Device for supplying a gaseous fuel to an engine

Abstract

The invention relates to a device for supplying a gaseous fuel to an engine that comprises a gas accumulator for receiving highly pressurized gaseous fuel, a gas buffer for receiving medium pressurized gaseous fuel, a gas supply device for delivering a gaseous fuel into an engine combustion space, a first gas line that connects the gas accumulator to the gas buffer and whose gas flow can be regulated via a first valve, a second gas line that connects the gas accumulator to the gas buffer and whose gas flow can be regulated via a second valve, and a third gas line that connects the gas buffer to the gas supply device. The device is further characterized in that a compressor is arranged in the second gas line to increase a pressure of a gaseous fuel flowing from the gas accumulator to the gas buffer.

Claims

1. A device for supplying a gaseous fuel to an engine comprising: a gas accumulator for taking up highly pressurized gaseous fuel; a gas buffer for taking up medium pressurized gaseous fuel; a gas supply device for delivering the gaseous fuel into an engine combustion space; a first gas line that connects the gas accumulator to the gas buffer and whose gas flow can be regulated via a first valve; a second gas line that connects the gas accumulator to the gas buffer and whose gas flow can be regulated via a second valve, wherein the second valve is in the second gas line and the second gas line branches from a fourth gas line; a third gas line that connects the gas buffer to the gas supply device; and the fourth gas line extending from the gas accumulator to the gas supply device, wherein a compressor is arranged in the second gas line to increase a pressure of the gaseous fuel flowing from the gas accumulator to the gas buffer, the device further comprises a control unit that is configured to control the first valve such that the gaseous fuel flowing from the gas accumulator into the gas buffer has a medium pressure and, if the gaseous fuel remaining in the gas accumulator falls below the medium pressure, to close the first valve and to open the second valve to bring the gaseous fuel present below the medium pressure in the gas accumulator to the medium pressure with the compressor and to supply said gaseous fuel to the gas buffer, and the control unit is configured to open a further valve for the fourth gas line when a pressure level in the gas accumulator is below the medium pressure and fuel gas is supplied to the engine from the gas accumulator via the fourth gas line, and, when a pressure level in the gas accumulator is at or above the medium pressure, the control unit closes the further valve for the fourth gas line and opens the second valve to provide a fuel gas supply to the engine from the gas buffer via the second gas line.

2. The device in accordance with claim 1, wherein a check valve is arranged between a pressure side of the compressor and the gas buffer.

3. The device in accordance with claim 1, wherein the gas supply device is configured to introduce the gaseous fuel that has the medium pressure into the engine combustion space.

4. The device in accordance with claim 1, wherein the highly pressurized pressure corresponds to a pressure range of 550 to 850 bar, and the medium pressure corresponds to a pressure range of 150 to 500 bar.

5. The device in accordance with claim 1, wherein the gas accumulator has a larger storage volume that is at least 10 times larger than the gas buffer.

6. The device in accordance with claim 1, wherein the gas buffer and/or a gas line section between the gas buffer and the compressor is provided with a heat exchanger.

7. The device in accordance with claim 1, wherein the control unit is configured to extend an opening duration of the fuel gas supply to deliver the gaseous fuel into the engine combustion space and/or to shift ignition timing for a gas or gas mixture present in the engine combustion space when the gaseous fuel remaining in the gas accumulator falls below the medium pressure.

8. The device in accordance with claim 1, wherein the control unit is configured to change at least one operating parameter of the engine when the gaseous fuel remaining in the gas accumulator falls below the medium pressure, by: using a changed set of engine data that, for example, effects a power increase with the disadvantage of a reduced efficiency; lowering a charge air temperature by increasing a cooling power; making a mixture in the engine combustion space more lean by increasing a charge air amount with a simultaneous increase of a charge air cooling power; carrying out an external exhaust gas recirculation using an exhaust gas recirculation cooling; switching in of an internal exhaust gas recirculation; and/or carrying out a water injection.

9. The device in accordance with claim 1, further comprising the gaseous fuel supply to the engine taking place via a direct injection, with the engine being a hydrogen engine that is configured to combust hydrogen or a hydrogen mixture in the engine combustion space.

10. The device in accordance with claim 1, wherein the gas accumulator comprises a plurality of gas pressure storage units connected to one another.

11. The device in accordance with claim 1, wherein the gas supply device comprises a plurality of individual gas injectors that obtain the respective pressurized gas to be delivered into the engine combustion space through a common rail.

12. A mobile work machine, having the device in accordance with claim 1.

13. The mobile work machine in accordance with claim 12, further comprising a recovery device for converting kinetic energy into electrical energy, wherein the mobile work machine is configured to use the electrical energy to operate the compressor.

14. The mobile work machine in accordance with claim 12, further comprising a recovery device for converting kinetic energy into hydraulic energy, wherein the mobile work machine is configured to use the hydraulic energy to operate the compressor by supplying the hydraulic energy to a hydraulic motor driving the compressor.

15. The device in accordance with claim 5, wherein the gas accumulator has a storage volume of at least 25 times larger than the gas buffer.

16. The device in accordance with claim 6, wherein the heat exchanger is connected to a main cooling circuit of the engine.

17. The device in accordance with claim 11, wherein the common rail is arranged in the third gas line.

18. The mobile work machine in accordance with claim 13, wherein the electrical energy converted from kinetic energy is buffered in a battery before the supply to the compressor.

19. The mobile work machine in accordance with claim 14, wherein the hydraulic energy converted from kinetic energy is buffered in a hydraulic accumulator.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further advantages, features, and details of the invention will become clear on the basis of the following description of the Figures. There are shown:

(2) FIG. 1A: an embodiment of the present invention,

(3) FIG. 1B: a further embodiment of the present invention,

(4) FIG. 2: an exemplary operating cycle of an internal combustion engine of a mobile work machine in accordance with the invention; and

(5) FIG. 3: a fuel gas consumption respectively a fuel consumption belonging to the operating cycle of FIG. 2.

DETAILED DESCRIPTION

(6) FIG. 1A shows a schematic representation of the device 1 in accordance with the invention. A gas accumulator 2 can be recognized that preferably comprises a plurality of individual stores. Provision can also be made here that it has a line system that enables a refueling of all the plurality of individual stores and a gas removal via a respective common connection.

(7) The device 1 has a first gas line 5 and a second gas line 7 to a gas buffer 3. A gas connection between the gas accumulator 2 and a gas buffer 3 is produced via the first gas line 5 with an open valve 6 and a pressure limiter 17.

(8) There is a gas connection between the gas accumulator 2 and the low pressure side of a compressor 10 with an open valve 8. Provided that no gas removal from the gas accumulator 2 is provided, the two valves 6, 8 in the respective gas line 5, 7 are closed.

(9) In FIG. 1A, the gas engine is not shown completely for reasons of clarity, but only the fuel gas path including the gas supply device 4.

(10) If the fuel gas pressure in the gas accumulator 2 is not yet above a first threshold value of, for example, 320 bar with respect to its configuration, the first valve 6 is open and the second valve 8 is closed in operation of the gas engine. The first threshold value corresponds to a pressure value at which the fuel gas can be supplied directly into the combustion space of the gas engine at the preferred target pressure. This first threshold value is smaller than the maximum pressure at which the gas accumulator can be filled.

(11) In a provided first operating mode, the fuel gas suppled to the gas engine is taken from the gas accumulator 2 and is supplied to a combustion space via the open first valve 6, the pressure limiter 17, the gas buffer 3, the controllable or regulable unit 16 for setting the rail pressure, the rail 14, and finally via an open injector 13. The gas buffer 3 in this operating mode only serves the reduction of pressure fluctuations of the fuel gas conducted at the gas engine.

(12) Without the pressure limiter 16, the gas buffer 3 would have to be substantially more pressure resistant. It is nevertheless conceivable that the desired pressure level can be maintained in the rail 14 without a pressure limiter 16 by a pulsed delivery of gas from the gas buffer 3. This is, however, possible better and simpler with the pressure limiter 16.

(13) In a specific embodiment, it can be a 6 cylinder hydrogen engine that has a maximum power in a range from 360 kW to 400 kW. The preferred rail pressure, i.e. a first target value of the rail pressure, can be in the range of 300 bar. The gas accumulator 2 can here be configured for a pressure level of approximately 700 bar. Provision can furthermore be made that the gas buffer 3 is designed for a maximum pressure of 450 bar or less, for example 400 bar or 350 bar.

(14) After a certain operating duration of the gas engine and after the continuous removal of fuel gas from the gas accumulator 2 associated therewith, the pressure in the gas accumulator 2 approaches a first threshold pressure value of, for example, 320 bar. Provided that the fuel gas pressure in the gas accumulator 2 is no longer above this first threshold pressure value, the preferred pressure level of, for example, 300 bar can no longer be provided to the rail 14 over the gas line 5.

(15) A second operating mode can accordingly be provided in accordance with the invention in which the second valve 8 is open in good time before the reaching of this first threshold value and the compressor 10 is operated. The fuel gas supply from the gas accumulator 2 into the gas buffer 3 thus takes place over the second gas line 7, with the pressure level being raised by the compressor 10 so that the preferred pressure level of, for example, 300 bar can continue to be provided to the rail 14 starting from the gas buffer 3.

(16) The design of the device 1 in accordance with the invention enables an interruption-free switching over of these two operating modes of the fuel gas supply, with the fuel gas being obtained directly from the gas accumulator 2 via the first valve 6 in the first operating mode and with the pressure level of the fuel gas coming from the gas accumulator 2 over the second gas line 7 being raised while using a compressor 10 in the second operating mode and a fuel gas store at a sufficiently high pressure thereby being provided in the gas buffer 3 to be able to provide the rail with the preferred target pressure of, for example, 300 bar.

(17) The fuel gas supply in accordance with the invention preferably provides a cooling possibility of the fuel gas compressed by the compressor 10. This can take place via a heat exchanger 12 installed in the gas buffer 3. The secondary side of the heat exchanger 12 could by way of example be connected to the main cooling circuit of the gas engine. Alternatively or additionally, a heat exchanger 12 could be installed at a different point of the fuel gas supply in accordance with the invention, for instance along the path between the compressor 10 and the gas buffer 3.

(18) The fuel gas supply in accordance with the invention enables a fuel gas removal from the gas accumulator 2 while supplying its intended use up to a pressure level that is a great deal smaller than the first threshold value of, for example, 320 bar. In order, on the one hand, to be able to utilize a high proportion of the fuel gas amount present in the gas accumulator 2 up to a refueling and, on the other hand, to keep demands and thus the costs for a suitable compressor 10 within limits, a gas removal is provided up to a dropping of the pressure level to a second threshold pressure value that can, for example, be at approximately 50 bar. A reciprocating compressor has proved to be advantageous for the implementation of a compressor 10.

(19) The requirement that it is ensured up to the reaching of the second threshold pressure value in the gas accumulator 2 that a sufficiently high mass flow of compressed fuel gas can be supplied to the gas buffer 3 to be able to operate the gas engine at the working point of its maximum output power is a further important aspect for the design of the compressor 10 and of its drive 15. It is clear here that this requirement can be alleviated in specific applications, for example in that only that working range of the gas engine is looked at that is actually used in the application or in that a gas buffer 3 is used that has a sufficiently high capacity (e.g. the configuration 350 bar or 400 bar and 25 l), whereby brief load peaks of the gas engine can be dealt with. However, this is only sensible when only brief load peaks occur in the application.

(20) Provision can be made in a preferred embodiment of the invention that the compressor 10 only works at a single working point and accordingly in pulsed operation. The drive of the compressor 10 can in this manner be operated at the best systemic point or at least at a particularly high system efficiency. The compressor is particularly preferably switched on when the fuel gas pressure in the gas buffer drops to a third threshold value of, for example, 330 bar and is switched off when a fourth threshold value of, for example, 350 bar is reached.

(21) Starting from the operating situation of a completely filled gas accumulator 2, the fuel gas can flow over the first gas line 5 to the gas buffer 3 and the gas supply device 4 can be operated at the first target value of the rail pressure of, for example, 300 bar. Provided that the first threshold pressure value in the gas accumulator 2, that should amount to 320 bar by way of example, is fallen below, an operation can take place in which the fuel gas of the gas supply device 4 is still supplied via the gas line 5 while carrying out a third operating mode up to the reaching of a further, fifth threshold pressure value that is disposed below it and that can, for example, amount to 220 bar. However, this requires a lowering of the rail pressure to a second target value of, for example, 200 bar that has to be below the fifth threshold pressure value. The fact that the power output capacity of the gas engine is reduced due to the lowered target rail pressure can be avoided by other measures (see below).

(22) The starting point of the third operating mode is a lowering of the fuel gas pressure in the gas buffer 3 to a fifth threshold pressure value of, for example, 220 bar that is below the first threshold pressure value of, for example, 320 bar.

(23) It is clear that with the stipulation of the fifth threshold pressure value of, for example, 220 bar in the gas buffer 3, the supply can initially take place over the first gas line 5. As soon as the gas pressure in the gas accumulator 2 falls below the fifth threshold pressure value, the gas supply takes place over the second gas line 7 having the compressor 10.

(24) If the gas pressure in the gas accumulator 2 in this third operating mode is below the first target pressure value (of, for example, 320 bar), but above the fifth target pressure value (of, for example, 220 bar), a fuel gas amount that no longer covers performance would be provided to the engine combustion space with an unchanged operating management of the gas engine and/or of the gas supply device 4.

(25) To avoid this, a different parameter set separately provided for this purpose has to be used by the engine management that in particular has an effect on the control or regulation of the fuel gas injection.

(26) So that the same amount of fuel gas is supplied to the combustion space while reducing the rail pressure, the opening duration of the respective injector 13, or more generally of the gas supply device 4, can be extended by a control or regulation unit. The same engine performance can thereby also be achieved at least within certain limits at a reduced fuel gas pressure. An adaptation of the injection start can furthermore also be sensible or necessary. Alternatively or additionally, a shift of the ignition angle can be sensible or necessary. If corresponding interventions are provided, the shifts of the injection start and/or of the ignition angle preferably take place in the direction of the piston bottom dead center of the engine.

(27) So that the gas engine can cover its full power range in an operation in accordance with the invention in accordance with this third operating mode at which the second target value of the rail pressure of, for example, 200 bar is valid that is lower than the first desired value of the rail pressure of, for example, 300 bar, an intervention in the operating management of the gas engine can be provided. Such an intervention can be one of the measures named below or a combination thereof:

(28) using a different set of changed engine data that have been stored separately for this purpose and that effects a power increase, for example, with the disadvantage of a reduced efficiency with respect to the lower rail pressure;

(29) lowering the charge air temperature by increasing the cooling power;

(30) making more lean by increasing the charge air amount with a simultaneous increase of the charge air cooling power;

(31) external exhaust gas recirculation (EGR) with EGR cooling;

(32) internal EGR can be switched in

(33) water injection, e.g. into the charge air and/or into the EGR path.

(34) FIG. 1A is a modified embodiment of the present invention. The device 1 shown there has been expanded by a further gas line 17, the fourth gas line 17, that extends to the gas pressure control unit 16 for the setting of the rail pressure starting from the pressure gas store 2 over a further control valve 20 that can optionally be provided, a pressure limiter 18, and a pressure tank 19 that is only required to alleviate pressure fluctuations and can therefore be very small. This modification allows a need-based use of the compressor 10. The control unit may have instructions stored therein (e.g., in non-transitory memory) to receive input from one or more sensors in the system, and send signals to one or more actuators, such as the control valve, or an engine actuator, to control rail pressure or the engine as described herein.

(35) If the pressure level in the gas accumulator 2 has a value between the first threshold pressure value of, for example, 320 bar and the fifth threshold pressure value of, for example, 220 bar, the gas is conveyed over the fourth gas line 17. In the case of low to medium power demands on the gas engine, the second target value of the rail pressure of, for example, 200 bar applies and in the case of high powers, the first target value of the rail pressure of, for example, 300 bar is valid. In other words, the rail pressure can vary in dependence on the required engine load. If the second rail pressure target value of, for example, 200 bar applies, that is, for example, a low power demand, the fuel gas supply preferably takes place over the fourth gas line 17 directly from the gas accumulator 2, with the gas received therein having a sufficiently high pressure to generate the required rail pressure. A pressure level of, for example, 230 bar that is in any case somewhat above the fifth threshold pressure value of, for example, 220 bar is provided in the gas buffer 3. If a high power demand is made starting from a low to medium load of the gas engine, a fuel gas supply of the gas engine from the gas buffer 3 takes place over the second gas line 7 by a corresponding switchover of the valves for the different gas lines 5, 7, 17 emanating from the gas accumulator. The latter makes possible a raising of the rail pressure to its first target value of, for example, 300 bar, that has to be present on a high power request in the rail, while using the compressor 10.

(36) The big advantage here is that less energy is supplied to the compressor 10 overall because a smaller amount of fuel gas has to be raised via the compressor 10 during this operating mode and starting from a pressure level between the first and fifth threshold pressure values to a correspondingly high pressure level that enables an operation of the gas engine below the first target value of the rail pressure of, for example, 300 bar. If the instantaneous pressure in the pressure gas store 2 is within the range between the first threshold pressure value and the fifth threshold pressure value, the higher target value of the rail pressure is only requested when, due to a high power request to the gas engine with an increased value, an increased rail pressure can be used that has to be supplied with an energy use applied on board. In contrast, the second rail pressure target value of, for example, 200 bar applies during this further operating mode in lower and medium partial low operation of the gas engine because a compensation of the smaller rail pressure is possible here with respect to the gas engine by a simple adaptation of the fuel gas injection times and no or hardly any noticeable efficiency disadvantages therefore result. Any further ones of the aforesaid measures of a modified operating management of the gas engine that result in higher efficiency losses can be omitted in contrast.

(37) The same principle can naturally be applied to different operating modes when the pressure level in the gas accumulator 2 has a value between the second threshold pressure value of, for example, 220 bar and a third threshold pressure value of, for example, 170 bar. In the fourth operating mode, a fuel gas supply of the gas engine can equally take place over the fourth line 17 shown in FIG. 1B, which is, however, only preferred for the lower load range. A fuel gas store is also provided at a pressure level of, for example, 330 bar in the gas buffer 3 in this operating mode to here also be able to switch over to a high load operation of the gas engine at short notice.

(38) Provision can furthermore be made that a mobile work machine provided with the device in accordance with the invention has a recovery device. As is known, technical systems are equipped with energy stores so that an instantaneously available recovery power can be used at a later time.

(39) Energy recovery is possible in certain application areas of the invention. On the use of a gas engine that is used together with a device in accordance with the invention in a mobile work machine, excess kinetic energy can e.g. arise. In the case of a mobile work machine configured as a crane, for instance, on the lowering of loads or on braking procedures during the travel movement. As is sufficiently known, rotation energy can be converted in such operating situations by electric machines operated as generators into electrical energy that can in turn be stored in a battery and/or in a double layer capacitor.

(40) A further development of the invention provides that at least a proportion of this recovered or recoverable energy is used for the power supply of the compressor 10. In the event that the fuel gas pressure level in the gas accumulator 3 has already dropped below a threshold pressure value, the arising recovery power can be directly supplied to the compressor 10 so that it is supplied with fuel gas from the gas accumulator 2 to compress it accordingly so that it can be supplied to the gas buffer 3. In this manner, the process energy is provided, without using energy that has to be separately taken from the gas accumulator for this purpose, to produce a raising of the pressure level respectively an increase of the fuel gas store in the gas buffer that is then supplied to the gas engine in such operating situations when an efficiency advantage results, e.g. in high load operation, due to the high fuel gas injection pressure of, for example, 300 bar.

(41) Alternatively or additionally, further energy stores that may be present can simultaneously be charged. In an exemplary embodiment, the compressor 10 could be driven by an electric machine 15 that is supplied via the onboard network battery. In this manner, the anyway present gas buffer 3 is supplied with recovery energy that could no longer be taken up at all by an onboard network battery that may be fully charged. It can optionally be sensible here to equip the gas engine with a more powerful generator and/or at least with one further alternator respectively an additional generator.

(42) An onboard network battery having a higher capacity and/or an additional battery can optionally naturally be used for the storage of electrically recovered energy. In this respect, the gas buffer 3 that is anyway required can be used, depending on the manner of observation, as a direct user or as an energy store of recovery power.

(43) Additionally or alternatively, a generator for taking up recovery power can also be installed such that it can take up recovery power outside the gas engine; in the example of a mobile work machine at the transfer case or in force transmission with a hydraulic machine via whose drive shaft recovery power occurs in certain operating situations.

(44) Alternatively or additionally, at least one electrical energy store can be used that is based on double layer capacitors. Unlike battery cells, double layer capacitors have a much higher power density, but a smaller energy density. If there are predestined points of the occurrence of recovery power that is briefly very high at a mobile work machine and if a correspondingly powerful generator is provided for electrical recovery, the use of double layer capacitors can be particularly sensible. The double layer capacitors can store the high electrical powers that are subsequently provided to the comparatively low power electric motor driving the compressor 10. In general, double layer capacitors are more resistant to low temperature and more resistant to high temperatures and have a higher charge/discharge cycle strength than batteries.

(45) Alternatively or additionally, a drive of the compresses via a hydraulic motor is possible. In a possible embodiment, this hydraulic motor is supplied by a hydraulic pump that can, for example, be located at a power takeoff of the gas engine or is installed at the transfer case. The hydraulic pump is preferably installed at a point in the drive system at which recovery power arises from time to time. Alternatively, instead of a separate hydraulic pump, a hydraulic motor required for the primary functions of the mobile work machine can be replaced with a hydraulic machine that works when recovery power arises in pump operation. When recovery power arises, it can be directly supplied to the hydraulic motor driving the compressor 10. A hydraulic accumulator for taking up recovery power that arises can be installed so that higher recovery powers can be taken up. A hydraulic accumulator can take up high powers comparable with a double layer capacitor, but has a low energy density. At a point at which high recovery powers are incurred briefly, they can thus be recovered and supplied to a hydraulic accumulator and is subsequently supplied to the hydraulic motor driving the compressor.

(46) Alternatively or additionally, a plurality of hydraulic pumps, via which a hydraulic recovery is possible, can be used, with a plurality of hydraulic accumulators also being able to be installed for taking up recovery power.

(47) In an application in which comparatively high portion amounts of recovery energy are incurred, it can be sensible to use a gas buffer having a higher capacity (e.g. 50 l).

(48) A specific application example of an internal combustion energy will be presented in the following that has an engine power in the range from 360 kW to 450 kW and that can be provided for a mobile work machine, for example for a very large crawler crane having a payload of up to 300 metric tonnes. If this internal combustion engine were represented by a hydrogen engine, the would be a 6 cylinder engine having a capacity of two to three liters per cylinder from today's point of view, that has a hydrogen consumption of 27 kg/h at the operating point of its maximum output power.

(49) Provision can thus be made that a hydrogen removal from the gas accumulator 2 takes place for so long until a residual pressure of 50 bar is present.

(50) Provision can be made as a rule that a rail pressure of 300 bar is always provided to the hydrogen engine, i.e. during the whole time period over which the hydrogen pressure in the gas accumulator 2 falls from an initial approximately 700 bar to 50 bar in the course of the engine operation. In accordance with the invention, the compressor 10 supplies the gas buffer 3 with hydrogen amounts so that a maintenance of the rail pressure of 300 bar is possible. The maximum power of the compressor 10 results from the constellation that the compressor 10 has to provide a compression of hydrogen from 50 bar to, for example, 320 bar, at a flow rate of 27 kg/h. In practice, this constellation will only occur for a very brief time and requires the situation that the usable hydrogen accumulator in the gas accumulator tank 2 is just exhausted while the hydrogen engine is operated under full load. In this theoretical operating situation, the compressor should have a mechanical input power of at least 9 kW, preferably more than 12 kW, or better at least 14 kW.

(51) The unit comprising the compressor 10 and its drive 16 is preferably configured such that a compression of fuel gas taken from the gas accumulator 2 can take place at this power with an efficiency that is as high as possible, said fuel gas being supplied to the gas buffer 3 so that a provision of fuel gas from this is possible while achieving a rail pressure of, for example, 300 bar.

(52) The recharging of the gas buffer 3 thus preferably takes place portion-wise by a pulsed operation of the compressor 10. An automatic switching on and switching off of the compressor 10 particularly preferably takes place; for example in accordance with a simple two point characteristic. The switching on of the drive 16 takes place here above a specific pressure level in the gas buffer 3 at which the target rail pressure can still be provided and the switching off takes place at a specific pressure level disposed thereabove.

(53) In accordance with the above third operating mode in which a rail pressure of 200 bar is available to the hydrogen engine, a demand of mechanical input power of the compressor amounts to at least 6 kW, better at least 8 kW, or even at least 10 kW.

(54) FIG. 2 shows a diagram of the engine speed and energy power over time. The graph arranged at the top in the diagram here represents the engine speed; the graph arranged below it shows the engine power. The two time progressions originate from a tachometer trace of a heavy crawler crane in real work deployment.

(55) It can be recognized that in this real tachometer trace of a work deployment of the heavy crawler crane a plurality of work maneuvers is present (fine hook positioning, installation of the raised component, etc.) and thus long time periods are present during which the primary drive only works in the lower partial load operation, whereas the time periods in which the primary drive works in the upper partial load operation are comparatively short. The supply in accordance with the invention of the gaseous fuel is very efficient for such a use. Under the assumption that during the tachometer trace shown a fuel gas pressure is present in the gas accumulator between the first and second threshold values; the operating of the invention in the operating mode described in connection with FIG. 1A is above all very advantageous. In the dominating time periods, an operation of the gas engine is possible below the second rail pressure target value of, for example, 200 bar without having to perform such interventions in the operating management of the gas engine. However, thanks to the possibility of obtaining fuel gas from the gas buffer 3, the gas engine can very easily be operated during the covering of its load peaks while the first rail pressure target value is valid and is maintained, whereby such interventions in the operating management of the gas engine that permit an increased power output only in connection with a reduction in efficiency can also be omitted in high load phases. Thanks to the possibility of being able to remove fuel gas from the gas pressure tank 2 in parallel with the actual work deployment of the heavy crawler crane and of being able to supply the gas buffer 3 via the compressor 10 at a sufficiently high pressure, it is possible to be able to operate the gas engine during the validity and maintenance of the first rail pressure target value over longer time periods, which could possibly be necessary in the shown tachometer track within the time period in which the actual raising of the load evidently takes place (about the time 1000 s).

(56) If the covering of the load peaks is to take place over an operation, of the gas engine below the first rail pressure target value while a fuel gas pressure is present in the gas accumulator 2 between the first threshold pressure value and the fifth threshold pressure value, the total compression energy to increase the pressure of the fuel gas has to be obtained at an increased fuel gas consumption. If the already presented possibility of recovery is included as a continuation of the invention in the considerations made here, it can be possible that a large part of the energy that is obtained from the compressor 10 to be able to provide said gas store in the gas buffer 3 can be taken from the recovery energy instead of a removal from the gas accumulator 2 separately required for this purpose.

(57) As already discussed, an operation of the gas engine is alternatively possible while the second rail pressure target value of, for example, 200 bar is valid, but requires such interventions in the operating management of the gas engine that result in an increased fuel gas consumption to cover the load peaks.

(58) FIG. 3 shows the fuel consumption belonging to FIG. 2 in kg/h. The tachometer trace shown in FIG. 2 comes from a heavy crawler crane operated by a diesel engine. The fuel consumption shown in FIG. 3 is based on simulation results that in turn relate to measurement and simulation results of a hydrogen engine in development. The hydrogen consumption substantially correlates with the available motor power.

REFERENCE NUMERAL LIST

(59) 1 device 2 gas accumulator 3 gas buffer 4 gas supply device 5 gas line 6 first valve 7 second gas line 8 second valve 9 third gas line 10 compressor 11 check valve 12 heat exchanger 13 gas supply injector 14 rail 15 compressor drive 16 gas pressure control device 17 fourth gas line 18 pressure limiter 19 compensation tank