (6) having a Weber number < about 2;

operating the compressor section (12) to generate an amount of compressed air; and

injecting the first fluid droplets (6) into the flowing air stream (4) in an amount effective to provide an amount of cooling to the flowing air stream (4), the first fluid droplets (6) having the Weber number≤ about 2 upon contact with the at least one stationary component (2);

wherein the surface (8) of the at least one stationary component (2) is effective to limit fluid droplet coalescence on the at least one stationary component (2), thereby reducing or eliminating a likelihood of downstream fluid droplet impact damage to the at least one rotating component (3).

12. The method of claim 1 1 , wherein the modifying comprises providing a coating (7) on the at least one stationary component (2) which exhibits a water receding contact angle≥ about 120 degrees upon contact with the first fluid droplets (6).

13. The method of claim 1 1 , wherein the at least one stationary component (2) comprises a stationary vane, and wherein the at least one rotating component (3) comprises a rotating blade.

14. A component (2) comprising a surface (8) that exhibits a water receding contact angle≥ about 120 degrees upon contact with droplets having a Weber number (We)≤ 2.

15. The component (2) of claim 14, wherein the surface (8) comprises a coating (7) on an outer portion of the component (2), and wherein the coating (7) exhibits a water receding contact angle greater than about 120 degrees upon contact with the droplets (6) having a Weber number (We)≤ 2.

16. The component (2) of claim 14, wherein the coating (7) comprises a thickness of from about 0.001 to 3.000 mm.

17. The component (2) of claim 14, wherein the component (2) comprises a component of a gas turbine engine (10).

18. A system (1 ) for reducing liquid impingement damage comprising:

a first component (2), a second component (3), a flowing gas stream (4) over the first (2) and second component (3), and a source (5) of first fluid droplets (6) in communication with the flowing gas stream (4) for introducing the first fluid droplets (6) into the flowing gas stream (4);

wherein the first component (2) comprises a surface (8) that exhibits a water receding contact angle≥ about 120 degrees upon contact with the first fluid droplets (6), the first fluid droplets (6) having a Weber number (We)≤ 2, thereby preventing coalescence of the first fluid droplets (6) on the surface (8) of the first component (2).

19. The system (1 ) of claim 18, wherein the surface comprises a coating (7) on a body of the component (2) that exhibits a water receding contact angle > about 120 degrees upon contact with the first fluid droplets (6) having a Weber number (We)≤ 2.

20. The system (1 ) of claim 18, wherein the first component (2) comprises a static component of a gas turbine engine (10), and wherein the second component (3) comprises a rotating component of the gas turbine engine (10).

21 . The system (1 ) of claim 18, wherein the system (1 ) comprises a gas turbine engine (10), and wherein the source (5) of first fluid droplets (6) comprises a wet air compression system (26) for a compressor section (12) of the gas turbine (10).

22. A gas turbine engine (10) comprising:

a compressor section (12) comprising at least one stationary component (2) and at least one rotating component (3) configured to generate compressed air at an outlet thereof;

a combustion section (14) for combusting fuel and an amount of the compressed air from the compressor section (12) to produce a working gas; a turbine section (14) downstream of the combustor section (12) receiving the working gas;

a wet air compression system (26) configured for introducing a plurality of first fluid droplets (6) into a flowing air stream (4) of the compressor section

(12); and

wherein the at least one stationary component (2) of the compressor section comprises a coating (7) that exhibits a water receding contact angle≥ about 120 degrees upon contact with first fluid droplets (6) having a Weber number (We) < 2, thereby preventing coalescence of the first fluid droplets (6) on a surface of the at least one stationary component (2).