GB2320060A

GB2320060A - Connector for mixing fuel and a second fluid

Info

Publication number: GB2320060A
Application number: GB9725762A
Authority: GB
Inventors: Bernd Danckert; Walter Dorner; Torsten Guth; Werner Remmels
Original assignee: MTU Friedrichshafen GmbH; MTU Motoren und Turbinen Union Friedrichshafen GmbH
Current assignee: Rolls Royce Solutions GmbH
Priority date: 1996-12-05
Filing date: 1997-12-04
Publication date: 1998-06-10
Anticipated expiration: 2017-12-04
Also published as: ITMI972654A1; DE19650559C1; FR2756871B1; IT1296816B1; FR2756871A1; GB2320060B; GB9725762D0

Abstract

A connecting element 4 has a first inlet 2 for a fuel line and a second inlet 3 for a second fluid, preferably water, the first inlet 2 leading to a flow passage 5 which is surrounded by an annular space 31 into which the second fluid is discharged and nozzle bores at the periphery of the flow passage 5 connecting the annular space 31 with the flow passage 5; the nozzle bores being arranged at an acute angle to an axis coaxial to the flow direction of the fuel in the fuel passage 5. The outlet 12 of the flow passage 5 may be directly attached to a fuel injection nozzle 1. Preferably a nozzle insert 18 is placed in the flow passage 5 separating the annular gap 31 from the flow passage 5 and through which the nozzles bores pass. The nozzle bores may co-operate with grooves in the flow passage 5 to increase turbulence and assist the emulsifying effect. The fuel-water ratio is a function of engine operating conditions.

Description

1 J is 1 CONNECTING ELEMENT FOR THE INLET OF FUEL AND A SECOND FLUID INTO

AN INJECTION VALVE 2320060

The invention relates to a connecting element for the inlet of fuel and a second fluid, which in particular is insoluble in the fuel, into the fuel intake of an injection valve of a diesel engine having the features indicated in the preamble of Claim 1.

A connecting element of this type is known from WO 88/01019, in which it is fully integrated into the nozzle holder of the injection valve which together with the injection nozzle forms the fuel-injection valve. The connection for a second fuel discharges at an angle into the section of the fuel-intake bore to the injection nozzle provided in the nozzle holder. In addition to extensive modifications to the nozzle holder, this connecting element requires additional construction space for the connection of the supply line for the second fuel disposed radially on the nozzle holder. Depending on the installation conditions of individual engines, in this device structurally expensive modifications to the existing cylinder head and/or adjoining supply systems are required. Another disadvantage of the connection formed in the nozzle holder arises just from the inlet of the second fuel via the opening cross-section of a bore into the fuel intake. This does in fact result in interstratification of the second fuel in the high-pressure duct during the injection intervals but in this case charge lamination also takes place which in the following highpressure stages is gradually conveyed to the injection opening. It is not possible to have a supply to the injection nozzle, which is dependent on engine operation, with uniform mixing of fuel and the second fluid, independently of the metered quantities of fluid, via the intake to the injection nozzle.

DE-PS 969 853 discloses a preferably sharply tapered connecting element which is screwed into the injection 2 nozzle body. Two bores are formed in the connecting element, to which corresponding feed ducts are connected, on the one hand, and which, on the other hand, at an intersection downstream unite at an acute angle with an axially arranged main duct. The feeds for the different types of fuel to the injection nozzle are here designed to be correct in respect of flow and with the lowest possible losses. Optimum mixing of the fuels is also not provided thereby.

On the other hand, DE 44 14 488 Cl discloses an emulsifier device in which satisfactory intermixing with the liquid present therein is effected by a discharge of second fluid spaced apart over the periphery into a swirl chamber. An emulsifier device of this type is expensive in construction and is designed for the formation of an is emulsion with the most uniform possible proportions of the fluids contained therein. Mixture variations dependent on engine operation are just as unlikely to be found in such a device as individual inlet or feed to the cylinders.

Therefore, the invention set out in Claim 1 is based on the problem of feeding a mass flow of a second fluid, which is metered depending on engine operation and which is subject to large fluctuations, to an injection nozzle mixed in a uniformly satisfactory manner with the fuel intake, in a manner which is simple in respect of apparatus and which is economical.

Claims

In a device of the type defined this problem is solved by the characterising features of Claim 1. Advantageous developments are characterised in the sub-claims. One advantage of the connecting element of the invention lies in moving the inlet location of the second fluid into the fuel intake upstream of the injection valve. Accordingly, all modifications required for the inlet are limited to the connecting element. In particular, exten;.-tle modifications to existing injector designs are obviat,ed,since the connecting piece is disposed between the duct and the nozzle holder of the injection vil-ve and-is 3 connected to the latter. Accordingly, the subsequent installation of a two-fluid injection in existing engines is possible without substantial modifications to the fuelinjection system already provided. A particularly economical embodiment is represented by a connecting piece whose end portion on the outlet side is designed to be complementary to the connection on the intake side for the connecting piece of the fuelinjection duct, whereby it can be connected via the standardised connection for the fuel-injection duct to the nozzle holder of the injection valve. As a result of the advantageous arrangement of the connecting element being directly upstream of the fuelinjection valve the passage volume introduced into the injection nozzle is very low. It is thereby ensured that in each case the optimum fuel composition metered by the supply systems for the instantaneous engine operation is introduced into the injection nozzle without substantial advance. Therefore, suddenly changing operating conditions, for example during load shedding, can be corrected directly by way of the fuel quantity and the appropriate fuel composition, thereby obviating disadvantages for the continued engine operation. Since the optimum fuel composition is not determined solely by the quantitative relationships between the fuel and second fluid but the engine operation depends essentially on the quality of the respectively injected fuel mixture, means are formed in the connecting element which enable the intake for the second fluid to discharge into the liquid passage spaced apart over the periphery. An inlet of second fluid at locations spaced apart uniformly over the periphery and the volume distribution achieved thereby advantageously assist the fluid dynamic intermixing by shearing of the second fluid introduced under high pressure with the fuel flow, independently of the quantity of second fluid to be admitted. is 4 In a preferred embodiment, for uniform mixing of both fluids an equalising volume surrounding the fluid passage is provided, into which the second fluid delivered by the high-pressure supply system discharges through the feed duct and which communicates with the passage via nozzle bores. Particular significance is again attributed to the installation position according to the invention being directly upstream of the nozzle holder if water is atomised into the fuel whereby an emulsion is precisely formed in both fluids when the injection is intended to take place. The small duct volume between the water inlet and the injection-nozzle opening prevents local accumulations of large amounts of water during the injection intervals in this zone, which could lead to corrosion, on the one hand, and to operating defects, on the other hand. Moreover, the residual amount of emulsion always has pressure applied to it by the fuel subsequently delivered, which counteracts any separation of the emulsion into the emulsion constituents. one embodiment of the invention is illustrated by way of example in the drawings and will be described in more detail below, wherein: Figure 1 shows, in longitudinal section, a connecting piece according to the invention mounted between the fuel duct and the injection valve; Figure 2 shows a half-sectional view of a nozzle insert; Figure 3 shows a projected cross-sectional view along the line III-III in Figure 2; Figure 4 shows a partial view of detail IV in Figure 1; and Figure 5 shows a sectional view along the section line V-V in Figure 4. In Figure 1 a fuel-injection duct 2 and a feed duct 3 for a second fluid, in this case water, are connected according to the invention with a fuel-injection valve 1 via a connecting element 4. is The connecting element 4 is of substantially rotationally symmetrical design and as a flow passage has an axial bore 5 with a widening 6 of enlarged diameter in the end portion 7 on the inlet side. A tapered seating surface 10 adjoining the widening extends axially outwards and forms, at the transition with an internal thread 9 and together therewith, a connector 8 into which a connecting piece 21 of the fuel-injection duct 2 is screwed. A radial groove 11 is formed over a portion of the axial length of the widening 6. An intake bore 13 which is open towards the periphery of the connecting element 4 and has a tapered seating surface 15, discharges into this radial groove 11. The connecting piece 17 of the feed duct 3 for second fluid is pressed axially at the tapered seating surface 15. In the vicinity of the widening 6 at the axial length of the radial groove 11 a cylindrical sleeve-shaped nozzle insert 18 is inserted coaxially in the axial bore 5 of the connecting element 4 and is checked axially against a shoulder 19 by means of the end face of the connecting piece 21 of the fuel-injection duct 2 being screwed into the connector 8, and is thereby secured in position. As a variant of the example of embodiment described here, the nozzle insert 18 can also be inserted with radial and axial play into the widening 6 of the axial bore 5 so that under the action of the fluid stream introduced at high pressure via the intake bore 13 it is caused to rotate about the longitudinal axis of the axial bore 5. The nozzle insert 18 delimits the radial groove 11 with respect to the axial bore 5 and in this way separates an accumulation volume 31 annularly surrounding the axial bore 5 and acting as an equalising volume. Altogether four nozzle bores 20 leading from the outer circumferential surface to the inner circumferential surface are formed uniformly distributed over the periphery of the nozzle insert 18, the inlet openings 29 of which are situated on the cylindrical outer circumference in the vicinity of the radial groove and discharge into the axial bore 5 via outlet 6 openings 30 which are disposed tangentially to the crosssectional surface 14 of the nozzle insert 18 (Figure 3) at an acute angle a (Figure 2), which may be between 30'and 60' In conformity with the number of nozzle bores 20, longitudinal grooves 22 are formed in the peripheral wall of the axial bore 5, as shown in Figures 4 and 5. The nozzle bores 20 are aligned with respect to outlet openings 30 on the cylindrical inner circumferential surface in a manner that intensifies intermixing of the admitted second fluid by shearing into the fuel intake downstream of the outlet openings 30 of the nozzle bores 20 in the axial bore 5. By aligned arrangement of the nozzle bores 20 and the longitudinal grooves 22, in addition to an increase in turbulence, the admitted second fluid is admitted is additionally over a relatively long axial length into the fuel stream in the axial bore 5. At its end portion 24 on the outlet side, the connecting element 4 has an external thread 25 by way of which a sealing surface 26 formed at the outlet end is pressed axially against a tapered seating surface 23 on the nozzle holder 27 of the fuel-injection valve 1 and whereby a connection of the axial bore 5 is established via an outlet opening 12 to the fuelintake bore 28 in the nozzle holder 27 of the injection valve 1. The opening cross-sectional area of the outlet bore 12 is smaller than the crosssectional area 14 of the axial bore 5. The connecting element 4 operates as follows: the starting point for the following description is engine operation with injection of neat diesel fuel which, in known manner, is sucked from a fuel tank 33 and fed at high pressure by means of a high-pressure pump 32 via a pressure accumulator 34 and passes through the fuel-injection duct 2, and the axial bore 5 of the connecting element 4 to the intake bore 28 of the injection valve 1. During the injection interval the injection valve 1 is closed so that the fuel situated in the supply line 2,5,28 is acted upon by 7 a dynamic pressure which corresponds approximately to the system pressure of the high-pressure fuel pump. At the same time, water is introduced as second fluid by a high-pressure supply system 35 through the feed duct 3 laterally into the connecting element 4 and passes through the radial intake bore 13 into the accumulation volume 31, where it is distributed over the entire periphery of the nozzle insert 18. When the injection valve 1 is closed a non-return valve in the feed duct 3 for second fluid prevents diesel fuel from displacing water from the accumulation volume 31. If the injection valve 1 is opened during the injection stage, fuel flows under the injection pressure through the axial bore 5 into the intake bore 28 in the is nozzle holder 27 to the injection nozzle and from there into the combustion chamber of the diesel engine. With suitable adjustment of the system pressures of the fuel-injection system and of the supply system for second fluid, the water fed back into the accumulation volume 31 corresponding to the respective engine operation passes through the nozzle bores 20 into the axial bore 5 and thus into the fuel flow. Because of the arrangement of the nozzle bores 20, the water is atomised into the fuel flow over the entire periphery of the axial bore 5 and is intensively intermixed therewith. The symmetrical arrangement of the nozzle bores 20 ensures, on the one hand, the admission of water at locations spaced apart symmetrically over the flow periphery and, on the other hand, the radial component of each atomised water jet respectively results in the water jets colliding with one another at an imaginary point on the longitudinal centre axis of the axial bore 5 and thereby intensifies the mixing turbulence. The axial component of the atomised water jets prevents excessive retarding of the axially flowing fuel and thus reduces pulsations or oscillations in the intake duct. As is evident from Figure 3, the atomised water jets also have a tangential component by which the entire charge of fuel flow in the axial bore 5 8 is caused to undergo a rotating motion about the longitudinal axis. In particular the rotating motion of the water/fuel mixture in the vicinity of the axial bore 5 in cooperation with the longitudinal grooves 22 spaced apart uniformly over the inner wall of the axial bore 5, with a suitable arrangement of the nozzle bores 20 in the peripheral direction relative to the longitudinal grooves 22, induces additional shear in the flow which assists the emulsion formation. The mixed flow or emulsion in the axial bore 5 subjected to turbulence by the aforementioned radial, axial and peripheral components of the water nozzle jets finally passes, under the action of the fed back fluid flows, through the outlet opening 12 into the intake bore 28 to the injection nozzle. When the fuel-water emulsion overflows from the axial bore 5 into the intake bore 28 it passes through the outlet bore 12 in the form of a restrictor. The high flow velocities at the small cross-sectional area of the outlet bore 12 additionally improve the distribution of the water or intermixing of the water in the fuel so that, finally, a homogeneous highquality emulsion reaches the injection nozzle. If the injection valve 1 is closed, during the injection interval the fuel-injection duct 2 and the axial bore 5 in the vicinity of the nozzle insert 18 are filled with fuel and the axial bore 5 downstream of the nozzle insert 18 and the intake bore 28 in the injection valve 1 are filled with the fuel-water emulsion which was formed during the preceding injection.

1 2 3 4 9 List of Reference Numerals fuel-injection valve fuel-injection duct feed duct for second fluid connecting element axial bore 6 - widening 7 - end portion on the inlet side 8 - connector 9 - internal thread seating surface 11 - radial groove 12 - outlet opening 13 - intake bore 14 - cross-sectional area - seating surface 16 - connecting element 17 connecting piece 18 - nozzle insert 19 - shoulder 20 nozzle bore 21 connecting piece 22 - longitudinal groove 23 - seating surface 24 - end portion on the outlet side 25 - external thread 26 - tapered seating surface 27 - nozzle holder 28 - intake bore 29 - inlet opening 30 - outlet opening 31 - accumulation volume 32 - high- pressure pump 33 - fuel tank 34 - pressure accumulator 35 - high-pressure injection system for second fluid CLAIMS 1. A connecting element for the inlet of fuel and a second fluid, which in particular is insoluble in the fuel, into the fuel intake of an injection valve of a diesel engine, comprises a connector for a fuel line and a connector for a supply means for the second fluid, with a flow passage fluid tightly connected on the intake side to the fuel line and on the outlet side to the fuel intake of the injection nozzle supplied with fuel by a high-pressure pump, in particular via a pressure accumulator, and also with an intake for the second fluid discharging into the flow passage between the inlet and outlet, the connecting element forming an end portion on the outlet side which can be connected to the nozzle holder of the fuel-injection is nozzle, wherein a substantially rectilinear flow passage i provided, separately from the flow passage an equalising volume surrounding the flow passage is formed, into which the intake bore for the second fluid discharges, and nozzle bores spaced apart over the periphery of the flow passage are provided at an acute angle to an axis coaxial to the flow direction in the flow passage and which connect the equalising volume to the flow passage.

2. A device according to Claim 1, wherein the nozzle bores which discharge into the flow passage are spaced apart symmetrically over the periphery.

3. A device according to Claim 1 or Claim 2, wherein the nozzle bores are provided at an angle of 300 to 600.

4. A device according to any one of the preceding claims, wherein the nozzle bores which discharge into the flow passage have a tangential component relative to the periphery of the flow passage.

1\ J

5. A device according to Claim 1, wherein the crosssectional area of the flow passage on the intake side is larger than the cross-sectional area on the outlet side.

6. A device according to any one of the preceding claims, wherein the equalising volume is separated by means of a nozzle insert with respect to the flow passage, in the walls of which there are formed nozzle bores by way of which the equalising volume is connected with the flow passage so as to convey fluid.

7. A device according to Claim 6, wherein the flow passage is in the form of a stepped bore with essentially three diameters arranged axially one behind the other and increasing towards the end portion on the inlet side, wherein an annular radial groove is provided in the vicinity of the second diameter, which is in conveying communication with the intake bore for the second fluid, and the cylindrical sleeve-shaped nozzle insert is inserted coaxially in the second diameter.

8. A device according to Claim 1, wherein the end portion on the outlet side is formed complementarily to the connector on the intake side for the connecting piece of the fuel-injection duct.

9. A connecting element for the inlet of fuel and a second fluid into an injection valve of a diesel engine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.