The invention relates to gasoline direct injection for vehicles and, more particularly, to providing a non-thermally conducting coating on a fuel injector tip to increase a temperature thereof and thus reduce particulate emissions.
Particulate emissions of gasoline engines will be newly regulated in Europe in 2014 with the introduction of EU6a regulations of 6×1012 particles/km and further reduced to 6×1011 particles/km with the introduction of EU6c in 2017. Similarly, United States regulations will impose similarly challenging standards with the introduction of LEVIII. Standards are assumed to be 10 mg/mi in 2014, 3 mg/mi in 2018 and 1 mg/mi in 2025. A major source of particulate emissions is known to be from a diffusion flame fed by fuel evaporating from the deposits on the fuel injector tip.
It is known that protruding the fuel injector further into the combustion chamber reduces the particulate emissions. Increasing injector tip protrusion raises injector tip temperature by exposing more injector tip surface area to hot combustion gases. This in turn enhances evaporation of any fuel remaining on the tip so there is no or little fuel remaining on the tip to be ignited when the flame front passes. The higher tip temperature also enhances oxidation of the deposits on the tip reducing the sponge-like surface of the deposits which hold the fuel.
Increasing tip temperature enhances evaporation on the external surfaces of the tip lowering particulate emissions, but it also increases the temperature of the fuel metering orifices or passages. This increases the risk of deposits being formed in the metering passages themselves. It is well known that fuel characteristics, tip (orifice) temperatures, fuel pressure and nozzle design affect deposit formation in injector flow passages. It is generally accepted that if the tip temperatures are kept below 120° C., that no problems with deposit related flow shift will be encountered. This guideline is only achievable with side mounted direct injectors. In centrally mounted injector applications, temperatures up to 300° C. can be seen.
Thus, there is a need to increase the injector tip temperature to lower particulate emissions while allowing the metering passages of the injector to be cooled by the fuel to prevent deposit formation in the passagers and thus prevent flow shift.
An object of the invention is to fulfill the need referred to above. In accordance with the principles of the embodiments, this objective is obtained by providing a fuel injector having an inlet, an outlet, and a passageway providing a fuel flow conduit from the inlet to the outlet. The fuel injector includes a valve structure movable in the passageway between a first position and a second position. A seat, at the outlet, has at least one seat passage in communication with the passageway. The seat contiguously engages a portion of the valve structure in the first position thereby closing the at least one seat passage and preventing fuel from exiting the at least one passage. The valve structure in the second position is spaced from the at least one seat passage so that fuel can move through the passageway and exit through the at least one seat passage. The seat includes an outer tip surface through which the least one seat passage extends. A non-thermally conducting coating is provided on at least a portion of the outer tip surface and not on surfaces defining the at least one seat passage. The coating is constructed and arranged to be heated by combustion gases so that the outer tip surface reaches a temperature greater than a temperature that the outer tip surface would reach if the coating was not provided, so as to cause evaporation of fuel that contacts the outer tip surface after injection. The at least one seat passage is constructed and arranged to not be substantially heated by conduction from the outer tip surface and to be cooled by fuel passing there-through so as to prevent deposits of combustion from accumulating on surfaces defining the at least one seat passage.
In accordance with another aspect of a disclosed embodiment, a method reduces particulate emissions associated with a fuel injector. The fuel injector has an inlet; an outlet; a passageway providing a fuel flow conduit from the inlet to the outlet; a valve structure movable in the passageway between a first position and a second position; a seat, at the outlet, having at least one seat passage in communication with the passageway. The seat contiguously engages a portion of the valve structure in the first position thereby closing the at least one seat passage and preventing fuel from exiting the at least one passage. The valve structure in the second position is spaced from the at least one seat passage so that fuel can move through the passageway and exit through the at least one seat passage. The seat includes an outer tip surface through which the at least one seat passage extends. The method coats a non-thermally conducting material on at least a portion of the outer tip surface and not on surfaces defining the at least one seat passage. The coating is heated by combustion gases during operation of the fuel injector so that the outer tip surface reaches a temperature greater than a temperature that the outer tip surface would reach if the coating was not provided, thereby enhancing evaporation of fuel on the outer tip surface and thus reducing particle emission. The method cools surfaces defining the at least one seat passage with fuel passing there-through so that the surfaces are at a temperature less than a temperature of the outer tip surface to ensure that fuel remaining in the at least one passage after injection is in a liquid state, thereby preventing deposits of combustion from accumulating on surfaces defining the at least one seat passage.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.
The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:
With reference to
Movement of the ball valve 24 opens or closes, respectively, the at least one metering orifice or seat passage 28 (
In accordance with an embodiment, an insulative coating 32 is provided on at least a portion of the outer tip surface 30. The coating 32 permits the surface temperature of the tip surface 30 to increase and, at the same time, allows the seat passages 28 to be cooled more effectively by the fuel passing there-through. The hot tip surface 30 reduces particle emissions and the cool seat passages 28 minimize the risk of deposit related flow loss. In the embodiment, the coating 32 surrounds, without obstructing, all of the seat passages 28.
It has been shown through measurements and modeling that the flow of fuel through the seat 26 has a major influence on the temperatures encountered on the seat 26. The plot shown in
In the embodiment, the steel outer tip surface 30 is coated with a non-thermally conducting material 32. The passages 28 are drilled through the more thermally conductive steel portion of the seat 26. The outer tip surface 30 is coated in such a way to allow the fuel to exit the steel surfaces defining the passages 28 with minimal contact with the coated tip surface 30. In this way, the passages 28 are cooled and wetted with fuel during injection but are not substantially heated through conduction from the large surface area of the tip surface 30 exposed to the heat of combustion. The low temperature (lower than that of the outer tip surface) in the passages 28 allows what fuel remains there after injection to remain liquid and not form deposit precursors. The coated tip surface 30, being insulated, is readily heated by the combustion gases and reaches higher temperatures than the same geometry would reach if it was not coated. Any fuel that contacts this hot surface readily evaporates and is less likely to form deposits and/or a diffusion flame creating particulates.
The material of the coating 32 preferably falls into the class of materials known as thermal barrier coatings. These are typically ceramic coating systems most commonly containing yttria-stabilized zirconia or other rare earth zirconates. However, the coating is not limited to zirconia or zirconates. The thickness of the coating 32 depends on the material selection and application method. A target thickness is preferably less than 0.25 mm.
Thus, the embodiments ensure that the temperature of the tip surface 30 is maintained as high as possible to lower particle emission and ensure that the temperature of the surfaces of the passages 28 is as low as possible so as to limit fuel deposits forming in the passages and thus prevent flow shift that is caused by fuel deposits.
The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.
Number | Name | Date | Kind |
---|---|---|---|
4817873 | McKay | Apr 1989 | A |
5173339 | Singer | Dec 1992 | A |
5551638 | Caley | Sep 1996 | A |
6267307 | Pontoppidan | Jul 2001 | B1 |
6502769 | Imoehl | Jan 2003 | B2 |
6755024 | Mao et al. | Jun 2004 | B1 |
6845920 | Sato et al. | Jan 2005 | B2 |
7051961 | Mills | May 2006 | B2 |
7896262 | Suzuki et al. | Mar 2011 | B2 |
20050242212 | Chapaton et al. | Nov 2005 | A1 |
20090025680 | Kihara | Jan 2009 | A1 |
20100224706 | Suzuki et al. | Sep 2010 | A1 |
20110147493 | Mitsuoka et al. | Jun 2011 | A1 |
20130048748 | Imoehl | Feb 2013 | A1 |
Number | Date | Country |
---|---|---|
1076998 | Oct 1993 | CN |
101338717 | Jan 2009 | CN |
Entry |
---|
Masao Kinoshita et al., A Method for Suppressing Formation of Deposits on Fuel Injector for Direct Injection Gasoline Engine, Society of Automotive Engineers, Inc., vol. 1999-01-03656, 1999, pp. 25-32. |
Wikipedia contributors, “Thermal barrier coating”, Wikipedia, The Free Encyclopedia, Feb. 25, 2014, 10:22 UTC, https://en.wikipedia.org/w/index.php?title=Thermal—barrier—coating&oldid=597050781 (accessed Jun. 26, 2014). |
Chinese Office Action and English translation dated Mar. 27, 2017, for counterpart Chinese application No. 201510617599.8. |
Chinese Decision on Rejection, dated Aug. 29. 2017 for corresponding Chinese Application No. 201510617599.8. |
Number | Date | Country | |
---|---|---|---|
20150377198 A1 | Dec 2015 | US |