Exhaust resonance tube of two-stroke horizontally-opposed four-cylinder piston engine

Abstract

The invention relates to an exhaust resonance tube of a two-stroke horizontally-opposed four-cylinder piston engine, which belongs to the field of two-stroke engines and comprises an exhaust manifold, a connecting component, an exhaust manifold and a tension spring component. One end of the exhaust manifold is provided with four branch air channels, and the other end of the exhaust manifold is a main air channel where the branch air channels converge. The four branch air passages are correspondingly connected with four exhaust ports of an engine respectively, and an air outlet of the exhaust manifold main air passage is in elastic airtight connection with an air inlet of the exhaust manifold through a connecting assembly. The exhaust manifold is a return reducing pipe, sequentially comprises a thin pipe section, a first diverging pipe section, a second diverging pipe section, an expansion pipe section, a rear taper pipe section and an exhaust tail pipe section and is used for adjusting contraction and expansion of exhaust waves in the exhaust manifold, and the phenomenon of back pressure is avoided. The tension spring assembly is used for vibration decoupling between the exhaust resonance tube and the engine. The two-stroke horizontally-opposed four-cylinder piston engine solves the problems that an existing two-stroke horizontally-opposed four-cylinder piston engine for the unmanned aerial vehicle has short-circuit loss, and the power is obviously reduced within a certain rotating speed range.

Description

Technical Field

[0001] The invention belongs to the field of two-stroke engines, and in particular relates to an exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine. Background Art

[0002] Two-stroke piston engines are widely used in the field of UAVs due to their simple structure and high power density. Existing two-stroke horizontally opposed four-cylinder piston engines use a straight exhaust pipe, which has an air inlet and an air outlet. When used in a two-stroke horizontally opposed four-cylinder piston engine, four exhaust pipes need to be installed at the same time.

[0003] When using a straight exhaust pipe, there is a phenomenon of fresh charge escaping and exhaust gas reflux during the engine's scavenging process, which is the "back pressure" effect, resulting in a large short-circuit loss, resulting in a decrease in charging efficiency and a decrease in power performance within a certain speed range (4500-5500rpm), making it difficult to meet the requirements of UAV power units for power and fuel economy. In addition, for a two-stroke horizontally opposed four-cylinder piston engine, the exhaust fluctuations of different cylinders will interfere with each other during the exhaust stroke, forming a complex airflow pattern, further reducing power performance.

[0004] At present, the existing exhaust systems are mainly aimed at optimizing their own structures and noise reduction design, and there is no systematic exhaust solution suitable for the unique airflow dynamics of the two-stroke horizontally opposed four-cylinder piston engine used in drones. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides an exhaust resonance tube for a two-stroke horizontally opposed four-cylinder piston engine, which solves the problem that the existing two-stroke horizontally opposed four-cylinder piston engine has short-circuit loss due to the use of a straight-exhaust pipe and has a significant power drop in the speed range of 4500 to 5500 rpm.

[0007] The technical solution of the present invention is: an exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine, comprising:

[0008] The exhaust manifold has four branch airways at one end, the upstream air inlets of the four branch airways are located in the same plane, and are all provided with connecting flanges, which are respectively connected to the four exhaust ports of the engine; the four branch airways merge into the main airway at the other end of the exhaust manifold;

[0009] A connection assembly, used for elastically and airtightly connecting a downstream air outlet of the exhaust manifold main air duct with an upstream air inlet of the exhaust main pipe;

[0010] The exhaust manifold is a meander-shaped reducer structure, and includes a thin pipe section, a first gradually expanding pipe section, a second gradually expanding pipe section, an expansion pipe section, a rear cone pipe section and an exhaust tail pipe section from its upstream air inlet to its downstream air outlet. Each pipe section is sealed and connected. The exhaust manifold is used to adjust the contraction and expansion of the exhaust wave of the engine in the exhaust manifold;

[0011] The tension spring assembly elastically connects the connecting flange of the exhaust main pipe and the exhaust manifold, and is used for vibration decoupling between the exhaust resonance pipe and the engine.

[0012] A further technical solution of the present invention is: the connecting assembly includes a first clamping ring, a first tension spring, a retaining ring and a graphite ring; multiple first clamping rings are evenly distributed on the circumferential outer diameter wall of the main air duct of the exhaust manifold and the thin tube section of the exhaust manifold, located at the butt joint between the two, and arranged one by one in opposite directions; two corresponding first clamping rings on the exhaust manifold and the exhaust manifold are a group, and a first tension spring is correspondingly installed to tighten the butt joint between the exhaust manifold and the exhaust manifold; the retaining ring and the graphite ring are coaxially sleeved on the outer diameter of the main air duct of the exhaust manifold in sequence, located between the exhaust manifold and the exhaust manifold, and are used to achieve a sealed butt joint between the exhaust manifold and the exhaust manifold.

[0013] A further technical solution of the present invention is: the exhaust manifold and the exhaust main pipe are both fixed with four first clamping rings, and four first tension springs are installed correspondingly; one end of the first tension spring is clamped and fixed to the first clamping ring of the exhaust manifold, and the other end is clamped and fixed to the first clamping ring of the exhaust main pipe.

[0014] A further technical solution of the present invention is: the retaining ring is annular, one side of which is against the first clamping ring located on the exhaust manifold, and the other side is in contact with the graphite ring surface; the graphite ring has a bowl-shaped structure, and an equal-diameter through hole is provided in the center to be sleeved on the main air duct of the exhaust manifold, and its bowl mouth end faces the retaining ring and is in surface contact with it, and its outer diameter profile is an arc surface, and the outer diameter arc surface of the graphite ring is connected to the inner wall of the arc-shaped bell-mouth structure set at the end of the thin tube section to form a spherical seal.

[0015] A further technical solution of the present invention is that the graphite ring is formed by compressing a metal mesh and flexible graphite, and is used to improve the wear resistance of the joint between the exhaust manifold and the exhaust main pipe.

[0016] A further technical solution of the present invention is: the adjacent joints of the thin tube section, the first gradually expanding tube section, the second gradually expanding tube section, the expansion tube section, the rear cone tube section and the exhaust tail pipe section have the same diameter and are all sealed and connected by welding; the thin tube section is a variable diameter gradually expanding bent tube, the first gradually expanding tube section is a variable diameter gradually expanding bent tube, the second gradually expanding tube section is a variable diameter gradually expanding straight tube, the expansion tube section is a constant diameter bent tube, the diameter of the expansion tube section reaches the maximum diameter of the exhaust main pipe, the rear cone tube section is a variable diameter contraction bent tube, and the exhaust tail pipe section is a constant diameter bent tube; the outlet end of the exhaust tail pipe section is rotated to the outside close to the thin tube section.

[0017] A further technical solution of the present invention is that the total length, length of each section and diameter parameters of the exhaust resonance tube are designed according to the matching engine speed, displacement and exhaust port size parameters.

[0018] A further technical solution of the present invention is: the tension spring assembly includes a second tension spring, a second clamping ring and a connecting angle piece; the second clamping ring is fixed above the outer diameter wall of the exhaust manifold, and the connecting angle piece is installed below the connecting flange of the exhaust manifold, one end of the second tension spring is clamped and fixed to the second clamping ring, and the other end is clamped and fixed to the connecting angle piece.

[0019] A further technical solution of the present invention is: the tension spring assembly is provided with three groups, the three second clamping rings are respectively fixed above the outer diameter walls of the first gradually expanding pipe section, the expansion pipe section and the rear cone pipe section of the exhaust manifold, the three connecting angle pieces are respectively installed below the connecting flanges close to the three second clamping rings, and the three second tension springs are respectively connected to a group of second clamping rings and connecting angle pieces that are close to each other.

[0020] A further technical solution of the present invention is that the connecting flange, the exhaust manifold, the first clamping ring, the second clamping ring, the retaining ring and the exhaust main pipe are all made of titanium alloy material to reduce the weight of the exhaust resonance pipe.

[0021] Beneficial Effects

[0022] The beneficial effects of the present invention are as follows: the exhaust resonance tube of a two-stroke horizontally opposed four-cylinder piston engine of the present invention adopts an exhaust manifold with a tree-shaped branch structure, and four branch airways are merged into a main airway. The four branch airways of the exhaust manifold are connected to the exhaust ports of the four cylinders of the engine, and the main airway of the exhaust manifold is elastically and airtightly connected to the air inlet of the exhaust manifold; through the design of the meander-shaped reducer structure of the exhaust manifold, the exhaust wave entering the exhaust manifold contracts and expands in the tube, forming an effective control of the exhaust wave, forming the optimal resonance effect of the exhaust wave in the tube, avoiding the "back pressure" phenomenon, and improving the charging efficiency. The elastic connection between the exhaust resonance tube and the engine is realized by the tension spring assembly, decoupling is achieved and vibration damage is reduced, and the fixed installation of the exhaust resonance tube is convenient. The compact structure of the exhaust manifold of the present invention in the shape of a meander in space meets the power requirements of the two-stroke horizontally opposed four-cylinder piston engine for unmanned aerial vehicles, and is conducive to system layout and lightweight design.

[0023] The exhaust manifold of the present invention comprises a thin pipe section, a first gradually expanding pipe section, a second gradually expanding pipe section, an expansion pipe section, a rear cone pipe section and an exhaust tail pipe section. Through three-dimensional nonlinear design, a compact structure is arranged in a zigzag shape in space. In order to achieve the best resonance effect, the total length of the exhaust manifold and the main diameter of the expansion pipe section are used as two independent variables, and 6 different pipe lengths and 5 different main diameter sizes are designed respectively. The optimal exhaust manifold component design parameters are optimized in combination with a one-dimensional simulation method. Based on the specific structural characteristics of the exhaust manifold, by controlling the contraction and expansion of the exhaust wave in the exhaust pipe, and the superposition of the pressure wave and the expansion wave, it is achieved that the fresh mixed gas that has entered the exhaust pipe is pressed back into the cylinder while preventing the discharge of the fresh mixed gas in the cylinder, thereby reducing the short-circuit loss, improving the charging efficiency, and improving the power characteristics of the engine.

[0024] Through experimental tests, it is found that the exhaust resonance tube of the present invention can increase the engine power by more than 10% at different altitudes.

[0025] The exhaust manifold of the present invention is elastically connected to the exhaust main pipe through a clamping ring and a first tension spring, and a sealing connection is achieved at the butt surface of the exhaust manifold and the exhaust main pipe through a graphite ring and a retaining ring, which reduces the transmission of vibration while ensuring sealing and improves the reliability of the exhaust resonance tube.

[0026] In the present invention, the connecting flange, the exhaust manifold, the first clamping ring, the second clamping ring, the retaining ring and the exhaust manifold are all made of titanium alloy (TA1) material, meeting the requirements of lightweight design of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the three-dimensional structure of the exhaust resonance pipe of the two-stroke horizontally opposed four-cylinder piston engine of the present invention;

[0028] Figure 2 It is a top view of the exhaust resonance pipe of the two-stroke horizontally opposed four-cylinder piston engine of the present invention;

[0029] Figure 3 It is a schematic diagram of each section of the exhaust manifold in the present invention;

[0030] Figure 4 It is a schematic diagram of the structure of the connection component in the present invention.

[0031] Explanation of the reference numerals: 1. Exhaust manifold, 11. Branch air duct, 12. Main air duct, 13. Connecting flange, 2. Connecting assembly, 21. First retaining ring, 22. First tension spring, 23. Retaining ring, 24. Graphite ring, 3. Exhaust main pipe, 31. Thin tube section, 32. First gradually expanding tube section, 33. Second gradually expanding tube section, 34. Expansion tube section, 35. Rear cone tube section, 36. Exhaust tail pipe section, 4. Tension spring assembly, 41. Second tension spring, 42. Second retaining ring, 43. Connecting angle piece. DETAILED DESCRIPTION

[0032] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0034] This embodiment is aimed at the problem in the prior art that the two-stroke horizontally opposed four-cylinder piston engine has low exhaust efficiency, serious short-circuit loss, and obvious power drop in the speed range of 4500-5500rpm due to the use of a straight exhaust pipe. Considering the use of the exhaust resonance effect, when the length and shape of the exhaust resonance tube match the engine speed and the scavenging exhaust phase, it not only helps to solve the "back pressure" effect of the exhaust, but also helps to improve the scavenging exhaust efficiency, increase the fresh mixture charge in the cylinder, and enhance the power performance of the two-stroke piston engine. The existing engine exhaust resonance tube is mainly suitable for automotive engines. Due to its structural characteristics, it requires a larger layout space, which is not conducive to the overall layout of the drone system and cannot be used for the two-stroke horizontally opposed four-cylinder piston engine of the drone. Therefore, the present invention proposes an exhaust resonance tube suitable for a two-stroke horizontally opposed four-cylinder piston engine.

[0035] See also Figure 1 , 2 The embodiment provides an exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine, comprising an exhaust manifold 1, a connecting assembly 2, an exhaust main pipe 3 and a tension spring assembly 4.

[0036] The exhaust manifold 1 has a tree-shaped branch structure, one end of which is four branch airways 11. The four branch airways 11 converge into the main airway 12 at the other end of the exhaust manifold, forming four air inlets and one air outlet. The upstream end of the four branch airways 11 is the air inlet of the exhaust manifold 1, and the downstream end of the main airway 12 is the air outlet of the exhaust manifold 1. The air inlet of the exhaust manifold 1 is connected to the exhaust ports of the four cylinders of the engine, and the air outlet of the exhaust manifold 1 is connected to the air inlet of the exhaust main pipe 3. Specifically, the air inlets of the four branch airways 11 are located in the same plane, and a connecting flange 13 is welded and fixed at the end of the air inlet of each branch airway 11. Each branch airway 11 is connected to the four exhaust ports of the engine through the connecting flange 13 at its end.

[0037] See also Figure 1 , 3 The exhaust manifold 3 is a zigzag reducer structure, one end of which is an air inlet and the other end is an air outlet. The air inlet of the exhaust manifold 3 is tightly connected with the air outlet of the exhaust manifold 1, and the exhaust outlet of the exhaust manifold 3 finally discharges the exhaust gas of the engine. The exhaust manifold 3 includes a thin pipe section 31, a first gradually expanding pipe section 32, a second gradually expanding pipe section 33, an expansion pipe section 34, a rear cone pipe section 35 and an exhaust tail pipe section 36 from its upstream air inlet to its downstream air outlet. Each pipe section is sealed and connected. The exhaust manifold is used to adjust the contraction and expansion of the exhaust wave of the engine in the exhaust manifold 3, so that the pressure wave and the expansion wave are superimposed, and the exhaust wave is effectively controlled to form the best resonance effect of the exhaust wave in the pipe, improve the exhaust efficiency, and then improve the charging efficiency.

[0038] Specifically, the adjacent joints of the thin tube section 21, the first gradually expanding tube section 32, the second gradually expanding tube section 33, the expansion tube section 34, the rear cone tube section 35 and the exhaust tail pipe section 36 of the exhaust manifold 3 have the same diameter, and are all sealed and connected by welding. The thin tube section 31 is a variable diameter gradually expanding bend, the first gradually expanding tube section 32 is a variable diameter gradually expanding bend, the second gradually expanding tube section 33 is a variable diameter gradually expanding straight tube, the expansion tube section 34 is a constant diameter bend, and the diameter of the expansion tube section 34 reaches the maximum diameter of the exhaust manifold 3, the rear cone tube section 35 is a variable diameter contraction bend, and the exhaust tail pipe section 36 is a constant diameter bend. The outlet end of the exhaust tail pipe section 36 is rotated to the lower outside near the thin tube section 31. The total length, length and diameter parameters of the exhaust manifold 3 are designed according to the matching engine speed, displacement and exhaust port size parameters.

[0039] In order to achieve the best resonance effect, the exhaust manifold 3 in this embodiment is designed with 6 different segment lengths and 5 different main diameter sizes, and the optimal exhaust manifold component design parameters are selected by combining the one-dimensional simulation method. When designing the structure of the exhaust manifold 3, after first determining the total length of the exhaust resonance pipe, the expansion and contraction angles of each pipe section according to parameters such as engine speed, displacement and exhaust port size, the length of the exhaust manifold 3 and the diameter of the expansion pipe section 34 are taken as independent variables, and the 6 length parameters and 5 diameter parameters of the remaining pipe sections are combined and determined according to the control variable method. Through one-dimensional performance simulation and artificial intelligence neural network optimization algorithm, with the goal of optimizing the power external characteristics, the optimal pipe section length and diameter parameters are finally obtained.

[0040] The three-dimensional structure of the exhaust manifold 3 is mainly for the convenience of spatial layout and installation. The shape is mainly determined to be a circular shape based on the outer dimensions of the prototype engine, the angle of the engine exhaust port and the propagation direction of the noise. The cubic spline curve function is used in the three-dimensional design. By keeping the expansion angle and length of each section unchanged, two sections of cubic spline functions are used to achieve three-dimensional modeling, which ensures the best exhaust resonance effect while meeting the layout of the limited space of the engine.

[0041] The outlet of the exhaust manifold 1 is connected to the inlet of the exhaust header 3 to achieve the resonance effect of the exhaust waves of the four cylinders. Figure 1 The connection assembly 2 is used for elastic and airtight connection between the air outlet of the exhaust manifold 1 and the air inlet of the exhaust manifold 3. The connection assembly 2 includes a first clamp ring 21, a first tension spring 22, a retaining ring 23 and a graphite ring 24.

[0042] Four first clamp rings 21 are evenly welded in the same circumference around the downstream end of the main air passage 12 of the exhaust manifold 1, and four first clamp rings 21 are evenly welded in the same circumference around the entrance of the exhaust manifold thin tube section 31. The four first clamp rings 21 on the exhaust manifold 1 correspond to the four first clamp rings 21 on the exhaust manifold 3 one by one, and are arranged facing each other, forming a first tension spring 22 installed in groups of two. There are four first tension springs 22 in total, which are correspondingly installed in the four groups of first clamp rings 21. One end of the first tension spring 22 is clamped and fixed with the first clamp ring 21 fixed on the exhaust manifold 1, and the other end is clamped and fixed with the first clamp ring 21 fixed on the exhaust manifold 3. The first tension spring 22 tightens the joint between the exhaust manifold 1 and the exhaust manifold 3, so that the two are tightened and connected while reducing the transmission of vibration. The retaining ring 23 and the graphite ring 24 are coaxially sleeved on the outer diameter of the main airway 12 of the exhaust manifold in sequence, and are located between the exhaust manifold 1 and the exhaust main pipe 3. The retaining ring 23 and the graphite ring 24 cooperate with each other, and the exhaust manifold 1 and the exhaust main pipe 3 are sealed and docked by the first tension spring 22. Specifically, the retaining ring 23 is annular, one side of which is against the first clamping ring 21 fixed to the exhaust manifold 1, and the other side is in surface contact with the graphite ring 24. The graphite ring 24 has a bowl-shaped structure, and a through hole of equal diameter is provided in the center to be sleeved on the main airway 12 of the exhaust manifold. The end of the bowl faces the retaining ring 23 and is in surface contact with it, and its outer diameter profile is an arc surface. Correspondingly, an arc-shaped bell-mouth structure is provided at the end of the thin tube section 31. The arc-shaped outer diameter surface of the graphite ring 24 contacts the inner wall surface of the bell-mouth structure of the thin tube section 31 to form a spherical seal. When the exhaust manifold 1 and the exhaust manifold 3 are tightened by the first tension spring 22, the retaining ring 23 and the graphite ring 24 are squeezed to achieve the sealed connection between the air outlet of the exhaust manifold 1 and the air inlet of the exhaust manifold 3. The graphite ring 24 is a graphite ring formed by compressing a metal mesh and flexible graphite, and is used to improve the wear resistance of the connection between the exhaust manifold 1 and the exhaust manifold 3.

[0043] See also Figure 1The tension spring assembly 4 elastically connects the exhaust main pipe 3 and the connecting flange 13 of the exhaust manifold 1, and is used for vibration decoupling between the exhaust resonance pipe and the engine, reducing vibration damage to the exhaust resonance pipe, and facilitating fixed installation of the exhaust resonance pipe. The tension spring assembly 4 is designed in three groups according to the specifications of the exhaust resonance pipe, and is evenly arranged along the rotation circle of the exhaust main pipe 3. The tension spring assembly 4 includes a second tension spring 41, a second clamping ring 42 and a connecting angle piece 43. The structure of the second clamping ring 42 is the same as that of the first clamping ring 21, and its fixed end is welded and fixed to the exhaust main pipe 3, and its clamping ring portion is used to install one end of the second tension spring 41. The connecting angle piece 43 is an L-shaped structure, and its side plate on one side is fixedly connected to the lower end face of the connecting flange 13 of the exhaust manifold 1, and a through hole is provided on the side plate on the other side for connecting the other end of the second tension spring 41. In this embodiment, three second clamping rings 42 are respectively fixed on the outer diameter walls of the first gradually expanding pipe section 32, the expansion pipe section 34 and the rear cone pipe section 35 of the exhaust manifold 3, three connecting angle pieces 43 are respectively installed under three connecting flanges 13 close to the installation positions of the three second clamping rings 42, and three second tension springs 41 are respectively connected to a group of adjacent second clamping rings 42 and connecting angle pieces 43. One end of the second tension spring 41 is clamped and fixed with the second clamping ring 42, and the other end is clamped and fixed with the connecting angle piece 43.

[0044] In order to meet the lightweight design requirements, in this embodiment, the connecting flange 13, the exhaust manifold 1, the first clamping ring 21, the second clamping ring 42, the retaining ring 23, and the exhaust main pipe 3 are all made of titanium alloy materials to achieve lightweight exhaust resonance tubes, which is beneficial to the lightweight of the two-stroke horizontally opposed four-cylinder piston engine.

[0045] The resonance tube in this embodiment is used for a naturally aspirated two-stroke horizontally opposed four-cylinder engine, in which the front two cylinders work and exhaust at the same time, and after an interval of 180° crankshaft angle, the rear two cylinders work and exhaust again. According to the gas state equation, when the exhaust gas passes through the expansion pipe of the exhaust manifold 3 (including the thin pipe section 31, the first gradually expanding pipe section 32, the second gradually expanding pipe section 33, and the expansion pipe section 34), the volume expands, the pressure decreases, and an expansion wave is generated. When the exhaust gas passes through the convergent pipe (including the rear cone pipe section 35 and the exhaust tail pipe section 36), the volume is compressed, the pressure increases, and a pressure wave is generated. The structural parameters such as the total length, the length and diameter of the exhaust resonance tube are related to the parameters such as the engine speed, displacement and exhaust port size. By controlling the contraction and expansion of the exhaust wave in the exhaust pipe, the pressure wave and the expansion wave are superimposed, thereby controlling the scavenging process of the engine. Within a certain speed range, when the engine is exhausting, the exhaust resonance tube can, on the one hand, allow the expansion wave to return to the exhaust port near the bottom dead center to accelerate the exhaust; on the other hand, it can allow the pressure wave to return to the exhaust port when the scavenging port is closed and the exhaust port is still open, thereby blocking the exhaust port and reducing the escape of fresh charge, ensuring the charging efficiency and the fresh charge capture rate, thereby preventing the discharge of the fresh mixture in the cylinder while pressing the fresh mixture that has entered the exhaust pipe back into the cylinder, thereby reducing short-circuit losses, improving charging efficiency, and enhancing power characteristics.

[0046] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. An exhaust resonance pipe for a two-stroke horizontally opposed four-cylinder piston engine, characterized in that: include: The exhaust manifold has four branch air passages at one end, the upstream air inlets of the four branch air passages are located in the same plane, and are all provided with connecting flanges, which are respectively connected to the four exhaust ports of the engine; The four branch airways merge into the main airway at the other end of the exhaust manifold; A connection assembly, used for elastically and airtightly connecting a downstream air outlet of the exhaust manifold main air duct with an upstream air inlet of the exhaust main pipe; The exhaust manifold is a meander-shaped reducer structure, and includes a thin pipe section, a first gradually expanding pipe section, a second gradually expanding pipe section, an expansion pipe section, a rear cone pipe section and an exhaust tail pipe section from its upstream air inlet to its downstream air outlet. Each pipe section is sealed and connected. The exhaust manifold is used to adjust the contraction and expansion of the exhaust wave of the engine in the exhaust manifold; The tension spring assembly elastically connects the connecting flange of the exhaust main pipe and the exhaust manifold, and is used for vibration decoupling between the exhaust resonance pipe and the engine.

2. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 1, characterized in that: The connecting assembly includes a first clamping ring, a first tension spring, a retaining ring and a graphite ring; a plurality of first clamping rings are evenly distributed on the circumferential outer diameter wall of the main airway of the exhaust manifold and the thin tube section of the exhaust manifold, located at the joint between the two, and arranged one by one in opposite directions; two corresponding first clamping rings on the exhaust manifold and the exhaust manifold form a group, and a first tension spring is correspondingly installed to tighten the joint between the exhaust manifold and the exhaust manifold; the retaining ring and the graphite ring are coaxially sleeved on the outer diameter of the main airway of the exhaust manifold in sequence, located between the exhaust manifold and the exhaust manifold, and are used to achieve a sealed joint between the exhaust manifold and the exhaust manifold.

3. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 2, characterized in that: The exhaust manifold and the exhaust main pipe are both fixed with four first clamping rings, and four first tension springs are installed correspondingly; one end of the first tension spring is clamped and fixed with the first clamping ring of the exhaust manifold, and the other end is clamped and fixed with the first clamping ring of the exhaust main pipe.

4. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 2, characterized in that: The retaining ring is annular, one side of which is against the first clamping ring located on the exhaust manifold, and the other side is in contact with the graphite ring surface; the graphite ring is a bowl-shaped structure in appearance, with an equal-diameter through hole in the center to be sleeved on the main airway of the exhaust manifold, the bowl mouth end faces the retaining ring and is in surface contact with it, and the outer diameter profile is an arc surface, and the outer diameter arc surface of the graphite ring is butted against the inner wall of the arc-shaped bell-mouth structure arranged at the end of the thin tube section to form a spherical seal.

5. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 4, characterized in that: The graphite ring is formed by compressing a metal mesh and flexible graphite, and is used to improve the wear resistance of the joint between the exhaust manifold and the exhaust main pipe.

6. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 1, characterized in that: The adjacent joints of the thin tube section, the first gradually expanding tube section, the second gradually expanding tube section, the expansion tube section, the rear cone tube section and the exhaust tail pipe section have the same diameter and are all sealed and connected by welding; the thin tube section is a variable diameter gradually expanding bent tube, the first gradually expanding tube section is a variable diameter gradually expanding bent tube, the second gradually expanding tube section is a variable diameter gradually expanding straight tube, the expansion tube section is a constant diameter bent tube, the diameter of the expansion tube section reaches the maximum diameter of the exhaust main pipe, the rear cone tube section is a variable diameter contraction bent tube, and the exhaust tail pipe section is a constant diameter bent tube; the outlet end of the exhaust tail pipe section is rotated to the outside close to the thin tube section.

7. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 6, characterized in that: The total length, length of each section and diameter parameters of the exhaust resonance pipe are designed according to the matching engine speed, displacement and exhaust port size parameters.

8. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 2, characterized in that: The tension spring assembly includes a second tension spring, a second clamping ring and a connecting angle piece; the second clamping ring is fixed above the outer diameter wall of the exhaust manifold, and the connecting angle piece is installed below the connecting flange of the exhaust manifold. One end of the second tension spring is clamped and fixed to the second clamping ring, and the other end is clamped and fixed to the connecting angle piece.

9. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 8, characterized in that: The tension spring assembly is provided with three groups, the three second clamping rings are respectively fixed on the outer diameter walls of the first gradually expanding pipe section, the expansion pipe section and the rear cone pipe section of the exhaust manifold, the three connecting angle pieces are respectively installed under the connecting flanges close to the three second clamping rings, and the three second tension springs are respectively connected to a group of second clamping rings and connecting angle pieces that are close to each other.

10. The exhaust resonance pipe of a two-stroke horizontally opposed four-cylinder piston engine according to claim 9, characterized in that: The connecting flange, the exhaust manifold, the first clamping ring, the second clamping ring, the retaining ring, and the exhaust main pipe are all made of titanium alloy material, which is used to reduce the weight of the exhaust resonance pipe.

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