Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M45/00—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship
  • F02M45/02—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts
  • F02M45/04—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts with a small initial part, e.g. initial part for partial load and initial and main part for full load
  • F02M45/08—Injectors peculiar thereto
  • F02M45/086—Having more than one injection-valve controlling discharge orifices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
  • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
  • F02M61/18—Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for
  • F02M61/1806—Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for characterised by the arrangement of discharge orifices, e.g. orientation or size
  • F02M61/1813—Discharge orifices having different orientations with respect to valve member direction of movement, e.g. orientations being such that fuel jets emerging from discharge orifices collide with each other
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
  • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
  • F02M61/18—Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for
  • F02M61/1806—Injection nozzles, e.g. having valve seats; Details of valve member seated ends, not otherwise provided for characterised by the arrangement of discharge orifices, e.g. orientation or size
  • F02M61/182—Discharge orifices being situated in different transversal planes with respect to valve member direction of movement
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
  • F02M2200/46—Valves, e.g. injectors, with concentric valve bodies

Definitions

• the present invention relates to a fuel injector mountable with respect to a combustion chamber for delivering fuel thereto, and to a fuel injection system for an internal combustion engine comprising such an injector.
• Fuel injectors are used to deliver fuel under high pressure to a combustion space of an engine. It is known to use multi-hole fuel injection nozzles in internal combustion engines, such as diesel engines with direct injection diesel combustion systems.
• One such multi-hole fuel injection nozzle is disclosed in European Patent No. 1626173 and comprises a nozzle body having concentric valve needles to control the flow of fuel through respective upper and lower spray holes.
• European Patent No. 1059437 describes a multi-hole injection nozzle which provides improved optimisation of air/fuel mixing.
• Figure 1 shows an injection nozzle of the kind described in EP- 1059437.
• the injection nozzle comprises a nozzle body 1 having a blind bore 2.
• the nozzle body 1 defines a primary nozzle axis A-A which is co-axial with the blind bore 2.
• the blind end of the bore 2 is provided with upper and lower spray holes 3, 4 and defines a seating with which a valve needle (not shown) is engageable to control the supply of fuel to the upper and lower spray holes 3, 4.
• the valve needle may be of the type described in EP-1626173, where inner and outer concentric valve needles are provided to control the flow of fuel through both the upper and lower spray holes together or through the upper spray hole only.
• first and second fuel sprays are emitted having axes labelled 7 and 8, respectively.
• the first and second fuel sprays 7, 8 merge to form a single fuel spray jet which gives the effect of a single large spray hole in terms of fuel mass flow and penetration of the fuel spray jet.
• the intersection point 6 of the first and second fuel sprays 7, 8 lies a distance RC into the combustion chamber, in a direction perpendicular to the primary nozzle axis A-A.
• the line 9 defines the axis and direction of the merged fuel spray jet.
• the vertical distance X3 below the flame face 10 of the engine cylinder head (i.e. at the ceiling of the combustion chamber) at the radius RC from the centre of the combustion chamber gives a vertical target direction of the merged fuel jet.
• the vertical target of the merged fuel spray jet 9 corresponds to the distance X3 below the flame face 10 of the engine cylinder head at the radius RC from the centre of the combustion chamber.
• the vertical target of the fuel spray jet from the single spray hole also corresponds to the distance X3 below the flame face 10 at the radius RC from the centre of the combustion chamber.
• the vertical target of the fuel spray jet from the single spray hole also corresponds to the distance X3 below the flame face 10 at the radius RC from the centre of the combustion chamber.
• the vertical target distance of the resulting fuel spray jet is the same. This is problematic for obtaining the lowest possible soot emissions because the vertical target distance which is optimal for air/fuel mixing is known to vary as a function of the engine speed/load.
• a fuel injector mountable with respect to a combustion chamber for delivering fuel thereto, the combustion chamber comprising a chamber ceiling and a chamber wall, the fuel injector comprising: a nozzle body having a primary nozzle axis; a first outlet opening having a first axis; a second outlet opening having a second axis; and means for controlling fuel delivery through the first and second outlet openings, said means comprising an inner valve needle and an outer valve needle, and being arranged to permit fuel delivery from only the first outlet opening, or through both the first and second outlet openings together; wherein the first and second outlet openings are oriented such that, in use, when fuel delivery is permitted through only said first outlet opening, a first spray formation is injected along the first axis, the first spray formation reaching a first target distance below said chamber ceiling at a radial distance from the primary nozzle axis; and when fuel delivery is permitted through both openings together, respective first and second spray formations are injected along the respective first
• the present invention provides a fuel injector which can give a different vertical fuel jet target at high engine loads and speeds compared with low engine loads and speeds and which can provide the combined benefit of varying the effective target direction with a variable effective spray hole diameter for the fuel spray jets.
• a different vertical spray/jet target By providing a different vertical spray/jet target, a better optimization of the vertical distribution of the fuel in the combustion chamber can be obtained, while the variable effective spray hole diameter gives a better optimization of the fuel distribution in the radial direction in the combustion chamber as engine load and speed conditions are varied.
• the resulting first spray formation reaches the first target distance below the chamber ceiling, which may be the optimum target distance for minimising emissions at the low engine load/speed condition.
• the second target distance is larger than the first target distance and may be the optimum target distance for minimising emissions at a high engine load/speed condition, when fuel delivery is permitted through both first and second outlet openings.
• the delivery of fuel through the first and second outlet openings is conveniently controlled by inner and outer valve needles.
• the nozzle body comprises a blind bore, and the first and second outlet openings open into the blind bore at respective locations spaced apart in the direction of the primary nozzle axis.
• the blind bore defines a seating with which each of the inner and outer valve needles is engageable.
• the second outlet opening may conveniently be disposed between the first outlet opening and the blind end of the bore.
• said outer valve needle is slidable within the bore to control fuel delivery through the first outlet opening and said inner valve needle is slidable within a further bore formed in the outer valve needle to control fuel delivery through the second outlet opening.
• the fuel injector comprises load transmitting means to permit the outer valve needle to transmit a force to the inner valve needle so as to cause movement of the inner valve needle when the outer valve needle is moved beyond a predetermined amount.
• the first outlet opening may be disposed between the second outlet opening and the blind end of the bore.
• said first and second axes may intersect at an intersection point which lies between the fuel injector and the chamber wall.
• said outer valve needle is slidable within the bore to control fuel delivery through the second outlet opening and said inner valve needle is slidable within a further bore formed in the outer valve needle to control fuel delivery through the first outlet opening.
• the fuel injector comprises load transmitting means to permit the inner valve needle to transmit a force to the outer valve needle so as to cause movement of the outer valve needle when the inner valve needle is moved beyond a predetermined amount.
• the fuel injector comprises one or more additional adjacent pairs of first and second outlet openings. More preferably, each of said adjacent pairs of first and second outlet openings are radially spaced at regular intervals around the primary nozzle axis.
• said radial distance is substantially equal to the radius of the combustion chamber.
• said first outlet opening and said second outlet opening have substantially the same diameter.
• a fuel injection system for an internal combustion engine comprising a combustion chamber having a chamber ceiling and a chamber wall, and a fuel injector according to the first aspect for delivering fuel to the combustion chamber.
• first aspect of the invention may be incorporated within the fuel injector of the second aspect, alone or in appropriate combination.
• Figure 1 is a schematic diagram of a conventional fuel injection nozzle.
• Figure 2A is a graph showing the relationship between engine soot emissions and fuel spray jet target distance under high engine load and speed conditions
• Figure 2B is a graph showing the relationship between engine soot emissions and fuel spray jet target distance under low engine load and speed conditions
• Figure 3 shows a first embodiment of an injection nozzle according to the present invention.
• Figure 4 shows a second embodiment of an injection nozzle according to the present invention. Detailed Description of Preferred Embodiments
• a combustion chamber of an internal combustion chamber is typically defined within an engine cylinder.
• a piston is mounted for reciprocable movement within the engine cylinder and comprises a piston bowl formed in an upper surface thereof.
• the ceiling of the combustion chamber is defined by a cylinder head face, which is also known in the art as a flame face.
• the injection nozzle of a fuel injector When installed within the engine, the injection nozzle of a fuel injector extends through an opening formed within the chamber ceiling.
• the wall of the combustion chamber which the fuel spray jet from the injection nozzle is incident upon is defined by the surface of the piston bowl of the piston.
• injection occurs when the piston is positioned at top dead centre (TDC) as is known in the art.
• spray jet or spray formation used hereinbelow will be understood to refer to the fuel injected through the fuel injection nozzle regardless of whether it is in vapour or liquid form, or a combination of both vapour and liquid.
• soot emission from a diesel engine is sensitive to the vertical target of the fuel spray/jet on the wall of the combustion chamber in the piston bowl. Furthermore, engine emission test work shows that there is an optimum vertical distribution for injection of fuel into the combustion chamber for the best fuel/air mixing and, accordingly, the lowest soot or smoke emission.
• Figures 2A and 2B comprise two curves C1 , C2 of exhaust smoke levels on the vertical axis plotted versus a fuel spray jet target distance on the horizontal axis.
• the fuel spray jet target distance is the vertical distance X below the cylinder head face at a radius RC from the primary nozzle axis A-A in Figure 1 , such as the value X3.
• the curve C1 in Figure 2A corresponds to a high engine load and high speed operating condition. It is apparent from curve C1 that the lowest smoke emission level S3 is achieved with a fuel spray jet target distance X1 below the cylinder head face or flame face.
• the curve C2 in Figure 2B corresponds to a low engine load and low speed operating condition. It is apparent from curve C2 that the lowest smoke emission level S4 is achieved with a fuel spray jet target distance X2 below the cylinder head face.
• soot emission could be reduced with a lower spray jet target in the combustion chamber (higher value of X) at high engine loads and speeds. Conversely, at low loads and speeds the soot emission level could be reduced with a higher fuel spray jet target (lower value of X).
• the upper and lower edges of the fuel spray jet from the upper spray hole 3 of the conventional injection nozzle shown in Figure 1 are illustrated by the straight lines 1 1 and 12.
• a corresponding fuel spray jet included angle 13 is shown.
• Computer model simulations of the fuel spray jet for typical in-cylinder engine conditions at high load and speed show that the included fuel spray jet angle 13 is about 10 degrees proximal to the nozzle body 2 but can reach about 20 degrees at a radius RC close to the radius of the combustion chamber wall.
• the edges 11 and 12 of the fuel spray jet are curved.
• the increase in the included spray jet angle 13 and the width of the fuel spray jet is caused by the injection of the fuel spray jet into high air density and high ambient air motion in the combustion chamber especially at high engine speed and load conditions.
• the required maximum variation of the vertical spray jet target as represented by the values X1 and X2 in Figures 2A and 2B is of the order of 2mm for a typical engine combustion system. This corresponds to varying the spray hole axis angle 5 in Figure 1 by about 5 degrees. This compares with the included spray jet angle 13 of up to 20 degrees for a fuel spray jet from a single spray hole. Also, fuel spray jets that are directed along slightly different directions will tend to merge together owing to the jet entrainment process and the tendency to form a single round circular jet further downstream in the merged jet.
• the injection nozzle comprises a nozzle body 21 having a blind bore 22.
• the nozzle body 21 defines a primary nozzle axis A-A which is co-axial with the blind bore 22.
• the blind end of the bore 22 is provided with upper and lower spray holes 23, 24 and defines a seating with which a valve needle (not shown) is engageable to control the supply of fuel to the upper and lower spray holes or outlet openings 23, 24.
• the valve needle may be of the type described in EP-1626173, where inner and outer concentric valve needles are provided and are operable to control the flow of fuel through both the upper and lower spray holes together or through the upper spray hole 23 only.
• respective rows of upper and lower spray holes may be provided, each of the holes of the respective rows being located at the same axial position relative to the bore 22.
• the holes can be arranged so that adjacent pairs of spray holes 23, 24 in the upper and lower rows are directed so that the fuel spray jets merge to form a single fuel spray jet for each pair of spray holes 23, 24 giving the effect of a single large spray hole in terms of fuel mass flow and penetration of the fuel spray jet.
• the injection nozzle of the first embodiment is provided with means for permitting the selective injection of fuel through either the upper row of spray holes 23 only, or through both the upper and lower rows of spray holes 23, 24 together, as is known in the art.
• the means for permitting the selective injection of fuel may comprise a valve needle mounted for reciprocable movement within the bore 22 of the nozzle body 21 and having a construction of that described in EP-1626173. Accordingly, the injection nozzle is operable such that, at low engine loads and speeds, only the upper row of spray holes 23 is opened.
• the resulting fuel spray jet has an axis 27 which is determined by the axis of the upper spray hole 23. At the distance RC from the primary nozzle axis A-A, in a direction perpendicular to the axis A-A, the fuel spray jet from the upper spray hole 23 has a vertical target distance X2 below the cylinder head face 30.
• the distance RC is the radius of the combustion chamber, where the injection nozzle is mounted such that the primary axis A-A of the injection nozzle is coaxial with the primary axis of the combustion chamber.
• the distance RC may be an arbitrary reference distance, such as two thirds of the radius of the combustion chamber measured from the primary nozzle axis A-A.
• the reference distance is chosen such that the vertical target distance of the fuel spray jet from the upper spray hole 23 can be distinguished from the vertical target distance of a merged fuel spray jet produced by injection through both upper and lower spray holes 23, 24, as explained in detail below.
• the injection nozzle is operable such that fuel is injected through both the upper and lower rows of spray holes 23, 24.
• the same number of spray holes are provided in each row with the adjacent pairs of upper and lower spray holes directed so that the upper and lower fuel sprays merge to form a single spray jet.
• the edges of the spray jets from each respective pair of upper and lower spray holes 23, 24 start to merge sufficiently at a radius RM so as to form a single fuel spray jet at least towards the outer radii of the combustion chamber, i.e. at the distance RC.
• the merging of the spray jets is necessary at high engine loads and speeds in order to ensure adequate fuel spray jet penetration into the combustion chamber with the merged spray jet.
• the upper and lower edges of the merged spray jet are illustrated by the lines 14 and 15.
• the lower spray hole axis 28 is significantly below the upper spray hole axis 27 at the radius RC. This means that the effective direction of the merged fuel spray jet is along the axis 29, which gives a vertical target distance X1 below the cylinder head face 30. Accordingly, for the high load/engine speed operating condition, where fuel is injected through both the upper and lower rows of spray holes 23, 24 and the resulting merged spray jet has a vertical target distance X1 , it can be seen from Figure 2A that this corresponds to the optimum target distance for minimising smoke emissions (S3).
• the axis 29 of the merged spray jet will be midway between the spray hole axes 27 and 28 for the upper and lower spray holes 23, 24.
• the difference in the fuel spray jet vertical targets X2 and X1 in Figure 3 provides the required variation in spray jet vertical target direction between low engine speed and load conditions and high engine load and speed conditions. At the same time the required variation in the effective spray hole diameter as in the prior art is achieved with a change of engine load and speed condition.
• the injection nozzle is provided with means for permitting the selective injection of fuel through either the lower row of spray holes 33 only, or through both the upper and lower rows of spray holes 34, 33 together, as is known in the art.
• the means for permitting the selective injection of fuel may comprise a valve needle mounted for reciprocable movement within the bore 22 of the nozzle body 21 and having a construction of that described in EP-1637730. Accordingly, with the second embodiment it is possible to open the lower row of spray holes 33 only at low engine loads and speeds rather than the upper row of spray holes 34 only, as in the first embodiment.
• the resulting fuel spray jets have a vertical target distance X2 below the cylinder head face 30.
• both the upper and lower rows of spray holes 34, 33 are opened.
• the same number of spray holes are used in each row with the adjacent pairs of upper and lower spray holes 34, 33 directed so that the upper and lower fuel spray jet edges start to merge sufficiently at a radius RM so as to form a single fuel spray jet towards the outer radii of the combustion chamber, i.e. at the distance RC.
• the upper and lower edges of the merged spray jet are illustrated by the lines 16 and 17.
• the axis 39 of the merged spray jet will be midway between the spray hole axes 38 and 37 for the upper and lower spray holes 34, 33.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fuel-Injection Apparatus (AREA)

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Applications Claiming Priority (2)

Publications (1)

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Cited By (5)

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Citations (6)

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• 2008
  • 2008-04-14 GB GBGB0806705.0A patent/GB0806705D0/en not_active Ceased
• 2009
  • 2009-03-30 WO PCT/GB2009/050306 patent/WO2009127850A1/en not_active Ceased
  • 2009-03-30 EP EP09733295.1A patent/EP2268913B1/en not_active Not-in-force
  • 2009-03-30 US US12/937,283 patent/US8490888B2/en not_active Expired - Fee Related
  • 2009-03-30 JP JP2011503496A patent/JP2011516787A/ja active Pending

Patent Citations (7)

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