Method for determining injection interval of multiple injection of high-pressure common rail system

Abstract

The application provides a high-pressure common rail system multiple injection injection interval determination method, comprising the following steps: S1. Building a high-pressure common rail system injection process high-speed photography direct shooting test system, setting an injection interval between pre-injection end and main injection start in an electronic control system, which is a control signal injection interval T1; S2. Completing high-pressure common rail system multiple injection spray development characteristic test experiments of each working condition; S3. Processing high-pressure common rail system multiple injection spray development process pictures of each working condition to obtain actual spray injection intervals T2 between pre-injection end and main injection start under each working condition; S4. Listing actual spray injection intervals corresponding to control signal injection intervals under each working condition, and summarizing a corresponding relationship formula between them. The high-pressure common rail system multiple injection injection interval determination method provided by the application adopts a spray visualization test method, and solves the problem of differences between control signals and actual sprays caused by injection delay.

Description

Technical Field

[0001] This invention belongs to the field of multiple injection in high-pressure common rail systems for diesel engines, and in particular relates to a method for determining the injection interval of multiple injections in high-pressure common rail systems. Background Technology

[0002] One major advantage of the high-pressure common rail system over other fuel supply systems is its ability to perform multiple injections within a single engine cycle. This multiple injection technology effectively controls NO in diesel engines. X It reduces particulate matter emissions, decreases combustion noise, and improves the overall economy and power of the machine.

[0003] In multi-injection processes, the injection interval (the interval between the end of one injection and the beginning of the next) is a crucial parameter, directly determining the interaction between the first and second fuel injections. If the injection interval is too large, the interaction between adjacent injections weakens, and the excessively long injection interval leads to an excessively long injection duration, affecting the diesel engine's combustion thermal efficiency and failing to meet its requirements. Conversely, if the injection interval is too small, the hydraulic pressure wave generated at the end of the first injection directly influences the next injection, increasing the uncontrollability of the injection quantity, particularly affecting the accuracy of small injection volumes.

[0004] During multiple injection processes, the electronic control system sets different injection intervals by setting control signals. However, due to various delays during the injection process, the injection interval set by the control system is not equal to the actual spray injection interval. What truly affects the in-cylinder fuel injection and interaction process is the fuel spray injection interval. Therefore, it is necessary to explore the correspondence between the control signal injection interval and the actual spray injection interval in order to achieve the ideal actual spray injection interval by accurately setting the control signal. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for determining the injection interval of multiple injections in a high-pressure common rail system, so as to solve the problem of the difference between the control signal and the actual spray caused by the injection delay.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for determining the injection interval of a high-pressure common rail system with multiple injections includes the following steps:

[0008] S1. Build a high-speed photography direct shooting test system for the injection process of the high-pressure common rail system, fill the constant volume incendiary bomb with background gas, adjust the back pressure required for the test, and adopt multiple injection strategies of pre-injection + main injection. Set the injection interval between the end of pre-injection and the start of main injection in the electronic control system. This is the control signal injection interval T1.

[0009] S2. Keeping the total injection quantity constant, set different pre-injection percentages and complete the test of the spray development characteristics of the high-pressure common rail system under various working conditions through multiple injections.

[0010] S3. Process images of the multiple spray development process of the high-pressure common rail system under various working conditions to obtain the actual spray interval T2 between the end of pre-spraying and the start of main spraying under each working condition;

[0011] S4. List the actual spray intervals corresponding to the control signal spray intervals under each operating condition, and summarize the correspondence between the two:

[0012] T1 = T2 + ΔT

[0013] Where △T is the difference between the two injection intervals.

[0014] Furthermore, the high-pressure common rail system injection process high-speed photography direct-shot test system includes an ECU and an oil pump. The oil pump delivers liquid from the oil tank to the injector through the oil rail. A constant-volume combustion bomb is located below the injector, and a heating device is installed inside the constant-volume combustion bomb. Quartz windows are located on opposite sides above the constant-volume combustion bomb, and light sources and high-speed cameras are installed on the exterior of the two sides respectively, so that the spray formed by the injector can be imaged by the high-speed camera. The high-speed camera transmits the captured images to the computer and the ECU respectively. The constant-volume combustion bomb pipeline is connected to the gas cylinder, and a pressure control valve is installed on the pipeline. The pressure control valve and the heating device are both signal-connected to the microcontroller. The ECU is also signal-connected to the oil pump, oil rail, injector, and computer respectively to complete the data acquisition and control of the entire system.

[0015] Furthermore, in order to photograph the development characteristics of a single jet of fuel mist, a single hole with the same diameter as the original orifice needs to be drilled at the center of the nozzle tip of the injector, and the original nozzle of the injector needs to be sealed, allowing only the fuel mist from the center nozzle to be injected into the constant volume projectile, thereby realizing the test of the development process of the single jet of fuel mist.

[0016] Furthermore, in order to simulate the real high injection back pressure in the cylinder, the background gas in step S1 is sulfur hexafluoride, which has a density five times that of air, and the background temperature is set to 303K; the injection interval set in the electronic control system between the end of the pre-injection and the start of the main injection is the time interval between the end of the pre-injection pulse width and the start of the main injection pulse width.

[0017] Furthermore, the specific method of step S2 is as follows: First, conduct experimental tests on the relationship between the single-hole injection quantity and the injection pulse width of the injector under different pressures to obtain the relationship curve between the injection quantity and the injection pulse width under different pressures. Based on this curve, determine the injection pulse width corresponding to the pre-injection quantity required for different pre-injection percentages, and provide input for the control of the pre-injection quantity of the electronic control system.

[0018] Furthermore, the specific method of step S3 is as follows: when processing the spray development process images, the pre-spray end feature image is the last image with continuous oil jets, and the main spray start feature image is the first image with continuous oil jets after the pre-spray ends. Based on the time interval between the images between the pre-spray end and the main spray start, and between two adjacent images, the actual spray interval between the pre-spray end and the main spray start can be obtained.

[0019] Compared with existing technologies, the method for determining the injection interval of a high-pressure common rail system described in this invention has the following advantages:

[0020] (1) The method for determining the injection interval of multiple injections in a high-pressure common rail system described in this invention adopts a spray visualization test method to obtain the actual development process of fuel spray in the cylinder, explores the correspondence between the control signal injection interval and the actual spray injection interval, and can accurately determine the correspondence between the control signal injection interval and the actual spray injection interval of the high-pressure common rail system. This solves the problem of the difference between the control signal and the actual spray caused by the injection delay, and can be used to guide the setting of the injection interval of the control system to obtain the ideal actual spray injection interval. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0022] Figure 1 This is a schematic diagram of the high-speed photography direct-shot test system for the high-pressure common rail system jetting process described in an embodiment of the present invention;

[0023] Figure 2 This is a graph showing the relationship between the injection quantity and the injection pulse width under different injection pressures, as described in the embodiments of the present invention.

[0024] Figure 3 These are the fluorescence value test data of solutions with different fluorescence concentrations at different wavelengths as described in the embodiments of the present invention.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1-Fuel tank; 2-Fuel pump; 3-Electric motor; 4-Fuel rail; 5-Light source; 6-Fuel injector; 7-Quartz window; 8-High-speed camera; 9-Heating device; 10-Pressure control valve; 11-Exhaust valve; 12-Microcontroller; 13-Gas cylinder; 14-Computer; 15-Constant volume incendiary bomb. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0028] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] A method for determining the injection interval of multiple injections in a high-pressure common rail system, such as... Figures 1 to 3 As shown, it includes the following steps:

[0032] S1. Build a high-speed photography direct shooting test system for the injection process of the high-pressure common rail system. Inject background gas into the constant volume incendiary bomb through the air intake system, adjust the back pressure required for the test, and adopt multiple injection strategies of pre-injection + main injection. Set the injection interval between the end of pre-injection and the start of main injection in the electronic control system. This is the control signal injection interval T1.

[0033] The high-pressure common rail system injection process high-speed photography direct-view test system includes an ECU, fuel tank 1, fuel pump 2, electric motor 3, fuel rail 4, light source 5, injector 6, quartz window 7, high-speed camera 8, heating device 9, pressure control valve 10, exhaust valve 11, microcontroller 12, gas cylinder 13, computer 14, and constant-volume combustion bomb 15. One end of the fuel pump 2 is equipped with an electric motor 3, which transports the liquid in the fuel tank 1 to the injector 6 through the fuel rail 4. Below the injector 6 is a constant-volume combustion bomb 15, inside which is installed a heating device 9. Quartz windows 7 are located on opposite sides above the constant-volume combustion bomb 15. A light source 5 is installed outside one quartz window, and the other... A high-speed camera 8 is mounted on the outside of the quartz window 7, and the spray generated by the fuel injector 6 is positioned on the horizontal plane of the quartz window 7, facilitating image acquisition by the high-speed camera 8. The high-speed camera 8 transmits the captured images to the computer 14 and the ECU. The constant-volume combustion bomb 15 is also connected to the outside via two pipelines. One pipeline is equipped with an exhaust valve 11, and the other pipeline is connected to the gas cylinder 13. A pressure control valve 10 is installed on the other pipeline. The pressure control valve 10 and the heating device 9 are both connected to the microcontroller 12. The ECU is also connected to the fuel pump 2, fuel rail 4, fuel injector 6, and computer 14 to complete the data acquisition and control of the entire system. The heating device 9 can be any device or mechanism capable of heating the fuel inside the constant-volume combustion bomb 15.

[0034] To capture the development characteristics of a single-beam fuel mist, the injector 6 needs to be machined, with a single hole of the same diameter as the original orifice drilled at the center of the nozzle tip. During the test, a tooling is used to seal the original nozzle of the injector 6, allowing only the fuel spray from the center nozzle to enter the constant-volume incendiary bomb 15, thereby achieving the test of the single-beam spray development process.

[0035] To simulate the real high injection back pressure inside the cylinder, sulfur hexafluoride, with a density five times that of air, was injected into the constant-volume combustion bomb 15 through gas cylinder 13. Based on the calculation formula for the adiabatic isentropic compression process of a diesel engine and the ideal gas law, the actual background density at top dead center of compression was calculated. By adjusting the background gas pressure inside the constant-volume combustion bomb 15 to simulate the real high-density fuel injection environment inside the cylinder, the background density was adjusted to 60 kg / m³. 3 The background temperature is set to 303K. The injection interval set in the electronic control system between the end of the pre-injection and the start of the main injection is the time interval between the end of the pre-injection pulse width and the start of the main injection pulse width.

[0036] The injection strategy adopts multiple injections of pre-injection + main injection. The injection interval between the end of pre-injection and the start of main injection is set to 0.8ms, 1.0ms and 1.2ms respectively in the electronic control system. The total injection amount of single-hole multiple injection is calculated to be 16.3mg based on the cyclic injection amount of the whole machine calibration point.

[0037] S2. Keeping the total injection quantity constant, set different pre-injection percentages and complete multiple injection spray development characteristic tests of the high-pressure common rail system under various operating conditions; first, conduct test tests on the relationship between the single-hole injection quantity and injection pulse width of the injector under different pressures to obtain the relationship curve between the injection quantity and injection pulse width under different pressures. Based on this curve, determine the injection pulse width corresponding to the pre-injection quantity required for different pre-injection percentages, and provide input for the control of the pre-injection quantity of the electronic control system.

[0038] The specific method is as follows: On an ultra-high pressure fuel supply system test bench, the variation law of single-hole fuel injection quantity of the injector with the injection pulse width under different pressures is tested and studied to obtain the fuel injection quantity curves corresponding to different injection pulse widths under different injection pressures, as shown in the figure. Figure 2 As shown in the figure. Based on the above curves, the injection pulse widths corresponding to different pre-injection percentages of fuel injection to meet the total fuel injection quantity requirements under different injection pressures can be obtained. By setting the target pulse width in the control system, the target pre-injection and main injection fuel injection quantities required for the ultra-high pressure spray visualization test can be obtained.

[0039] S3. Process images of the multiple spray development process of the high-pressure common rail system under various working conditions to obtain the actual spray interval T2 between the end of pre-spraying and the start of main spraying under each working condition;

[0040] When processing images of the spray development process, the pre-spray end feature image is the last image with continuous oil jets, and the main spray start feature image is the first image with continuous oil jets after the pre-spray ends. Based on the time interval between the images of the pre-spray end and the main spray start, and between two adjacent images, the actual spray interval between the pre-spray end and the main spray start can be obtained.

[0041] S4. List the actual spray intervals corresponding to the control signal spray intervals under each operating condition, and summarize the correspondence between the two:

[0042] T1 = T2 + ΔT

[0043] Where △T is the difference between the two injection intervals.

[0044] Specifically, tests were conducted on the development characteristics of multiple spray jets in the high-pressure common rail system under various operating conditions. Images of the actual spray development process were obtained. When processing these images, an example was taken: a spray development image with a control signal pre-main jet interval of 0.4 ms at 220 MPa. Figure 3As shown, the image showing the end of pre-spray is the last image with continuous oil jets (image number 2), and the image showing the start of main spray is the first image with continuous oil jets after the end of pre-spray (image number 5). There are a total of 4 images between the end of pre-spray and the start of main spray, with a time interval of 0.1 ms between adjacent images. Therefore, the actual spray interval between the end of pre-spray and the start of main spray is 0.3 ms. Based on this method, the spray images for each test condition are processed to obtain the actual spray interval corresponding to the control signal spray interval for each condition, as shown in Table 1.

[0045] Table 1

[0046]

[0047] From Table 1, we can conclude that T1 = T2 + 0.1, that is, the difference between the two is ΔT = 0.1 ms.

[0048] Therefore, when setting the ideal spray interval, you only need to set the control signal spray interval to spray interval + 0.1.

[0049] The high-pressure common rail system's multiple injection interval determination method in this scheme adopts a spray visualization test method, which obtains the actual development process of fuel spray in the cylinder, explores the correspondence between the control signal injection interval and the actual spray injection interval, and solves the problem of the difference between the control signal and the actual spray caused by injection delay. It can be used to guide the setting of the control system injection interval to obtain the ideal actual spray injection interval.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the injection interval of a high-pressure common rail system in multiple injections, characterized in that: Includes the following steps: S1. Build a high-speed photography direct-shot test system for the injection process of the high-pressure common rail system, fill the constant volume incendiary bomb with background gas, adjust the back pressure required for the test, and adopt multiple injection strategies of pre-injection + main injection. Set the injection interval between the end of pre-injection and the start of main injection in the electronic control system. This is the control signal injection interval T1. S2. Keeping the total injection quantity constant, set different pre-injection percentages and complete the test of spray development characteristics of high-pressure common rail system under various working conditions; S3. Process images of the multiple spray development process of the high-pressure common rail system under various working conditions to obtain the actual spray interval T2 between the end of pre-spraying and the start of main spraying under each working condition; S4. List the actual spray intervals corresponding to the control signal spray intervals under each operating condition, and summarize the correspondence between the two: Among them, △ T This is the difference between the two injection intervals; In step S3, the specific method is as follows: when processing the spray development process images, the pre-spray end feature image is the last image with continuous oil jets, and the main spray start feature image is the first image with continuous oil jets after the pre-spray ends. Based on the time interval between the images between the pre-spray end and the main spray start, and between two adjacent images, the actual spray interval between the pre-spray end and the main spray start can be obtained.

2. The method for determining the injection interval of a high-pressure common rail system under multiple injections according to claim 1, characterized in that: The high-pressure common rail system injection process high-speed photography direct-shot test system includes an ECU and an oil pump. The oil pump delivers liquid from the oil tank to the injector through the oil rail. A constant-volume combustion bomb is located below the injector, and a heating device is installed inside the constant-volume combustion bomb. Quartz windows are located on opposite sides above the constant-volume combustion bomb, and light sources and high-speed cameras are installed on the exterior of the two sides respectively, so that the spray formed by the injector can be imaged by the high-speed camera. The high-speed camera transmits the captured images to the computer and ECU respectively. The constant-volume combustion bomb pipeline is connected to the gas cylinder, and a pressure control valve is installed on the pipeline. The pressure control valve and the heating device are both connected to the microcontroller. The ECU is also connected to the oil pump, oil rail, injector and computer respectively to complete the data acquisition and control of the entire system.

3. The method for determining the injection interval of a high-pressure common rail system according to claim 2, characterized in that: To capture the development characteristics of a single-jet fuel mist, a single hole with the same diameter as the original orifice needs to be drilled at the center of the nozzle tip of the injector, and the original nozzle of the injector needs to be sealed, allowing fuel spray from only the central nozzle to enter the constant volume projectile, thereby enabling the testing of the single-jet spray development process.

4. The method for determining the injection interval of a high-pressure common rail system under multiple injections according to claim 1, characterized in that: To simulate the real high injection back pressure in the cylinder, the background gas in step S1 is sulfur hexafluoride, which has a density five times that of air, and the background temperature is set to 303K; the injection interval set in the electronic control system between the end of the pre-injection and the start of the main injection is the time interval between the end of the pre-injection pulse width and the start of the main injection pulse width.

5. The method for determining the injection interval of a high-pressure common rail system under multiple injections according to claim 1, characterized in that: The specific method of step S2 is as follows: First, conduct experimental tests on the relationship between the single-hole injection quantity and the injection pulse width of the injector under different pressures to obtain the relationship curve between the injection quantity and the injection pulse width under different pressures. Based on this curve, determine the injection pulse width corresponding to the pre-injection quantity required for different pre-injection percentages, and provide input for the control of the pre-injection quantity of the electronic control system.

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