A METHOD FOR PREVENTING DEPOSITS RESULTING From a THERMAL HYDROCARBON DEGRADATION ON ARTICLES

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B09-1065FR

Society said: GENERAL ELECTRIC COMPANY

METHOD FOR PREVENTING DEPOSITS FROM A HYDROCARBON THERMAL DEGRADATION OF ARTICLES

The invention of: VARANASI Kripa Kiran

BHATE Nitin

Jeffrey GOLDMEER Scott

Geoffrey David MYERS

Priority a patent application deposited in the United States of America under No. 12/100,029 9 April 2008

The present invention relates generally to the deposits formed on surfaces in contact with hydrocarbon fluids and, more particularly, to surfaces having a texture designed to prevent the formation of carbonaceous deposits, soot and oil. The present invention also relates to articles having such surfaces and to methods of making such articles and surfaces.

At direction of the present disclosure, is to determine as a whole as hydrocarbon fluids hydrocarbon liquids, hydrocarbon gases or mixtures thereof. At purposes of the present description, the expression "degradation products of hydrocarbon fluids" covers products formed from hydrocarbons, e. g., certain polymers resulting from the thermal conversion of paraffins to naphthenes, of aromatic and polycyclic molecules in the hydrocarbon, as well as products resulting from the decomposition of the fuel itself, such as carbon.

Since a high temperature is generally associated with undesirable levels of forming deposits of hydrocarbon fluids, which is discussed herein is commonly so-called thermal instability or, in the case of fuels, fuel instability. Circulation hydrocarbon fluids, lubricating oils, hydraulic oils, fuels used as fuel and other can form soot deposits, deposits and carbonaceous deposits of oil to the surface of containment walls and other parts that they contact when the fluid and/or heat up the surface. For example, coking occurs has the solidification of liquid fuels in the form of carbonaceous deposits which tend to form on heated surfaces in contact with the liquid fuels. An illustrative, as examples Process and system affected by such deposits, the petrochemical processes, tool machines, motor engines, gas turbine engines of aircraft, marine engines and industrial and other in which surface deposits formed from fluids, fuels and hydrocarbon oils are a significant problem. The deposits can foul the heat exchangers, the fuel injectors associated with spark plugs and the dispensing nozzles for lubrication, the control valves for the prevention of jamming, and create problems with many other types of actuators and associated control fluids, fuels and hydrocarbon oils. Furthermore, such deposition risk of reducing the flow rate, increase the operating pressures in the fuel lines and lessen the performance of the injection system and/or combustion, or of the overall process, of the system or engine.

In one example, solid deposits and varnish deposits appear on inner and outer surfaces, wetted by a liquid fuel, the fuel feed system. In addition to the fuel injectors, other parts wetted by the fuel, the collectors of which, metering valves, valves and distribution valves vent/check exposed to both the fuel and the air at high temperature or high ambient temperatures at risk of suffering from carbonaceous formation of deposits and carbon. The conditions for coking occurs depend upon the composition of the fuel, the concentration of the dissolved oxygen, the surface roughness, the composition of the surface and many other variables that affect the rate of formation of carbonaceous deposits in a hydrocarbon fuel. The current practice is to limit 149 °C (300 °F) or less to the temperature of the surfaces wetted by the fuel, in order to minimize carbon formation. This is difficult to achieve in conventional ambient conditions of a gas turbine where temperatures delivery compressors for machines compression ratio/relatively low performance exceed 370 °C (700 °F), and, for the more efficient systems, exceed 540 °C (1000 °F).

A second type of carbon formation, which may extend to combustion systems supplied by a liquid or gas occurs when solid carbon particles and soot accumulate on the members of the combustion systems. Such carbon deposits, commonly called "clinker" adversely affect the distribution of the air and the fuel in the combustion chamber, causing increased emissions, temperatures of the metals of the parts and a deformation of the temperature profile in the outlet of the combustion chamber, of which reduces the life of the members present downstream. Such carbon deposits solids can also cause erosion of the rotating vanes profiles turbines, maintaining performance and life time, when the large "clinker" are dislodged by vibrations, an air flow or differential thermal expansion and disintegrate in the downstream turbine. Since the collisions between the large carbon deposits and the vanes profiles can occur at a relative speed very high (hundreds or even thousands of m/s), and that the carbon is remarkably hard in this form, the erosion of surfaces vanes profiles a problem of life.

An area particularly troublesome for the engines on the aircraft wing and derivatives, liquid fuel, is posed by the splash plate. On these types of engines, carbonaceous deposits can accumulate on the splash plate and, finally, coking can flaking and damaging the coatings for thermal barrier on the members of the combustion chamber. Such problems can have heavy consequences on the operational capabilities of the engine. Another worrying in area of the carbonaceous deposits in gas turbine engines is current constituted by the fuel lines leading to the combustion chamber. If the temperature of the fuel lines is in a certain temperature range, carbonaceous deposits can form within of the fuel lines, thereby increasing pressure required pumping and/or limits the flow of fuel to the engine.

As discussed above, a method for alleviating the accumulation of carbonaceous and other deposits in the fuel lines and other contact surfaces of turbine engines has been to maintain the temperature sufficiently low to prevent occurs a reaction of forming a carbonaceous deposition. In this case the turbine engines are forced to operate at temperatures lower than the optimum values and, therefore, they may lack efficiency. Alternatively, cooling devices have been added in the combustion system to maintain the temperatures lower surfaces without sacrificing the optimal temperatures ignition. However, make these devices more expensive and complex designs to turbine engines. Another method has been to be applied to the surfaces a catalyst or a coating, sometimes called barrier coating of carbonaceous deposits (CBC), said coatings being devised to prevent thermal chemically deposits adhering to surfaces. Again, the special coating increase the cost and adds a further machining step in the design of a turbine engine. Furthermore, some current coatings are unsuitable for each type of thermal deposition which may occur in the combustion system. Still another method to solve the problem of thermal deposits has been to modify using additives the hydrocarbon fuel. However, the fuel is intended to be pre-treated prior to use, must be purchased or special fuels which are already mixed in the additives, which is cost.

A surface for a metallic article which prevents the formation of deposits thermal, in particular a surface preventing carbon deposits, without resorting to a change in the hydrocarbon fluid, without adopting special procedures and without installing special equipments is therefore desirable for the current liquid fuel turbines and the like.

In the present disclosure are disclosed are methods of making a surface adapted to prevent the formation of thermal deposits.

In one embodiment, a method for preventing deposits by thermal degradation of hydrocarbons on a surface of a gas turbine component comprises carrying out the turbine part comprising the surface configured to be in contact with a hydrocarbon fluid, the substrate being formed of a material to nominal wettability by the liquid sufficient to create, with respect to an oil, a nominal angle of contact, providing a plurality of ridges on the substrate to form a surface texture anti-deposition, the elevations having different dimensions, a shape and orientation selected such that the surface has a effective wettability sufficient to create, with respect to an oil, a contact angle larger than the effective nominal angle of contact, and the elevations having a width dimension (a) and a spacing dimension (b), the reliefs preventing the hydrocarbon fluid from entering the surface texture and thereby reducing adhesion thermal hydrocarbon deposits on the surface.

In another embodiment, a method for preventing deposits of coke on a surface of a gas turbine component comprises carrying out the turbine part comprising a surface adapted to contact a hydrocarbon fluid, the substrate being formed of a material to nominal wettability by the liquid sufficient to create, with respect to an oil, a nominal angle of contact, providing a plurality of ridges on the substrate to form a surface texture carbonaceous deposit control, the plurality of elevations having dimensions, a shape and orientation selected such that the surface has a effective wettability sufficient to create, with respect to an oil, a contact angle greater than the effective nominal contact angle, and the elevations having a width dimension (a) and a spacing dimension (b), the reliefs preventing the hydrocarbon fluid from entering the surface texture and thereby reducing the adhesion of carbonaceous deposits on the surface.

A combustion system for a gas turbine engine may include a combustion chamber adapted to contain a hydrocarbon fluid injected into the combustion system, and a splash plate disposed at one end of the combustion chamber nearest the point of injection of a hydrocarbon fluid, and having a surface adapted to contact the hydrocarbon fluid, the splash plate being produced from a material with nominal wettability by the liquid sufficient to create, with respect to an oil, a nominal angle of contact; a plurality of elevations disposed on the surface of the splash plate to form a surface texture carbonaceous deposit control, the different elevations having dimensions, a shape and orientation selected such that the surface has a effective wettability sufficient to create, with respect to an oil, a contact angle larger than the effective nominal angle of contact; and the elevations having a width dimension (a) and a spacing dimension (b), the dimensions preventing the hydrocarbon fluid from entering the surface texture and thereby reducing the adhesion of a carbonaceous deposition on the surface, and a ratio b/a is less than about 2, and a ratio h/a is less than about 5.

The invention will be better understood with the study of the detailed description of some embodiments taken by way of non-limiting example and illustrated by the appended drawings on which:

figure 1 is a schematic sectional of a gas turbine engine;

figure 2 is a sectional schematic view of a combustion system used with the gas turbine engine of Figure 1;

figure 3 is a schematic sectional of a gas turbine engine or industrial high capacity terrestrial used in a plant;

figure 4 is a sectional schematic view of a combustion system used with the gas turbine engine of Figure 3;

figure 5 is a sectional schematic view of an example embodiment of the surface of an article having the texture;

figure 6 is a sectional schematic view of a fluid disposed on a nominally planar surface;

figure 7 illustrates graphically the theoretical parameters for reliefs-like columns on a surface to remove the droplets striking thereof at different rates;

figure 8 illustrates graphically the theoretical parameters for pores (such as a cavity) serving as a surface relief, rather than columns;

figure 9 represents in graphical form a further comparison between Laplace pressures (P_L ) capillary pressures and (Pc) for the spacing of reliefs in columns;

and

figures 10 and 11 illustrate graphically the fraction of surface area available for adhesion of deposits carbonaceous, for respective reliefs in the form of columns and reliefs in the form of pores.

The present disclosure is directed to surfaces that prevent build-up of thermal deposits, such as carbonaceous deposits, soot, carbon particles, and other. As described herein, the use of textures oleophobic surfaces can prevent the accumulation of such deposits by preventing the oil highly wetting the surface. The texture described can promote the fall of the oil droplets and prevent the oil to reach to the temperature required for the formation of carbonaceous deposits. The use of a suitable texture also prevents that cores carbonaceous deposits sticking onto the surface, by preventing the formation of other carbonaceous deposits. The variant surface texture described herein are adapted to prevent penetration of oil droplets in the surface texture, by reducing adhesion carbonaceous deposits on the surface.

Expression "oleophobic surface" is used generally to designate the physical property of repelling oil of a molecule or a surface. At purposes of the present description, the expressions "oleophobic surface" and "oleophobic surface texture" are more particularly for designating any surface which repels a hydrocarbon fuel and prevents the formation of deposits by thermal degradation from the fuel. Although the invention does not relate to or is limited to a liquid fuel hydrocarbon particular, typical fuels for which the surfaces may be adapted, and typical fuels are protected against which the substrates of the article may include hydrocarbon fuel gases such as natural gas, and hydrocarbon fuels or in the form of distillates, which may contain a hydrocarbon and distillation products thereof, which are generally liquid at room temperature. The fuels can be mixtures of hydrocarbons, mixtures of such distillation products, mixtures of hydrocarbons and distillation products, gasoline, diesel fuels No. L or no.2, fuels for jet engines, such that the fuel Jet-A, fuel oils or any of the aforementioned fuels mixed with additives well known in the art. The can hear by liquid fuels hydrocarbon-based liquid fuels normally used in jet engines, which, but not limited to, industrial gas turbines, the stepping motors used as internal combustion engines or alternative, which, but not limited to, the motors to automobiles and trucks, aircraft jet, any other gas turbine engine and other.

Oleophobic The surfaces described herein may be employed with any piece adapted to contact or for holding a liquid fuel hydrocarbon to high temperature, e.g. jet engine liquid hydrocarbon or a diesel fuel engine, brought to a temperature at which degradation products are formed in the hydrocarbon. Examples not-limiting such articles or parts of the conduits for transporting of a liquid fuel, heat exchangers, ovens of fuel storage tanks, surfaces fuel injection, injectors, liners and other combustion systems. To provide a surface finish "release" to the surfaces close to the fuel injector where soot rich in carbon can accumulate, so that large deposits are less likely to form and that, if they are formed, they fall in the form of particles of relative size much smaller, without causing as much erosion of parts mounted on the passage of hot gases.

Recital drawings in general and, in particular, Figure 1, it will be understood that the illustrations are used to describe a particular embodiment of the surface and the article described herein and are not intended to be limited thereto. Figure 1 is a sectional schematic view of an example gas turbine engine. The will evoke herein is the use of the treatments oleophobic surfaces in the combustion system of the gas turbine liquid. However, it is understood that surface treatments described herein may be advantageously employed in any system or method wherein thermal deposits from hydrocarbon fuels, such as carbonaceous deposits, soot, carbon and other to appear on the surface of metals, to help reduce the performance and the life of these systems.

For gas turbine engines, the carbonaceous deposit control surfaces can greatly improve the capabilities of the motors in the combustion system, and also preventing the limiting the flow of fuel to the engine by the obstruction of fuel lines by carbonaceous deposits. Additionally, textured surfaces oleophobic in turbine engines can suppress the need for additives for the fuel or cooling members active in the combustion system. As a specific example, a splash plate textured surface oleophobic can prevent the accumulation of carbonaceous deposits thereon. By limiting coking occurs on the splash plate, is strongly reduced the risk of carbonaceous deposits is anneal away and damaging the surfaces adjacent barrier coating and, thereby, extending the life of the turbine.

Figure 1 shows an example of embodiment of a gas turbine engine 10 comprising a fan assembly 12, a high pressure compressor 14 and a combustion system 16. The engine 10 also includes a high pressure turbine 18, a low pressure turbine 20 and an accelerator 22. The blower assembly 12 includes a series of fan blades 24 extending radially outwardly from a rotor disc 26. The engine 10 has an intake side 28 and an exhaust side 30.

During operation, air passes in the blower assembly 12 and compressed air is supplied to the high pressure compressor 14. The high compressed air is delivered to the combustion system 16. The airflow from the combustor 16 drives the turbines 18 and 20, and the turbine 20 drives the blower assembly 12.

Figure 2 is a cross-sectional view of the combustion system 16 used in the engine gas turbine 10. The combustion system 16 may include an annular outer liner 40, an annular inner liner 42 and a rounded end 44 extending between the inner and outer jacket, 40 and 42 respectively. The outer jacket 40 and the inner liner 42 define a combustion chamber 46.

The combustion chamber 46 is generally annular and may be disposed between the liners 40 and 42. The outer and inner liners 40 and 42 extend to a distributor 56 turbine arranged downstream of the convex end 44 combustion system. In the example of embodiment, the outer and inner liners 40 and 42 each comprise a plurality of panels 58 which include a series of steps 60 each of which forms a separate portion liners 40 and 42 of the combustion system. The convex end 44 of the combustion system can include a set of annular dome 70 having an annular configuration. The dome assembly 70 the combustor is configured to provide mechanical support for an upstream end 72 of the combustion system 16, and the dome assembly 70 includes a dome plate or bezel plate 74 and a cone assembly 76 splash-flaring. The splash cone assembly 76 is a single part and has a portion 77 splash.

The combustion system 16 can be supplied with fuel via a fuel injector 80 connected to a source of fuel (not shown) and through the convex end 44 of the combustion system. More particularly, the fuel injector 80 extends through dome assembly 70 and discharges fuel in a direction (not shown) which is substantially concentric relative to a central longitudinal axis of symmetry 82 of the combustion system. The combustion system 16 may also include a fuel ignition generator 84 which extends into the combustion system 16 downstream of the fuel injector 80. The combustion system 16 further includes a air turbulence 90 to annular outlet extending substantially symmetrically about the central longitudinal axis of symmetry 82.

Part splash plate 77 is constructed to prevent hot combustion gases produced within the combustion system 16 and of the pulverized fuel from the injector 80 do not create splashes impinging on the domed plate of the combustion system. Therefore, the splash plate itself may be susceptible to thermal formation of deposits because of the degradation of hydrocarbon fuel its surface, because the function of the splash plate is direct the flow of hydrocarbon fuel and of carbonaceous gases away from other parts. In some cases, as these carbonaceous deposits and these oil deposits continue to accumulate, they can flaking during operation and impinge upon other surfaces of the combustion system 16. This may cause damage in the combustion system and to the possibilities of damage thereof. By arranging a splash plate and/or other parts in contact with the hydrocarbon fuel heated by textures oleophobic surfaces, it is possible to mitigate or reduce quite the formation of deposits by thermal degradation on the surfaces of the parts. In some embodiments, a surface deposit control carbonaceous to texture composed of surface relief (described in more detail hereinafter) may be provided over the entire surface of the splash plate. However, in some cases, the surface texture carbonaceous deposit control may be necessary or desirable that at a portion of the surface.

Recital maintaining another application where the oleophobic surfaces described herein would be desirable, in Fig. 3 is illustrated a stationary gas turbine to use 40 to the ground, having a can-annular combustion system 410. Figure 4 is a cross-sectional view enlarged of the combustion system 410 shown in Figure 3. Each combustion system 410 comprises a substantially cylindrical casing 412 combustion system. The rear or proximal end of the housing combustion system is closed by a end cap assembly 414 which contains supply pipes, collectors and the corresponding fitting to provide the combustion system a hydrocarbon fuel, air and water. The end cap assembly 414 receives a plurality (e.g. three to six) "outer" sets fuel injection 416 (only one of which is shown in Figure 4 for convenience and clarity), arranged in a circular array about a longitudinal axis of the combustion system, and a central injector.

Inside the casing 410 the combustor is mounted, substantially concentrically thereto, a substantially cylindrical flow sleeve 418 connected, at its front end, to the outer wall of the transition duct 420 422 double-walled. The flow sleeve 418 is connected, in its rear end, by a radial flange 424, the housing 412 combustion system wherein join the front and rear sections of the housing 412 combustion system.

Within the sleeve 418 flow is disposed concentrically a jacket 430 combustion system which, at its front end, is connected to the inner wall of the transition duct 422. The liner 430 the combustor is supported by a lid assembly liner and combustion system by a plurality of supports and of mounting assemblies (not shown in detail) within the housing 412 of the combustion system.

As with the splash plate of the combustion system in the aircraft turbine engine, the surface of the fuel injectors 416 and 430 of the liner of the combustion system are areas of the turbine combustion system employed to the ground which may be subject to carbonaceous deposits and carbon deposits. The fuel hydrocarbon liquid and the hydrocarbon gas can be burned directly in contact, and the same coating the surfaces of the injectors and jacket combustion system. Thermal The accumulation of deposits on the injector, outside chipping and cause damage to the inner surfaces, disturbing the passage of the hydrocarbon fuel to the combustion system itself. This can lead to increasing the required pumping pressure and/or impeding the passage of fuel to the engine. Therefore, the surfaces of the fuel injector and the combustor liners are parts of the combustion system that would benefit from oleophobic surfaces for pushing the hydrocarbon-based liquid fuels.

At purposes of the present description, the expression "contact angle" or "static contact angle" designates the angle, measured at the interface substrate, formed between a stationary droplet of a reference liquid and a horizontal surface on which there is the droplet. The contact angle serves as a measure of the wettability of the surface. If the liquid spreads completely on the surface and forms a film, the contact angle is 0 degree. More the contact angle increases, the wettability decreases more. The treatments of oleophobic surfaces described so far will be maintaining generally called "anti-deposits surface carbonaceous" to facilitate the explanations. Expression "carbonaceous deposit control surface" is intended to describe a surface which has a substantially reduced tendency to the wettability by oils. A surface carbonaceous deposit control also promotes the oil droplets drop more easily than the surfaces according to the prior art. A textured surface carbonaceous deposit control described herein prevents oil films in the texture of the surface, resulting in a strong decrease of adhesion carbonaceous deposits on the surface. The carbonaceous deposit control surfaces are characterized by a reduced accumulation thermal deposits compared to surfaces without the processing described.

The splash plate 77 and the interior surfaces of the combustion system 16 of Figure 2 are one example of articles can advantageously include surfaces carbonaceous deposit control in combustion systems of aircraft and turbine aeronautics derivatives. Also, the fuel injector 416 and the liner 430 combustion system of Figure 4 are exemplary of items ideal for resisting surfaces deposits carbonaceous in combustion systems for ground use turbine. However, it is understood that these surfaces carbonaceous deposit control may be useful in any combustion system wherein a liquid fuel hydrocarbon is in contact with a heated surface. Treatments of surfaces in areas where the hydrocarbon fluid heated contacts a surface (i.e. surfaces subject to coking occurs), such that the splash plate, can provide surface properties carbonaceous deposit control, anti-soot and other.

Recital maintaining Fig. 5, it is shown a sectional schematic view of a surface subjected to coking occurs an article according to an exemplary embodiment of the present invention. The article 100 comprises a surface 120. At direction of the present disclosure, the term "surface" denotes the portion of the article 100 directly in contact with a hydrocarbon fluid surrounding the article 100. The surface may comprise the substrate, the reliefs or the surface modification layer disposed over the substrate, according to the specific configuration of the article. The surface 120 has a low wettability by the liquid. A measure commonly admitted for the wettability by a surface 120 is the value of the static contact angle formed between the surface 40 120 130 and a tangent to a surface of a droplet 150 a reference liquid at the point of contact between the surface 120 and the droplet 150. High values of the contact angle 140 indicate a low wettability for the reference liquid on the surface 120. The reference liquid may be any liquid. The reference liquid used for the system and methods described above may be a liquid which contains at least one hydrocarbon. In a particular embodiment, the reference liquid is an oil. Examples not limiting oils of petroleum-based products such as crude oil and products obtained in the distillation thereof, such as kerosene, gasoline, no. 1 or no. 2 diesel fuels, jet engine fuels, such as Jet-A, paraffin and other. At purposes of the present description, the expression "oil-resistant" will be heard as qualifying a surface that generates with oil a static angle of contact of at least about 30 degrees. Since the wettability is dependent in part on the surface tension of the reference liquid, a surface data may have a different wettability (and thus form a different contact angle) for different liquids.

The surface 120 consists of a material with nominal wettability by the liquid sufficient to generate, with respect to an oil, a nominal angle of contact of at least about 30 degrees. For understanding the invention, a "nominal angle contact" 340 (Figure 6), designates the static angle contact 340 multiplied when a droplet of a reference liquid 360 320 is placed on a smooth surface (surface roughness < 1 nm) consisting essentially of the material. Contact 340 The nominal angle is a measure of the "nominal wettability" of the material. In one embodiment, the nominal angle of contact, in the case of an oil, is at least about 30 degrees, in particular at least about 70 degrees, more particularly at least about 100 degrees and even more particularly at least about 120 degrees.

The surface 120 (Figure 5) is made of at least one material selected from the group comprising a ceramic and an intermetallic compound. The ceramic materials which are suitable include oxides, carbides, nitrides, borides inorganic and combinations thereof. An illustrative not as-limiting examples of such ceramic materials aluminum nitride, boron nitride, chromium nitride, silicon carbide, silica, tin oxide, titanium oxide, titanium carbonitride, titanium nitride, titanium oxynitride, the stibinite (SbS2), zirconia, hafnium oxide, zirconium nitride and combinations thereof. In some embodiments, the surface is made of an intermetallic compound. An illustrative not as-limiting examples of suitable intermetallic compounds of nickel aluminide, titanium aluminide and combinations thereof. The material is selected based on the desired contact angle, the manufacturing technique used and the final application of the article.

The surface 120 further comprises a texture with a plurality of reliefs 160. By providing a surface 120, produced from a material with relatively high nominal wettability, a specific texture, as described in detail below, the textured surface can be used for a much lower wettability to that able to the material of the surface. In particular, the surface 120 has, for the reference liquid, effective wettability (i.e. a wettability of the textured surface) sufficient to generate an effective contact angle greater than the nominal angle of contact. In one embodiment, the angle of effective contact is higher by at least about 5 degrees to the nominal angle of contact, in particular higher by at least about 10 degrees to the nominal angle of contact, more particularly greater than at least about 20 degrees to the nominal angle of contact and, even more particularly, higher by at least about 30 degrees to the nominal angle of contact. The angle of effective contact is dependent in part on the form, dimensions and spacings of the reliefs, as described in detail below.

As described above, the surface 120 has a texture comprising a plurality of reliefs 160. The embossments 160 of the plurality of embossments may have any shape, which at least one of recesses, projections, nanoporous solids, notches or other. The embossments may include bumps, cones, rods, columns, wires, channels, reliefs substantially spherical, substantially cylindrical reliefs, of pyramid-shaped protrusions, prismatic structures, combinations thereof, and other. Many varieties of relief formed are suitable to serve as reliefs 160. In some embodiments, as shown in the Lig. 5, at least a subset of the plurality of reliefs 160 projects above the surface 120 of the article. In some embodiments, at least a subset of the plurality of reliefs 160 is a plurality of cavities (e.g., pores) 170 arranged in the surface 120. In some embodiments, at least a subset of the reliefs 160 has a shape selected from the group consisting of a cube, a rectangular prism, a cone, a cylinder, a pyramid, a trapezoidal prism and a hemisphere or other spherical portion. These forms are useful regardless of whether the protrusion or a projection or a cavity 170 160.

The dimensions of the reliefs 160 (Figure 5) may be characterized in a number of ways. The embossments 160 comprise a height dimension (h) 200, which represents the height of raised protrusions above the surface 120 or, in the case of cavities 170, the depth to which the cavities extend in the surface 120. The embossments 160 further comprise a width dimension (a) 220. The precise nature of the width dimension will depend on the shape of the relief, but is defined as the width of the relief at the point where the relief would be naturally into contact with a droplet of a liquid arranged at the surface of the article. The parameters of height and width 160 reliefs have a large effect on the wetting behavior observed on the surface 120.

The orientation of the reliefs is another theoretical consideration in the study of techniques of the wettability of a surface. An important aspect of the orientation of the reliefs is formed by the spacing of the reliefs. With reference to Figure 3, in some embodiments the reliefs 160 are arranged in a spaced-apart manner, characterized by a spacing dimension

(b) 240. The spacing dimension 240 is defined as the distance between the edges of two protrusions the most closely adjacent. Other aspects of orientation may also be taken into account, such as the extent to which the top 250 (or the bottom 260 for a cavity) deviates from an orientation parallel to the surface 120, or the extent to which the reliefs 160 deviates from a perpendicular orientation with respect to the surface 120.

In some embodiments, all of the features of the plurality of reliefs 160 have substantially the same respective values for h, a and/or b ("an ordered set"), although this is not a general requirement. For example, the plurality of reliefs 160 can be a collection of embossments have a random distribution of dimensions, shape and/or orientation. In some embodiments, further, the plurality of protrusions is characterized by a multi-modal distribution (for example a bimodal distribution or a trimodal) in h, a, b or any combination of these dimensions. Such distributions may advantageously provide a reduced wettability in environments where meet droplets of various sizes. Therefore, the estimating the effects of h, a and b on the wettability is carried out in the best taking into account the distributive nature of these parameters. The embossments may vary in any parameter and must be suitable to create a surface which prevents that droplets from penetrating the surface relief, for connection of the to a reduced contact between coking and the textured surface. Therefore, it is understood that when the parameters a, b, and other h are described herein in the context of the plurality of reliefs rather than individual reliefs, these parameters are to be interpreted as representing average values for the plurality of reliefs considered in terms of a population.

Many applications for surfaces with low wettability, such as carbonaceous deposit control surfaces, require a sufficiently large contact angle for oil, independently of a low level of friction and other forces of contact between the droplet and the surface which promote accumulation of carbonaceous deposits. The shape, the dimensions and spacing of the reliefs, as well as the composition of the material of the surface, all influence the wettability of the surface. Therefore, it is possible to choose the dimensions and spacings of the reliefs so that the effective angle of contact for the oil is optimal to reduce thermal deposits (e.g. carbonaceous deposits) on the surface. The surfaces so designed and constructed have a wettability selected for the oil to characteristics carbonaceous deposit control.

The repellency a textured surface results from the positive capillary pressure that generates the texture. This pressure helps prevent the droplet enter the texture (e.g., the reliefs) of the surface. For a texture surface a set of raised parts columnar square section having a width dimension "a", "b" and spacer height "h", the capillary pressure can be obtained as:

Equation 1

wherein: P_c = capillary pressure,

y_L v= surface tension of the liquid.

For a surface texture comprised of a set of relief form of cavities having dimensions of radius "a", "b" spacer between pores and height "h", the capillary pressure is given by

=-Pc lv cos0₀ Equation 2

When an immovable object is placed on the surface provided with the reliefs, the capillary pressures above are resistant to what is called the Laplace pressure( Pl = 2j_L v / R, R being the radius of the droplet). If the droplet strikes the surface with a speed V, the capillary pressure associated with the surface must then withstand the pressure Bernoulli {Pb ~ pP/2). Therefore, for stationary droplets, the surface texture must be designed so that Pc > Pl and, for mobile droplets, the surface texture must be designed so that >Pb-Pc

Figure 7 illustrates graphically the theoretical parameters for of the protuberances of the type column on a surface in order to remove droplets striking the surface at different rates. The figure shows the relationship between the column dimension (that is say the width "a") and the relative spacing of the columns (i.e. the ratio b/a of the nip at the width) at varying rates of droplets. The areas located under the curves give the theoretical range of parameters suitable for suppressing a liquid droplet in the given speed. Figure 8 illustrates graphically the theoretical parameters for pores (e.g., cavities) constituting the surface relief, rather than columns. The figure shows the relationship between the radius ("has") of the pores and the speed of the droplets. The area under the curve gives the theoretical parameters suitable for removing the liquid droplet to the given speed.

Figure 9 provides in graphical form a further comparison between the pressures Laplace (P £) the capillary pressures and (Pc)- The dependence capillary pressures and Laplace (measured in Pascals (Pa)) for droplets of 1 microliter (μΕ) has been calculated as a function of the relative surface spacing reliefs as columns (i.e. a ratio b/a of the nip at the width of the columns). Reliefs The dashed line is in the form of columns having a width (a) of 15 micrometers. A a ratio of relative spacing (b/a) of 6 (i.e. with b = 90 micrometers), the pressure P_L , represented by the continuous line, overcoming the pressure P_c . The dashed line represents reliefs in columns (a) having a width of 3 micrometers. As shown in Figure 9, space/width ratios comparable, Pc is always greater than P_L when using the columns of 3 micrometers in width. Therefore, these figures depict in that reliefs carbonaceous deposit control must have as dimensions "has" a width less than about 15 micrometers and a relative spacing (b/a) less than about 6 for that the surface is resistant to wetting.

Instrumenting recall conditions suitable for surface relief carbonaceous deposit control, must be taken into account, by being calculated, the effective fraction of area of the surface on which carbon deposits could adhere. The effective surface area is given by the following equations:

Fraction surface area for columns = 1 / (1+ b/a)² Equation Fraction surface area for pores 3 = 1-π / 4 (1 +b/a)² The Equation 4 equations show that, when columns are sparser (i.e. a ratio width/spacing larger), the effective surface area of contact for carbon deposits is reduced and, therefore, it reduces the risk of adhesion and accumulation. Figures 10 and 11 illustrate graphically the fraction of surface area available for adhesion of deposits carbonaceous, for respective reliefs in the form of columns and reliefs in the form of pores.

By appropriate choice of b/a and and has, associated with a suitable choice of materials after the environment of the application, it is possible to provide a surface texture so that droplets of hydrocarbon fluid on the surface are resistant properties coking occurs associated with a falling behaviour easy droplets. Therefore, the raised lands have a height dimension (h), a width dimension (a) and a spacing dimension (b) such that the ratio b/a is less than about 6 and the ratio h/a is less than about 10.

For reliefs protruding above the surface, e.g. columns (Fig. 10), ordinarily the parameter a is less than approximately 25 micrometers. In some embodiments, a is less than about 10 micrometers. In other embodiments, a is less than about 5 micrometers. In yet other embodiments, a is less than about 1 micrometer. In some embodiments, b/a is from about 0.1 to about 6. In some other embodiments, b/a is from about 0.5 to about 4. In yet other embodiments, b/a is from about 0.5 to about 2. In some embodiments, h/a is less than about 10. In some other embodiments, h/a is less than about 5. In yet other embodiments, h/a is less than about 1.

Also, as shown in Figure 11, for reliefs extending beneath the surface, such as spores, ordinarily the parameter a is less than approximately 25 micrometers. In some embodiments, a is less than about 10 micrometers. In other embodiments, a is less than about 5 micrometers. In yet other embodiments, a is less than about 1 micrometer. In some embodiments, b/a is from about 0.1 to about 6. In some other embodiments, b/a is from about 0.5 to about 4. In yet other embodiments, b/a is from about 0.5 to about 2. In some embodiments, h/a is less than about 10. In some other embodiments, h/a is less than about 5. In yet other embodiments, h/a is less than about 1.

The plurality of reliefs 160 (Figure 5) that make up the texture are not limited necessarily to the surface 120 or an area nearer to the surface 120. In some embodiments, the article 100 further comprises a solid portion 110 disposed under the surface 120, and the plurality of reliefs 160 extend into the solid portion 110. Dividing the reliefs 160 on the entire article 100, including on the surface 120 and in the bulk portion 110, allows for regeneration of the surface 120 when erodes the top layer of the surface.

In some embodiments, the surface comprises a layer of surface energy modification (not shown). In some cases, the modifying layer surface energy is formed by a coating disposed on a substrate. The substrate may be at least one of a metal, an alloy, a ceramic or any combination thereof. The substrate can take the form of a film, sheet, or a bulk form. The substrate may represent the article 100 in its final form, such as a finished part; a shape near net shape; or a blank to be later transformed into the article 100. The surface 120 may be part of the substrate. For example, the surface 120 may be formed directly by reproducing a texture on the substrate or by creating the texture by swaging on the substrate, or by any other method known in the art to form or provide a predetermined surface texture to the surface of a substrate. Alternatively, the surface 120 may be constituted by a layer deposited or disposed on the substrate by any number of techniques known to those skilled in the art.

The coating consists of at least one material selected from the group comprising hard coating oleophobic, a fluorinated material, a composite material and various combinations thereof. An illustrative examples not as-limiting suitable oleophobic coatings diamond like carbon (DLC)

-whose fluorinated DLC, tantalum oxide, titanium carbide, titanium nitride, chromium nitride, boron nitride, chromium carbide, molybdenum carbide, titanium carbonitride, boron nitride, zirconium nitride, the formed nickel electrolessly, silica, titanium oxide and nickel aluminide. At direction of the present disclosure, designated "hard coatings oleophobic" a class of coatings having a hardness greater than that observed for metals and resistance wettability sufficient to generate, with a droplet of oil, a nominal static contact angle of at least about 30 degrees. By way of example in no way limiting, fluorinated DLC coatings have shown a high resistance to wetting by oil. Other hard coatings such as nitrides, borides, carbides and oxides may also perform this function. These hard coatings, and the methods for their application, as the chemical vapor deposit (CVD), the deposition physical vapor deposition (PVD), etc, are known in the art and can be used in aggressive environments. Alternatively, the surface modification layer may be formed by diffusion or implantation of molecular species, atomic or ionic in the surface to form a layer of material having modified surface properties compared to the material in the surface modification layer. In one embodiment, the surface modification layer consists of a material with ion implantation, e.g. a metal ion implantation.

Articles to limited wettability for the oil are advantageous for many applications be subject to problems of thermal deposits such as carbon deposits. An illustrative as examples of potential applications of the embodiments described herein the combustion systems of engines such as gas turbine engines and derivatives on wings of the aircraft, the industrial boilers, furnaces, etc Other examples of articles include, so as not limited to, pipes and tubing for transporting hydrocarbon fluids heated to fuel systems of engines. The nature of the application will determine the extent to which reliefs are to be arranged on an article. Carbonaceous formation causes a degradation of the surfaces on which the risk of deposits and result in impaired performance combustion systems. The properties antifouling carbonaceous articles described herein improve performance and elongate the life of existing systems from the formation of carbonaceous deposits and other problems with deposits thermally induced.

Another aspect of the invention is a method to make unfavourable to the formation of carbonaceous deposits the surface of an article. The method includes: providing an article having a substrate subject to coking occurs; providing a plurality of ridges on the substrate to form a surface such as the formation of carbonaceous deposits on the surface can be reduced. The substrate is made of a material having a nominal wettability by the liquid sufficient to generate, with respect to an oil, a nominal angle of contact. The embossments have dimensions, a shape and orientation selected such that the surface has a effective wettability sufficient to generate, with respect to an oil, a contact angle greater than the nominal angle effective contact. The embossments have a height dimension (h), a width dimension (a), a spacing dimension (b) such that the ratio b/a is less than about 2 and that the ratio h/a is less than about 10. The surface has an angle of effective contact, with respect to an oil, greater than about 30 degrees.

The embossments are arranged on the substrate to form a surface. The embossments may be arranged on the substrate by any texturing process known in the art. An illustrative examples of a few suitable methods as lithography, soft lithography, embossing, forming, etching, the directed growth, the film deposition, laser drilling, sandblasting, thermal spraying, the electrochemical etching and other. The embossments may be made of the same material as the substrate or other material. The choice accurate material of the substrate and features, and the dimensions and spacing of the reliefs is dependent in part on the desired wettability of the surface, as above described. Ordinarily, the surface to the angle of effective contact, with respect to an oil, greater than about 30 degrees. In some embodiments, the surface to the angle of effective contact, with respect to an oil, greater than about 50 degrees. In other embodiments, the surface to the angle of effective contact, with respect to an oil, greater than about 100 degrees.

Embodiments above have advantages over traditional methods of the prior art to limit thermal deposits on the surfaces of parts of gas turbine engines. For example, the parts for a turbine comprising the surfaces herein provide a longer life and superior operation that the existing parts which undergo a thermal deposition. The surfaces antifouling carbonaceous described herein may advantageously prevent the formation of deposits thermal, in particular carbonaceous deposits, without the need for a change in the hydrocarbon fluid, without adoption of special procedures and without installing special equipment may be desired for the existing liquid fuel turbines and the like.

The example below serves to illustrate the elevations and the advantages offered by the embodiments of the present invention is, in no way, and for limiting the invention thereto.

The intervals indicated herein are inclusive and combinable (e.g. intervals of "up to about 25% by weight or, more particularly, from about 5% by weight to about 20% by weight", are Inclusive extreme values and all intermediate values of the intervals of "about 5% by weight to about 25% by weight", etc). The term "combination" includes the amalgams, mixtures, alloys, reaction products and other. Furthermore, the terms "first", "second", and other denote herein does no order, no or importance, but rather are used to distinguish an element of another, and the terms "a" and "a" are not a quantitative limitation herein, but instead indicate the presence of at least one of the above. The adverb change history "about" used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the margin of error associated with measurement of the particular quantity). The suffix "(s)" used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the dye (s) covers one or more dyes). A reference, throughout the description, to "a first embodiment", "another embodiment", "one embodiment", etc means that a particular element (e.g., a relief, a structure and/or characteristic) described with reference to the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. Furthermore, it is understood that the elements described may be combined in any suitable manner in the various embodiments.