FI120886B - Fuel injection system for piston engine - Google Patents

Abstract

The invention relates to a common rail fuel injectionsystem(1) for a piston engine with several cylinders (12). The fuel injection system (1) comprises at least one pressure accumulator (7, 8, 18) for pressurized fuel, injectors (6) for injecting pressurized fuel into the cylinders (12) and a leakage channel arrangement (24) for removing fuel leaking from the injectors (6). The leakage channel arrangement (24) is provided with a leak detector (28) for detecting a fuel leak.

Description

FUEL INJECTION SYSTEM FOR PISTON ENGINE

The invention relates to a fuel injection system for a piston engine according to the preamble of claim 1.

5 Common rail fuel injection systems are commonly used to improve the performance of piston engines. In the common rail system, pressure generation and fuel injection are functionally separated. Fuel 10 is fed to the common pressure reservoir by a high pressure pump, from where it is led through separate pipes to the injection nozzle of each cylinder.

It is an object of the present invention to provide an improved fuel injection system for a piston engine.

15

The object of the invention is achieved by a fuel injection system according to claim 1. The fuel injection system according to the invention comprises at least one injection accumulator for pressurized fuel and injection nozzles connected to the accumulator or accumulators:. 20 for injection of pressurized fuel into the cylinders. The system consists of • · · •. ·. still leaking fuel from the spray nozzle arrangement nozzles • · · • ·· ·. to remove. The leakage duct arrangement has a leak detector • · · ·:. ·. to detect.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 schematically illustrates one fuel injection system according to the invention. Figure 2 is a cross-sectional view of a fuel injection nozzle that can be used in the fuel injection system of Figure 1, Figure 3 is a cross-sectional view showing the connection of the feed pipe to the fuel injection nozzle and the cylinder nozzle. 4 is a cross-sectional view of a leaking fuel detector that may be used in the fuel injection system of FIG. 1.

Figure 1 schematically illustrates a fuel injection system 1 for a large piston engine, e.g., a diesel engine, based on a common rail system. A large piston engine refers to engines that can be used, for example, as main or auxiliary engines in ships or power plants. The engine can be run on heavy 15 fuel oil. The fuel injection system 1 comprises a fuel source, e.g. a fuel tank 2, from which fuel is fed by a low pressure pump 3 through a fuel line 4 to a high pressure pump 5 which in turn raises the fuel pressure to a level sufficient to inject into the injection nozzles 6.

The fuel injection system 1 comprises at least one pressure accumulator 7, 8: 1X for high pressure fuel. The system shown in Figure 1 comprises two. a separate battery 7, 8 arranged in fluid communication with one another via an M · · connecting pipe 9. Fuel is supplied from the high pressure pump 5 • ·. ·· 1. 25 to the first pressure accumulator 7 from which fuel is further supplied to the second pressure accumulator 8 via a connecting pipe 9. In addition, each injection nozzle 6 may be provided with an injector nozzle accumulator 18 to which fuel is supplied from the pressure accumulators 7,8. to heat it, it can be circulated in the injection system 1 before the engine is started. The second pressure accumulator 8 also has a spare valve 11 for maintaining pressure in the pressure accumulators 7, 8 and / or the injection nozzle accumulators 18 below a predetermined maximum value. The backup valve 11 may also be used, if necessary, to release pressure from the pressure accumulators 7, 8 and / or the pressure accumulators 18 of the injection nozzles 18. The volume of the pressure accumulators 7, 8 may be determined by the formula: 5

Vacc = S! {Vinj1Ninj) where VaCc = volume of the accumulator,

Vinj = the amount (volume) of fuel injected by the injection nozzle during one 10 injection procedure at full (100%) engine load,

Ninj = number of injection nozzles connected to said battery with a value of S between 50 and 100.

The fuel injection system 1 comprises injection nozzles 6 for injecting fuel 15 into the engine cylinders 12. The structure of the fuel injection nozzles 6 is illustrated in more detail in Figure 2. The injection nozzles 6 are mounted on the engine cylinder head 13. 13 for drilling 35.

"... 20 In the embodiment shown in Fig. 1, a plurality of injection nozzles are connected to each of the pressure accumulators 7,8;

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:: 1: 7, 8 connect only one injection nozzle 6. The pressure accumulators 7, 8 are supplied with · · · · j: 1: fuel for the injection nozzles 6 through the supply lines 14. Feed pipes 14: V: equipped with double walls. The inner flow space 25 of the feed pipe 14 is for high pressure fuel and the outer flow space serves as a conduit for any leakage fuel. The outer flow spaces of the feed pipes are: · · ·: in flow communication with a fuel leak detection system that may be · · »provided with a pressure accumulator 7, 8. Examples of such fuel leakage *: ··: detector systems are described in EP Patent 1,150,006.

·: ··: 30 • · · · · · 4 ·

The injection nozzle 6 comprises a body 15 provided with a valve needle 16 to guide fuel injection from the fuel chamber 17 to the cylinder 12. Depending on the position of the valve needle 16, fuel injection from the fuel chamber 17 to the cylinder 12 is either allowed or denied.

The injection nozzle 6 comprises an injection nozzle pressure accumulator 18 into which fuel is supplied through the supply pipe 14. The injection nozzle pressure accumulator 18 has a volume of at least 40, typically 60-100, times the amount (volume) of fuel injected by the injection nozzle during one injection event at full (100%) engine load.

10 Fuel is supplied from the injection nozzle pressure accumulator 18 through the conduit 34 to the fuel chamber 17. A flow fuse 19 is provided between the injection nozzle pressure accumulator 18 and the fuel chamber 17.

The injection nozzle 6 comprises a control chamber 20 to which fuel is supplied through a supply pipe 14. The fuel pressure in the control chamber 20 acts on the valve needle 16. The pressure of the fuel in the control chamber 20 forces the .. 20 valve needle 16 towards the closed position. The movement of the valve needle 16, and thus also the injection of fuel into the cylinder 12, can be controlled by the prevailing pressure in the control chamber. A return pipe 21 is provided in the injector nozzle 6 to remove fuel from the control chamber 20. The return pipe 21 is provided or connected to a second bore 42 in the cylinder head 13.

• · · • · .1 ··. 25 Fuel removed from control chamber 20 via return pipe 21 ··· is used to control fuel injection from injection nozzle 6.

: 1 · 1: A control valve 22 is provided in the return pipe 21 to control the fuel discharge from the control chamber 20. The control valve 22 may be a solenoid valve.

· ·

The control chamber inlet has a throttle limiting the fuel flow to the control chamber 20. The injection nozzle 6 is also provided with a spring 23 which forces the valve needle 16 toward the closed position.

The control valve 22 is opened to initiate fuel injection. Fuel flows from the control chamber 20 to the return pipe 21 and the fuel pressure in the control chamber 22 decreases. The fuel flows through the return pipe 21 to the fuel tank 2. The fuel pressure in the return pipe 21 is typically about 4 bar or more than 4 bar. When the pressure in the control chamber 22 is sufficiently low, the force exerted by the fuel pressure in the fuel chamber 17 forces the valve needle 16 toward the open position against the force of the spring 23. As a result, the valve needle 16 rises from its seat and the fuel 10 is injected from the fuel chamber 17 into the cylinder 12. As the control valve 22 closes, the fuel pressure in the control chamber 20 rises. As a result, the valve needle 16 returns to its closed position against the seat so that the injection of fuel from the fuel chamber 17 into the cylinder 12 stops.

15 The fuel injection system 1 is provided with a leakage channel arrangement 24 from the injection nozzles 6 from the so-called. to remove dirty leakage. A dirty leak is an unwanted fuel leak from the injector nozzles 6, e.g. leakage between injector nozzle parts and / or a mixture of fuel and injector seal oil. The leakage channel arrangement 24 comprises 20 connected to or in fluid communication with the injection nozzles 6 • · «| ... branch channels 25. In addition, the leak channel arrangement 24 comprises a manifold channel 26 connected to the branch channels 25, whereby the branch channel 25 receives • · 1:. leakage fuel flow is directed to manifold channel 26. Injection nozzle body 15 has a leakage outlet through which dirty leakage can be • ·. · 1 ·. 25 removes injection nozzle 6 and leads to branch channel 25. Branch channel 25 ·· · is in fluid communication with the leak outlet. The branch passage 25 is arranged in a bore in the cylinder head 13. The bore 35 into which the feed pipe 14 is arranged may also have access to the branch passage 25 such that the clearance 38 between the outer surface of the feed pipe 14 and the inner surface of the bore 35 acts as the branch passage 25.

• · • · · · 1 · · 6 ·

Fig. 3 shows in more detail the connection of the supply pipe 14 to the fuel injection nozzle 6 and the cylinder head 13. The supply pipe 14 comprises a first part 14a and a second part 14b arranged between the pressure accumulator 7, 8 and the cylinder head 13 and the injector nozzle 6. The first portion 14a is provided with double walls. The second portion 14b is a tube having a simple wall. Thus, the second portion 14b comprises a flow space for high pressure fuel only. The second portion 14b is provided in the bore 35 in the cylinder head 13. The bore 35 comprises two chambers 38, 39. The high pressure fuel 10 from the pressure accumulator 7, 8 is fed through the first tube 14a to the cylinder head 13 and further through the second tube 14b the first end 36a of the portion 14b is sealed to the first portion 14a. Any suitable fastening means 37, e.g. a sleeve having a threaded connection to the pipe end 36a, may be provided 15 to ensure a tight connection between the first part 14a and the second part 14b. The other end 36b of the second portion 14b is in direct contact with the injection nozzle 6 through the mutual contact surfaces 37a and 6a. Surface 6a may be conical and surface 37a is preferably spherical to provide a reliable and tight connection.

The cylinder head 13 has a first chamber 38 communicating with a leakage outlet through a second chamber 39. The second chamber 39 • · · ':' [· [has a smaller diameter than the first chamber 38. The arrangement comprises an additional fastening means 40, e.g. a sleeve or a corresponding bolt element through which · · · · · · · · . The second portion 14b is guided and threadedly connected to the first ·· ♦ chamber 38 in the cylinder head 13. The second portion 14b is provided with an expanded portion 14c having a counter surface 37b cooperating with the surface 40a of the fastening means 40. These surfaces 37b and 40a may be · · · conical. Alternatively, surface 37b, like surface 37a, may have a spherical shape · · 30, thereby better conforming to the possible deflection of second part 14b described below. Thus, the second portion 14b may be tightly sealed to the mating surface 40a of the fastening means 40 closer to the first end 36a of the second portion. The expanded part 14c need not be a structural part of the second part 14b, but may, if desired, be implemented as a separate threaded connection sleeve.

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As shown in Fig. 3, the portion of the second portion 14b which lies between the expanded portion 14c and the injection nozzle 6 is of significant length, particularly with respect to its diameter. When the second portion 14b has such a layout inside the second chamber 39, the advantage is a long elongation length that allows 10 loads to be held in spite of fuel temperature operating range values of 40 ° C to 150 ° C when using heavy fuel oil. If necessary, the second chamber 39 allows the second portion 14b to bend to such an extent that sufficient load stability can be maintained under various conditions. On the other hand, this portion of the second portion 14b may have a guide defining the limits of such deflection. In the figure this is only schematically shown in the form of a support element 41. Such a support element should, of course, be designed to allow leakage therethrough, thereby enabling the leakage flow through chambers 38 and 39 described below.

.. 20 The first chamber 38 communicates with the second chamber 39 · ·! . leakage outlet. Thus, the chambers 38, 39 serve as a branch passage • · · • · ·! V 25 and are used to eliminate the dirty leakage from the injection nozzle 6. The branch passage 25 comprises a passage 42 through which dirty • · · ”V leakage is discharged from the cylinder head 13.

• · · ··· 25 • · ·· ·

The leakage channel arrangement 24 is provided with a leak detector 28 for detecting fuel leaks. The leak detector 28 is coupled to the manifold channel 26 at a location through which all fuel from the branch passages 25 is arranged to flow. Because of the small amount of fuel leakage under normal injection nozzle operating conditions, it is desirable that only · higher fuel flow leaks are detected. Therefore, the leak detector 28 28 is arranged to detect only higher flows, i.e., leakage fuel flows whose flow exceeds a predetermined value. Leak detector 28 is unable to detect leakage fuel flows with a flow below a predetermined value.

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Figure 4 is a cross-sectional view of a leak detector 28 suitable for use in the fuel injection system of Figure 1. The collecting duct 26 is connected to the leakage inlet 30 in the detector 28. The leakage detector 28 comprises a control chamber 29 into which the leaking fuel 10 enters through the leakage inlet 30. At the bottom of the control chamber is an aperture 31 through which the fuel is drained from the control chamber 29. The aperture 31 is dimensioned such that leakage of the injector nozzles 6 under normal operating conditions is completely drained from the control chamber 29. When a larger 15 leakage fuel flow arrives at the control chamber 29, and as a result, the height of the fuel surface in the control chamber 29 rises. The control chamber 29 has a fuel level indicator device 32, e.g., a float or level indicator, that triggers an alarm or otherwise notifies when the fuel level in the control chamber 29 rises to 20 points, indicating a greater degree of dirty fuel leakage. one or more injection nozzles 6. Thus, the leak detector 28 is configured to detect only leakage fuel streams with a current of • · · | 1V exceeding a predetermined value. Due to the larger dirty fuel leakage from the injector nozzle 6, the corresponding cylinder 12 does not operate optimally • 1 ·, ···. The operating parameters of the cylinder 25 and the cylinder 12 are outside normal limits.

• · ·· ·

The leaking injector nozzle 6 may be located by an engine control system that monitors the operating parameters of the cylinders, e.g., cylinder pressure or. ·· 1; exhaust temperature. At the top of the control chamber 29 is a leakage outlet · · · #t V 33 through which excess fuel is discharged.

• · 30 From the leak detector 28, fuel is led to fuel tank 2.

Under normal operating conditions of the spray nozzles 6, the branch and manifold channels 25, 26 and the control chamber 29 of the 9 leakage channel arrangements 24 are depressurized (i.e., at atmospheric pressure).

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Claims (10)

A common rail-based fuel injection system (1) for a multi-cylinder piston engine, comprising fuel injection system (1) - at least one pressurized fuel accumulator (7, 8,18), - injectors (6) for injecting pressurized fuel into the cylinders (12), which injectors (6) are connected to the pressure accumulator (s) (7, 8), from which pressure accumulator (s) (7, 8) through double-wall feeder (14) measure fuel for the injectors (6) ), which have double walls internal flow space supply ducts (14) for pressurized fuel and their outer flow space acts as a collection channel for possible leakage fuel, and - a leakage channel arrangement (24) for removing fuel leaking from injectors (6) ), characterized in that the leakage channel arrangement (24) comprises branch channels (25) connected to the injectors (6) and a collection channel (26) arranged in flow communication with the branch the leakage stream from the branch ducts (25) can be collected in the junction channel (26), which leakage channel arrangement (24) is provided with a leak detector connected to the junction channel (26) for detecting a fuel leak. • · • M • «• · · • · · ΓΥ Fuel injection system according to claim 1, characterized in that the leak detector tower (28) is arranged to detect only such leakage fuel streams whose flow exceeds a predetermined value. • · · · · · · · 3. Fuel injection system according to claim 1 or 2, characterized in that ..... the fuel injection from the injector (6) is controlled by the fuel pressure in the injector (6) • · control chamber (20). · · · · · · · Fuel injection system according to claim 3, characterized in that a return pipe (21) through which the fuel is removed from the control chamber ..f: * (20) is connected to the injector. · · · · · · · · · · 5. Fuel injection system according to any of the preceding claims, characterized in that the injector (6) comprises an injector pressure accumulator (18) for the fuel being injected. Fuel injection system according to any of the preceding claims, characterized in that the injectors (6) are connected to the pressure accumulator (s) (7, 8) by means of feeding pipes (14), which pipes are arranged in drill heels (35) in the cylinder. the lid (13). Fuel injection system according to claim 6, characterized in that the clearance (38, 39) between the feeder tube (14) and the drill hole (35) forms part of the leakage channel arrangement (24). Fuel injection system according to any one of the preceding claims, characterized in that the channels (25, 26) in the channel arrangement (24) are pressure-free. Fuel injection system according to any of the preceding claims, characterized in that the leak detector (28) comprises a leaking fuel control chamber (29) and an opening (31) through which fuel can be removed from the control chamber (29), which opening is so dimensioned that from the control chamber (29) a • · [can be removed. leaked fuel quantity that arises during the normal operating conditions of the injectors (6) • · · in * Y countries 10. Fuel injection system according to some of the preceding claims, characterized by the fact that the control chamber is equipped with a fuel level detector (32). ). · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·