Low pressure egr system without egr valve and method for controlling egr exhaust gas flow thereof

Abstract

The application discloses a low-pressure EGR system without an EGR valve and an EGR exhaust flow control method, which is used for reducing the thermal load of an engine under a high-load working condition and reducing the risk of knocking problems. The application comprises a supercharger, a Venturi tube, a cylinder, an air inlet pipeline and an exhaust pipeline. The air inlet pipeline is connected with an air inlet end of the cylinder. A first end of the exhaust pipeline is fixed on an exhaust end of the cylinder, and a second end of the exhaust pipeline extends to be connected with an aftertreatment device. The supercharger is provided with an air inlet turbine and an exhaust turbine. The air inlet turbine is communicated with the air inlet pipeline, and the exhaust turbine is communicated with the exhaust pipeline. An EGR system pipeline is arranged between the air inlet pipeline and the exhaust pipeline. One end of the EGR system pipeline is connected in front of an air inlet direction of the air inlet turbine, and the other end of the EGR system pipeline is connected behind an exhaust direction of the exhaust turbine. The Venturi tube is arranged in the EGR system pipeline, so that exhaust gas is backflowed to the air inlet pipeline through the EGR system pipeline and the Venturi tube.

Description

Technical Field

[0001] This application relates to the field of engine exhaust gas recycling technology, and in particular to a low-pressure EGR system without an EGR valve and an EGR exhaust gas flow control method. Background Technology

[0002] EGR (Exhaust Gas Recirculation) refers to the process of returning a portion of the exhaust gas from the engine to the intake manifold, where it mixes with fresh air and re-enters the cylinders. Currently, EGR valves are typically used to assist in the exhaust gas recirculation process. An EGR system line is installed between the exhaust and intake manifolds, and the EGR valve is located within this line. By controlling the opening degree of the EGR valve, the flow rate of the recirculated exhaust gas is controlled.

[0003] In existing technologies, one method of exhaust gas recirculation is the high-pressure EGR system. High-pressure EGR refers to the EGR exhaust gas being drawn from in front of the turbocharger turbine, cooled by the EGR cooler, mixed with the fresh air pressurized by the turbocharger, and then entering the cylinder for combustion. The high-pressure EGR system is equipped with an EGR valve, which introduces the required EGR flow by controlling the opening of the EGR valve. However, because the exhaust gas in the high-pressure EGR system is drawn from in front of the turbocharger exhaust turbine, the exhaust gas path is relatively short, and the temperature of the EGR exhaust gas is relatively high. This results in a high thermal load on the engine under heavy load conditions and also increases the risk of knocking.

[0004] Based on this, this application provides a low-pressure EGR system to solve the problems mentioned above. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a low-pressure EGR system without an EGR valve and its control method, which reduces the thermal load on the engine under high load conditions and reduces the risk of knocking.

[0006] The first aspect of this application provides a low-pressure EGR system without an EGR valve, including...

[0007] Supercharger, venturi tube, cylinder, intake manifold and exhaust manifold;

[0008] The intake pipe is connected to the intake end of the cylinder;

[0009] The first end of the exhaust pipe is fixed to the exhaust end of the cylinder, and the second end extends to connect with the aftertreatment device, which is used to remove pollutants from the exhaust gas.

[0010] The turbocharger is equipped with an intake turbine and an exhaust turbine. The intake turbine is connected to the intake pipe, and the exhaust turbine is connected to the exhaust pipe.

[0011] An EGR system pipeline is provided between the intake pipeline and the exhaust pipeline. One end of the EGR system pipeline is connected to the front of the intake turbine in the intake direction, and the other end is connected to the rear of the exhaust turbine in the exhaust direction. The venturi tube is installed in the EGR system pipeline, so that the exhaust gas flows back to the intake pipeline through the EGR system pipeline and the venturi tube.

[0012] Optionally, the recirculation system further includes a first pressure sensor and a second pressure sensor. The first pressure sensor is disposed in front of the intake turbine in the intake direction and connected to the intake pipeline. The first pressure sensor is used to measure the intake pressure value.

[0013] The second pressure sensor is disposed between the exhaust turbine and the aftertreatment device, and is used to measure the pressure value of the exhaust.

[0014] Optionally, the venturi tube is provided with a third integrated temperature and pressure sensor and a fourth integrated temperature and pressure sensor, which are respectively located at both ends of the venturi tube to measure the temperature and pressure values ​​at both ends of the venturi tube.

[0015] Optionally, the EGR system pipeline is also equipped with an EGR cooler, which is used to cool the recirculated exhaust gas.

[0016] Optionally, the EGR cooler is fixedly connected to the venturi tube in front of it along the exhaust gas flow direction.

[0017] Optionally, an intercooler, a throttle valve, and a natural gas mixer are sequentially arranged along the intake direction on the intake pipe, and the natural gas mixer is connected to the natural gas injection device.

[0018] Optionally, the venturi tube is fixed to the EGR system pipeline by means of threaded connection or bolt connection.

[0019] Optionally, the recirculation system further includes an air filter disposed on the intake pipe and located in front of the turbocharger intake direction.

[0020] The second aspect of this application provides a method for controlling the EGR exhaust gas flow rate of a low-pressure EGR system without an EGR valve, comprising:

[0021] The intake valve closing time is controlled by the depth Miller camshaft;

[0022] The pressure difference between the intake pressure and the exhaust pressure is obtained by using the first pressure sensor and the second pressure sensor;

[0023] Determine whether the differential pressure value is positive; if so, monitor the engine's operating load in real time.

[0024] When the operating load is less than a preset threshold, it is determined whether the EGR exhaust gas overcomes the resistance of the EGR system pipeline. If so, the EGR exhaust gas is returned through the Venturi tube.

[0025] When the operating load is greater than the preset threshold, the EGR exhaust gas is controlled to reflux through the venturi tube according to the preset EGR rate, where the EGR rate represents the ratio of the intake CO2 concentration to the exhaust CO2 concentration.

[0026] Optionally, the EGR rate ranges from 5% to 10%.

[0027] As can be seen from the above technical solutions, this application has the following effects:

[0028] By placing the EGR system piping at both ends of the turbocharger and installing a venturi tube within the EGR system piping, replacing the existing EGR valve with the venturi tube, the EGR system piping is kept in a constantly open state. The EGR exhaust gas is drawn out from behind the turbocharger's exhaust turbine and introduced before the turbocharger's intake turbine. The EGR exhaust gas and air have a longer path to enter the cylinder after mixing, thus reducing the temperature of the EGR exhaust gas returning to the cylinder. At the same time, combined with the deep Miller camshaft controlling the closing time of the intake valve to reduce the temperature of the air-fuel mixture in the cylinder, the thermal load of the engine under high load conditions can be reduced, thereby reducing the risk of knocking problems in the cylinder. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A schematic diagram of a low-pressure EGR system without an EGR valve provided in this application;

[0031] Figure 2 A schematic diagram of an EGR exhaust gas flow control method for a low-pressure EGR system without an EGR valve provided in this application;

[0032] Figure 3 This is a schematic diagram of the engine operating conditions in this application. Detailed Implementation

[0033] This application provides a low-pressure EGR system without an EGR valve and an EGR exhaust gas flow control method to reduce the thermal load of the engine under high load conditions and reduce the risk of knocking problems.

[0034] Please see Figure 1 , Figure 1 A schematic diagram of a low-pressure EGR system without an EGR valve provided in this application, the reflux system comprising:

[0035] The system comprises a turbocharger 1, a venturi tube 2, a cylinder 3, an intake pipe 4, and an exhaust pipe 5. The intake pipe 4 is connected to the intake end of the cylinder 3. The first end of the exhaust pipe 5 is fixed to the exhaust end of the cylinder 3, and the second end extends to connect with the aftertreatment device 6. The turbocharger 1 is equipped with an intake turbine 11 and an exhaust turbine 12. The intake turbine 11 is connected to the intake pipe 4, and the exhaust turbine 12 is connected to the exhaust pipe 5. An EGR system pipe 7 is provided between the intake pipe 4 and the exhaust pipe 5. One end of the EGR system pipe 7 is connected to the front of the intake turbine 11 in the intake direction, and the other end is connected to the rear of the exhaust turbine 12 in the exhaust direction. The venturi tube 2 is installed in the EGR system pipe 7, so that the exhaust gas flows back to the intake pipe 4 through the EGR system pipe 7 and the venturi tube 2.

[0036] The intake pipe 4 is divided into a front intake pipe and a rear intake pipe. The front intake pipe is the pipe between the intake turbine 11 and the air filter 9, and the rear intake pipe is the pipe between the intake turbine 11 and the cylinder 3. In this embodiment, the intake turbine 11 of the turbocharger 1 is connected to both the front intake pipe and the rear intake pipe. Outside air first enters the front intake pipe, and the intake turbine 11 heats and pressurizes the air in the front intake pipe. The pressurized air mixes thoroughly with the fuel as it flows through the rear intake pipe, and then enters the cylinder 3 for combustion. The exhaust gas generated by combustion is discharged along the exhaust pipe 5 to the aftertreatment device 6. After the exhaust gas is treated by the aftertreatment device 6, it is discharged.

[0037] EGR system pipe 7 connects the two ends of turbocharger 1. One end of EGR system pipe 7 is connected to the intake front pipe, and the other end is located between exhaust turbine 12 and aftertreatment device 6, and is connected to exhaust pipe 5.

[0038] A Venturi tube 2 is installed on the EGR system pipe 7. The Venturi tube 2 is in a normally open state. That is, during engine operation, when the exhaust pressure is greater than the intake pressure and the EGR exhaust gas overcomes the resistance of the EGR system pipe 7, the EGR exhaust gas can flow back from the exhaust pipe 5 to the intake front pipe. Furthermore, as the engine load increases, the exhaust flow rate increases, and the exhaust pressure also increases accordingly. Therefore, during engine operation, the exhaust gas recirculation flow rate will increase with the increase of engine power. For example, when the engine power is 100, the exhaust resistance is 50, and the exhaust gas recirculation flow rate is 20. When the power rises to 300, the exhaust resistance increases to 150, and the exhaust gas recirculation flow rate increases to 50.

[0039] In this embodiment, EGR exhaust gas is introduced into the EGR system pipeline 7 after the exhaust turbine 12. After the return exhaust gas passes through the venturi tube 2, the EGR exhaust gas is introduced into the intake pipeline 4 before the intake turbine 11. The return exhaust gas and the fresh air in the intake front pipeline are mixed to form a mixture. After the mixture passes through the intake turbine 11, it flows into the cylinder through the intake rear pipeline. Therefore, this application firstly increases the path of the EGR exhaust gas from the start of its recirculation to its entry into cylinder 3, and cools the mixture through the intercooler 42 located at the rear of the intake, so that the mixture can be effectively cooled before entering cylinder 3; at the same time, combined with the deep Miller camshaft controlling the intake valve closing time, it further reduces the temperature of the mixture in the cylinder, thus reducing the thermal load of the engine under high load conditions and reducing the risk of knocking in cylinder 3; secondly, the reduction in cylinder temperature and pressure at the end of compression increases the engine's knock limit, which in turn allows for a higher geometric compression ratio piston, resulting in a larger expansion ratio and improved engine economy.

[0040] Optionally, the low-pressure EGR system without an EGR valve provided in this application further includes a first pressure sensor 41 and a second pressure sensor 51. The first pressure sensor 41 is disposed in front of the intake turbine 11 in the intake direction and connected to the intake pipe 4. The first pressure sensor 41 is used to measure the intake pressure value. The second pressure sensor 51 is disposed between the exhaust turbine 12 and the aftertreatment device 6. The second pressure sensor 51 is used to measure the exhaust pressure value between the exhaust turbine 12 and the aftertreatment device 6.

[0041] In this embodiment, by measuring the pressure values ​​of the intake air and the exhaust air, the pressure difference between the intake front-end pipe and the exhaust pipe 5 can be calculated. This pressure difference can be used to determine whether there is backflow of EGR exhaust gas and to achieve real-time monitoring.

[0042] Optionally, a third integrated temperature and pressure sensor 71 and a fourth integrated temperature and pressure sensor 72 are installed on the Venturi tube 2. These sensors are respectively located at both ends of the Venturi tube 2 to measure the pressure and temperature values ​​at both ends. The flow rate of the EGR exhaust gas flowing through the Venturi tube 2 can be calculated using these measurement results. In this embodiment, the temperature and pressure values ​​at both ends of the Venturi tube 2 can be measured, and real-time monitoring of the EGR flow rate can be achieved through the temperature and pressure difference changes before and after the Venturi tube.

[0043] Optionally, an EGR cooler 73 is also provided on the EGR system pipeline 7. The EGR cooler 73 is used to cool the recirculated exhaust gas. In this embodiment, the EGR cooler 73 is used to control the temperature of the recirculated exhaust gas in the EGR system pipeline 7 and reduce the pressure drop in the EGR system pipeline 7.

[0044] Optionally, the EGR cooler 73 is fixedly connected to the venturi tube 2 in front of the exhaust gas flow direction.

[0045] Optionally, an intercooler 42, a throttle valve 43, and a natural gas mixer 44 are sequentially arranged along the intake direction on the intake pipe 7. The natural gas mixer 44 is connected to the natural gas injection device 8. In this embodiment, the natural gas mixer 44 can be used not only for mixing natural gas and air, but also for mixing fuel and air. In this case, the fuel injection device is connected to the natural gas mixer 44.

[0046] Optionally, the Venturi tube 2 is fixed to the EGR system piping 7 by means of threaded connection or bolt connection.

[0047] Optionally, the engine exhaust gas recirculation system provided in this application further includes an air filter 9, which is disposed on the intake pipe 4 and located in front of the turbocharger 1 in the intake direction. Specifically, in this embodiment, the EGR system pipe 7 is connected between the turbocharger 1 and the air filter 9, and the first pressure sensor 41 is disposed in front of the air filter 9 in the intake direction.

[0048] Please continue reading. Figure 2 , Figure 2 This is a schematic diagram of an EGR exhaust gas flow control method for a low-pressure EGR system without an EGR valve, as provided in this application. It should be noted that this EGR exhaust gas flow control method for a low-pressure EGR system without an EGR valve can be applied to a terminal, a system, or a server. For ease of explanation, this application uses a system as the implementing entity for illustration. The EGR exhaust gas flow control method includes:

[0049] 101. The system controls the closing time of the intake valve through the depth Miller camshaft.

[0050] The deep Miller camshaft controls the timing of intake valve closing, reducing the temperature and pressure of the air-fuel mixture at the end of the compression stroke, thereby suppressing knocking and improving the engine's knock limit.

[0051] 102. The system obtains the pressure difference between the intake pressure and the exhaust pressure through the first pressure sensor and the second pressure sensor.

[0052] The turbocharger has a first pressure sensor at the intake end and a second pressure sensor at the exhaust end. The first pressure sensor measures the intake pressure at the intake end, and the second pressure sensor measures the exhaust pressure at the exhaust end. The pressure difference between the intake and exhaust ends can be calculated from these two pressure values. It should be noted that the second pressure sensor is located between the exhaust turbine and the aftertreatment system. Therefore, the pressure value measured by the second pressure sensor is the exhaust pressure between the exhaust turbine and the aftertreatment system, and the pressure difference is calculated by subtracting the intake pressure from the exhaust pressure. For example, if the measured intake pressure is 100 kPa and the exhaust pressure between the exhaust turbine and the aftertreatment system is 115 kPa, the pressure difference is 15 kPa.

[0053] 103. The system determines whether the differential pressure value is positive. If so, it monitors the engine's operating load in real time.

[0054] After the system measures the differential pressure value, it determines whether the differential pressure value is positive. A positive value is a positive number, which is the value obtained by subtracting the pressure value at the intake end from the pressure value at the exhaust end. In practice, since the venturi tube in this application is in a normally open state, and the exhaust flow rate and exhaust pressure increase when the engine operating load increases, it will lead to an increase in EGR exhaust gas recirculation. Therefore, when the differential pressure value is positive, the system monitors the engine operating load in real time.

[0055] Additionally, when the difference is negative, it indicates that the intake pressure is greater than or equal to the exhaust pressure. Due to the resistance in the EGR system pipeline, the exhaust gas generated by the cylinder passes directly through the aftertreatment device and is transported to the outside without recirculation.

[0056] 104. When the operating load is less than the preset threshold, the system determines whether the EGR exhaust gas can overcome the resistance of the EGR system pipeline. If so, the EGR exhaust gas is returned through the Venturi tube.

[0057] By defining and setting a preset load threshold by staff, when the real-time detected engine load is less than the preset threshold, it indicates that the engine is operating under low load conditions. At this time, the system further determines whether the EGR exhaust gas has overcome the resistance of the EGR system pipeline. If it has, a small amount of EGR exhaust gas is introduced into the intake pipeline through the normally open Venturi tube; if it has not, there is no EGR exhaust gas backflow.

[0058] It should be noted that, due to operation under low load conditions, the engine intake and exhaust airflows are both small. Therefore, under these conditions, there is only a small amount of EGR exhaust gas recirculation, or no EGR exhaust gas recirculation at all. Details are as follows... Figure 3 As shown, in Figure 3 In the diagram, the x-axis represents engine speed, the y-axis represents torque, and the area indicated by arrow a represents low-load operating conditions. When the engine operates in this area, if the EGR exhaust gas overcomes the resistance of the EGR system piping, only a small amount of EGR exhaust gas will flow back; if the EGR exhaust gas does not overcome the resistance of the EGR system piping, there will be no EGR exhaust gas flow back. The area indicated by arrow b represents high-load operating conditions.

[0059] 105. When the operating load exceeds the preset threshold, the system controls the EGR exhaust gas to reflux through the venturi tube according to the preset EGR rate. The EGR rate represents the ratio of the intake CO2 concentration to the exhaust CO2 concentration.

[0060] Please continue reading. Figure 3 According to the preset threshold of load in step 104, when the real-time detected engine operating load is greater than the preset threshold, it means that the engine is operating under heavy load conditions. At this time, the engine intake volume is large, the exhaust flow is increased, and the pressure difference between the exhaust pressure and the intake pressure is greater. The system controls the EGR exhaust gas to recirculate through the Venturi tube according to the preset EGR rate. The EGR rate represents the ratio of the intake CO2 concentration to the exhaust CO2 concentration. That is, when the engine is operating in the area indicated by arrow b, the EGR rate is introduced to control the EGR exhaust gas to recirculate.

[0061] Optionally, in one feasible approach, the EGR rate ranges from 5% to 10%.

[0062] In this embodiment, by using the deep Miller camshaft operation mode in conjunction with the intake valve closing time, the in-cylinder temperature and pressure at the end of the compression stroke are reduced, thereby suppressing knocking and improving the engine's knock limit. This allows for the use of pistons with higher geometric compression ratios, resulting in a larger engine expansion ratio and improved engine economy under all operating conditions. In addition, introducing EGR rate under heavy load conditions can further reduce in-cylinder temperature and in-cylinder thermal load.

[0063] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0064] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0065] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0066] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0067] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A low-pressure EGR system without an EGR valve, characterized in that, include: Supercharger, venturi tube, cylinder, intake manifold and exhaust manifold; The intake pipe is connected to the intake end of the cylinder; The first end of the exhaust pipe is fixed to the exhaust end of the cylinder, and the second end extends to connect with the aftertreatment device, which is used to remove pollutants from the exhaust gas. The turbocharger is equipped with an intake turbine and an exhaust turbine. The intake turbine is connected to the intake pipe, and the exhaust turbine is connected to the exhaust pipe. An EGR system pipeline is provided between the intake pipeline and the exhaust pipeline. One end of the EGR system pipeline is connected to the front of the intake turbine in the intake direction, and the other end is connected to the rear of the exhaust turbine in the exhaust direction. The venturi tube is installed in the EGR system pipeline, so that the exhaust gas flows back to the intake pipeline through the EGR system pipeline and the venturi tube. The recirculation system also includes a first pressure sensor and a second pressure sensor. The first pressure sensor is located in front of the intake turbine in the intake direction and is connected to the intake pipeline. The first pressure sensor is used to measure the intake pressure value. The second pressure sensor is disposed between the exhaust turbine and the aftertreatment device, and is used to measure the pressure value of the exhaust.

2. The low-pressure EGR system according to claim 1, characterized in that, The Venturi tube is equipped with a third integrated temperature and pressure sensor and a fourth integrated temperature and pressure sensor, which are respectively located at both ends of the Venturi tube to measure the temperature and pressure values ​​at both ends of the Venturi tube.

3. The low-pressure EGR system according to claim 1, characterized in that, The EGR system pipeline is also equipped with an EGR cooler, which is used to cool the returning exhaust gas.

4. The low-pressure EGR system according to claim 3, characterized in that, The EGR cooler is fixedly connected to the venturi tube in front of it along the direction of exhaust gas flow.

5. The low-pressure EGR system according to claim 1, characterized in that, The intake pipe is provided with an intercooler, a throttle valve and a natural gas mixer in sequence along the intake direction, and the natural gas mixer is connected to the natural gas injection device.

6. The low-voltage EGR system according to claim 1, characterized in that, The venturi tube is fixed to the EGR system pipeline by means of threaded connection or bolt connection.

7. The low-voltage EGR system according to claim 1, characterized in that, The recirculation system also includes an air filter, which is disposed on the intake pipe and located in front of the turbocharger in the intake direction.

8. A method for controlling the EGR exhaust gas flow rate of a low-pressure EGR system without an EGR valve, characterized in that, include: The intake valve closing time is controlled by the depth Miller camshaft; The pressure difference between the intake pressure and the exhaust pressure is obtained by using the first pressure sensor and the second pressure sensor; Determine whether the differential pressure value is positive; if so, monitor the engine's operating load in real time. When the operating load is less than a preset threshold, it is determined whether the EGR exhaust gas overcomes the resistance of the EGR system pipeline. If so, the EGR exhaust gas is returned through the Venturi tube. When the operating load exceeds the preset threshold, the EGR exhaust gas is controlled to reflux through the venturi tube according to the preset EGR rate. The EGR rate represents the ratio of the intake CO2 concentration to the exhaust CO2 concentration; the range of the EGR rate is 5%-10%.

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