DUAL-FUEL INTERNAL COMBUSTION ENGINE

Abstract

Dual-fuel internal combustion engine with at least two combustion chambers which have a different distance from at least one gas mixer for producing a gas-air mixture, whereby an inlet valve for the gas-air mixture and an injector for liquid fuel is assigned to each of the combustion chambers, and a control device is provided which is configured in a change-over mode to change an amount of energy supplied to the at least two combustion chambers through the gas-air mixture in a first direction, and to change an amount of liquid fuel supplied to the at least two combustion chambers in an opposite, second direction, whereby the control device is designed to determine a time for the change of the amount of liquid fuel in the second direction for each of the at least two combustion chambers according to the distance of the respective combustion chamber from the at least one gas mixer.

Claims

1. Dual-fuel internal combustion engine with at least two combustion chambers which have a different distance from at least one gas mixer for producing a gas-air mixture, whereby an intake valve for the gas-air mixture and an injector for liquid fuel is assigned to each of the combustion chambers, and a control device is provided which, in a change-over mode, is designed to change an amount of energy supplied to at least two combustion chambers through the gas-air mixture in a first direction, and to change an amount of liquid fuel supplied to the at least two combustion chambers in an opposite second direction, characterized in that the control device is designed to establish a time for the change in the amount of liquid fuel in the second direction for each of the at least two combustion chambers according to the distance of the respective combustion chamber from the at least one gas mixer.

2. A dual-fuel internal combustion engine according to claim 1, characterized in that a plurality of combustion chambers is provided, whereby the control device is designed to determine a time for the change in the amount of liquid fuel for the combustion chambers according to an individual distance of the respective combustion chamber from at least one gas mixer.

3. A dual-fuel internal combustion engine according to claim 1, characterized in that a plurality of combustion chambers is provided, which are organized in the control device in the at least two groups, said groups having a different distance from the at least one gas mixer, whereby the control device is designed to determine a time for the change in the amounts of liquid fuel for the at least two groups according to a distance between the at least two groups of the gas mixer.

4. A dual-fuel internal combustion engine according to claim 3, characterized in that the setpoint value of the start of an injection of the liquid fuel into one of the combustion chambers is selected according to its membership of one of the at least two groups.

5. A dual-fuel internal combustion engine according to one of the preceding claims, characterized in that the control device is designed to select a time interval between the change in the first direction and the change in the second direction according to an ignition sequence.

6. A dual-fuel internal combustion engine according to one of the preceding claims, characterized in that the start of the injection of the liquid fuel into a combustion chamber is corrected according to the mixture temperature present in this combustion chamber and/or the knocking tendency to be expected in this combustion chamber.

7. A dual-fuel internal combustion engine according to one of the preceding claims, characterized in that at least one cylinder pressure sensor is provided for measuring a pressure flow in the at least one combustion chamber, whereby signals from the at least one cylinder pressure sensor can be supplied to the control device, and the control device is designed for this, in order to correct the change in the amount of energy supplied by the liquid fuel and/or the start of the injection of the liquid fuel into a combustion chamber for one of the at least two combustion chambers according to the signals of the at least one cylinder pressure sensor.

8. A dual-fuel internal combustion engine according to one of the preceding claims, characterized in that the control device is designed to select the time interval between the change in the second direction and the change in the first direction according to a change in a substitution rate and/or the start of an injection of the liquid fuel.

9. A method for operating a dual-fuel internal combustion engine, whereby an amount of energy supplied to at least two combustion chambers of the internal combustion engine by a gas-air mixture is changed in a first direction and an amount of liquid fuel supplied to one of the at least two combustion chambers is changed in an opposite, second direction, characterized in that a time for the change in the amount of liquid fuel in the second direction is determined for each of the at least two combustion chambers according to the distance of the respective combustion chamber from the at least one gas mixer.

Description

[0037] Further advantages and details of the invention can be found in the figures and the related description of the figures. They are as follows:

[0038] FIGS. 1a to 1c show some figures for the clarification of a first exemplary embodiment of a dual-fuel internal combustion engine according to the invention and a method according to the invention,

[0039] FIG. 2 shows a second exemplary embodiment,

[0040] FIGS. 3a and 3b show a further simplified exemplary embodiment for the better understanding of the invention and

[0041] FIG. 4 shows a schematic representation of a dual-fuel internal combustion engine.

[0042] FIG. 1a shows schematically a dual-fuel internal combustion engine with 16 combustion chambers. These combustion chambers are numbered consecutively from 1 to 16 according to the ignition sequence. It is schematically indicated that the gas-air mixture arrives in the individual combustion chambers from a gas mixer located on the right-hand side of the internal combustion engine. The combustion chambers are organized into two groups (Group 1 and Group 2).

[0043] FIGS. 1b and 1c show the course of the amounts of gas and liquid fuel that are present in the combustion chambers of the two groups. The time curve of the air excess lambda is also shown.

[0044] In all exemplary embodiments, diesel is used as a liquid fuel.

[0045] FIG. 1b shows the different amount trends for Group 2, and FIG. 1c is analogous in relation to Group 1.

[0046] At the time T_S, gas is admixed via the gas mixer. This gas will reach Group 1 faster than Group 2. Therefore, in the case of Group 1, the diesel amount is withdrawn at time T_1. In the case of Group 2, this occurs only at a later time T_2. At the end of the changeover operation (time T_E), an equal ratio exists in all combustion chambers between the gas amount Q_Gas and the diesel amount Q_Diesel. The air excess lambda is also adjusted.

[0047] During the changeover, it is also provided to correct the start of the injection of the liquid fuel, in this case diesel, according to the mixture temperature present in the respective combustion chamber and the knocking tendency expected in this combustion chamber. The setpoint value to be corrected for the start of the diesel injection is thus dependent on which group the respective combustion chamber belongs to.

[0048] In FIG. 1a, the combustion chambers are numbered by their positions in the ignition sequence. The ignition sequence can be used to determine the time for the change to the second direction (withdrawal of the diesel amount). For example, for the combustion chamber with number 1 in the ignition sequence, a calculated distance of Group 2 from the gas mixer can be corrected using a correction factor. The correction factor may, for example, be additive or multiplicative. Due to its position 1, which is far away from the gas mixer and therefore, at a specific time, has a lower gas concentration than, for example, the combustion chamber with position 15, an effective expansion of the calculated distance is indicated in this case by the correction factor (i.e. the amount of diesel is later withdrawn).

[0049] FIG. 2 shows an alternative exemplary embodiment. Here, the combustion chambers of the dual-fuel internal combustion engine are divided into four groups. Otherwise, this exemplary embodiment is analogous to the one shown in FIGS. 1a to 1c.

[0050] For a better understanding of the invention, a further exemplary embodiment is shown in FIGS. 3a and 3b which, for the sake of simplicity, comprises only four combustion chambers. This is shown in FIG. 3a. Again, a gas mixer is provided that is arranged in the figure on the right-hand side of the combustion chambers (again indicated by an arrow labeled gas).

[0051] FIG. 3b shows several diagrams, whereby the injected diesel amount is shown for different work cycles. Four work cycles are shown that, however, do not have to follow one another directly. In practice, it will actually be more common that there are several other work cycles between the work cycles shown. The changes in the diesel amount can thus change continuously or stepwise between the illustrated work cycle. In this exemplary embodiment, the gas amount admixed in the gas mixer is increased at a certain point in time before work cycle 1. In work cycle 1, this increased gas volume has not yet reached the combustion chambers. The diesel amount is therefore not changed for any of the four combustion chambers.

[0052] The modified gas volume has reached combustion chambers 3 and 4 in work cycle 2, but has not reached combustion chambers 1 and 2.

[0053] Therefore, in work cycle 2, the diesel amount for combustion chambers 3 and 4 must be reduced. This can be done stepwise, as shown by the difference between the illustrated work cycles 2 and 3. In a first step (work cycle 2), the diesel amount Q_Diesel of combustion chambers 3 and 4 is reduced by a certain amount. This behavior is continued in work cycle 3 and the diesel amount Q_Diesel intended for the combustion chambers after the changeover is already used in work cycle 3 for combustion chambers 3 and 4.

[0054] However, this stepwise withdrawal of the diesel amount Q_Diesel is not absolutely necessary. An abrupt withdrawal of the diesel amount Q_Diesel can also be advantageous.

[0055] Following the processes, in work cycle 4 the changed gas amount in the gas-air mixture feed now also reaches combustion chambers 1 and 2. Here, the diesel amount is immediately withdrawn from the amount existing before the changeover at the desired diesel amount Q_Diesel. At this time, the same diesel amount Q_Diesel is then injected again in all combustion chambers 1 to 4.

[0056] It should be noted that FIGS. 3a and 3b are purely schematic. In particular, the ratios of the diesel amounts Q_Diesel may differ greatly in practice from the ratios shown here.

[0057] In the case of the injection events (work cycle 3, combustion chamber 3 and work cycle 4, combustion chamber 2) provided with the reference symbols X, the ignition sequence ZR shown on the right must also be understood as a time axis. The shifted indicators for the diesel amount Q_Diesel indicate that the injection of the diesel starts earlier than is normally provided. This can be done, for example, in response to an excessively high cylinder pressure or an undesired combustion process.

[0058] FIG. 4 shows schematically a dual-fuel internal combustion engine according to the invention. It has four combustion chambers B1 to B4, which can be supplied with liquid fuel, in this case diesel, via the injectors I1 to I4.

[0059] To create the gas-air mixture, a central gas mixer GM is provided, which is connected to an air supply L and a gas reservoir G, e.g. a tank. Via a gas-air mixture supply R, the gas-air mixture produced in the central gas mixer GM is fed to the combustion chambers B1 to B4. Downstream of the gas mixer GM, a compressor V of a turbocharger (mixed-charged internal combustion engine) is also provided. However, the gas mixer GM could also be arranged downstream of the compressor V in the air supply (air-charged internal combustion engine). The number of combustion chambers B1 to B4 is purely exemplary.

[0060] The invention can be used in dual-fuel internal combustion engines with 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 or 24 combustion chambers.

[0061] Reciprocating piston engines can be used, i.e. the combustion changes are arranged in piston cylinder units.

[0062] The invention can preferably be used in a stationary internal combustion engine, for marine applications or mobile applications such as so-called non-road mobile machinery (NRMM), preferably as a reciprocating piston engine. The internal combustion engine can be used as a mechanical drive, e.g. for operating compressor systems or coupled with a generator to a genset for generating electrical energy.