A method and system for low temperature assisted starting of a diesel engine

Abstract

The present application relates to the technical field of diesel engine low-temperature auxiliary starting, and particularly relates to a diesel engine low-temperature auxiliary starting method and system. When the diesel engine is started at low temperature, if the ambient temperature is lower than a threshold value, then a combustion-supporting agent is quantitatively injected to assist compression ignition. During the starting process, the starting current and the crank angle signal of each cylinder are collected in real time; the synchronization degree of the current amplitude and the crank phase among the cylinders is calculated with a complete four-stroke as an analysis window; a combustion synchronization factor is obtained by comprehensively considering the two factors, and the injection time of the combustion-supporting agent is dynamically adjusted based on the time sequence change trend thereof. Through accurate pressure calculation and quantitative injection control, the present application ensures the stability of the combustion-supporting agent supply, combines the combustion synchronization of all cylinders, so that the system can dynamically adjust the injection time of the combustion-supporting agent according to the actual combustion state, and the starting success rate of the diesel engine at low temperature is improved.

Description

Technical Field

[0001] This invention relates to the technical field of low-temperature auxiliary starting of diesel engines, and specifically to a method and system for low-temperature auxiliary starting of diesel engines. Background Technology

[0002] Diesel engines face multiple difficulties when starting in low-temperature environments: low ambient temperatures cause a sharp increase in engine oil viscosity, increasing frictional resistance in moving parts; fuel atomization quality decreases, resulting in insufficient compression endpoint temperature and pressure; simultaneously, battery capacity deteriorates, reducing starter motor output power. These factors collectively lead to starting difficulties or even failures for diesel engines at low temperatures. Current technologies often use heating wires or flame preheaters to heat the intake air and increase the compression endpoint temperature. In-cylinder preheating plugs directly heat the combustion chamber to increase cylinder temperature. Low-ignition-point combustion improvers (such as ethers) are injected into the intake manifold or combustion chamber to lower the compression ignition conditions of the fuel.

[0003] However, the preheating device has high energy consumption, long preheating time, and cannot be dynamically adjusted according to the actual combustion state. In reality, there is a lack of real-time monitoring and feedback on the actual combustion effect. When the combustion efficiency decreases due to factors such as pressure fluctuations and fuel quality differences, the system cannot make corresponding adjustments. Summary of the Invention

[0004] To address the technical problems of high energy consumption, long preheating time, and inability to dynamically adjust preheating devices based on actual combustion conditions, as well as the lack of real-time monitoring and feedback on actual combustion effects, and the inability of the system to make corresponding adjustments when combustion efficiency decreases due to factors such as pressure fluctuations and fuel quality differences, this invention aims to provide a method and system for assisting the low-temperature starting of a diesel engine. The specific technical solution adopted is as follows: A method for assisting the low-temperature starting of a diesel engine, comprising: during the low-temperature starting process of the diesel engine, when the ambient temperature is lower than a preset threshold, quantitatively injecting a combustion-supporting agent to assist compression ignition; and when the diesel engine is started, collecting data from all cylinders at each preset sampling time. The starting current signal and crankshaft angle signal are used; each complete four-stroke cycle of the diesel engine is taken as a time analysis window; in each time analysis window, the amplitude synchronization degree between all cylinders in each time analysis window is obtained based on the change characteristics of the starting current signal between each cylinder and other cylinders; in each time analysis window, the phase synchronization degree between all cylinders in each time analysis window is obtained based on the change characteristics of the crankshaft angle signal between each cylinder and other cylinders; based on the amplitude synchronization degree and phase synchronization degree, the combustion synchronization factor between all cylinders is obtained; based on the temporal change trend of the combustion synchronization factor, the injection time of the quantitative injection of the combustion-supporting agent is adjusted.

[0005] Furthermore, the method for obtaining the amplitude synchronization degree includes: in each time analysis window, the difference between the peak value of the starting current signal of each cylinder and the trough value of the next starting current signal is taken as the peak amplitude of the starting current signal of each cylinder in each time analysis window; the amplitude synchronization degree is obtained according to the amplitude synchronization degree calculation formula, which is shown below: In the formula, This indicates the degree of amplitude synchronization among all cylinders; This represents the standard deviation of the peak amplitude of the starting current signal for all cylinders. This represents the average peak amplitude of the starting current signal for all cylinders.

[0006] Furthermore, the method for obtaining the phase synchronization degree includes: arranging the peak phases of each cylinder according to the corresponding time sequence of the peaks in each time analysis window; calculating the phase difference between adjacent peak phases; and obtaining the phase synchronization degree between all cylinders in each time analysis window based on the phase deviation between each phase difference and the preset ideal phase difference. The calculation formula is as follows: In the formula, This indicates the degree of phase synchronization among all cylinders in each time analysis window; The standard deviation of the phase difference between adjacent wave crests; This indicates the preset ideal phase difference.

[0007] Furthermore, the method for obtaining the combustion synchronization factor includes: taking the arithmetic mean between the amplitude synchronization degree and the phase synchronization degree as the combustion synchronization factor among all cylinders.

[0008] Furthermore, based on the temporal variation trend of the combustion synchronization factor, the injection time of the quantitative injection of the combustion accelerator is adjusted, including: arranging all combustion synchronization factors within a preset time length according to time sequence to obtain a combustion synchronization factor sequence; performing trend decomposition on the combustion synchronization factor sequence to extract the trend term of the combustion synchronization factor sequence; when the trend term shows a downward trend, the injection interval is shortened by advancing the start time of the next combustion accelerator injection.

[0009] Furthermore, the injection interval is shortened by advancing the start time of the next combustion-supporting agent injection, including: calculating the slope of the five most recent points in the trend term as the first slope; when the first slope is less than 0, adjusting the preset injection time at each preset sampling time, and the formula for calculating the time adjustment is as follows: In the formula, Indicates the amount of time adjustment; This represents the first slope of the last 5 points in the trend term; the adjusted injection time at each preset sampling time is obtained by subtracting the time adjustment amount from the preset injection time at each preset sampling time.

[0010] A diesel engine low-temperature auxiliary starting system includes: a temperature sensing module for quantitatively injecting combustion-supporting agent to assist compression ignition when the ambient temperature is below a preset threshold during the low-temperature starting process of the diesel engine; a combustion-supporting agent supply module, including a storage tank, an injection valve, and a pressure maintaining mechanism, for performing quantitative injection; a signal acquisition module for acquiring the starting current signal and crankshaft angle signal of all cylinders at each preset sampling time when the diesel engine is started; using each complete four-stroke cycle of the diesel engine as each time analysis window; obtaining the amplitude synchronization degree between all cylinders in each time analysis window based on the change characteristics of the starting current signal between each cylinder and other cylinders in each time analysis window; obtaining the phase synchronization degree between all cylinders in each time analysis window based on the change characteristics of the crankshaft angle signal between each cylinder and other cylinders in each time analysis window; obtaining the combustion synchronization factor between all cylinders based on the amplitude synchronization degree and the phase synchronization degree; and a control module for adjusting the injection time of the quantitative injection of combustion-supporting agent according to the temporal change trend of the combustion synchronization factor.

[0011] Furthermore, the pressure maintenance structure in the combustion-supporting agent supply module includes an inert gas encapsulated in a storage tank, and the control module is also configured to monitor or predict the pressure inside the tank based on the ideal gas law and the saturated vapor pressure model of the combustion-supporting agent.

[0012] Furthermore, based on the ideal gas law and the saturated vapor pressure model of the combustion-supporting agent, the pressure inside the tank is monitored or predicted, including: collecting the temperature and volume of the storage tank at each preset sampling time; obtaining the saturated vapor pressure of the combustion-supporting agent based on the temperature and volume of the storage tank; calculating the partial pressure of the inert gas based on the saturated vapor pressure of the combustion-supporting agent, the volume of the storage tank, the amount of inert gas, and the temperature inside the storage tank, according to the ideal gas law; and obtaining the theoretical total pressure of the storage tank at each preset sampling time based on the saturated vapor pressure of the combustion-supporting agent and the partial pressure of the inert gas.

[0013] This invention has the following beneficial effects: When the ambient temperature is below a preset threshold, the invention activates a low-temperature assisted starting system to quantitatively inject combustion-supporting agent to assist compression ignition. Since the nozzles are installed in the opposite direction to the air filter intake during the fuel injection process to ensure that the combustion-supporting agent is fully mixed with air and uniformly enters each cylinder, a decrease in compression ignition efficiency can lead to a deviation in cylinder synchronization. Furthermore, in each complete four-stroke cycle of a diesel engine, all cylinders undergo one compression stroke. Therefore, each complete four-stroke cycle of the diesel engine is used as a time analysis window. The changes in the starting current signal and crankshaft angle signal between all cylinders within each time analysis window are analyzed to obtain the amplitude synchronization degree and combustion synchronization factor. This is then combined to obtain the combustion synchronization factor between all cylinders. When the combustion synchronization factor decreases, it indicates that the combustion efficiency of the cylinder is reduced. At this time, the combustion efficiency is compensated for by dynamically adjusting the combustion-supporting agent injection time and advancing the start time of the next injection. This invention ensures the stability of the combustion-supporting agent supply through precise pressure calculation and quantitative injection control. Combined with the combustion synchronization of all cylinders, the system can dynamically adjust the combustion-supporting agent injection time according to the actual combustion state, thereby improving the start-up success rate of diesel engines at low temperatures. Attached Figure Description

[0014] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a flowchart of a low-temperature auxiliary starting method for a diesel engine provided in one embodiment of the present invention; Figure 2 This is a block diagram of a low-temperature auxiliary starting system for a diesel engine provided in one embodiment of the present invention. Detailed Implementation

[0016] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a diesel engine low-temperature auxiliary starting method and system proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] The following description, in conjunction with the accompanying drawings, details a specific scheme for a diesel engine low-temperature auxiliary starting method and system provided by the present invention.

[0019] Please see Figure 1 The present invention illustrates a method for assisting the low-temperature start of a diesel engine according to an embodiment of the present invention. The method includes: step S1: during the low-temperature start of the diesel engine, when the ambient temperature is less than a preset threshold, a combustion aid is quantitatively injected to assist compression ignition.

[0020] This invention primarily addresses the scenario of successfully starting a diesel engine in low-temperature environments. Therefore, a temperature sensor is first installed in the diesel engine compartment to monitor the ambient temperature in real time. When the ECU receives the start signal from the ignition switch, it first reads the temperature sensor value. If the temperature is higher than a preset threshold, the diesel engine is started according to the normal procedure, and the low-temperature start assist system does not operate. If the ambient temperature is lower than the preset threshold, the ECU activates the low-temperature start assist system.

[0021] In one embodiment of the present invention, the preset threshold is set to -10℃. It should be noted that the preset threshold can be set by itself and is not limited here.

[0022] To analyze the actual changes in engine combustion state and avoid interference from the amount of oxidizer injected, the oxidizer is set to be injected in a fixed quantity. The ECU controls the injection valve to operate according to a preset fixed-quantity injection strategy. The injection parameters are set as follows: injection flow rate is set to 0.0007 L / s and kept constant; injection cycle is set to once per second; injection duration per second is set to 0.19 s; and the buffer time for the injection valve to fully open and close is defined as 20% of the injection duration. This buffer time occurs after injection and is adjacent to the injection time. Therefore, the total time occupied by the injection valve per second is... At this point, the injection valve needs to be set to start injecting 0.772 seconds before the start time.

[0023] Since the normal operation of the injection valve's quantitative injection function depends on the stability of the inlet pressure, in order to ensure that the combustion-supporting agent is injected at a constant flow rate, this embodiment of the invention sets up a pressure-maintaining structure in the combustion-supporting agent storage tank. This structure can monitor or predict the pressure inside the tank based on the ideal gas law and the saturated vapor pressure model of the combustion-supporting agent. The specific steps include: First, there is an inert gas in the storage tank to maintain stability. Therefore, the amount of inert gas is calculated using the initial parameters of the storage tank under normal conditions (25°C). Specifically, this embodiment of the invention uses a pressure tank with a volume of 1.3L as the combustion-supporting agent storage tank, wherein the liquid phase volume of the combustion-supporting agent is 0.84L, and the gas phase volume of the inert gas inside the tank is... It is 0.46L.

[0024] exist Based on existing technology, the initial total pressure inside the tank is... for Total saturated vapor pressure of combustion-supporting agent This allows us to obtain the partial pressure of the inert gas inside the tank at this time. for .

[0025] Since the partial pressure of an inert gas changes with temperature according to the ideal gas law, the ideal gas constant in the equation... thermodynamic temperature for The amount of inert gas at this time for: .

[0026] Secondly, at each preset sampling time, the temperature inside the storage tank is collected; the volume of the injected combustion oxidizer is calculated as the liquid phase volume, and then the current gas phase volume is obtained by subtracting the current liquid phase volume from the storage tank volume; based on the temperature inside the storage tank, the total saturated vapor pressure of the combustion oxidizer corresponding to that temperature is obtained by consulting the combustion oxidizer saturated vapor pressure table. In one embodiment of the present invention, the preset sampling time is set to 1 second. It should be noted that the preset sampling time can be set by the user and is not limited here.

[0027] Based on the saturated vapor pressure of the combustion-supporting agent, the volume of the storage tank, the amount of inert gas, and the temperature inside the storage tank, the partial pressure of the inert gas is calculated according to the ideal gas law, as shown in the following formula: In the formula, Indicates the first The partial pressure of inert gas at each preset sampling time; Indicates the first The amount of inert gas in the storage tank at a preset sampling time; Represents the ideal gas constant; Indicates the first Temperature of the storage tank at a preset sampling time; This indicates the volume of the gas phase inside the storage tank.

[0028] The first The theoretical total pressure of the storage tank is obtained by adding the partial pressure of the inert gas at each preset sampling time to the total saturated vapor pressure of the combustion-supporting agent corresponding to the temperature at that time.

[0029] When the theoretical total pressure of the storage tank is lower than the minimum pressure required to maintain the metered injection, the instantaneous flow rate of the combustion accelerator decreases, and external equipment is activated to assist in pressurization. A micro air pump integrated in the storage tank replenishes the space inside the tank with inert gas, maintaining the theoretical total pressure of the storage tank at the minimum pressure required for metered injection.

[0030] Step S2: When the diesel engine is started, collect the starting current signal and crankshaft angle signal of all cylinders at each preset sampling time; take each complete four-stroke cycle of the diesel engine as each time analysis window; in each time analysis window, obtain the amplitude synchronization degree between all cylinders in each time analysis window based on the change characteristics of the starting current signal between each cylinder and other cylinders; in each time analysis window, obtain the phase synchronization degree between all cylinders in each time analysis window based on the change characteristics of the crankshaft angle signal between each cylinder and other cylinders; obtain the combustion synchronization factor between all cylinders based on the amplitude synchronization degree and the phase synchronization degree.

[0031] In diesel engines, the fuel injection nozzles are installed in the opposite direction to the air filter intake during the fuel injection process to ensure that the fuel and air are fully mixed and evenly enter each cylinder. If the compression ignition efficiency decreases, the cylinder synchronization will be deviated. In addition, in each complete four-stroke cycle of a diesel engine, all cylinders will perform a compression stroke. Therefore, in this embodiment of the invention, each complete four-stroke cycle of the diesel engine is used as a time analysis window. The change characteristics of the starting current signal and crankshaft angle signal between all cylinders in each time analysis window are analyzed to obtain the amplitude synchronization degree and combustion synchronization factor. Then, the combustion synchronization factor between all cylinders is obtained by combining them.

[0032] Preferably, in one embodiment of the present invention, the method for obtaining the amplitude synchronization degree includes: in each time analysis window, since a significant peak appears in the starting current signal corresponding to the compression stroke of each cylinder, the difference between the peak value of the starting current signal of each cylinder and the trough value of the next starting current signal is used as the peak amplitude of the starting current signal of each cylinder in each time analysis window; the amplitude synchronization degree is obtained according to the amplitude synchronization degree calculation formula, which is shown below: In the formula, This indicates the degree of amplitude synchronization among all cylinders; This represents the standard deviation of the peak amplitude of the starting current signal for all cylinders. This represents the average peak amplitude of the starting current signal for all cylinders.

[0033] In the formula for calculating the degree of amplitude synchronization, when the peak amplitude of the starting current signal of each cylinder is the same, the degree of amplitude synchronization among all cylinders is the highest. The standard deviation of the peak amplitude of the starting current signal of all cylinders is 0, and the degree of amplitude synchronization among all cylinders is 1, reaching the maximum value. When the dispersion of the peak amplitude of the starting current signal of all cylinders is greater than the mean of the peak amplitude, the degree of amplitude synchronization among cylinders is negative. At this time, the difference in combustion efficiency among all cylinders is more obvious.

[0034] Since the crankshaft angle of a diesel engine is 720° in each complete four-stroke cycle, and in this embodiment of the invention, the diesel engine involved is a 4-cylinder four-stroke engine, the crankshaft angle interval for each cylinder to perform power stroke is 180° under ideal conditions. That is, when adjacent cylinders perform compression stroke, the phase difference of the starting current signal is 180°. At this time, the preset ideal phase difference is set to 180°.

[0035] Preferably, in one embodiment of the present invention, the method for obtaining the phase synchronization degree includes: since the firing order of the cylinders in a four-cylinder four-stroke engine is cylinder 1, cylinder 3, cylinder 4, and cylinder 2, the peak of cylinder 1 appears in the 0°-180° range, the peak of cylinder 3 appears in the 180°-360° range, the peak of cylinder 4 appears in the 360°-540° range, and the peak of cylinder 2 appears in the 540°-720° range; in each time analysis window, the peak phases of each cylinder are arranged according to the corresponding time sequence of the peaks; the phase difference between adjacent peak phases is calculated; based on the phase deviation between each phase difference and the preset ideal phase difference, the phase synchronization degree between all cylinders in each time analysis window is obtained, and the calculation formula is as follows: In the formula, This indicates the degree of phase synchronization among all cylinders in each time analysis window; The standard deviation of the phase difference between adjacent wave crests; This indicates the preset ideal phase difference.

[0036] In the above formula, ,in, This indicates the corresponding phase of the peak value of the starting current signal of cylinder 1; This indicates the corresponding phase of the peak value of the starting current signal of cylinder 3; This indicates the corresponding phase of the peak value of the starting current signal of cylinder 4; This represents the corresponding phase of the peak value of the starting current signal for cylinder 2; in the formula for calculating the standard deviation of the phase difference between adjacent peak phases, the smaller the difference between each cylinder and the preset ideal phase difference, the better. The smaller the value, the more likely the crankshaft is to be in an ideal position when the cylinder performs the compression stroke. At this time, the phase between cylinders is more synchronized, and the combustion efficiency between different cylinders is more similar.

[0037] Preferably, in one embodiment of the present invention, the method for obtaining the combustion synchronization factor includes: taking the arithmetic mean between the amplitude synchronization degree and the phase synchronization degree as the combustion synchronization factor among all cylinders.

[0038] Step S3: Adjust the injection time of the quantitative injection of the combustion accelerator according to the temporal change trend of the combustion synchronization factor.

[0039] When the combustion synchronization factor decreases, it indicates that the combustion efficiency of the cylinder is reduced. At this time, the reduction in combustion efficiency can be compensated by dynamically adjusting the timing of the fuel injection and advancing the start time of the next injection.

[0040] Preferably, in one embodiment of the present invention, adjusting the injection time of the quantitative injection of the combustion accelerator according to the temporal variation trend of the combustion synchronization factor includes: arranging all combustion synchronization factors within a preset time length in temporal order to obtain a combustion synchronization factor sequence; in one embodiment of the present invention, the preset time length is set to all times from ECU ignition to the current preset sampling time.

[0041] The combustion synchronization factor sequence is decomposed to extract the trend term. When the trend term shows a downward trend, the injection interval is shortened by advancing the start time of the next oxidizer injection. Specifically, this involves calculating the slope of the last 5 points in the trend term as the first slope. When the first slope is less than 0, the preset injection time at each preset sampling time is adjusted. The formula for calculating the time adjustment is as follows: In the formula, Indicates the amount of time adjustment; This represents the first slope of the last 5 points in the trend term; the adjusted injection time at each preset sampling time is obtained by subtracting the time adjustment amount from the preset injection time at each preset sampling time.

[0042] By continuously adjusting the propellant injection timing, the combustion efficiency between cylinders is restored to normal. At this point, the adjustment of the injection valve timing is stopped. Specific methods include: if engine surging occurs after startup, the ECU illuminates the manual mode indicator. The driver presses the mode switch, and the system enters manual mode. The control module continuously adjusts the propellant injection timing. When the ECU detects that the diesel engine speed is consistently higher than the idle speed (e.g., 600 rpm) for 3 seconds and the combustion synchronization factor is greater than 0.9, it determines that the start is successful. After releasing the button, the system automatically stops working.

[0043] This completes the low-temperature auxiliary start of the diesel engine.

[0044] In summary, during the low-temperature start-up of a diesel engine, when the ambient temperature is below a preset threshold, a metered injection of combustion improver is performed to assist compression ignition. During engine startup, starting current and crankshaft angle signals from all cylinders are collected at each preset sampling time. Each complete four-stroke cycle of the diesel engine is used as a time analysis window. Within each time analysis window, the amplitude synchronization degree between all cylinders is obtained based on the characteristics of the starting current signal changes between each cylinder and other cylinders. Similarly, the phase synchronization degree between all cylinders is obtained based on the characteristics of the crankshaft angle signal changes between each cylinder and other cylinders. The combustion synchronization factor between all cylinders is obtained based on the amplitude and phase synchronization degrees. The injection time of the metered combustion improver injection is adjusted according to the temporal variation trend of the combustion synchronization factor.

[0045] One embodiment of the present invention provides a low-temperature auxiliary starting system for a diesel engine. The system includes a memory, a processor, and a computer program. The memory stores the corresponding computer program, and the processor runs the corresponding computer program. When the computer program runs in the processor, it can implement the methods described in steps S1-S3, specifically including: a temperature sensing module 101, used to quantitatively inject combustion-supporting agent to assist compression ignition when the ambient temperature is lower than a preset threshold during the low-temperature starting process of the diesel engine; a combustion-supporting agent supply module 102, including a storage tank, an injection valve, and a pressure maintaining mechanism, used to perform quantitative injection; and a signal acquisition and analysis module 103, used to acquire the signal of all cylinders at each preset sampling time when the diesel engine is started. The starting current signal and crankshaft angle signal are used; each complete four-stroke cycle of the diesel engine is taken as a time analysis window; in each time analysis window, the amplitude synchronization degree between all cylinders in each time analysis window is obtained based on the change characteristics of the starting current signal between each cylinder and other cylinders; in each time analysis window, the phase synchronization degree between all cylinders in each time analysis window is obtained based on the change characteristics of the crankshaft angle signal between each cylinder and other cylinders; the combustion synchronization factor between all cylinders is obtained based on the amplitude synchronization degree and the phase synchronization degree; the control module 104 is used to adjust the injection time of the quantitative injection of the combustion accelerator according to the temporal change trend of the combustion synchronization factor.

[0046] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0047] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for assisting the starting of a diesel engine at low temperatures, characterized in that, The method includes: during the low-temperature start-up of a diesel engine, when the ambient temperature is below a preset threshold, quantitatively injecting an oxidizer to assist compression ignition; when the diesel engine is started, collecting the starting current signal and crankshaft angle signal of all cylinders at each preset sampling time; using each complete four-stroke cycle of the diesel engine as each time analysis window; in each time analysis window, obtaining the amplitude synchronization degree between all cylinders in each time analysis window based on the change characteristics of the starting current signal between each cylinder and other cylinders; in each time analysis window, obtaining the phase synchronization degree between all cylinders in each time analysis window based on the change characteristics of the crankshaft angle signal between each cylinder and other cylinders; obtaining the combustion synchronization factor between all cylinders based on the amplitude synchronization degree and the phase synchronization degree; and adjusting the injection time of the quantitative oxidizer injection based on the temporal change trend of the combustion synchronization factor.

2. The method for assisting the starting of a diesel engine at low temperatures according to claim 1, characterized in that, The method for obtaining the amplitude synchronization degree includes: in each time analysis window, taking the difference between the peak value of the starting current signal of each cylinder and the trough value of the next starting current signal as the peak amplitude of the starting current signal of each cylinder in each time analysis window; and obtaining the amplitude synchronization degree according to the amplitude synchronization degree calculation formula, which is as follows: In the formula, This indicates the degree of amplitude synchronization among all cylinders; This represents the standard deviation of the peak amplitude of the starting current signal for all cylinders. This represents the average peak amplitude of the starting current signal for all cylinders.

3. The method for assisting the starting of a diesel engine at low temperatures according to claim 1, characterized in that, The method for obtaining the phase synchronization degree includes: arranging the peak phases of each cylinder according to the corresponding time sequence of the peaks in each time analysis window; calculating the phase difference between adjacent peak phases; and obtaining the phase synchronization degree between all cylinders in each time analysis window based on the phase deviation between each phase difference and a preset ideal phase difference. The calculation formula is as follows: In the formula, This indicates the degree of phase synchronization among all cylinders in each time analysis window; The standard deviation of the phase difference between adjacent wave crests; This indicates the preset ideal phase difference.

4. The method for assisting the starting of a diesel engine at low temperatures according to claim 1, characterized in that, The method for obtaining the combustion synchronization factor includes: taking the arithmetic mean between the amplitude synchronization degree and the phase synchronization degree as the combustion synchronization factor among all cylinders.

5. A method for assisting the starting of a diesel engine at low temperatures according to claim 1, characterized in that, Based on the temporal variation trend of the combustion synchronization factor, the injection time of the quantitative injection of the combustion accelerator is adjusted, including: arranging all combustion synchronization factors within a preset time length according to time sequence to obtain a combustion synchronization factor sequence; performing trend decomposition on the combustion synchronization factor sequence to extract the trend term of the combustion synchronization factor sequence; when the trend term shows a downward trend, the injection interval is shortened by advancing the start time of the next combustion accelerator injection.

6. A method for assisting the starting of a diesel engine at low temperatures according to claim 5, characterized in that, The injection interval is shortened by advancing the start time of the next combustion-supporting agent injection, including: calculating the slope of the most recent 5 points in the trend term as the first slope; when the first slope is less than 0, adjusting the preset injection time at each preset sampling time, and the time adjustment amount is calculated as follows: In the formula, Indicates the amount of time adjustment; This represents the first slope of the last 5 points in the trend term; the adjusted injection time at each preset sampling time is obtained by subtracting the time adjustment amount from the preset injection time at each preset sampling time.

7. A low-temperature auxiliary starting system for a diesel engine, characterized in that, The system for implementing the method of any one of claims 1 to 8 comprises: a temperature sensing module for quantitatively injecting an oxidizer to assist compression ignition when the ambient temperature is less than a preset threshold during the low-temperature start-up of a diesel engine; an oxidizer supply module, including a storage tank, an injection valve, and a pressure maintaining mechanism, for performing quantitative injection; a signal acquisition and analysis module for acquiring the starting current signal and crankshaft angle signal of all cylinders at each preset sampling time when the diesel engine is started; using each complete four-stroke cycle of the diesel engine as each time analysis window; obtaining the amplitude synchronization degree between all cylinders in each time analysis window based on the change characteristics of the starting current signal between each cylinder and other cylinders in each time analysis window; obtaining the phase synchronization degree between all cylinders in each time analysis window based on the change characteristics of the crankshaft angle signal between each cylinder and other cylinders in each time analysis window; obtaining the combustion synchronization factor between all cylinders based on the amplitude synchronization degree and the phase synchronization degree; and a control module for adjusting the injection time of the quantitative oxidizer injection according to the temporal change trend of the combustion synchronization factor.

8. A diesel engine low-temperature auxiliary starting system according to claim 7, characterized in that, The pressure maintenance structure in the combustion-supporting agent supply module includes an inert gas encapsulated in the storage tank, and the control module is also configured to monitor or predict the pressure inside the tank based on the ideal gas law and the saturated vapor pressure model of the combustion-supporting agent.

9. A diesel engine low-temperature auxiliary starting system according to claim 8, characterized in that, Based on the ideal gas law and the saturated vapor pressure model of the combustion-supporting agent, the pressure inside the tank is monitored or predicted, including: collecting the temperature and volume of the combustion-supporting agent inside the storage tank at each preset sampling time; obtaining the saturated vapor pressure of the combustion-supporting agent based on the temperature and volume of the combustion-supporting agent inside the storage tank; calculating the partial pressure of the inert gas based on the saturated vapor pressure of the combustion-supporting agent, the volume of the storage tank, the amount of inert gas, and the temperature inside the storage tank according to the ideal gas law; and obtaining the theoretical total pressure of the storage tank at each preset sampling time based on the saturated vapor pressure of the combustion-supporting agent and the partial pressure of the inert gas.

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