A compact EGR system and control method

Abstract

The present invention discloses a compact EGR system and control method. It includes an engine, wherein the engine intake pipe is connected to an intercooler and a compressor in sequence, the engine exhaust manifold is connected to a turbine, the turbine outlet is connected to a post-processing DOC, DPF, and SCR, the rear ends of the DOC and DPF are connected to one end of a low-pressure EGR pipeline, a low-pressure EGR pump is arranged on the low-pressure EGR pipeline, the low-pressure EGR pump is driven by a low-pressure EGR motor, and the other end of the low-pressure EGR pipeline is connected to an EGR cooler inlet; the rear end of the engine exhaust manifold is connected to one end of two high-pressure EGR pipelines, and the other ends of the two high-pressure EGR pipelines are connected to the EGR cooler inlet; the EGR cooler outlet is connected to the compressor inlet. The present invention realizes global EGR rate control under different loads and different speeds, achieves a high EGR rate, and the transient responsiveness of the EGR rate is higher.

Description

Technical Field

[0001] The invention belongs to the technical field of engine exhaust gas recirculation system, and in particular relates to a compact EGR system and a control method. Background Art

[0002] Exhaust gas recirculation (EGR) technology introduces part of the exhaust gas of the internal combustion engine into the intake air to participate in the combustion process again. X One of the main technical solutions used for emissions. It is mainly divided into high-pressure EGR technology and low-pressure EGR technology. High-pressure EGR technology mainly takes exhaust gas from the front of the engine turbine and introduces it into the intake system of the engine intake manifold after passing through the EGR valve, one-way valve, and EGR cooler. Low-pressure EGR technology mainly takes exhaust gas from the post-treatment and introduces it into the intake system before the engine compressor after passing through the EGR valve, one-way valve, and EGR cooler.

[0003] like Figure 1 , Figure 2 As shown in the figure, according to the distribution of the next generation EGR rate according to the predicted regulations and the comparison of the predicted graph, the maximum EGR of existing diesel engines does not exceed 22%, and the EGR rate under medium and high loads is generally not high. According to the prediction of the next generation EGR rate distribution, the maximum EGR rate will reach nearly 30%, and the EGR rate under high-speed conditions is generally above 26%.

[0004] Since the EGR rate that can be achieved by diesel engines is currently limited by the driving pressure difference of the EGR system, the EGR valve can meet the requirements of the National VI regulations to achieve the existing EGR rate. However, in the face of more stringent emission regulations in the future, the EGR valve cannot meet the needs of future diesel engines in areas where the driving pressure difference of the diesel engine itself is low.

[0005] At the same time, in order to achieve a higher EGR driving pressure difference, many existing engine high-pressure EGR systems use dual-channel EGR pipelines to introduce the exhaust gas into the engine's intake system after passing through the EGR valve, one-way valve, and EGR cooler. The function of the one-way valve can effectively reduce the backflow of exhaust gas and better ensure the formation of EGR gas, but the dual-channel system has one more EGR valve, one one-way valve, and one EGR cooler than the single-channel system, and the cost and failure rate will increase accordingly, and the difficulty of vehicle layout will also increase. Similarly, in vehicles with high and low pressure EGR systems, in addition to the high and low pressure EGR systems having one more EGR valve, one-way valve, and EGR cooler than the above-mentioned high-pressure EGR system, the cost, failure rate, and layout difficulty will also be higher. Summary of the invention

[0006] The purpose of the present invention is to solve the deficiencies of the above-mentioned background technology and to provide a compact EGR system and control method.

[0007] The technical solution adopted by the present invention is: a compact EGR system, including an engine, wherein the engine intake pipe is connected to an intercooler and a compressor in sequence, the engine exhaust manifold is connected to a turbine, the turbine outlet is connected to post-processing DOC, DPF, and SCR, the rear ends of the DOC and DPF are connected to one end of a low-pressure EGR pipeline, a low-pressure EGR pump is arranged on the low-pressure EGR pipeline, the low-pressure EGR pump is driven by a low-pressure EGR motor, and the other end of the low-pressure EGR pipeline is connected to an EGR cooler inlet; the rear end of the engine exhaust manifold is connected to one end of two high-pressure EGR pipelines, and the other ends of the two high-pressure EGR pipelines are connected to the EGR cooler inlet; the EGR cooler outlet is connected to the compressor inlet.

[0008] The two high-pressure EGR pipelines are respectively provided with a first high-pressure EGR pump and a second high-pressure EGR pump, and the first high-pressure EGR pump and the second high-pressure EGR pump are respectively driven by a first high-pressure EGR motor and a second high-pressure EGR motor.

[0009] A first solenoid valve and a second solenoid valve are respectively arranged on the two high-pressure EGR pipelines, and the two high-pressure EGR pipelines at the rear ends of the first solenoid valve and the second solenoid valve are combined into one, and a third high-pressure EGR pump is arranged on the high-pressure EGR pipeline combined into one, and the third high-pressure EGR pump is driven by a third high-pressure EGR motor.

[0010] It also includes an ECU, which acquires in real time an accelerator pedal position signal, an engine speed signal, a low-pressure EGR motor speed signal, a first high-pressure EGR motor speed signal, and a second high-pressure EGR motor speed signal respectively output by an accelerator pedal position sensor, an engine speed sensor, an intake air flow sensor, a low-pressure EGR motor speed sensor, a first high-pressure EGR motor speed sensor, and a second high-pressure EGR motor speed sensor.

[0011] The ECU determines the engine operating condition and the EGR rate of the engine under MAP1 according to the accelerator pedal position signal and the engine speed signal, and controls the speed of the low-pressure EGR motor, the first high-pressure EGR motor and the second high-pressure EGR motor.

[0012] When the engine operating condition corresponds to an engine EGR rate of 0% to 23%, the ECU controls the low-pressure EGR motor to start and run at the speed corresponding to the corresponding calibrated MAP2 data, and the speeds of the first high-pressure EGR motor and the second high-pressure EGR motor are 0;

[0013] When the engine operating condition corresponds to an engine EGR rate of 23% to 25%, the ECU controls the low-pressure EGR motor speed to 0, and the first high-pressure EGR motor and the second high-pressure EGR motor are turned on and run at the speed corresponding to the corresponding calibrated MAP2 data;

[0014] When the engine operating condition corresponds to an engine EGR rate of 26% to 30%, the ECU controls the low-pressure EGR motor speed to 0, the first high-pressure EGR motor and the second high-pressure EGR motor are turned on, and run at the speed corresponding to the corresponding calibrated MAP2 data.

[0015] The ECU obtains in real time the accelerator pedal position signal, engine speed signal, low-pressure EGR motor speed signal, third high-pressure EGR motor speed signal, first solenoid valve switch signal, and second solenoid valve switch signal respectively output by the accelerator pedal position sensor, engine speed sensor, intake air flow sensor, low-pressure EGR motor speed sensor, third high-pressure EGR motor speed sensor, first solenoid valve switch sensor, and second solenoid valve switch sensor.

[0016] The ECU determines the engine operating condition and the EGR rate of the engine under MAP1 according to the accelerator pedal position signal and the engine speed signal, and controls the speed of the low-pressure EGR motor and the third high-pressure EGR motor, and the switches of the first solenoid valve and the second solenoid valve.

[0017] When the engine operating condition corresponds to an engine EGR rate of 0% to 23%, the ECU controls the low-pressure EGR motor to turn on and run at the speed corresponding to the corresponding calibrated MAP2 data, the first solenoid valve and the second solenoid valve are closed, and the speed of the third high-pressure EGR motor is 0;

[0018] When the engine operating condition corresponds to an engine EGR rate of 23% to 25%, the ECU controls the low-pressure EGR motor speed to 0, the first solenoid valve and the second solenoid valve are closed, and the third high-pressure EGR motor is turned on and runs at the speed corresponding to the corresponding calibrated MAP2 data;

[0019] When the engine operating condition corresponds to an engine EGR rate of 26% to 30%, the ECU controls the low-pressure EGR motor speed to 0, the first solenoid valve is opened, the second solenoid valve is opened, the third high-pressure EGR motor is opened, and runs at the speed corresponding to the corresponding calibrated MAP2 data.

[0020] A control method for a compact EGR system includes: air is supercharged and cooled by a compressor and an intercooler, and then enters the engine through an engine intake pipe to participate in combustion compression and work. Then, the exhaust gas passes through the engine exhaust manifold and enters the turbine. A part of the exhaust gas expands and does work. The exhaust gas after the turbine is discharged after being post-processed by DOC, DPF, and SCR. After the DOC and DPF, one low-pressure exhaust gas is taken for low-pressure exhaust gas recirculation and enters the low-pressure EGR pipeline, and then passes through the EGR cooler to re-enter the compressor for supercharging; after the exhaust manifold, two exhaust gases are taken for high-pressure exhaust gas circulation and enter the two high-pressure EGR pipelines. The exhaust gases of the two high-pressure EGR pipelines enter the EGR cooler shared with the low-pressure EGR pipeline and are collected into one channel for cooling, and then merge with the intake air after the intercooler to enter the engine intake pipe to participate in cylinder combustion; or the two high-pressure EGR pipelines are collected into one channel and then enter the EGR cooler shared with the low-pressure EGR pipeline, and after cooling, merge with the intake air after the intercooler and enter the engine intake pipe to participate in cylinder combustion.

[0021] The present invention has a high- and low-pressure EGR system, wherein the high-pressure EGR system is a dual-channel high-pressure EGR system, and the low-pressure EGR system is a single-channel low-pressure EGR system. The combination of all EGR valves and one-way valves is replaced by an electric EGR pump. Not only the motor speed integrated in the EGR pump itself is controlled by the ECU, thereby controlling the power of the EGR pump and realizing global EGR rate control under different loads and speeds, but also a high EGR rate that cannot be achieved by an ordinary EGR valve can be achieved, and the transient responsiveness of the EGR rate brought by the motor control speed is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the current distribution of diesel engine EGR rate;

[0023] Figure 2 This is a schematic diagram of the predicted EGR rate distribution under the next generation of regulations;

[0024] Figure 3 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0026] Figure 5 This is a schematic diagram of specific fuel consumption and EGR rate corresponding to different EGR rate targets for single and double channels under 1200r / min working conditions;

[0027] Figure 6 The schematic diagram of specific fuel consumption and EGR rate corresponding to different EGR rate targets for single and double channels under 1000r / min working condition;

[0028] Figure 7 It is a schematic diagram of the principle of the present invention;

[0029] Figure 8 Schematic diagram of the comparison between single-channel and dual-channel pulse pressure waves. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but they do not constitute a limitation on the present invention.

[0031] like Figure 3 , Figure 4 As shown, a compact EGR system of the present invention comprises an engine, wherein the engine intake pipe is connected to an intercooler and a compressor in sequence, the engine exhaust manifold is connected to a turbine, the turbine outlet is connected to post-processing DOC, DPF, and SCR, the rear ends of the DOC and DPF are connected to one end of a low-pressure EGR pipeline, a low-pressure EGR pump is arranged on the low-pressure EGR pipeline, the low-pressure EGR pump is driven by a low-pressure EGR motor M1, and the other end of the low-pressure EGR pipeline is connected to an EGR cooler inlet; the rear end of the engine exhaust manifold is connected to one end of two high-pressure EGR pipelines, and the other ends of the two high-pressure EGR pipelines are connected to the EGR cooler inlet; the EGR cooler outlet is connected to the compressor inlet.

[0032] The two high-pressure EGR pipelines are respectively provided with a first high-pressure EGR pump and a second high-pressure EGR pump, and the first high-pressure EGR pump and the second high-pressure EGR pump are respectively driven by a first high-pressure EGR motor M2 and a second high-pressure EGR motor M3.

[0033] A first solenoid valve P1 and a second solenoid valve P2 are respectively arranged on the two high-pressure EGR pipelines. The two high-pressure EGR pipelines at the rear end of the first solenoid valve P1 and the second solenoid valve P2 are combined into one high-pressure EGR pipeline. A third high-pressure EGR pump is arranged on the combined high-pressure EGR pipelines. The third high-pressure EGR pump is driven by a third high-pressure EGR motor M4.

[0034] It also includes an ECU, which acquires in real time an accelerator pedal position signal, an engine speed signal, a low-pressure EGR motor speed signal, a first high-pressure EGR motor speed signal, and a second high-pressure EGR motor speed signal respectively output by an accelerator pedal position sensor, an engine speed sensor, an intake air flow sensor, a low-pressure EGR motor speed sensor, a first high-pressure EGR motor speed sensor, and a second high-pressure EGR motor speed sensor.

[0035] The ECU determines the engine operating condition and the EGR rate of the engine under MAP1 according to the accelerator pedal position signal and the engine speed signal, and controls the speed of the low-pressure EGR motor, the first high-pressure EGR motor and the second high-pressure EGR motor.

[0036] The ECU obtains in real time the accelerator pedal position signal, engine speed signal, low-pressure EGR motor speed signal, third high-pressure EGR motor speed signal, first solenoid valve switch signal, and second solenoid valve switch signal respectively output by the accelerator pedal position sensor, engine speed sensor, intake air flow sensor, low-pressure EGR motor speed sensor, third high-pressure EGR motor speed sensor, first solenoid valve switch sensor, and second solenoid valve switch sensor.

[0037] The ECU determines the engine operating condition and the EGR rate of the engine under MAP1 according to the accelerator pedal position signal and the engine speed signal, and controls the speed of the low-pressure EGR motor and the third high-pressure EGR motor, and the switches of the first solenoid valve and the second solenoid valve.

[0038] Embodiment 1:

[0039] like Figure 3 As shown, air is supercharged and cooled by the compressor and intercooler, then enters the engine through the engine intake pipe to participate in combustion, compression and work, and then the exhaust gas passes through the engine exhaust manifold and enters the turbine. A part of the exhaust gas expands and does work, and the exhaust gas after the turbine is discharged after post-processing DOC+DPF+SCR. At the same time, a low-pressure exhaust gas is taken after DOC+DPF for low-pressure exhaust gas recirculation and low-pressure EGR. A low-pressure EGR pump is arranged on the low-pressure EGR pipeline, and the low-pressure EGR pump is driven by its own integrated low-pressure EGR motor M1. The speed of the low-pressure EGR motor M1 is controlled by the ECU. After taking air, it passes through the EGR cooler and re-enters the compressor for supercharging. The rest of the exhaust gas after the turbine is discharged, and another A part of the exhaust gas is taken from two exhaust gas paths on the exhaust manifold for high-pressure exhaust gas recirculation (EGR). A first high-pressure EGR pump and a second high-pressure EGR pump are respectively arranged on the two high-pressure EGR pipelines. The first high-pressure EGR pump and the second high-pressure EGR pump are driven by the first high-pressure EGR motor M2 and the second high-pressure EGR motor M3 integrated therein. The speed of the first high-pressure EGR motor M2 and the second high-pressure EGR motor M3 are controlled by the ECU. After taking air from the two high-pressure EGR paths, they also enter the same EGR cooler. In the EGR cooler, the two EGR pipelines are gathered into one cooled high-pressure EGR gas, which enters the engine intake pipe after merging with the gas after passing through the intercooler to participate in the combustion in the cylinder.

[0040] The ECU obtains in real time the accelerator pedal position signal, engine speed signal, low-pressure EGR motor M1 speed signal, first high-pressure EGR motor M2 speed signal, and second high-pressure EGR motor M3 speed signal output by the accelerator pedal position sensor, engine speed sensor, intake air flow sensor, low-pressure EGR motor M1 speed sensor, first high-pressure EGR motor M2 speed sensor, and second high-pressure EGR motor M3 speed sensor respectively.

[0041] The ECU determines the engine operating condition and the EGR rate of the engine under MAP1 according to the accelerator pedal position signal and the engine speed signal, and controls the speed of the low-pressure EGR motor M1, the first high-pressure EGR motor M2 and the second high-pressure EGR motor M3.

[0042] When the engine operating condition corresponds to an engine EGR rate of 0% to 23%, the ECU controls the low-pressure EGR motor M1 to start and run at the speed corresponding to the corresponding calibration MAP2 data, and the speeds of the first high-pressure EGR motor M2 and the second high-pressure EGR motor M3 are 0;

[0043] When the engine operating condition corresponds to an engine EGR rate of 23% to 25%, the ECU controls the speed of the low-pressure EGR motor M1 to be 0, and the first high-pressure EGR motor M2 and the second high-pressure EGR motor M3 are turned on and run at the speed corresponding to the corresponding calibrated MAP2 data;

[0044] When the engine operating condition corresponds to an engine EGR rate of 26% to 30%, the ECU controls the speed of the low-pressure EGR motor M1 to 0, and the first high-pressure EGR motor M2 and the second high-pressure EGR motor M3 are turned on and run at the speed corresponding to the corresponding calibrated MAP2 data.

[0045] Embodiment 2:

[0046] like Figure 4 As shown, air is supercharged and cooled by the compressor and intercooler, and then enters the engine through the engine intake pipe to participate in combustion, compression, and work. Then the exhaust gas passes through the engine exhaust manifold and enters the turbine. Part of the exhaust gas expands and does work. The exhaust gas after the turbine is discharged after post-processing DOC+DPF+SCR. At the same time, a low-pressure exhaust gas is taken after DOC+DPF for low-pressure exhaust gas recirculation and low-pressure EGR. A low-pressure EGR pump is set on the low-pressure EGR pipeline. The low-pressure EGR pump is driven by its own integrated low-pressure EGR motor M1. The speed of the low-pressure EGR motor M1 is controlled by the ECU. After taking the air, it passes through the EGR cooler and re-enters the compressor. The turbocharger is used to supercharge the exhaust gas, and the remaining exhaust gas after the turbine is discharged. The other part of the exhaust gas is taken in two exhaust gas routes on the exhaust manifold for high-pressure exhaust gas recirculation (EGR). The first solenoid valve P1 and the second solenoid valve P2 are arranged on the two high-pressure EGR pipelines respectively. The pipelines after the first solenoid valve P1 and the second solenoid valve P2 are combined into one route, and then pass through the third high-pressure EGR pump and are driven by the third high-pressure EGR motor M4 integrated therein. The speed of the third high-pressure EGR motor M4 is controlled by the ECU, and then enter the EGR cooler shared with the low-pressure EGR pipeline, and after cooling, it merges with the intake air after the intercooler and enters the engine intake pipe to participate in the combustion in the cylinder.

[0047] The ECU obtains in real time the accelerator pedal position signal, the engine speed signal, the low-pressure EGR motor M1 speed signal, the third high-pressure EGR motor M4 speed signal, the first solenoid valve P1 switch signal, and the second solenoid valve P2 switch signal outputted by the accelerator pedal position sensor, the engine speed sensor, the intake air flow sensor, the low-pressure EGR motor M1 speed sensor, the third high-pressure EGR motor M4 speed sensor, the first solenoid valve P1 switch signal, and the second solenoid valve P2 switch signal respectively;

[0048] The ECU determines the engine operating condition and the EGR rate of the engine under MAP1 according to the accelerator pedal position signal and the engine speed signal, and controls the speed of the low-pressure EGR motor M1 and the third high-pressure EGR motor M4, and the switches of the first solenoid valve P1 and the second solenoid valve P2.

[0049] When the engine operating condition corresponds to an engine EGR rate of 0% to 23%, the ECU controls the low-pressure EGR motor M1 to turn on and run at the speed corresponding to the corresponding calibration MAP2 data, the first solenoid valve P1 and the second solenoid valve P2 are closed, and the speed of the third high-pressure EGR motor M4 is 0;

[0050] When the engine operating condition corresponds to an engine EGR rate of 23% to 25%, the ECU controls the speed of the low-pressure EGR motor M1 to be 0, the first solenoid valve P1 and the second solenoid valve P2 are closed, and the third high-pressure EGR motor M4 is turned on and runs at the speed corresponding to the corresponding calibration MAP2 data;

[0051] When the engine operating condition corresponds to an engine EGR rate of 26% to 30%, the ECU controls the speed of the low-pressure EGR motor M1 to 0, the first solenoid valve P1 is opened, the second solenoid valve P2 is opened, and the third high-pressure EGR motor M4 is opened, and runs at the speed corresponding to the corresponding calibrated MAP2 data.

[0052] like Figure 5 and Figure 6 The figure shows the effect comparison of single-channel and dual-channel under different speeds of 1200r / min and 1000r / min when the low-pressure EGR pump is closed. The horizontal axis is the ratio of the EGR pump output power to the maximum power, and the vertical axis is the specific fuel consumption and EGR rate. It shows that the dual-channel EGR can achieve a higher EGR rate than the single-channel EGR. When the EGR valve opening is below 50%, the BSFC (specific fuel consumption) is better overall. When it is above 50%, the BSFC (specific fuel consumption) is worse because the engine intake volume under the conditions of 1000r / min and 1200 / min is not too much surplus. As the EGR rate increases, the insufficient intake volume will lead to worse combustion and poorer supercharger operating efficiency. At this time, the EGR pump speed can be controlled to control the EGR to the best working condition for specific fuel consumption.

[0053] like Figure 7 As shown, the high-pressure EGR pump pipeline ① of the present invention takes EGR gas from the 1st, 2nd and 3rd cylinders of the engine and the high-pressure EGR pump pipeline ② takes EGR gas from the 4th, 5th and 6th cylinders of the engine. Compared with only taking one high-pressure EGR pipeline ① or ②, the pulse energy of the pipeline gas can be better utilized. Figure 8 As shown, the interference between the air intake pressure waves of the single-pass EGR pipelines ① and ② makes the total EGR pressure wave peak value smaller than that of the dual-channel, resulting in a relatively small single-pass EGR rate. Therefore, the dual-channel air intake high-pressure EGR pipeline of the present invention itself can obtain a higher EGR rate than the single-pass EGR pipeline. Also, because the dual-pass EGR pipeline + low-pressure EGR pipeline corresponds to three EGR pipelines that need to be cooled, the present invention adopts an integrated EGR cooler to integrate the cooling of three pipelines, namely, two high-pressure EGR pipelines and one low-pressure EGR pipeline, into one cooler. This is not only more conducive to the utilization of the EGR pipeline pulse energy and the realization of a higher EGR rate, but also more compact than the structure of multiple EGR coolers, and reduces the cost of the EGR system and the cooling system.

[0054] Therefore, the implementation of this patent can achieve the improvement of the global EGR rate by replacing the existing EGR valve or EGR valve + one-way valve with an electrically driven EGR pump. At the same time, an integrated EGR cooler is adopted, and multiple channels are set inside the cooler. The multi-channel EGR pipelines are merged into the same EGR cooler for cooling and then introduced into the corresponding intake system. According to the actual diesel engine oil operating conditions, the ECU controls the speed of the EGR pump motor to adjust different EGR rates, achieve the optimal global EGR rate under different conditions, and ultimately achieve emission targets and the best engine economy performance.

[0055] Under the working condition that the engine EGR rate demand is large, Example 1: ECU controls to open the high-pressure EGR pump at the same time, Example 2: ECU controls to open the solenoid valves P1 and P2 and the high-pressure EGR pump at the same time, which can not only meet the high EGR rate demand of the engine, but also can accurately control the speed of the electric EGR pump through optimization calibration, thereby accurately controlling the EGR rate at the high-pressure end and the EGR rate at the low-pressure end, and realizing the improvement of the vehicle's specific fuel consumption; it can better solve the problem of slow transient response of the engine under all working conditions; it can not only enable the whole vehicle to achieve higher and stricter future emission regulations, but also make the whole vehicle more economical; the multi-channel EGR system can better utilize the pulse pressure wave of the pipeline gas, and through a single EGR cooler with multi-channel input, it can not only maximize the utilization of pulse energy, but also has a more compact structure than multiple EGR coolers, and has lower cost and failure rate.

[0056] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A compact EGR system, comprising an engine, characterized in that: The engine intake pipe is connected to the intercooler and the compressor in sequence, the engine exhaust manifold is connected to the turbine, the turbine outlet is connected to the post-processing DOC, DPF, and SCR, the rear ends of the DOC and DPF are connected to one end of the low-pressure EGR pipeline, a low-pressure EGR pump is arranged on the low-pressure EGR pipeline, the low-pressure EGR pump is driven by a low-pressure EGR motor, and the other end of the low-pressure EGR pipeline is connected to the EGR cooler inlet; the rear end of the engine exhaust manifold is connected to one end of the two-way high-pressure EGR pipeline, and the other end of the two-way high-pressure EGR pipeline is connected to the EGR cooler inlet; the EGR cooler outlet is connected to the compressor inlet; A first high-pressure EGR pump and a second high-pressure EGR pump are respectively arranged on the two high-pressure EGR pipelines, and the first high-pressure EGR pump and the second high-pressure EGR pump are respectively driven by a first high-pressure EGR motor and a second high-pressure EGR motor; The ECU is further comprised of an ECU that acquires in real time an accelerator pedal position signal, an engine speed signal, a low-pressure EGR motor speed signal, a first high-pressure EGR motor speed signal, and a second high-pressure EGR motor speed signal outputted by an accelerator pedal position sensor, an engine speed sensor, an intake air flow sensor, a low-pressure EGR motor speed sensor, a first high-pressure EGR motor speed sensor, and a second high-pressure EGR motor speed sensor, respectively; The ECU determines the engine operating condition and the EGR rate of the engine corresponding to MAP1 according to the accelerator pedal position signal and the engine speed signal, and controls the speed of the low-pressure EGR motor, the first high-pressure EGR motor and the second high-pressure EGR motor; When the engine operating condition corresponds to an engine EGR rate of 0% to 23%, the ECU controls the low-pressure EGR motor to start and run at the speed corresponding to the corresponding calibrated MAP2 data, and the speeds of the first high-pressure EGR motor and the second high-pressure EGR motor are 0; When the engine operating condition corresponds to an engine EGR rate of 23% to 25%, the ECU controls the low-pressure EGR motor speed to 0, the first high-pressure EGR motor and the second high-pressure EGR motor are turned on, and run at the speed corresponding to the corresponding calibrated MAP2 data; When the engine operating condition corresponds to an engine EGR rate of 26% to 30%, the ECU controls the low-pressure EGR motor speed to 0, the first high-pressure EGR motor and the second high-pressure EGR motor are turned on, and run at the speed corresponding to the corresponding calibrated MAP2 data; Or the two high-pressure EGR pipelines are respectively provided with a first solenoid valve and a second solenoid valve, the two high-pressure EGR pipelines at the rear ends of the first solenoid valve and the second solenoid valve are combined into one high-pressure EGR pipeline, a third high-pressure EGR pump is provided on the combined high-pressure EGR pipeline, and the third high-pressure EGR pump is driven by a third high-pressure EGR motor; It also includes an ECU, which acquires in real time an accelerator pedal position signal, an engine speed signal, a low-pressure EGR motor speed signal, a third high-pressure EGR motor speed signal, a first solenoid valve switch signal, and a second solenoid valve switch signal respectively output by an accelerator pedal position sensor, an engine speed sensor, an intake air flow sensor, a low-pressure EGR motor speed sensor, a third high-pressure EGR motor speed sensor, a first solenoid valve switch sensor, and a second solenoid valve switch sensor; The ECU determines the engine operating condition and the EGR rate of the engine corresponding to MAP1 according to the accelerator pedal position signal and the engine speed signal, and controls the speed of the low-pressure EGR motor and the third high-pressure EGR motor, and the switches of the first solenoid valve and the second solenoid valve; When the engine operating condition corresponds to an engine EGR rate of 0% to 23%, the ECU controls the low-pressure EGR motor to start and run at the speed corresponding to the corresponding calibrated MAP2 data, the first solenoid valve and the second solenoid valve are closed, and the speed of the third high-pressure EGR motor is 0; When the engine operating condition corresponds to an engine EGR rate of 23% to 25%, the ECU controls the low-pressure EGR motor speed to 0, the first solenoid valve and the second solenoid valve are closed, and the third high-pressure EGR motor is turned on and runs at the speed corresponding to the corresponding calibrated MAP2 data; When the engine operating condition corresponds to an engine EGR rate of 26%~30%, the ECU controls the low-pressure EGR motor speed to 0, the first solenoid valve is opened, the second solenoid valve is opened, the third high-pressure EGR motor is opened, and runs at the speed corresponding to the corresponding calibrated MAP2 data.

2. A control method for a compact EGR system according to claim 1, characterized in that: The air is supercharged and cooled by the compressor and intercooler, and then enters the engine through the engine intake pipe to participate in combustion compression and work. The exhaust gas then passes through the engine exhaust manifold and enters the turbine. A part of the exhaust gas expands and does work. The exhaust gas after the turbine is discharged after being post-processed by DOC, DPF, and SCR. After the DOC and DPF, one low-pressure exhaust gas is taken for low-pressure exhaust gas recirculation and enters the low-pressure EGR pipeline, and then passes through the EGR cooler to re-enter the compressor for supercharging; after the exhaust manifold, two exhaust gases are taken for high-pressure exhaust gas circulation and enter the two high-pressure EGR pipelines. The exhaust gas of the two high-pressure EGR pipelines enters the EGR cooler shared with the low-pressure EGR pipeline and is gathered into one channel for cooling, and then merges with the intake air after the intercooler to enter the engine intake pipe to participate in combustion in the cylinder; or the two high-pressure EGR pipelines are merged into one channel and then enter the EGR cooler shared with the low-pressure EGR pipeline, and after cooling, merges with the intake air after the intercooler and enters the engine intake pipe to participate in combustion in the cylinder.

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