CN111502836A - Control method for exhaust valve of low-speed two-stroke diesel engine - Google Patents
Control method for exhaust valve of low-speed two-stroke diesel engine Download PDFInfo
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- CN111502836A CN111502836A CN202010282731.5A CN202010282731A CN111502836A CN 111502836 A CN111502836 A CN 111502836A CN 202010282731 A CN202010282731 A CN 202010282731A CN 111502836 A CN111502836 A CN 111502836A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0242—Variable control of the exhaust valves only
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0242—Variable control of the exhaust valves only
- F02D13/0249—Variable control of the exhaust valves only changing the valve timing only
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0253—Fully variable control of valve lift and timing using camless actuation systems such as hydraulic, pneumatic or electromagnetic actuators, e.g. solenoid valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0276—Actuation of an additional valve for a special application, e.g. for decompression, exhaust gas recirculation or cylinder scavenging
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/22—Safety or indicating devices for abnormal conditions
- F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/22—Safety or indicating devices for abnormal conditions
- F02D2041/228—Warning displays
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
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- Output Control And Ontrol Of Special Type Engine (AREA)
Abstract
The invention provides a control method of an exhaust valve of a low-speed two-stroke diesel engine, which specifically comprises the following steps: (1) exhaust valve position acquisition and selection strategies; (2) a strategy of lift calculation and current switch state judgment; (3) and (4) calculating the opening and closing angle of the exhaust valve. According to the exhaust valve position acquisition and selection strategy, because combustion is not needed to do work in the cylinder at the moment, the engine can be protected under the influence of water flow by the existence of the reference value of the opening/closing of the exhaust valve in the control unit; the strategy of lift calculation and current switch state judgment can be used in the process of overhauling the engine in a shutdown state, and if the engine needs to be turned; the invention has important significance for the performance, stability, emission, protection of relevant mechanical components and the like of the whole diesel engine.
Description
Technical Field
The invention relates to a control method of an exhaust valve of a diesel engine, in particular to a control method of an exhaust valve of a low-speed two-stroke diesel engine, belonging to the field of control of internal combustion engines.
Background
The low-speed two-stroke diesel engine provides main power for dry bulk cargo ships, large oil tankers and container ships, and is used in a large scale in the global range. Along with the improvement of emission regulations and the reduction of fuel reserves, the low-speed marine diesel engine also develops towards intellectualization, and compared with the traditional low-speed two-stroke diesel engine, the intelligent diesel engine cancels an exhaust valve driving device, a fuel pump, a cam shaft, a reversing servo motor, a fuel oil connection device, a servo motor, a starting air distributor and other devices; the device comprises a common rail device for establishing fuel pressure instead, a host control unit, a servo oil system for controlling the action of an exhaust valve, an injection control unit for controlling the injection quantity and the pulse width, a fuel supply unit for supplying high-pressure fuel and servo oil and the like. The diesel engine main machine control module mainly comprises cylinder lubricating oil control, fuel pump control, an integrated speed regulator, pressurization system control and variable exhaust timing control.
With the gradual progress of the intellectualization of the diesel engine, a control system of the exhaust valve, which is one of important parts of the diesel engine, becomes important, the exhaust valve control system capable of ensuring the reasonable operation of the engine in various working conditions is researched, and the exhaust valve control system has important significance for the performance, the stability, the emission, the protection of related mechanical components and the like of the whole diesel engine. The opening/closing angle of the exhaust valve is related to the in-cylinder filling stratified condition, the utilization and waste degree of fuel, in-cylinder combustion conditions such as pressure, temperature, heat release rate and other parameters, and the accurate control of the opening/closing angle is very important in the design process of the diesel engine.
The exhaust valve driving system comprises a servo oil pump, a servo oil service pump, a 200bar servo oil common rail pipe, a common rail electromagnetic valve, an exhaust control valve, a driving valve, an exhaust valve position sensor, an air spring, a liquid level switch and the like, and is shown in figure 1. The opening of the exhaust valve is realized by that a control system sends an opening electric signal to the common rail valve, a main valve hydraulic control oil circuit is connected, high-pressure hydraulic oil enters the bottom of a hydraulic driving piston in an exhaust driving pump through a main valve, the driving piston is pushed to move upwards to extrude the hydraulic oil in an exhaust valve driving pipe, the hydraulic piston at the top of the exhaust valve is driven by pressure oil to push the exhaust valve to move downwards, and meanwhile, an air cylinder in the middle of the exhaust valve is compressed to open the exhaust valve. When the exhaust valve is closed, the control system sends a closed electric signal to the common rail valve to cut off the control oil path of the main valve, the main valve is reset by the spring force after losing control hydraulic oil, the hydraulic oil at the bottom of the piston of the driving pump is released to drive the piston to reset, the pressure in the hydraulic pipe is reduced, the exhaust valve is gradually reset under the action of the air spring, and finally the exhaust valve is closed.
Disclosure of Invention
The invention aims to provide a control method of an exhaust valve of a low-speed two-stroke diesel engine for better protecting the engine.
The purpose of the invention is realized as follows:
a control method for an exhaust valve of a low-speed two-stroke diesel engine specifically comprises the following steps:
(1) exhaust valve position acquisition and selection strategies;
(2) a strategy of lift calculation and current switch state judgment;
(3) and (4) calculating the opening and closing angle of the exhaust valve.
The invention also includes such features:
1. the exhaust valve position acquisition and selection strategy specifically comprises the following steps:
the two sensors are used for detecting the positions of the exhaust valves, the two sensors can obtain respective current values after the position signals of the exhaust valves are collected, the numerical values displayed by the two sensors are not completely the same, the positions of the exhaust valves are monitored by the sensors, and then 4-20mA analog quantity signals are transmitted to a control system after the digital-analog signal conversion module of the host machine, wherein the numerical values reflect the opening and closing degree of the exhaust valves:
if the current value is not in the range of 4-20mA, the exhaust valve has faults in a single sampling and exceeds the allowable amplitude value which does not cause damage to the components;
if neither sensor fails, which is the operation that should be performed in most cases, the average value of the values displayed by both sensors is found as the final exhaust valve position value;
if #1 fails in a single sample and #2 does not, the value displayed by the #2 sensor is used as the final position of the exhaust valve at that moment;
if #2 fails in a single sample, and #1 does not, the value displayed by the #1 sensor is used as the final position of the exhaust valve at that moment;
if both sensors have faults, subsequent calculation is not carried out, and the exhaust valve is opened and closed according to a preset value; meanwhile, the failure times are accumulated, and the two sensors continuously display the failure condition for 3 times, so that the mechanical failure is judged, an alarm is sent to a security module of a host control unit, the emergency shutdown is attempted according to the current engine state, and a professional is dispatched to carry out maintenance;
2. in the exhaust valve position acquisition process, setting the exhaust valve to be opened when the total stroke of the exhaust valve exceeds 15% as the completion of the actual opening action, and setting the exhaust valve to be closed when the total stroke of the exhaust valve exceeds 85% as the completion of the actual closing action;
3. the strategy for lift calculation and current switch state judgment is specifically as follows:
(2.1) according to the position value of the exhaust valve triggered by the current sampling, synthesizing the position value of the exhaust valve triggered by the previous sampling to perform filtering calculation, and obtaining the result of the current position value of the exhaust valve after filtering;
(2.2) respectively reading the exhaust valve positions three times in 75-80 DEG CA and 175-180 DEG CA according to the current crank angle signal of the engine, calculating an average value to be used as a reference current value for closing and opening the circulation exhaust valve, wherein the exhaust valve should be completely opened or completely closed in the two intervals, and the average values in the two intervals are subjected to difference to obtain the exhaust valve lift;
(2.3) comparing the result of the filtered exhaust valve position with the lift of the exhaust valve, and outputting the current state of the exhaust valve as closed if the result is lower than 15% of the total lift; and if the current state of the exhaust valve is higher than 15%, outputting the current state of the exhaust valve as open.
4. The strategy for calculating the opening and closing angle of the exhaust valve is specifically as follows:
(3.1) reading the current servo oil pressure and oil temperature, reading the rotating speed, load, theoretical closing angle of the exhaust valve in the last cycle and scavenging pressure, wherein the theoretical opening and closing angle of the exhaust valve can be determined after inquiring a rotating speed-load-reference valve timing MAP graph through the rotating speed and the load;
(3.2) under the influence of the change of the current servo oil pressure, the change of the servo oil temperature and the change of the exhaust valve closing angle, correcting the theoretical opening angle of the exhaust valve by combining the three parameters to obtain the expected opening angle of the exhaust valve;
and (3.3) under the influence of the temperature change of the current servo oil and the change of the scavenging pressure, correcting the theoretical closing angle of the exhaust valve by combining the two parameters to obtain the expected closing angle of the exhaust valve.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the exhaust valve position acquisition and selection strategy, because combustion is not needed to do work in the cylinder at the moment, the engine can be protected under the influence of water flow by the existence of the reference value of the opening/closing of the exhaust valve in the control unit;
2. the strategy of lift calculation and current switch state judgment can be used in the process of overhauling the engine in a shutdown state, and if the engine needs to be turned;
3. the strategy for calculating the opening and closing angle of the exhaust valve is used in the starting process of an engine from a static state to a constant speed running state, and when parameters such as scavenging efficiency, servo oil pressure oil temperature and the like change rapidly due to large difference of rotating speed between front and back cycles;
4. the invention has important significance for the performance, stability, emission, protection of relevant mechanical components and the like of the whole diesel engine.
Drawings
FIG. 1 is a discharge valve drive mechanism and principle;
FIG. 2 is a current command and operating state determination flow;
FIG. 3 is a flow chart of exhaust valve malfunction determination;
FIG. 4 is a schematic illustration of exhaust valve lift and command delay;
FIG. 5 is a flow chart of the current exhaust valve opening/closing state judgment;
FIG. 6 is a flow chart of calculation of the exhaust valve opening/closing angle;
FIG. 7 is a simulated fault accumulation result;
FIG. 8 is a simulated open and closed state determination for different exhaust valve lift curves;
fig. 9 simulates the results of the theoretical open/close angle change at different rotational speeds.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Aiming at the hydraulic and mechanical principles and the importance of exhaust valve control, the invention provides a perfect exhaust valve control strategy aiming at an exhaust valve control module in a main engine control unit, and the perfect exhaust valve control strategy is verified on the model simulation level, and the idea of the control strategy can be used in the actual design process of a low-speed two-stroke diesel engine. The specific implementation of the invention comprises the following steps:
(1) providing a complete control strategy aiming at the exhaust valve of the RT-Flex machine or the exhaust valve with similar structural principle;
(2) establishing an exhaust valve control strategy model in the SIMU L INK;
(3) partial functions of the exhaust valve control strategy were tested and verified.
Firstly, the current command and the current engine working state are compared and judged, and the working conditions are divided into normal, fault and starting, autorotation and turning, as shown in figure 2. After the mark of successful starting of the engine is established, the engine starts to enter a normal working state, wherein the normal working state comprises the requirements of drivers such as the increase and the reduction of the rotating speed and the like; the autorotation working condition is triggered under the condition that the rotating speed of the engine is higher than 3rpm and no engine starting command exists, and the turning working condition needs an additional switch for triggering; the starting condition is a condition that a starting command is issued and the current engine speed is 0, and the triggering condition of the fault mode is that the measured value of the position sensor is out of range during starting and normal operation, which will be explained in detail below.
Due to the consideration and design of safety, two Hall sensors for detecting the position of the exhaust valve are designed, the position of the exhaust valve is determined in real time through selection and calculation, and the determined position is used in the use process of a subsequent control strategy, so the part proposes the control strategy for acquiring and selecting the position of the exhaust valve, and the control strategy is shown in FIG. 3.
After the exhaust valve position signal is collected, the two sensors obtain respective current values, and the numerical values displayed by the two sensors are not completely the same due to the problems of instrument precision, installation errors and the like. The position of the exhaust valve is monitored by a sensor, and then the position of the exhaust valve is transmitted to a control system by a digital-analog signal conversion module of the host machine to form an analog quantity signal of 4-20mA, wherein the numerical value reflects the opening and closing degree of the exhaust valve.
And then, judging the range of the numerical values corresponding to the two sensors, namely whether the numerical values are in the specified limit range, if not, the exhaust valve is in the range, the exhaust valve has a fault in a single sampling and exceeds the allowable amplitude value which does not cause damage to the component, and the allowable amplitude value is set to be 2-22 mA.
If neither sensor fails, which is the operation that should be performed in most cases, the average of the values indicated by both sensors is taken as the final exhaust valve position value.
If #1 fails in a single sample and #2 does not, the value displayed by the #2 sensor is used as the final position of the exhaust valve at that time.
If #2 fails in a single sample, and #1 does not, the value displayed by the #1 sensor is used as the final position of the exhaust valve at that time.
If both sensors have faults, subsequent calculation is not carried out, and the exhaust valve is opened and closed according to a preset value; and meanwhile, accumulating the failure times, and if the two sensors show that the failure condition occurs for 3 times continuously, judging that the engine fails, sending an alarm to a security module of the host control unit, trying to perform emergency shutdown according to the current engine state and sending a professional for maintenance.
The strategy has 5 possible output results which cannot occur simultaneously, and the strategy is finished after the results are obtained.
During the monitoring of the position of the exhaust valve, the resulting analog signal generates fluctuations and noise, so the system internally sets: the actual opening action is determined to be completed when the exhaust valve is opened for more than 15% of the total stroke, and the actual closing action is determined to be completed when the exhaust valve is closed for more than 85% of the total stroke, as shown in fig. 4.
After the sub-control strategy is started, according to the exhaust valve position value under the current sampling trigger, the exhaust valve position value under the previous sampling trigger is integrated to perform filtering calculation, and a result of the filtered current exhaust valve position value is obtained, as shown in fig. 5. This result takes into account the error that is currently generated during the process of acquiring the exhaust valve position value, and uses the concept of first order inertial filtering, as shown in fig. 4, that is:
Yn＝αXn+(1-α)Yn-1
wherein α is the filter coefficient, XnIs the newly sampled value; y isn-1Is the last filtering result; y isnFor this filtering result, α is selected to be 0.5 for subsequent verification.
On the other hand, the exhaust valve positions are read three times in 75-80 CA, 175-180 CA, respectively, based on the current crank angle signal of the engine, and averaged as the reference current value for the closing and opening of the exhaust valve of the cycle, in which interval the exhaust valve should be fully open or fully closed, respectively. And (4) subtracting the average values in the two intervals to obtain the lift of the exhaust valve. Since the exhaust valve lift cannot be calculated before the exhaust valve action of the present cycle due to the acquired and calculated delays, the exhaust valve lift of the present cycle is ensured as accurately as possible within the operable range with the exhaust valve lift value of the previous cycle, as shown in fig. 5.
Then, comparing the result of the filtered exhaust valve position with the lift of the exhaust valve, and outputting the current state of the exhaust valve as closed if the result is lower than 15% of the total lift; and if the current state of the exhaust valve is higher than 15%, outputting the current state of the exhaust valve as open.
The total of two output results, namely the current open-close state of the exhaust valve, is finished, and then the control strategy is finished.
The calculation flow of the theoretical opening and closing angle of the exhaust valve is shown in fig. 6. On one hand, the current servo oil pressure and the current oil temperature are read, and the rotating speed, the load, the theoretical closing angle of the exhaust valve in the last cycle and the scavenging pressure are read, wherein the theoretical opening and closing angle of the exhaust valve can be determined after a rotating speed-load-reference valve timing MAP is inquired through the rotating speed and the load. Then, under the influence of the change of the current servo oil pressure, the change of the servo oil temperature and the change of the exhaust valve closing angle, the theoretical opening angle of the exhaust valve is corrected by integrating the three parameters to obtain the expected opening angle of the exhaust valve; under the influence of the temperature change of the current servo oil and the change of the scavenging pressure, the theoretical closing angle of the exhaust valve is corrected by combining the two parameters to obtain the expected closing angle of the exhaust valve. The parameters are verified through experiments and analyzed theoretically, the speed of the action time of the exhaust valve is influenced, namely the delay of the opening/closing of the exhaust valve is influenced, and the parameters need to be considered in a control strategy.
The crank angle at the exhaust valve closing timing of the previous cycle affects the crank angle at the exhaust valve opening timing of the present cycle. The influence of the exhaust valve closing angle on the opening angle is one of the factors for calculating the desired opening angle by multiplying an influence coefficient by the difference between the reference timing closing angle and the angle at which the exhaust valve is actually closed in the previous cycle.
On the other hand, due to factors such as the switching process of the solenoid valve, the process of pressure accumulation in each hydraulic pipeline exceeding the pre-tightening force of the spring, the time consumed for signal transmission between the control units, the motion process of the hydraulic piston and the like, the opening/closing process of the exhaust valve has a certain time delay from the sending of the action command to the actual action. The actual opening/closing angle and the expected opening/closing angle of the previous cycle are collected, and the crank angle degree corresponding to the delay time is calculated. Wherein the expected opening/closing is calculated after synthesizing the parameters of the influence and stored in the register; the actual opening/closing angle is obtained by reading and registering the crank angle of the engine at that time, triggered by the judgment of the opening/closing of the exhaust valve as a condition. Because of the existence of the delay, the invention takes the rotation angle of the crankshaft corresponding to the delay into the influence factor of the opening/closing angle of the exhaust valve of the cycle, and the opening/closing angle of the exhaust valve of the cycle minus the delay angle under a coefficient can realize the compensation or offset effect of the delay to a certain extent.
The resulting crank angle at which the command to open or close the exhaust valve is given is the angle at which the exhaust valve can be opened or closed at a reasonable angle in actual motion, as shown in fig. 6.
The ship may be influenced by the water flow with a large flow speed when being parked or stationary, so that the propeller is stressed, and the working condition is recorded as a rotation working condition. At this time, the exhaust valve still needs to be controlled correspondingly, otherwise, the piston can form larger pressure in the cylinder after the compression stroke is finished, and if the exhaust valve is not opened, the exhaust valve can have adverse effects on the internal mechanical structure of the engine, a hydraulic device and the like. The trigger condition of the condition is set to be that no starting signal exists and the rotating speed of the engine is more than 3rpm, and because combustion is not needed to do work in the cylinder at the moment, the engine can be protected under the influence of water flow by the aid of the reference value of opening/closing of the exhaust valve in the control unit.
When the engine is overhauled in a shutdown state, if the turning motion of the engine is needed, the opening/closing reference value of the exhaust valve in the control unit is also used for opening/closing.
In the starting process of the engine from a static state to a constant speed operation state, parameters such as scavenging efficiency, servo oil pressure oil temperature and the like are changed rapidly due to large rotation speed difference between the front and the back cycles, so that an exhaust valve control strategy special for starting is set. This strategy will be experimentally tested and calibrated with reference to a reference timing opening/closing angle. The strategy is effective because the engine can be started to a constant speed operation state stably under the MAP with the opening/closing angle of the exhaust valve. The opening/closing angle after successful start-up will be calculated by the method described above.
When the valve position sensor indicates a malfunction of the exhaust valve, the calculation of the delay time from the command to the actual actuation of the exhaust valve is not accurate due to errors in the measurement of the position of the exhaust valve and the calculation of the lift, so that in this case a control according to the desired opening/closing angle is carried out, wherein the parameters affecting the desired opening/closing angle are in accordance with what has been described above. If both sensors show faults (less than three times), the forced deceleration treatment is carried out on the engine, and the control system continues to monitor in the period, wherein other monitoring indexes in the security system of the whole machine also need to be closely concerned in the basis of evaluating whether the engine is normal or not. If the fault exceeds three times, an alarm is given, and relevant technicians are dispatched to enter the cabin for maintenance.
The exhaust valve position acquisition and selection strategy is adopted to establish an exhaust valve fault judgment model in the SIMU L INK according to the above-mentioned exhaust valve position acquisition and selection strategy, wherein the waveform diagram of a simulation fault accumulation part is shown in figure 7, the upper diagram is a random signal generated by white noise, the value of the random signal represents that both the two exhaust valves judge the exhaust valve fault when the value is 1, the value of the random signal is zero, the two exhaust valve sensors do not simultaneously display abnormity, and the lower diagram is a waveform diagram which triggers alarm and deceleration (Boolean value is 1) when three faults are accumulated within a certain time, and the waveform diagram is in accordance with the design concept after the verification.
FIG. 8 is a waveform diagram of a model display of a control strategy built in SIMU L INK according to the strategy of lift calculation and current switch state determination, wherein the upper diagram is a simulated exhaust valve lift signal (amplitude according to physical lift, and one-dimensional table look-up conversion is needed if current change evaluation is needed), the third cycle changes amplitude, the fourth cycle changes opening duration, the middle diagram is a waveform diagram of an exhaust valve lift calculation function, the lower diagram is a result of switch state determination, 1 represents that an exhaust valve is in a current opening state, 0 represents that the exhaust valve is in a current closing state, the first cycle does not obtain the determination of the opening/closing state and is caused by the time lag of calculating the exhaust valve lift, the third cycle is determined to be fault, and the results displayed by the model including the third cycle meet the design expectation in comparison of the exhaust valve lift calculation and the switch state.
FIG. 9 is a waveform diagram modeled in SIMU L INK according to a strategy for exhaust valve opening and closing angle calculation, with some steps omitted or with the influence of certain factors set to constant values.
Claims (5)
1. A control method for an exhaust valve of a low-speed two-stroke diesel engine is characterized by comprising the following steps:
(1) exhaust valve position acquisition and selection strategies;
(2) a strategy of lift calculation and current switch state judgment;
(3) and (4) calculating the opening and closing angle of the exhaust valve.
2. The method as claimed in claim 1, wherein the exhaust valve position collection and selection strategy is specifically:
the two sensors are used for detecting the positions of the exhaust valves, the two sensors can obtain respective current values after the position signals of the exhaust valves are collected, the numerical values displayed by the two sensors are not completely the same, the positions of the exhaust valves are monitored by the sensors, and then 4-20mA analog quantity signals are transmitted to a control system after the digital-analog signal conversion module of the host machine, wherein the numerical values reflect the opening and closing degree of the exhaust valves:
if the current value is not in the range of 4-20mA, the exhaust valve has faults in a single sampling and exceeds the allowable amplitude value which does not cause damage to the components;
if neither sensor fails, which is the operation that should be performed in most cases, the average value of the values displayed by both sensors is found as the final exhaust valve position value;
if #1 fails in a single sample and #2 does not, the value displayed by the #2 sensor is used as the final position of the exhaust valve at that moment;
if #2 fails in a single sample, and #1 does not, the value displayed by the #1 sensor is used as the final position of the exhaust valve at that moment;
if both sensors have faults, subsequent calculation is not carried out, and the exhaust valve is opened and closed according to a preset value; and meanwhile, accumulating the failure times, and if the two sensors show that the failure condition occurs for 3 times continuously, judging that the engine fails, sending an alarm to a security module of the host control unit, trying to perform emergency shutdown according to the current engine state and sending a professional for maintenance.
3. The method as claimed in claim 2, wherein the exhaust valve position is collected by setting the actual opening operation to be completed when the exhaust valve is opened for more than 15% of the total stroke, and setting the actual closing operation to be completed when the exhaust valve is closed for more than 85% of the total stroke.
4. The method as claimed in claim 1, wherein the strategy of lift calculation and current switch state determination is as follows:
(2.1) according to the position value of the exhaust valve triggered by the current sampling, synthesizing the position value of the exhaust valve triggered by the previous sampling to perform filtering calculation, and obtaining the result of the current position value of the exhaust valve after filtering;
(2.2) respectively reading the exhaust valve positions three times in 75-80 DEG CA and 175-180 DEG CA according to the current crank angle signal of the engine, calculating an average value to be used as a reference current value for closing and opening the circulation exhaust valve, wherein the exhaust valve should be completely opened or completely closed in the two intervals, and the average values in the two intervals are subjected to difference to obtain the exhaust valve lift;
(2.3) comparing the result of the filtered exhaust valve position with the lift of the exhaust valve, and outputting the current state of the exhaust valve as closed if the result is lower than 15% of the total lift; and if the current state of the exhaust valve is higher than 15%, outputting the current state of the exhaust valve as open.
5. The method for controlling the exhaust valve of the low-speed two-stroke diesel engine as claimed in claim 1, wherein the strategy for calculating the opening and closing angle of the exhaust valve is specifically as follows:
(3.1) reading the current servo oil pressure and oil temperature, reading the rotating speed, load, theoretical closing angle of the exhaust valve in the last cycle and scavenging pressure, wherein the theoretical opening and closing angle of the exhaust valve can be determined after inquiring a rotating speed-load-reference valve timing MAP graph through the rotating speed and the load;
(3.2) under the influence of the change of the current servo oil pressure, the change of the servo oil temperature and the change of the exhaust valve closing angle, correcting the theoretical opening angle of the exhaust valve by combining the three parameters to obtain the expected opening angle of the exhaust valve;
and (3.3) under the influence of the temperature change of the current servo oil and the change of the scavenging pressure, correcting the theoretical closing angle of the exhaust valve by combining the two parameters to obtain the expected closing angle of the exhaust valve.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010282731.5A CN111502836A (en) | 2020-04-12 | 2020-04-12 | Control method for exhaust valve of low-speed two-stroke diesel engine |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010282731.5A CN111502836A (en) | 2020-04-12 | 2020-04-12 | Control method for exhaust valve of low-speed two-stroke diesel engine |
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| CN111502836A true CN111502836A (en) | 2020-08-07 |
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| CN202010282731.5A Pending CN111502836A (en) | 2020-04-12 | 2020-04-12 | Control method for exhaust valve of low-speed two-stroke diesel engine |
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| CN1710258A (en) * | 2004-06-17 | 2005-12-21 | 五十铃自动车株式会社 | Exhaust valve drive control method and device |
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