DE102018215891A1 - Device for metering a gaseous and a liquid fuel and a method for operating this device - Google Patents

Abstract

Device for metering a gaseous and a liquid fuel with an injector (1), which is designed to meter a gaseous fuel under a working pressure, and with a supply line (2) for supplying gaseous fuel to the injector (1), wherein An atomizer unit (8) is provided in the supply line (2), via which a lubricating liquid can be introduced in an atomized manner into the supply line (2) for the gaseous fuel.

Description

The invention relates to a device for metering a gaseous and a liquid fuel, as used, for example, to introduce gaseous and liquid fuels into a combustion chamber of an internal combustion engine. In addition, the invention relates to a method for operating this device.

State of the art

Devices are known from the prior art with which liquid and gaseous fuels can be introduced into a combustion chamber of an internal combustion engine. In particular, injectors are used for this purpose, which can inject or inject both gaseous and liquid fuel under a specific high pressure into a combustion chamber of an internal combustion engine. The liquid fuel is atomized and serves either as the sole fuel if gaseous fuel is not available or as an ignition quantity to initiate combustion in the combustion chamber so that the gaseous fuel burns optimally. Such a device is for example from the DE 10 2016 271 009 A1 known. The injector used in the device has an outer and an inner nozzle needle, the outer nozzle needle controlling an inflow cross section for metering the gaseous fuel. The inner nozzle needle arranged in the outer nozzle needle interacts with a nozzle seat and serves to open and close injection openings via which the liquid fuel is metered in. The control of both nozzle needles is servo-hydraulic, which means that both nozzle needles experience a closing force due to the pressure in a control chamber that is filled with the liquid fuel, which is directed towards the respective nozzle seat.

If an injection or injection is to take place, the pressure in the control rooms is reduced and the nozzle needles lift off the nozzle seats and expose the injection openings or the injection openings.

Both gaseous and liquid fuel are therefore present within the injector at a high pressure of, for example, approximately 500 bar (50 MPa). However, the fuels should not mix within the injector, which is why sealing measures are required. A complete seal between the gas and liquid-carrying areas of the injector is difficult to achieve, because of the design, throttle gaps between these areas cannot be completely avoided. A slight admixture of liquid fuel to the gaseous fuel is not necessarily disadvantageous, that is, if liquid fuel gets into the area of the injector filled with gas as long as a certain amount is not exceeded. It is even desirable for wear on the nozzle seat of the outer nozzle needle, since the liquid fuel - for example diesel fuel - has a lubricating effect here. In addition, the liquid fuel creates an additional seal on the nozzle seat, which cannot be provided with an elastomer seal due to the high temperatures and is therefore not completely gas-tight without the liquid film.

However, the exact metering of the liquid fuel that is to enter the gas range is difficult. The amount of liquid fuel that reaches the nozzle seat through the throttle gap depends on the pressure difference and the size of the throttle gap and also on other parameters, such as the temperature. Functional impairments can also occur if only liquid fuel is sprayed out over a long period of time, the outer nozzle needle, which controls the gaseous fuel, remains closed and only the inner nozzle needle opens and closes. The amount of liquid entering then collects in the gas area of the injector, which leads to difficulties when restarting the gas injection, since a larger amount of liquid suddenly enters the combustion chamber with the gas flow and there leads to unpredictable combustion conditions.

It is therefore generally advantageous if measures are taken in the injector which lead to a complete separation of gaseous and liquid fuel. This can be done, for example, by using suitable seals, for example corrugated bellows, or by directly actuating the nozzle needles, so that there are no control rooms that can be filled with liquid fuel. In the case of such injectors, however, there is no lubricating liquid film in the gas system due to the concept, so that leaks and increased wear on the gas valve seat can occur.

The liquid and the gaseous fuel can also be metered by two separate injectors, which are either completely separate or in which both metering devices are accommodated in the same housing. In these systems too, lubrication of the sealing seat of the injector for the gaseous fuel is advantageous for the reasons mentioned above.

Advantages of the invention

The inventive device for metering a liquid and a gaseous In contrast, fuel has the advantage that there is reduced wear and a good seal in the gas-carrying area of the injector, regardless of the principle of the nozzle needle control. For this purpose, the device for metering a gaseous and a liquid fuel has an injector which is designed to meter a liquid and gaseous fuel under a respective working pressure. Furthermore, a supply line for supplying gaseous fuel to the injector is provided, wherein an atomizer unit is provided in the supply line, via which a lubricating liquid can be atomized into the supply line for the gaseous fuel.

By feeding the lubricant into the gas stream, a fine film of lubricant is deposited on the surfaces of the feed line and the injector and thus also on the sealing seat of the sealing element, which controls the feed of the gaseous fuel in the injector. This results in sufficient lubrication of the sealing seat, regardless of how the sealing element is moved. The wear caused by an unlubricated nozzle seat and the sealing problems at this point can thus be avoided.

In a first advantageous embodiment, the injector has a longitudinally movable nozzle needle which interacts with a nozzle seat for opening and closing a flow cross-section through which the gaseous fuel can be metered. By wetting with the lubricant of the nozzle seat, the advantages already mentioned occur.

In a further advantageous embodiment, the supply line has a high-pressure gas space, a connecting line leading from the high-pressure gas space to the injector and a high-pressure line, via which the high-pressure gas space can be filled with gaseous fuel under high pressure, the atomizer unit being arranged in the high-pressure line. As a result of the arrangement of the atomizer unit in the high-pressure line, the atomized lubricant is already fed in before the high-pressure gas space, so that all surfaces downstream of the atomizer unit are wetted with the lubricant. In particular, it offers the advantage that the entire structure, in particular the high-pressure gas space, does not have to be changed compared to the already known metering systems.

In a further advantageous embodiment, the atomizer unit is controlled by an electrical control device. This allows the lubricant to be atomized to be dosed precisely in the desired quantity and at the right time.

In a further advantageous embodiment, a plurality of injectors for metering the liquid and gaseous fuel are connected to the high-pressure gas space via a connecting line in each case. As a result of the arrangement of the atomizer unit in the high-pressure line in front of the high-pressure gas space, all the injectors and thus all the valve seats of these injectors are wetted with the lubricant, so that all injectors have the corresponding advantages.

In a further advantageous embodiment of the device, a high-pressure fuel collecting space is present, in which compressed, liquid fuel is held under high pressure and from which an inlet line leads to the injector. In particular, if a fuel is metered by the injector that has lubricating properties, such as diesel fuel, this can also be used to wet the nozzle seat of the injector. Since the fuel is already present in the system under high pressure, it can easily be supplied to the metering unit from the high-pressure fuel collecting space via a connecting line. The high pressure fuel plenum also provides the pressure required to atomize the liquid fuel.

In a method according to the invention for operating a device for metering a gaseous and a liquid fuel with an injector, which is designed to meter a gaseous fuel under a working pressure, it is provided that an atomizer unit in a supply line for supplying the gaseous fuel to the injector is arranged, through which a lubricant is introduced atomized. This lubricating liquid is preferably liquid fuel which lubricates the valve seat of the gaseous part of the injector. This liquid fuel is preferably the same fuel that is dosed via the injector. The lubricating liquid is advantageously introduced into the supply line only when gaseous fuel is metered in via the injector. If the injector works in a mode in which only liquid fuel is metered, the valve seat of the corresponding nozzle needle does not need to be wetted further with a lubricant, so that there is no metering in via the atomizer unit during this time.

The atomizer unit is preferably controlled by means of an electrical control valve, the lubricating liquid being introduced by the control device only at predetermined operating points of an internal combustion engine into which the injector injects or injects the fuels. When metering in the lubricant, it is particularly important to ensure that not too much of it gets into the areas of the injector where gas is metered, as this can otherwise lead to malfunctions. About coordinating with the operating points of the For example, some internal combustion engine can be introduced with a little lubricating fluid shortly after the internal combustion engine starts, while only a little additional lubricating fluid is metered into the intake tract of the gaseous fuel during operation.

Figure list

• In the drawing, an embodiment of the device according to the invention is shown. It shows
  • 1 1 shows a schematic representation of the entire device, only the essential components being shown,
  • 2nd a longitudinal section through an injector, as in the device 1 Is used,
  • 3rd an enlargement of the section of III 2nd and
  • 4th a further enlargement of the section of IV 2nd .

Description of the embodiments

In 1 A device for metering liquid and gaseous fuel, for example into a combustion chamber of an internal combustion engine, is shown schematically. For this purpose, the device has a large number of injectors 1 on, which are designed to meter the liquid and gaseous fuel. Each of the injectors 1 is via a connecting line 6 with a high pressure gas space 10th connected, which is filled with gaseous fuel under a high pressure of, for example, 500 bar (50 MPa). The high pressure gas space 10th is via a high pressure line 4th filled with the pressurized gas, the high pressure line 4th , the high pressure gas space 10th and the connecting lines 6 together a supply line 2nd form. Each of the injectors 1 is also via an inlet pipe 7 with a fuel high pressure plenum 11 connected, in which liquid fuel is held under high pressure, preferably also under about 500 bar. The fuel high-pressure plenum 11 becomes from a tank 12th filled, the liquid fuel via a high pressure pump 13 compressed and further the fuel high-pressure plenum 11 is fed.

The high pressure line 4th shows an enlarged section in this illustration 9 on in which an atomizer unit 8th protrudes. The atomizer unit 8th For example, an injection valve is designed and designed to atomize a lubricant under a relatively high pressure of, for example, also approximately 500 bar, so that droplets of lubricant enter the high-pressure line 4th can be brought in. This lubricant or the atomized lubricant is caused by the gas flow within the high pressure line 4th entrained, enters the high pressure gas space 10th and over the connecting lines 6 into the injectors 1 . The atomizer unit 8th is via an electrical control unit 15 controlled via a connecting cable 16 with the atomizer unit 8th connected is. In the in 1 The embodiment shown is used as the lubricating fluid of the fuel, which is also via the injectors 1 is dosed. This is the fuel high-pressure plenum 11 over a line 5 with the dosing unit 8th connected so that liquid fuel under pressure from the metering unit 8th fed and via the atomizer unit 8th into the high pressure line 4th is introduced.

The injectors 1 are designed to meter both liquid and gaseous fuel. The gaseous fuel is in the form of a gas jet 18th or a variety of gas jets 18th ejected, as well as the liquid fuel, the liquid jets 19th forms. In 2nd Such an injector is shown enlarged in longitudinal section, only the essential parts being shown. The injector 1 has a nozzle body 20th on where a hole 21 is graduated. The nozzle body 20th is with a holding body 22 connected, which is not shown in the drawing, so that the holding body 22 and the nozzle body 20th are connected to each other in a liquid and gas tight manner. In the hole 21 is an outer nozzle needle 23 arranged longitudinally displaceable. The outer nozzle needle 23 has a conical sealing surface at its combustion chamber end 24th with which they also have a conical outer nozzle seat 26 interacts to open and close a flow cross section for the gaseous fuel. The gaseous fuel passes through a feed hole 29 that are inside the nozzle body 20th is trained in a radial extension 30th the hole 21 . The radial expansion 30th is over an annular gap 31 that is between the outer nozzle needle 23 and the wall of the hole 21 is formed with the outer nozzle seat 26 connected so that in this way gaseous fuel to the outer nozzle seat 26 flows. In the nozzle body 20th are several injection openings 27 distributed over the circumference, so that from the outer nozzle seat 26 raised outer nozzle needle 23 gaseous fuel through the annular gap 31 and the outer nozzle seat 26 to the injection openings 27 flows where the exiting gaseous fuel jets of gas 18th forms.

The outer nozzle seat 26 the bore widens away 21 in a spring chamber 33 in which an outer closing spring 44 is arranged. The closing spring 44 is supported with one end on a sleeve 45 and with the other end on the outer nozzle needle 23 starting with the closing spring 44 a cylindrical section 34 the outer nozzle needle 23 surrounds. On the one hand, this causes the outer nozzle needle 23 against the outer nozzle seat 26 pressed and on the other hand the sleeve 45 against the holding body 22 .

In the outer nozzle needle 23 is a longitudinal bore 36 trained in the inner nozzle needle 38 is arranged to be longitudinally displaceable, so that between the inner nozzle needle 38 and the wall of the longitudinal bore 36 a pressure room 37 is trained. The pressure room 37 is about one in the outer nozzle needle 23 trained cross hole 50 with the spring chamber 33 connected and is at its - in the drawing upper - end of an inner sleeve 49 limited. Between the inner sleeve 49 and the inner nozzle needle 38 is an internal closing spring 48 and compressive bracing arranged the inner nozzle needle 38 against an inner nozzle seat 40 presses with a sealing surface 39 and being the inner nozzle seat 40 inside the outer nozzle needle 23 is trained. The inner nozzle seat 40 downstream are several injection openings 43 in the outer nozzle needle 23 trained so that when the inner nozzle needle 38 from the inner nozzle seat 40 has raised liquid fuel from the pressure chamber 37 through the injection ports 42 is sprayed out and liquid jets 19th forms.

Through the outer nozzle seat 26 facing end of the outer nozzle needle 23 , i.e. the cylindrical section 34 who have favourited Sleeve 45 who have favourited Inner Sleeve 49 and the holding body 22 becomes an outer control room 51 limited, in which changing fuel pressure is adjustable. Likewise, through the inner nozzle seat 40 facing end of the inner nozzle needle 38 who have favourited Inner Sleeve 49 and the holding body 22 an inner control room 52 limited. The outer control room 51 is via an outer inlet hole 57 Can be filled with liquid fuel under high pressure and via an outer drain hole 58 relieved, the outer drain hole 58 opens into a low pressure chamber and inside the outer drain hole 58 a first control valve 53 is arranged. The first control valve 53 is designed as a 2/2-way valve, so that the outer drain hole opens and closes 58 the pressure in the outer control room 51 can be varied and thus the hydraulic closing force on the outer nozzle needle 23 .

The inner control room is based on the same principle 52 via an inner inlet bore 60 fillable and via an outer drain hole 61 can be relieved, in the outer drain hole 61 a second control valve 55 is arranged, which is also designed as a 2/2-way valve. From the outer inlet hole 57 also carries out a high pressure drilling 62 in the spring chamber 33 , which is therefore also filled with liquid fuel under high pressure. By lowering the pressure in the first control room 51 or in the second control room 52 can thus independently of one another a longitudinal movement of the outer nozzle needle 23 and the inner nozzle needle 38 to be controlled. By closing the control valves 53 , 55 become the nozzle needles 23 , 38 closed again.

3rd again shows an enlarged view of the section of III 2nd in the area of the nozzle seats 26 , 40 . The outer nozzle needle 23 lies on the outer conical nozzle seat 26 on where a seal of the gas in the annular gap 31 must be reached if no gas is to escape. By closing and opening the outer nozzle needle 23 there are slight relative movements between the outer nozzle needle 23 and the outer nozzle seat 26 , in addition to the impact load caused by attaching the nozzle needle 23 , which leads to wear in this area. In addition, it is complex to machine a conical seat so that it is completely gas-tight, in spite of the relatively high pressure in the annular space 31 no gas into the injection openings 27 reached. By introducing the lubricant through the dosing unit 8th however, finely atomized lubricant reaches the nozzle seat with the gas flow 26 and on the sealing surface 24th , so that this area is slightly lubricated by the lubricant, which reduces the friction between these two surfaces and thus the wear. In addition, the lubricant seals leaks caused by microscopic roughness so that the gas is tightly sealed in this area.

The outer nozzle needle 23 is in the hole 21 of the nozzle body 20th in an area between the spring chamber 33 and radial expansion 30th led so that a throttle gap in this area 35 between the outer nozzle needle 23 and the wall of the hole 21 is formed. 4th shows again an enlarged view of the injector 2nd in the area of the throttle gap 35 , this area in the 2nd is marked with IV. Because in the spring chamber 33 liquid fuel is under high pressure and in the radial expansion 30th Gas under high pressure, there is an inevitable leakage when there are pressure differences between the gas area and the liquid area, since the pressure in the gaseous area is always kept somewhat lower than in the liquid area. This penetrating fuel would also lubricate the outer nozzle seat 26 lead, however, this inflow depends on the pressure difference, the viscosity of the fuel, the temperature and other physical quantities, so that there is an exact lubrication of the outer nozzle seat 26 not possible. The atomizer unit 8th on the other hand, it allows one to Apply the specified amount of lubricant at exactly the right time in order to reduce friction. Especially when the device starts to operate, it is important to have the outer nozzle seat 26 to lubricate what's over the throttle gap 35 cannot be given at this time, but what about the atomizer unit 8th is easily possible.

The use of an atomizer unit 8th A lubricant can also be used in devices in which the liquid and the gaseous fuel are not metered via an injector for both fuels, but in which there is a separate injector for each fuel type, either with separate housings or in a common housing . In this case, the lubricating liquid is metered into the high-pressure line of the injector for the gaseous fuel, as in the exemplary embodiment described above, in order to achieve the desired effects. Such an atomizer unit can also be provided in a device which is used exclusively for metering in gaseous fuel, but in this case the pressure required for atomization must be generated by a suitable separate device.

QUOTES INCLUDE IN THE DESCRIPTION

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Patent literature cited

• DE 102016271009 A1 [0002]

Claims (12)

Device for metering a gaseous and a liquid fuel with an injector (1), which is designed to meter a gaseous fuel under a working pressure, and with a supply line (2) for supplying gaseous fuel to the injector (1), thereby characterized in that an atomizer unit (8) is provided in the supply line (2), via which a lubricating liquid can be introduced in an atomized manner into the supply line (2) for the gaseous fuel. Device after Claim 1 , characterized in that the injector has a longitudinally movable nozzle needle (23) which interacts with a nozzle seat (26) for opening and closing a flow cross-section through which the gaseous fuel can be metered. Device after Claim 1 , characterized in that the supply line (2) has a high-pressure gas space (10), a connecting line (6) leading from the high-pressure gas space (10) to the injector (1) and a high-pressure line (4) via which the high-pressure gas space (10) contains gaseous fuel Can be filled under high pressure, the atomizing unit (8) being arranged in the high-pressure line (4). Device after Claim 1 , characterized in that the atomizer unit (8) is controlled by an electrical control device (15). Device after Claim 3 , characterized in that several injectors (1) for metering the gaseous fuel are connected to the high-pressure gas space (10) via a connecting line (6). Device after Claim 1 , characterized in that the injector (1) is designed not only for metering a gaseous fuel but also for metering the liquid fuel and the device has a high-pressure fuel collecting chamber (11) in which compressed liquid fuel is held under high pressure and from which an inlet line (7) leads to the injector (1). Device after Claim 6 , characterized in that the lubricating liquid is the liquid fuel which can be metered by the injector (1) and the atomizer unit (8) is connected to the high-pressure fuel collecting chamber (11) via a line (5). Method for operating a device for metering a gaseous and a liquid fuel, with an injector (1) which is designed to meter a gaseous fuel under a working pressure, and with a feed line (2) for feeding gaseous fuel to the injector (1), characterized in that an atomizer unit (8) is arranged in the feed line (2) for the gaseous fuel, via which a lubricating liquid is introduced in an atomized manner. Procedure according to Claim 8 , characterized in that the lubricant is liquid fuel. Procedure according to Claim 9 , characterized in that the injector (1) is also designed for metering the liquid fuel and the liquid fuel metered into the supply line is the same fuel which is metered via the injector (1). Procedure according to Claim 8 , characterized in that the lubricating liquid is introduced into the supply line (2) only when gaseous fuel is metered in via the injector (1). Procedure according to Claim 8 , characterized in that the atomizer unit (8) is controlled by means of an electrical control device (15) and the lubricant is only introduced at operating points of an internal combustion engine specified by the control device (15), into which internal combustion engine the injector (1) injects or fuels injected.

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