A method of arranging an EGR pipe joint
By constructing a three-dimensional model of the intake manifold and optimizing the arrangement of the EGR pipe joints, the problem of poor EGR uniformity in the intake manifold was solved, thereby improving the combustion stability and performance of the engine, shortening the development cycle, and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DONGFENG MOTOR GRP
- Filing Date
- 2023-11-08
- Publication Date
- 2026-07-31
AI Technical Summary
In compact and lightweight gasoline engines, it is difficult to determine the optimal location for the intake manifold EGR connector, resulting in poor EGR uniformity, which affects combustion stability, power performance, economic performance and emission performance. Moreover, existing methods require long-term thermodynamic development bench tests.
By constructing a three-dimensional model of the intake manifold, the flow performance indicators are determined, the positions of the intake manifold and branch pipes are adjusted, the EGR pipe joints are arranged based on the EGR operating parameters, the EGR uniformity index is optimized, and the tilt angle, insertion depth and opening deflection angle of the EGR pipe joints are adjusted to ensure that the relative deviation of the EGR rate is within ±5%.
It achieves good uniformity of the intake manifold EGR system, ensuring combustion stability and engine power, economy and emissions performance, while shortening the development cycle and saving costs.
Smart Images
Figure CN117536746B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of automotive exhaust gas recirculation technology, specifically to a method for arranging EGR pipe connectors. Background Technology
[0002] Hybrid-specific engines focus on improving engine thermal efficiency and reducing fuel consumption. Exhaust Gas Recirculation (EGR) technology introduces a certain amount of exhaust gas into the intake manifold under partial load conditions. This requires a corresponding increase in throttle opening to meet the demand for fresh air under these conditions, effectively reducing engine pumping losses. Furthermore, the inert gases in the EGR exhaust gas do not participate in in-cylinder combustion, effectively diluting the oxygen concentration in the combustible mixture within the combustion chamber. This slows down combustion, lowers combustion temperature, and effectively reduces NOx emissions. Therefore, EGR technology is the mainstream technique for reducing fuel consumption in hybrid-specific engines.
[0003] To meet market demands and stringent emission regulations, compactness and lightweight design are the mainstream development direction for gasoline engines. However, this presents greater technical challenges in ensuring the uniformity of EGR in the intake manifold. This is mainly because the miniaturization of the intake manifold, with its shorter main pipe and branch pipes for each cylinder, makes it difficult to determine the optimal location for the EGR pipe connectors. This results in a smaller fuel-air mixing space and shorter mixing time, leading to poor EGR uniformity across cylinders. This directly affects combustion stability, engine power performance, fuel economy, and emissions performance.
[0004] During the engine concept design and development phase, obtaining the EGR uniformity of the intake manifold EGR system through thermodynamic development bench tests is a lengthy process that requires testing resources and costs. Summary of the Invention
[0005] The purpose of this application is to provide a method for arranging EGR pipe joints to obtain the optimal arrangement scheme of EGR pipe joints, so that the intake manifold EGR system has good EGR uniformity, thereby ensuring combustion stability and ensuring that the engine has good power performance, economic performance and emission performance.
[0006] To achieve the above objectives, this application provides a method for arranging EGR pipe fittings, comprising:
[0007] Based on the pre-constructed three-dimensional model of the intake manifold, the gas flow performance indicators in the intake manifold corresponding to the engine's operating conditions are determined.
[0008] If the flow performance indicators do not meet the preset requirements, the position of the intake manifold and / or the position of the intake manifold branch pipes shall be adjusted.
[0009] Based on the EGR operating parameters, EGR pipe joints are arranged according to preset position parameters to construct a three-dimensional model of the intake manifold EGR system. The intake manifold EGR system includes the intake manifold, EGR pipeline, and EGR pipe joints connecting the intake manifold and EGR pipeline.
[0010] Based on the three-dimensional model of the intake manifold EGR system, the EGR uniformity index of the intake manifold EGR system is determined. Based on the EGR uniformity index, the preset position parameters are adjusted, thereby adjusting the arrangement of the EGR pipe joints.
[0011] In some embodiments of this application, based on the aforementioned scheme, the flow performance indicators include the deviation of the mass flow coefficient of the gas in each branch of the intake manifold and the mass flow non-uniformity of the intake manifold.
[0012] In some embodiments of this application, based on the aforementioned scheme and according to a pre-constructed three-dimensional model of the intake manifold, the gas flow performance indicators within the intake manifold corresponding to the engine's operating conditions are determined, including:
[0013] Based on the three-dimensional model of the intake manifold and the first preset correlation, the deviation of the mass flow coefficient of the gas in each branch of the intake manifold corresponding to the engine's operating conditions is determined.
[0014] The first pre-defined association relationship is:
[0015]
[0016] in,
[0017]
[0018]
[0019] M th_i =c th_i ·ρ th_i ·A i
[0020]
[0021]
[0022] Δp i =p u -p m_i
[0023] In the formula, M represents the deviation of the mass flow coefficient of the gas in the i-th branch of the intake manifold; th_i c is the theoretical mass flow rate at the outlet of the i-th branch of the intake manifold; th_iρ is the theoretical gas velocity at the outlet of the i-th branch of the intake manifold. th_i A is the theoretical gas density at the outlet of the i-th branch of the intake manifold; i The cross-sectional area of the outlet of the i-th branch pipe of the intake manifold; k is the adiabatic index; R is the ideal gas constant; p u For environmental pressure; T u ambient temperature; p m_i is the outlet pressure of the i-th branch of the intake manifold; n is the number of branches of the intake manifold; Mi is the actual mass flow rate at the outlet of the i-th branch of the intake manifold. is the mass flow rate coefficient of the gas in the i-th branch of the intake manifold; It is the average mass flow coefficient of the gas in all branches of the intake manifold.
[0024] In some embodiments of this application, based on the aforementioned scheme and according to a pre-constructed three-dimensional model of the intake manifold, the gas flow performance indicators within the intake manifold corresponding to the engine's operating conditions are determined, including:
[0025] Based on the three-dimensional model of the intake manifold and the second preset correlation, the mass flow non-uniformity of the intake manifold corresponding to the engine's operating conditions is determined.
[0026] The second pre-defined association relationship is:
[0027]
[0028] in,
[0029]
[0030] In the formula, M i MAX(M) represents the actual mass flow rate at the outlet of the i-th branch of the intake manifold; n represents the number of branches in the intake manifold; i ) is the maximum actual mass flow rate at all branch outlets of the intake manifold; MIN(M i () represents the minimum actual mass flow rate among all branch outlets of the intake manifold; This is the average mass flow rate at all branch outlets of the intake manifold.
[0031] In some embodiments of this application, based on the foregoing scheme, the preset requirements include: under the operating conditions of the engine, the deviation of the mass flow coefficient of the gas in each branch of the intake manifold is less than or equal to ±2.5%, and the mass flow non-uniformity of the intake manifold is less than or equal to ±5%.
[0032] In some embodiments of this application, based on the foregoing scheme, the position of the intake manifold and / or the position of the intake manifold branch pipes are adjusted, including:
[0033] If the actual mass flow rate at the outlet of one of the intake manifold branches is too low, increase the transition radius between that branch and the pressure regulating chamber; if the actual mass flow rate at the outlet of one of the intake manifold branches is too high, decrease the transition radius between that branch and the pressure regulating chamber.
[0034] In some embodiments of this application, based on the foregoing scheme, the position of the intake manifold and / or the position of the intake manifold branch pipes are adjusted, including:
[0035] If, under engine operating conditions, the mass flow coefficient deviation of the gas in each branch pipe of the intake manifold is greater than ±2.5%, and the mass flow non-uniformity of the intake manifold is greater than ±5%, then, based on the gas flow pressure distribution cloud map of the intake manifold, the angle between the central axis of the intake inlet of the intake manifold and the horizontal direction is adjusted.
[0036] In some embodiments of this application, based on the aforementioned scheme, the portion of the EGR pipe connector inserted into the intake manifold has openings on both the intake and exhaust sides. The preset position parameters include: the tilt angle of the EGR pipe connector, the insertion depth of the EGR pipe connector, and the deflection angle of the opening of the EGR pipe connector. The tilt angle of the EGR pipe connector is the angle between the central axis of the EGR pipe connector and the horizontal direction, and the deflection angle of the opening of the EGR pipe connector is the angle between the central axis of the EGR pipe connector and the central axis of the opening.
[0037] In some embodiments of this application, based on the aforementioned scheme, the EGR uniformity index includes the EGR rate and the relative deviation of the EGR rate.
[0038] Adjust the preset position parameters according to the EGR uniformity index, including:
[0039] Adjust the tilt angle of the EGR pipe fitting, the insertion depth of the EGR pipe fitting, and the deflection angle of the opening of the EGR pipe fitting so that the relative deviation of the EGR rate is less than or equal to ±5%.
[0040] In some embodiments of this application, based on the aforementioned scheme, the engine's operating conditions include idling, partial load, and external characteristic conditions, and the EGR operating parameter conditions include minimum specific fuel consumption and maximum EGR rate conditions.
[0041] The technical solution of this application provides a method for arranging EGR pipe joints, including: determining the gas flow performance index in the intake manifold corresponding to the engine's operating conditions based on a pre-constructed three-dimensional model of the intake manifold; adjusting the position of the intake manifold and / or the position of the branch pipes of the intake manifold if the flow performance index does not meet the preset requirements; arranging the EGR pipe joints according to preset position parameters based on the EGR operating parameters, constructing a three-dimensional model of the intake manifold EGR system, the intake manifold EGR system including the intake manifold, EGR pipeline, and EGR pipe joints connecting the intake manifold and the EGR pipeline; determining the EGR uniformity index of the intake manifold EGR system based on the three-dimensional model of the intake manifold EGR system, adjusting the preset position parameters according to the EGR uniformity index, thereby adjusting the arrangement of the EGR pipe joints to obtain the optimal arrangement scheme of the EGR pipe joints, so that the intake manifold EGR system has good EGR uniformity, thereby ensuring combustion stability and ensuring that the engine has good power performance, economic performance, and emission performance. At the same time, it saves costs, improves development efficiency, significantly shortens product development cycle, and clarifies the design optimization direction for intake manifold and EGR pipeline layout. Attached Figure Description
[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:
[0043] Figure 1 This is a flowchart illustrating the arrangement method of the EGR pipe fittings in this application;
[0044] Figure 2 This is a three-dimensional structural diagram of the intake manifold of this application;
[0045] Figure 3 This is a schematic diagram of the planar structure of the intake manifold of this application;
[0046] Figure 4 This is a schematic cross-sectional view of the intake manifold from the timing end to the flywheel end in this application;
[0047] Figure 5 This is a three-dimensional structural diagram of the intake manifold from another angle of this application;
[0048] Figure 6 This is a schematic diagram of the arrangement structure of the EGR pipe joints in the overall assembly of this application;
[0049] Figure 7 This is a schematic cross-sectional view of the EGR pipe fitting of this application;
[0050] Figure 8 This is a cross-sectional schematic diagram of the EGR pipe fitting of this application from another angle. Detailed Implementation
[0051] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0052] The following detailed description of some embodiments of this application will be provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0053] The intake manifold is a crucial component of the engine's intake system. It distributes the air-fuel mixture or clean air as evenly as possible to the intake passages of each cylinder. The flow performance of the intake manifold directly affects the intake airflow and uniformity, thus influencing the engine's power and fuel economy. Furthermore, as a key engine component, the intake manifold is the passageway for introducing the EGR (Exhaust Gas Refrigerant) system, directly affecting EGR uniformity, which in turn affects combustion stability, and consequently, the engine's power, fuel economy, and emissions performance. Therefore, during engine design and development, strict evaluation standards are applied to the fresh air intake uniformity of the intake manifold to ensure good flow performance. This application uses two indicators—the deviation of the mass flow coefficient of the gas in each branch pipe of the intake manifold and the mass flow non-uniformity—to evaluate the flow performance of the intake manifold.
[0054] The speed of sound in air is approximately 340 m / s (approximately 1224 km / h). The maximum speed reached by cars (including racing cars) on the road is less than one-third of the speed of sound. Therefore, the flow field problem of a car engine falls under the category of low-speed aerodynamics. Gas density is related to pressure and thermal processes, and its compressibility cannot be ignored; it is called a compressible fluid. Considering the relative motion and interaction forces between moving fluid molecules, it is called a viscous fluid. Considering the compressibility, viscosity, and thermal conductivity of a fluid, it is called a real fluid. Therefore, this application considers the fluid in the intake manifold to be a real fluid with compressibility, viscosity, and thermal conductivity, which better reflects the actual working state of an engine intake manifold.
[0055] During the intake process, fresh air enters the intake manifold. As the throttle valve body opens and the degree of valve opening changes, the vacuum and internal volume of the intake manifold change, and the direction, velocity, and flow pattern of the gas flow change. Collisions of fluid particles and vortices generated in the fluid form a turbulent and irregular flow field. It can be seen that the air movement in the intake manifold is a very complex compressible, viscous, and turbulent motion. Therefore, the intake pressure at the intake manifold inlet is fluctuating and unstable. After the buffering and stabilizing effects of the intake manifold pressure stabilizing chamber and each branch pipe, the airflow at the outlet of each branch pipe tends to be stable. Therefore, this application selects the gas flow parameters at the outlet of each branch pipe of the intake manifold, including outlet pressure, gas velocity, density, etc., to calculate the mass flow rate of the gas in each branch pipe, thereby improving the accuracy of the intake manifold flow performance evaluation index.
[0056] Please see Figure 1 This application provides a method for arranging EGR pipe fittings, including:
[0057] Step S1: Based on the pre-constructed three-dimensional model of the intake manifold, determine the gas flow performance indicators in the intake manifold corresponding to the engine's operating conditions.
[0058] Specifically, the method for constructing a three-dimensional model of the intake manifold may include: obtaining the geometric parameters of the intake manifold, and constructing a three-dimensional model of the intake manifold based on experimental methods and the geometric parameters of the intake manifold.
[0059] In some embodiments, the engine operating conditions include idling, partial load, and external characteristic conditions. Since the throttle opening is closely related to the engine operating conditions, the throttle opening can be 0-10% under idling conditions; 30-60%, for example 50%, under partial load conditions; and 100%, i.e., the throttle is fully open, under external characteristic conditions.
[0060] In some embodiments, the gas flow performance indicators within the intake manifold include the deviation of the mass flow coefficient of the gas in each branch pipe of the intake manifold and the mass flow non-uniformity of the intake manifold. By calculating the mass flow rate of the gas in each branch pipe of the intake manifold under different engine operating conditions, the deviation of the mass flow coefficient of the gas in each branch pipe and the mass flow non-uniformity of the intake manifold are further calculated based on the mass flow rate of the gas in each branch pipe, thereby reflecting the flow performance of the intake manifold.
[0061] In some embodiments, based on a pre-constructed three-dimensional model of the intake manifold, the flow performance indicators of the gas within the intake manifold corresponding to the engine's operating conditions are determined, including:
[0062] Based on the pre-built three-dimensional model of the intake manifold and the first preset correlation, the deviation of the mass flow coefficient of the gas in each branch of the intake manifold corresponding to the engine's operating conditions is determined; based on the pre-built three-dimensional model of the intake manifold and the second preset correlation, the mass flow non-uniformity of the intake manifold corresponding to the engine's operating conditions is determined.
[0063] The first pre-defined association relationship is:
[0064]
[0065] The second pre-defined association relationship is:
[0066]
[0067] in,
[0068]
[0069]
[0070] M th_i =c th_i ·ρ th_i ·A i
[0071]
[0072]
[0073] Δp i =p u -p m_i
[0074]
[0075] In the formula, ε is the mass flow coefficient deviation of the gas in the i-th branch of the intake manifold; M is the mass flow non-uniformity of the intake manifold; th_i c is the theoretical mass flow rate at the outlet of the i-th branch of the intake manifold; th_i ρ is the theoretical gas velocity at the outlet of the i-th branch of the intake manifold. th_i A is the theoretical gas density at the outlet of the i-th branch of the intake manifold; i The cross-sectional area of the outlet of the i-th branch pipe of the intake manifold; k is the adiabatic index; R is the ideal gas constant; p u For environmental pressure; T u ambient temperature; p m_i Let be the outlet pressure of the i-th branch of the intake manifold; n be the number of branches in the intake manifold; M iThis represents the actual mass flow rate at the outlet of the i-th branch pipe of the intake manifold. is the mass flow rate coefficient of the gas in the i-th branch of the intake manifold; MAX(M) represents the average mass flow coefficient of the gas in all branches of the intake manifold. i ) is the maximum actual mass flow rate at all branch outlets of the intake manifold; MIN(M i () represents the minimum actual mass flow rate among all branch outlets of the intake manifold; This is the average mass flow rate at all branch outlets of the intake manifold.
[0076] Among them, the adiabatic index k, the ideal gas constant R, and the ambient pressure p u Ambient temperature T u The number of branches n in the intake manifold are preset boundary conditions, and the remaining parameters can be obtained through simulation software based on the three-dimensional model of the intake manifold.
[0077] Step S2: If the flow performance indicators do not meet the preset requirements, adjust the position of the intake manifold and / or the position of the intake manifold branch pipes.
[0078] To ensure good flow performance in the intake manifold, the preset requirements include: the deviation of the mass flow coefficient of the gas in each branch of the intake manifold under different engine operating conditions. Less than or equal to ±2.5%, and the mass flow rate non-uniformity ε of the intake manifold is less than or equal to ±5%.
[0079] In some embodiments, adjusting the position of the intake manifold and / or the position of the intake manifold branch pipes includes:
[0080] like Figure 2 As shown, if the actual mass flow rate of one of the branch outlets 2 of the intake manifold 1 is too small, the transition radius R1 between the branch 3 and the pressure regulating chamber 4 is increased, thereby increasing its flow area; if the actual mass flow rate of one of the branch outlets 2 of the intake manifold 1 is too large, the transition radius R1 between the branch 3 and the pressure regulating chamber 4 is decreased, thereby decreasing its flow area. This optimization method uses local optimization, requires minimal structural changes to the intake manifold, is simple and quick to implement, and does not increase the overall machine cost or require changes to the overall machine layout.
[0081] Secondly, other local optimization methods can also be used, such as... Figure 3 As shown, if the actual mass flow rate of one of the branch outlets 2 of the intake manifold 1 is too small, the bending radius R2 and R3 of the branch 3 will be increased, thereby changing the bending direction of the branch 3; if the actual mass flow rate of one of the branch outlets 2 of the intake manifold 1 is too large, the bending radius R2 and R3 of the branch 3 will be decreased.
[0082] In some embodiments, adjusting the position of the intake manifold and / or the position of the intake manifold branch pipes includes:
[0083] If, under the operating conditions of the engine, the overall intake uniformity of the intake manifold is poor (i.e., the mass flow coefficient deviation of the gas in each branch of the intake manifold is greater than ±2.5%, and the mass flow non-uniformity of the intake manifold is greater than ±5%), and the effect of local optimization methods is not ideal, then based on the gas flow pressure distribution cloud map of the intake manifold, as follows... Figure 4 As shown, adjust the angle β between the central axis 10 of the intake manifold and the horizontal direction 20. By adopting the overall optimization method, analyze the gas flow pressure distribution cloud map of the intake manifold, evaluate the pressure loss of the intake manifold, and adjust the intake direction, that is, the angle β between the central axis 10 of the intake manifold and the horizontal direction 20.
[0084] Step S3: Based on the EGR operating parameters, arrange the EGR pipe joints according to the preset position parameters to construct a three-dimensional model of the intake manifold EGR system. The intake manifold EGR system includes the intake manifold, EGR pipeline, and EGR pipe joints connecting the intake manifold and EGR pipeline.
[0085] In some embodiments, the EGR operating parameters include the minimum specific fuel consumption condition and the maximum EGR rate condition.
[0086] Specifically, the lowest specific fuel consumption condition and the maximum EGR rate condition can be selected under partial load conditions as typical EGR operating parameter conditions for evaluating EGR uniformity.
[0087] For a certain hybrid-specific gasoline engine, the parameters under different operating conditions are as follows:
[0088] Lowest specific fuel consumption conditions: engine speed 2500 rpm, engine pressure 9.08 bar, engine torque 108.17 Nm;
[0089] Maximum EGR rate operating conditions: engine speed 3500 rpm, engine pressure 8.66 bar, engine torque 94.8 Nm.
[0090] like Figure 5As shown, based on the requirements of the engine layout and considering the engine compartment layout boundary, a relatively flat area is selected at the intake manifold 5 behind the throttle valve as the possible installation area for the EGR pipe connector 6. At the same time, to avoid EGR condensation problems, the EGR pipe connector 6 needs to be tilted upwards. Combining spatial layout and process feasibility, the EGR pipe connector 6 is installed on a small plane farthest from the throttle valve within the possible installation area. This is mainly because the installation position of the EGR pipe connector 6 is far from the throttle valve, which can extend the gas transmission path and facilitate the full mixing of fresh air and EGR exhaust gas, thereby improving EGR uniformity.
[0091] If the portion of the EGR pipe connector inserted into the intake manifold is too short, the EGR exhaust gas will be carried away by the fresh air flow before it is fully mixed with the fresh air. If the portion of the EGR pipe connector inserted into the intake manifold is too long, the EGR exhaust gas is prone to interfering with the fresh air, resulting in airflow collisions and other issues that affect the mixing effect. Therefore, the required insertion depth L of the EGR pipe connector is as follows:
[0092]
[0093] In the formula, H is the maximum vertical distance of the intake manifold section cavity corresponding to the coaxial section of the EGR pipe connector, and D is the radius of the cavity at the intake inlet.
[0094] like Figure 6 As shown, the tilt angle ψ of EGR pipe connector 6 is the angle between the central axis 30° of the EGR pipe connector and the horizontal direction 20°. If condensation occurs in the EGR system, it will result in water vapor in the EGR gas. This water vapor tends to accumulate at the low point of the intake manifold. Under vehicle acceleration conditions, this condensate will enter the engine intake manifold and then the combustion chamber, causing misfire and fuel failure. Furthermore, in low-temperature environments, condensate buildup can cause freezing, leading to internal structural cracking and affecting engine reliability and lifespan. Therefore, to avoid the aforementioned EGR condensation problem, EGR pipe connector 6 must be tilted upwards. The required tilt angle ψ of EGR pipe connector 6 is as follows:
[0095] 15°≤ψ≤90°
[0096] This application follows the principle of constant flow area. The intake manifold is made using injection molding, and the EGR pipe connector is specially structured. The processing mold is extracted in the vertical direction. Considering the ease of processing, process feasibility, and cost, a square hole is opened on each of the EGR pipe connectors along the intake and exhaust sides, and the two square holes are exactly the same in size and shape. The hole structure is used to divert and guide the EGR exhaust gas, so that the fresh air and EGR exhaust gas are mixed more fully, and the uniformity of EGR is improved.
[0097] Assuming the inner diameter of the EGR pipe fitting is d, and following the conventional EGR intake method, the flow area S of the EGR gas can be expressed as:
[0098]
[0099] The part of the EGR pipe connector that inserts into the intake manifold has openings on both the intake and exhaust sides. These openings are square holes, and the two square holes are exactly the same size and shape. The preset position parameters include the tilt angle ψ of the EGR pipe connector, the insertion depth L of the EGR pipe connector, and the deflection angle θ of the opening of the EGR pipe connector.
[0100] like Figure 7 and Figure 8 As shown, the dimensions of the square hole on the EGR pipe fitting are as follows:
[0101]
[0102] l1=l2=γL
[0103]
[0104] In the formula, γ is an empirical coefficient, which is generally required to be... l1 is the length of the square hole on the intake side, l2 is the length of the square hole on the exhaust side, h1 is the width of the square hole on the intake side, h2 is the width of the square hole on the exhaust side, S1 is the area of the square hole on the intake side, and S2 is the area of the square hole on the exhaust side.
[0105] The deflection angle θ of the EGR pipe fitting opening is the angle between the EGR pipe fitting center axis 30° and the opening center axis 40°. The values of the deflection angle θ are as follows:
[0106] 15°≤θ≤45°
[0107] Assuming the deflection angle of the square orifice on the intake side is positive when rotating clockwise from the timing end to the flywheel end, and negative when rotating counterclockwise from the timing end to the flywheel end, and the deflection angle of the square orifice on the exhaust side is positive when rotating clockwise from the flywheel end to the timing end, and negative when rotating counterclockwise from the flywheel end to the timing end, then the opening scheme for the EGR pipe connector is as follows:
[0108] Table 1. Hole Opening Scheme for EGR Pipe Fittings
[0109]
[0110] In Table 1, θ1 is the deflection angle of the square hole on the intake side of the EGR pipe connector, and θ2 is the deflection angle of the square hole on the exhaust side of the EGR pipe connector.
[0111] The single-variable method, using permutations and combinations, is employed to determine the opening scheme:
[0112] Based on scheme 1, the set of opening schemes includes:
[0113] Set 1: Schemes 1, 2, and 3; Schemes 1, 2, and 4; Schemes 1, 3, and 5; Schemes 1, 4, and 5; Schemes 1, 6, and 7; Schemes 1, 6, and 8; Schemes 1, 7, and 9; Schemes 1, 8, and 9. The deflection direction and angle of the holes on one side are the same. The influence of the hole deflection direction on the uniformity of EGR is compared and analyzed.
[0114] Set 2: Combinations 1, 2, 10; 1, 3, 11; 1, 4, 12; 1, 5, 13; Combinations 1, 6, 14; Combinations 1, 7, 15; Combinations 1, 8, 16; Combinations 1, 9, 17. One side of the hole has the same deflection direction and angle, and the other side of the hole has the same deflection direction. Compare and analyze the influence of the deflection angle of the other side of the hole on the EGR uniformity.
[0115] Set 3: Combinations 1, 2, and 6; Combinations 1, 3, and 7; Combinations 1, 4, and 8; Combinations 1, 5, and 9. Both holes are deflected in the same direction and at the same angle. The influence of the deflection angle on the uniformity of EGR is compared and analyzed.
[0116] Set 4: Combinations 1, 2, 11; 1, 3, 10; 1, 4, 13; 1, 5, 12; Combinations 1, 6, 15; Combinations 1, 7, 14; Combinations 1, 8, 17; Combinations 1, 9, 16. One side of the hole has the same deflection direction and angle, while the other side has a different deflection direction. The influence of the deflection direction and angle of the other side on the EGR uniformity is compared and analyzed.
[0117] Step S4: Based on the three-dimensional model of the intake manifold EGR system, determine the EGR uniformity index of the intake manifold EGR system, and adjust the preset position parameters according to the EGR uniformity index, thereby adjusting the arrangement of the EGR pipe joints.
[0118] Specifically, EGR uniformity indicators include EGR rate and EGR rate relative deviation.
[0119] EGR rate is a percentage used to measure the mass of exhaust gas in each cylinder, and the calculation formula is:
[0120]
[0121] In the formula, E i m is the EGR rate of the i-th cylinder; EGRThe mass of EGR exhaust gas in the cylinder after the intake valve is closed; m air This refers to the mass of air in the cylinder after the intake valve is closed.
[0122] The relative deviation of EGR rate is used to measure the uniformity of EGR across cylinders. The calculation formula is as follows:
[0123]
[0124]
[0125] In the formula, The average EGR rate of the intake manifold; Let be the relative deviation of the EGR rate of the i-th cylinder, and n be the number of cylinders.
[0126] To ensure combustion stability, EGR uniformity must meet the requirement that the relative deviation of the EGR rate be ≤ ±5%. Considering processability and cost, the number and shape of the openings on the EGR pipe fitting remain unchanged. The main optimization directions are the tilt angle, insertion depth, opening direction, and deflection angle of the EGR pipe fitting. Therefore, if the relative deviation of the EGR rate in each cylinder does not meet the target limit, based on the corresponding changes obtained from the analysis of the opening direction and deflection angle in the set of opening schemes, a mathematical optimization method is used to adjust the tilt angle ψ, insertion depth L, and deflection angle θ of the EGR pipe fitting. This optimization process is repeated to obtain the optimal arrangement of the EGR pipe fitting. Based on this, in some embodiments, preset position parameters are adjusted according to the EGR uniformity index, including:
[0127] Adjust the tilt angle ψ of the EGR pipe fitting, the insertion depth L of the EGR pipe fitting, and the deflection angle θ of the opening of the EGR pipe fitting so that the relative deviation of the EGR rate is less than or equal to ±5%.
[0128] In summary, this application provides a method for arranging EGR pipe joints during the engine concept design and development stage, optimizing the arrangement of the intake manifold EGR system with a main intake method, and possessing the following characteristics:
[0129] 1. The use of an EGR pipe connector inserted into the intake manifold (referred to as insert-type EGR) solves the problems of limited space, restricted cabin layout space, and interference.
[0130] 2. Analyze the flow state of fresh air in the intake manifold, select the gas flow parameters of each branch outlet of the intake manifold, calculate the mass flow non-uniformity and mass flow coefficient deviation of each branch under different engine operating conditions, and propose a rapid optimization method based on the corresponding evaluation indicators to ensure good flow performance of the intake manifold.
[0131] 3. To ensure that the fresh air in the intake manifold meets the performance development goals, and based on this, insert-type EGR systems are arranged in areas where EGR pipe fittings may be installed. Multiple orifice schemes are defined, typical EGR operating parameter points are selected, and the EGR rate and its relative deviation for each cylinder are statistically analyzed. Based on the performance development goals, the optimal installation location and orifice scheme for the insert-type EGR system are comprehensively evaluated and selected. This application achieves the optimal arrangement of EGR pipe fittings, ensuring good EGR uniformity in the intake manifold EGR system, thereby guaranteeing combustion stability and ensuring good engine power, fuel economy, and emissions performance. Simultaneously, it saves costs, improves development efficiency, significantly shortens the product development cycle, and clarifies the design optimization direction for the intake manifold and EGR pipeline layout.
[0132] Other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. It should be understood that this application is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.
Claims
1. A method of arranging an exhaust gas recirculation pipe joint, characterized in that include: Based on the pre-constructed three-dimensional model of the intake manifold, the gas flow performance indicators in the intake manifold corresponding to the engine's operating conditions are determined. If the flow performance index does not meet the preset requirements, the position of the intake manifold and / or the position of the branch pipe of the intake manifold shall be adjusted. Based on the operating conditions of the exhaust gas recirculation, exhaust gas recirculation pipe joints are arranged according to preset position parameters to construct a three-dimensional model of the intake manifold exhaust gas recirculation system. The intake manifold exhaust gas recirculation system includes the intake manifold, the exhaust gas recirculation pipeline, and the exhaust gas recirculation pipe joints connecting the intake manifold and the exhaust gas recirculation pipeline. Based on the three-dimensional model of the intake manifold exhaust gas recirculation system, the exhaust gas recirculation uniformity index of the intake manifold exhaust gas recirculation system is determined. Based on the exhaust gas recirculation uniformity index, the preset position parameters are adjusted, thereby adjusting the arrangement of the exhaust gas recirculation pipe joints. The portion of the exhaust gas recirculation (EGR) connector inserted into the intake manifold has openings on both the intake and exhaust sides. The preset position parameters include: the tilt angle of the EGR connector, the insertion depth of the EGR connector, and the deflection angle of the opening of the EGR connector. The tilt angle of the EGR connector is the angle between the central axis of the EGR connector and the horizontal direction, and the deflection angle of the opening of the EGR connector is the angle between the central axis of the EGR connector and the central axis of the opening.
2. The arrangement method of the exhaust gas recirculation pipe joint according to claim 1, characterized by, The flow performance indicators include the deviation of the mass flow coefficient of the gas in each branch of the intake manifold and the mass flow non-uniformity of the intake manifold.
3. The method of arranging an exhaust gas recirculation pipe joint according to claim 2, characterized in that, The step of determining the gas flow performance indicators within the intake manifold corresponding to the engine's operating conditions based on a pre-constructed three-dimensional model of the intake manifold includes: Based on the three-dimensional model of the intake manifold and the first preset correlation, the deviation of the mass flow coefficient of the gas in each branch of the intake manifold corresponding to the operating conditions of the engine is determined. The first preset association relationship is: in, In the formula, The deviation of the mass flow coefficient of the gas; The theoretical mass flow rate is the outlet of the i-th branch of the intake manifold. Let be the theoretical gas velocity at the outlet of the i-th branch of the intake manifold; Let be the theoretical gas density at the outlet of the i-th branch of the intake manifold; Let be the cross-sectional area of the outlet of the i-th branch pipe of the intake manifold; k The adiabatic index; R It is the ideal gas constant; Due to environmental pressures; Ambient temperature; Let be the outlet pressure of the i-th branch of the intake manifold; n This refers to the number of branch pipes in the intake manifold; This represents the actual mass flow rate at the outlet of the i-th branch pipe of the intake manifold. is the mass flow rate coefficient of the gas in the i-th branch of the intake manifold; It is the average mass flow coefficient of the gas in all branches of the intake manifold.
4. The method for arranging the exhaust gas recirculation pipe joint according to claim 2, characterized in that, The step of determining the gas flow performance indicators within the intake manifold corresponding to the engine's operating conditions based on a pre-constructed three-dimensional model of the intake manifold includes: Based on the three-dimensional model of the intake manifold and the second preset correlation, the mass flow non-uniformity of the intake manifold corresponding to the operating conditions of the engine is determined. The second preset association relationship is: in, In the formula, This represents the actual mass flow rate at the outlet of the i-th branch pipe of the intake manifold. n This refers to the number of branch pipes in the intake manifold; This is the maximum actual mass flow rate at all branch outlets of the intake manifold. It is the minimum actual mass flow rate among all the branch outlets of the intake manifold; This is the average mass flow rate at all branch outlets of the intake manifold.
5. The method for arranging the exhaust gas recirculation pipe joint according to claim 2, characterized in that, The preset requirements include: under the operating conditions of the engine, the mass flow coefficient deviation of the gas in each branch of the intake manifold is less than or equal to ±2.5%, and the mass flow non-uniformity of the intake manifold is less than or equal to ±5%.
6. The method for arranging the exhaust gas recirculation pipe joint according to claim 2, characterized in that, The adjustment of the position of the intake manifold and / or the position of the branch pipes of the intake manifold includes: If the actual mass flow rate at the outlet of one of the intake manifold branches is too low, the transition radius between the branch and the pressure regulating chamber is increased; if the actual mass flow rate at the outlet of one of the intake manifold branches is too high, the transition radius between the branch and the pressure regulating chamber is decreased.
7. The method for arranging the exhaust gas recirculation pipe joint according to claim 5, characterized in that, The adjustment of the position of the intake manifold and / or the position of the branch pipes of the intake manifold includes: If, under the operating conditions of the engine, the mass flow coefficient deviation of the gas in each branch of the intake manifold is greater than ±2.5%, and the mass flow non-uniformity of the intake manifold is greater than ±5%, then, based on the gas flow pressure distribution cloud map of the intake manifold, the angle between the central axis of the intake inlet of the intake manifold and the horizontal direction is adjusted.
8. The method for arranging the exhaust gas recirculation pipe joint according to claim 1, characterized in that, The uniformity index of exhaust gas recirculation includes the exhaust gas recirculation rate and the relative deviation of the exhaust gas recirculation rate. The step of adjusting the preset position parameters according to the exhaust gas recirculation uniformity index includes: Adjust the tilt angle of the exhaust gas recirculation pipe connector, the insertion depth of the exhaust gas recirculation pipe connector, and the deflection angle of the opening of the exhaust gas recirculation pipe connector to make the exhaust gas recirculation rate relatively deviate. .
9. The method for arranging the exhaust gas recirculation pipe joint according to claim 1, characterized in that, The engine's operating conditions include idling, partial load, and external characteristic conditions, and the exhaust gas recirculation operating parameters include minimum specific fuel consumption and maximum exhaust gas recirculation rate.