Air cylinder cover simulation piece temperature load applying method

Abstract

The invention provides a temperature load applying method for a cylinder cover simulation part. The method comprises the steps that the temperature condition is determined according to the working condition of an internal combustion engine; obtaining a temperature field according to the temperature condition, and determining an observation point position of a nose bridge area of the cylinder cover according to the temperature field; measurement is carried out through the observation point positions to obtain observation data, and induction coil parameters are determined according to the observation data; and obtaining a temperature load applying scheme according to the induction coil parameters. According to the method, the temperature load borne by the cylinder cover in actual work is accurately simulated through temperature conditions of a cylinder cover temperature field and induction coil parameters, and a temperature load applying scheme is determined.

Description

Technical Field

[0001] The invention relates to the technical field of engine testing, and in particular to a method for applying temperature load to a cylinder head simulation part. Background Art

[0002] The cylinder head is one of the important structural components of the internal combustion engine. It is used to close the upper part of the cylinder and form a combustion chamber together with the top of the piston and the cylinder wall. The cylinder head has an extremely complex structure, on which are processed the intake and exhaust valves, valve guide holes, etc., and the cooling water channel, intake and exhaust pipes and part of the combustion chamber are cast inside. When the internal combustion engine is working, the working environment of the cylinder head is very harsh and the stress conditions are very complicated. It not only needs to bear the mechanical loads such as the bolt preload generated during the assembly process of the internal combustion engine, but also needs to bear the heat load generated by gas combustion and the gas explosion pressure load. At the same time, due to the existence of cooling water channels, factors such as the uneven distribution of the coolant flow path will also lead to complex distribution of temperature and stress fields inside the cylinder head.

[0003] To determine the temperature load of the cylinder head under the condition of known mechanical load, a cylinder head coupling fatigue test is required. However, the traditional test method has high economic cost, long test cycle, complicated operation process, and insufficient test accuracy and precision. Therefore, it is necessary to design a method for applying temperature load to cylinder head simulation parts. Summary of the invention

[0004] The purpose of the present invention is to provide a method for applying temperature load to a cylinder head simulation part, so as to accurately simulate the temperature load borne by the cylinder head in actual work through the temperature conditions of the cylinder head temperature field and the parameters of the induction coil, and determine the temperature load application scheme.

[0005] To achieve the above object, the present invention provides the following solutions:

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

[0007] Determine the temperature conditions according to the internal combustion engine operating conditions; the temperature conditions include: thermal boundary conditions of the firing surface, thermal boundary conditions of the outer surface, thermal boundary conditions of the intake and exhaust pipe wall, and thermal boundary conditions of the cooling water channel wall;

[0008] The temperature field is obtained according to the temperature conditions, and the observation point of the nose bridge area of ​​the cylinder head is determined according to the temperature field;

[0009] The observation data are obtained by measuring at the observation points, and the induction coil parameters are determined based on the observation data; the induction coil parameters include: coil shape, copper tube diameter, copper tube spacing and the distance between the coil and the heating surface.

[0010] The temperature load application scheme is obtained according to the induction coil parameters.

[0011] Optionally, the thermal boundary conditions of the firing surface include an average ambient temperature and a firing surface cross-flow heat transfer coefficient;

[0012] The average ambient temperature is calculated as: in, is the average ambient temperature, h g is the instantaneous convection heat transfer coefficient, T g is the instantaneous ambient temperature, θ is the crankshaft angle;

[0013] The calculation formula of the heat transfer coefficient of the fire surface is: in, is the average convection heat transfer coefficient.

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

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

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

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

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

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

[0020] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the method for applying temperature load to a cylinder head simulation part provided by the present invention comprises: determining temperature conditions according to the operating conditions of an internal combustion engine; obtaining a temperature field according to the temperature conditions, and determining observation points of the nose bridge area of ​​the cylinder head according to the temperature field; measuring at the observation points to obtain observation data, and determining induction coil parameters according to the observation data; and obtaining a temperature load application scheme according to the induction coil parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 This is a flow chart of a method for applying a temperature load according to an embodiment of the present invention;

[0023] Figure 2 The observation point for the embodiment of the present invention is the bit arrangement map. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention is 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: determining temperature conditions according to the internal combustion engine operating conditions; the temperature conditions include: thermal boundary conditions of the firing surface, thermal boundary conditions of the outer surface, thermal boundary conditions of the wall of the intake and exhaust pipes, and thermal boundary conditions of the wall of the cooling water channel;

[0028] Specifically, the thermal boundary conditions of the fire surface include the average ambient temperature and the convection heat transfer coefficient of the fire surface. In this embodiment, when the internal combustion engine operates at rated power, its working cycle is a four-stroke, in which the convection heat transfer coefficient and temperature show periodic fluctuations. From a macroscopic perspective, each cycle is completed very quickly, and the cycle time is negligible, which is approximately treated as a steady state. The calculation formula for the average ambient temperature is:

[0029]

[0030] The calculation formula of the heat transfer coefficient of the fire surface is:

[0031]

[0032] in, is the average ambient temperature, T g is the instantaneous ambient temperature, in K; h g is the instantaneous convective heat transfer coefficient, is the average convection heat transfer coefficient of the firepower, in W / (m 2 ·K); θ is the crankshaft angle, the unit is degree.

[0033] The outer surface thermal boundary conditions include the outer surface temperature and the outer surface convection heat transfer coefficient. The outer surface of the cylinder head contacts the air and conducts convection heat transfer. The temperature and convection heat transfer coefficient on the outer surface are not large, and the thermal impact on the cylinder head can be ignored. In this embodiment, the outer surface temperature is room temperature 298K, and the outer surface convection heat transfer coefficient is 30W / (m 2 ·K).

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

[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 and can take away part of the heat received by the cylinder head. However, the surface of the water cavity is complex and tortuous, and the heat received by each section of the water cavity is different, resulting in different heat transfer coefficients. This embodiment uses Fluent software to simulate and analyze the cylinder head, accurately simulate the flow of coolant in the cylinder head, and then obtain the temperature distribution of the fluid domain, and obtain the initial boundary conditions of the thermodynamic simulation calculation through coupling analysis, and regard them as the thermal boundary conditions of the cooling water channel wall.

[0036] Step 200: obtaining a temperature field according to the temperature condition, and determining an observation point position of the nose bridge area of ​​the cylinder head according to the temperature field;

[0037] Specifically, this embodiment uses ABAQUS simulation software to apply different thermal boundary conditions to different positions of the cylinder head, and calculates the temperature field of the cylinder head. The fire surface of the nose bridge area between the intake and exhaust valves is selected as the key feature area, and 7 observation points are arranged in this area. The specific arrangement scheme is as follows Figure 2 As shown, the observation points are symmetrically distributed along two symmetry axes parallel to the edge of the fire surface in the nose bridge area and passing through the center of the fire surface in the nose bridge area, where L is the length of the fire surface and W2 is the width of the fire surface.

[0038] Step 300: measuring at observation points to obtain observation data, and determining induction coil parameters according to the observation data;

[0039] Specifically, the induction coil is an electromagnetic coil, and the induction coil parameters include: coil shape, copper tube diameter, copper tube spacing and the distance between the coil and the heating surface. In this embodiment, the fire surface of the cylinder head nose bridge area simulation part is used as the heating surface, which is rectangular. The coil shape is designed to be a rectangular shape similar to the fire surface. The determination of the copper tube diameter is based on the specific size of the simulation part, and this embodiment does not make a specific limitation. During the heating process, the electric current will generate a large amount of heat in the copper tube, and the temperature of the induction coil is maintained within an appropriate range by passing cooling water through the hollow copper tube.

[0040] Compared with the same type of internal combustion engines, this embodiment reduces the copper tube spacing corresponding to the exhaust valve side, and tilts the induction coil during installation, so that the induction coil on the exhaust valve side is closer to the heating surface to ensure that the heating temperature of the exhaust valve side area is higher.

[0041] It should be noted that the cylinder head temperature field data was obtained through ABAQUS simulation software, and it was found that the temperature of the nose bridge area between the intake and exhaust valves was higher, and due to the high temperature difference between the intake and exhaust valves, there was a significant temperature gradient distribution in the nose bridge area. The induction heating temperature distribution law of this embodiment is as follows: the smaller the copper tube spacing, 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 a temperature load application plan according to the induction coil parameters.

[0043] Specifically, for the two key design parameters of copper tube spacing and the distance between the coil and the heating surface, 3 to 4 parameter levels were selected for orthogonal experiments. The Maxwell3D module in Ansoft software was used to simulate the electromagnetic thermal structure coupling heating of the cylinder head nose bridge area simulation part, and the transient heat flux distribution data of the simulation part 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 ​​of the 7 observation points under each orthogonal experiment were compared with the reference temperature values, and the best solution with a gradient distribution trend consistent with the expectation and an error range of less than 10% was selected to ensure the accuracy of the induction coil design and the reliability of the heating effect. The best solution was used as the temperature load application solution.

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

[0045] Specifically, the fixture includes bolts and a plate, the mechanical load applying device includes a torque wrench and a hydraulic loading sub-device, the heating device adopts an electromagnetic induction coil, and the measuring module includes a thermocouple, a stress strain sensor and a displacement sensor.

[0046] Furthermore, the simulation part is firmly clamped by bolts and plates to limit the freedom of the simulation part during the test. The electromagnetic induction heating technology is used to accurately heat the bottom fire surface of the simulation part using the induction coil designed in this embodiment, and thermocouples are arranged at 7 key observation points to measure the temperature change of the nose bridge area of ​​the cylinder head.

[0047] The simulation test of this embodiment adopts a test cycle of heating-insulation-cooling, which can more accurately simulate the start-up-operation-shutdown conditions of the internal combustion engine, and each cycle constitutes a cycle number.

[0048] Specifically, before the simulation test begins, the bolt preload and the gas explosion pressure are first determined by finite element analysis technology. The bolt preload is an assembly force that ensures a firm connection between the cylinder head and the engine body. In this embodiment, the simulation of the bolt preload is achieved by applying a normal constant pressure load to the top surface of the cylinder head simulation part. Since the nose bridge area of ​​the cylinder head is far away from the bolt position, the bolt preload on the nose bridge area is relatively small. This embodiment uses finite element analysis software (such as ABAQUS) to simulate and calculate the size 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. The pre-simulation of the bolt preload makes the cylinder head thermal fatigue simulation test of this embodiment more accurate. This embodiment does not pre-simulate the gas explosion pressure, so that the pre-simulation can eliminate the interference of the gas explosion pressure, and improves the accuracy and precision of the data on the influence of temperature load on the nose bridge area of ​​the cylinder head.

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

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

[0052] Insulation stage: After reaching the highest temperature, the cylinder head maintains this temperature for a period of time. This stage is achieved by controlling the fluctuation range of the temperature at the observation point (for example, ±8°C) 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 of blowing air into the water channel, and the cooling rate is controlled by adjusting the wind speed.

[0054] It should be noted that the heating rate, the maximum temperature reached during heating, and the temperature amplitude generated during the simulation test heating process of this embodiment will have a huge impact on the stress value at the dangerous position of the nose bridge area of ​​the cylinder head. The average heating rate, maximum temperature, and temperature amplitude are selected as heating parameters, and the maximum stress value and average stress value of the simulated part are obtained through an orthogonal test of 3 factors and 3 levels. Among them, the maximum stress value reflects the stress peak value that may be reached during the entire heating, insulation, and cooling process, indicating the limit state that may be reached during 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 of the heating process.

[0055] The crack development of the simulated part was observed by stopping the machine to check the crack every 100 cycles. The failure boundary of this embodiment was set to the crack length reaching 5 mm, at which time the test was stopped and the thermal-mechanical coupling fatigue life (number of cycles) was recorded. This embodiment conducted 6 tests under each thermal boundary condition to ensure that at least 5 tests had valid test data, and finally obtained the average thermal fatigue life under each thermal boundary condition.

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

[0057] 1) The cylinder head simulation test device is used to conduct simulation tests, which significantly shortens the heating time and speeds up the test process;

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

[0059] 3) The orthogonal experimental method is used to improve the accuracy of the simulation experiment.

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

[0061] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for applying temperature load to a cylinder head simulation component, characterized in that: The steps include: Determine the temperature conditions according to the working conditions of the internal combustion engine; the temperature conditions include: thermal boundary conditions of the firing surface, thermal boundary conditions of the outer surface, thermal boundary conditions of the wall of the intake and exhaust pipes, and thermal boundary conditions of the wall of the cooling water channel; Obtaining a temperature field according to the temperature condition, and determining an observation point position of the nose bridge area of ​​the cylinder head according to the temperature field; The observation points are measured to obtain observation data, and the induction coil parameters are determined according to the observation data; the induction coil parameters include: coil shape, copper tube diameter, copper tube spacing and the distance between the coil and the heating surface. A temperature load application scheme is obtained according to the induction coil parameters.

2. The method for applying temperature load to a cylinder head simulation component according to claim 1, characterized in that: The thermal boundary conditions of the firing surface include the average ambient temperature and the firing surface flow heat transfer coefficient; The calculation formula of the average ambient temperature is: in, is the average ambient temperature, h g is the instantaneous convection heat transfer coefficient, T g is the instantaneous ambient temperature, θ is the crankshaft angle; The calculation formula of the fire surface flow heat transfer coefficient is: in, is the average convection heat transfer coefficient.

3. The method for applying temperature load to a cylinder head simulation component according to claim 1, characterized in that: The outer surface thermal boundary conditions include the outer surface temperature and the outer surface convection heat transfer coefficient; the outer surface temperature is room temperature, and the outer surface convection heat transfer coefficient is 30W / (m 2 ·K).

4. The method for applying temperature load to a cylinder head simulation component according to claim 1, characterized in that: The working environment of the cylinder head is simulated by simulation software to obtain the temperature distribution of the fluid domain, and the temperature distribution of the fluid domain is used as the thermal boundary condition of the cooling water channel wall.

5. The method for applying temperature load to a cylinder head simulation component according to claim 1, characterized in that: A temperature field is obtained according to the temperature conditions, and observation points in the nose bridge area of ​​the cylinder head are determined according to the temperature field. The specific steps are: the temperature conditions are calculated by finite element analysis technology to obtain the temperature field, and a plurality of observation points are arranged on the fire surface of the nose bridge area between the intake valve and the exhaust valve according to the temperature field.

6. The method for applying temperature load to a cylinder head simulation component according to claim 5, characterized in that: The observation points are symmetrically distributed along two symmetry axes that are parallel to the edges of the firepower surface of the bridge of the nose area and pass through the center of the firepower surface of the bridge of the nose area.

7. The method for applying temperature load to a cylinder head simulation component according to claim 1, characterized in that: The induction coil is arranged obliquely outside the heating surface; the coil is rectangular in shape; and the diameter of the copper tube is determined by the actual size of the cylinder head.

8. The method for applying temperature load to a cylinder head simulation component according to claim 1, characterized in that: A temperature load application scheme is obtained according to the induction coil parameters, and the specific steps are: multiple heating schemes are implemented on the heating surface according to different induction coil parameters, temperature values ​​are obtained through the observation points, the temperature values ​​are compared with reference values, and the gradient distribution trend is obtained, and the heating scheme corresponding to the gradient distribution trend that does not exceed the expected trend error range is used as the temperature load application scheme.

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