JP2009281274A - Gas fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas fuel injection device capable of simultaneously achieving both of high output and prevention of delivery of unburned gas fuel by accelerating mixing of gas fuel with compressed air in the gas fuel injection device for injecting the high pressure gas fuel into an engine combustion chamber. <P>SOLUTION: The gas fuel injection device where the gas fuel is injected under the condition that an injection pressure P<SB>INJ</SB>of the gas fuel and an atmosphere pressure P<SB>AMB</SB>in the combustion chamber has the following relationship of P<SB>INJ</SB>/P<SB>AMB</SB>≥4, satisfies the relationship of L<SB>P</SB><Lm(max) wherein a distance from an opening end face of a first injection hole to an intersection point P of a center axis of the first injection hole and a center axis of a second injection hole is an intersection point distance LP with a Mach disk generation region where a Mach disk is formed in a gas jet injected from the injection hole is Lm(max). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gaseous fuel injection device that injects high-pressure gaseous fuel into an internal combustion engine.

  From the viewpoint of energy management, gas fuels such as natural gas (LNG, CNG), liquefied petroleum gas (LPG), and hydrogen gas are used as fuels to replace conventional liquid fossil fuels in the development of next-generation automotive internal combustion engines. Development of a gas fuel engine to be used is required.

  However, gaseous fuel cannot inject a required amount of fuel in a short period of time due to its low energy density, which may cause insufficient output. Furthermore, it is difficult to mix the gaseous fuel and the compressed air in the combustion chamber, and control of self-ignition by promoting the mixing is an issue. For this reason, various techniques have been studied for the purpose of improving output shortage and promoting mixing.

  For example, Patent Document 1 discloses an injector for injecting high-pressure gaseous fuel into an engine combustion chamber from an injection hole provided at a nozzle tip, a high-pressure gaseous fuel supply passage for supplying high-pressure gaseous fuel to the injection hole, and an injection hole An electric drive unit that controls the drive of the needle that opens and closes the nozzle, and further, the cross-sectional area of the high-pressure gas fuel supply passage is rapidly increased in the direction from the nozzle hole side to the upstream side in the high-pressure gas fuel supply passage in the nozzle. Since the volume expanding part to be expanded is provided and the volume expanding part having a predetermined volume is provided in the high pressure gas fuel supply passage in the nozzle close to the nozzle hole, a large amount of high pressure gas fuel is supplied to the nozzle hole at the initial stage of injection. In addition, by using the pressure wave generated during injection, a large amount of gaseous fuel can be injected into the engine combustion chamber at a high pressure in a short time, and mixing with air is promoted to increase output. To prevent the discharge of unburned gaseous fuel Sometimes feasible gaseous fuel injector is disclosed.

Further, in order to improve the output shortage, it is necessary to inject gaseous fuel into the engine combustion chamber from the nozzle hole provided at the tip of the nozzle at an extremely high pressure, but the following phenomenon may occur in the gas injected at high pressure. Are known.
Non-Patent Document 1 and the like show an analysis related to a gas jet. As shown in FIG. 11, the high-pressure gas injection pressure _{P INJ} a single injection hole nozzle _{I S} is injected into the low pressure atmosphere of the ambient pressure _{P AMB,} injection pressure _{P INJ} and the ambient pressure ratio _P between the pressure _{P AMB INJ} / When _PAMB is four times or more, in the vicinity of the nozzle hole outlet, the gas injected from the nozzle hole cannot be completely expanded to the atmospheric pressure _PAMB, resulting in an underexpanded jet. In such an underexpanded jet, an expansion wave ExW expanding outward is generated, and the flow velocity at this time becomes supersonic (M> 1), and is reflected as a compression wave CmW at the boundary surface JB between the jet and the atmospheric gas. Then, it is reflected again at the jet boundary surface JB and becomes the expansion wave ExW, and the compression wave CmW and the expansion wave ExW are repeatedly generated again. In particular, when the pressure ratio P _INJ / P _AMB is large, the shock cannot normally intersect on the central axis of the jet FJ, and a barrel shock wave BS is formed by the combination and interference of the expansion wave ExW, the compression wave CmW, and the reflected wave RS. Then, a disk-shaped Mach disk MD perpendicular to the injection direction is formed, and a supersonic (M> 1) expansion wave region and a subsonic (M <1) compression wave region are formed with the Mach disk MD as a boundary. It is known (Nonpatent literature 1 etc.).
JP 2006-14474 A Proceedings of the Japan Opportunity Society (Part B) Vol. 72, No. 721 (2006/9) No.06-0160 Influence of nozzle shape on near-field structure of underexpanded sonic jet Yumiko Otobe and others

  For this reason, when high pressure gaseous fuel is injected using a conventional fuel injection valve, the gaseous fuel is confined in the barrel shock wave BS, and the gaseous fuel and the compressed air in the combustion chamber are slightly in the vicinity of the jet boundary JB. Although mixed, gaseous fuel and compressed air in the combustion chamber hardly mix in the barrel shock wave BS. Further, the speed of the jet is gradually lost, and outside the Mach disk formation region Lm (max), the speed of the jet is reduced and its kinetic energy is extremely small, so that it may take time to mix with the air. .

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a gaseous fuel injection device that can facilitate mixing of gaseous fuel and compressed air in a gaseous fuel injection device that injects high-pressure gaseous fuel into an engine combustion chamber. It is.

In the first aspect of the invention, a fuel injection valve having at least two injection holes including at least a first injection hole and a second injection hole is provided, and high-pressure gaseous fuel introduced into the fuel injection valve is provided. , A gaseous fuel injection device for injecting into the combustion chamber of the internal combustion engine from the nozzle hole, where the injection pressure of the gaseous fuel is _PINJ and the atmospheric pressure in the combustion chamber is _PAMB , In the gaseous fuel injection device for injecting the gaseous fuel under the condition satisfying the relationship, the central axis of the first injection hole and the central axis of the second injection hole from the opening end surface of the first injection hole. When the distance to the intersection _P is defined as the intersection distance L _P and the Mach disk generation region in which the Mach disk is formed in the gas jet injected from the nozzle hole is defined as Lm (max), The center axis of the first injection hole and the center of the injection valve Setting a first injection angle theta ₁ and the second formed by the central axis of the central shaft and the injection valve of the second injection hole of the injection angle theta ₂ formed by the.
P _INJ / P _AMB ≧ 4 Equation 1
L _P <Lm (max) ... Formula 2

  According to the invention of claim 1, a plurality of jets collide in the vicinity of the exit of the nozzle hole, the shock cell structure is destroyed by the collision of the barrel shock wave, and the jet is greatly disturbed, so that the kinetic energy of the gaseous fuel is large. Thus, mixing with compressed air becomes possible, and mixing of gaseous fuel and air is promoted. Therefore, it is possible to realize a fuel injection device capable of suppressing the discharge of unburned gaseous fuel into the combustion exhaust by rapid mixing of gaseous fuel and compressed air.

Specifically, as in the invention of claim 2, the intersection distance L _P is set to a range of 6 mm or less. Further, as in the invention of claim 3, the intersection distance L _P is set in a range of 0.01 mm or more. It has been found that if a plurality of jets are crossed within the scope of the inventions of claims 2 and 3, the gaseous fuel jets collide with each other with high kinetic energy, and a large turbulence can be generated.

More specifically, the first injection angle θ ₁ formed by the central axis of the first injection hole and the central axis of the injection valve is set to satisfy the relationship of the expression 2 as in the invention of claim 4. It is desirable to set the second injection angle θ ₂ formed by the central axis of the second injection hole and the central axis of the injection valve so that θ ₁ > θ ₂ .

  Furthermore, as in the invention of claim 5, it is desirable that the distance Dp between the plurality of nozzle holes is set to 6 mm or less.

  As in the sixth aspect of the invention, it is desirable that the nozzle hole has an opening diameter De of 0.01 mm or more.

  A gaseous fuel injection device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an overall configuration in which a gaseous fuel injection device of the present invention is applied to an internal combustion engine 3. A cylinder head 30 of the internal combustion engine 3 includes a gaseous fuel injection valve I, an ignition device (not shown), and an intake cylinder. 301, an intake valve 302, an exhaust cylinder 303, and an exhaust valve 304 are provided. The air-fuel mixture is ignited. As the gaseous fuel, hydrogen, CNG (compressed natural gas), LNG (liquefied natural gas), DME (dimethyl ether) or the like is used. The gaseous fuel injection valve I is supplied with a high-pressure gaseous fuel GF from a high-pressure source 5 such as a pressure accumulator connected to a high-pressure cylinder or a common rail accumulated by a high-pressure pump.

The electronic control unit ECU4 detects the in-cylinder pressure P _AMB in the combustion chamber, the high-pressure gaseous fuel injection pressure P _INJ , the engine speed NE, the engine water temperature WT, the accelerator opening, the top dead center, and the like. The load status is input, and the fuel injection timing, injection pressure, injection amount, ignition timing, etc. are calculated according to the load status, sent to the drive control unit EDU41, and the gaseous fuel injection valve I is set at a predetermined timing by the EDU41. Driven. Particularly in the present invention, high-pressure gaseous fuel is injected into the combustion chamber 34 under the condition where the pressure ratio _P INJ _{/ P AMB} and injection pressure _{P INJ} and the in-cylinder pressure _{P AMB} is 4 or more.

In FIG. 2, the outline | summary of the gaseous fuel injection valve I used for the gaseous fuel injection apparatus in the 1st Embodiment of this invention is shown. The gaseous fuel injection valve I includes a nozzle part 100, an injector base part 110, and an actuator part 120.
The injector base 110 includes a high-pressure gaseous fuel introduction passage 103 for introducing high-pressure gaseous fuel, a pressure accumulating chamber 102 for accumulating the pressure of the introduced high-pressure gaseous fuel, and gaseous fuel in the fuel chamber 10 formed in the nozzle portion 100. A gaseous fuel supply channel 101 to be introduced is formed.
Further, a known working liquid that transmits a pressure acting on one or both of the ascending direction and the descending direction of the needle 200 to the injector base and introduces a working liquid to lubricate the sliding part of the needle 200. A flow path 120 is appropriately formed.
A needle shaft portion 20 having a small diameter is formed on the distal end side of the needle 200. A fuel chamber 10 is defined around the needle shaft portion 20, and nozzle holes 14 and 15 provided at the distal end of the fuel chamber 10. A valve body 2 that opens and closes by opening and closing is formed at the tip of the needle shaft portion 20.
A long-axis needle 200 that is slidably held in the axial direction is accommodated inside the injector base 100, and an actuator 120 connected to the EDU 41 is provided on the proximal end side of the needle 200. The needle 200 is controlled to move up and down in the axial direction. As the actuator 120, known drive control means such as an electromagnetic actuator using an electromagnetic solenoid excited by energization or a piezoelectric actuator using a piezoelectric element extending by energization can be appropriately used.

With reference to FIG. 3, the structure of the front-end | tip of the nozzle part 100 of the fuel injection valve I which is the principal part of the gaseous fuel injection apparatus in the 1st Embodiment of this invention is explained in full detail.
In the present embodiment, the valve body 2 is formed in a substantially conical shape. Inside the nozzle base 1, there are formed sheet surfaces 11, 12 formed in a substantially bowl shape that penetrates the fuel chamber 10, and a sac chamber 13 whose tip is closed, and a first injection hole 14 and a second injection hole 14. A nozzle hole is formed.
The first nozzle hole 14 is provided at an angle of the first nozzle hole drilling angle θ ₁ with respect to the central axis of the nozzle portion, and the second nozzle hole 15 is second with respect to the central axis of the nozzle portion. The nozzle hole is provided at an angle θ ₂ . The first nozzle hole drilling angle θ ₁ is set to be larger than the second nozzle hole drilling angle θ ₂ , and the central axis of the first nozzle hole 14 and the center axis of the second nozzle hole 15 are at an intersection P. Crossed.
The intersection distance LP from the outlet end of the first injection hole 14 to the intersection P is set to be shorter than the Mach disk formation region Lm (max).
Further, the first nozzle hole 14 and the second nozzle hole 15 are provided apart from each other by a distance D _P between nozzle holes at the nozzle hole outlet, and D _P is set to 6 mm or less. Further, the nozzle hole 14 and the nozzle hole 15 have an outlet opening diameter φDe set to 0.01 mm or more.
When the valve is closed, the valve body 2 descends, and the first seat surface 11 and the second seat surface 12 formed inside the nozzle portion 1, the first valve seat portion 21 of the valve body 2, and the second seat surface 2. The valve seat 22 is in contact with each other, and the first nozzle hole 14 and the second nozzle hole 15 are closed.
When the valve is opened, the valve body 2 rises, and the first seat surface 11 and the second seat surface 12 formed inside the nozzle portion 1, the first valve seat portion 21 of the valve body 2, and the second seat surface 2. The valve seat part 22 is separated, and the first nozzle hole 14 and the second nozzle hole 15 are in a state of being in communication with the fuel chamber 10.

The relationship between the Mach disk formation region Lm (max) and the pressure ratio P _INJ / P _AMB will be described with reference to FIG. In this embodiment when the outlet opening diameter φDe is 1.0 mm, the Mach disk formation region Lm (max) with respect to the change in the pressure ratio P _INJ / P _AMB between the injection pressure P _INJ and the in-cylinder atmosphere pressure P _AMB Changes in direct proportion. If the intersection distance LP from the opening outlet De of the first nozzle hole 14 to the intersection P is 6 mm or less, the intersection P is found to be within the range of the Mach disk formation region Lm (max).

The effects of the present invention will be described with reference to FIGS.
As shown in FIG. 5A, in the first embodiment of the present invention, the first injection hole 14 and the second injection hole 15 are connected to the first injection hole forming angle θ1 and the second injection hole. When drilling is performed so that the drilling angle θ2 satisfies the relationship θ1> θ2 and L _P <Lm (max), L ₁ on the central axis from the opening outlet of the first injection hole 14 , L ₂ , L ₃ , and L ₄ , the measurement results P ₁ , P ₂ , P ₃ , and P ₄ of the fuel gas concentration at the distances are taken as Example 1, and as shown in FIG. In the first embodiment, the first nozzle hole 14 and the second nozzle hole 15 have a first nozzle hole drilling angle θ ₁ and a second nozzle hole drilling angle θ _{2 such} that θ ₁ > θ _2. satisfies the relationship, and, _{L P} ≧ Lm when bored so that the (max), _L 1 of the central axis from the opening outlet of the first nozzle holes _14, L _{2, L} 3, Measurement of the concentration of fuel gas at a distance of _{4 P 1,} P _2, P 3, and _{P 4} and Example 2, as shown in FIG. 6 (a), a first injection hole 14 second injection holes 15 in which the first nozzle hole drilling angle θ1 and the second nozzle hole drilling angle θ2 are drilled so as to be in a relationship of θ ₁ = θ ₂ , that is, parallel to each other. The measurement results P ₁ , P ₂ , P ₃ , P ₄ of the concentration of the fuel gas at the distances L ₁ , L ₂ , L ₃ , L ₄ on the central axis from the opening exit of the hole 14 are referred to as Comparative Example 1, and FIG. As shown in (b), the first nozzle hole 14 and the second nozzle hole 15 are formed such that the first nozzle hole forming angle θ1 and the second nozzle hole forming angle θ2 are θ ₁ <θ _2. in the case where bored so that the relation, L ₁ of the central axis from the opening outlet of the first nozzle holes _{14, L 2,} L _3, measurement results of the concentration of fuel gas in the distance L ₄ As P _{1, P 2,} P 3, compared _{P 4} Example 2 and the results are shown in Figure 7.

As shown in FIG. 7, in the case of Comparative Examples 1 and 2, the distance is not reduced much the concentration of the gaseous fuel be separated, at a distance L _4, rapidly because it is a concentration drop, the surrounding compressed air It is inferred that the mixing with is not performed. On the other hand, in Examples 1 and 2 of the present invention, in the vicinity of the opening outlet L1 of the _first nozzle hole 14, although the gas concentration was similar to that in Comparative Examples 1 and ₂ , the position of L2 in a rapid reduction in the gas concentration was observed, further gas concentration in L ₃ but becomes lower in the L _4, it was found that a higher gas concentration than Comparative examples 1 and 2. Further, it was found that the density drop occurred in Example 1 at a shorter distance than in Example 2.
Therefore, according to the present invention, the high-pressure gas jet injected from the first nozzle hole 14 and the second nozzle hole 15 collides in the Mach disk formation region, and thus has high kinetic energy. It is presumed that the jet flow collided in the state was greatly disturbed, the mixing with the surrounding compressed air became active, and the concentration decreased rapidly.

With a fuel injection device of the first embodiment of the present invention in FIG. 8, the intersection distance LP to an intersection P when the pressure ratio _P INJ _{/ P AMB} 10 of a fuel injection pressure _{P INJ} and the ambient pressure _{P AMB} It shows the gas concentration uniformity when changing.
The gas concentration uniformity is an average value of gas fuel concentrations at three points when the measurement distance is 30 mm, 40 mm, and 50 mm.
As shown in the figure, it has been found that the uniformity of the gaseous fuel concentration becomes high when the intersection distance L _P is 6 mm or less.
Also from this test result, it was found that the gas fuel concentration can be made uniform quickly by causing the first nozzle hole 14 and the second nozzle hole 15 to collide with each other within the range of the Mach disk formation region Lm (max). .

9 and 10 are cross-sectional views showing the main part of another embodiment of the present invention.
As shown in this figure (a), the first nozzle hole 14a may be drilled in the sack chamber 13, and the second nozzle hole 15a may be drilled in the seat portion. As shown, both the first nozzle hole 14b and the second nozzle hole 15b may be formed in the sack chamber 13b. In either case, the same effect can be obtained as long as the intersection point P of the present invention is provided in the Mach disk formation region Lm (max).

  Furthermore, as shown to Fig.10 (a), it is good also as a structure which provides the 1st nozzle hole 14c, the 2nd nozzle hole 15c, and the 3rd nozzle hole 16c, and 3 or more gas jets cross | intersect. In addition, as shown in FIG. 4B, the nozzle holes are not drilled in the wall surface at the tip of the nozzle, but a plurality of nozzle holes 14d are drilled in the disc-shaped nozzle hole plate 17, and the central axes thereof are formed. The crossing point P may be within the Mach disk formation area Lm (max).

In addition, this invention is not limited to the said embodiment, The high pressure gaseous fuel injected from a some nozzle hole is made to collide in a Mach disk formation area, and rapid mixing with gaseous fuel and cylinder air is aimed at. Modifications can be made as appropriate without departing from the spirit of the present invention.
For example, in the description of the above embodiment, although a specific needle driving method is not specified, the pressure of the pressure fluid is applied in the valve opening direction and the valve closing direction, and the control valve is operated by the driving actuator. A known driving method for raising and lowering the needle by changing the balance between the pressure in the valve opening direction and the pressure in the valve closing direction can be appropriately employed.
In the above embodiment, the effect of the present invention is exhibited at any injection timing as long as the pressure ratio P _INJ / P _AMB between the fuel injection pressure P _INJ and the in-cylinder atmospheric pressure P _AMB is equal to or higher than a predetermined pressure. The However, if fuel injection is performed in a state where the in-cylinder atmospheric pressure PAMB is low, in addition to the effect of the present invention, the tumble vortex generated in the cylinder when the cylinder piston is raised further mixes the gaseous fuel and the compressed air. Can also be expected to promote.
Furthermore, in the above embodiment, an example in which the present invention is applied to an internal combustion engine provided with an ignition device has been described. However, a self-igniting liquid fuel such as light oil is mixed with a gaseous fuel in a small amount. Applicable to ignition engines.

The block diagram which shows the outline | summary of the internal combustion engine provided with the gaseous fuel injection apparatus in the 1st Embodiment of this invention. The partial cross section figure which shows the outline | summary of the gaseous fuel injection valve used for the fuel-injection apparatus in the 1st Embodiment of this invention. The principal part sectional view of the gaseous fuel injection valve used for the fuel injection device in a 1st embodiment of the present invention. The characteristic view which shows the change of the intersection distance L _P and the Mach disk formation area Lm (max) with respect to the pressure ratio P _INJ / P _AMB . (A) is principal part sectional drawing which shows the structure of Example 1, (b) is principal part sectional drawing which shows the structure of Example 2. FIG. (A) is principal part sectional drawing which shows the structure of the comparative example 1, (b) is principal part sectional drawing which shows the structure of the comparative example 2. FIG. The characteristic view which shows the effect of this invention with a comparative example. It shows the effect of the present invention, the characteristic diagram of the gas concentration uniformity for intersection distance L _P. (A), (b) is principal part sectional drawing which shows the modification of this invention. (A), (b) is principal part sectional drawing which shows the modification of this invention. These are the conceptual diagrams which show the phenomenon in the nozzle hole vicinity of the single nozzle hole for high-pressure gaseous fuel injection.

Explanation of symbols

I Fuel injection valve 1 Nozzle tip 10 Fuel chamber 11, 12 Seat portion 13 Suck chamber 14 First injection hole 15 Second injection hole 2 Valve body 21, 22 Valve body seating portion P _INJ Fuel injection pressure P _AMB cylinder Atmospheric pressure Lm (max) Mach disk formation region D _P inter-hole distance φDe injection hole outlet opening diameter P injection hole center axis intersection L _P intersection distance θ ₁ first injection hole formation angle θ ₂ second injection hole Angle

Claims (6)

A fuel injection valve provided with two or more injection holes composed of at least a first injection hole and a second injection hole is provided, and high-pressure gaseous fuel introduced into the fuel injection valve is transferred from the injection hole to the internal combustion engine. A gaseous fuel injection device for injecting into the combustion chamber,
In the gaseous fuel injection device for injecting the gaseous fuel under a condition satisfying the relationship of the following formula 1 when the injection pressure of the gaseous fuel is P _INJ and the atmospheric pressure in the combustion chamber is _PAMB :
The distance from the opening end face of the first nozzle hole to the intersection point P between the central axis of the first nozzle hole and the central axis of the second nozzle hole is defined as an intersection distance L _P, and the gas injected from the nozzle hole A gaseous fuel injection device satisfying the relationship of the following formula 2 when a Mach disk generation region where a Mach disk is formed in a jet is Lm (max).
P _INJ / P _AMB ≧ 4 Equation 1
L _P <Lm (max) ... Formula 2 The gaseous fuel injection device according to claim 1, wherein the intersection distance L _P is set in a range of 6 mm or less. The gaseous fuel injection device according to claim 1 or 2, wherein the intersection distance L _P is set in a range of 0.01 mm or more. In order to satisfy the relationship of Formula 2, the first injection angle θ ₁ formed by the central axis of the first injection hole and the central axis of the injection valve, the central axis of the second injection hole, and the injection valve 4. The gaseous fuel injection device according to claim _{1, wherein a second} injection angle θ ₂ formed with the central axis is set to satisfy θ ₁ > θ _{2. 5} .   The gaseous fuel injection device according to any one of claims 1 to 4, wherein a distance Dp between the plurality of nozzle holes is set to 6 mm or less. The gaseous fuel injection device according to any one of claims 1 to 5, wherein an opening diameter De of the injection hole is formed to be φ0.01 mm or more.

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