Abstract:
Control systems comprising electronic control modules ( 104, 106 ) may be configured to control operation of a dual fuel internal combustion engine ( 1 ). In case of a failure of an electronic control module ( 104, 106 ), the dual fuel internal combustion engine ( 1 ) may interrupt operation. The disclosed control system and method may maintain operation of the dual fuel internal combustion engine ( 1 ) when a malfunction within an operation mode of the dual fuel internal combustion engine ( 1 ), particularly when an electronic control module ( 104, 106 ) fails, is detected.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally refers to control systems and control methods for dual fuel internal combustion engines and more particularly to maintaining operation of the dual fuel internal combustion engine when a malfunction within an operation mode is detected. 
       BACKGROUND 
       [0002]    When controlling internal combustion engines, self-redundant control systems may ensure continuous operation of the internal combustion engines in particular for marine applications. Self-redundant control systems commonly monitor their own functionality as well as the operation of the controlled internal combustion engine. 
         [0003]    As an example for a single fuel operated internal combustion engine having multiple cylinder banks, EP 2 388 460 A1 discloses a common rail fuel system with independently controlled fuel supply to each bank. Control modules for each of the cylinder banks are configured to communicate with each other thereby providing a self-redundant control system. Thereby, the control modules are operated as master control modules and slave control modules. 
         [0004]    For a dual fuel internal combustion engine, U.S. Pat. No. 6,073,592 discloses a control system comprising a master electronic control module controlling the diesel fuel mode functions, and one or more slave electronic control modules controlling the gaseous fuel functions of the dual fuel engine. The master electronic control module communicating with the one or more slave electronic control modules drives the diesel fuel injectors, processes sensor data required for diesel operation, monitors and protects the engine during diesel operation, starts and stops the engine, and processes operator input. The remaining electronic control functions are allocated among the slave electronic control modules, which include controlling the solenoid gas admission valves. The master electronic control module transitions operation to the liquid fuel mode in the event of a failure of any gaseous fuel mode specific components, or if communication between the master electronic control module and the slave electronic control modules fails. Therefore, operation of the engine may be continued even if one or the entire slave electronic control module fails. 
         [0005]    WO 2008/104764 A1 discloses an apparatus for controlling dual fuel supply to a fuel injected engine having an electronic engine management system that supplies a primary injector control signal to each of primary fuel injectors. Furthermore, the apparatus comprises an emulator that emulates the electrical characteristics of a primary injector, and a controller that processes a monitor signal to derive an alternative control signal which is used to control the primary fuel supply or a mixture of the primary fuel and a secondary fuel. 
         [0006]    A further example of a control system for a bi-fuel engine is known from US 2011/0202256 A1. 
         [0007]    The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems. 
       SUMMARY OF THE DISCLOSURE 
       [0008]    According to an aspect of the present disclosure, a control system for a dual fuel internal combustion engine operable in a liquid fuel mode using a fuel rack actuator for controlling a liquid fuel amount and a gaseous fuel mode using a gaseous fuel admission valve for controlling a gaseous fuel amount comprises a first electronic control module configured to provide a liquid fuel amount control signal to the fuel rack actuator when controlling the liquid fuel mode, and a second electronic control module configured to provide a gaseous fuel amount control signal to the gaseous fuel admission valve when controlling the gaseous fuel mode and configured to provide a back-up liquid fuel amount control signal to the fuel rack actuator when controlling the liquid fuel mode. 
         [0009]    According to another aspect of the present disclosure, an internal combustion engine operable in a liquid fuel mode and a gaseous fuel mode comprises a liquid fuel injection system including a main injection system configured to inject liquid fuel during the liquid fuel mode, an ignition injection system configured to inject liquid fuel during the gaseous fuel mode, and a fuel rack actuator configured to control the amount of injected liquid. The internal combustion engine further comprises a gaseous fuel injection system including a gaseous fuel admission valve for mixing gaseous fuel with compressed air, and a control system as disclosed herein. 
         [0010]    According to another aspect of the present disclosure, a control method for an internal combustion engine operable in a liquid fuel mode using a fuel rack actuator for controlling a liquid fuel amount and a gaseous fuel mode using a gaseous admission valve for controlling a gaseous fuel amount comprises the steps of providing a liquid fuel amount control signal to the fuel rack actuator when controlling the liquid fuel mode by a first electronic control module, and providing a gaseous fuel amount control signal to the gaseous admission valve when controlling the gaseous fuel mode by a second electronic control module and providing a back-up liquid fuel amount control signal to the fuel rack actuator when controlling the liquid fuel mode by the second electronic control module. 
         [0011]    In some embodiments of the control system, the second electronic control module may be configured to provide the back-up liquid fuel amount control signal to the fuel rack actuator when monitoring a malfunction of the liquid fuel amount control signal of the first electronic control module. 
         [0012]    In some embodiments, the control system may comprise a monitoring connection line between the first electronic control module and the second electronic control module for monitoring the functionality of the first electronic control module with respect to the liquid fuel amount control signal. 
         [0013]    In some embodiments of the control system, the first electronic control module may be further configured to switch the dual fuel internal combustion engine from the gaseous fuel mode into the liquid fuel mode when monitoring a malfunction of the gaseous fuel amount control signal of the second electronic control module. 
         [0014]    In some embodiments, the control method may further comprise providing the back-up liquid fuel amount control signal to the fuel rack actuator when monitoring a malfunction of the liquid fuel amount control signal of the first electronic control module. 
         [0015]    In some embodiments, the control method may further comprise monitoring the functionality of the first electronic control module and the second electronic control module. 
         [0016]    In some embodiments, the control method may further comprise switching the internal combustion engine from the gaseous fuel mode into the liquid fuel mode when monitoring a malfunction of the gaseous fuel amount control signal of the second electronic control module. 
         [0017]    Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  shows an exemplary schematic diagram of a dual fuel internal combustion engine; 
           [0019]      FIG. 2  shows an exemplary block diagram illustrating controlling the dual fuel internal combustion engine of  FIG. 1 ; 
           [0020]      FIG. 3  shows a flow diagram illustrating self redundancy with respect to a liquid fuel operation of a dual fuel internal combustion engine; and 
           [0021]      FIG. 4  shows a flow diagram illustrating self redundancy with respect to a gaseous fuel operation of a dual fuel internal combustion engine. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described therein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims. 
         [0023]    The present disclosure may be based in part on the realization that a dual fuel internal combustion engine may be provided with a self-redundant control system also for the case of failure of an electronic control module for the liquid fuel mode by using an electronic control module for the gaseous fuel mode. 
         [0024]    Dual fuel internal combustion engines may be operated with different kinds of fuels like heavy fuel oil (HFO), diesel fuel, gasoline, and natural gas. Specifically, dual fuel internal combustion engines may be operated in either a liquid fuel mode (LFM), for example a diesel fuel mode, and a gaseous fuel mode (GFM), for example a natural gas mode. 
         [0025]    For the LFM, a liquid fuel injector system provides liquid fuel to the charged air within a combustion chamber, where the charge air/liquid fuel mixture is ignited by compression. 
         [0026]    For the GFM, a gaseous fuel such as natural gas is controllably released into an air intake port connected to a cylinder, producing a charge air/gaseous fuel mixture. After a predetermined period of time, a small amount of diesel fuel also referred to ignition fuel may be injected into the cylinder containing the charge air/fuel mixture. The amount of the ignition fuel may be about 3% of the fuel amount injected during the LFM. The compression ignites the diesel fuel, which in turn ignites the charge air/gaseous fuel mixture. 
         [0027]    To operate LFM as well as GFM, a control system for a dual fuel internal combustion engine may control components of the liquid fuel injector system and the gaseous fuel injector system, including gaseous admission valves and ignition fuel injectors. 
         [0028]    Referring to  FIG. 1 , an exemplary schematic diagram of a dual fuel internal combustion engine  1  including an engine unit, an air system, a fuel system, and a control system is shown. 
         [0029]    The engine unit may comprise an engine block  2 , at least one cylinder  4  providing at least one combustion chamber  6  for combusting fuel, a piston  8 , and a crank-shaft  10  connected to the piston via a piston rod  12 . The piston  8  may be configured to reciprocate within the cylinder  4 . 
         [0030]    The air system may comprise an inlet valve  42  fluidly connected to the at least one combustion chamber  42 , and an outlet valve  70  also fluidly connected to the at least on combustion chamber  6 . The inlet valve  42  may be configured to enable injection of compressed charge air and/or a mixture of compressed charge air and gaseous fuel into the at least one combustion chamber  6 . After combusting the liquid fuel or gaseous fuel, the exhaust may be released out of the at least one combustion chamber  6  via the outlet valve  70  into an associated exhaust gas system (not shown) for treating the exhaust gas. 
         [0031]    The fuel system may include a gaseous fuel tank  14  for storing the gaseous fuel, for instance natural gas, and a liquid fuel tank unit  16 , which may include a first liquid fuel tank  18  for storing, for example HFO, and a second liquid fuel tank  20  for storing, for example diesel fuel. 
         [0032]    The fuel system may further comprise a liquid fuel injection system  30 , a gaseous fuel injection system  40 , and an ignition fuel injection system  50 . 
         [0033]    The liquid fuel injection system  30  may be configured to inject liquid fuel originating from the liquid fuel tank unit  16  into the at least one combustion chamber  6 . The liquid fuel injector  32  may be supplied with HFO from the first liquid fuel tank  18  or with diesel fuel from the second liquid fuel tank  20 . 
         [0034]    The liquid fuel injection system  30  may comprise a liquid fuel injector  32  having a liquid fuel injector nozzle  34  fluidly communicating with the at least one combustion chamber  6  and a fuel rack actuator  36  configured to control the amount of liquid fuel provided to the liquid fuel injector  32 . The fuel rack actuator  36  may be connected to the liquid fuel injector  32  via a rack  38  for controlling the amount of injected liquid fuel. 
         [0035]    The gaseous fuel injection system  40  may be configured to inject gaseous fuel originating from the gaseous fuel tank  14  into the at least one combustion chamber  6 . The gaseous fuel injection system  40  may include a gas admission valve  44 , for instance a solenoid gas admission valve, which may be arranged upstream of the inlet valve  42  and may be configured to mix gaseous fuel originating from the gaseous fuel tank  14  with compressed charge air. The mixture of gaseous fuel and compressed charge air may be injected into the at least one combustion chamber  6  via the inlet valve  42 . 
         [0036]    The ignition fuel injection system  50  may be configured to inject a small amount of liquid fuel, preferably diesel fuel, into the at least one combustion chamber  6 . The ignition fuel injection system  50  may include an ignition fuel injector  52  having an ignition fuel injector nozzle  54  being in fluid communication with the at least one combustion chamber  6  and a common rail system  60  receiving diesel fuel from the second liquid fuel tank  20  of the liquid fuel tank  16 . The ignition fuel injector  52  may be supplied with diesel fuel from the common rail system  60 . The common rail system  60  may be embodied by a small sized common rail system known in the art. 
         [0037]    In some embodiments, the ignition fuel injection system  50  may be also configured to inject liquid fuel into the at least one combustion chamber  6  during the LFM. This may prevent the ignition fuel injector nozzle  54  from being blocked by, for example, soot resulting from the combusting process. 
         [0038]    The control system may comprise a control unit  102  including a first electronic control module (FECM)  104  and a second electronic control module (SECM)  106 , and several control lines connected to the respective components of the fuel system. The FECM  104  may be connected to the SECM  106  via a monitoring connection line  120  which may be configured to exchange information between the FECM  104  and the SECM  106  for monitoring each other. 
         [0039]    The FECM  104  may be configured to control the LFM of the dual fuel internal combustion engine  1 . Specifically, the FECM  104  may be connected to the fuel rack actuator  36  via a connection line  112  and a hardware connection, such as a relay  130 . 
         [0040]    For instance, the hardware connection may also be embodied by multiple relays  130 . Furthermore, the hardware connection may be embodied by a diode or by multiple diodes. Diodes may allow a continuous connection between both ECM and the fuel rack actuator without the need to switchover as described below with respect to the relay  130 . 
         [0041]    During the LFM, the FECM  104  may provide a liquid fuel amount control signal to the fuel rack actuator  36  via the connection line  112 . The liquid fuel amount control signal may indicate a desired liquid fuel amount to be injected into the at least one combustion chamber  6 . Furthermore, the liquid fuel amount control signal may further be embodied by a key failure mode. The fuel rack actuator  36  may pivot the rack  38  for adjusting the amount of liquid fuel, for instance HFO originating from the first liquid fuel tank  18  or diesel fuel originating from the second liquid fuel tank  20 . 
         [0042]    In addition, the FECM  104  may be configured to generally control the dual fuel internal combustion engine  1  such as controlling the engine speed and delivered fuel/power from the engine. Moreover, during the GFM, the FECM  104  may be configured to control the ignition fuel injection system  50  via a connection line  114  as explained below with respect to controlling the GFM with the SECM  106 . 
         [0043]    The SECM  106  may be configured to control the GFM of the dual fuel internal combustion engine  1 . Specifically, the SECM  106  may be connected to the gas admission valve  44  via a connection line  110 . Furthermore, the SECM  106  may be connected to the fuel rack actuator  36  via the connection line  110  and the relay  130 . 
         [0044]    During the GFM, the SECM  106  may provide a gaseous fuel amount control signal to the gaseous admission valve  44  via the connection line  110 . The gaseous fuel amount control signal may indicate a desired gaseous fuel amount to be mixed with compressed charge air within the gaseous admission valve  44 , which mixture may be injected into the at least one combustion chamber  6 . Furthermore, the gaseous fuel amount control signal may be embodied by a key failure mode of the SECM, such as loss of connection to, for instance, the CAN bus system. At the same time, the FECM  104  may provide an ignition fuel amount control signal to the ignition fuel injector  52  via the connection line  114 . The ignition fuel amount control signal may indicate a desired ignition fuel amount to be injected into the at least one combustion chamber  6  for igniting the gaseous mixture. For example, the small amount of injected ignition liquid fuel may be about 3% of the amount of injected liquid fuel during the LFM. 
         [0045]    It should be noted that the liquid fuel amount control signal provided by the FECM  104  may be a signal of, for example, 70 V, whereas the gaseous fuel amount control signal provided by the SECM  106  may be a signal of, for example, 108 V. 
         [0046]    The control system may further comprise several sensors for receiving actual parameters of the dual fuel internal combustion engine  1 . For example, the control system may include a cylinder pressure sensor  80  for sensing the pressure within the at least one combustion chamber  6 , a crank shaft speed sensor  82  for measuring the speed of the crank shaft  10 , a charge air pressure sensor  84  for measuring the pressure of the compressed charge air, a gaseous fuel pressure sensor  86  for measuring the pressure of the gaseous fuel, a liquid fuel pressure sensor  88  for measuring the pressure of the liquid fuel, a common rail pressure sensor  90  for measuring the pressure of the liquid fuel within the common rail, and an exhaust gas pressure sensor  92  for measuring the pressure of the exhaust gas released out of the at least one combustion chamber  6 . 
         [0047]    The control system may also comprise further sensors, such as speeding/timing sensors, for which the FECM  104  and the SECM  106  may directly interpret the speed and engine angle information for its own use. 
         [0048]    The sensors  80 ,  82 ,  84 ,  86 ,  88 ,  90 , and  92  may be connected to the control unit  102  via a data link  118  (shown in  FIG. 2 ), for instance a CAN-bus system. Both the FECM  104  and the SECM  106  may be connected to each sensor, for example to receive time critical information and, in order to meet marine regulations, for improving redundancy of the control system. For example, a failure of the CAN link between the FECM  104  and a sensor may not cause the operation of the SECM  106 . 
         [0049]    The desired amount of liquid fuel and/or gaseous fuel to be injected into the at least one combustion chamber  6  may be determined in accordance with the received parameters from the sensors  80 ,  82 ,  84 ,  86 ,  88 ,  90 , and  92 . 
         [0050]    Referring to  FIG. 2 , the control system of the dual fuel internal combustion engine  1  is shown. As can be seen in  FIG. 2 , the FECM  104  is connected to the SECM  106  via the monitoring connection line  120  which may be configured to exchange information between the FECM  104  and the SECM  106 . Thus, the FECM  104  may be able to monitor the gaseous fuel amount control signal of the SECM  106 , and vice versa. 
         [0051]    The relay  130  may be configured to transmit the liquid fuel amount control signal either from the FECM  104  or from the SECM  106  to the fuel rack actuator  36  via a connection line  116 . 
         [0052]    The FECM  104  may be connected to the ignition fuel injection system  50  comprising the ignition fuel injector  52  and the ignition injector nozzle  54 , and the SECM  106  may be connected to the gaseous fuel injection system  40  comprising the gas admission valve  42  and the inlet valve  42 . 
       INDUSTRIAL APPLICABILITY 
       [0053]    In the following, the operation of the dual fuel internal combustion engine  1  is described in connection with  FIGS. 3 and 4 . Specifically,  FIG. 3  relates to a back-up in case of a malfunction of the FECM  104  and  FIG. 4  relates to a back-up system in case of a malfunction of the SECM  106 . 
         [0054]    As shown in  FIG. 3 , the LFM may be controlled by the FECM  104  (step  200 ). Continuously, the SECM  106  may monitor the liquid fuel amount control signal provided by the FECM  104  to relay  130  (step  202 ). The relay  130  may in turn transmit the liquid fuel amount control signal to the fuel rack actuator  36 . The SECM  106  may detect a malfunction of the liquid fuel amount control signal provided by the FECM  104  (step  204 ), for example, the SECM  106  may detect a key failure mode of the SECM  104 , such as a loss of connection of the SECM  104  and the CAN bus system. In this case, the SECM  106  may take over control of the LFM (step  206 ). Therefore, the SECM  106  may provide a back-up liquid fuel amount control signal to the relay  130  which may switchover and may transmit the liquid fuel amount control signal from the SECM  106  to the fuel rack actuator  36 . Then, the LFM may be controlled by the SECM  106  (step  208 ), i.e. the dual fuel internal combustion engine  1  may maintain operation in the LFM. 
         [0055]    Referring to  FIG. 4 , the GFM may be controlled by the SECM  106  (step  300 ). Continuously, the FECM  104  may monitor the gaseous fuel amount control signal provided by the SECM  106  to the gaseous fuel injection system  40 . At the same time, the FECM  104  may provide the ignition fuel amount control signal to the ignition fuel injection system  50  for initiating injection of the ignition fuel for igniting the gaseous mixture within the at least one combustion chamber  6 . The FECM  104  may detect a malfunction of the gaseous fuel amount control signal provided by the SECM  106  (step  302 ). In this case, the FECM  104  may switch the dual fuel internal combustion engine  1  from the GFM into the LFM (step  304 ), i.e. the LFM may be a back-up mode for the GFM. Thus, the dual fuel internal combustion engine  1  may operate in the LFM controlled by the FECM  104  (step  306 ). 
         [0056]    With respect to  FIGS. 3 and 4 , it may be ensured that the dual fuel engine  1  may be continuously operating even if a malfunction of the control signals provided by one of the ECMs  104 ,  106  occurs. This may ensure that, for example, a larger ship may drive at all events to the next harbor for having maintenance of the dual fuel internal combustion engine  1 . 
         [0057]    The liquid fuel amount control signal provided by the FECM  104  may comprise a voltage of 70 V, and the gaseous fuel amount control signal provided by the SECM  106  may comprise a voltage of 108 V. Thus, the SECM  106  providing a higher voltage may take over control of the LFM controlled by the voltage of 70 V. 
         [0058]    During both modes the LFM and the GFM, the control unit  102  may receive engine parameters from the sensors  80 ,  82 ,  84 ,  86 ,  88 ,  90 , and  92  indicative of, for example, the pressure within the at least one combustion chamber  6 . The control unit  102  may then provide these parameters to the FECM  104  and the SECM  106  for controlling operation of the respective fuel mode. 
         [0059]    For example, if a larger ship comprising a dual fuel internal combustion engine  1  is driving in coastal areas, the dual fuel internal combustion engine may be operated in the GFM due to its lower emissions. However, when driving, for example on the high seas, the dual fuel internal combustion engine  1  may be operated in the LFM. 
         [0060]    Furthermore, it should be noted that the control unit  102  may further comprise a third ECM in case controlling a V-type dual fuel engine. It may be understood that the third ECM may control operation of the first cylinder bank, for example the odd numbered cylinders, whereas the FECM  104  may control operation of the second cylinder bank, for example the even numbered cylinders. 
         [0061]    The disclosed control system may be used at internal combustion engines of middle to large size. In particular, the dual fuel internal combustion engine  1  may be sized and configured to be used e.g. in vessels, larger ships or in power plants. Dual fuel internal combustion engines of such a size may have a power output of more than 500 kW/cylinder with 12 to 20 cylinders. 
         [0062]    In general, dual fuel internal combustion engines may further be embodied by a multi-cylinder bank dual fuel engine, which may be selected from the group of engines consisting of radial engines, opposed engines, V-type engines, in-line engines, and W-type engines. 
         [0063]    Herein, the term “internal combustion engine” may refer to internal combustion engines which may be used as main or auxiliary engines of stationary power providing systems such as power plants for production of heat and/or electricity as well as in ships/vessels such as cruiser liners, cargo ships, container ships, and tankers. Fuels for internal combustion engines may include diesel oil, marine diesel oil, heavy fuel oil, alternative fuels or a mixture thereof, and natural gas. 
         [0064]    In addition, the term “internal combustion engine” as used herein is not specifically restricted and comprises any engine, in which the combustion of a fuel occurs with an oxidizer to produce high temperature and pressure gases, which are directly applied to a movable component of the engine, such as pistons or turbine blades, and move it over a distance thereby generating mechanical energy. Thus, as used herein, the term “internal combustion engine” comprises piston engines and turbines. 
         [0065]    Medium speed internal combustion engines may be large stand-alone engines that therefore provide reasonable access to the end sides of the engine block. 
         [0066]    Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.