CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application claims priority to U.S. Provisional Application No.

62/890,275 filed August 22, 2019, titled “DUCTED COMBUSTION SHIELD”, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

[0002] The present invention relates generally to fuel systems and more specifically to combustion shields for fuel injectors within engines.

BACKGROUND OF THE DISCLOSURE

[0003] Direct-injection engines utilize fuel injectors to inject fuel directly into the combustion chamber. While direct injection engines marked improvements in efficiency and emissions over indirect injection, there remains room for improvement in the technology.

[0004] Presently, diesel engines output a significant amount of soot, which is often removed from exhaust through the use of devices such as diesel particulate filters. Though these filters and other similar methods achieve their purpose of reducing the soot found in the exhaust of a vehicle, they can also be expensive, increase the amount of harmful emissions like NOx and reduce the efficiency of the engine overall.

[0005] Work relating to new methods for reducing emissions and soot output by combustion engines by improving the efficiency of the combustion events in the engine cylinders has been done prior to this invention. Some of these attempts include the use of ducts external to the fuel injector nozzle holes to affect characteristics of the fuel injection. However, previous methods of using ducts rely on structural arms to hold a duct near the injector or add ducts to the cylinder head of the engine. In many cases, these methods require costly engine modification or may lack adequate stability for use in a diesel engine. There remains a need for a fueling system that improves efficiency, reduces emissions, and is easily manufactured and implemented. SUMMARY OF THE INVENTION

[0006] According to an exemplary embodiment, a combustion shield for use with an injector including a nozzle having a plurality of nozzle holes or openings is provided. The combustion shield comprises an outer wall defining a bore, a plurality of ducts, and at least one vent extending through a portion of the outer wall. The bore in the outer wall is sized to receive a portion of the injector nozzle and each duct is substantially or precisely aligned with a portion of the outer wall, receiving a fluid which is emitted through the nozzle hole.

[0007] According to a further exemplary embodiment, the outer wall may extend along a longitudinal axis of the injector beyond the plurality of nozzle holes. Further, each duct may be spaced apart from a corresponding one of the plurality of nozzle holes.

[0008] Further, the outer wall may be constructed from at least two materials. These materials may be selected from a plurality of options and are described in further detail in the following detailed description. For example, a portion of the outer wall is constructed from ceramic, or the plurality of ducts are constructed from a high-erosion resistant material. In some examples, the at least one vent forms a venturi. In some examples, the inlet opening of each duct has a diameter larger than a diameter of each of the nozzle openings. In some examples, each duct has an outlet opening substantially aligned with the one of the plurality of nozzle openings and fluidly coupled with a corresponding one of the inlet openings.

[0009] In some examples, the outlet opening of each duct has a diameter substantially equal to a diameter of the corresponding inlet opening. In some examples, the outlet opening of each duct has a diameter smaller than a diameter of the corresponding inlet opening. In some examples, the outlet opening of each duct has a diameter larger than a diameter of the corresponding inlet opening.

[0010] In some examples, the combustion shield includes a retention feature configured to plastically deform at least a portion of the combustion shield into the injector nozzle and provide mechanical retention. The retention feature may include one or more crimping groove. The combustion shield also has a high thermal conductivity such that it can serve as a heat shield for the injector. [0011] Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The detailed description of drawings particularly refers to the accompanying figures in which:

[0013] FIG. l is a cross-sectional view of a combustion shield according to an illustrative embodiment of the present disclosure; and

[0014] FIG. 2 is a cross-sectional view of a combustion shield according to another illustrative embodiment of the present disclosure.

[0015] FIGs. 3A through 3C are cross-sectional views of a combustion shield according to different illustrative embodiments of the present disclosure.

DETAILED DESCRIPTION

[0016] The embodiments of the invention described herein are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Rather, the embodiments selected for description have been chosen to enable one skilled in the art to practice the invention.

[0017] Referring to FIG. 1, a combustion shield 10 for use with a fuel injector 12 is shown including a plurality of ducts 14 and at least one vent 16.

[0018] Combustion shield 10 also includes an outer wall 18 which defines an internal bore 20. Bore 20 is sized to receive a portion of nozzle 11 of injector 12. Outer wall 18 may be constructed from a plurality of materials as discussed below. It should be noted that shield 10 should be resistant to fluid and cavitation erosion. Further, combustion shield 10 has a high thermal conductivity such that it can serve as a heat shield for injector 12. In some examples, the combustion shield 10 is made of a material with higher thermal conductivity than the material of the injector 12. In some examples, the injector 12 may be made of stainless steel with a thermal conductivity between 14 to 17 Wm^K ¹ . In some examples, steel with 2% tungsten has a thermal conductivity of 17 Wm^K ¹ at 20 °C, and increasing the tungsten content in the steel may decrease the thermal conductivity. In some examples, the material of the combustion shield 10 has a thermal conductivity of at least 50 Wm^K ¹ , at least 70 Wm^K ¹ , at least 80 Wm^K ¹ , at least 100 Wm^K ¹ , at least 120 Wm^K ¹ , or at least 150 Wm^K ¹ at 20 °C and at atmospheric pressure, depending on the material used.

[0019] According to one exemplary embodiment, a lower portion 21 of combustion shield 10 may be made from ceramic. Further, ducts 14 may be made of a high-erosion resistant material, such as tungsten. It should be understood to those skilled in the art that many combinations of different materials could be used in the construction of combustion shield 10 of the present disclosure. Alternatively, combustion shield 10 may also be constructed using only a single material.

[0020] Ducts 14 of combustion shield 10 extend through outer wall 18. Each duct 14 includes an inlet opening 26, an outlet opening 27 and a substantially cylindrical passage 28 that extends along an axis 30 between inlet opening 26 and outlet opening 27. As such, the inlet opening 26 and the outlet opening 27 are fluidly coupled with each other to facilitate fluid communication through the passage 28 and the premixing of the fluid with air coming from the bore 20. Cylindrical passage 28 of each duct 14 is aligned with each injector nozzle hole 22 to receive fuel jets 24 emitted through nozzle holes 22. Fuel jets 24 are directed substantially along axis 30, travel across gap 32 between nozzle holes 22 and inlet openings 26, and enter into inlet openings 26 of ducts 14. Ducts 14 channel fuel jets 24 through passage 28 and out outlet opening 27 into combustion chamber 36. In some examples, the bore 20 is connected to the external environment of the combustion chamber 36. In certain embodiments, a diameter D1 of cylindrical passages 28 is configured to be large enough to allow fuel jets 24 to pass through smoothly. In some examples, the diameter D1 may be larger than a diameter of the nozzle holes 22 to facilitate receiving fuel from the nozzle holes 22 mixed with air from the combustion chamber through the gap 32.

[0021] As shown in FIG. 1, in this embodiment outer wall 18 extends along a longitudinal axis 29 of injector 12 into combustion chamber 36 beyond the plurality of nozzle holes 22. In this manner, inlet openings 26 of each duct 14 are properly aligned with the downward orientation of corresponding nozzle holes 22.

[0022] Still referring to the exemplary embodiment of FIG. 1, ducts 14 are spaced apart from nozzle holes 22 by gap 32 as indicated above. As fuel jets 24 exit nozzle holes 22 and cross gap 32 into an inlet opening 26 of a corresponding duct 14, a local pressure drop occurs. This pressure drop drags air up through open end 34 (or vent 16) of bore 20 to mix with the fuel of fuel jets 24. This amount of air helps determine the pre-mixture of air and fuel used for combustion. Further, the length LI of gap 32 between injector nozzle holes 22 and inlet openings 26 of ducts 14 should be sufficiently small such that fuel jets 24 will not auto-ignite while passing through gap 32. LI may be determined using simulations which account for the specific application and operating conditions.

[0023] In various embodiments, ducts 14 are drilled into wall 18 of combustion shield 10 and may be constructed from a different material than the rest of combustion shield 10. Ducts 14 extend through the thickness (L2) of outer wall 18. Ducts 14 may be visually aligned under a microscope or could include an alignment feature to locate ducts 14 to each corresponding nozzle hole 22. It should be understood that ducts 14 could be formed using various other suitable methods that allow for the alignment of each duct 14 with a corresponding nozzle hole 22

[0024] While only two ducts 14 are shown in the cross-sectional view of FIG. 1, it should be appreciated by those skilled in the art that more or fewer ducts 14 may be used (corresponding to the number of nozzle holes 22) to suit different applications. Additionally, the space between ducts 14 and the size and shape of ducts 14 may be modified for different applications.

[0025] Further, ducts 14 should be sufficiently long to shield against an excessive amount of entrainment. Though some entrainment is required for the operation of the engine, excess entrainment, as seen in engines without ducts, leads to a higher soot output. The shielding from excessive entrainment leads to optimal equivalence ratios at auto-ignition zone of fuel jets 24 at outlet openings 27 of ducts 14, which produces less soot.

[0026] Still referring to FIG. 1, the combustion shield 10 further includes at least one vent 16 as indicated above. Vent 16 allows for air to flow to inlet openings 26 of ducts 14. It should be understood that, rather than including a single vent 16 at the end of outer wall 18 as shown in FIG. 1, combustion shield 10 may include one or more holes that extend through outer wall 18 or one or more holes that extend through a lower wall 35 that extends between outer wall 18 as shown in FIG. 2 and discussed below. In any event, at least one vent 16 should be provided to permit sufficient air flow at gap 32 to inlet openings 26.

[0027] With reference now to FIG. 2, a further exemplary embodiment of a combustion shield 10’ is shown. Components depicted in FIG. 2 that are identical to components of FIG. 1 are identified using identical reference numbers. Combustion shield 10’ differs from combustion shield 10 in at least two ways. First, combustion shield 10’ includes a retention feature 38. Retention feature 38 may be a crimping groove as shown or another similar feature. Retention feature 38 plastically deforms shield 10’ into nozzle 11 to provide mechanical retention. It should be understood that shield 10’ may also be attached with another suitable attachment mechanism such as press fit, welding, or soldiering.

[0028] Still referring to FIG. 2, in the depicted embodiment, combustion shield 10’ encompasses injector nozzle 11, thereby reducing heat transfer from combustion chamber 36 to injector nozzle 11. A small air gap 40 (see FIG. 1) can be established between an inner surface 42 of combustion shield 10’ and an outer surface 44 of the injector nozzle 11 to further reduce heat transfer to injector nozzle 11.

[0029] In the described embodiments, when fuel jet 24 is emitted by fuel injector 11, it is first exposed to air as it passes across gap 32 between nozzle hole 22 and inlet opening 26 of duct 14. As fuel jet 24 passes through this space, air is mixed with the fuel, yielding a lean mix of fuel and air prior to combustion. In some examples, the gap 32 may minimize heat transfer to a tip of the injector nozzle 11. As fuel jet 24 enters duct 14, a pressure drop is created around fuel jet 24 inducing further air flow. The use of a leaner fuel mix leads to lower soot output and may also lead to lower NOx emissions.

[0030] The shielding from excessive entrainment (as detailed above) leads to a lengthening of the distance between the auto-ignition zone at the combustion chamber 36 and injector hole 22, often called the lift-off length by those skilled in the art. This lengthening of the lift-off length contributes to a leaner auto-ignition zone which produces less soot. [0031] Further, it should be understood that once fuel jet 24 exits duct 14, combustion proceeds in the manner known for a combustion engine. Because the flame will bum more cleanly due to a better ratio of fuel and air as discussed above, the engine will output less soot.

[0032] In some examples, as fuel exits the spray hole (nozzle hole 22) in high velocity, the flow of fuel begins to disperse as a function distance from the exit, forming a plume of fuel. The resulting plume enters the passage 28 and creates a low pressure region behind the plume that induces air flow. In some examples, a venturi effect is formed to entrain air in the fluid stream (or fuel jet 24) before it leaves the duct 14, thus allowing the passage 28 to be miniaturized and incorporated into the fuel injector 12. In some examples, a diameter of the plume is 60% to 80% of a diameter of the passage 28 at the entrance section 26. Specifically, when fuel exits the nozzle 11 in high velocity, it locally creates a pressure drop. The pressure drop draws oxygen-rich air into a nozzle chamber (at least partially defined by the inner surface 42 of the combustion shield 10’) from below the injector 12 and entrains the air into the spray plume of the fuel, improving the mixture of fuel and air therein. As such, the vent 16 may be employed as a venturi orifice to introduce air into the nozzle chamber.

[0033] Though described in reference to a diesel engine, it should be understood that combustion shields 10, 10’ of the present disclosure could be used in a variety of engines which could use a variety of fuels. The fuels could include diesel, ethanol, or other appropriate fuels that could be used for compression ignition systems.

[0034] FIGs. 3A through 3C show the different configurations that are possible with respect to the fuel passage 28 for the duct 14 of the combustion shield 10. In FIG. 3A, the passage 28 is substantially cylindrical such that the inlet opening 26 and the outlet opening 27 have similar or same diameter. That is, the diameter Di of the inlet opening 26 and the diameter Do of the outlet opening 27 are substantially the same or equal to each other. This configuration is shown in FIG. 1 where the diameter Dl defines both the diameters Di and D ₀ mentioned herein. That is, the entire passage 28 is defined by a single consistent diameter Dl.

[0035] In FIGs. 3B and 3C, the passage 28 has a frustoconical or tapered configuration, where the two openings have different diameters and the diameter of the duct 14 changes between the openings. For example, FIG. 3B shows the inlet opening 26 with the diameter Di being smaller than the diameter D ₀ of the outlet opening 27, and FIG. 3C shows the inlet opening 26 with the diameter Di being larger than the diameter D ₀ of the outlet opening 27. In some situations, the difference in the diameters may be advantageous in controlling the fuel flow through the passage 28, as well as to allow for greater flexibility in positioning the shield 10 with respect to the injector 12.

[0036] Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the spirit and scope of the invention as described and defined in the following claims.