Exhaust system device and method of designing the same

Abstract

The application relates to an exhaust system device and a design method, and belongs to the technical field of heavy truck aftertreatment systems. 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 engine end of a vehicle through a hinged first support, the air inlet end of the hot end air inlet pipe is butted to the outlet of an engine supercharger, the exhaust pipe is connected to the frame through a hinged second support, the air outlet end of the exhaust pipe is butted to an exhaust aftertreatment device, and the aftertreatment device is connected to the frame end of the vehicle through a third support. The exhaust system device is designed based on the engine working excitation frequency and the road surface excitation frequency of the vehicle, resonance between the exhaust system and the engine full speed range excitation frequency and the road surface excitation is avoided, and the reliability and durability of the exhaust system are improved.

Description

Technical Field

[0001] This invention relates to the field of heavy-duty vehicle after-treatment system technology, specifically to an exhaust system device and its design method. Background Technology

[0002] With the deepening implementation of the China VI emission standards for heavy-duty commercial vehicles, the world's most stringent emission regulations for heavy-duty commercial vehicles require after-treatment systems to have a durability of 7 years or 700,000 kilometers, and to meet emission standards throughout the vehicle's entire lifecycle. These stringent standards place higher demands on the reliability, durability, and robustness of after-treatment systems and their components. Most existing automotive exhaust systems are designed with only considerations such as sealing performance, exhaust after-treatment capacity, and vehicle displacement. In practical applications, problems such as loose exhaust pipes and leaks occur, affecting the normal operation of the exhaust system. Therefore, developing a highly efficient, replicable, easily scalable, and highly reliable exhaust system device and method has become an urgent need in the field of after-treatment systems. Summary of the Invention

[0003] To address the problems in the prior art, this invention patent designs an exhaust system device to solve the problem of poor durability of existing automotive exhaust system devices.

[0004] The technical solution adopted in this invention is as follows: 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 fixed together by a clamp. The hot-end intake pipe is connected to the vehicle engine end by a first bracket, and its intake end is connected to the exhaust port of the engine turbocharger by a clamp. The intake end of the exhaust pipe is integrally welded to the flexible pipe. The exhaust pipe is connected to the vehicle frame by a second bracket, and its exhaust end is connected to an exhaust aftertreatment unit. The aftertreatment unit is connected to the vehicle frame end by 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 operation.

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

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

[0007] ΦD≥10V

[0008] In the formula: ΦD——pipe diameter, in mm;

[0009] V – Engine displacement, measured in liters (L);

[0010] (2) Calculate the required flexible tube length based on the pipe diameter, and arrange the flexible tube orientation 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 should be more than 2.5 times the diameter to achieve a good vibration reduction effect. The diameter of the flexible tube should be 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] In the formula: L—the length of the flexible tube, in mm;

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

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

[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 manifold is determined according to the engine's highest excitation frequency coefficient k. After boosting, the modal frequency of the hot-end intake manifold 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 surface 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] In the formula: f—the modal frequency of the exhaust pipe,

[0023] k — Stiffness of the exhaust pipe

[0024] m — the mass of the exhaust pipe

[0025] The road surface excitation frequency is related to the structural strength of the vehicle chassis and is obtained from actual road surface data. Under normal circumstances, the road surface excitation frequency is ≤30Hz.

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

[0027] (6) Design the support structure of the exhaust system device according to the vehicle chassis layout and the external structure of the after-processor. When designing, refer to the calculation results of steps (3) and (4) and avoid resonance between the support structure and the vehicle engine.

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

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

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

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

[0032] Furthermore, in the support structure design of step (6), support points must be designed within a range of 0.5m before and after the flexible tube to ensure the correct installation state of the flexible tube.

[0033] Furthermore, in the support structure design of step (6), for the front exhaust design, the exhaust pipe must be fixed with vibration isolation design, and rubber damping pads are used to eliminate the 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 top exhaust design, a flexible pipe must be connected to the rear side of the after-processor, and a fixed bracket must be designed within 0.5m of the flexible pipe to eliminate manufacturing tolerances and isolate vibration.

[0035] Furthermore, the design method also includes calculating the airflow pulse frequency. 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 is engaged, the airflow frequency is prevented from resonating with the frequency of the after-processor and accessories, which could lead to damage.

[0036] Compared to existing technologies, the advancements of this invention's patented exhaust system device and design method lie in:

[0037] This invention patent presents an exhaust system device and its design method, which for the first time in the industry proposes a method and principle for designing an aftertreatment system based on engine vibration frequency. This improves the reliability and durability of the aftertreatment system piping, and is different from the existing method of evaluating the static strength and fatigue number of components by loading with a certain gravitational acceleration. Furthermore, it reduces the interaction between the exhaust piping and the turbocharger on reliability.

[0038] The exhaust system device and its design method designed by this invention patent comprehensively consider the vibration excitation generated by the vehicle engine and the road surface during product use. It can effectively avoid the impact of high and low frequency vibrations on product reliability and the interaction between components, ensuring that the failure rate of components is maintained at a low and reasonable level, and ensuring the stability of exhaust system pipeline connection and the durability of application. Attached Figure Description

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

[0040] Figure 2 This is a schematic diagram of the exhaust system device.

[0041] In the diagram, 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 Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0043] like Figure 1 , 2As shown, this invention patent 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 by a first bracket 11, and its intake end is connected to the exhaust port of the engine turbocharger by a clamp. The first bracket 11 is connected to the hot-end intake pipe 1 by a two-part clamp. The clamp is a bolt-tightening structure, which can effectively secure the connection between the hot-end intake pipe 1 and the first bracket 11, ensuring the rigidity and modal properties 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 integral welding form, both of which can meet the requirements for pipeline flow guidance. The integral welding form has the advantages of low cost and convenient assembly, and this structure is preferred. The exhaust pipe 3 is connected to the vehicle frame by a second bracket 31, which is located within 300mm behind the flexible pipe 2. First, the second bracket 31 can effectively bear the weight of the exhaust pipe assembly, ensuring that the pipe is properly supported. Second, it can ensure that the flexible pipe 2 operates within its design specifications, preventing excessive stretching or compression that could cause breakage or damage to the flexible pipe 2. Third, it can improve the mode of the exhaust pipe, avoiding resonance with road surface excitation. The exhaust pipe 3's outlet end is connected to an exhaust aftertreatment unit, which is connected to the vehicle's frame end via the third bracket.

[0044] The main design method for the exhaust system device disclosed in this patent is as follows:

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

[0046] ΦD≥10V

[0047] In the formula: ΦD——pipe diameter, in mm;

[0048] V – Engine displacement, measured in liters (L);

[0049] (2) Calculate the required flexible tube length based on the pipe diameter, and arrange the flexible tube orientation 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 should be more than 2.5 times the diameter to achieve a good vibration reduction effect. The diameter of the flexible tube should be 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] In the formula: L—the length of the flexible tube, in mm;

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

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

[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 manifold is determined by the engine's highest vibration frequency coefficient k. The engine's highest excitation frequency coefficient usually refers to the proportionality between the excitation frequency generated by the engine at its maximum speed and its speed. This coefficient is related to factors such as the engine's structure, number of cylinders, and working cycle. After turbocharging, the modal frequency of the hot-end intake manifold 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 surface vibration. The modal frequency of the exhaust pipe needs to be higher than the vibration frequency of the road surface. The formula for calculating the modal frequency of the exhaust pipe is as follows:

[0060]

[0061] In the formula: f—the modal frequency of the exhaust pipe,

[0062] k — Stiffness 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. It is collected on the actual road surface and is generally ≤30Hz.

[0065] (5) The design method also includes calculating the airflow pulse frequency. The formula for calculating the airflow pulse frequency is: airflow pulse frequency = (engine speed × number of cylinders) ÷ 120. By matching flexible tubes with different stiffnesses, when the exhaust throttle valve or exhaust brake butterfly valve is engaged, the airflow frequency is prevented from resonating with the frequency of the after-processor and accessories, which could lead to damage.

[0066] (6) Determine the exhaust pipe sealing structure and pipeline connection method according to the relevant requirements of the vehicle emission regulations for the airflow sealing of the vehicle exhaust; the sealing gasket material of the exhaust sealing structure shall be a material with high temperature resistance, high strength, high resilience, long service life and no pollution, such as expanded graphite, special alloys coated with high temperature resistance coating, etc. The compression range of the sealing structure shall meet 15%-25% of the total thickness; after unloading, the rebound rate shall be greater than 5%-10% of the total thickness.

[0067] (7) Design the support structure of the exhaust system based on the vehicle chassis layout and the external structure of the aftertreatment unit. The design should refer to the calculation results in 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 to prevent resonance in the exhaust system components so that the exhaust system can perform optimally. The design process involves determining the hard point coordinates based on the system layout requirements, drawing the boundary model, designing the scheme, conducting process analysis, CAE analysis, and system review. Specifically,

[0068] a. The connection method between each bracket and the vehicle frame or engine should be determined based on the spatial location of the exhaust system brackets and the surrounding boundary conditions;

[0069] b. It is necessary to consider the cumulative tolerances in the manufacturing process so that each bracket has the ability to eliminate tolerances, such as designing the mounting holes of the brackets as elongated holes, etc.

[0070] c. For the mounting holes of a single bracket on the chassis beam of the aftertreatment system, at least two holes should be used for connection. The design requirements for both ends of the exhaust pipe bracket are generally to use two holes for connection and fixation, and a single hole fixation scheme shall not be used.

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

[0072] e. Support points must be designed within 0.5m before and after the flexible tube to ensure the correct installation of the flexible tube;

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

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

[0075] h. The bracket design should have the functions of preventing incorrect assembly and preventing missing assembly; the design of sheet metal parts and castings should be carried out in accordance with relevant standards, and should also follow the design principles of sheet metal parts. The bracket design should meet the calculation and analysis of strength and fatigue life, and the CAE safety factor should meet the requirements of simulation analysis standards.

[0076] After the technical design scheme is finalized and developed, vehicle testing is required to verify the reliability of the exhaust system and conduct pipeline modal testing. The specific methods are as follows: With the engine in a static, stopped state, multiple acceleration sensors are placed. These sensors should be arranged according to engineering experience, based on the principle of reflecting the pipeline routing and vibration characteristics. The "hammering method" is used to test the natural modal frequencies of the exhaust system pipeline. With the engine running at idle, the system is slowly accelerated to its rated speed. Multiple acceleration sensors are placed on the exhaust system pipeline body to test the pipeline vibration intensity during this slow acceleration process. The pipeline reliability is evaluated using both natural modal frequencies and vibration intensity. The natural modal frequencies are compared to the engine's natural vibration frequency. If the natural frequency is greater than the engine's natural vibration frequency, there is no risk of resonance. If the requirements are not met, adjustments to the exhaust system are needed, such as improving the bracket fixing position, increasing rigidity, optimizing the overall pipeline routing, or adding pipeline fixing points, to improve the natural frequency of the exhaust system pipeline and meet the modal performance requirements.

[0077] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the present invention shall still fall within the scope of the present invention.

Claims

1. A method of designing an exhaust system arrangement, characterized by, 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 fixed together by a clamp. The hot-end intake pipe is connected to the vehicle engine end by a first bracket, and its intake end is connected to the engine turbocharger outlet by a clamp. The intake end of the exhaust pipe is integrally welded to the flexible pipe. The exhaust pipe is connected to the vehicle frame by a second bracket, and its exhaust end is connected to an exhaust aftertreatment unit. The aftertreatment unit is connected to the vehicle frame end by 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 operation. The specific steps of the design method are as follows: (1) Determine the pipe diameter of the exhaust system device based on the engine displacement. The pipe diameter is calculated as follows: ΦD≥10V; Where: ΦD——pipe diameter, in mm; V——engine displacement, in L; (2) Calculate the required flexible tube length based on the pipe diameter, and arrange the flexible tube orientation 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 should be more than 2.5 times the diameter to achieve a good vibration reduction effect. The diameter of the flexible tube should be consistent with the hot end intake and exhaust pipes. The formula for calculating the length of the flexible tube is as follows: L≥2.5 Φd; Where: L—length of the flexible tube, in mm; Φd—diameter of the flexible tube, in mm; (3) Determine the modal frequency of the hot-end intake pipe based on the engine's vibration frequency. The modal frequency of the hot-end intake pipe needs to avoid the range of the engine's excitation frequency. The engine excitation frequency is calculated using the following formula: 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, and the modal frequency of the hot end intake pipe after the engine is supercharged must be greater than or equal to k f; (4) Determine the modal frequency of the exhaust pipe based on the influence of road surface 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: ； In the formula: f—modal frequency of the exhaust pipe, k—stiffness of the exhaust pipe, m—mass of the exhaust pipe. The excitation frequency of the road surface is strongly correlated with the overall vehicle chassis structure and is obtained from actual road surface data. (5) Determine the exhaust pipe sealing structure and pipeline connection method according to the relevant requirements for airflow sealing of the exhaust system; (6) Design the support structure of the exhaust system device according to the vehicle chassis layout and the external structure of the after-processor. When designing, refer to the calculation results of steps (3) and (4) and avoid resonance between the support structure and the vehicle engine and road vibration.

2. A method of designing an exhaust system arrangement according to claim 1, characterized in that In step (5), the sealing gasket of the exhaust sealing structure 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 5%-10% of the total thickness.

3. A method of designing an exhaust system arrangement according to claim 1, characterized in that The design of the support structure in step (6) needs to take into account the cumulative tolerances in the manufacturing process so that each bracket has the ability to eliminate tolerances.

4. A method of designing an exhaust system arrangement according to claim 1, characterized in that In the support structure design of step (6), the mounting holes of a single bracket of the after-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 should be connected by two holes.

5. A method of designing an exhaust system arrangement according to claim 1, characterized in that In the support structure design of step (6), for exhaust system pipelines longer than 1.5m, at least two or more support points should be designed to limit and support the exhaust system pipeline in different directions.

6. A method of designing an exhaust system arrangement according to claim 1, characterized in that In the support structure design of step (6), support points must be designed within a range of 0.5m before and after the flexible tube to ensure the correct installation state of the flexible tube.

7. A method of designing an exhaust system arrangement according to claim 1, characterized in that In the support structure design of step (6), for the front exhaust design, the exhaust pipe must be fixed with vibration isolation design, and rubber damping pads are used to eliminate the vibration transmission between the exhaust pipe and the frame, and eliminate the risk of resonance between the bracket and the chassis.

8. A method of designing an exhaust system arrangement according to claim 1, characterized in that In the support structure design of step (6), for the top exhaust design, a flexible pipe must be connected to the rear side of the post-processor, and a fixed bracket must be designed within 0.5m of the flexible pipe to eliminate manufacturing tolerances and isolate vibration.

9. A method of designing an exhaust system arrangement according to claim 1, characterized in that The design method also includes calculating the airflow pulse frequency. The formula for calculating the airflow pulse frequency 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 is engaged, the airflow frequency is prevented from resonating with the frequency of the after-processor and accessories, which could lead to damage.

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