Control method for reducing plateau power loss of supercharged diesel engine by using EGR (Exhaust Gas Recirculation)

Abstract

The invention relates to the technical field of diesel engine power control, in particular to a control method for reducing plateau power loss of a supercharged diesel engine through EGR. The working condition point of current operation is obtained through the engine rotating speed sensor and the accelerator position sensor, the electronic control unit corrects the main injection advance angle and the rail pressure according to the current altitude, and then the opening degree of the EGR valve is calculated and controlled according to the air amount demand value and the actual air inflow measured by the PFM air flow meter. When the altitude simulation test bench performs external characteristic tests under various altitudes, the main injection advance angle, the rail pressure and the air quantity demand quantity of the diesel engine are continuously debugged by combining the rotating speed of a diesel engine supercharger, the vortex front exhaust temperature and the smoke intensity value tested by the bench, and finally the EGR opening degree value and the external characteristic oil quantity value under the altitude condition are determined. And obtaining the maximum plateau power result under the altitude condition.

Description

Technical Field

[0001] The invention relates to the technical field of diesel engine power control, and in particular to a control method for reducing plateau power loss of a supercharged diesel engine by using EGR. Background Art

[0002] Diesel engines have become the main power source in the commercial vehicle field due to their efficient heat release efficiency and higher fuel utilization rate. With the implementation of the National VI Emission Regulations, mainstream diesel engine systems all use exhaust gas recirculation systems (EGR) to control the original engine exhaust. When the vehicle is running in plateau areas, as the altitude increases, the air density becomes thinner and thinner, and the oxygen content of fresh air will also decrease, resulting in worsening combustion. When the diesel engine is running near the external characteristics, the increase in the exhaust temperature or pressure before the turbine will cause the abandoned turbocharger to overheat and overspeed. In order to protect the engine or supercharger, the amount of oil in the engine's external characteristics has to be limited, resulting in engine torque limitation, which ultimately manifests as severe power loss in the plateau, especially at high speeds.

[0003] In order to restore the power performance at high altitudes, diesel engines mostly use exhaust gas turbocharging systems based on cost control. However, with the intensification of market competition, the power level of the plains has been continuously improved after the main engine manufacturers adopted the supercharging technology. The rated power level of the plains has been tapped to the extreme, and the boost pressure ratio of the exhaust gas turbocharger has continued to increase, which ultimately leads to the power of the supercharged diesel engine being lower than that of the plains under high altitude conditions. The traditional technical method is to restore the combustion efficiency and explosion pressure of the engine under plateau conditions by optimizing the combustion parameters, but for high-pressure ratio supercharged diesel engines, because the supercharger is overheated and overspeeded, the power restored by this method is limited, and the power loss is still large. Therefore. How to solve the problem of large power loss of turbocharged diesel engines in plateaus has become a difficult problem in research and development. Summary of the invention

[0004] In view of the above problems, the present invention provides a control method for reducing the plateau power loss of a supercharged diesel engine by using EGR.

[0005] The technical solution adopted is a control method for reducing the plateau power loss of a turbocharged diesel engine using EGR, comprising the following steps: S1. The diesel engine is tested for external characteristics at different altitudes on an altitude simulation test bench; S2. Increase the main injection advance angle and rail pressure to restore the maximum explosion pressure of the engine to the target value; S3. Determine whether the diesel engine can increase the cyclic injection amount at the operating point; S4. If the diesel engine has a supercharger overspeed or over-exhaust temperature phenomenon, adjust the required intake volume of the diesel engine at the operating point under the altitude condition, so that the EGR of the diesel engine is gradually opened when it is running under the operating condition, and judge the smoke value; S5. Repeat the action of increasing the injection oil amount or increasing the EGR opening until the smoke value exceeds the allowable smoke limit or the current turbocharger speed and pre-turbine exhaust temperature are over-temperature and over-speed, complete the test, and obtain the final external characteristic power.

[0006] Optionally, in S1, the diesel engine is provided with an electronic control unit, an ambient pressure sensor, an engine speed sensor and a throttle position sensor; The electronic control unit is used to obtain the altitude position of the engine operation and control the opening of the EGR valve; The ambient pressure sensor collects the current operating altitude of the engine and transmits it to the electronic control unit; The engine speed sensor and the throttle position sensor provide the electronic control unit with the current operating point of the engine.

[0007] Optionally, the electronic control unit corrects the main injection advance angle and the rail pressure according to the current altitude, and calculates and controls the opening of the EGR valve according to the air volume demand value and the actual intake air volume measured by the air flow meter.

[0008] Optionally, in S3, it is determined whether the supercharger is overspeeding and whether the exhaust temperature before the turbine of the diesel engine exceeds the allowable exhaust temperature to determine whether the circulating fuel injection amount at the operating point can be increased.

[0009] Optionally, in S3, if the diesel engine does not have over-temperature or over-speed, the cyclic injection amount is directly increased, and steps S1 to S3 are executed cyclically. If the diesel engine has supercharger over-speed or over-exhaust temperature, S4 is executed.

[0010] Optionally, in S4, if the smoke value is within the specified smoke limit target, and the current supercharger speed and pre-turbine exhaust temperature are both within the allowable range of the diesel engine, the injection amount can be further increased and S5 is executed, otherwise steps S1 to S4 are executed cyclically.

[0011] The beneficial effects of the present invention are: 1. A control method for reducing the plateau power loss of a supercharged diesel engine by using EGR is provided. By turning on EGR to reduce the cylinder pressure and the maximum combustion temperature, the supercharger over-temperature and over-speed are reduced, and the power level of the engine output is increased as much as possible, so as to achieve the purpose of reducing the plateau power loss of the diesel engine; 2. At the same time, when conducting a high-altitude external characteristic test, the current operating altitude of the diesel engine can be obtained through the electronic control unit, and when the diesel engine is judged to be operating in the external characteristic area based on the throttle position and the engine speed sensor, combined with the supercharger speed and pre-turbine exhaust temperature of the oil production machine under the current operating conditions collected by the test bench, and the smoke value results of the smoke equipment test, the control method is used to make a judgment, continuously adjust the air volume demand value, change the EGR opening of the diesel engine, and adjust the actual cyclic injection amount of the external characteristic, and finally achieve the maximum power level of the diesel engine when it runs to the operating point at the altitude, effectively improving the power loss of the diesel engine at the altitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The schematic diagram of the engine system is as follows; Figure 2 The present invention is a logic diagram of a control method for reducing the plateau power loss of a turbocharged diesel engine by using EGR. DETAILED DESCRIPTION

[0013] The following describes the implementation of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0014] It should be noted that the illustrations provided in the following embodiments are only used to schematically illustrate the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0015] In this embodiment, Figure 1 and Figure 2 As shown, a control method for reducing the plateau power loss of a supercharged diesel engine using EGR is provided, comprising the following steps: S1. The diesel engine is tested for external characteristics at different altitudes on an altitude simulation test bench; S2. Increase the main injection advance angle and rail pressure to restore the maximum explosion pressure of the engine to the target value; S3. Determine whether the diesel engine can increase the cyclic injection amount at the operating point; S4. If the diesel engine has a supercharger overspeed or over-exhaust temperature phenomenon, adjust the required intake volume of the diesel engine at the operating point under the altitude condition, so that the EGR of the diesel engine is gradually opened when it is running under the operating condition, and judge the smoke value; S5. Repeat the action of increasing the injection oil amount or increasing the EGR opening until the smoke value exceeds the allowable smoke limit or the current turbocharger speed and pre-turbine exhaust temperature are over-temperature and over-speed, complete the test, and obtain the final external characteristic power.

[0016] The purpose of this design is to provide a control method for using EGR to reduce the plateau power loss of a turbocharged diesel engine. By turning on EGR to reduce the cylinder pressure and the maximum combustion temperature, the supercharger overheating and overspeeding can be reduced, and the engine output power level can be increased as much as possible, thereby reducing the plateau power loss of the diesel engine.

[0017] Meanwhile, in a specific implementation, when the diesel engine is subjected to external characteristic tests at different altitudes on an altitude simulation test bench, the maximum explosion pressure of the engine is first restored to the target value by increasing the main injection advance angle and the rail pressure according to the altitude and the engine speed under the current working condition of the diesel engine; According to the supercharger speed value and the exhaust temperature before the turbine measured by the test bench, if the two jointly determine that the current supercharger speed of the diesel engine does not exceed the limit and the exhaust temperature before the turbine does not exceed the limit, the circulating fuel injection amount of the diesel engine at this operating point is increased to improve the power level at this altitude.

[0018] If the diesel engine has a supercharger overspeed or an over-exhaust temperature phenomenon, the next step is executed; The diesel engine adjusts the required intake volume at the operating point under the altitude condition, so that the EGR of the diesel engine gradually opens when it is running under the operating condition. At this time, it is necessary to measure the smoke value of the diesel engine after the EGR is turned on when it is running under the current operating condition. If the smoke value is within the specified smoke limit target, the injection amount can be further increased, thereby continuing to increase the power of the plateau external characteristic point, returning to the supercharger overspeed or over-exhaust temperature judgment mentioned above, and repeating the action of increasing the injection amount or increasing the EGR opening until the smoke value exceeds the allowable smoke limit. The test is then stopped to obtain the final external characteristic power, which is the maximum power level of the diesel engine under this operating condition under the altitude condition.

[0019] Take specific data as an example: For a certain model of diesel engine, the rated power point speed is 2600 at 0 meters altitude, and the rated power is 162kW. The engine external characteristic test at 2000 meters altitude is carried out on the altitude simulation bench, the engine speed is 2600rpm, the power is 120kW, the current EGR opening is 0%, the throttle opening is 100%, the cycle injection amount is 80mg / hub, the required intake amount is 1600mg / hub, the actual intake amount is 1600mg / hub, the rail pressure is 1700000hPa, and the main injection advance angle is 14deg.

[0020] The current exhaust temperature before the turbine of the diesel engine in the bench test is 700°C, the allowable exhaust temperature before the turbine is 750°C, the supercharger speed is 170,000 rpm, the maximum allowable supercharging speed is 180,000 rpm, the current explosion pressure of the diesel is 17 MPa, the maximum allowable explosion pressure is 18 MPa, the current measured 415 smoke value is 0.8FSN, and the maximum allowable smoke value at this point is controlled to be 2FSN.

[0021] At this time, first increase the current main injection advance angle and rail pressure to control the burst pressure to 18MPa. At this time, the supercharger speed and the exhaust temperature before the turbine are still lower than the limit requirements of the diesel engine, then increase the external characteristic injection amount. When the injection amount is 85mg / str, the supercharger speed reaches 180,000 rpm, reaching the maximum supercharger speed limit allowed by the supercharger speed.

[0022] Next, the air demand is adjusted to 1550mg through the plateau altitude correction coefficient. Because the demand is less than the current actual intake, EGR is turned on, and the EGR opening is 5%. The final actual intake is 1550mg / str. At this time, the test engine smoke value is 1.5FSN, and the current supercharger speed will be 175,000 rpm, and the exhaust temperature before the turbine is 730℃, so the external characteristic oil volume can be further increased.

[0023] When the diesel is at 2600rpm and the throttle is fully open, after repeated debugging, the final results are as follows: the current EGR opening is 8%, the throttle opening is 100%, the cycle injection amount is 90mg / hub, the required intake volume is 1500mg / hub, the actual intake volume is 1500mg / hub, the rail pressure is 1800000hPa, the main injection advance angle is 16deg, the maximum burst pressure is 18MPa, 415 smoke degree 1.8FSN, the pre-turbine exhaust temperature is 740℃, and the supercharger speed is 180,000 rpm. Because the supercharger speed reaches the maximum allowable speed limit, the test ends and the final engine power is 145kW.

[0024] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for reducing the plateau power loss of a supercharged diesel engine using EGR, characterized in that: The following steps are involved: S1. The diesel engine is tested for external characteristics at different altitudes on an altitude simulation test bench; S2. Increase the main injection advance angle and rail pressure to restore the maximum explosion pressure of the engine to the target value; S3. Determine whether the diesel engine can increase the cyclic injection amount at the operating point; S4. If the diesel engine has a supercharger overspeed or over-exhaust temperature phenomenon, adjust the required intake volume of the diesel engine at the operating point under the altitude condition, so that the EGR of the diesel engine is gradually opened when it is running under the operating condition, and judge the smoke value; S5. Repeat the action of increasing the injection oil amount or increasing the EGR opening until the smoke value exceeds the allowable smoke limit or the current turbocharger speed and pre-turbine exhaust temperature are over-temperature and over-speed, complete the test, and obtain the final external characteristic power.

2. A control method for reducing high-altitude power loss of a supercharged diesel engine using EGR according to claim 1, characterized in that: In S1, the diesel engine is provided with an electronic control unit, an ambient pressure sensor, an engine speed sensor and a throttle position sensor; The electronic control unit is used to obtain the altitude position of the engine operation and control the opening of the EGR valve; The ambient pressure sensor collects the current operating altitude of the engine and transmits it to the electronic control unit; The engine speed sensor and the throttle position sensor provide the electronic control unit with the current operating point of the engine.

3. A control method for reducing high-altitude power loss of a supercharged diesel engine using EGR according to claim 2, characterized in that: The electronic control unit corrects the main injection advance angle and the rail pressure according to the current altitude, and calculates and controls the opening of the EGR valve according to the air volume demand value and the actual intake air volume measured by the air flow meter.

4. A control method for reducing high-altitude power loss of a supercharged diesel engine using EGR according to claim 1, characterized in that: In S3, it is determined whether the supercharger is overspeeding and whether the exhaust temperature before the turbine of the diesel engine exceeds the allowable exhaust temperature to determine whether the circulating fuel injection amount at the operating point can be increased.

5. A control method for reducing high-altitude power loss of a supercharged diesel engine using EGR according to claim 4, characterized in that: In S3, if the diesel engine does not have over-temperature or over-speed, the cyclic injection amount is directly increased, and steps S1 to S3 are cyclically executed. If the diesel engine has supercharger over-speed or over-exhaust temperature, S4 is executed.

6. A control method for reducing high-altitude power loss of a supercharged diesel engine using EGR according to claim 5, characterized in that: In S4, if the smoke value is within the specified smoke limit target, and the current turbocharger speed and pre-turbine exhaust temperature are within the allowable range of the diesel engine, the injection amount can be further increased and S5 is executed, otherwise steps S1 to S4 are executed cyclically.

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