CN111502879A

CN111502879A - Dual-substance injector

Info

Publication number: CN111502879A
Application number: CN202010078353.9A
Authority: CN
Inventors: D·布拉特雷尔; R·米特; T·屈格勒
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-01-31
Filing date: 2020-02-03
Publication date: 2020-08-07
Also published as: DE102019219441A1

Abstract

The invention relates to a two-substance injector for injecting two different media, comprising two coaxially arranged nozzle needles (1,2) guided one inside the other for releasing and closing injection openings (3,4), wherein each nozzle needle (1,2) is assigned a control chamber (5,6) that can be charged with a control medium and that can be discharged as a function of a switching position of a control valve (7,8) such that a control pressure acting on the nozzle needle (1,2) can be varied in order to actuate the respective nozzle needle (1, 2). According to the invention, a pressure increasing device (10) is arranged in the inlet path (9) of the first medium, so that the pressure in the inlet path (9) of the first medium can be increased.

Description

Dual-substance injector

Technical Field

The invention relates to a dual substance injector. By means of the two-substance injector, two different media, for example liquid and gaseous fuels or fuel and water, can be injected separately from one another. In the case of the exemplary named, injection takes place into a combustion chamber of the internal combustion engine or into an intake system arranged upstream of the combustion chamber. For this purpose, the two-substance injector has two coaxially arranged nozzle needles guided in a nested manner with respect to one another for releasing and closing the injection opening.

Background

A two-substance injector of the type described above is known for example from the publication DE 102016221543 a 1. Injectors are known for injecting gaseous and/or liquid fuel into the combustion chamber of an internal combustion engine. The injector includes a first valve mechanism reciprocally received in the central bore of the nozzle body and a second valve mechanism reciprocally received in the central bore of the first valve mechanism. Each valve mechanism is assigned a control chamber which can be supplied with liquid fuel via an inlet throttle and can be discharged via a valve. In order to simplify the construction of the injector, the two valves are connected in series and can be actuated by means of a common actuator. The one actuator reduces the number of components and thus the manufacturing or assembly effort. The series connection of the two valves also ensures that the two valve mechanisms of the injector can be opened offset in time from one another in order to be able to carry out a pilot injection (pilotinsprivung) with liquid fuel and then a main injection with gaseous fuel.

Based on the prior art described above, a dual substance injector for a medium supply system, in particular a fuel supply system, is to be provided, which can reduce the complexity of the system configuration. This relates in particular to a fuel supply system for supplying an internal combustion engine with gaseous fuel. In such systems, the complexity is also related to the gas pressure, since high gas pressures affect the thermal equilibrium. Therefore, a low gas pressure is desirable in this viewpoint. However, high gas pressures are required for injection.

Disclosure of Invention

The object of the invention is therefore to resolve the conflict between the above-mentioned objects.

To solve this object, a two-substance injector is proposed according to the invention. Advantageous embodiments of the invention are known from the preferred embodiments.

The two-substance injector proposed for injecting two different media comprises two coaxially arranged nozzle needles guided in a nested manner for releasing and closing the injection opening. In this case, each nozzle needle is assigned a control chamber which can be charged with a control medium and which can be relieved as a function of the switching position of the control valve, so that the control pressure acting on the nozzle needle can be varied in order to actuate the respective nozzle needle. According to the invention, a pressure intensifying device is arranged in the inlet path of the first medium, so that the pressure in the inlet path of the first medium can be increased.

The system pressure can be reduced by a pressure increase inside or in the vicinity of the ejector, so that a less complex system configuration can be selected. This applies in particular when the system is a fuel supply system for gaseous fuels (e.g. natural gas) and liquid fuels. For example, the system may be an NGDI system, where "NGDI" stands for "direct injection of natural gas".

In an NGDI system, the system pressure or gas pressure required for injection/blowing is typically 500 bar. If the pressure is to be provided on the system side, the high gas pressure affects the system configuration, since all components have to be designed for the high gas pressure. Furthermore, the requirements for the thermal balance of the system increase as the gas pressure increases.

If a two-substance injector according to the invention is used in such a system, the gas pressure in the system can be kept low and only raised to the desired value in or near the injector. Accordingly, the complexity of the fuel supply system is reduced. In this case, the first medium is a gaseous fuel or natural gas.

However, the dual substance injector of the present invention is not limited to application as an NGDI injector or as a dual fuel injector. The two-substance injector can also be used in other supply systems for supplying or injecting two different media. As another application example, injection of fuel and water may be cited, for example. The fuel, in particular the gaseous fuel, may also be hydrogen, for example.

The pressure boosting device of the proposed two-substance injector preferably comprises an intensifier chamber arranged in the inlet path of the first medium and a piston delimiting the intensifier chamber, so that the volume of the intensifier chamber is variable by the axial position of the piston. If the piston sinks deeper into the intensifier chamber, its volume decreases, which results in an increase in pressure in the intensifier chamber. In this way, the pressure in the supply path of the first medium can be increased.

The supply path for the first medium comprises sections which are located inside and outside the injector, so that the pressure boosting device can also be arranged inside or outside the injector. The preferred arrangement is particularly relevant in relation to the corresponding installation space. The pressure intensifying means may also be arranged outside the injector if the installation space in the injector for receiving the pressure intensifying means is not sufficient. In this case, the arrangement is preferably carried out in the vicinity of the injector in order to avoid possible pressure losses on the way to the injector.

In the case of an arrangement of the pressure intensifying means inside the injector, the piston is advantageously arranged in such a way that it moves parallel to the longitudinal axis a of the two-substance injector, i.e. parallel to the direction of movement of the two nozzle needles. The piston can be arranged coaxially with respect to the two nozzle needles, for example. In the case of a supercharging device arranged outside the injector in the vicinity of the injector, the piston can be oriented arbitrarily.

It is furthermore proposed that the piston of the charging device delimits, at its end facing away from the intensifier chamber, a pressure chamber which can be charged with a pressure medium, preferably a control medium. Thus, the pressure in the pressure chamber may vary and may be used to operate the piston. Thus, the axial position of the piston can be changed in accordance with the pressure in the pressure chamber.

In one embodiment of the invention, it is provided that the piston is embodied as a stepped piston. That is, the piston comprises sections with different diameters or piston cross sections, so that the pressure increase ratio of the pressure increasing device can be adjusted by the area ratio of the corresponding piston cross sections

In this way, the supercharging can be further increased, whereby the efficiency of the supercharging device is increased.

According to a preferred embodiment of the invention, the piston of the charging device has a first section which delimits the intensifier chamber and a second section which delimits the pressure chamber and has an increased diameter compared to the first section, so that an annular shoulder which delimits the further pressure chamber is formed. The pressure in the other pressure chamber causes a pressure acting on the piston, which acts against the adjusting force in the first pressure chamber. The movement of the piston or the actuation of the pressure intensifier can thus be controlled by the pressure difference between the two pressure chambers.

Preferably, the further pressure chamber can be supplied with control medium via the inlet throttle and can be relieved via the outlet throttle as a function of the switching position of the control valve. The coordination of the throttle devices is preferably selected such that the control medium flowing into the further pressure chamber is replenished via the continuously open inlet throttle device compared to the control medium flowing out of the further pressure chamber via the outlet throttle device when the control valve is open. The pressure in the other pressure chamber then drops to such an extent that a resultant force acts on the piston, which causes the piston to sink deeper into the intensifier chamber. The actuation of the charging device can thus be controlled in a simple manner by the pressure acting on both sides of the piston, respectively.

In order to charge the two pressure chambers with the control medium, the two pressure chambers are connected to an input for the control medium. The same pressure prevails in both pressure chambers if the control valve controlling the pressure in the other pressure chamber remains closed. Thus, with the control valve closed, the piston is substantially pressure balanced.

Advantageously, the piston of the charging device is supported on a return spring. The return spring facilitates the return of the piston to its initial position. This is advantageous in particular when the piston is pressure-balanced. The return spring is preferably designed as a compression spring and is received in the further pressure chamber.

As an extension, it is provided that a further pressure chamber of the pressure intensifier is connected to the control chamber via a connecting channel for controlling the reciprocating movement of the first nozzle needle. This configuration has the following advantages: the control pressure in the control chamber can be controlled by means of the first nozzle needle, while the pressure in the other pressure chamber of the pressure intensifier can be controlled by means of a common control valve. The structure of the two-substance injector is correspondingly simplified.

In order to prevent the medium from being sucked back out of the region of the supply path arranged further downstream when the piston of the charging device is reset and when the volume of the intensifier chamber increases, it is proposed that a non-return valve be arranged in the supply path of the first medium, in particular upstream of the charging device, which non-return valve is closed off against the supply direction.

According to an alternative preferred embodiment of the invention, the piston of the charging device has a first section which delimits the intensifier chamber and a second section which delimits the pressure chamber and has a reduced diameter compared to the first section, so that an annular shoulder is formed which delimits the further pressure chamber. In contrast to the previous embodiment, the pressure in the other pressure chamber does not counteract the adjusting force in the first pressure chamber, but constitutes a pressure equalizing volume. For this purpose, the further pressure chamber is preferably connected to a return for the control medium, so that a return pressure acts in the further pressure chamber. If diesel fuel is used as the control medium, the reflux pressure is typically not greater than 10 bar. The actuation of the piston is therefore controlled by the pressure in the first pressure chamber or by the pressure difference between the pressure in the first pressure chamber and the pressure in the intensifier chamber. In order to compress the first medium present in the intensifier chamber, the pressure in the first pressure chamber is increased, so that the piston of the pressure boosting device sinks deeper into the intensifier chamber. In order to increase the pressure in the first pressure chamber, the first pressure chamber is charged with a control medium, preferably the same control medium which also controls the reciprocating movement of the nozzle needle.

The input into the first pressure chamber is preferably controlled by means of a control valve and/or an input throttle. The unloading of the first pressure chamber can be brought about by the discharge throttle and/or the control valve. In this case, only one control valve is required, by means of which either the supply into the first pressure chamber or the discharge from the first pressure chamber can be blocked. In particular, a two-position three-way reversing valve or a three-position three-way reversing valve is suitable as a control valve. The two-position three-way directional valve makes it possible to arrange the pressure boosting device outside the injector. The three-position three-way reversing valve has the following advantages: depending on the connection arrangement with the control chamber formed in the injector, the number of control valves can be reduced overall.

The shoulder formed on the piston of the charging device can at the same time form a control edge which releases or closes the discharge path as a function of the axial position of the piston. The relief path serves to relieve the control chamber associated with the first nozzle needle, so that the control chamber is relieved more quickly and the first nozzle needle opens more quickly. The connection of the control chamber to the unloading path is preferably effected by means of a discharge throttle assigned to the control chamber.

Drawings

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The figures show:

FIG. 1 is a schematic longitudinal sectional view of a two-substance injector according to a first preferred embodiment,

figure 2 is a schematic longitudinal section of a two substance injector according to a second preferred embodiment,

figure 3 is a schematic longitudinal section of a two-substance injector according to a third preferred embodiment in connection with an injection system,

FIG. 4 is a schematic longitudinal sectional view of a two substance injector according to a fourth preferred embodiment,

FIG. 5 is a schematic longitudinal sectional view of a two substance injector according to a fifth preferred embodiment,

FIG. 6 is a schematic longitudinal sectional view of a two substance injector according to a sixth preferred embodiment,

FIG. 7 is a schematic longitudinal sectional view of a two-substance injector according to a seventh preferred embodiment and

fig. 8 is a schematic illustration of a pressure curve and a needle stroke curve.

Detailed Description

From the schematic of fig. 1, a dual mass eductor according to the present invention is known, which may be used, for example, as an NGDI eductor. The two-substance injector has a nozzle body 23, in which two coaxially arranged nozzle needles 1,2 guided one inside the other are received. The outer nozzle needle 1 controls a first injection opening 3, via which a first medium, for example natural gas, can be injected or blown in. The first nozzle needle 1 is embodied as a hollow needle. The inner nozzle needle 2 controls a second injection opening 4 via which a second medium, for example diesel fuel, can be injected. The inner nozzle needle 2 is received in the outer nozzle needle 1 while constituting an input path 24 for the second medium. The outer nozzle needle 1 and the nozzle body 23 together delimit the supply path 9 for the first medium.

In an NGDI injector, first the inner nozzle needle 2 is opened for diesel pilot injection via the injection opening 4, by means of which the gaseous fuel subsequently injected via the injection opening 3 can be ignited.

To open the inner-nozzle needle 2, the control pressure in the cylindrical control chamber 6 above the inner-nozzle needle 2 is reduced by means of the control valve 8, so that the inner-nozzle needle 2 can open as the control pressure in the control chamber 6 decreases. With the control valve 8 open, the control medium present in the control chamber 6 (wherein the present control medium is the second medium) flows out via the outlet throttle 22, while the medium is fed in via the inlet throttle 21. However, the input amount is smaller than the outflow amount, so that the control pressure in the control chamber 6 drops and the inner nozzle needle 2 moves upward.

In order to open the outer nozzle needle 1, the control pressure in the annular control chamber 5 above the outer nozzle needle 1 is reduced by means of a further control valve (not shown). As the control pressure in the control chamber 5 drops, the outer nozzle needle 1 can open.

In order to close the two

nozzle needles

1,2, the control pressure in the

respective control chamber

5,6 is raised again by closing the control valve.

In order to increase the pressure of the first medium, the two-substance injector according to the invention shown in fig. 1 has a pressure intensifier device 10, which comprises an intensifier chamber 11 arranged in the inlet path 9 and a piston 12 delimiting the intensifier chamber 11. Thus, the input path 9 for the first medium extends via the amplifier chamber 11. The piston 12 is currently implemented as a stepped piston. A first section 12.1, which has a reduced diameter or reduced cross section compared to a second section 12.2, which delimits a pressure chamber 13 arranged above the piston 12, serves to delimit the intensifier chamber 11. The piston 12 thus forms an annular shoulder 14 which delimits a further pressure chamber 15 on the side of the section 12.2 facing away from the pressure chamber 13. The two

pressure chambers

13, 15 are each connected to an inlet path 24 for a second medium, which is currently simultaneously used as a control medium. In contrast to the first pressure chamber 13, the further pressure chamber 15 is connected via an inlet throttle 16, so that the inlet is throttled. The control pressure in the further pressure chamber 15 can be varied by means of a discharge throttle 17 which can be switched on and off by means of the control valve 7 in such a way that the resultant pressure acts on the piston 12, which moves the piston 12 downward, so that it sinks deeper into the intensifier chamber 11. In this case, the piston 12 reduces the volume of the intensifier chamber 11, so that the pressure in the intensifier chamber 11 or in the supply path 9 of the first medium rises. In this way, a pressure increase inside the injector is caused in the inlet path 9 of the first medium. Thus, the input pressure of the first medium outside the eductor may be reduced, which has the advantage of reducing the complexity of the system configuration, for example in an NGDI eductor. Furthermore, the pressure increase inside the injector has a positive influence on the heat balance of the system.

The movement of the piston 12 is caused against the spring force of a pressure spring acting as a return spring 18. Thus, when the control valve 7 is closed and the pressure in the further pressure chamber 15 rises again, the pressure spring supports the return of the piston 12. With the closing of the control valve 7, the control medium can therefore no longer flow out of the further pressure chamber 15 via the outlet throttle 22, but can only flow in via the inlet throttle 21. As a result, the piston 12 moves upward again, wherein it is withdrawn from the intensifier chamber 11, so that the volume of the intensifier chamber 11 increases again. In order to prevent a portion of the first medium present in the feed path 9 from being sucked back in here, a check valve 20 is arranged in the feed path 9 upstream of the intensifier chamber 11.

Fig. 2 shows a development of the two-substance injector of fig. 1. Since the two-substance injector of fig. 2 additionally has a connecting channel 19 which connects the further pressure chamber 15 of the pressure intensifier 10 with the annular control chamber 5 above the outer nozzle needle 1, the control valve 7 can be used not only for actuating the pressure intensifier but also for controlling the reciprocating movement of the outer nozzle needle 1. In this way the complexity of the two-substance injector can be reduced.

Another preferred embodiment of the dual substance injector of the present invention is shown in fig. 3 in conjunction with an injection system. A first medium (for example natural gas or hydrogen) and a second medium (for example diesel fuel) can be injected by means of the two-substance injector shown. The second medium is currently simultaneously used as a control medium which controls the reciprocating movement of two nozzle needles of the two-substance injector which are guided one inside the other.

The first medium is stored in at least one tank 25 and supplied to the two-substance injector via the inlet path 9. The feed path 9 is guided via an intensifier chamber 11 of a pressure intensifying device 10, which is arranged in fig. 3 close to the injector (not internally in the injector). Depending on the kind of medium and/or the type of storage, different requirements are placed on the tank 25.

In the case of i. a tank 25 is shown, said tank containing a carrier liquid

In the downstream connected dehydrogenation unit 26, the Hydrogen bound in the Carrier liquid is released by means of heat (W) and brought to a pressure level of about 10 to 50bar by means of the low-pressure compression device 27, before the Hydrogen is introduced into the feed path 9.

In the case of ii, a cryogenic tank 25' is shown for storing cryogenic fuel, for example hydrogen or methane or liquefied Natural Gas (L NG ═ L Natural Gas.). the temperature of the hydrogen is approximately-250 ℃ and the temperature of the methane is approximately-160 ℃.

In the case of iii, a high-pressure tank 25 "is shown, in which fuel under pressure is stored. The fuel can again be hydrogen, methane or Natural Gas (CNG ═ Compressed Natural Gas: Compressed Natural Gas). The operating pressure is between 200 and 300 bar.

The second medium (in the present case diesel fuel) is stored in a tank 30 and compressed by means of a high-pressure pump 31 and supplied to a high-pressure accumulator 32 or Rail (Rail). The dual substance injector is supplied with diesel fuel through a high pressure reservoir 32. As shown in fig. 3, in addition to the two-substance injector shown, other two-substance injectors may be connected to the high-pressure accumulator 32.

The diesel fuel supplied to the two-substance injector serves as ignition fuel and control medium. Thus, both

control chambers

5,6 of the dual fuel can be loaded with diesel fuel. The input is performed by means of the

input throttle

21, 33, respectively. Depending on the switching position of the control valves 7,8, the

control chambers

5,6 are relieved of pressure by the

outlet throttle

22, 34, respectively. Furthermore, diesel fuel is used to control the supercharging device 10. For this purpose, the pressure chamber 13 arranged on the end side with respect to the piston 12 is charged with diesel fuel depending on the switching position of the further control valve 35, so that the piston 12 is charged with diesel pressure. This diesel pressure is higher than the pressure in the intensifier chamber 11, so that a hydraulic pressure acts on the piston 12, which presses the piston 12 downward against the spring force of the return spring 18. Here, the piston 12 sinks deeper into the intensifier chamber 11, so that the volume of the intensifier chamber is reduced and the first medium received therein is compressed. A first check valve 20 arranged upstream of the pressure boosting device 10 in the inlet path 9 may enable a pressure build-up in the intensifier chamber 11. Subsequently, the compressed medium is supplied to the two-substance injector via a second non-return valve 36 arranged downstream of the pressure boosting device 10 in the inlet path 9. For unloading the pressure chamber 13, a discharge throttle 17 is provided, via which the pressure chamber 13 is connected to a return 37, which leads back into the tank 30.

The piston 12 of the charging device 10 of fig. 3 is embodied as a stepped piston, so that the piston 12 has a first piston section 12.1 and a second piston section 12.2. In fig. 3, the diameter of the second piston section 12.2 is selected to be smaller than the diameter of the first piston section 12.1. A further pressure chamber 15, which is likewise connected to the return 37, is delimited by a shoulder 14 formed on the piston 12, so that a return pressure acts in the pressure chamber 15.

Fig. 4 shows a variant of the embodiment shown in fig. 3. Here, the control valve 35 is not configured as a two-position three-way directional valve, but as a three-position three-way directional valve. This makes it possible to dispense with the control valve 8 for unloading the control chamber 6 above the inner nozzle needle 2. The control valve 35 is designed in such a way that in the initial position the discharge from the pressure chamber 13 via the discharge throttle 17 is open, while the input into the pressure chamber 13 is closed. The outer nozzle needle 1 is also actuated by means of a control valve 7.

Fig. 5 shows a further variant. In this embodiment, the control valve 35 replaces the two control valves 7,8, so that the number of valves is further reduced. However, this requires the arrangement of the supercharging device 10 inside the injector, since otherwise an additional pressure line would be required.

Fig. 6 shows a variant of the embodiment of fig. 5. In this case, the piston 12 of the charging device 10 simultaneously forms a control edge 38 in the region of the shoulder 14, which, depending on the axial position of the piston 12, releases an unloading path 39, which is connected to the control chamber 5 via the outlet throttle 34.

Another preferred embodiment is shown in fig. 7. The outer nozzle needle 1 is controlled here solely by the applied pressure. As soon as a corresponding pressure builds up in the control chamber 5, the nozzle needle 1 opens against the spring force of the spring 40 and/or against the hydraulic pressure. In the case of opening against hydraulic pressure, the hydraulic and pneumatic active surfaces present on the nozzle needle 1 must be coordinated with one another in accordance with the pressure relationship.

Fig. 8 shows an exemplary pressure curve and needle travel curve for the embodiment according to fig. 4. The uppermost diagram shows the pressure profile in the charging device 10, curve K1 indicating the course of the pressure p in the pressure chamber 13 over time t and curve K2 indicating the course of the pressure p in the intensifier chamber 11 over time t.

The curve K3 in the table below illustrates the input pressure of the diesel fuel, and the curve K4 illustrates the input pressure of the first medium in the inlet path 9. The stroke h of the two

nozzle needles

1,2 is shown in the graph below it, wherein the curve K5 describes the stroke h of the inner nozzle needle 2 and the curve K6 describes the temporally offset stroke h of the outer nozzle needle 1. Curves K7 through K9 illustrate the valve strokes of the

control valves

7,8, and 35.

The lowermost diagram shows the injection rate (einsipritzrate), wherein curve K10 shows the diesel injection rate and curve K11 shows the injection rate of the first medium or of the main fuel.

Claims

1. A two-substance injector for injecting two different media, comprising two coaxially arranged nozzle needles (1,2) guided one inside the other for releasing and closing injection openings (3,4), wherein each nozzle needle (1,2) is assigned a control chamber (5,6) which can be charged with a control medium and which can be discharged as a function of the switching position of a control valve (7,8) in such a way that a control pressure acting on the nozzle needle (1,2) can be varied in order to actuate the respective nozzle needle (1,2), characterized in that a pressure boosting device (10) is arranged in the inlet path (9) of the first medium in such a way that the pressure in the inlet path (9) of the first medium can be increased.

2. The two-substance injector according to claim 1, characterized in that the pressure boosting device (10) comprises an intensifier chamber (11) arranged in the input path (9) and a piston (12) delimiting the intensifier chamber (11), such that the volume of the intensifier chamber (11) can be changed by the axial position of the piston (12).

3. The two-substance injector according to claim 2, characterized in that the piston (12) delimits, on its end facing away from the intensifier chamber (11), a pressure chamber (13) which can be charged with a pressure medium, preferably the control medium.

4. The dual substance injector according to claim 2 or 3, characterized in that the piston (12) is embodied as a stepped piston.

5. The two-substance injector according to claim 4, characterized in that the piston (12) has a first section (12.1) which delimits the intensifier chamber (11) and a second section (12.2) which delimits the pressure chamber (13) and has an increased diameter compared to the first section (12.1) such that an annular shoulder (14) is formed which delimits a further pressure chamber (15).

6. Dual substance injector according to claim 5, characterized in that the further pressure chamber (15) can be charged with the control medium by an input throttle (16) and can be discharged by an outlet throttle (17) depending on the switching state of the control valve (7).

7. The dual substance injector according to one of claims 2 to 6, characterized in that the piston (12) is substantially pressure-balanced with the control valve (7) closed.

8. The dual substance injector according to one of claims 2 to 7, characterized in that the piston (12) is supported on a return spring (18), which is preferably configured as a pressure spring and is received in the further pressure chamber (15).

9. The two-substance injector according to one of claims 5 to 8, characterized in that the further pressure chamber (15) is connected to the control chamber (5) by a connecting channel (19) for controlling the reciprocating movement of the first nozzle needle (1).

10. Two-substance injector according to one of the preceding claims, characterized in that in the inlet path (9) of the first medium, upstream of the pressure boosting device (10), a non-return valve (20) is arranged, which is shut off against the inlet direction.