Adjustable two-stage turbocharged diesel engine supercharging system and method of use

Abstract

The application discloses a two-stage supercharging diesel engine supercharging system and a use method thereof. The system comprises a plurality of cylinders of a diesel engine, which are divided into a group of governing cylinders and a group of remaining cylinders; an air filter is connected to an air inlet of a low-pressure supercharger, a low-pressure air cooler, an air inlet of a high-pressure supercharger and a high-pressure air cooler in sequence through an air pipeline, and then connected to an air inlet main pipe; exhaust ends of the governing cylinders are connected to a governing exhaust gas main pipe in parallel; exhaust ends of the remaining cylinders are connected to a remaining exhaust gas main pipe in parallel; the governing exhaust gas main pipe and the remaining exhaust gas main pipe are connected to an exhaust gas collecting pipe through exhaust gas connecting pipes; the exhaust gas collecting pipe is connected to the high-pressure supercharger and the low-pressure supercharger in sequence through an exhaust gas pipeline; an exhaust gas bypass pipe is connected to the two superchargers and is provided with a bypass valve; a first EGR control valve of the governing exhaust gas main pipe is connected to the exhaust gas collecting pipe; one end of a circulating connecting pipe is connected to the governing exhaust gas main pipe, and the other end of the circulating connecting pipe is connected to the air inlet main pipe; an EGR cooler and a second EGR control valve are arranged on the circulating connecting pipe. The application adopts a two-stage supercharging and cylinder supercharging combined mode to improve the air inlet pressure of the diesel engine, reduce the oil consumption and emission of the diesel engine and increase the supercharging operation range of the diesel engine; meanwhile, an exhaust gas bypass structure is adopted to reduce the supercharger speed under high-speed working conditions and solve the problem of excessively high supercharging pressure; a governing cylinder structure and an EGR system are adopted to improve the air inlet pressure of the diesel engine under low working conditions and reduce the NOx emission of the diesel engine under high working conditions.

Description

Technical Field

[0001] This invention belongs to the field of engine technology, specifically relating to an adjustable two-stage turbocharged diesel engine turbocharging system and its usage method. Background Technology

[0002] As one of the main factors affecting the performance of diesel engines, exhaust gas turbocharging technology has become a major way to improve the power, economy, and emissions of diesel engines. Exhaust gas turbocharging technology utilizes the energy of engine exhaust gases to drive an exhaust turbine, which in turn increases the intake pressure and airflow through a compressor. The high-temperature exhaust gases from the engine cylinders enter the turbocharger through the exhaust pipe, driving the turbine blades to rotate, which in turn drives the coaxial compressor blades to rotate. This causes the compressor to compress the intake air, increasing the intake pressure and airflow into the cylinders, increasing the engine's air-fuel ratio, and improving engine performance. A two-stage turbocharging system refers to a turbocharging system consisting of two or more turbochargers connected in series. It is generally used in special environments where single-stage turbocharging cannot meet the performance requirements of the diesel engine. Traditional two-stage turbocharging systems have poor adaptability. Under low operating conditions, the diesel engine's exhaust volume is insufficient to provide enough exhaust gas for the two-stage turbocharging device to operate normally; under high operating conditions, the diesel engine speed is high and the exhaust flow is large, which can easily cause the two-stage turbocharging system to over-pressurize. Summary of the Invention

[0003] The technical problem this invention aims to solve is to overcome the shortcomings of existing systems and provide an adjustable two-stage turbocharged diesel engine turbocharging system and its usage method to adapt to the needs of two-stage turbocharging under different operating conditions. Under low operating conditions, it increases air compression efficiency; under high operating conditions, it avoids excessive turbocharging, reduces diesel engine fuel consumption and emissions, expands the turbocharging operating range of the diesel engine, and reduces NOx emissions from the diesel engine under high operating conditions.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an adjustable two-stage turbocharged diesel engine turbocharging system, comprising a diesel engine with multiple cylinders, and an air filter, a low-pressure turbocharger, a low-pressure air cooler, a high-pressure turbocharger, and a high-pressure air cooler; the multiple cylinders are divided into a group of controlling cylinders and a group of remaining cylinders; the injectors for injecting fuel into the controlling cylinders are independently controllable; the air filter is connected to the intake manifold via an air pipe, sequentially connecting the air inlet of the low-pressure turbocharger, the low-pressure air cooler, the air inlet of the high-pressure turbocharger, and the high-pressure air cooler; the exhaust ends of the controlling cylinders are connected to the controlling exhaust manifold; the exhaust ends of the remaining cylinders are connected to the remaining exhaust manifolds; the controlling exhaust manifold and the remaining exhaust manifolds are connected to the remaining exhaust manifolds; the controlling exhaust manifold and the remaining exhaust manifolds are connected to the remaining exhaust manifolds. All exhaust gas mains are connected to the exhaust gas collection pipe via exhaust gas connection pipes. The exhaust gas collection pipe is connected in series with the exhaust gas interface of the high-pressure turbocharger and the exhaust gas interface of the low-pressure turbocharger via exhaust gas pipelines. One end of the exhaust gas bypass pipe is connected to the exhaust gas pipeline between the exhaust gas interfaces of the high-pressure turbocharger and the low-pressure turbocharger, and the other end is connected to the exhaust gas collection pipe. An exhaust gas bypass valve is provided on the exhaust gas bypass pipe. A first EGR control valve is provided on the exhaust gas connection pipe from the exhaust gas main to the exhaust gas collection pipe. One end of the circulation connection pipe is connected to the exhaust gas main, and the other end is connected to the intake main. An EGR cooler and a second EGR control valve are provided on the circulation connection pipe.

[0005] As a further optimization, the exhaust bypass valve, the first EGR control valve, and the second EGR control valve are all electrically controlled valves with adjustable opening.

[0006] As a further optimization, there are two low-pressure turbochargers and one high-pressure turbocharger; the air inlets of the two low-pressure turbochargers are each connected to an air filter; the air outlets of the two low-pressure turbochargers are connected to the low-pressure air cooler through an air duct, and the air outlet of the low-pressure air cooler is connected to the air inlet of the high-pressure turbocharger through an air duct; the exhaust gas outlet tee of the high-pressure turbocharger is connected to the air inlet of the two low-pressure turbochargers.

[0007] As a further optimization, there are two low-pressure turbochargers and two high-pressure turbochargers; the air inlets of the two low-pressure turbochargers are each connected to an air filter, and the air outlets of the two low-pressure turbochargers are connected to the low-pressure air cooler via air ducts. The air outlets of the low-pressure air cooler are connected to the air inlets of the two high-pressure turbochargers via two air ducts; the air outlets of the two high-pressure turbochargers are connected to the high-pressure air cooler via air ducts; the exhaust gas collection pipe is connected to the exhaust gas inlets of the two high-pressure turbochargers via two exhaust gas ducts; the exhaust gas outlets of the two high-pressure turbochargers are connected to the exhaust gas inlets of the two low-pressure turbochargers via exhaust gas ducts; an exhaust gas bypass pipe is provided between each pair of high-pressure and low-pressure turbochargers; and each exhaust gas bypass pipe is equipped with an exhaust gas bypass valve.

[0008] The present invention also provides a method of using an adjustable two-stage turbocharged diesel engine system, comprising the following steps:

[0009] S1: When the diesel engine is operating at 0-20% emission levels, the two-stage turbocharging + cylinder injection mode is activated: the first EGR control valve is closed, the second EGR control valve is opened, the exhaust bypass valve is closed, and the injectors of the cylinders in the control system stop working; fresh air is compressed by the compressor of the two-stage exhaust gas turbocharger and cooled by two stages, then merges with the air discharged from the control system and cooled by the EGR air cooler, and then enters all cylinders of the diesel engine; the exhaust gas from the remaining cylinders passes through the turbines of the high- and low-pressure exhaust gas turbochargers in sequence before being discharged into the atmosphere;

[0010] S2: As the diesel engine speed increases, when the diesel engine is in the 20% to 80% exhaust condition, the two-stage turbocharging mode is activated: the first EGR control valve is opened, and the second EGR control valve and the exhaust bypass valve are closed; the injectors controlling the cylinders operate normally; fresh air is compressed by the two-stage exhaust gas turbocharger compressor and cooled by two stages before entering all cylinders of the diesel engine; the combustion exhaust gas passes through the high-pressure and low-pressure stage exhaust gas turbochargers in sequence before being discharged into the atmosphere;

[0011] S3: As the diesel engine speed continues to increase, when the diesel engine is in the 80% to 100% exhaust condition, the two-stage turbocharging + exhaust gas bypass mode is activated: the first EGR control valve is opened, the second EGR control valve is closed, and the exhaust gas bypass valve is opened; the injectors controlling the cylinders operate normally; fresh air is compressed by the two-stage exhaust gas turbocharger compressor and cooled by two stages before entering all cylinders of the diesel engine; the combustion exhaust gas is divided into two paths after entering the exhaust gas manifold, one path enters the low-pressure turbocharger turbine after passing through the exhaust gas bypass valve, and the other path enters the low-pressure turbocharger turbine after passing through the high-pressure turbocharger turbine, and finally is discharged into the atmosphere.

[0012] As a further optimization, in steps S2 to S3, when the diesel engine is operating at 20% to 100% emission levels, the two-stage turbocharging + exhaust gas bypass + EGR recirculation mode is activated: the first EGR control valve is closed, the second EGR control valve is opened, and the exhaust gas bypass valve is opened; the injectors of the control cylinders operate normally; fresh air is compressed by the two-stage exhaust gas turbocharger compressor and cooled by two stages before being discharged from the control cylinders and cooled by the EGR air cooler, then merged with the exhaust gas and enters all cylinders of the diesel engine; the combustion exhaust gas is divided into two paths after entering the exhaust gas manifold, one path enters the low-pressure turbocharger turbine after passing through the exhaust gas bypass valve, and the other path enters the low-pressure turbocharger turbine after passing through the high-pressure turbocharger turbine, and finally is discharged into the atmosphere.

[0013] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses a combination of two-stage turbocharging and cylinder turbocharging to increase the intake pressure of the diesel engine, reduce fuel consumption and emissions, and expand the turbocharging operating range of the diesel engine; simultaneously, it employs an exhaust gas bypass structure to reduce the turbocharger speed under high-speed conditions, solving the problem of excessively high turbocharger pressure; and it utilizes a control cylinder structure and an EGR system to increase the intake pressure of the diesel engine under low-speed conditions, reducing NOx emissions from the diesel engine under high-speed conditions. The design is reasonable and effective, and the product has high reliability. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the system structure in Embodiment 1 of the present invention;

[0015] Figure 2 This is a schematic diagram of the system structure in Embodiment 2 of the present invention;

[0016] Figure 3 This is a schematic diagram of the system in Embodiment 2 of the present invention in a two-stage boosting mode;

[0017] Figure 4 This is a schematic diagram of the system in Embodiment 2 of the present invention in a two-stage booster + exhaust bypass mode;

[0018] Figure 5 This is a schematic diagram of the system in Embodiment 2 of the present invention in a two-stage boost + exhaust gas bypass + EGR recirculation mode;

[0019] Figure 6 The schematic diagram shows the system in Embodiment 2 of this invention in a two-stage boosting + control cylinder air replenishment mode;

[0020] Figure 7 A schematic diagram of the system structure in Embodiment 3 of this invention;

[0021] Figure 8 A schematic diagram of the system structure in Embodiment 4 of this invention.

[0022] In the diagram: 1. Air filter, 2. Low-pressure booster, 3. Exhaust bypass valve, 4. Low-pressure air cooler, 5. High-pressure booster, 6. High-pressure air cooler, 7. EGR air cooler, 8. First EGR control valve, 9. Second EGR control valve, 10. Control cylinder, 11. Other cylinders, 12. Air duct, 13. Intake manifold, 14. Controlled exhaust manifold, 15. Other exhaust manifolds, 16. Exhaust connection pipe, 17. Exhaust manifold, 18. Exhaust duct, 19. Exhaust bypass pipe, 20. Circulation connection pipe. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] Example 1, please refer to Figure 1 .

[0025] This invention provides a technical solution: an adjustable two-stage turbocharged diesel engine turbocharging system, comprising a diesel engine with multiple cylinders, an air filter, a low-pressure turbocharger 2, a low-pressure air cooler 4, a high-pressure turbocharger 5, and a high-pressure air cooler 6; the multiple cylinders are divided into a group of control cylinders 10 and a group of remaining cylinders 11; the fuel injectors for injecting fuel into the control cylinders 10 can be independently controlled; furthermore, the control cylinders 10 can stop injecting fuel and become an air compression device to further increase the air pressure.

[0026] The air filter is connected in series via air pipe 12 to the air interface of low-pressure turbocharger 2, low-pressure air cooler 4, air interface of high-pressure turbocharger 5, and high-pressure air cooler 6, and then connected to the intake manifold 13. The intake manifold 13 is connected to multiple intake branch pipes, and each intake branch pipe is connected to the intake end of one of the cylinders. It can be seen that through the two turbochargers connected in series, the air enters the cylinder after two stages of pressurization.

[0027] The exhaust end of the control cylinder 10 is connected to the control exhaust gas main pipe 14; the exhaust ends of the remaining cylinders 11 are connected to the remaining exhaust gas main pipe 15; the control exhaust gas main pipe 14 and the remaining exhaust gas main pipe 15 are both connected to the exhaust gas collection pipe 17 through the exhaust gas connection pipe 16, and the exhaust gas collection pipe 17 is connected in series with the exhaust gas interface of the high-pressure turbocharger 5 and the exhaust gas interface of the low-pressure turbocharger 2 through the exhaust gas pipe 18; it can be seen that the exhaust gas is used twice through the two turbochargers connected in series, driving the turbines of the two-stage turbochargers to rotate.

[0028] One end of the exhaust bypass pipe 19 is connected to the exhaust pipe 18 between the exhaust port of the high-pressure booster 5 and the exhaust port of the low-pressure booster 2, and the other end is connected to the exhaust manifold 17. An exhaust bypass valve 3 is provided on the exhaust bypass pipe 19. It can be seen that the exhaust bypass pipe 19 connects the two boosters, diverting a portion of the exhaust gas entering the high-pressure booster 5 to the low-pressure booster 2, which can be used to avoid the high-pressure booster 5 from over-compressing the air. The diversion is controlled by a first EGR control valve 8 provided on the exhaust gas connecting pipe 16 from the exhaust manifold 14 to the exhaust manifold 17.

[0029] One end of the recirculation connection pipe 20 is connected to the main exhaust gas control pipe 14, and the other end is connected to the main intake pipe 13. An EGR cooler and a second EGR control valve 9 are installed on the recirculation connection pipe 20. Therefore, the recirculation connection pipe 20 can be used to return the exhaust gas generated by the main exhaust cylinder 10 in the diesel engine to the intake system for secondary combustion, reducing NO₂ levels. X emission.

[0030] Preferably, the exhaust bypass valve 3, the first EGR control valve 8, and the second EGR control valve 9 are all electrically controlled valves with adjustable openings. Specifically, the first EGR control valve 8 and the second EGR control valve 9 are high-temperature resistant butterfly valves. The openings of the first EGR control valve 8 and the second EGR control valve 9 can be calibrated at different speeds according to the intake air volume requirements of the diesel engine under different operating conditions, thereby meeting the fuel consumption and emission requirements of the diesel engine at various speeds. The exhaust bypass valve 3 is a high-temperature resistant butterfly valve. The opening of the exhaust bypass valve 3 can be adjusted and calibrated at different speeds according to the high-operational-condition intake air volume requirements of the diesel engine, reducing the intake pressure and turbocharger speed of the diesel engine under high operating conditions while meeting the fuel consumption and emission requirements.

[0031] The following steps are included when using it.

[0032] S1: When the diesel engine is in the 0-20% emission condition, start the two-stage turbocharging + cylinder injection mode: close the first EGR control valve 8, open the second EGR control valve 9, close the exhaust bypass valve 3, and the injector of the cylinder 10 stops working.

[0033] Fresh air is compressed by the compressor of a two-stage exhaust gas turbocharger and cooled by two stages of air cooling. It then merges with the air discharged from the control cylinder 10 and cooled by the EGR air cooler 7, and enters all cylinders of the diesel engine. The exhaust gas from the combustion of the remaining cylinders 11 passes through the turbines of the high-pressure and low-pressure exhaust gas turbochargers in sequence before being discharged into the atmosphere.

[0034] S2: As the diesel engine speed increases, when the diesel engine is in the 20% to 80% exhaust condition, the two-stage boost mode is activated: the first EGR control valve 8 is opened, and the second EGR control valve 9 and the exhaust bypass valve 3 are closed; the injector of the control cylinder 10 operates normally.

[0035] Fresh air is compressed by a two-stage exhaust gas turbocharger and cooled by two stages before entering all cylinders of the diesel engine; combustion exhaust gas passes through the turbines of high- and low-pressure exhaust gas turbochargers in sequence before being discharged into the atmosphere.

[0036] S3: As the diesel engine speed continues to increase, when the diesel engine is in the 80% to 100% exhaust condition, the two-stage turbocharging + exhaust gas bypass mode is activated: the first EGR control valve 8 is opened, the second EGR control valve 9 is closed, and the exhaust gas bypass valve 3 is opened; the injector of the control cylinder 10 operates normally.

[0037] Fresh air is compressed by the two-stage exhaust gas turbocharger compressor and cooled by two stages before entering all cylinders of the diesel engine. The combustion exhaust gas is collected in the exhaust gas manifold 17 and then split into two paths. One path passes through the exhaust gas bypass valve 3 and enters the turbine of the low-pressure turbocharger 2. The other path passes through the turbine of the high-pressure turbocharger 5 and then enters the turbine of the low-pressure turbocharger 2. Finally, the exhaust gas is discharged into the atmosphere.

[0038] It is evident that under low operating conditions (0-20% emission level), the two-stage turbocharger + control cylinder air injection mode is activated. The two turbochargers, along with the control cylinder 10, compress air, increasing the diesel engine's intake pressure, reducing fuel consumption and emissions, and expanding the turbocharger's operating range. Under normal operating conditions (20%-80% exhaust level), sufficient exhaust gas drives the two-stage turbochargers. The control cylinder 10 no longer compresses air but participates in normal operation, ensuring the engine's power output. By activating the two-stage turbocharger mode, the diesel engine obtains sufficient intake pressure, ensuring its power performance. Under high operating conditions (80%-100% exhaust level), the high engine speed significantly increases airflow. By activating the two-stage turbocharger + exhaust bypass mode, while the engine operates at full load, exhaust gas is diverted through the exhaust bypass pipe 19, reducing the turbocharger speed under high-speed conditions and resolving the problem of excessive boost pressure.

[0039] A better implementation method is to activate the two-stage turbocharging + exhaust gas bypass + EGR recirculation mode when the diesel engine is operating at 20% to 100% emission levels: close the first EGR control valve 8, open the second EGR control valve 9, and open the exhaust gas bypass valve 3; the injectors of the control cylinder 10 operate normally; fresh air is compressed by the two-stage exhaust gas turbocharger compressor and cooled by two stages before being discharged from the control cylinder 10 and cooled by the EGR air cooler 7, then merged with the exhaust gas and enters all cylinders of the diesel engine; the combustion exhaust gas merges into the exhaust gas manifold 17 and splits into two paths, one path enters the low-pressure turbocharger 2 turbine through the exhaust gas bypass valve 3, and the other path enters the low-pressure turbocharger 2 turbine through the high-pressure turbocharger 5 turbine, and finally is discharged into the atmosphere. It can be seen that at this time, while ensuring high-speed operation, the diesel engine introduces exhaust gas into the intake system for secondary combustion through the recirculation connection pipe 20, reducing NOx emissions from the high-operation diesel engine. This satisfies the need to reduce pollutant emissions while ensuring the power of the diesel engine.

[0040] In summary, this embodiment employs a combination of two-stage turbocharging and cylinder turbocharging to increase the diesel engine's intake pressure, reduce fuel consumption and emissions, and expand the turbocharged operating range. Simultaneously, it utilizes an exhaust bypass structure to reduce the turbocharger speed at high operating speeds, addressing the issue of excessively high turbocharger pressure. Furthermore, it employs a control cylinder structure and an EGR system to increase the diesel engine's intake pressure at low operating conditions, reducing NOx emissions at high operating conditions. The design is reasonable and effective, resulting in high product reliability.

[0041] Example 2, please refer to Figure 2-6 .

[0042] The difference between this embodiment and Embodiment 1 is that there are two low-pressure boosters 2 and two high-pressure boosters 5; the air inlets of the two low-pressure boosters 2 are each connected to an air filter, and the air outlets of the two low-pressure boosters 2 are connected to the low-pressure air cooler 4 through air pipes 12. The air outlet of the low-pressure air cooler 4 is connected to the air inlets of the two high-pressure boosters 5 through two air pipes 12; the air outlets of the two high-pressure boosters 5 are connected to the high-pressure air cooler 6 through air pipes 12; the exhaust gas collection pipe 17 is connected to the exhaust gas inlets of the two high-pressure boosters 5 through two exhaust gas pipes 18; the exhaust gas outlets of the two high-pressure boosters 5 are connected to the exhaust gas inlets of the two low-pressure boosters 2 through exhaust gas pipes 18; an exhaust gas bypass pipe 19 is provided between each pair of high-pressure boosters 5 and low-pressure boosters 2; and each exhaust gas bypass pipe 19 is equipped with an exhaust gas bypass valve 3.

[0043] As can be seen, in this embodiment, the first-stage turbocharger consists of two parallel low-pressure turbochargers 2, and the second-stage turbocharger consists of two parallel high-pressure turbochargers 5. This design is suitable for diesel engines with a large number of cylinders and a large displacement, such as in this embodiment. Figure 2The illustrated dual-row 16-cylinder diesel engine can also achieve the same technical effects as in Example 1.

[0044] Example 3, please refer to Figure 7 .

[0045] The difference between this embodiment and embodiment 2 is that there are two low-pressure boosters 2 and one high-pressure booster 5. The air inlets of the two low-pressure boosters 2 are each connected to an air filter; the air outlets of the two low-pressure boosters 2 are connected to the low-pressure air cooler 4 via air pipe 12, and the outlet of the low-pressure air cooler 4 is connected to the air inlet of the high-pressure booster 5 via air pipe 12; the exhaust gas outlet tee of the high-pressure booster 5 is connected to the air inlet of the two low-pressure boosters 2 via exhaust gas pipe 18.

[0046] As can be seen, in this embodiment, the first-stage turbocharger consists of two parallel low-pressure turbochargers 2, and the second-stage turbocharger consists of one high-pressure turbocharger 5. The number and type of turbochargers can be configured as needed to accommodate diesel engines with displacements between Embodiment 1 and Embodiment 2, and can also achieve the same technical effects as Embodiment 1.

[0047] Example 4, please refer to Figure 8 .

[0048] The difference between this embodiment and Embodiment 2 is that there are four low-pressure turbochargers 2 and two high-pressure turbochargers 5. The first-stage turbocharger is constructed by connecting two low-pressure turbochargers 2 in series to form a low-pressure turbocharger assembly. These two low-pressure turbocharger assemblies are then connected in parallel and connected in series with the two high-pressure turbochargers 5, which serve as the second-stage turbochargers. This further improves air compression efficiency and makes it suitable for diesel engines with larger displacements than those in Embodiment 2. It can also achieve the same technical effects as Embodiment 1.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An adjustable two-stage turbocharged diesel engine turbocharging system, comprising a diesel engine with multiple cylinders, and an air filter, a low-pressure turbocharger (2), a low-pressure air cooler (4), a high-pressure turbocharger (5), and a high-pressure air cooler (6); characterized in that: The multiple cylinders are divided into a group of control cylinders (10) and a group of other cylinders (11); the injectors that inject oil into the control cylinders (10) can be controlled independently; The air filter is connected to the air inlet of the low-pressure booster (2), the low-pressure air cooler (4), the air inlet of the high-pressure booster (5), and the high-pressure air cooler (6) in series via the air pipe (12) and then connected to the intake manifold (13); the exhaust end of the control cylinder (10) is connected to the control exhaust manifold (14); the exhaust ends of the other cylinders (11) are connected to the other exhaust manifold (15); the control exhaust manifold (14) and the other exhaust manifold (15) are both connected to the exhaust collection manifold (17) via the exhaust connection pipe (16); the exhaust collection manifold (17) is connected to the exhaust inlet of the high-pressure booster (5) and the exhaust inlet of the low-pressure booster (2) in series via the exhaust pipe (18); One end of the exhaust bypass pipe (19) is connected to the exhaust pipe (18) between the exhaust port of the high-pressure booster (5) and the exhaust port of the low-pressure booster (2), and the other end is connected to the exhaust gas collection pipe (17). An exhaust bypass valve (3) is provided on the exhaust bypass pipe (19). A first EGR control valve (8) is provided on the exhaust gas connection pipe (16) from the exhaust gas main pipe (14) to the exhaust gas collection pipe (17); One end of the circulation connecting pipe (20) is connected to the main exhaust gas pipe (14), and the other end is connected to the main intake pipe (13). An EGR cooler and a second EGR control valve (9) are provided on the circulation connecting pipe (20). The following steps are involved in its use: S1: When the diesel engine is in the 0-20% emission condition, the two-stage turbocharging + cylinder injection mode is activated: the first EGR control valve (8) is closed, the second EGR control valve (9) is opened, the exhaust bypass valve (3) is closed, and the injector of the cylinder (10) stops working; fresh air is compressed by the compressor of the two-stage exhaust gas turbocharger and cooled by two stages, and then merges with the air discharged from the cylinder (10) and cooled by the EGR air cooler (7), and then enters all cylinders of the diesel engine; the exhaust gas from the combustion of the remaining cylinders (11) passes through the turbines of the high and low pressure stage exhaust gas turbochargers in sequence and is then discharged into the atmosphere; S2: As the diesel engine speed increases, when the diesel engine is in the 20% to 80% exhaust condition, the two-stage boost mode is started: the first EGR control valve (8) is opened, and the second EGR control valve (9) and the exhaust bypass valve (3) are closed; the injector of the control cylinder (10) works normally. Fresh air is compressed by a two-stage exhaust gas turbocharger and cooled by two stages before entering all cylinders of the diesel engine; combustion exhaust gas passes through the turbines of high- and low-pressure exhaust gas turbochargers in sequence before being discharged into the atmosphere. S3: As the diesel engine speed continues to increase, when the diesel engine is in the 80% to 100% exhaust condition, the two-stage turbocharging + exhaust bypass mode is started: the first EGR control valve (8) is opened, the second EGR control valve (9) is closed, and the exhaust bypass valve (3) is opened; the injectors of the control cylinder (10) work normally; fresh air is compressed by the compressor of the two-stage exhaust gas turbocharger and cooled by two stages before entering all cylinders of the diesel engine; the combustion exhaust gas is divided into two paths after entering the exhaust gas manifold (17), one path enters the low-pressure turbocharger (2) turbine after passing through the exhaust bypass valve (3), and the other path enters the low-pressure turbocharger (2) turbine after passing through the high-pressure turbocharger (5) turbine, and finally is discharged into the atmosphere.

2. The adjustable two-stage turbocharged diesel engine turbocharging system according to claim 1, characterized in that: The exhaust bypass valve (3), the first EGR control valve (8), and the second EGR control valve (9) are all electrically controlled valves with adjustable opening.

3. The adjustable two-stage turbocharged diesel engine turbocharging system according to claim 1, characterized in that: There are two low-pressure boosters (2) and one high-pressure booster (5); The air inlets of the two low-pressure boosters (2) are each connected to an air filter; the air outlets of the two low-pressure boosters (2) are connected to the low-pressure air cooler (4) through an air pipe (12); the air outlet of the low-pressure air cooler (4) is connected to the air inlet of the high-pressure booster (5) through an air pipe (12). The exhaust gas pipe (18) of the exhaust gas outlet tee of the high-pressure booster (5) is connected to the air inlet of the two low-pressure boosters (2).

4. The adjustable two-stage turbocharged diesel engine turbocharging system according to claim 1, characterized in that: There are two low-pressure boosters (2) and two high-pressure boosters (5); The air inlets of the two low-pressure boosters (2) are each connected to an air filter, and the air outlets of the two low-pressure boosters (2) are connected to the low-pressure air cooler (4) through an air pipe (12). The air outlet of the low-pressure air cooler (4) is connected to the air inlets of the two high-pressure boosters (5) through two air pipes (12). The air outlets of the two high-pressure boosters (5) are connected to the high-pressure air cooler (6) through an air pipe (12). The exhaust gas collection pipe (17) is connected to the exhaust gas inlets of two high-pressure boosters (5) through two exhaust gas pipes (18); the exhaust gas outlets of the two high-pressure boosters (5) are connected to the exhaust gas inlets of two low-pressure boosters (2) through the exhaust gas pipes (18); An exhaust bypass pipe (19) is provided between each pair of high-pressure boosters (5) and low-pressure boosters (2); each exhaust bypass pipe (19) is provided with an exhaust bypass valve (3).

5. The adjustable two-stage turbocharged diesel engine turbocharging system according to claim 1, characterized in that: In steps S2 to S3, when the diesel engine is in the 20% to 100% emission condition, the two-stage turbocharging + exhaust bypass + EGR recirculation mode is started: the first EGR control valve (8) is closed, the second EGR control valve (9) is opened, and the exhaust bypass valve (3) is opened; the injector of the control cylinder (10) works normally; fresh air is compressed by the compressor of the two-stage exhaust gas turbocharger and cooled by two stages, and then discharged with the control cylinder (10) and cooled by the EGR air cooler (7) before the exhaust gas merges and enters all cylinders of the diesel engine; the combustion exhaust gas merges into the exhaust gas manifold (17) and is divided into two paths, one path enters the low-pressure turbocharger (2) turbine through the exhaust bypass valve (3), and the other path enters the low-pressure turbocharger (2) turbine through the high-pressure turbocharger (5) turbine and is finally discharged into the atmosphere.

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