CN220979704U - Gas mixer, exhaust gas recirculation system and engine - Google Patents

Abstract

The utility model discloses a gas mixer, an exhaust gas recirculation system and an engine, wherein the gas mixer comprises a shell, a spray pipe and a diffusion pipe, and for each micro-mixing channel, air entering from an air inlet and fuel gas in a first channel entering from the periphery of the first channel are mixed in the first channel along the flowing direction; because the flow cross section area of the micro-mixing channel is gradually reduced, under the Bernoulli principle, negative pressure is formed at the joint of the spray pipe and the diffusion pipe, so that the mixed air, fuel gas and waste gas entering the injection pipe are injected to the joint of the spray pipe and the diffusion pipe, and are uniformly mixed in the second channel, and the air, fuel gas and waste gas are mixed twice, so that the mixing uniformity of the gas mixer is improved. In addition, the waste gas is ejected to the joint of the spray pipe and the diffusion pipe through the ejection pipe, so that the resistance loss during mixing in a gas moderation period is reduced.

Description

Gas mixer, exhaust gas recirculation system and engine

Technical Field

The utility model relates to the technical field of engines, in particular to a gas mixer, an exhaust gas recirculation system and an engine.

Background

An exhaust gas recirculation system (Exhaust Gas Return, EGR for short) is an effective measure for reducing the engine emissions. As emissions regulations are upgraded, the demand for EGR rates is also increasing. The EGR rate has a greater effect on the in-cylinder combustion temperature, and as the EGR rate increases, both the in-cylinder transient maximum temperature and the average temperature decrease, and as the high temperature environment is a necessary condition for NO _X production, an increase in the EGR rate is beneficial to reducing the emissions of NO _X.

In addition, for a natural gas engine, the uniformity of mixing of natural gas with air and exhaust gas is also of great importance, and has significant influence on the dynamic property, economy, emission property, cycle variation and the like of the engine. In natural gas engines, the component responsible for this function is a gas mixer. The gas mixer is required to meet the requirements of mixing uniformity of three gases and to have the smallest possible flow resistance loss.

Therefore, how to improve the uniformity of gas mixing and reduce the flow resistance loss at the same time is a technical problem to be solved by those skilled in the art.

Disclosure of utility model

The utility model provides a gas mixer, an exhaust gas recirculation system and an engine, which are used for improving the uniformity of gas mixing and reducing the flow resistance loss.

In order to achieve the above object, the present utility model provides the following technical solutions:

in a first aspect, the present utility model provides a gas mixer comprising a housing, a nozzle and a diffuser, wherein the housing comprises an air inlet and a mixture outlet, and an exhaust gas inlet and a gas inlet, which are arranged in opposition;

The spray pipe is arranged at the air inlet and comprises at least three first channels, and the cross section of each first channel is gradually reduced from the spray inlet to the roar; the spray pipe is provided with a gas inlet hole which is communicated with the first channel and the gas inlet; an injection pipe is arranged in the spray pipe, one end of the injection pipe is communicated with the waste gas inlet, and the other end of the injection pipe extends to the throat of the spray pipe;

The diffuser pipe is arranged at the mixed gas outlet and comprises second channels with the number equal to that of the first channels, the cross section of each second channel is gradually increased from the initial port to the tail end port, and the caliber of the initial port of each second channel is consistent with that of the throat of each first channel; a second channel and a first channel form a micro-mixing channel.

Optionally, in the above gas mixer, the gas inlet and the exhaust gas inlet are both disposed on the peripheral surface of the housing, and the gas inlet and the exhaust gas inlet may be disposed opposite to each other.

Optionally, in the above gas mixer, the injection pipe includes an arc section and a straight line section, wherein the straight line section extends along the axial direction of the spray pipe, and the arc section is smoothly connected from the exhaust gas inlet to the straight line section.

Optionally, in the above gas mixer, a second channel is coaxial with a first channel.

Optionally, in the above gas mixer, the first channel and the second channel are uniformly arranged along a circumferential direction.

Optionally, in the above gas mixer, a waste gas ring cavity is further arranged between the shell and the spray pipe, and the waste gas inlet is communicated with the injection pipe through the waste gas ring cavity.

Optionally, in the gas mixer, a gas ring cavity is further arranged between the shell and the spray pipe, and the gas inlet is communicated with the gas inlet hole through the gas ring cavity.

Optionally, in the gas mixer, a plurality of gas inlet holes are uniformly arranged on the pipe wall corresponding to each first channel in the circumferential direction of the spray pipe.

Optionally, in the above gas mixer, a roar ring cavity is further provided between the housing and the nozzle, and surrounds the roar.

Optionally, in the gas mixer, the nozzle is further provided with a communication hole, and the communication hole is radially communicated with a part opposite to the roar ring cavity.

Optionally, in the above gas mixer, the end openings of the diffuser pipe are gradually fused together at the intersection of every two second channels through an arc surface.

In a second aspect, an embodiment of the present utility model provides an exhaust gas recirculation system, including a turbocharger, an intercooler, a gas mixer, an intake manifold, an engine block, an exhaust manifold, and an exhaust cooler, wherein a compressor of the turbocharger, the intercooler, the gas mixer, the intake manifold, the engine block, the exhaust manifold, and a turbine of the turbocharger are sequentially communicated; the engine body, the exhaust manifold, the exhaust cooler and the exhaust gas inlet of the gas mixer are communicated; the gas mixer is a gas mixer according to any one of the above.

Optionally, the exhaust gas recirculation system further includes a throttle valve, and the throttle valve is located between the gas mixer and the intercooler.

In a second aspect, embodiments of the present utility model provide an engine comprising an exhaust gas recirculation system as described above.

According to the technical scheme, for each micro-mixing channel, the air entering from the air inlet and the fuel gas in the first channel entering from the first channel along the flowing direction are mixed in the first channel; because the flow cross section area of the micro-mixing channel is gradually reduced, under the Bernoulli principle (the larger the cross section area is, the larger the pressure is, namely the larger the pressure potential energy is, the smaller the kinetic energy is, namely the smaller the speed of gas flow is), negative pressure is formed at the joint of the spray pipe and the diffusion pipe, so that mixed air, gas and waste gas entering the injection pipe are injected to the joint of the spray pipe and the diffusion pipe, and the air, the gas and the waste gas are uniformly mixed in the second channel, and the mixing uniformity of the gas mixer is improved because the air, the gas and the waste gas are mixed twice. In addition, the waste gas is ejected to the joint of the spray pipe and the diffusion pipe through the ejection pipe, so that the resistance loss during mixing in a gas moderation period is reduced.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is apparent that the drawings in the following description are only some examples or embodiments of the present utility model, and it is possible for those of ordinary skill in the art to obtain other drawings from the provided drawings without inventive effort, and to apply the present utility model to other similar situations from the provided drawings. Unless otherwise apparent from the context of the language or otherwise specified, like reference numerals in the figures refer to like structures or operations.

FIG. 1 is a schematic diagram of an EGR system according to the present utility model;

FIG. 2 is a schematic diagram of another EGR system provided by the present utility model;

FIG. 3 is an exploded view of a gas mixer according to the present utility model;

FIG. 4 is a schematic cross-sectional view of a cross-section of a gas blender provided by the present utility model;

FIG. 5 is a schematic cross-sectional view of another cross-section of a gas blender provided by the present utility model;

FIG. 6 is a cross-sectional view taken along section A-A of FIG. 5;

FIG. 7 is a cross-sectional view of section B-B of FIG. 5;

FIG. 8 is a perspective view of a diffuser according to the present utility model;

in the illustration, 100 is a turbocharger, 200 is an intercooler, 300 is a gas mixer, 400 is an intake manifold, 500 is a cylinder, 600 is an exhaust manifold, 700 is an exhaust cooler, 800 is a throttle valve, 900 is an exhaust throttle valve;

310 is a shell, 320 is a spray pipe, 330 is a diffuser pipe, 300a is an air inlet, 300b is a mixed gas outlet, 300c is an exhaust gas inlet, and 300d is a gas inlet;

311 is an exhaust gas annular cavity, 312 is a fuel gas annular cavity, 313 is a roar annular cavity;

321 is a first channel, 322 is an injection pipe, 323 is a gas inlet hole, 324 is a communication hole, 321a is a first inlet, and 321b is a first outlet;

331 is a second passageway, 331a is a second inlet, 331b is a second outlet.

Detailed Description

The utility model is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the utility model and are not limiting of the utility model. The described embodiments are only some, but not all, embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

An Engine (Engine) is a machine capable of converting other forms of energy into mechanical energy, including, for example, an internal combustion Engine (reciprocating piston Engine), an external combustion Engine (stirling Engine, steam Engine, etc.), a jet Engine, an electric motor, etc.

An exhaust gas recirculation system (Exhaust Gas Return, EGR for short) is an effective measure for reducing the engine emissions. As emissions regulations are upgraded, the demand for EGR rates is also increasing. The EGR rate has a greater effect on the in-cylinder combustion temperature, and as the EGR rate increases, both the in-cylinder transient maximum temperature and the average temperature decrease, and as the high temperature environment is a necessary condition for NO _X production, an increase in the EGR rate is beneficial to reducing the emissions of NO _X. In addition, for a natural gas engine, the uniformity of mixing of natural gas with air and exhaust gas is also of great importance, and has significant influence on the dynamic property, economy, emission property, cycle variation and the like of the engine. In natural gas engines, the component responsible for this function is a gas mixer. The gas mixer is required to meet the requirements of mixing uniformity of three gases and to have the smallest possible flow resistance loss. Therefore, how to improve the uniformity of gas mixing and reduce the flow resistance loss at the same time is a technical problem to be solved by those skilled in the art.

In order to solve the technical problems, the following description is provided with reference to the accompanying drawings:

Referring to fig. 1, fig. 1 discloses a schematic structural diagram of an exhaust gas recirculation system.

The exhaust gas recirculation system according to the embodiment of the present utility model may be applied to the above-described engine, and may include the turbocharger 100, the intercooler 200, the gas mixer 300, the intake manifold 400, the engine body 500, the exhaust manifold 600, and the exhaust cooler 700, wherein the compressor of the turbocharger 100, the intercooler 200, the gas mixer 300, the intake manifold 400, the engine body 500, the exhaust manifold 600, and the turbine of the turbocharger 100 are sequentially communicated; the engine block 500, the exhaust manifold 600, the exhaust cooler 700, and the exhaust gas inlet 300c of the gas mixer 300 are communicated.

The ventilation process of the engine supercharging system comprises the following steps: on the one hand, under the pumping action of the engine, air enters a compressor, the compressed high-temperature gas is cooled by an intercooler 200 after being compressed by the compressor, and the air enters a gas mixer 300; on the other hand, a part of the exhaust gas after the work is completed passes through the exhaust manifold 600 and enters the gas mixer 300 through the exhaust cooler 700; the other part of exhaust gas is led into a turbine, and energy generated by the turbine is transmitted to a compressor through a connecting shaft between the turbine and the compressor, so that the air inlet is compressed to improve the air inlet pressure. The natural gas, air and exhaust gas entering the gas mixer 300 are uniformly mixed in the gas mixer 300, and then enter the engine body 500 through the gas mixer 300 and the intake manifold 400.

The compressor of the turbocharger 100 communicates with the intercooler 200; the turbine of the turbocharger 100 communicates with the exhaust manifold 600. The compressor may include a centrifugal compressor, a positive displacement compressor, or another type of compressor for increasing the pressure within the air EGR flow path during engine operation. The turbine is located downstream of the exhaust manifold 600 and rotates as the exhaust gas expands through the turbine. The turbine is coupled to the compressor, for example via a shaft, and rotates the compressor. While the illustrated embodiment utilizes a turbocharger 100 to increase intake manifold 400 pressure, other compression methods, such as an electric or engine-driven compressor (e.g., turbocharger 100), may also be used. In some embodiments, a separate controller or Engine Control Unit (ECU) is used to control various aspects of system operation. For example, the controller may adjust the air-fuel ratio, spark timing, and EGR flow rate based on current operating conditions.

Intercooler 200 is configured to cool compressed air prior to the air entering intake manifold 400. The intercooler 200 is a heat exchanger, such as an air-to-air exchanger or an air-to-water exchanger.

Intake manifold 400 is configured to receive a combustible mixture to be combusted within engine block 500. That is, the intake manifold 400 communicates with an oxygen source and a fuel source. The combustible mixture may include air and any combustible fluid, such as natural gas, atomized gasoline or diesel. Although the illustrated embodiment includes a four-cylinder engine, any number of cylinders may be used.

The engine block 500 of an embodiment of the present utility model may be a piston engine block, but may also be other types of internal combustion engines, such as a rotary engine block or a gas turbine engine block.

The exhaust manifold 600 is configured to receive combustion products (exhaust gas) from the engine block 500. That is, the exhaust manifold 600 communicates with the outlet of the engine body 500. The exhaust gas inlet 300c of the gas mixer 300 communicates with the exhaust manifold 600.

An exhaust gas cooler is located between the exhaust manifold 600 and the gas mixer 300. The exhaust gas cooler may be operated to reduce the exhaust gas temperature prior to the gas mixer 300. The exhaust gas cooler is a heat exchanger, such as an air-air exchanger or an air-water exchanger.

Referring to fig. 2, fig. 2 discloses a schematic structural diagram of another exhaust gas recirculation system.

The exhaust gas recirculation system according to the embodiment of the present utility model may further include a throttle valve 800 based on the structure shown in fig. 1, where the throttle valve 800 is located between the intercooler and the intake manifold 400. Throttle 800 is located downstream of the compressor, and throttle 800 is located upstream of intake manifold 400. The throttle 800 is configured to regulate the flow of air from the ambient environment into the intake manifold 400, for example, by varying the cross-sectional area of the flow passage through the throttle 800. In some embodiments, throttle 800 may include a butterfly valve or a butterfly valve. Reducing the cross-sectional area of the flow passage through the throttle valve 800 may reduce the flow rate of air flowing through the throttle valve 800 toward the intake manifold 400.

In some embodiments of the utility model, the exhaust gas recirculation system may further include an exhaust gas throttle 900 positioned between the exhaust manifold 600 and the gas mixer 300 to regulate the flow of exhaust gas. The exhaust throttle valve 900 regulates the flow of exhaust gas by adjusting the cross-sectional area through the exhaust throttle valve 900. In some embodiments, the exhaust throttle 900 may include a butterfly valve, a needle valve, or another type of valve.

In the illustrated embodiment, the gas mixer 300 is located downstream of the throttle valve 800 and upstream of the intake manifold 400 of the gas mixer 300. The gas mixer 300 is located in an engine intake system and is connected to a throttle valve 800, an intake manifold 400, and an exhaust manifold 600. The fluid connection may be made from a conduit containing a flow channel allowing fluid flow. In some embodiments, the gas mixer 300 may be included within a conduit connecting the intake manifold 400 and the throttle valve 800, within the intake manifold 400, within the exhaust manifold 600, integrated within the throttle valve 800, or integrated within the EGR throttle valve 900. Details regarding the exemplary gas blender 300 will be described below in the present disclosure.

Referring to fig. 3 to 5, fig. 3 is an exploded view of a gas mixer 300 according to the present utility model; FIG. 4 is a schematic cross-sectional view of a cross-section of a gas blender 300 provided by the present utility model; fig. 5 is a schematic cross-sectional view of another cross-section of a gas blender 300 provided by the present utility model.

The gas mixer 300 according to the embodiment of the present utility model includes a housing 310, a nozzle 320, and a diffuser 330, wherein the housing 310 includes an air inlet 300a and a mixture outlet 300b, and an exhaust gas inlet 300c and a gas inlet 300d, which are arranged opposite to each other.

The nozzle 320 is disposed at the air inlet 300a, and the nozzle 320 includes at least three first channels 321, and the cross section of the first channels 321 is gradually reduced from the inlet 321a to the throat 321 b; the nozzle 320 is provided with a gas inlet 323 communicating the first channel 321 with the gas inlet 300 d; an injection pipe 322 is arranged in the spray pipe 320, one end of the injection pipe 322 is communicated with the waste gas inlet 300c, and the other end of the injection pipe 322 extends to a roar 321b of the spray pipe 320.

The diffuser 330 is disposed at the mixture outlet 300b, the diffuser 330 includes second channels 331 corresponding to the first channels 321, the cross section of the second channels 331 is gradually enlarged from the initial opening 331a to the final opening 331b, and the caliber of the initial opening 331a of the second channels 331 is consistent with the caliber of the roar opening 321b of the first channels 321; a second channel 331 and a first channel 321 form a micro-mixing channel.

For each micro-mixing channel, air entering from the air inlet 300a and fuel gas in the first channel 321 entering from the circumference of the first channel 321 are mixed in the first channel 321 along the flowing direction; because the flow cross-sectional area of the micro-mixing channel is gradually reduced, under the bernoulli principle (the larger the cross-sectional area is, the larger the pressure is, the smaller the kinetic energy is, the smaller the speed of gas flow is), the negative pressure is formed at the joint of the spray pipe 320 and the diffuser pipe 330, so that the mixed air and gas and the exhaust gas entering the injection pipe 322 are injected to the joint of the spray pipe 320 and the diffuser pipe 330, and are uniformly mixed in the second channel 331, and the mixing uniformity of the gas mixer 300 is improved because the air, the gas and the exhaust gas are mixed twice. In addition, the exhaust gas is injected to the junction of the nozzle 320 and the diffuser 330 through the injection pipe 322, thereby reducing the resistance loss during the mixing of the gas during the moderating period.

It should be noted that, the gas inlet 300d and the exhaust gas inlet 300c may be disposed on the peripheral surface of the housing 310, or may be disposed at one end of the housing 310 where the air inlet 300a is disposed. Preferably, the gas inlet 300d and the exhaust gas inlet 300c are disposed on the circumferential surface of the housing 310. Further, the gas inlet 300d and the exhaust gas inlet 300c may be disposed opposite to each other or may be disposed on the same side.

The ejector pipe 322 has the function of ejecting the exhaust gas to the joint of the first channel 321 and the second channel 331, and the ejector pipe 322 has a smooth structure so as to reduce the fluid resistance of the exhaust gas. When the exhaust gas inlet 300c is disposed on the peripheral surface of the housing 310, the injection pipe 322 includes a circular arc segment and a straight line segment, wherein the straight line segment extends along the axial direction of the injection pipe 320, and the circular arc segment is smoothly connected from the exhaust gas inlet 300c to the straight line segment. The arrangement of the circular arc section can reduce the fluid resistance of the exhaust gas in the steering process from the exhaust gas inlet 300c to the straight line section, and the straight line section enables the flow direction of the exhaust gas to be parallel to the axial direction of the spray pipe 320 when the injection pipe 322 is connected to the joint of the first channel 321 and the second channel 331, so that the resistance of the exhaust gas and other gases in mixing is reduced, and the mixing uniformity is improved.

To further reduce drag losses, in some embodiments of the present utility model, a second channel 331 is coaxial with a first channel 321 such that air entering the gas mixer 300 through the air inlet 300a is generally parallel to the micro-mixing channels, thereby achieving drag reduction.

To improve further mixing uniformity, in some embodiments of the present utility model, the first and second passages 321 and 331 are uniformly arranged in the circumferential direction so that the gas discharged from the gas mixture outlet 300b is mixed more uniformly.

In order to improve the further mixing uniformity, an exhaust gas ring cavity 311 is further arranged between the shell 310 and the spray pipe 320, and the exhaust gas inlet 300c is communicated with the injection pipe 322 through the exhaust gas ring cavity 311. After the gas has gas ports and enters the waste gas ring cavity 311, the gas circumferentially enters the injection pipe 322 from the waste gas ring cavity 311. Because the waste gas ring cavity 311 exists, after the waste gas is filled into the waste gas ring cavity 311, the pressure at the inlets of all the injection pipes 322 is equivalent, so that the mixing uniformity of the gas and the air is improved.

In order to improve further mixing uniformity, a gas ring cavity 312 is further arranged between the shell 310 and the spray pipe 320, and the gas inlet 300d is communicated with the gas inlet hole 323 through the gas ring cavity 312. After the fuel gas enters the fuel gas ring cavity 312 through the fuel gas inlet holes 323, the fuel gas enters the first channel 321 from the circumferential direction. Because of the gas ring cavity 312, after the gas is filled into the gas ring cavity 312, the pressure at all the gas inlet holes 323 is equivalent, so that the mixing uniformity of the gas and the air is improved. In the embodiment of the present utility model, a plurality of gas inlets 323 are uniformly arranged on the pipe wall of the nozzle 320 corresponding to each first channel 321 in the circumferential direction, so as to further improve the mixing uniformity.

In order to make the pressures at the gas inlets 323 equal, in the embodiment of the present utility model, the nozzle 320 is further provided with a communication hole 324, so that the gas inlets 323 far apart from each other can be communicated, thereby ensuring that the pressures at all the gas inlets are equal, as shown in fig. 6.

In order to ensure that the nozzle 320 is also provided with a nozzle ring cavity 313 between the housing 310 and the nozzle 320, the nozzle ring cavity 313 surrounds the nozzle 321b, so that the pressure at the nozzle 321b is the same, thereby improving the mixing uniformity therein.

Further, in order to reduce the influence of the abrupt pressure change on the uniformity of mixing, the nozzle 320 is further provided with a communication hole 324, and the communication hole 324 communicates with the opposite part of the throat cavity 313 along the radial direction, so that the throat cavity 313 can be further communicated through the communication hole 324 besides communicating in its own structure, and therefore, when the abrupt pressure change occurs at the throat 321b, the two parts are communicated to ensure that the pressure at the throat is the same, as shown in fig. 7.

For each second passage 331 of the diffuser pipe 330, the flow cross-sectional area becomes gradually larger in the flow axial direction to gradually convert the velocity energy obtained through the nozzle 320 into pressure energy using the bernoulli principle, while air, gas and exhaust gas are further mixed in the passage. At the intersection of each two second channels 331 at the end port 331b of the diffuser 330, the two channels are gradually merged together by an arc surface, so as to reduce the local resistance loss of converging the multiple channels into a single channel outlet, as shown in fig. 8.

Wherein, in the description of the embodiments of the present utility model, unless otherwise indicated, "/" means or, for example, a/B may represent a or B; "and/or" herein is merely an association relationship describing an association object, and means that three relationships may exist, for example, a and/or B may mean: a exists alone, A and B exist together, and B exists alone.

The terms "first" and "second" are used above for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.

For convenience of description, only a portion related to the present utility model is shown in the drawings. Embodiments of the utility model and features of the embodiments may be combined with each other without conflict.

The above description is only illustrative of the preferred embodiments of the present utility model and the technical principles applied, and is not intended to limit the present utility model. Various modifications and variations of the present utility model will be apparent to those skilled in the art. The scope of the utility model is not limited to the specific combination of the above technical features, but also covers other technical features formed by any combination of the above technical features or their equivalents without departing from the inventive concept. Such as the above-mentioned features and the technical features disclosed in the present utility model (but not limited to) having similar functions are replaced with each other.

Claims (13)

1. A gas mixer, comprising a housing, a nozzle and a diffuser pipe, wherein the housing comprises an air inlet and a mixed gas outlet, and an exhaust gas inlet and a gas inlet which are arranged oppositely;

The spray pipe is arranged at the air inlet and comprises at least three first channels, and the cross section of each first channel is gradually reduced from the spraying inlet to the roar; the spray pipe is provided with a gas inlet hole which is communicated with the first channel and the gas inlet; an injection pipe is arranged in the spray pipe, one end of the injection pipe is communicated with the waste gas inlet, and the other end of the injection pipe extends to the roar of the spray pipe;

The diffuser pipe is arranged at the mixed gas outlet, the diffuser pipe comprises second channels with the number equal to that of the first channels, the section of each second channel is gradually enlarged from the initial port to the tail port, and the caliber of the initial port of each second channel is consistent with that of the throat of each first channel; one of the second channels and one of the first channels form a micro-mixing channel.

2. The gas mixer of claim 1, wherein the gas inlet and the exhaust gas inlet are each disposed on a peripheral surface of the housing, the gas inlet and the exhaust gas inlet being oppositely disposed.

3. The gas mixer of claim 1, wherein the ejector tube comprises an arc segment and a straight segment, wherein the straight segment extends in an axial direction of the nozzle, and the arc segment is smoothly connected from the exhaust gas inlet to the straight segment.

4. The gas mixer of claim 1 wherein one of said second channels is coaxial with one of said first channels; or the first and second channels are uniformly arranged in the circumferential direction.

5. The gas mixer of claim 1, wherein a waste gas annulus is further provided between the housing and the nozzle, and the waste gas inlet communicates with the ejector tube through the waste gas annulus.

6. The gas mixer of claim 1, wherein a gas ring cavity is further provided between the housing and the nozzle, and the gas inlet communicates with the gas inlet aperture through the gas ring cavity.

7. The gas mixer of claim 1, wherein a plurality of gas inlet holes are uniformly circumferentially arranged on the pipe wall of the spray pipe corresponding to each first channel.

8. A gas mixer according to claim 1, wherein a roar annulus is further provided between the housing and the nozzle, the roar annulus surrounding the roar.

9. A gas mixer as claimed in claim 6, wherein the lance is further provided with a communication hole which communicates radially with the opposite part of the roar annulus.

10. The gas mixer of claim 1 wherein the diffuser pipe ends are gradually joined together at the intersection of each two of said second passages by a cambered surface.

11. An exhaust gas recirculation system, comprising a turbocharger, an intercooler, a gas mixer, an intake manifold, an engine body, an exhaust manifold and an exhaust cooler, wherein a compressor of the turbocharger, the intercooler, the gas mixer, the intake manifold, the engine body, the exhaust manifold and a turbine of the turbocharger are sequentially communicated; the engine body, the exhaust manifold, the exhaust cooler and the exhaust gas inlet of the gas mixer are communicated; the gas mixer is a gas mixer according to any one of claims 1 to 10.

12. The exhaust gas recirculation system of claim 11, further comprising a throttle valve positioned between the gas mixer and the intercooler.

13. An engine comprising an exhaust gas recirculation system according to claim 11 or 12.