FI122491B - Method and system for balancing the cylinders in a diesel engine - Google Patents

Description

METHOD AND SYSTEM FOR BALANCING DIESEL ENGINE CYCLES

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

In piston engines, there are differences in power output between the various cylinders of the engine. The differences are due to e.g. wear of the fuel injection system components 10, whereby their function changes during the service life. Differences in power between the cylinders adversely affect engine performance, for example, increasing stress on the crankshaft and other components and vibrations on the engine. Therefore, the aim is to balance the cylinders, i.e. to keep the combustion process as similar as possible between the cylinders. Problems due to cylinder power differences 15 are common in diesel engines equipped with common rail injection systems that use heavy fuel oil as fuel.

The object of the invention is to provide an improved solution for balancing the load on the diesel engine cylinders.

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The objects of the invention are mainly achieved as set forth in claims 1 and 12. In the invention, the start time of the combustion event of each cylinder is determined and compared to the specified start time of the combustion event to a specific setpoint. The fuel injection start time will be modified if the specified start time for the combustion event differs from the set value. In addition, the exhaust gas temperature of each cylinder is measured and the fuel injection duration of the cylinders is modified based on the exhaust gas temperatures to equalize the power produced by the cylinders.

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The invention provides considerable advantages. By adjusting each cylinder o both the start time of the combustion event and the duration of injection,

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power differences between cylinders equalized. The power differences between the cylinders due to the wear of the components 2 of the injection system can be compensated and thus the operation of the cylinders is kept optimal throughout the life of the components. Load changes caused by different types of fuels or fuel quality variations can also be compensated for, which minimizes engine performance. The system can also be used to maintain fuel injection system components, such as injectors. The system control unit can be set to monitor the variation of the component control values, whereby by the control value, the control unit informs about the need to replace the component. In addition, less expensive injectors can be used in the fuel injection system because the injectors do not have to look for individual tuning values for each co-injection system.

The invention will now be described, by way of example, with reference to the accompanying drawing, which schematically illustrates one system according to the invention.

The drawing shows an example of a system 1 according to the invention for balancing engine cylinders 3. The system 1 is mounted in connection with the piston engine 2. Engine 2 is a large diesel engine used, for example, as a main and auxiliary engine for marine 20s or in power plants. The engine 2 is provided with a common-rail injection system 4 for supplying fuel to the cylinders 3. The fuel for the engine 2 is, for example, heavy fuel oil. Injection system 4 is electrically controlled.

The engine comprises a plurality of cylinders 3, each of which is provided with an injector 5 cvj for injecting fuel into the combustion chamber of the cylinder. The supply system comprises one g of common rail 9 for pressurized fuel. The injectors 5 are x connected to a common pressure storage 9. The fuel supply system 4 comprises

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for injecting fuel from a fuel source 6, such as a fuel tank, and a low pressure pump 11 and a low pressure pump 12 from a fuel source 6 into a pressure reservoir 9. Each injector 5 is in fluid communication with the common pressure reservoir C19 through a fuel conduit 10.

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While the engine 2 is running, fuel is pumped from the fuel tank 6 through a low pressure pump 11 through a supply channel 13 to a high pressure pump 12 and further through a high pressure pump 12 through a supply channel 13 to a common pressure storage 9. The fuel is supplied to injectors 5

The engine 2 comprises a system 1 for balancing the cylinders 3, i.e. keeping the combustion process between the cylinders 3 as similar as possible. The system 1 of the system 10 comprises a control unit 14 which controls the injection of fuel from the injectors 5 to the cylinders 3. The control unit 14 determines the time at which the injection of fuel in each cylinder will commence. The control unit 14 controls the time at which the fuel injection begins. In addition, the control unit 14 controls the duration of fuel injection.

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The control unit 14 determines the start time of the combustion event, i.e. the crankshaft angle corresponding to the start of the combustion, in each cylinder 3. The start time of the combustion event can be determined based on the cylinder pressure position measurement (the angle of the cam corresponding to the start of the combustion event) or crankshaft angle. In both methods, the angle of rotation of the crankshaft is measured by a suitable angle sensor 16. The measurement information of the angle sensor 16 is transmitted to the control system 14.

In the method based on the location measurement of the cylinder pressure, the cylinder pressure of each cylinder 3 is measured by a suitable gauge 15, such as a pressure sensor, a knock sensor (accelerometer) or a strain gauge sensor fitted to the cylinder 3. Cylinder pressure can also be measured with

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tiomittauksella. Measurement data g 30 for cylinder pressure and crankshaft rotation angle is transmitted to the control unit 14. The control unit 14 determines the time at which the combustion event of each cylinder 3 will start, the cylinder pressure and crankshaft

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based on measurement data of the dys angle. When the measured cylinder pressure reaches a value 4 indicating that the combustion event in cylinder 3 has begun, the corresponding crankshaft angle is determined. The onset of the combustion event is indicated, for example, by a change in the slope of the cylinder pressure rise curve. The start time of the combustion event can also be determined by measuring the maximum cylinder-5 pressure.

When the starting time of the combustion event is determined based on torsional vibration riveting, the system comprises gauges for measuring crankshaft torsional vibration. An angle sensor 16 for measuring the crankshaft rotation angle 10 can be used as a measuring element to obtain measurement information on the magnitude of the torsional vibration as well as the rotational angle at which the torsional vibration occurs. The measurement data is sent to the control unit 14. The control unit 14 determines, based on the measurement data, the time of the start of the combustion event in each cylinder 3.

15 Once the start time of the combustion event has been determined, the control unit 14 compares the specified start time of the combustion event with a certain setpoint. The setpoint may be predetermined, for example, based on the motor load and the pressure in the common rail 9. If the specified start time of the combustion event differs from the set value, the control unit 14 changes the start time of fuel injection per cylinder. The fuel injection start time is changed so that the combustion start time is approaching the setpoint. Since the start time of the fuel injection corresponds quite closely to the start time of the combustion event, the start time of the fuel injection can be changed to the set value of the start time of the combustion event.

dj g In addition, the control unit 14 changes the fuel injection duration of the cylinders 3 to equalize the power produced by the cylinders. Fuel injection

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the duration is changed per cylinder. The fuel injection duration is varied after the above-described fuel injection start time adjustment has been made, i.e., the fuel injection start time has been obtained.

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fmal. The fuel injection duration can be varied so that the power produced by the cylinders 3 is equal. The fuel injection duration can be varied based on the exhaust gas temperatures of the cylinders 3 or the crankshaft torsional vibration measurement.

5 When adjusting fuel injection duration based on exhaust gas temperatures, system 1 comprises cylinder-specific temperature sensors 18 for measuring cylinder exhaust temperatures. The temperature sensors 18 are mounted in the exhaust ducts 19 of the cylinders. The measurement data of the temperature sensors 18 is transmitted to the control unit 14. The control unit 14 changes the fuel injection duration 10 based on the measured exhaust gas temperatures. The duration of the fuel injection is adjusted to equalize the power produced by the cylinders 3. The control unit 14 can change the duration of fuel injection so that the exhaust gas temperatures of the cylinders 3 are equal. The measured exhaust gas temperatures are compared to the set value. If the measured exhaust gas temperature of one of the cylinders 3 deviates from the setpoint 15, the duration of fuel injection to that cylinder will be changed so that the exhaust gas temperature is at its set point. The exhaust gas temperature setpoint can be the average or predetermined value of the measured exhaust gas temperatures, which may vary depending on, for example, engine load or fuel used. Fuel injection duration 20 is increased if the exhaust gas temperature is too low. Similarly, fuel injection times will be shortened if the exhaust temperature is too high.

When the fuel injection duration is adjusted based on crankshaft torsional vibration measurement, the system comprises measuring means for measuring crankshaft torsional vibration. As a measuring element, an angle sensor 16 for measuring the crankshaft wheel path angle can be used, thereby providing measurement data i g on the magnitude of the torsional vibration and the rotational angle at which the torsional vibration x occurs. The measurement data is sent to the control unit 14. The control unit 14 adjusts 0_ per cylinder the duration of fuel injection so as to minimize the torque oscillation of the crankshaft Ιο 30.

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Fuel injection duration can be changed using both of the methods described above, based on cylinder exhaust temperatures and crankshaft torque oscillation. In this case, the duration of the fuel injection can be adjusted by utilizing both measurements simultaneously or by preferentially using only one measurement, for example exhaust temperature measurement, with another measurement being in reserve. If necessary, the second measurement can be used, for example, if the primary measurement fails.

The invention is not limited to the embodiments shown, but several variations 10 are conceivable within the scope of the appended claims. The start time of the combustion event can be determined by measuring the flow of the solenoid valves of the injectors 5 or by measuring the injection pressure of the fuel. The fuel injection pressure can be measured by a pressure switch or pressure sensor located in the common pressure storage 9 or the injector fuel passage 10.

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For example, according to one embodiment, the fuel injection duration of the cylinders 3 is varied on the basis of the exhaust gas temperatures and the torsional vibration to equalize the power produced by the cylinders. In this way, it is possible to further increase the accuracy of the adjustment with respect to the duration of the injection.

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The method further comprises the step of evaluating the accuracy of the exhaust gas temperature measurement and determining the change in fuel injection duration based on torsional vibration if the cylinder exhaust gas temperature measurement is not valid. Cases where the exhaust gas temperature measurement is not valid are, for example, a failure of the sensor that measures the exhaust gas temperature, or the exhaust gas temperature 18 of the cylinder c / j is sufficiently different from the preset temperature value or the average exhaust gas temperature. The advantage of this is that the error conditions of the sensor affecting the injection duration can be ce

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it is not necessary to stop the engine. In this case, one way g 30 is to determine the change in the fuel injection duration of the cylinders 3 based on the torque oscillation, if the cylinder exhaust temperature 18 differs

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more than 50% of the set temperature value or the average exhaust gas temperature of the cylinders. The preset temperature value for that load may be stored, for example, in the control for the reference load and speed. Another way is to determine the change in the fuel injection duration of the cylinders 3 based on torsional vibration if the cylinder exhaust temperature 18 5 differs from a preset temperature value or the average of the cylinder exhaust gas temperatures by more than 10%. The advantage of this method is that the determination method affecting the duration of the injection can be temporarily varied, thereby selecting the one used primarily, here based on the exhaust gas temperature. Both methods can be implemented by modifying the functionality of the control unit 14 of the system 10.

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Claims (22)

1. A method for balancing a diesel engine (2) cylinders (3), characterized in that - it is determined the starting time of the combustion event of each cylinder (3) - the determined starting time of the combustion event is compared with a given set point and - the fuel injection time is changed to the cylinders (3) if the determined combustion event start time deviates from the set point, - the respective cylinder exhaust temperature (18) is measured, and - the fuel injection time of the cylinders (3) is changed on the basis of the exhaust gas balance. of the cylinders (3) produced the effects. Process according to claim 1, characterized in that the cylinder-specific fuel injection time is extended if the exhaust temperature is too low and shortened if the exhaust temperature is too high. 20 Method according to claim 1 or 2, characterized in that the fuel injection time of the cylinders (3) is changed so that a desired exhaust temperature setpoint is achieved. o 25 Method according to Claim 3, characterized in that the measured value of the measured exhaust temperatures or a predetermined value is used as the set point. i σ> o x Method according to any of the preceding claims, characterized in that the CL measures the torsional oscillation of the engine crankshaft and changes the fuel injection time of the cylinders (3) on the basis of the torsional oscillation to balance the effects produced by the cylinders (3). (M Method according to claim 5, characterized in that the fuel injection time of the cylinders (3) is changed based on the exhaust temperatures and on the basis of the torsional oscillation. 5 Method according to claim 5, characterized in that the method further comprises a step for estimating the validity of the exhaust temperature measurement (18) and for deciding (3) changing the fuel injection time of the cylinders on the basis of the torsional swing of the exhaust temperature measurement (18) of the cylinder. is valid. 10 Method according to claim 5 or 7, characterized in that if the fuel injection time of the cylinders (3) is changed based on the torsional oscillation if the exhaust temperature of the cylinder (3) deviates from a predetermined temperature value or the average value of the exhaust gas temperatures of the cylinders (3) . Method according to any of the preceding claims, characterized in that the position (15, 16) of the respective cylinder (3) cylinder pressure is measured and the starting time of the combustion event is determined on the basis of the measurement of the position of the cylinder pressure. Method according to claim 8, characterized in that the cylinder pressure is measured with a knock sensor, strain sensor or pressure sensor (15) arranged in conjunction with the cylinder (3). δ 25 (M c Method according to any of the preceding claims, characterized in that g is measured the torsional oscillation of the crankshaft of the engine and is determined initially at the time of the combustion event on the basis of the torsional oscillation measurement CL. £ 30m System (1) for balancing the cylinders of a diesel engine (2), which system comprises, in conjunction with the respective cylinder (3), installable temperature sensors (3) for measuring the exhaust gas temperature of the cylinder, characterized in that the system (1) comprises a control unit (14) arranged to - determine the start time of the respective combustion event (3), 5. compare the determined start time of the combustion event with a set point, - change the start time of injection of fuel to the cylinders (3). the initial time of the combustion event deviates from the set point and 10 - change the fuel injection time of the cylinders (3) on the basis of the exhaust temperatures to balance the effects produced by the cylinders. System according to claim 12, characterized in that the control unit is arranged to specifically extend the fuel injection time if the exhaust temperature is too low and to shorten the fuel injection time if the exhaust temperature is too high. Method according to any of the preceding claims, characterized in that the control unit (14) is arranged to change the fuel injection time so that a desired setpoint for the exhaust temperature of the cylinders (3) is reached. 15. A system according to claim 14, characterized in that the setpoint is the average of the measured exhaust temperatures or a predetermined value. o 25 System according to any of the preceding claims 12 - 15, characterized in that the system (1) comprises means (16) for measuring the torsional oscillation in the crankshaft of the engine and that the control unit (14) is arranged to change the fuel injection time. for the cylinders (3) on the basis of the torsional oscillation for CL to balance the effects produced by the cylinders (3) k 30 tn System according to any one of the preceding claims 12-16, characterized in that the system (1) comprises means (16) for measuring the torsional oscillation of the crankshaft of the engine and that the control unit (14) is arranged to change the fuel injection time of the cylinders. (3) bed on the basis of the exhaust temperatures and on the basis of the torsional oscillation. 18. A system according to claim 16, characterized in that it further comprises means for estimating the validity of the exhaust temperature measurement (18) and for deciding (3) changing the fuel injection time of the cylinders (3) on the basis of the torsional oscillation of the exhaust temperature measurement (18). the cylinder is not valid. 10 System according to claim 18, characterized in that the control unit (14) is arranged to change the fuel injection time of the cylinders (3) on the basis of the torsional oscillation if the cylinder exhaust temperature (18) deviates from a predetermined temperature value or the average value of the exhaust gas temperatures of the cylinders (3). . System according to any of the preceding claims 12-19, characterized in that the system (1) comprises means (15, 16) for measuring the position of the cylinder pressure of each cylinder (3) and that the control unit (14) is arranged to determine The starting time of the combustion event of the cylinders (3) is based on the measurement of the position of the cylinder pressure. 21. A system according to claim 20, characterized in that the means for measuring the position of the cylinder pressure comprise a knock sensor, strain sensor or pressure sensor (15) arranged in connection with the cylinder. CM 22. A system according to claim 20 or 21, characterized in that the means for measuring the position of the cylinder pressure comprise an angle sensor (16) which measures the rotation angle of the crankshaft of the engine. CD LO LO CD o o C \ l