A gas injection control method and system based on flow area regulation

Abstract

The application discloses a kind of based on flow area regulation and control gas injection control method and system, the control method includes: the back pressure at the outlet of injection valve and the pressure in the pre-valve common rail pipe are obtained, the ratio of back pressure and pressure is calculated;Whether the ratio of back pressure and pressure is less than or equal to critical pressure ratio is judged;If yes, then the injection amount of injection valve is adjusted by adjusting the flow area of injection valve;If no, then the pressure in the pre-valve common rail pipe is increased until the ratio of back pressure and pressure is less than or equal to critical pressure ratio, and then the injection amount of injection valve is adjusted by adjusting the flow area of injection valve;The method has the advantages of pressure control type gas injection strategy and time control type gas injection strategy, while avoiding uneven mixture during adjusting gas injection amount, and meeting the adjustment frequency and pressure stability under the condition of frequent changes.

Description

Technical Field

[0001] This invention relates to the field of gas injection control methods, specifically to a gas injection control method and system based on flow area regulation. Background Technology

[0002] Gas injection systems were initially based on time-controlled modes, followed by multi-point injection systems with pressure-controlled modes. Pressure-controlled gas supply systems differ from time-controlled systems. For multi-point injection, time-controlled systems control engine load by adjusting the injection pulse width of the gas injection valves, while pressure-controlled systems control engine load by adjusting the pressure within the common rail.

[0003] Multi-point gas injection systems based on time-controlled modes control the gas injection quantity by controlling the injection duration. This is achieved by controlling the opening and closing times of a high-speed solenoid valve; the length of time the solenoid valve is open controls the amount of fuel supplied. Under different loads, the injection pressure remains essentially constant, while the injection duration varies. For example... Figure 1 As shown, during the intake valve opening process, apart from a portion of the time spent on scavenging, combustion gas injection can be organized for most of the intake process. Under high engine load, the injection duration is longer to provide sufficient injection volume; while under low load, the injection duration is very short. With combustion gas injection, the injected combustion gas and the intake air enter the cylinder together; without combustion gas injection, only air may enter the cylinder, which is not conducive to the formation of a homogeneous mixture between the combustion gas and air.

[0004] To facilitate the mixing of fuel gas and air, existing multi-point fuel injection systems based on pressure control primarily control the fuel injection quantity by adjusting the fuel injection pressure. In time-controlled multi-point fuel injection systems, a common rail and a pressure regulating valve are added. By controlling the opening of the pressure regulating valve, the amount of fuel entering the common rail is controlled, thereby controlling the fuel pressure within the common rail. Its structure is as follows: Figure 2 As shown, under high load, the gas pressure in the common rail is increased by controlling the opening of the gas pressure regulating valve. Under medium and low load, the gas pressure in the common rail is decreased by controlling the opening of the gas pressure regulating valve, maintaining the injection duration approximately constant to improve the air-fuel mixture quality under medium and low loads. However, the implementation of a multi-point gas injection system in pressure control mode relies on the gas pressure regulating valve to adjust the pressure in the common rail. Stabilizing the pressure in the common rail at the target injection pressure requires a certain period of time. Therefore, under high-speed operating conditions, the adjustment speed cannot be guaranteed, and the gas pressure stability in the common rail is insufficient, which is detrimental to intake flow control under frequent changes in operating conditions. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a gas injection control method and system based on flow area regulation. By adjusting the flow area of ​​the injection valve during the gas injection process, the gas injection quantity can be controlled, which can meet the requirements of frequency adjustment and pressure stability under frequent changes in operating conditions.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, a gas injection control method based on flow area regulation is provided, comprising the following steps:

[0008] Obtain the back pressure at the outlet of the injection valve and the pressure in the common rail before the valve, and calculate the ratio of back pressure to pressure.

[0009] Determine whether the ratio of back pressure to pressure is less than or equal to the critical pressure ratio;

[0010] If so, the injection volume of the injection valve is adjusted by adjusting the flow area of ​​the injection valve.

[0011] If not, increase the pressure in the common rail before the valve until the ratio of back pressure to pressure is less than or equal to the critical pressure ratio, and then adjust the injection volume of the injection valve by adjusting the flow area of ​​the injection valve.

[0012] In some embodiments of the present invention, the injection quantity of the injection valve per unit time is calculated according to the following formula:

[0013]

[0014] In the formula, A is the flow area; κ is the isentropic exponent; p0 is the stagnation pressure; ν0 is the stagnation pressure ratio; where κ, p0, and ν0 are all constants, the injection volume of the injection valve per unit time is directly proportional to the flow area, and the injection volume of the injection valve is adjusted by changing the flow area.

[0015] In some embodiments of the present invention, the critical pressure ratio is the ratio of the working fluid pressure to the stagnation pressure when the working fluid flow rate reaches the local speed of sound.

[0016] In some embodiments of the present invention, when the ratio of the back pressure at the outlet of the injection valve to the pressure in the common rail before the valve is less than or equal to the critical pressure ratio, the injection valve operates in the supercritical sonic flow region, and the injection quantity of the injection valve is not affected by the back pressure at the outlet of the injection valve.

[0017] In some embodiments of the present invention, the amount of gas injected depends on the load of the engine under different operating conditions, and the duration of gas injection depends on the engine speed and the number of cylinders; the start of the injection duration is later than the start of the gas injection time, and the end of the injection duration is earlier than the end of the gas injection time.

[0018] In some embodiments of the present invention, the injection valve is disposed on the common gas rail, and the common gas rail is connected to the gas storage tank via a gas control valve.

[0019] In some embodiments of the present invention, a temperature sensor and a pressure sensor are provided on the common gas rail.

[0020] In a second aspect of the invention, a gas injection control system based on flow area regulation is provided, characterized in that it comprises:

[0021] The data acquisition module is configured to: acquire the back pressure at the outlet of the injection valve and the pressure in the common rail before the valve, and calculate the ratio of back pressure to pressure;

[0022] The judgment module is configured to: determine whether the ratio of back pressure to pressure is less than or equal to the critical pressure ratio;

[0023] The control module is configured to: if so, adjust the injection volume of the injection valve by adjusting the flow area of ​​the injection valve;

[0024] If not, increase the pressure in the common rail before the valve until the ratio of back pressure to pressure is less than or equal to the critical pressure ratio, and then adjust the injection volume of the injection valve by adjusting the flow area of ​​the injection valve.

[0025] In a third aspect of the invention, a computer-readable storage medium is provided having a program stored thereon, characterized in that, when executed by a processor, the program implements the steps in the gas injection control method based on flow area regulation.

[0026] In a fourth aspect of the invention, an electronic device is provided, including a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that the processor executes the program to implement the steps in the gas injection control method based on flow area regulation.

[0027] One or more technical solutions of the present invention have the following beneficial effects:

[0028] This invention proposes a gas injection control method based on flow area regulation, which is a multi-point gas injection strategy based on flow area control mode. It mainly controls the gas injection quantity by adjusting the opening area of ​​the injection valve during the gas injection process, thereby changing the flow area of ​​the gas at the injection valve. The injection valve connects to the common rail and the intake passage, injecting gas into the intake passage to mix with air, thus forming "quantity regulation". This method combines the advantages of pressure-controlled and time-controlled gas injection strategies, while avoiding uneven mixture during gas injection quantity adjustment and ensuring stable adjustment frequency and pressure under frequent changes in operating conditions. Attached Figure Description

[0029] Figure 1 This is a flowchart of the gas injection control method based on flow area regulation according to the present invention;

[0030] Figure 2 A diagram of a test system for gas injection in the prior art;

[0031] Figure 3 for Figure 2 A simplified structural diagram of the controlled component in the diagram;

[0032] Figure 4 A graph showing the relationship between the mass flow rate and pressure ratio of the injection valve;

[0033] Figure 5 This is a graph showing the relationship between valve lift and time.

[0034] In the diagram: 1. Compressor; 2. First valve; 3. Pressure stabilizing tank; 4. Second valve; 5. Air filter; 6. Pressure stabilizing valve; 7. Oil mist separator; 8. Gas control valve; 9. Pressure transmitter; 10. Gas supply rail pipe; 11. Injection valve; 12. Pressure transmitter; 13. Temperature sensor; 14. Piezoelectric pressure sensor; 15. Test bench; 16. Gas storage tank. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0036] Example 1

[0037] Existing technologies such as Figure 2 The test bench shown uses compressor 1 as the power source for the gas, and pressure stabilizing tank 3 to stabilize the gas pressure. The gas then passes through common rail 10, gas injection valve 11, and enters the intake manifold. The controlled components are mainly as follows (simplified structure). Figure 3 As shown, the injection valve is installed on the common gas rail 10, which is connected to the gas storage tank 16 via a gas control valve 8. A temperature sensor and a pressure sensor are installed on the common gas rail 10. The back pressure at the outlet of the injection valve 11 is P. b The pressure in the common rail before the valve is P. The main controlled parameters are the gas pressure P in the common rail and the back pressure P of the injection valve. b And the opening area A of the injection valve, during operation, by ensuring that P b / P≤σ * Under certain conditions, it is possible to adjust the injection volume by adjusting the flow area.

[0038] Specifically, the gas injection control method based on flow area regulation provided by this invention, such as... Figure 1 As shown, it includes the following steps:

[0039] Obtain the back pressure P at the outlet of the injection valve b Calculate the ratio of back pressure to pressure by taking the pressure P in the common rail pipe before the valve.

[0040] Determine back pressure P b Is the ratio σ of pressure P less than or equal to the critical pressure ratio σ? * ;

[0041] If so, the injection volume of the injection valve is adjusted by adjusting the flow area A of the injection valve;

[0042] If not, increase the pressure P in the common rail before the valve until the back pressure P b The ratio σ to the pressure is less than or equal to the critical pressure ratio σ. * Then, the injection volume of the injection valve is adjusted by adjusting the flow area A of the injection valve.

[0043] In this embodiment, the injection volume of the injection valve per unit time is calculated according to the following formula:

[0044]

[0045] In the formula, A is the flow area; κ is the isentropic exponent; p0 is the stagnation pressure; ν0 is the stagnation pressure ratio; where κ, p0, and ν0 are all constants, the injection volume of the injection valve per unit time is directly proportional to the flow area, and the injection volume of the injection valve is adjusted by changing the flow area.

[0046] The derivation of the above formula is as follows:

[0047] In pneumatics, the various pneumatic components through which airflow passes are often abstracted as contraction nozzles or throttling orifices. The formula for calculating the mass flow rate through the nozzle is obtained from the continuity equation and the relationship between gas state parameters, as follows.

[0048]

[0049] In the formula: A is the flow area; k is the isentropic exponent; p0 is the stagnation pressure; Figure 4 Point b in the equation represents the critical pressure p. cr The ratio to the stagnation pressure p0.

[0050] In this embodiment, the critical pressure ratio is the ratio of the working fluid pressure to the stagnation pressure when the working fluid velocity reaches the local speed of sound, and is calculated using the following formula:

[0051]

[0052] Where, σ *The critical pressure ratio is the ratio of the working fluid pressure to the stagnation pressure when the flow velocity reaches the local speed of sound. k is the isentropic exponent. Taking air as an example, k = 1.4, and the critical pressure ratio should be σ. * =0.528. When the back pressure of the injection valve is less than the critical pressure, the gas pressure can only expand to the critical pressure P at most because the injection valve cannot provide the gradually expanding cross section required for airflow expansion. cr The maximum gas injection velocity can only reach the local speed of sound. Therefore, when the back pressure of the injection valve is less than the critical pressure p... cr Then, the equation for the injection flow rate of the gas per unit time can be obtained:

[0053]

[0054] When the injection time is t, the total injection flow rate is:

[0055]

[0056] Furthermore, P refers to the pressure of the gas inside the common rail, and p0 is the stagnation pressure of the gas inside the common rail. It is defined as the gas flow velocity stagnating to zero according to a certain process. The parameter at this time is the stagnation parameter. In the calculation process, the gas flow parameters at the inlet before the valve can be expressed by their corresponding stagnation parameters. Therefore, P and p0 are both parameters describing the pressure inside the common rail. Usually, the simplified parameter p0 can be used to replace P.

[0057] pass Figure 4 It can be seen that when the back pressure of the injection valve is greater than the critical pressure, the gas injection quantity increases with the back pressure P. b The injection quantity changes with the back pressure P. When the injection valve pressure is less than the critical pressure, the injection quantity is a constant value and does not change with the back pressure P. b Change with change. Control P b / p0≤σ * (i.e., control P) b / P≤σ * The gas injection valve operates in the supercritical sonic flow region, where the gas flows at the speed of sound. Even if the pressure P at the valve outlet... b If the flow rate continues to decrease without any change in the flow within the injection valve, then Q remains constant. The flow rate at this stage is called the critical flow rate Q.

[0058] like Figure 4As shown in the formula above, the injection quantity is directly proportional to the flow area and injection time, and positively correlated with pressure within a certain range. Time-controlled injection systems maintain a constant injection pressure and adjust the injection time to regulate the gas injection quantity, thereby controlling engine load. Pressure-controlled multi-point injection systems maintain a constant injection time and adjust the injection pressure to regulate the gas injection quantity, thereby controlling engine load. When temperature and injection time remain constant, maintaining the gas in the sonic flow region, the gas injection quantity is only related to the gas flow area. Based on this principle, a flow area-controlled multi-point gas injection system is proposed, which adjusts the injection quantity by controlling the gas flow area to achieve engine quantity regulation.

[0059] Furthermore, the amount of fuel gas injected depends on the engine load under different operating conditions, and the duration of fuel gas injection depends on the engine speed and the number of cylinders; for example... Figure 5 As shown, the injection duration begins later than the start of the fuel injection time, and ends earlier than the end of the fuel injection time. The former prevents the combustion chamber from allowing the burnt-out mixture to flow back into the intake manifold through the intake valve, igniting some of the fresh mixture and causing backfire. The latter ensures that the fuel gas fully enters the cylinder, preventing the mixture from remaining in the intake manifold.

[0060] Example 2

[0061] In a typical embodiment of the present invention, a gas injection control system based on flow area regulation is provided, comprising:

[0062] The data acquisition module is configured to: acquire the back pressure at the outlet of the injection valve and the pressure in the common rail before the valve, and calculate the ratio of back pressure to pressure;

[0063] The judgment module is configured to: determine whether the ratio of back pressure to pressure is less than or equal to the critical pressure ratio;

[0064] The control module is configured to: if so, adjust the injection volume of the injection valve by adjusting the flow area of ​​the injection valve;

[0065] If not, increase the pressure in the common rail before the valve until the ratio of back pressure to pressure is less than or equal to the critical pressure ratio, and then adjust the injection volume of the injection valve by adjusting the flow area of ​​the injection valve.

[0066] Example 3

[0067] The purpose of this embodiment is to provide a computer-readable storage medium.

[0068] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the gas injection control method based on flow area regulation as described in Embodiment 1 of this disclosure.

[0069] Example 4

[0070] The purpose of this embodiment is to provide an electronic device.

[0071] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the gas injection control method based on flow area regulation as described in Embodiment 1 of this disclosure.

[0072] The steps and methods involved in the apparatuses of Embodiments 2, 3, and 4 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0073] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0074] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A gas injection control method based on flow area regulation, characterized in that, Includes the following steps: Obtain the back pressure at the outlet of the injection valve and the pressure in the common rail before the valve, and calculate the ratio of back pressure to pressure. Determine whether the ratio of back pressure to pressure is less than or equal to the critical pressure ratio; If so, the injection volume of the injection valve is adjusted by adjusting the flow area of ​​the injection valve. If not, increase the pressure in the common rail before the valve until the ratio of back pressure to pressure is less than or equal to the critical pressure ratio, and then adjust the injection volume of the injection valve by adjusting the flow area of ​​the injection valve. The critical pressure ratio is the ratio of the working fluid pressure to the stagnation pressure when the working fluid velocity reaches the local speed of sound.

2. The gas injection control method based on flow area regulation as described in claim 1, characterized in that, The injection volume of the injection valve per unit time is calculated according to the following formula: In the formula, For circulation area; It is the isentropic exponent; For stabilizing pressure; The pressure ratio under stagnation conditions; where, , , All are constants. The injection volume per unit time of the injection valve is directly proportional to the flow area. The injection volume of the injection valve can be adjusted by changing the flow area.

3. The gas injection control method based on flow area regulation as described in claim 1, characterized in that, When the ratio of the back pressure at the outlet of the injection valve to the pressure in the common rail before the valve is less than or equal to the critical pressure ratio, the injection valve operates in the supercritical sonic flow region, and the injection quantity of the injection valve is not affected by the back pressure at the outlet of the injection valve.

4. The gas injection control method based on flow area regulation as described in claim 1, characterized in that, The amount of gas injected depends on the engine load under different operating conditions, and the duration of gas injection depends on the engine speed and the number of cylinders. The start of the injection duration is later than the start of the time when gas can be injected, and the end of the injection duration is earlier than the end of the time when gas can be injected.

5. The gas injection control method based on flow area regulation as described in claim 1, characterized in that, The injection valve is installed on the common gas rail, which is connected to the gas storage tank via a gas control valve.

6. The gas injection control method based on flow area regulation as described in claim 5, characterized in that, The common rail gas pipe is equipped with a temperature sensor and a pressure sensor.

7. A gas injection control system based on flow area regulation, characterized in that, include: The data acquisition module is configured to: acquire the back pressure at the outlet of the injection valve and the pressure in the common rail before the valve, and calculate the ratio of back pressure to pressure; The judgment module is configured to: determine whether the ratio of back pressure to pressure is less than or equal to the critical pressure ratio; The control module is configured to: if so, adjust the injection volume of the injection valve by adjusting the flow area of ​​the injection valve; If not, increase the pressure in the common rail before the valve until the ratio of back pressure to pressure is less than or equal to the critical pressure ratio, and then adjust the injection volume of the injection valve by adjusting the flow area of ​​the injection valve. The critical pressure ratio is the ratio of the working fluid pressure to the stagnation pressure when the working fluid velocity reaches the local speed of sound.

8. A computer-readable storage medium having a program stored thereon, characterized in that, When executed by the processor, the program implements the steps in the gas injection control method based on flow area regulation as described in any one of claims 1-5.

9. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the gas injection control method based on flow area regulation as described in any one of claims 1-5.

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