CN102046946B - For balancing the method and system of cylinder of diesel engine - Google Patents

Abstract

A kind of for balancing the method for the cylinder (3) of diesel engine (2), in the method, limit the initial time of the combustion process of each cylinder (3), and the initial time of the restriction of combustion process and specific setting value are compared.If the initial time of the combustion process limited is different from this setting value, then change the initial time injected fuel in cylinder (3).In addition, measure the delivery temperature of each cylinder and change the endurance injected fuel in cylinder (3) based on this delivery temperature, the output produced by cylinder with equilibrium.

Description

Method and system for balancing diesel engine cylinders

technical field

The invention relates to a method for balancing a cylinder of a diesel engine. The invention also relates to a system for balancing cylinders of a diesel engine.

Background technique

In a piston engine, there are differences in power generation between the different cylinders of the engine. This difference is, for example, a variation in the operation of the injection systems over their lifetime due to wear of the parts of the injection systems. The difference in cylinder power can negatively affect engine operation, for example, increasing the load on the crank and other parts, and the vibration of the engine will also increase. Therefore, an attempt is made to maintain a balance between the cylinders, ie to make the combustion process as similar as possible between the cylinders. Problems related to power differences between cylinders occur more commonly in diesel engines with a common pressure supply system, where heavy oil is used as fuel.

Contents of the invention

It is an object of the present invention to provide an improved solution for balancing cylinder loads in a diesel engine.

The objects of the invention are mainly achieved as disclosed in claims 1 and 11 appended hereto. In the present invention, the start times of the combustion processes in the individual cylinders are defined and compared with specific setpoints. If the defined start time of the combustion process differs from the setpoint, the start time of the fuel injection is changed. Additionally, the exhaust temperature of each cylinder is measured, and the duration of fuel injection into the cylinder is varied based on the exhaust temperature to equalize the power produced by the cylinder.

The invention achieves considerable advantages. By individually adjusting the start of the combustion process and the duration of fuel injection into each cylinder, power differences between the cylinders will be balanced. Power differences between cylinders due to wear of parts in the injection system are compensated so that the operation of the cylinders remains optimal throughout the lifetime of the parts. In addition, load changes due to different types of fuel or changes in the quality of the same fuel can be compensated so that these load changes have as little effect as possible on engine operation. The system can also be applied to the maintenance of parts of the fuel injection system, such as injectors. The control unit of the system may be arranged to monitor changes in the setpoint of a component, whereby if the setpoint exceeds a limit value indicating that the component needs to be replaced, the control unit notifies the need. Furthermore, since it is not necessary to provide individual injector adjustments for each common pressure supply system, less expensive injectors can be used in the injection system.

detailed description

The invention will be explained in more detail below by way of example with reference to the accompanying drawing, which schematically illustrates a system according to the invention.

The figures depict an example of a system 1 for balancing a cylinder 3 of a diesel engine according to the invention. The system 1 is arranged in combination with a piston engine 2 . The engine 2 is a large diesel engine, which is used, for example, as a main engine and an auxiliary engine in ships or power plants. The engine 2 has a common pressure supply system 4 for supplying fuel into the cylinders 3 . For example, heavy oil is used as fuel in the engine 2 . The injection system 4 is controlled electrically.

The engine comprises several cylinders 3 each having an injector 5 for injecting fuel into the cylinder's combustion chamber. The supply system comprises a common rail 9 for pressurized fuel. The injectors 5 are connected to a common rail 9 . The fuel supply system 4 includes a fuel source 6 (eg, a fuel tank) and a low-pressure pump 11 and a high-pressure pump 12 for feeding fuel from the fuel source 6 into the common rail 9 . Each injector 5 is in flow communication with the common rail 9 through a fuel passage 10 .

When the engine 2 is running, fuel is pumped by the low-pressure pump 11 from the fuel tank 6 to the high-pressure pump 12 along the supply channel 13 , and then pumped by the high-pressure pump 12 into the common rail 9 via the supply channel 13 . Fuel is led from the common rail 9 to the injectors 5 . Fuel is injected into the cylinder 3 by the injector 5 at the desired moment.

The engine comprises a system 1 by which the cylinders 3 are balanced, ie the combustion process is kept as similar as possible between the cylinders 3 . The system 1 comprises a control unit 14 controlling the injection of fuel from the injector 5 to the cylinder 3 . The control unit 14 defines the starting instants for injecting fuel into the individual cylinders. The control unit 14 adjusts the starting moment of the fuel injection. Furthermore, the control unit 14 controls the duration of the fuel injection.

The control unit 14 defines the start moment of the combustion process, ie the crank angle in each cylinder 3 corresponding to the start of the combustion. The start moment of the combustion process can be defined based on a positional measurement of the cylinder pressure (the crank angle corresponding to the cylinder pressure indicates the start of the combustion process) or based on a measurement of the torsional vibration of the crank. In both methods, the angle of rotation can be measured by an angle sensor 16 suitable for this purpose. The measurement data of the angle sensor 16 are transmitted to the control unit 14 .

In a method based on positional measurement of the cylinder pressure, the cylinder pressure in the individual cylinders 3 is measured by a suitable measuring device 15, such as a pressure sensor, a knock sensor (acceleration sensor) or a strain gauge, which is connected to the cylinder 3 are set in combination. Cylinder pressure can also be measured using ionization measurements. The measured data on the cylinder pressure and on the angle of rotation of the crank are transmitted to the control unit 14 . The control unit 14 defines the starting instant of the combustion process in the individual cylinder 3 on the basis of the measurement data of the cylinder pressure and the crank angle of rotation. As soon as the measured cylinder pressure reaches a value indicating that the combustion process in cylinder 3 has started, a corresponding crank angle will be defined. The start of the combustion process is indicated by, for example, a change in the angular coefficient that occurs in the cylinder pressure increase curve. The starting moment of the combustion process can also be defined by measuring the maximum cylinder pressure.

When defining the starting moment of the combustion process on the basis of torsional vibration measurements, the system includes a measuring device for measuring the torsional vibrations of the crankshaft. An angle sensor 16 that measures the rotational angle of the crank may be used as the measuring means, whereby measurement data regarding the magnitude of the torsional vibration and the rotational angle at which the torsional vibration occurs is received. This measurement data is transmitted to the control unit 14 . On the basis of this measurement data, the control unit 14 defines the starting instant of the combustion process in the individual cylinder 3 .

Once the start time of the combustion process has been defined, the control unit 14 compares the defined start time of the combustion process with a specific setpoint. This set value can be predetermined, for example based on the engine load and the pressure of the common rail 9 . If the defined start time of the combustion process differs from this setpoint, the control unit 14 changes the start time of the fuel injection individually for each cylinder. The starting moment of the fuel injection is changed so that the starting moment of the combustion process is close to the set value. Since the starting moment of the fuel injection coincides quite precisely with the starting moment of the combustion process, it is possible to change the starting moment of the fuel injection to be the same as the set value of the starting moment of the combustion process.

Furthermore, in order to equalize the power produced by the cylinders, the control unit 14 varies the duration of fuel injection into the cylinders 3 . The duration of fuel injection is varied individually for each cylinder. Once the above adjustments are made to the start of fuel injection, the duration of fuel injection is changed, ie the start of fuel injection is as desired. The duration of fuel injection into the cylinders can be varied so that the power produced by the individual cylinders 3 is equalized. The duration of fuel injection can be varied based on the exhaust gas temperature of cylinder 3 or based on measurements of torsional vibrations of the crank.

If the duration of fuel injection is adjusted based on the exhaust gas temperature, the system 1 includes a temperature sensor 18 associated with each cylinder for measuring the exhaust gas temperature of the cylinder. A temperature sensor 18 is mounted on an exhaust pipe 19 of the cylinder. The measurement data of the temperature sensor 18 are transmitted to the control unit 14 . The control unit 14 varies the duration of fuel injection based on the measured exhaust gas temperature. The duration of fuel injection is varied in order to equalize the power produced by cylinders 3 . The control unit 14 can vary the duration of the fuel injection so that the exhaust gas temperatures in the individual cylinders 3 are equalized. Compare the measured discharge temperature with the setpoint. If the measured value of the exhaust temperature of one of the cylinders 3 is different from the set value, the duration of fuel injection into said cylinder is changed so that its exhaust temperature is at its set value. An average value or a predetermined value of the measured exhaust gas temperatures can be used as a setpoint value for the exhaust gas temperature, the magnitude of which can depend, for example, on the load on the engine or on the fuel used. If the exhaust gas temperature is too low, extend the duration of fuel injection. Similarly, if the exhaust temperature is too high, the duration of fuel injection is shortened.

If the duration of the fuel injection is defined on the basis of measurements of the torsional vibrations of the crank, the system comprises measuring means for measuring the torsional vibrations of the crank. The angle sensor 16 that measures the rotation angle of the crank may be used as the measurement means, whereby measurement data regarding the magnitude of the torsional vibration and the rotation angle at which the torsional vibration occurs are received at the same time. This measurement data is transmitted to the control unit 14 . The control unit 14 individually varies the duration of fuel injection into each cylinder such that torsional vibrations of the crank are minimized.

The duration of fuel injection can be varied using the above two methods (ie, cylinder based exhaust temperature and crank based torsional vibration). The duration of the fuel injection can then be adjusted by utilizing both measurements simultaneously or using one measurement first (for example the measurement of exhaust gas temperature) with the other measurement as a backup measurement. This other measure can be used when needed, for example when the main measure was unsuccessful.

The invention is not limited to the embodiments shown, but several variants are conceivable within the scope of the appended claims. The starting moment of the combustion process can be defined by measuring the current in the solenoid valve of the injector 5 or by measuring the fuel injection pressure. The fuel injection pressure can be measured by a pressure switch or a pressure sensor arranged in the common rail 9 or in the fuel passage 10 of the injector.

For example, according to one embodiment, the duration of fuel injection into the cylinders 3 is varied to equalize the power produced by the cylinders based on the exhaust gas temperature and on the torsional vibrations. In this way, the accuracy of the adjustment can be further increased, as long as the duration of the injection is taken into account.

Furthermore, the method includes a stage of evaluating the correctness of the measurement of the exhaust gas temperature and determining a change in the duration of the fuel injection based on torsional vibrations if the measurement of the exhaust gas temperature of the cylinder is incorrect. Such an erroneous measurement of the exhaust gas temperature is, for example, a failure of the sensor for measuring the exhaust gas temperature or the deviation of the exhaust gas temperature 18 of the cylinder from the preset temperature value or from the average value of the exhaust gas temperature of the cylinder. big case. This offers the advantage that faulty states of sensors affecting the adjustment of the duration of the injection can be detected and the engine does not necessarily have to be shut down. In this case, if the exhaust gas temperature 18 of the cylinder deviates by more than 50% relative to the preset temperature value or relative to the average value of the exhaust gas temperature, the time limit for the change of the duration of fuel injection into the cylinder 3 is defined One way is based on torsional vibrations. For example, the predetermined temperature value for a specific load may be a reference value recorded in the regulation system for the specific load and speed. Another way of limiting the variation in the duration of fuel injection into a cylinder 3 if the exhaust gas temperature 18 of the cylinder deviates by more than 10% relative to a preset temperature value or relative to the average value of the exhaust gas temperature is based on torsional vibration. This offers the advantage that the determination methods affecting the adjustment of the duration of the injection can be replaced immediately, so that the one determination method to be predominantly used (in this case the method based on the exhaust gas temperature) can be selected. These two approaches can be realized by changing the function of the control unit 14 of the system.

Claims (18)

1. A method for a cylinder (3) of a balanced diesel engine (2), the method comprising the following steps: Defining the starting moment of the combustion process in each cylinder (3), comparing the defined start moment of the combustion process with a specific setpoint, and changing the start moment of fuel injection into said cylinder (3) if the defined start moment of said combustion process differs from said set value, It is characterized in that, Measure the exhaust gas temperature of each cylinder (18), varying the duration of fuel injection into said cylinders (3) based on the exhaust gas temperature to equalize the power produced by said cylinders (3), and The torsional vibration of the engine crank is measured and the duration of fuel injection into the cylinders (3) is varied based on the exhaust gas temperature and the torsional vibration to equalize the power produced by the cylinders. 2. A method according to claim 1, characterized by extending the duration of fuel injection associated with a cylinder if the exhaust gas temperature is too low and shortening the duration of the fuel injection associated with the cylinder if the exhaust gas temperature is too high duration of fuel injection. 3. A method according to claim 1 or 2, characterized in that the duration of fuel injection into the cylinder (3) is varied such that a desired exhaust gas temperature is achieved. 4. A method according to claim 3, characterized in that an average value or a predetermined value of the measured exhaust gas temperature is used as the setpoint. 5. A method according to claim 1, characterized in that the method further comprises the stage of evaluating the correctness of the measurement of the exhaust gas temperature (18) and if the exhaust gas temperature (18) of the cylinder ) is incorrectly measured, the change in the duration of fuel injection into said cylinder (3) is determined on the basis of torsional vibrations. 6. The method according to claim 1, characterized in that if the exhaust gas temperature (18) of the cylinder deviates from a preset temperature value or deviates from the average value of the exhaust gas temperature of the cylinder (3) , then the variation of the duration of fuel injection into said cylinder (3) is defined based on torsional vibrations. 7. A method according to claim 1, characterized in that the location (15, 16) of the cylinder pressure in each cylinder (3) is measured and that the combustion process is defined based on the location measurement of the cylinder pressure the starting moment of . 8. The method according to claim 6, characterized in that the cylinder pressure is measured by a knock sensor, strain gauge or pressure sensor (15) provided in conjunction with the cylinder (3). 9. The method according to claim 1, characterized in that torsional vibrations of the engine crank are measured and the starting moment of the combustion process is defined based on the torsional vibration measurements. 10. A system (1) for balancing cylinders (3) of a diesel engine (2), comprising a control unit (14) and a device to be installed in conjunction with each cylinder (3) for measuring the exhaust gas temperature of said cylinder temperature sensor (18), the control unit (14) is configured to perform the following operations: Defining the starting moment of the combustion process in each cylinder (3), comparing the defined start moment of the combustion process with a set value, and changing the start moment of fuel injection into said cylinder (3) if the defined start moment of said combustion process differs from said set value, characterized in that the control unit (14) is arranged to vary the duration of fuel injection into the cylinders (3) based on the measurement of the exhaust gas temperature in order to equalize the power produced by the cylinders, and The system comprises means (16) for measuring torsional vibrations of the crank, and the control unit (14) is arranged to vary the injection of fuel into the cylinders (3) based on the exhaust gas temperature and torsional vibrations duration to equalize the power produced by the cylinders (3). 11. A system according to claim 10, characterized in that the control unit is arranged to prolong the duration of fuel injection associated with a cylinder when the exhaust gas temperature is too low and to prolong the duration of fuel injection when the exhaust gas temperature is too low. High shortens the duration of fuel injection associated with the cylinder. 12. A system according to claim 10 or 11, characterized in that the control unit (14) is arranged to vary the duration of fuel injection such that the desired temperature of the exhaust gas of the cylinder (3) is achieved set value. 13. The system of claim 12, wherein the desired setpoint is an average or predetermined value for the exhaust gas temperature. 14. A system according to claim 10, characterized in that the system further comprises means for evaluating the correctness of the measurement of said exhaust gas temperature (18), and if said exhaust gas temperature (18) of said cylinder If the measurement of , the change in the duration of fuel injection into the cylinder (3) is defined on the basis of torsional vibrations. 15. The system according to claim 14, characterized in that the control unit (14) is configured to deviate from a preset temperature value or deviate from the cylinder (3 The duration of fuel injection into the cylinder (3) is varied based on torsional vibrations in the case of the average value of the exhaust gas temperature. 16. A system according to claim 10, characterized in that the system (1) comprises means (15, 16) for measuring the position of the cylinder pressure in each cylinder (3), and that the control unit ( 14) Arranged to define a starting moment of said combustion process based on said position measurement of said cylinder pressure. 17. A system according to claim 16, characterized in that said means for measuring the location of said cylinder pressure comprises a knock sensor, a strain gauge or a pressure sensor (15) provided in conjunction with said cylinder . 18. A system according to claim 16 or 17, characterized in that the means for measuring the position of the cylinder pressure comprises an angle sensor (16) measuring the rotation angle of the engine crank.