A method for applying temperature load to a cylinder head simulation component

Abstract

This invention provides a method for applying temperature load to a cylinder head simulation component. The method includes: determining temperature conditions based on the operating conditions of an internal combustion engine; obtaining a temperature field based on the temperature conditions, and determining observation points in the cylinder head nose area based on the temperature field; measuring the observation points to obtain observation data, and determining induction coil parameters based on the observation data; and obtaining a temperature load application scheme based on the induction coil parameters. This method accurately simulates the temperature load experienced by the cylinder head during actual operation using the temperature conditions of the cylinder head temperature field and the induction coil parameters, and determines the temperature load application scheme.

Description

Technical Field

[0001] This invention relates to the field of engine testing technology, and in particular to a method for applying temperature loads to a cylinder head simulator. Background Technology

[0002] The cylinder head is one of the most important structural components of an internal combustion engine. It seals off the upper part of the cylinder and, together with the piston top and cylinder wall, forms the combustion chamber. The cylinder head has an extremely complex structure, machined with intake and exhaust valves, valve guide holes, etc., and internally contains cooling water channels, intake and exhaust pipes, and part of the combustion chamber. During engine operation, the cylinder head operates in a very harsh environment and experiences complex stresses. It must withstand not only mechanical loads such as bolt preload generated during engine assembly, but also thermal loads from gas combustion and combustion pressure loads. Furthermore, the presence of cooling water channels and the uneven distribution of coolant flow paths contribute to a complex distribution of temperature and stress fields within the cylinder head.

[0003] Determining the temperature load on a cylinder head under known mechanical loads requires coupled fatigue testing. However, traditional testing methods are costly, time-consuming, complex, and lack sufficient accuracy and precision. Therefore, it is essential to design a method for applying temperature loads to a cylinder head simulator. Summary of the Invention

[0004] The purpose of this invention is to provide a method for applying temperature load to a cylinder head simulation component, so as to accurately simulate the temperature load that the cylinder head bears in actual operation through the temperature conditions of the cylinder head temperature field and the parameters of the induction coil, and to determine the temperature load application scheme.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A method for applying a temperature load to a cylinder head simulation component includes the following steps:

[0007] The temperature conditions are determined based on the internal combustion engine operating conditions. The temperature conditions include: thermal boundary conditions of the fire face, thermal boundary conditions of the outer surface, thermal boundary conditions of the intake and exhaust pipe walls, and thermal boundary conditions of the cooling water passage walls.

[0008] The temperature field is obtained based on the temperature conditions, and the observation points in the nose area of ​​the cylinder head are determined based on the temperature field.

[0009] Measurements are taken at observation points to obtain observation data, and the parameters of the induction coil are determined based on the observation data. The parameters of the induction coil include: coil shape, copper tube diameter, copper tube spacing, and distance between the coil and the heating surface.

[0010] The temperature load application scheme is obtained based on the parameters of the induction coil.

[0011] Optionally, the thermal boundary conditions of the fire-fighting surface include the average ambient temperature and the convective heat transfer coefficient of the fire-fighting surface;

[0012] The formula for calculating the average ambient temperature is: in, h represents the average ambient temperature. g T is the instantaneous convective heat transfer coefficient. g The instantaneous ambient temperature is θ, and the crankshaft angle is θ.

[0013] The formula for calculating the convective heat transfer coefficient of a fire engine is: in, The average thermal convective heat transfer coefficient is denoted as .

[0014] Optionally, the external surface thermal boundary conditions include the external surface temperature and the external surface convective heat transfer coefficient; the external surface temperature is room temperature, and the external surface convective heat transfer coefficient is 30 W / (m²). 2 ·K).

[0015] Optionally, the working environment of the cylinder head can be simulated using simulation software to obtain the temperature distribution in the fluid domain, and the temperature distribution in the fluid domain can be used as the thermal boundary condition of the cooling water channel wall.

[0016] Optionally, the temperature field is obtained based on the temperature conditions, and the observation points in the nose bridge area of ​​the cylinder head are determined based on the temperature field. The specific steps are as follows: the temperature conditions are calculated using finite element analysis technology to obtain the temperature field, and multiple observation points are arranged on the fire surface of the nose bridge area between the intake valve and the exhaust valve based on the temperature field.

[0017] Optionally, the observation points are symmetrically distributed along two axes of symmetry that are parallel to the edge of the nose bridge fire surface and pass through the center of the nose bridge fire surface.

[0018] Optionally, the induction coil is inclined and positioned outside the heating surface; the coil shape is rectangular; and the diameter of the copper tube is determined by the actual dimensions of the cylinder head.

[0019] Optionally, a temperature load application scheme is obtained based on the parameters of the induction coil. The specific steps are as follows: multiple heating schemes are implemented on the heating surface according to different induction coil parameters, temperature values ​​are obtained through observation points, the temperature values ​​are compared with reference values ​​to obtain the gradient distribution trend, and the heating scheme corresponding to the gradient distribution trend that does not exceed the expected trend error range is taken as the temperature load application scheme.

[0020] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: The cylinder head simulation component temperature load application method provided by the present invention includes: determining temperature conditions according to the internal combustion engine operating conditions; obtaining a temperature field according to the temperature conditions, and determining the observation points of the cylinder head nose area according to the temperature field; measuring through the observation points to obtain observation data, and determining the induction coil parameters according to the observation data; and obtaining a temperature load application scheme according to the induction coil parameters. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the temperature load application method according to an embodiment of the present invention;

[0023] Figure 2 The observation point is arranged in a position diagram according to an embodiment of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 As shown, the present invention provides a method for applying temperature load to a cylinder head simulation component, comprising the following steps:

[0027] Step 100: Determine the temperature conditions based on the internal combustion engine operating conditions; the temperature conditions include: thermal boundary conditions of the fire face, thermal boundary conditions of the outer surface, thermal boundary conditions of the intake and exhaust pipe walls, and thermal boundary conditions of the cooling water channel walls.

[0028] Specifically, the thermal boundary conditions of the fire-propelled surface include the average ambient temperature and the convective heat transfer coefficient of the fire-propelled surface. In this embodiment, when the internal combustion engine operates at its rated power, its working cycle is a four-stroke cycle, in which the convective heat transfer coefficient and temperature exhibit periodic fluctuations. From a macroscopic perspective, the completion speed of each cycle is extremely fast, and the cycle time is negligible, thus approximating a steady-state situation. The formula for calculating the average ambient temperature is:

[0029]

[0030] The formula for calculating the convective heat transfer coefficient of a fire engine is:

[0031]

[0032] in, T represents the average ambient temperature. g The instantaneous ambient temperature is expressed in Kelvin (K); h g The instantaneous convective heat transfer coefficient is... The mean convective heat transfer coefficient of the fire unit is expressed in W / (m²). 2 ·K); θ is the crankshaft rotation angle, in deg.

[0033] The external surface thermal boundary conditions include the external surface temperature and the external surface convective heat transfer coefficient. The cylinder head's external surface is in contact with air and undergoes convective heat transfer. The temperature and convective heat transfer coefficient on the external surface are relatively small, and their thermal impact on the cylinder head can be ignored. In this embodiment, the external surface temperature is room temperature (298 K), and the external surface convective heat transfer coefficient is 30 W / (m²). 2 ·K).

[0034] The thermal boundary conditions of the intake and exhaust pipe walls are the convective heat transfer coefficients of the intake pipe wall and the exhaust pipe wall. The convective heat transfer coefficients of the intake and exhaust pipe walls of the internal combustion engine simulated in this embodiment are relatively close. However, since the intake pipe introduces unburned cold air, while the exhaust pipe discharges hot gas after being subjected to high temperatures in the combustion chamber, the temperature of the exhaust pipe is significantly higher than that of the intake pipe.

[0035] The thermal boundary condition of the cooling water channel wall is the heat transfer coefficient of the cooling water cavity. As the most important structure for cylinder head cooling, the cooling water cavity has a strong heat transfer capacity, capable of removing some of the heat received by the cylinder head. However, the surface of the water cavity is complex and tortuous, and the amount of heat received by each section varies, resulting in different heat transfer coefficients. This embodiment uses Fluent software to simulate and analyze the cylinder head, accurately simulating the flow of coolant within the cylinder head, thereby obtaining the temperature distribution of the fluid domain. Through coupled analysis, the initial boundary conditions for thermodynamic simulation calculations are obtained and considered as the thermal boundary conditions of the cooling water channel wall.

[0036] Step 200: Obtain the temperature field based on the temperature conditions, and determine the observation points in the cylinder head bridge area based on the temperature field;

[0037] Specifically, this embodiment uses ABAQUS simulation software to apply different thermal boundary conditions to different locations on the cylinder head and calculates the temperature field of the cylinder head. The nose bridge area between the intake and exhaust valves is selected as the key feature region, and seven observation points are arranged in this region. The specific arrangement scheme is as follows: Figure 2 As shown, the observation points are symmetrically distributed along two axes of symmetry that are parallel to the edge of the nose bridge fire surface and pass through the center of the nose bridge fire surface, where L is the length of the fire surface and W2 is the width of the fire surface.

[0038] Step 300: Measure the observation points to obtain observation data, and determine the parameters of the induction coil based on the observation data;

[0039] Specifically, the induction coil is an electromagnetic coil, and its parameters include: coil shape, copper tube diameter, copper tube spacing, and distance between the coil and the heating surface. In this embodiment, the firing surface of the cylinder head nose bridge simulated component is used as the heating surface, which is rectangular. The coil shape is designed to be a rectangle similar to the firing surface. The copper tube diameter is determined based on the specific dimensions of the simulated component, and this embodiment does not impose a specific limitation. During the heating process, the current generates a large amount of heat in the copper tube, and the temperature of the induction coil is maintained within a suitable range by circulating cooling water through the hollow copper tube.

[0040] Compared to similar internal combustion engines, this embodiment reduces the spacing between the copper pipes on the exhaust valve side and tilts the induction coil during installation, making the induction coil on the exhaust valve side closer to the heating surface, thus ensuring a higher heating temperature in the exhaust valve side area.

[0041] It should be noted that, using ABAQUS simulation software to obtain cylinder head temperature field data, it was found that the temperature in the bridge area between the intake and exhaust valves is relatively high, and due to the high temperature difference between the intake and exhaust valves, a significant temperature gradient distribution exists in the bridge area. The induction heating temperature distribution pattern in this embodiment is as follows: the smaller the spacing between the copper tubes, the higher the heating temperature; the smaller the distance between the coil and the heating surface, the higher the heating temperature.

[0042] Step 400: Obtain the temperature load application scheme based on the induction coil parameters.

[0043] Specifically, for the two key design parameters—the spacing between copper tubes and the distance between the coil and the heating surface—orthogonal experiments were conducted at three to four parameter levels. The Maxwell 3D module in Ansoft software was used to simulate the electromagnetic-thermal coupling heating of the cylinder head nose area. The obtained transient heat flow distribution data of the simulated component was imported into the transient temperature module of Ansys software to obtain the temperature field distribution at each transient moment during the heating process. The temperature values ​​at seven observation points in each orthogonal experiment were compared with the reference temperature values. The optimal scheme, where the gradient distribution trend was consistent with expectations and the error range was within 10%, was selected to ensure the accuracy of the induction coil design and the reliability of the heating effect. The optimal scheme was then used as the temperature load application scheme.

[0044] The test apparatus used in the cylinder head thermal fatigue simulation test of this embodiment includes: a simulation part, a fixture, a mechanical load application device, a heating device, a measurement module, and a control module; the mechanical load application device surrounds the simulation part through the fixture, the heating device is connected to the simulation part, and the measurement module is connected to the mechanical load application device and the control module respectively.

[0045] Specifically, the fixture includes bolts and plates, the mechanical load application device includes a torque wrench and a hydraulic loading sub-device, the heating equipment uses an electromagnetic induction coil, and the measurement module includes thermocouples, stress-strain sensors and displacement sensors.

[0046] Furthermore, the simulated component is securely clamped by bolts and plates to restrict its degrees of freedom during the test. Electromagnetic induction heating technology is employed, using the induction coil designed in this embodiment to precisely heat the bottom surface of the simulated component, and thermocouples are placed at seven key observation points to measure temperature changes in the cylinder head nose area.

[0047] The simulation test in this embodiment adopts a heating-heat preservation-cooling test cycle, which can accurately simulate the start-up-operation-stop condition of an internal combustion engine. Each cycle constitutes a cycle number.

[0048] Specifically, before the simulation test begins, the bolt preload and combustion pressure are first determined using finite element analysis (FEM). The bolt preload is an assembly force that ensures a secure connection between the cylinder head and the engine block. In this embodiment, the bolt preload is simulated by applying a normal constant pressure load to the top surface of the cylinder head simulator. Because the nose bridge area of ​​the cylinder head is far from the bolt locations, the bolt preload force acting on the nose bridge area is relatively small. This embodiment uses finite element analysis software (such as ABAQUS) to simulate and calculate the magnitude of the actual normal constant pressure load acting on the nose bridge area.

[0049] It should be noted that the main fatigue failure of the cylinder head is low-cycle creep fatigue failure caused by alternating cyclic thermal stress. Pre-simulation of bolt preload makes the cylinder head thermal fatigue simulation test in this embodiment more accurate. This embodiment does not pre-simulate the combustion pressure of the combustion gases, allowing the pre-simulation to eliminate interference from combustion pressure and improving the accuracy and precision of the data on the influence of temperature load on the cylinder head nose area.

[0050] Specifically, a complete cycle process includes the following three stages:

[0051] Heating phase: The cylinder head is heated to its maximum temperature. The duration of this phase is determined by the power of the induction coil.

[0052] Temperature holding phase: After reaching the maximum temperature, the cylinder head maintains this temperature for a period of time. This phase is achieved by controlling the fluctuation range of the observation point temperature (e.g., ±8℃) until the temperature drops to the set lower limit temperature due to natural cooling.

[0053] Cooling stage: Rapid cooling is achieved by forced convection cooling through airflow into the water channels, and the cooling rate is controlled by adjusting the airflow speed.

[0054] It should be noted that the heating rate, the highest temperature reached, and the resulting temperature amplitude during the simulated heating process in this embodiment will have a significant impact on the stress value at the critical location in the cylinder head nose area. The average heating rate, highest temperature, and temperature amplitude were selected as heating parameters, and the maximum and average stress values ​​of the simulated part were obtained through a 3-factor, 3-level orthogonal experiment. The maximum stress value reflects the peak stress that may be reached during the entire heating, holding, and cooling process, indicating the potential limit state of the stress concentration process; the average stress value is obtained by dividing the time integral of the stress value at each moment during the heating process by the unit cycle time, reflecting the overall stress state during the heating process.

[0055] The crack development of the simulated component was observed by stopping the test every 100 cycles to check for cracks. In this embodiment, the failure boundary was set at a crack length of 5 mm, at which point the test was stopped and the thermo-mechanical coupled fatigue life (number of cycles) was recorded. This embodiment performed 6 tests under each thermal boundary condition to ensure at least 5 valid test data points, ultimately obtaining the average thermal fatigue life under each thermal boundary condition.

[0056] The beneficial effects of this invention are as follows:

[0057] 1) The simulation test conducted by the cylinder head simulation test device significantly shortened the heating time and accelerated the test process;

[0058] 2) The cylinder head simulation device fully considers the water channel structure, improving the accuracy of the test;

[0059] 3) The use of orthogonal experimental design improved the accuracy of the simulation experiment.

[0060] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0061] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method of applying temperature loads to a cylinder head mockup, characterized in that, The method comprises the following steps: determining a temperature condition according to the working condition of the internal combustion engine; the temperature condition comprises a fire surface thermal boundary condition, an outer surface thermal boundary condition, an intake and exhaust pipeline wall surface thermal boundary condition and a cooling water channel wall surface thermal boundary condition; obtaining a temperature field according to the temperature condition, and determining observation point positions of a nose bridge area of a cylinder head cover according to the temperature field; the specific steps are: calculating the temperature condition by a finite element analysis technology to obtain the temperature field, and arranging a plurality of observation point positions on the fire surface of the nose bridge area between the intake valve and the exhaust valve according to the temperature field; the observation point positions are symmetrically distributed along two symmetric axes parallel to the edge of the fire surface of the nose bridge area and passing through the center of the fire surface of the nose bridge area; measuring through the observation point positions to obtain observation data, and determining induction coil parameters according to the observation data; the induction coil parameters comprise a coil shape, a copper pipe diameter, a copper pipe spacing and a coil-heating surface distance; obtaining a temperature load application scheme according to the induction coil parameters; the specific steps are: implementing a plurality of heating schemes on the heating surface according to different induction coil parameters, obtaining temperature values through the observation point positions, comparing the temperature values with reference values to obtain a gradient distribution trend, and taking the heating scheme corresponding to the gradient distribution trend not exceeding the expected trend error range as the temperature load application scheme.

2. The cylinder head mockup temperature load application method according to claim 1, characterized by, The fire surface thermal boundary condition comprises an average ambient temperature and a fire surface convection heat transfer coefficient; The average ambient temperature is calculated by the following formula: ; wherein, is the average ambient temperature, is the instantaneous convective heat transfer coefficient, is the instantaneous ambient temperature, is the crank angle; The calculation formula of the fire surface convection heat transfer coefficient is: ; wherein, is the average fire surface convection heat transfer coefficient.

3. The cylinder head mockup temperature load application method according to claim 1, characterized by, The outer surface thermal boundary condition includes an outer surface temperature and an outer surface convective heat transfer coefficient; the outer surface temperature is room temperature, and the outer surface convective heat transfer coefficient is 30 W / (m 2 K).

4. The cylinder head mockup temperature load application method according to claim 1, characterized by, simulating the working environment of the cylinder head cover by simulation software to obtain a fluid domain temperature distribution, and taking the fluid domain temperature distribution as the cooling water channel wall surface thermal boundary condition.

5. The cylinder head mockup temperature load application method according to Claim 1, characterized by, The induction coil is obliquely arranged outside the heating surface; the coil shape is rectangular; and the copper pipe diameter is determined by the actual size of the cylinder head cover.

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