FIELD OF THE DISCLOSURE

[001] The present disclosure is related to reducing fuel-film formed on the surface of intake port or valve during cold start and/or warm-up phase of an internal combustion engine, and more particularly to improved homogenization of an air/fuel mixture prior to combustion in an internal combustion engine.

BACKGROUND OF THE DISCLOSURE

[002] In port fuel injected (PFI) engines fuel delivery is typically performed outside the cylinder in an attempt to obtain a fairly homogeneous charge, which is desired for improving full combustion. In these engines the fuel spray is injected from a fuel injector towards an inner wall of an inlet duct of the cylinder head, which may result in fuel accumulation on the inner wall. This effect may be particularly prevalent due to condensation where the engine is not yet warmed to operating temperature.

[003] Fuel mixture preparation may occur by fuel evaporation from the fuel accumulated on the inner wall, and suspended droplets that are introduced during each injection cycle.

[004] One of the challenges facing PFI engines is the completion of mixture preparation at cold start and/or warm-up phase when the temperatures of intake duct walls and inlet valves are low. During these "cold start" periods, available time for complete fuel evaporation is short and the level of turbulence in the flow is low. These problems may result in imprecise fuel metering due to reduction of amount of fuel induced in the cylinder compared to that of injected; incomplete combustion and high peak of unburned hydrocarbons and carbon monoxide due to inlet port and valve surface wetting; and incomplete in-cylinder droplet evaporation, among others.

[005] DE 2306362 discloses a two-dimensional mesh or net layer positioned downstream (i.e., in front of) of a fuel injector in the intake port.

The mesh is intended to facilitate cold start conditions and engine operation by improving initial fuel vaporization and reducing wall film formation in the intake port and on the valve surfaces. However, this net has a limited number of pores which are incapable of dispersing the fuel in a wide pattern within intake port. Therefore, in spite of some level of additional air/fuel mixture

homogenization the degree of homogenization may not be sufficiently enhanced to achieve full combustion and eliminate the drawbacks discussed above.

SUMMARY OF THE DISCLOSURE

[006] The present inventors have recognized that in DE 2306362 incomplete homogenization remains a problem, particularly at low temperature and during engine warm-up. Therefore improvements in air/fuel

homogenization are desirable, for example, improved dispersion of a fuel rich core emanating from a fuel injector.

[007] According to embodiments of the present disclosure, a fuel injected combustion engine is provided. The engine comprises an intake port in controllable fluid communication with a cylinder of the fuel injected combustion engine, fuel delivery means in fluid communication with the intake port and positioned to facilitate provision of fuel into the intake port, and a first three- dimensional porous medium positioned between the cylinder and the fuel delivery means, and configured to disperse fuel provided by the fuel delivery means via a plurality of pores in the porous medium.

[008] By providing such a system, homogenization of an air/fuel mixture may be improved due to dispersion of the fuel through a three-dimensional porous medium. In causing an "injected" fuel spray to pass through a three- dimensional porous medium, a fuel rich "core" of the injected spray may be more thoroughly dispersed upon traversing a thickness of the medium, and thereby, more readily combined with intake air.

[009] Importantly, the term "three-dimensional," as used herein, shall be understood to mean a medium that, in addition to presenting a surface area, has an observable thickness, for example greater than 2 mm, and more specifically, between 5 and 10mm.

[0010] A second three-dimensional porous medium positioned between the first three-dimensional porous medium and the cylinder may also be provided. The second three-dimensional porous medium may have a pore density different than that of the first three-dimensional porous medium. [0011] According to some embodiments, the first three-dimensional porous medium may have a pore density less than that of the second three- dimensional porous medium.

[0012] The first three dimensional porous medium may have a pore density between 8 and 10 PPI, and for example, a porosity greater than 80 percent.

[0013] The second three-dimensional porous medium may have a pore density of greater than 20 PPI, and for example, a porosity greater than 80 percent.

[0014] A heating means may be provided, and configured to increase a temperature of the first and/or second three-dimensional porous medium.

[0015] The heating means may include a glow plug inserted at least partially into one of the first or second three-dimensional porous medium and/or an electric heater (e.g., a resistance heater) in contact with at least a portion of an outer surface of the first and/or second three-dimensional porous medium.

[0016] The three-dimensional porous medium may comprise a porous ceramic foam, for example, a silicon carbide (SiC).

[0017] The three-dimensional porous medium may comprise a porous metallic foam, for example, Cu (copper).

[0018] A passage distinct from the intake port may be provided, and may fluidly connect an upstream portion of the first three-dimensional porous medium, i.e., a portion positioned between the fuel delivery means and the first three-dimensional porous medium, with an air flow. The air flow may comprises air from an upstream portion of the intake port, and/or ambient air surrounding an external portion of the fuel delivery means.

[0019] According to some embodiments, the first and/or second three- dimensional porous mediums may be shaped to conform with an internal shape of the intake port. For example, the shape may be generally circular or oval.

[0020] Further, a thickness of the first three-dimensional porous medium may be between 10 and 15 mm, while a thickness of the second three- dimensional porous medium, when provided, may be between about 5 and 10 mm. Where additional three-dimensional media are provided, the thicknesses thereof may decrease for each additional media.

[0021] According to further embodiments of the present disclosure, a vehicle comprising a fuel injected combustion engine according to any of the embodiments discussed above may be provided. [0022] According to still further embodiments, a method for homogenizing an air/fuel mixture of a fuel injected combustion engine is provided. The method includes injecting fuel provided by a fuel delivery means through a first three-dimensional porous medium.

[0023] By providing such a method, better homogenization of an air/fuel mixture may be obtained based on passage of a fuel spray through the three- dimensional porous medium.

[0024] The method may include causing the injected fuel to pass through a second three-dimensional porous medium positioned between the first three- dimensional porous medium and a cylinder of the combustion engine.

[0025] The method may include heating the first and/or second three- dimensional porous medium.

[0026] Heating of the three-dimensional porous medium may further improve evaporation of fuel and homogenization of the air/fuel mixture, thereby leading to improved combustion, especially at cold-start.

[0027] It is intended that combinations of the above-described elements and those within the specification may be made, except where otherwise contradictory.

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description, and serve to explain the principles thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 shows a cross section of one cylinder of an exemplary porous material assisted PFI spark-ignition internal combustion engine according to embodiments of the present disclosure;

[0030] Fig. 2 shows a cross-sectional view highlighting an exemplary heating configuration according to embodiments of the present disclosure;

[0031] Fig. 3 shows a cross-sectional view highlighting another exemplary heating configuration according to embodiments of the present disclosure;

[0032] Fig. 4 shows exemplary three-dimensional porous media according to embodiments of the present disclosure; and [0033] Fig. 5 shows a flowchart highlighting an exemplary method for homogenization of an air/fuel mixture according to embodiments of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

[0034] Reference will now be made in detail to exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0035] Figure 1 shows a cross section of one cylinder of an exemplary porous material assisted PFI spark-ignition internal combustion engine according to embodiments of the present disclosure. One of skill understands that while a single cylinder is shown and discussed for purposes of explanation, the porous material assisted PFI spark-ignition internal combustion engine may comprise as many cylinders as desired, each having a similar configuration to that described herein.

[0036] The combustion engine includes at least one intake valve 2 downstream of an intake port 1, an injection port 8, at least one piston 12, and block 13. The engine includes at least one controlled (e.g., electronically via an ECU) fuel injector 9. Fuel injector 9, corresponding to a fuel delivery means, may be affixed to injection port 8 (e.g., via fasteners 11) and configured to inject fuel into the cylinder formed in block 13 in which piston 12 reciprocates such that the air/fuel mixture may be subsequently ignited (e.g. via a spark) within the cylinder. General operation of a combustion engine is well understood by one of skill in the art and will not be discussed in detail herein.

[0037] Injection port 8 may be configured to receive an electronically controlled fuel injector 9, and may be in fluid communication with intake port 1. Injection port 8 may have any suitable shape and size (e.g., circular or semi circular), for example, depending on a design of the engine in which injection port 8 is intended to operate.

[0038] Fuel injector 9 may be positioned within injection port 8 and be configured to inject any type of fuel suitable for combustion in the PFI combustion engine, e.g., gasoline, ethanol, methanol, etc. Particularly, fuel injector 9 may be configured to provide fuel to intake port 1 and entrained by an airflow carried by intake port 1 into the cylinder upon opening of valve 2 at a particular timing.

[0039] At least one three-dimensional porous medium 4, 6 configured to disperse the fuel provided by fuel injector 9 is positioned between fuel injector 9 and the cylinder into which the air/fuel mixture is to be injected. For example, at least one three-dimensional porous medium 4, 6 may be provided in between injection port 8 and intake port 1.

[0040] According to some embodiments, and as shown in the figures, two such three-dimensional porous medium 4, 6 may be provided, and one of skill in the art understands that three, four, or more porous media 4,6 are also contemplated and considered to fall within the scope of the present disclosure.

[0041] Three-dimensional porous medium 4, 6 comprise a porous material, i.e., a material comprising a plurality of pores permitting fluids to pass through from an impingement side 35 of the medium to an exit side 36 of the media, by traversing various pores 40 present within the porous medium 4, 6. The three- dimensional media may comprise, for example, a metal or ceramic foam.

[0042] According to some embodiments, a porosity of the three-dimensional porous medium 4, 6 may be greater than 70 percent, greater than 80 percent, and in some embodiments, greater than 90 percent. In any case, the porosity of the three-dimensional porous medium is less than 100 percent.

[0043] Three-dimensional porous medium 4, 6 may be fabricated from a ceramic foam, for example, of high thermal conductivity, such as, for example, a silicon carbide (SiC) or Aluminum oxide (AI2O3) Alternatively, or in addition, three-dimensional porous medium 4, 6 may be fabricated from a metal foam, such as, for example, copper (Cu) or Aluminum (Al) or nickel-chromium- aluminum (Ni-Cr-AI).

[0044] Three-dimensional porous medium 4, 6 may have a thickness Ti, T ₂ and where circular, or substantially circular in form, a radius R. According to some embodiments, three-dimensional porous medium 4, 6 may be shaped so as to substantially conform to an internal periphery of injection port 8 in fluid communication with intake port 1 of the cylinder into which the air/fuel mixture 3 is to be provided. Such a shape may be, for example, circular, oval, etc. One of skill will understand that where a polygonal shape is implemented, the discussion of radius is intended to refer to dimensions enabling the calculation of a surface area and volume of such a polygon, e.g., for a rectangle, length and width along with thickness Ti, T ₂ .

[0045] Where two or more three-dimensional porous medium 4, 6 are provided, the porosity, pore density, composition, and thickness may be identical among all of the three-dimensional porous medium 4, 6. For example, where two porous media 4, 6 are provided, each may be fabricated of a ceramic foam having a thickness of 10mm, with a porosity of greater than 80 percent, and a pore density of approximately 8-10 PPI.

[0046] Alternatively, and according to a desirable implementation, the characteristics of each provided three-dimensional porous medium 4, 6 may differ in one or more of porosity, pore density, composition, and thickness. For example, where two porous media 4, 6 are provided, a first medium 6 may comprise a ceramic foam having a porosity of greater than 80 percent and a pore density of 8-10 PPI. A thickness Ti of the first porous medium may be approximately 6-15 mm, for example, and more specifically between 10 and 15mm.

[0047] A second medium 4 may again comprise a ceramic foam having a porosity of greater than 80 percent, but a higher pore density of, for example, greater than 20 PPI and a lesser thickness T ₂ , for example, 5-10 mm.

[0048] Alternatively, the second medium 4 may also differ in composition, for example a metal foam instead of a ceramic foam. Various combinations of first and second three-dimensional porous media are contemplated and intended to fall within the scope of the disclosure, for example, combinations of ceramic and metal.

[0049] In such an implementation, first medium 6 and second medium 4 may be placed such that each contacts a respective surface of the other. In other words, a distance d, as highlighted at Fig. 4, may be approximately 0mm. Alternatively, distance d between an exit surface of a first three-dimensional porous medium 6 and an impingement surface of a second three-dimensional porous medium 4, may vary between approximately 0.5 and 5mm, as desired, and more specifically, between 0.5 and 1mm.

[0050] A distance D _s between an injection tip 10 of fuel injector 9 and a first surface of three-dimensional porous medium 6 may be adjusted to improve fuel distribution over the impingement surface of medium 6. Such a distance may be adjusted to reduce the amount reflected spray from the surface of the porous medium after spray impingement. For example, a tip of the injector may be placed as closed as the top surface of the medium depending on the injection pressure and pore density of the porous medium. The distance between the tip of injector and the surface of the medium can be between zero and approximately the thickness of the medium for example. According to some embodiments the distance D _s may range between 0 mm and 15mm.

[0051] Figs. 2 and 3 show cross-sectional views highlighting exemplary heating configurations according to embodiments of the present disclosure. As shown at Fig. 2, a heating element 25 may be provided, for example, surrounding the one or more three-dimensional porous medium 4, 6. According to some embodiments, heating element 25 may be in contact with at least one three-dimension porous medium 4, 6, such that upon providing power (e.g., an electric current) to heating element 25, a temperature of the at least one three- dimensional medium 4, 6 is increased.

[0052] Such a heating element 25 may be an electrical resistance heating element, for example, comprising a coil of wire having a relatively low

resistance so as to increase in temperature when current is passed through the coil.

[0053] As shown at Fig. 3, a glow plug 5 may be provided, such glow plug 5 being inserted into a portion of the at least one three dimensional porous medium 4, 6. Glow plug 5 may be similarly configured to, upon receiving a flow of current, increase the temperature of the one or more three dimensional porous medium 4, 6 before the start of an injection process where fuel is injected from fuel injector 9.

[0054] Such a temperature increase may be configured to facilitate evaporation of the fuel during, for example, a cold start condition. For example, a temperature of between 50 and 100 degrees C may be obtained by the at least one three-dimensional porous medium 4, 6 depending on the level of energy provided to glow plug 5 and/or heating element 25. For example, the temperature may be near a boiling temperature of the fuel with the goal of causing approximately 50 per cent of fuel to be evaporated. Where gasoline is chosen as the fuel the temperature may be approximately 101°C. Notably, glow plug 5 and heating element 25 may be provided in tandem to provide an extra boost of heating when necessary. [0055] Fig. 5 shows a flowchart 500 highlighting steps by which an air/fuel mixture may be better homogenized. By heating the one or more three- dimensional porous medium 4, 6 (step 505) and then causing fuel injected from fuel injector 9 to pass through one or more three-dimensional porous medium 4, 6 (step 510), the fuel spray may become better distributed and evaporated, and a fuel rich "core" normally present during a fuel injection process may be eliminated.

[0056] In addition, it may be possible to better entrain fuel spray 3 with intake air flow within port 1 to create a more homogenous combustible mixture which flows inside the cylinder when during opening of intake valve 2. These effects may significantly reduce the chance of wall film formation of fuel in the intake port 1, especially at cold start.

[0057] Variations and additions may be made to the disclosed system without departing from the scope of the disclosure. For example, in order to improve cleaning/clearing of the pores 40 in the one or more three-dimensional porous medium 4, 6 from possibly accumulated fuel droplets or other substances, a passage 14, distinct from the intake port 1, but providing fluid communication between intake port 1 and the space created in injection port 8 by distance D _s , may be provided. By providing passage 14, a portion of air, for example, turbocharged air at an increased pressure, may be provided to an impingement surface 35 of the first three-dimensional porous medium 6, and caused to pass there through, clearing and/or cleaning the pores 40 of the medium.

[0058] An arrangement is also contemplated whereby passage 14 passes through an upper portion of fuel injector 9 (e.g., via a mounting flange) such that ambient air (i.e., uncharged air) is provided to the impingement surface 35 of the first three-dimensional porous medium.

[0059] Notably, portions of the injection port 1 and fuel injector 9 may be caused to hold the one or more porous media 4, 6 in place.

[0060] Sealing has been also considered between fuel injection port 8 and fuel injector 9, as well as a seal 7 between a top edge of the impingement surface 35 of the first three-dimensional porous medium 6, and the fuel injection port 8. Additionally a seal 7' between a bottom side 36 of the porous medium 4, 6 (i.e., where the dispersed fuel exits the medium) is considered. These seals 7, 7' may be configured to hold the media in place and, for example, to aid in installation by avoiding fracturing of the media.

[0061] Application of EGR and subsequent cleaning the porous media is also considered in the scope of the present disclosure. Passage 14 bringing gas from intake port may also be connected to an EGR pipe in the intake system. This may increase a possibility of clogging of the porous structure by particulate matters coming from an EGR stream. Therefore, it may be possible to introduce a sudden high pressure airflow through porous medium so these particles can be flushed.

[0062] The features of the invention will appear more fully from the accompanying drawings following the above mentioned descriptions.

[0063] Throughout the description, including the claims, the term

"comprising a" should be understood as being synonymous with "comprising at least one" unless otherwise stated. In addition, any range set forth in the description, including the claims should be understood as including its end value(s) unless otherwise stated. Specific values for described elements should be understood to be within accepted manufacturing or industry tolerances known to one of skill in the art, and any use of the terms "substantially" and/or "approximately" and/or "generally" should be understood to mean falling within such accepted tolerances.

[0064] Although the present disclosure herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure.

[0065] It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.