Exhaust system device and design method thereof

Abstract

The invention relates to an exhaust system device and a design method, and belongs to the technical field of after-treatment systems of heavy-duty cars. The exhaust system device comprises a hot end air inlet pipe, a flexible pipe and an exhaust pipe which are sequentially connected, the hot end air inlet pipe and the flexible pipe are fixedly connected through a clamp, the hot end air inlet pipe is connected to the end of a vehicle engine through a hinged first support, and the air inlet end of the hot end air inlet pipe is in butt joint with an outlet of an engine supercharger. The exhaust pipe is connected to the vehicle frame through a hinged second support, the air outlet end of the exhaust pipe is in butt joint with an exhaust postprocessor, and the postprocessor is connected with the vehicle frame end of the vehicle through a third support. The exhaust system device is designed based on the engine acting excitation frequency and the road excitation frequency of the vehicle, resonance between the exhaust system and the excitation frequency and the road excitation in the full-rotating-speed interval of the engine is avoided, and the reliability and durability of the exhaust system are improved.

Description

Technical Field

[0001] The invention relates to the technical field of heavy-duty vehicle aftertreatment systems, and in particular to an exhaust system device and a design method thereof. Background Art

[0002] With the deepening of the National VI emission regulations for heavy-duty commercial vehicles, as the world's most stringent emission regulations for heavy-duty commercial vehicles, the durability of the after-treatment system is required to reach 7 years or 700,000 kilometers, and the emissions must meet the standards throughout the life cycle of the vehicle. The high standards of the regulations put forward higher standards for the reliability, durability and robustness of the after-treatment system and its components. Most of the existing automobile exhaust systems are designed only considering factors such as their sealing performance, exhaust after-treatment capabilities, and vehicle displacement. In actual application, problems such as loose exhaust pipes and air leakage occur, affecting the normal operation of the exhaust system. Therefore, the development of a high-efficiency, replicable, and easy-to-promote high-reliability exhaust system device and method has become an urgent need in the field of after-treatment systems. Summary of the invention

[0003] In order to solve the problems in the prior art, the present invention patent designs an exhaust system device to solve the problem of poor durability of the existing automobile exhaust system device.

[0004] The technical solution adopted by the present invention is: the exhaust system device includes a hot end intake pipe, a flexible pipe and an exhaust pipe connected in sequence, the hot end intake pipe and the flexible pipe are connected and fixed by a clamp, the hot end intake pipe is connected to the vehicle engine end through a first bracket, and its intake end is butted with the engine supercharger outlet through a clamp, the intake end of the exhaust pipe is welded integrally with the flexible pipe, the exhaust pipe is connected to the frame through a second bracket, and its outlet end is butted with an exhaust after-processor, and the after-processor is connected to the frame end of the vehicle through a third bracket, the modal frequency of the hot end intake pipe of the exhaust system device is higher than the excitation frequency of the vehicle engine, and the modal frequency of the exhaust pipe is higher than the road vibration frequency generated during vehicle driving.

[0005] The specific steps of the design method of the exhaust system device provided by the present invention are as follows:

[0006] (1) Determine the pipe diameter of the exhaust system device according to the engine displacement. The pipe diameter is calculated as follows:

[0007] ΦD≥10V

[0008] Where: ΦD——pipeline diameter, unit is mm;

[0009] V——engine displacement, in L;

[0010] (2) Calculate the required length of the flexible tube according to the pipe diameter, and arrange the flexible tube posture according to the engine runout. The pipe diameter is between 60mm-150mm, and the engine runout is the design value, which is within the range of 10mm-30mm. The flexible tube length must be more than 2.5 times the diameter to achieve a good shock absorption effect. The diameter of the flexible tube is consistent with the hot end intake and exhaust pipes. The formula for calculating the length of the flexible tube is as follows:

[0011] L≥2.5Φd;

[0012] Where: L is the length of the flexible tube, in mm;

[0013] Φd——the diameter of the flexible pipe, in mm;

[0014] (3) Determine the modal frequency of the hot-end intake pipe according to the vibration frequency of the engine. The modal frequency of the hot-end intake pipe needs to avoid the range of the engine excitation frequency. The calculation formula is based on the engine excitation frequency:

[0015] f=nr / 120

[0016] Where: f——engine excitation frequency,

[0017] n——engine rated frequency;

[0018] r——number of engine cylinders;

[0019] The modal frequency of the hot end intake pipe is determined by the highest excitation frequency coefficient k of the engine. The modal frequency of the hot end intake pipe after supercharging must be greater than or equal to k*f;

[0020] (4) Determine the modal frequency of the exhaust pipe based on the influence of road vibration. The modal frequency of the exhaust pipe needs to be higher than the excitation frequency of the road surface. The formula for calculating the modal frequency of the exhaust pipe is:

[0021]

[0022] Where: f is the modal frequency of the exhaust pipe,

[0023] k——rigidity of the exhaust pipe,

[0024] m——the mass of the exhaust pipe,

[0025] The road excitation frequency is related to the structural strength of the vehicle chassis and is obtained on the actual road surface. Generally, the road excitation frequency is ≤30Hz.

[0026] (5) Determine the exhaust pipe sealing structure and pipe connection method based on the relevant requirements for airflow sealing;

[0027] (6) Design the exhaust system support structure based on the vehicle chassis layout and the external structure of the post-processor. The design should refer to the calculation results of steps (3) and (4) to avoid resonance between the support structure and the vehicle engine.

[0028] Furthermore, the sealing gasket of the exhaust sealing structure in step (5) is made of expanded graphite, an alloy coated with a high-temperature resistant coating, etc., and the compression range should meet 15%-25% of the total thickness; after unloading, the rebound rate should be greater than the requirement of 5%-10% of the total thickness.

[0029] Furthermore, the design of the support structure in step (6) needs to take into account the accumulated tolerances during the manufacturing process so that each bracket has the ability to eliminate tolerances.

[0030] Furthermore, in the support structure design of step (6), the single bracket mounting hole of the post-processor on the frame beam should be connected by at least two holes, and the two ends of the second bracket of the exhaust pipe are required to be connected by two holes.

[0031] Furthermore, in the support structure design of step (6), for exhaust system pipes longer than 1.5 m, at least two or more support points should be designed to limit and support the exhaust system pipes in different directions.

[0032] Furthermore, in the design of the support structure in step (6), support points must be designed within 0.5 m in front and behind the flexible pipe to ensure the correct installation state of the flexible pipe.

[0033] Furthermore, in the support structure design of step (6), for the front exhaust design, the fixation of the exhaust pipe must have a seismic isolation design, using rubber shock-absorbing pads to eliminate vibration transmission between the exhaust pipe and the frame, and eliminate the risk of resonance between the bracket and the chassis.

[0034] Furthermore, in the support structure design of step (6), for the upper exhaust design, a pipeline flexible part must be connected to the rear side of the post-processor, and a fixed bracket must be designed within 0.5m of the pipeline flexible part to eliminate manufacturing tolerances and isolate vibrations.

[0035] Furthermore, the design method also includes calculating the airflow pulse frequency, and the airflow pulse frequency calculation formula is: frequency = (engine speed × number of cylinders) ÷ 120. By matching flexible tubes with different stiffnesses, when the exhaust throttle valve or exhaust brake butterfly valve intervenes in the work, the airflow frequency is prevented from resonating with the post-processor and accessory frequencies to cause damage.

[0036] Compared with the prior art, the exhaust system device and the design method thereof designed in the present invention are improved in that:

[0037] The exhaust system device and design method of the patented design of this invention are the first in the industry to propose a method and principle for designing an after-treatment system based on the engine vibration frequency, which improves the reliability and durability of the after-treatment system pipelines. It is different from the existing method of evaluating the static strength and fatigue number of components by loading with a certain gravitational acceleration, and also reduces the interaction between the exhaust pipeline and the supercharger on reliability.

[0038] The exhaust system device and its design method designed in the patent of this invention comprehensively consider the vibration excitation generated by the vehicle engine and the driving road surface during the use of the product, which can effectively avoid the influence of high and low frequency vibrations on product reliability and the interaction between components, ensure that the failure rate of components is maintained at a low normal and reasonable level, and ensure the stability of the exhaust system pipe connection and the durability of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the structural connection of the exhaust system device.

[0040] Figure 2 It is a schematic diagram of the exhaust system structure.

[0041] In the figure, 1 is the hot end air inlet pipe, 2 is the flexible pipe, 3 is the exhaust pipe, 11 is the first bracket, 12 is the second bracket, and 4 is the clamp. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The technical solutions in the embodiments of the present invention are clearly and completely described, and the described embodiments are only embodiments of a part of the present invention, not all of them. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] like Figure 1 , 2As shown, the patent of the present invention designs an embodiment of an exhaust system device. In this embodiment, the exhaust system device includes a hot end intake pipe 1, a flexible pipe 2 and an exhaust pipe 3 connected in sequence. The hot end intake pipe 1 and the flexible pipe 2 are connected and fixed by a clamp 4. The hot end intake pipe 1 is connected to the vehicle engine end through a first bracket 11, and its intake end is connected to the engine supercharger outlet through a clamp. The first bracket 11 is connected to the hot end intake pipe 1 through a two-petal clamp. The clamp is a bolt tightening structure, which can effectively tighten the hot end intake pipe 1 and the first bracket 11 to ensure the stiffness and modal index of the hot end intake pipe 1. The exhaust pipe 3 and the flexible pipe 2 can be connected by a clamp, a sealing gasket structure, or an integrated welding form, which can meet the pipeline diversion use requirements. Among them, the integrated welding form has the advantages of low cost and convenient assembly, and this structure can be preferably used. The exhaust pipe 3 is connected to the frame through a second bracket 31, and the second bracket 31 is located within 300mm behind the flexible pipe 2. First, the second bracket 31 can effectively bear the weight of the exhaust pipe assembly and ensure that the pipe is reasonably supported; second, it can ensure that the flexible pipe 2 works within its design index range to prevent the flexible pipe 2 from breaking or being damaged due to excessive stretching or compression; third, it can improve the mode of the exhaust end pipe to avoid resonance with road excitation. The exhaust end of the exhaust pipe 3 is connected to the exhaust after-processor, which is connected to the frame end of the vehicle through the third bracket.

[0044] When designing the exhaust system device disclosed in the patent of this invention, the main design method is:

[0045] (1) Determine the pipe diameter of the exhaust system according to the engine displacement. The pipe diameter is calculated as follows:

[0046] ΦD≥10V

[0047] Where: ΦD——pipeline diameter, unit is mm;

[0048] V——engine displacement, in L;

[0049] (2) Calculate the required length of the flexible tube according to the pipe diameter, and arrange the flexible tube according to the engine runout. The pipe diameter is between 60mm and 150mm, and the engine runout is the design value, which is within the range of 10mm to 30mm. The flexible tube length must be more than 2.5 times the diameter to achieve a good shock absorption effect. The diameter of the flexible tube is consistent with the hot end intake and exhaust pipes. The formula for calculating the length of the flexible tube is as follows:

[0050] L≥2.5Φd;

[0051] Where: L is the length of the flexible tube, in mm;

[0052] Φd——the diameter of the flexible pipe, in mm;

[0053] (3) Determine the modal frequency of the hot-end intake pipe according to the vibration frequency of the engine. The modal frequency of the hot-end intake pipe needs to avoid the range of the engine excitation frequency. The calculation formula is based on the engine excitation frequency:

[0054] f=nr / 120

[0055] Where: f——engine excitation frequency,

[0056] n——engine rated frequency;

[0057] r——number of engine cylinders;

[0058] The modal frequency of the hot end intake pipe is determined by the highest vibration frequency coefficient k of the engine. The highest excitation frequency coefficient of the engine usually refers to the proportional coefficient between the excitation frequency generated by the engine at the maximum speed and its speed. This coefficient is related to factors such as the structure of the engine, the number of cylinders, and the working cycle. The modal frequency of the hot end intake pipe after supercharging must be greater than or equal to k*f;

[0059] (4) Determine the modal frequency of the exhaust pipe based on the influence of road vibration. The modal frequency of the exhaust pipe needs to be higher than the vibration frequency of the road surface. The modal frequency calculation formula of the exhaust pipe is:

[0060]

[0061] Where: f is the modal frequency of the exhaust pipe,

[0062] k——rigidity of the exhaust pipe,

[0063] m——the mass of the exhaust pipe,

[0064] The frequency of the road surface is related to the structural strength of the vehicle chassis and is obtained on the actual road surface. In general, the road surface excitation frequency is ≤30Hz;

[0065] (5) The design method also includes calculating the airflow pulse frequency. The airflow pulse frequency calculation formula is: airflow pulse frequency = (engine speed × number of cylinders) ÷ 120. By matching flexible pipes with different stiffnesses, when the exhaust throttle valve or exhaust brake butterfly valve intervenes in the operation, the airflow frequency is prevented from resonating with the frequency of the post-processor and accessories, thereby preventing damage.

[0066] (6) The exhaust pipe sealing structure and pipeline connection method shall be determined according to the relevant requirements of relevant automobile emission regulations for the airflow sealing of vehicle exhaust. The sealing gasket of the exhaust sealing structure shall be made of high temperature resistant, high strength, high resilience, long life and pollution-free materials, such as expanded graphite, special alloys coated with high temperature resistant coating, etc. The compression range of the sealing structure shall meet the requirement of 15%-25% of the total thickness. After unloading, the rebound rate shall be greater than the requirement of 5%-10% of the total thickness.

[0067] (7) Design the support structure of the exhaust system device according to the vehicle chassis layout and the external structure of the post-processor. The design should refer to the calculation results of steps (3) and (4). The main function of the support structure is to reliably, effectively and safely fix the exhaust system components to the vehicle chassis and engine, and avoid resonance of the exhaust system components so that the exhaust system can perform at its best. The design process is to determine the hard point coordinates, draw the boundary digital model, perform scheme design, process analysis, CAE analysis, system review, etc. according to the system layout requirements.

[0068] a. Determine the connection method between each bracket and the frame or engine according to the spatial position of the exhaust system bracket, the surrounding boundary conditions, etc.;

[0069] b. It is necessary to consider the accumulated tolerance in the manufacturing process so that each bracket has the ability to eliminate the tolerance, such as designing the mounting hole of the bracket into a long hole;

[0070] c. The mounting holes of a single bracket of the post-processor on the frame beam should be connected by at least two holes. The design requirements for both ends of the exhaust pipe bracket are generally to use two holes for connection and fixing, and a single hole fixing scheme shall not be used;

[0071] d. For exhaust system pipes longer than 1.5m, at least two or more support points should be designed to limit and support the exhaust system pipes in different directions;

[0072] e. Support points must be designed within 0.5m in front and behind the flexible pipe to ensure the correct installation of the flexible pipe;

[0073] f. For front exhaust design, the exhaust pipe must be fixed with a seismic isolation design, using rubber shock-absorbing pads to eliminate vibration transmission between the exhaust pipe and the frame, and eliminate the risk of resonance between the bracket and the chassis;

[0074] g. For upper exhaust design, the pipeline flexible parts must be connected to the rear side of the post-processor, and a fixed bracket must be designed within 0.5m of the pipeline flexible parts to eliminate manufacturing tolerances and isolate vibration;

[0075] h. The bracket design should have the function of preventing wrong installation and leakage. The sheet metal and casting design should be designed in accordance with relevant standards and the sheet metal design principles should be followed. The bracket design must meet the calculation and analysis of strength and fatigue life, and the CAE safety factor should meet the simulation analysis standard requirements.

[0076] After the solidification and development of the technical design scheme is completed, it is necessary to carry out vehicle testing to verify the application reliability of the exhaust system and conduct a pipeline modal test. The specific method is as follows: when the engine is in a static shutdown state, accelerometers are arranged at multiple points. The accelerometers need to be arranged according to engineering experience and in accordance with the principle of being able to reflect the direction and vibration characteristics of the pipeline, and the "hammer method" is used to test the natural modal frequency of the exhaust system pipeline; when the engine is started and idle, it is slowly accelerated to the rated speed point of the engine, and accelerometers are arranged at multiple points on the exhaust system pipeline body to test the pipeline vibration intensity during the slow acceleration process; the pipeline reliability is evaluated through the two dimensions of natural modal frequency and vibration intensity, and the natural vibration frequency of the engine is compared. If it is greater than the natural vibration frequency of the engine, there is no resonance risk; if the index requirements are not met, the exhaust system needs to be adjusted by improving the bracket fixing position, increasing the stiffness, optimizing the overall direction of the pipeline, or increasing the pipeline fixing points, so as to increase the natural frequency of the exhaust system pipeline and meet the modal index requirements.

[0077] The above contents are only preferred embodiments of the present invention and cannot be used to limit the scope of implementation of the present invention. That is, any simple equivalent changes and modifications made according to the claims and description of the present invention are still within the scope of the present invention.

Claims

1. An exhaust system device, characterized in that: The exhaust system device includes a hot end intake pipe, a flexible pipe and an exhaust pipe which are connected in sequence. The hot end intake pipe and the flexible pipe are connected and fixed by a clamp. The hot end intake pipe is connected to the vehicle engine end through a first bracket, and its intake end is butted with the engine supercharger outlet through a clamp. The intake end of the exhaust pipe is welded integrally with the flexible pipe. The exhaust pipe is connected to the vehicle frame through a second bracket, and its outlet end is butted with an exhaust after-processor. The after-processor is connected to the vehicle frame end through a third bracket. The modal frequency of the hot end intake pipe of the exhaust system device is higher than the excitation frequency of the vehicle engine, and the modal frequency of the exhaust pipe is higher than the road vibration frequency generated when the vehicle is running.

2. A method for designing an exhaust system device according to claim 1, characterized in that: The specific steps of the design method are: (1) Determine the pipe diameter of the exhaust system device according to the engine displacement. The pipe diameter is calculated as follows: ΦD≥10V Where: ΦD——pipeline diameter, unit is mm, V——engine displacement, in L; (2) Calculate the required length of the flexible tube according to the pipe diameter, and arrange the flexible tube posture according to the engine runout. The pipe diameter is between 60mm-150mm, and the engine runout is the design value, which is within the range of 10mm-30mm. The length of the flexible tube is more than 2.5 times the diameter to achieve a good shock absorption effect. The diameter of the flexible tube is consistent with the hot end intake and exhaust pipes. The formula for calculating the length of the flexible tube is as follows: L≥2.5Φd; Where: L is the length of the flexible tube, in mm, Φd——the diameter of the flexible pipe, in mm; (3) Determine the modal frequency of the hot-end intake pipe according to the vibration frequency of the engine. The modal frequency of the hot-end intake pipe needs to avoid the range of the engine excitation frequency. The calculation formula is based on the engine excitation frequency: f=nr / 120 Where: f——engine excitation frequency, n——engine rated frequency, r——number of engine cylinders; The modal frequency of the hot end intake pipe is determined by the highest excitation frequency coefficient k of the engine. The modal frequency of the hot end intake pipe after engine supercharging must be greater than or equal to k*f; (4) Determine the modal frequency of the exhaust pipe based on the influence of road vibration. The modal frequency of the exhaust pipe needs to be higher than the excitation frequency of the road surface. The formula for calculating the modal frequency of the exhaust pipe is: Where: f is the modal frequency of the exhaust pipe, k——rigidity of the exhaust pipe, m——the mass of the exhaust pipe, The excitation frequency of the road surface is strongly related to the vehicle chassis structure and is collected on the actual road surface; (5) Determine the exhaust pipe sealing structure and pipe connection method based on the relevant requirements of the exhaust system airflow sealing; (6) Design the exhaust system support structure based on the vehicle chassis layout and the external structure of the post-processor. The design should refer to the calculation results of steps (3) and (4) to avoid resonance between the support structure and the vehicle engine and road vibration.

3. The design method of an exhaust system device according to claim 2, characterized in that: The sealing gasket of the exhaust sealing structure in step (5) is made of expanded graphite or an alloy coated with a high-temperature resistant coating. The compression range of the sealing structure should meet the requirement of 15%-25% of the total thickness. After unloading, the rebound rate should be greater than the requirement of 5%-10% of the total thickness.

4. The design method of an exhaust system device according to claim 2, characterized in that: The design of the support structure in step (6) needs to take into account the accumulated tolerances during the manufacturing process so that each bracket has the ability to eliminate tolerances.

5. The design method of an exhaust system device according to claim 2, characterized in that: In the support structure design of step (6), the mounting holes of a single bracket of the post-processor on the vehicle frame should be connected by at least two holes, and the two ends of the second bracket of the exhaust pipe are required to be connected by two holes.

6. The design method of an exhaust system device according to claim 2, characterized in that: In the support structure design of step (6), for exhaust system pipes longer than 1.5 m, at least two or more support points should be designed to limit and support the exhaust system pipes in different directions.

7. The design method of an exhaust system device according to claim 2, characterized in that: In the support structure design of step (6), support points must be designed within 0.5 m in front and behind the flexible pipe to ensure the correct installation state of the flexible pipe.

8. The method for designing an exhaust system device according to claim 2, characterized in that: In the support structure design of step (6), for the front exhaust design, the fixation of the exhaust pipe must have a seismic isolation design, using rubber shock-absorbing pads to eliminate vibration transmission between the exhaust pipe and the frame, and eliminate the risk of resonance between the bracket and the chassis.

9. The design method of an exhaust system device according to claim 2, characterized in that: In the support structure design of step (6), for the upper exhaust design, a pipeline flexible part must be connected to the rear side of the post-processor, and a fixed bracket must be designed within 0.5m of the pipeline flexible part to eliminate manufacturing tolerances and isolate vibrations.

10. The design method of an exhaust system device according to claim 2, characterized in that: The design method also includes calculating the airflow pulse frequency, and the airflow pulse frequency calculation formula is: frequency = (engine speed × number of cylinders) ÷ 120. By matching flexible tubes with different stiffnesses, when the exhaust throttle valve or exhaust brake butterfly valve intervenes in the work, the airflow frequency is prevented from resonating with the post-processor and accessory frequencies to cause damage.

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