Method and control device for operating a system of several internal combustion engines

Abstract

Method for operating a system (1; 21) consisting of several internal combustion engines (2, 3; 22, 23), wherein the internal combustion engines (2, 3; 22, 23) are coupled such that partial drive powers provided by running internal combustion engines (2, 3; 22, 23) are taken off by at least one common consumer (4; 24), wherein the internal combustion engines (2, 3; 22, 23) are operated such that the total drive power provided by the running internal combustion engines (2, 3; 22, 23), which corresponds to the sum of the partial drive powers, corresponds at least to the power required for the common consumer(s) (4; 24), and wherein, with the required power being provided, an individual operating point is determined for each running internal combustion engine (2, 3; 22, 23) and the respective internal combustion engine (2, 3; 22, 23) is operated at this individual operating point. namely such that for the system (1;21) while complying with emission limits, minimal operating costs are incurred, for each internal combustion engine (2, 3; 22, 23) an individual operating point is determined such that the system (1; 21) incurs minimal operating costs from operating costs and maintenance costs.;

Description

[0001] The invention relates to a method for operating a system of several internal combustion engines. Furthermore, the invention relates to a control device for carrying out the method.

[0002] Systems consisting of several coupled internal combustion engines are known from marine applications. These systems are coupled in such a way that the partial propulsion power provided by the engines is drawn by at least one common consumer. The partial propulsion power provided by the system's engines together constitutes a total power output, which is drawn by the common consumer(s). The respective consumer can be a mechanical consumer, an electrical consumer, or a hydraulic consumer. In the case of a common mechanical consumer, the system is referred to as a mechanically coupled internal combustion engine; in the case of a common electrical consumer, as an electrically coupled internal combustion engine; and in the case of a common hydraulic consumer, as a hydraulically coupled internal combustion engine.It is known from marine applications that a system of mechanically coupled internal combustion engines, acting as a common mechanical consumer, mechanically drives a ship's propeller. Furthermore, it is known that a system of electrically coupled internal combustion engines, acting as an electrical consumer, drives a generator to produce electrical energy, which can then be used, for example, to drive an electric motor and / or other consumers. It is also possible for internal combustion engines to be mechanically, electrically, and / or hydraulically coupled, depending on the configuration of several common consumers.

[0003] In practice, a system of several coupled internal combustion engines is operated in such a way that, depending on the power required by the common consumer(s), several running internal combustion engines each provide identical partial drive power to collectively supply the power required by the common consumer(s). If the power required by the common consumer(s) is relatively high, typically all internal combustion engines are operated in such a way that they provide identical partial drive power. Conversely, if the power required by the common consumer(s) is relatively low, one or more internal combustion engines in the system can be shut down, while the remaining running internal combustion engines are operated in such a way that they provide identical partial drive power.

[0004] DE 10 2013 207 047 B3, DE 10 2011 076 073 A1, US 2007 / 0 191 179 A1 and DE 10 2009 036 277 A1 disclose systems with multiple internal combustion engines that have a common consumer of the partial drive power.

[0005] US 2012 / 0 022 728 A1 and US 2007 / 0 219 683 A1 reveal the control of several locomotives in a train with a common consumer.

[0006] Based on this, the present invention aims to create a novel method for operating a system of several internal combustion engines and a control device for carrying out the method.

[0007] This problem is solved by a method according to claim 1.

[0008] According to the invention, an individual operating point is determined for each running internal combustion engine by providing the requested power and the respective internal combustion engine is operated at this individual operating point, namely in such a way that minimal operating costs are incurred for the system while complying with emission limits.

[0009] The invention makes it possible to operate a system of several internal combustion engines in a particularly economical way.

[0010] The operating points for the running internal combustion engines are selected to minimize operating costs for the overall system. This is achieved not by operating all running internal combustion engines at an identical point, but rather by determining an individual operating point for each engine and operating it at that specific point. An optimal operating point is not determined for a single engine, but rather for the system as a whole. This is done while adhering to emission limits, which must be strictly observed during operation.

[0011] Preferably, at least one running internal combustion engine of the system is operated at an individual operating point such that the NO X-The raw emissions and / or the raw CO2 emissions and / or the boost pressure and / or the fuel injection pressure and / or the compression ratio and / or the fuel-air ratio and / or the exhaust gas temperature of this internal combustion engine differ from the corresponding operating parameter of the or any other running internal combustion engine of the system, in particular by at least 10%, preferably by at least 20%, most preferably by at least 50%. This enables a particularly advantageous operation of a system consisting of several coupled internal combustion engines.

[0012] A particularly advantageous approach is to determine an individual operating point for each operating internal combustion engine, ensuring minimal operating costs for the system, encompassing both fuel and maintenance expenses. Operating costs include fuel expenses and maintenance / service costs, allowing for the determination of the individual operating point for each engine within the system of coupled internal combustion engines. This enables particularly economical operation of a system comprising multiple coupled internal combustion engines.

[0013] Preferably, when determining the individual operating points, the provision of reserve power and / or load-switching capability for each operating internal combustion engine and / or the entire system is also taken into account. When not only emission limits but also reserve power and / or load-switching capability for the system are considered, the system can be operated particularly advantageously.

[0014] Preferably, when determining the individual operating points for the running internal combustion engines, priorities are also taken into account, which depend in particular on fuel costs and / or maintenance costs and / or the remaining drive power available until the next service interval. Prioritization makes it possible to determine the operating points for the internal combustion engines taking into account the priorities specified by the operator.

[0015] When an exhaust aftertreatment system is present, minimum temperatures must usually be maintained. The method according to the invention is also applicable here. For this purpose, the internal combustion engines are operated in such a way that the desired, usually elevated, exhaust gas temperatures are achieved at minimal operating costs. Since increasing the exhaust gas temperature through otherwise conventional measures, such as lowering the air / fuel ratio or adjusting the injection timing, leads to a significant increase in fuel consumption, the application of the method according to the invention is particularly effective here. For this purpose, different engines are operated under different loads, so that different exhaust gas temperatures result, or the effort required to heat the exhaust gas can be reduced.

[0016] The control device according to the invention comprises means for carrying out the method according to the invention.

[0017] Preferred embodiments of the invention are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows: Fig. 1: a block diagram of a first system consisting of several internal combustion engines; and Fig. 2 a block diagram of a second system consisting of several internal combustion engines.

[0018] The invention relates to a method for operating a system of several internal combustion engines and a control device for carrying out the method.

[0019] Fig. Figure 1 shows a highly schematic representation of a first system 1 consisting of several internal combustion engines 2, 3. The in Fig. The internal combustion engines 2 and 3 shown in Figure 1 are coupled in such a way that partial drive power supplied by them is drawn by a common consumer 4. This consumer 4 can be, for example, a hydraulic, electrical, mechanical, or other type of consumer, whose required drive power is supplied by the sum of both internal combustion engines 2 and 3. Fig. In system 1, fuel 5 or 6 is supplied to each of the combustion engines on the one hand, and combustion air 7, 8 is supplied to each of the combustion engines on the other hand, whereby the fuel 5, 6 is burned in the respective combustion engine 2, 3 and exhaust gas 9, 10 is discharged from the respective combustion engine 2, 3. In system 1 of the Fig. Each internal combustion engine 2, 3 is assigned an individual exhaust aftertreatment unit 11, 12, in which the respective exhaust gas 9, 10 of the respective internal combustion engine 2, 3 undergoes individual exhaust aftertreatment. Accordingly, purified exhaust gas 13, 14 exits the exhaust aftertreatment unit 11, 12. The operation of the internal combustion engine 2, 3 and / or the exhaust aftertreatment unit 11, 12 is controlled and / or regulated by a control unit 15.

[0020] In accordance with the present invention, the system 1 consisting of the coupled internal combustion engines 2, 3 is operated in such a way that, by providing the power requested by the common consumer 4, an individual operating point is determined for each running internal combustion engine 2, 3 of the system 1 and the respective internal combustion engine 2, 3 is operated in this determined, individual operating point, namely in such a way that minimal operating costs are incurred for the system 1 while complying with specified emission limits.

[0021] Operating costs can include operating material costs and maintenance costs. Operating material costs include, in particular, the fuel costs of the fuel 5, 6 burned in the internal combustion engines 2, 3. Furthermore, operating material costs also include the costs for a reducing agent and / or absorbing agent required in the exhaust aftertreatment systems 11, 12 for the exhaust aftertreatment of the exhaust gas 9, 10 leaving the internal combustion engines 2, 3.

[0022] Thus, if the exhaust aftertreatment devices 11, 12 are, for example, SCR catalysts, ammonia or an ammonia precursor substance, such as urea, guanidium formate, ammonium carbamet, ammonium formate or the like, is required as a reducing agent for exhaust aftertreatment.

[0023] Urea decomposes at high temperatures into isocyanic acid and ammonia according to the following equation (NH2)2CO → NH3 + HNCO

[0024] Isocyanic acid further decomposes with water contained in the exhaust gas according to the following equation. HNCO + H2O → NH3 + CO2

[0025] The complete hydrolysis of one mole of urea produces two moles of ammonia and one mole of carbon dioxide according to the following equation. (NH2)2CO + H2O → 2NH3 + CO2

[0026] This makes ammonia available as a reducing agent for exhaust gas aftertreatment in an SCR catalyst through the hydrolysis of urea.

[0027] According to the following equation, one mole of ammonia is required to react one mole of nitric oxide. 4NO + 4NH3 + O2 → 4N2 + 6H2O

[0028] The ratio between ammonia and nitrogen oxides is referred to as the feed ratio α=NH3 / NOx, where a feed ratio α=1 for an ideal catalyst means that all nitrogen oxides are reduced, i.e., a 100% NOx conversion is achieved. For the NOx conversion X NOx This applies X NOx = (C NOx,0 -C NOx ) / C NOx,0

[0029] Then, if, for example, reducing agents increase in relation to fuel costs, operating points of running internal combustion engines can be shifted so that less reducing agent is required in the exhaust aftertreatment devices 11, 12 due to reduced raw emissions.

[0030] Similarly, reducing agents or absorbents for exhaust aftertreatment are required in CH2O oxidation catalysts, NO oxidation catalysts, NOx storage catalysts, CH4 oxidation catalysts, desulfurization plants, or the like, and these determine the operating costs. As explained above, the individual operating points for the running internal combustion engines 2, 3 of system 1 are determined in such a way that minimal operating costs, in particular minimal operating costs, are incurred for the entire system 1.

[0031] In addition to the operating costs, maintenance costs are also preferably taken into account when determining the individual operating points for the internal combustion engines 2, 3 of system 1.

[0032] Maintenance and service work is required at defined intervals for the internal combustion engines 2 and 3, as well as for the exhaust aftertreatment systems 11 and 12. This work also affects the operating costs of system 1. Maintenance and service intervals depend, among other things, on the operating points at which the internal combustion engines 2 and 3 are currently and have previously been operated. Therefore, maintenance and service costs are preferably also taken into account when determining the individual operating points for the operating internal combustion engines 2 and 3 of system 1.

[0033] In the operation of system 1, consisting of several coupled internal combustion engines 2, 3, at least one running internal combustion engine of system 1 is operated at an individual operating point such that the raw NOx emissions and / or the raw CO2 emissions and / or the boost pressure and / or the fuel injection pressure and / or the compression ratio and / or the fuel-air ratio and / or the exhaust gas temperature of this internal combustion engine differs from the corresponding operating parameter of any other running internal combustion engine 2, 3 of system 1. As already explained, emission limits are taken into account while minimizing operating costs.

[0034] A particularly advantageous embodiment is one in which at least one of these operating parameters of at least one running internal combustion engine deviates from the corresponding operating parameter of the or any other running internal combustion engine by at least 10%, preferably by at least 20%, most preferably by at least 50%.

[0035] In the preferred embodiment of the invention, an individual operating point is determined for each internal combustion engine 2, 3 of the system 1, consisting of coupled internal combustion engines, depending on the operating costs of the internal combustion engines 2, 3, the operating costs of the exhaust aftertreatment devices 11, 12, the maintenance costs of the internal combustion engines 2, 3, and the maintenance costs of the exhaust aftertreatment devices 11, 12. This is achieved such that minimal operating costs result while providing the power required by the common consumer 4, which is to be supplied as a total power output by the internal combustion engines 2, 3, and while complying with binding emission limits for the system 1. This enables particularly economical operation of a system consisting of several coupled internal combustion engines.

[0036] According to an advantageous further development of the invention, the determination of the individual operating point for each of the running internal combustion engines 2, 3 of the system 1 is further carried out taking into account a reserve power to be maintained as well as a load switching capability to be maintained of the system 1.

[0037] In this way, in addition to the power required by each common electrical consumer 4, a reserve power is to be provided by the internal combustion engines 2 and 3 of system 1. Furthermore, dynamically changing loads can be taken into account in order to select the individual operating points of the internal combustion engines 2 and 3 so that, ultimately, system 1 exhibits good load switching capability. According to this further development, the individual operating points of the internal combustion engines 2 and 3 of system 1 are therefore determined taking into account the required power, the reserve power, the desired load switching capability, and the emission limits to be met, while minimizing the operating costs of the overall system 1.

[0038] A particularly advantageous embodiment of the invention is one in which, when determining the individual operating points for the running internal combustion engines 2, 3, priorities are taken into account that can, for example, be specified by the operator. Thus, fuel costs can be given a higher priority than maintenance costs, so that fuel costs have a greater influence on the determination of the individual operating points for the internal combustion engines 2, 3 than maintenance costs. Furthermore, individual internal combustion engines can be prioritized for the operation of system 1, namely taking into account the remaining drive power that can be provided by the same engine until the next service interval.

[0039] For example, if the remaining drive power available for one internal combustion engine of system 1 is low due to its recent load, whereas the remaining drive power available for other internal combustion engines of system 1 is higher due to a lower recent load, then the internal combustion engines with the higher available remaining drive power can be given higher priority for further operation in order to increase the possible operating time of system 1 until the next required service.

[0040] The above procedure is carried out fully automatically by the control unit 15, which controls the operation of the internal combustion engines 2, 3 and / or the operation of the exhaust aftertreatment systems 11, 12. For this purpose, the control unit 15 exchanges data with the internal combustion engines 2, 3 and with the exhaust aftertreatment systems 11, 12, as indicated by the dashed arrows. Furthermore, the control unit 15 exchanges data with each common consumer 4, for example, to determine the power demanded by each common consumer 4.

[0041] The control device 15 comprises means for carrying out the method, consisting of hardware and software components. The hardware components are interfaces for exchanging data with the assemblies involved in carrying out the method according to the invention. These hardware components also include a memory for data storage and a processor for data processing. The software components are program modules for carrying out the method according to the invention.

[0042] A particularly preferred embodiment of the invention is one in which the internal combustion engines 2, 3 of system 1 provide partial drive power, feed this power into a DC network, and make it available to a common consumer 4. In this case, the operating points for the internal combustion engines 2, 3 can be freely selected independently of the on-board network frequencies typical for AC generators, which allows the internal combustion engines and thus the entire system 1 to be operated particularly efficiently.

[0043] Internal combustion engines can be diesel engines, gasoline engines, or turbomachines.

[0044] The invention is particularly preferred for use in a propulsion system for a ship, in which the internal combustion engines 2, 3 are typically designed as marine diesel engines powered by heavy oil.

[0045] Heat exchangers can be arranged downstream of the internal combustion engines 2, 3, in particular downstream of the exhaust gas catalysts 11, 12, to utilize exhaust gas heat for heating a fluid. This can further increase the efficiency of the system 1 consisting of internal combustion engines 2, 3.

[0046] In System 1 of the Fig. In 1, each of the internal combustion engines 2 and 3 has an individual exhaust aftertreatment device 11, 12 downstream. In contrast, Fig. 2 a system 21 consisting of several internal combustion engines 22, 23, each providing partial drive power for a common consumer 24, wherein exhaust gas 29, 30 of the internal combustion engines 22, 23, which is produced during the combustion of fuel 25 or 26 in the presence of combustion air 27, 28 in the internal combustion engines 22, 23, is routed through a common exhaust aftertreatment device 31, from which purified exhaust gas 32 flows. A control device 33 controls the operation of the two internal combustion engines 22, 23 and the common exhaust aftertreatment device 31, as described in the exemplary embodiment of Fig.1 described, wherein, by providing the power requested by the common consumer 24 for the internal combustion engine 22, 23, an individual operating point is determined and the respective running internal combustion engine 22, 23 is operated in this individual operating point, namely in such a way that minimal operating costs are incurred for the system 21 while complying with emission limits, preferably by maintaining a reserve power and / or a desired load switching capability.

[0047] It is therefore in line with the invention to determine optimal, individual operating points for the internal combustion engines of a system consisting of several coupled internal combustion engines, not in relation to the optimum of the respective internal combustion engine as such, but in relation to the optimum of the overall system, so that minimal operating costs are incurred with regard to operating resources and maintenance costs, whereby individual factors and internal combustion engines can be prioritized depending on the user. Emission limits to be met, reserve power to be maintained, and the desired dynamics of the load-sensing capability of the overall system are taken into account. In particular, the consideration of dynamic reserves for the load-sensing capability of the internal combustion engines, and thus of the overall system, allows for particularly advantageous operation of the system consisting of several internal combustion engines. Reference symbol list 1 system 2 Internal combustion engine 3 Internal combustion engine 4 consumers 5 Fuel 6 Fuel 7 Charge air 8 Charge air 9 Exhaust gas 10 Exhaust gas 11 Exhaust aftertreatment system 12 Exhaust aftertreatment system 13 Exhaust gas 14 Exhaust gas 15 Control unit 21 System 22 Internal combustion engine 23 Internal combustion engine 24 consumers 25 Fuel 26 Fuel 27 Charge air 28 Charge air 29 Exhaust gas 30 Exhaust gas 31 Exhaust aftertreatment system 32 Exhaust gas 33 Control unit

Claims

[1] Method for operating a system (1; 21) of several internal combustion engines (2, 3; 22, 23), wherein the internal combustion engines (2, 3; 22, 23) are coupled such that partial drive powers provided by running internal combustion engines (2, 3; 22, 23) are taken off by at least one common consumer (4; 24), and wherein the internal combustion engines (2, 3; 22, 23) are operated such that the total drive power provided by the running internal combustion engines (2, 3; 22, 23), which corresponds to the sum of the partial drive powers, is at least equal to the power required for the common consumer or consumers (4; 24), characterized by, that, by providing the requested power for each running internal combustion engine (2, 3; 22, 23), an individual operating point is determined and the respective internal combustion engine (2, 3; 22, 23) is operated at this individual operating point, namely in such a way that the system (1; 21) incurs minimal operating costs while complying with emission limits, wherein an individual operating point is determined for each internal combustion engine (2, 3; 22, 23) in such a way that the system (1; 21) incurs minimal operating costs from operating costs and maintenance costs. [2] Method according to claim 1, characterized by , that at least one running internal combustion engine (2, 3; 22, 23) of the system (1; 21) is operated at an individual operating point such that the NO X-raw emissions and / or the raw CO2 emissions and / or the boost pressure and / or the fuel injection pressure and / or the compression ratio and / or the fuel-air ratio and / or the exhaust gas temperature of this internal combustion engine differs from the corresponding operating parameter of the or any other running internal combustion engine (2, 3; 22, 23) of the system (1; 21). [3] Method according to claim 2, characterized by that at least one of these operating parameters deviates from the corresponding operating parameter of the or any other running internal combustion engine by at least 10%, preferably by at least 20%, most preferably by at least 50%. [4] Method according to any one of claims 1 to 3, characterized by, that each internal combustion engine (2, 3) of the system (1) is connected to an individual exhaust aftertreatment device (11, 12) in which the exhaust gas of the respective internal combustion engine is subjected to individual exhaust aftertreatment, or that several internal combustion engines (22, 23) of the system (21) are connected to a common exhaust aftertreatment device (31) in which the exhaust gas of the respective internal combustion engines is subjected to common exhaust aftertreatment, and that for each operating internal combustion engine (2, 3; 22, 23) an individual operating point is determined such that, depending on the cost of the fuel to be burned in the internal combustion engine (2, 3; 22, 23) and depending on the cost of the reducing agent and / or absorbing agent to be used for exhaust aftertreatment in the exhaust aftertreatment system (11, 12; 31) for the system (1;21) while complying with emission limits and providing the requested performance, minimal operating costs for fuel and reducing agent and / or absorbenant are incurred. [5] Method according to any one of claims 1 to 4, characterized by , that, by providing the requested power and maintaining a reserve power and / or load switching capability for each internal combustion engine (2, 3; 22, 23), an individual operating point is determined and the respective internal combustion engine (2, 3; 22, 23) is operated at this individual operating point, namely in such a way that the system (1; 21) incurs minimal operating costs while complying with emission limits. [6] Method according to any one of claims 1 to 5, characterized by , that when determining the individual operating points for the internal combustion engine (2, 3; 22, 23) priorities are taken into account. [7] Method according to claim 6, characterized by, that the prioritizations of the internal combustion engines (2, 3; 22, 23) depend on fuel costs and / or maintenance costs and / or on their remaining drive power available until the next service date. [8] Method according to any one of claims 1 to 7, characterized by , that the partial drive powers provided by the internal combustion engines (2, 3; 22, 23) of the system (1; 21) are fed into a direct current network and made available to a consumer (4; 24). [9] Control device, characterized by Means for carrying out the method according to any one of claims 1 to 8.

Images