CN211975155U - Sequential two-stage supercharging system for constant-pressure exhaust pipe - Google Patents

Abstract

The utility model provides a sequence second grade turbocharging system for level pressure blast pipe, relates to second grade turbocharging system technical field, including the level pressure blast pipe, be provided with relative waste gas import and the waste gas export that sets up on the level pressure blast pipe, and waste gas import slope towards the waste gas export. The utility model solves the problem that how to realize compact arrangement of the supercharger and reduce the production cost in the prior heavy engine and marine engine in the traditional technology; the exhaust pipe is limited by the exhaust flow passage, so that the loss caused by the twisting of the airflow is increased; how to ensure that the system response is improved when the engine rotates at a low speed; and how to effectively control the detonation pressure value of the engine at high rotating speed.

Description

Sequential two-stage supercharging system for constant-pressure exhaust pipe

Technical Field

The utility model relates to a second grade turbocharging system technical field, concretely relates to order second grade turbocharging system for level pressure blast pipe.

Background

Turbochargers use the energy of the exhaust gas from the engine to increase engine charge density. At present, the power of the engine is continuously improved, and higher requirements are put forward on a supercharging system. The supercharging pressure of the engine after two-stage supercharging is adopted can be greatly improved, both the high-pressure supercharger and the low-pressure supercharger can work in a working area with higher efficiency, and when the two superchargers work, the flow range of the engine is greatly widened. In a series two-stage supercharging system, the supercharging pressure can be increased to about 6.0 (namely the inlet pressure of an engine reaches 6 atmospheric pressures), single-stage supercharging is difficult to achieve, and the requirements of improving the power and meeting the emission of a diesel engine can be well met.

When the series two-stage supercharging system is applied to the existing engine to improve the power, the high-speed explosion pressure of the engine is high, the reliability is influenced, the pulse supercharging system is suitable for the internal combustion engine under the low supercharging condition, and the two systems can be adopted under the high supercharging condition. In the pulse turbocharging system, the loss of exhaust energy due to the throttling of exhaust gas is smaller than in the constant pressure turbocharging system, and the use of exhaust pulse energy is also considered. However, when the constant pressure ratio is increased, the pressure in the exhaust pipe of the constant pressure system is correspondingly increased, the loss of the exhaust energy is reduced, and the proportion of the pulse energy in the exhaust energy is reduced along with the increase of the pressure increase ratio, so that the utilization effects of the two systems on the exhaust energy are gradually close to each other along with the increase of the pressure increase ratio. Generally, when the boost ratio is less than 2.5, the use of exhaust energy is better with a pulse boost system.

Most of the time, the vehicle engine works under partial load, and has higher requirements on acceleration performance and torque characteristics, so that a pulse supercharging system is adopted in single supercharging. For the occasions such as ships, power generation and the like, because the requirement on variable working conditions is not outstanding, the space installation position of the pressurization system is not strictly limited, and the pressurization degree is generally higher, the constant-pressure pressurization system is adopted more. The middle supercharging degree of the sequential two-stage supercharging system is high, the application of the high-pressure stage greatly improves the low-speed performance of the engine, and the necessity of pulse energy at the low speed of the engine is weakened for the main advantages of the pulse turbocharging system. The temperature and pressure of the exhaust gas before the turbine are periodically pulsed, and the flow direction of the exhaust gas entering the blades of the working wheel is also periodically changed, so that the impact loss of the airflow is increased; the pulsating pressure sometimes causes a partial air inlet phenomenon of the turbine, so that the heat efficiency of the pulse system is low, the pressure in front of the turbine of the constant pressure system is constant, and the efficiency of the turbine is high.

The chinese intellectual property office discloses a patent No. 200880003872.6 which discloses that it is possible to reduce the number of parts and weight by integrating an exhaust manifold part, which is a cast member integrating an exhaust manifold and a high-pressure turbine housing of a high-pressure supercharger, with a low-pressure stage connecting part to which an exhaust gas control valve is assembled, and to reduce the number of assembling man-hours by bolt fastening or the like, and further to reduce the number of disassembling man-hours in a narrow engine room. In a two-stage supercharging type exhaust turbocharger, a high-pressure stage supercharger having a high-pressure turbine driven by exhaust gas discharged from an exhaust manifold of an engine and a low-pressure stage supercharger having a low-pressure turbine driven by exhaust gas after driving the high-pressure stage supercharger are arranged in series in a flow path of exhaust gas, and the flow rates of the exhaust gas flow path of the high-pressure stage supercharger and the exhaust gas flow path of the low-pressure stage supercharger are controlled by switching an exhaust gas control valve. The two-stage supercharging exhaust turbocharger is characterized in that the exhaust manifold, a high-pressure turbine housing of the high-pressure stage supercharger, and a valve housing accommodating the exhaust gas control valve are integrated to form an exhaust manifold integrated housing.

However, in the device, the exhaust pipe integrated housing is formed by an integrated casting piece, and in the application of the diesel market, the exhaust pipe integrated housing is only used in a small amount in a light diesel engine supercharging system of 3.0L or less, because the size of the exhaust pipe is small, the exhaust pipe is suitable for compact arrangement and use in a small engine, but the rejection rate is high; among them, the use of a supercharging system for medium and heavy duty engines, marine engines, etc. is limited by the volume of the supercharger, difficulty in processing, poor versatility, etc., and thus the exhaust pipe integrated housing is not suitable for the supercharging system for medium and heavy duty engines, marine engines, etc.

The intellectual property office of China discloses a patent with application number 201711177012.1, and the scheme comprises a high-pressure stage supercharger, a high-pressure stage turbine outlet smoke exhaust pipe, a supercharger support body and a low-pressure stage supercharger; the high-pressure stage supercharger is connected with an engine exhaust pipe; one end of the supercharger support body is fixed on an engine, the other end of the supercharger support body is connected with a low-pressure stage supercharger in a supporting mode through a hollow flange, the lower side of the supercharger support body is connected with a high-pressure stage turbine outlet smoke exhaust pipe, and a hollow part of the flange is an airflow channel; and the high-pressure stage turbine outlet smoke exhaust pipe is provided with a hose structure capable of adjusting the length and the angle. The utility model has the advantages of it is following: the utility model is applied to the mounting and supporting of the two-stage supercharging system of the engine, and realizes that the supporting of the high-low pressure supercharger does not influence each other through a supercharger supporting body with a hollow flange in the compact connection process; meanwhile, an adjustable corrugated pipe design structure is arranged in two supports of the high-pressure booster, so that the phenomenon of over-positioning of the supports can be avoided.

The device is composed of a high-pressure stage supercharger, a low-pressure stage supercharger, a control mechanism of the high-pressure stage supercharger, a connecting pipeline and the like through sequential two-stage supercharging, the volume and the weight of the system are increased, and the space of an existing engine cabin is difficult to place. Especially, in the engine with a single-stage supercharger, the installation and fixation of two superchargers are more complicated and difficult.

The chinese intellectual property office discloses a patent application No. 201711177012.1, which includes an exhaust manifold and an intake manifold distributed on both left and right sides of a cylinder head, and a supercharger for compressing fresh air flowing into the intake manifold by using fluid energy of exhaust gas discharged from the exhaust manifold. The supercharger is composed of a two-stage supercharger including a high-pressure supercharger coupled to the exhaust manifold and a low-pressure supercharger coupled to the high-pressure supercharger. The high-pressure supercharger is disposed on one of the left and right sides of the exhaust manifold, and the low-pressure supercharger is disposed above the exhaust manifold.

However, the device is only applied to series pressurization, and the mode that the high-pressure stage is disconnected and only the low-pressure stage works at a high speed or in a desired working condition cannot be realized.

In conclusion, research and development personnel in the prior art neglect the limitation that how to carry out compact integrated design on small and medium-sized engines is limited by high processing cost and difficult processing, and cannot apply the large-size integrated design to occasions such as medium and heavy-duty engines, marine engines and the like; the sequential connection of the single mode cannot ensure that the response of the system is improved when the engine rotates at a low speed, and how to effectively control the detonation pressure value of the engine when the engine rotates at a high speed; and the exhaust pipe of the existing two-stage supercharging system is limited by an exhaust runner, so that the loss caused by the torsion of the airflow is increased. Therefore, the prior art has obvious inconvenience and defects in practical use, and needs to be improved.

SUMMERY OF THE UTILITY MODEL

Aiming at the defects in the prior art, the utility model provides a sequential two-stage supercharging system for a constant pressure exhaust pipe, which is used for solving the problem that how to realize the compact arrangement of a supercharger in a medium-heavy engine, a marine engine and the like in the traditional technology and simultaneously reducing the production cost; the exhaust pipe is limited by the exhaust flow passage, so that the loss caused by the twisting of the airflow is increased; how to ensure the improvement of system response at low rotation speed; and how to effectively control the detonation pressure value of the engine at high rotating speed.

In order to solve the above problem, the utility model provides a following technical scheme:

the utility model provides a sequence second grade turbocharging system for level pressure blast pipe, includes the level pressure blast pipe, be provided with relative waste gas import and the waste gas export that sets up on the level pressure blast pipe, just waste gas import slope orientation waste gas export.

As an improved scheme, two exhaust outlets are arranged in parallel, and a high-pressure stage turbine and a low-pressure stage turbine which are arranged in parallel are correspondingly connected through the two exhaust outlets.

As an improved scheme, the waste gas outlet and the inner wall of the constant-pressure exhaust pipe are arranged in a rounding structure.

As an improved scheme, a compact connecting cavity is connected between the high-pressure stage turbine and the low-pressure stage turbine.

As an improvement, the compact connecting channel comprises an air guide tee connecting the vortex rear end of the high-pressure stage turbine and the vortex front end of the low-pressure stage turbine.

As an improved scheme, an on-off valve is further arranged in the air guide three-way pipe, and the air path of the constant-pressure exhaust pipe is divided into a first air path which is independently communicated with the front end of the vortex of the low-pressure stage turbine and a second air path which is independently communicated with the front end of the vortex of the high-pressure stage turbine by the on-off valve.

As an improved scheme, two inlet ends of the air guide three-way pipe are correspondingly connected with the waste gas inlet and the vortex rear end of the high-pressure stage turbine, and an outlet end of the air guide three-way pipe is connected with the vortex front end of the high-pressure stage turbine and forms a third air path through a part connected with the vortex rear end of the high-pressure stage turbine.

As an improved scheme, the high-pressure stage turbine is provided with a bypass valve, a bypass flow channel connected with an air outlet end of the bypass valve is arranged in the high-pressure stage turbine, an outlet of the bypass flow channel is communicated with the third air channel, and a fourth air channel is formed through the bypass flow channel.

As an improved scheme, the on-off valve comprises a butterfly valve, the butterfly valve is provided with two actions of opening and closing, and when the butterfly valve is in the closing action, the first air path is closed.

Compared with the prior art, the beneficial effects of the utility model are that:

the waste gas inlet is inclined towards the waste gas outlet, so that the air flow is better guided to the supercharger; the rounded corners of R15-25 are designed at the joints of two exhaust gas outlets and a constant-pressure exhaust pipe for guiding exhaust gas flow into the supercharger, so that the loss caused by the fact that high-speed flowing exhaust gas in the vertical direction at two sides is converted into flowing exhaust gas in the horizontal direction is reduced, and simulation calculation shows that the pressure loss is reduced by about 1.5% by the aid of the large rounded corners;

when the engine is at a low speed, a (small) high-pressure stage supercharger is mainly used, so that the system responsiveness is improved, and the air intake flow and the pressure are improved; only a (large) low-pressure stage supercharger is used at high speed, so that the detonation pressure value of the engine is effectively controlled; the low-pressure turbine and the high-pressure turbine are connected through the air guide three-way pipe, so that the volume is effectively reduced, and the split turbines are connected;

the high-low pressure supercharger can directly use the existing series supercharger, and a new supercharger shell mold does not need to be separately developed. Especially, in the performance matching stage, the existing supercharger can be used for multi-scheme matching, various schemes can be quickly combined, the test cost is low, and the period is short. The scheme is a pressurization system solution with low system cost, small occupied space and high reliability. When the product is expanded and applied, the pressurization system of the design method is easy to realize serialization;

the number of pipelines is small, and the connection relation is simplified, so that the weight of the system is greatly reduced, the number of components is reduced, the assembly working hours caused by bolt combination and the like are reduced, and the disassembly working hours in a narrow engine room are further reduced;

as a supercharging system supplier, the engine supercharger can be used for meeting multiple customers, the engine displacement, the power and the post-processing strategy are different, and the pneumatic parameters of the high-pressure and low-pressure superchargers are also different; the engines are different in structural arrangement, exhaust pipe structure, connector size and the like, when products are deformed, the engines can be combined and used through the existing series superchargers, and the product deformation and multi-scheme verification can be realized by designing connector pipelines needing to be changed. The number of dies is greatly reduced, and the cost of processing tools and cutters caused by different appearances is reduced, so that the manufacturing cost and the manufacturing period are reduced, the power turbine verification period can be shortened in the matching verification stage, and the customer requirements can be quickly responded; in the mass production stage and during the product expansion application, the production efficiency is improved, the profit rate of the product is increased, and the pressurization system of the design method is easy to realize serialization; the large technical problem is solved by simple improvement; the production cost is greatly reduced; and the problem that the traditional technology is constructed by complex parts is overcome; the structure is simple, and the assembly process steps are simple and convenient; the structure is simple, and the service life is long; simple structure and stable operation.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the technical solutions in the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

Fig. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic structural diagram of the external structure of the present invention;

FIG. 3 is a schematic structural view of the high-pressure stage exhaust outlet of the present invention;

in the figure: 1-a low-pressure stage turbine, 2-a high-pressure stage turbine, 3-a constant-pressure exhaust pipe, 4-a second gas path, 5-a third gas path, and 6-a fourth gas path; 7-a first gas path; 8-on-off valve; 9-high pressure stage waste gas outlet; 10-an air guide three-way pipe; 11-a bypass flow channel; 12-bypass valve, 13-exhaust gas inlet; 14-low pressure stage exhaust gas outlet; 15-rounded configuration.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.

As shown in fig. 1 to 3, the sequential two-stage supercharging system for a constant-pressure exhaust pipe includes a constant-pressure exhaust pipe 3, wherein the constant-pressure exhaust pipe 3 is provided with an exhaust gas inlet 13 and an exhaust gas outlet which are oppositely arranged, and the exhaust gas inlet 13 is inclined towards the exhaust gas outlet.

Two exhaust gas outlets are arranged in parallel and are correspondingly connected with a high-pressure stage turbine 2 and a low-pressure stage turbine 1 which are arranged in parallel through the two exhaust gas outlets, and the two exhaust gas outlets are respectively a high-pressure stage exhaust gas outlet 9 and a low-pressure stage exhaust gas outlet 14 which are correspondingly connected with the high-pressure stage turbine 2 and the low-pressure stage turbine 1. The high-pressure stage waste gas outlet 9 is positioned at the left upper part of the low-pressure stage waste gas outlet 14 and has an inclination, the outlet of the high-pressure stage turbine 2 is also moved to the left spatially, the spatial arrangement of the outlet and the air guide three-way pipe 10 is reasonably arranged, and the loss caused by the twisting of the air flow is reduced

The exhaust gas outlet and the inner wall of the constant pressure exhaust pipe 3 are arranged in a rounding structure 15.

A compact connecting cavity is connected between the high-pressure stage turbine 2 and the low-pressure stage turbine 1.

The compact connecting duct comprises an air guide tee 10 communicating the vortex aft end of the high pressure stage turbine 2 with the vortex forward end of the low pressure stage turbine 1.

The gas guiding three-way pipe 10 is continuously bent with an angle, so that the low-pressure stage turbine 1 is arranged at a close position in single pressurization, and arrangement of an air filter, an aftertreatment device and a pipeline of the aftertreatment device is well maintained. More importantly, the system needs to arrange pipelines at a certain distance, but the scheme does not cause insufficient support strength, large bending moment of the system and the like caused by a low-pressure stage supercharger, and does not occupy extra space.

An on-off valve 8 is further arranged in the air guide three-way pipe 10, and the air path of the constant pressure exhaust pipe 3 is divided into a first air path 7 which is independently communicated with the front end of the vortex of the low-pressure stage turbine 1 and a second air path 4 which is independently communicated with the front end of the vortex of the high-pressure stage turbine 2 by the on-off valve 8.

Two inlet ends of the air guide three-way pipe 10 are correspondingly connected with the waste gas inlet 13 and the vortex rear end of the high-pressure stage turbine 2, and the outlet end of the air guide three-way pipe 10 is connected with the vortex front end of the high-pressure stage turbine 2 and forms a third air path 5 through the part connected with the vortex rear end of the high-pressure stage turbine 2.

The high-pressure stage turbine 2 is provided with a bypass valve 12, a bypass flow channel 11 connected with the air outlet end of the bypass valve 12 is arranged in the high-pressure stage turbine 2, the outlet of the bypass flow channel 11 is communicated with the third air path 5, and a fourth air path 6 is formed through the bypass flow channel 11.

The on-off valve 8 comprises a butterfly valve which is provided with two actions of opening and closing, and when the butterfly valve is in the closing action, the first air path 7 is closed.

In the scheme, the volume of the air passage of the constant-pressure exhaust pipe 3 is more than 2 times of that of the pulse exhaust pipe, and the exhaust gas discharged by each cylinder body is the air passage of the common constant-pressure exhaust pipe 3, so that the constant-pressure exhaust pipe 3 can realize a good constant-pressure effect. In the design of exhaust pipes for more and more medium and heavy engines, marine engines and the like, a water cooling structure is used. Compared with a pulse exhaust system, the constant-pressure exhaust system is simpler, lower in cost and easy to arrange and maintain. In the whole supercharging system, the weight of the exhaust pipe accounts for more than 50%, so that the volume of the exhaust pipe can be properly reduced in practical application, and the light weight of the exhaust pipe is further realized.

The scheme is suitable for medium and heavy duty engines, marine engines and the like.

The high-pressure-stage supercharger has a high-pressure turbine driven by exhaust gas discharged from an exhaust manifold of the engine, and the low-pressure-stage supercharger 1 is driven by exhaust gas after driving the high-pressure-stage supercharger at a low speed.

In the structural arrangement of the sequential supercharging two-stage supercharging, low-pressure stage support is a main constraint factor, and in order to find a reliable support point, the supercharging system is very loose in arrangement and large in occupied space, or redesigns, produces exhaust pipes and other high-cost parts, the scheme is to perform innovative structural arrangement under the principle of similar sequential supercharging, and the exhaust pipes can be obtained by using the existing exhaust pipes without redesign; the new design effectively combines parts, the existing series high-low pressure stage supercharger, the on-off valve 8 and the newly designed air guide three-way pipe 10 are completely used, the air guide three-way pipe 10 realizes the dual functions of air flow circulation and system component support, and if the existing total intercooler is used, the total intercooler inlet three-way is added.

The support of the supercharger is the main part of the weight and stress of a supercharging system, the weight of the low-pressure stage supercharger is obviously higher than that of the high-pressure stage supercharger, no special support component is needed in the structure, the high-pressure stage turbine 2 and the low-pressure stage turbine 1 are directly fixed through the constant-pressure exhaust pipe 3, and the arrangement of an air filter, an aftertreatment device and pipelines of the aftertreatment device is well maintained.

More importantly, the system needs to arrange pipelines at a certain distance, but the scheme does not cause insufficient support strength, large bending moment of the system and the like caused by a low-pressure stage supercharger, and does not occupy extra space.

As for the pipeline arrangement, which is one of the main aspects affecting the fluid loss, important factors affecting the performance of the supercharging system, especially the compact design needs attention, the spatial arrangement is mainly considered in the patent,

when the engine is at a low speed, the on-off valve 8 is closed, the first air passage 7 is closed, the waste gas enters the front end of the vortex of the high-pressure stage turbine 2 along the second air passage 4 to do work, and then enters the front end of the vortex of the low-pressure stage turbine 1 through the third pipeline to do work, so that the waste gas at the outlet of the high-pressure stage turbine 2 smoothly enters the low-pressure stage turbine 1, the waste gas outlet connected with the high-pressure stage turbine 2 is arranged at the upper left part of the waste gas outlet of the low-pressure stage turbine 1 and has an inclination, the high-pressure stage turbine 2 also moves to the left in space, and the loss caused by the;

when the engine rotates at a middle speed, the on-off valve 8 is still closed, the first air passage 7 is still in a closed state, the bypass valve 12 is in an open state, most of the exhaust gas enters the front end of the vortex of the high-pressure stage turbine 2 along the second air passage 4 to do work, a small part of the exhaust gas does not enter the front end of the vortex of the high-pressure stage turbine 2 to do work, but is directly conveyed to the third pipeline along the fourth pipeline through the bypass valve 12, and then the two parts of the exhaust gas are conveyed to the front end of the vortex of the low-pressure stage turbine 1 together through the third pipeline to do work.

When the engine rotates at a high speed, the on-off valve 8 is closed, the first air passage 7 is opened, and because the pressure of the high-pressure stage turbine 2 after the front vortex is the same, the waste gas cannot enter the high-pressure stage turbine 2 through the second air passage 4, and the waste gas directly enters the front vortex end of the low-pressure stage turbine 1 through the first air passage 7 to do work, the air flow passages are compactly and smoothly transferred in three working modes.

The compressor has the same side structure, the three-way material at the outlet of the compressor is made of aluminum alloy, the weight is light, and the compressor can be supported by a low-pressure compressor shell.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the scope of the embodiments of the present invention, and are intended to be covered by the claims and the specification.

Claims (9)

1. A sequential two-stage supercharging system for a constant-pressure exhaust pipe is characterized in that: including level pressure blast pipe (3), be provided with waste gas import (13) and the waste gas export of relative setting on level pressure blast pipe (3), just waste gas import (13) slope orientation waste gas export.

2. A sequential two-stage supercharging system for a constant-pressure exhaust pipe according to claim 1, characterized in that: the two waste gas outlets are arranged in parallel, and the two waste gas outlets are correspondingly connected with a high-pressure stage turbine (2) and a low-pressure stage turbine (1) which are arranged in parallel.

3. A sequential two-stage supercharging system for a constant-pressure exhaust pipe according to claim 1, characterized in that: the waste gas outlet and the inner wall of the constant-pressure exhaust pipe (3) are arranged in a rounding structure (15).

4. A sequential two-stage supercharging system for a constant-pressure exhaust pipe according to claim 2, characterized in that: a compact connecting cavity channel is connected between the high-pressure stage turbine (2) and the low-pressure stage turbine (1).

5. The sequential two-stage supercharging system for a constant-pressure exhaust pipe according to claim 4, wherein: the compact connecting cavity comprises an air guide three-way pipe (10) which is communicated with the vortex rear end of the high-pressure stage turbine (2) and the vortex front end of the low-pressure stage turbine (1).

6. The sequential two-stage supercharging system for a constant-pressure exhaust pipe according to claim 5, wherein: an on-off valve (8) is further arranged in the air guide three-way pipe (10), and the air path of the constant pressure exhaust pipe (3) is divided into a first air path (7) which is independently communicated with the vortex front end of the low-pressure stage turbine (1) and a second air path (4) which is independently communicated with the vortex front end of the high-pressure stage turbine (2) by the on-off valve (8).

7. The sequential two-stage supercharging system for a constant-pressure exhaust pipe according to claim 5, wherein: the two inlet ends of the air guide three-way pipe (10) are correspondingly connected with the waste gas inlet (13) and the vortex rear end of the high-pressure stage turbine (2), the outlet end of the air guide three-way pipe (10) is connected with the vortex front end of the high-pressure stage turbine (2), and a third air path (5) is formed by a part connected with the vortex rear end of the high-pressure stage turbine (2).

8. A sequential two-stage supercharging system for a constant-pressure exhaust pipe according to claim 7, wherein: the high-pressure stage turbine (2) is provided with a bypass valve (12), a bypass flow channel (11) connected with an air outlet end of the bypass valve (12) is arranged in the high-pressure stage turbine (2), an outlet of the bypass flow channel (11) is communicated with the third air path (5), and a fourth air path (6) is formed through the bypass flow channel (11).

9. A sequential two-stage supercharging system for a constant-pressure exhaust pipe according to claim 6, characterized in that: the on-off valve (8) comprises a butterfly valve, the butterfly valve is provided with two actions of opening and closing, and when the butterfly valve is in the action of closing, the first air path (7) is closed.

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