Method and device for applying mechanical load to cylinder cover simulation part

Abstract

The invention provides a mechanical load applying method for a cylinder cover simulation part. The method comprises the following steps: obtaining a mechanical load internal relationship according to mechanical load characteristics; different internal combustion engine operation conditions are simulated, and mechanical load data under the different internal combustion engine operation conditions are obtained; and obtaining a mechanical load applying scheme according to the mechanical load data and the mechanical load internal relationship. According to the method, the temperature load and the mechanical load borne by the cylinder cover nose bridge area in actual work are accurately simulated through the influence of the working condition parameters of the internal combustion engine on the in-cylinder gas detonation pressure.

Description

Technical Field

[0001] The invention relates to the technical field of engine testing, and in particular to a method and device for applying mechanical 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] The Chinese patent with publication number CN106610355A discloses a thermal engine fatigue test method, including: setting load loading parameters; controlling the surface temperature of the sample to cycle within a set temperature range and applying a temperature load to the sample; applying a mechanical load to the sample according to a set functional relationship between the mechanical load and the temperature; and ending the test when the set number of cyclic loading is reached. However, this test method lacks targeted design for specific parts of the nose bridge area of ​​the cylinder head, and does not take into account the complexity of the mechanical load in this area, especially the influence of bolt preload and gas explosion pressure load. Therefore, it is very necessary to design a method and device for applying mechanical load to a cylinder head simulation part. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for applying mechanical load to a cylinder head simulation part, which can accurately simulate the temperature load and mechanical load borne by the nose bridge area of ​​the cylinder head in actual work through the influence of the internal combustion engine operating parameters on the explosion pressure of the combustion gas in the cylinder.

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

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

[0007] The internal relationship of the mechanical load is obtained according to the mechanical load characteristics; the mechanical load includes: bolt preload and maximum burst pressure;

[0008] Simulate different internal combustion engine operating conditions to obtain mechanical load data under different internal combustion engine operating conditions; internal combustion engine operating conditions include: ignition advance angle, load and speed;

[0009] A mechanical load application plan is obtained according to the mechanical load data and the internal relationship of the mechanical load.

[0010] Optionally, the calculation formula of the internal relationship of the mechanical load is: P0 = (1.25 ~ 2) πR 2 P max ; Where P0 is the bolt preload, R is the average radius of the sealing belt, P max The maximum burst pressure.

[0011] Optionally, different internal combustion engine operating conditions are simulated to obtain mechanical load data under different internal combustion engine operating conditions, specifically including:

[0012] By changing the ignition advance angle, the maximum explosion pressure and the maximum explosion pressure moment under different ignition advance angles are obtained;

[0013] By changing the load, the maximum burst pressure and the maximum burst pressure moment under different loads are obtained;

[0014] By changing the rotation speed, the maximum explosion pressure and the maximum explosion pressure moment at different rotation speeds are obtained.

[0015] A cylinder head simulation device under pre-temperature load, comprising: 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;

[0016] The heating device is used to apply a pre-temperature load, the mechanical load applying device is used to simulate the different mechanical loads borne by the cylinder head, the measuring module is used to measure the stress and deformation of the simulated part, and the control module is used to process the transmission data of the measuring module.

[0017] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the method for applying mechanical load to a cylinder head simulation part provided by the present invention comprises: obtaining the internal relationship of the mechanical load according to the mechanical load characteristics; simulating different internal combustion engine operating conditions to obtain mechanical load data under different internal combustion engine operating conditions; and obtaining a mechanical load application scheme according to the mechanical load data and the internal relationship of the mechanical load. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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.

[0019] Figure 1 A flow chart of a method for applying a mechanical load according to an embodiment of the present invention;

[0020] Figure 2 A flow chart of obtaining mechanical load data according to an embodiment of the present invention;

[0021] Figure 3 A point diagram for a simulation test of an embodiment of the present invention;

[0022] Figure 4 This is a sinusoidal waveform hydraulic pressure curve diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0023] 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.

[0024] 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.

[0025] like Figure 1 As shown, the present invention provides a method for applying mechanical load to a cylinder head simulation component, comprising the following steps:

[0026] Step 100: Obtaining the internal relationship of the mechanical load according to the mechanical load characteristics;

[0027] Specifically, the maximum explosion pressure, inertia force and vibration impact that the components of the internal combustion engine are subjected to constitute its mechanical load, and the intensity of these loads is a key factor in determining the mechanical strength of the internal combustion engine. Mechanical loads mainly include gas pressure, additional stress caused by vibration, inertia force of moving mass, and preload force. The mechanical load of an internal combustion engine has two significant characteristics: one is periodic changes, and the other is impact. These characteristics may cause fatigue damage and induce strong vibrations. For the cylinder head, its mechanical loads include: bolt preload and maximum explosion pressure. During operation, the fire surface of the cylinder head is continuously subjected to periodic mechanical shocks from the gas explosion pressure. This impact force is usually very large, which will cause mechanical impact fatigue of the base plate material, and this fatigue damage is closely related to the speed and load of the internal combustion engine.

[0028] It should be noted that in this embodiment, in order to ensure that the cylinder head can be firmly connected to the cylinder liner when the internal combustion engine is working under any working conditions, the bolt preload is designed to be significantly higher than the maximum explosion pressure of the gas, ensuring that the cylinder head will not be separated from the cylinder liner due to pressure fluctuations even under extreme conditions. The relationship between the bolt preload and the maximum explosion pressure is expressed by the following calculation formula:

[0029] P0=(1.25~2)πR 2 P max ;

[0030] Among them, P0 is the bolt preload, R is the average radius of the sealing belt, P max The maximum burst pressure.

[0031] Step 200: Simulate different internal combustion engine operating conditions to obtain mechanical load data under different internal combustion engine operating conditions; the internal combustion engine operating conditions include: ignition advance angle, load and speed;

[0032] Specifically, the working cycle of an internal combustion engine includes four strokes: intake, compression, power (combustion), and exhaust. In a four-stroke internal combustion engine, the piston reciprocates up and down four times, and the crankshaft rotates 720° (two turns) to complete a working cycle. During the compression stroke, as the piston moves toward the top dead center, the combustible mixture in the cylinder is compressed, and the pressure and temperature gradually increase. The power stroke is the stage where the explosion pressure reaches its peak. When the piston approaches the top dead center, the spark plug ignites the mixture, generating high-temperature and high-pressure combustion gas, which pushes the piston downward, at which time the explosion pressure reaches its highest. During the exhaust stroke, the piston moves upward, discharges the burned exhaust gas out of the cylinder, and the explosion pressure decreases accordingly. The explosion pressure is naturally generated through the combustion process of the internal combustion engine, and the change in the explosion pressure can be controlled by adjusting parameters such as the ignition advance angle, load, and speed.

[0033] Specifically, the specific steps of obtaining the mechanical load data under different internal combustion engine operating conditions according to the pre-applied temperature load are as follows: Figure 2 As shown, including:

[0034] Step 201: obtaining the maximum explosion pressure and the maximum explosion pressure moment under different ignition advance angles by changing the ignition advance angle;

[0035] Furthermore, the adjustment of the ignition advance angle has a direct impact on the combustion process of the internal combustion engine, and then acts on the explosion pressure. When the ignition advance angle increases, the combustion of the mixture starts earlier, resulting in an increase in the pressure peak generated during the combustion process, so that the energy released by the combustion is closer to the top dead center of the piston, thereby providing a greater driving force during the downward movement of the piston. In this embodiment, the ignition advance angle selects three conditions: the initial ignition advance angle, 10°A ahead of the initial ignition advance angle, and 10°A behind the initial ignition advance angle.

[0036] Step 202: by changing the load, obtaining the maximum burst pressure and the maximum burst pressure moment under different loads;

[0037] Furthermore, under different load conditions, the explosion pressure of the internal combustion engine shows obvious differences. Under high load conditions, in order to provide more power output, the internal combustion engine requires more fuel, which leads to an increase in fuel supply, which in turn increases the explosion pressure. On the contrary, under low load conditions, the fuel supply and the explosion pressure are reduced accordingly. In this embodiment, three load levels of 25%, 50% and 75% are selected for testing.

[0038] Step 203: By changing the rotation speed, the maximum explosion pressure and the maximum explosion pressure moment at different rotation speeds are obtained.

[0039] Furthermore, the change in speed affects the explosion pressure of the internal combustion engine through various factors, including but not limited to: combustion efficiency, combustion process, cylinder pressure, cycle fluctuation and internal combustion engine load. In this embodiment, three speed levels of 1000 rpm, 3000 rpm and 5000 rpm are selected for testing.

[0040] Step 300: Obtain a mechanical load application plan according to the mechanical load data and the internal relationship of the mechanical load.

[0041] like Figure 3 As shown, this embodiment conducts comprehensive tests at three levels of three parameters: ignition advance angle, load and speed, and selects the bridge area of ​​the fire surface between the intake and exhaust valves as the measurement point, and obtains the maximum explosion pressure and the maximum explosion pressure moment of the cylinder head under different ignition advance angles, different loads and different speeds, a total of 27 sets of data. Then, the bolt preload corresponding to each set of data is obtained according to the calculation formula of the bolt preload and the maximum explosion pressure, and 27 sets of mechanical load application schemes corresponding to different parameters are generated.

[0042] The present invention also provides a cylinder head simulation device under pre-temperature load, comprising: a simulation piece, 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 piece through the fixture, the heating device is connected to the simulation piece, and the measuring module is respectively connected to the mechanical load applying device and the control module;

[0043] The heating device is used to apply a pre-temperature load, the mechanical load applying device is used to simulate the different mechanical loads borne by the cylinder head, the measuring module is used to measure the stress and deformation of the simulated part, and the control module is used to process the transmission data of the measuring module.

[0044] 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.

[0045] Furthermore, the simulation part is firmly clamped by bolts and plates to limit the freedom of the simulation part during the test. The bottom (fire surface) of the simulation part is heated by an electromagnetic induction coil, and the winding shape of the coil is consistent with the shape of the bottom surface of the simulation part, both of which are rectangular. The spacing between the copper tubes in the coil is kept uniform, the coil is parallel to the fire surface, and maintains an optimal distance of 3-5mm from the fire surface. Multiple thermocouples are arranged on the bottom surface of the simulation part to monitor the temperature changes of the simulation part in real time.

[0046] Specifically, before the simulation test begins, the pre-temperature load is first determined according to the steady-state temperature field of the cylinder head to determine the heating conditions in the simulation test. The specific steps include:

[0047] The temperature field of the cylinder head is obtained by finite element analysis;

[0048] Furthermore, in the normal operation of the internal combustion engine, the duration of each working cycle is extremely short, so the internal combustion engine combustion chamber components can be approximately regarded as being in a steady-state heat transfer state, that is, it is assumed that the temperature of each area does not change with time. Therefore, the steady-state temperature field of this embodiment working under the stable working condition of 100% load of the internal combustion engine is used as the reference of the pre-temperature field. Through the ABAQUS simulation software, differentiated thermal boundary conditions are applied to different positions of the cylinder head to obtain the temperature field of the cylinder head.

[0049] It should be noted that under 100% load conditions, the thermal load borne by the cylinder head is more significant than that under other load conditions, and the temperature distribution is more uniform and more representative.

[0050] According to the temperature field, the average actual temperature and temperature stability range of the nose bridge area of ​​the fire face are obtained;

[0051] Furthermore, the post-processing tool ODB field output of ABAQUS was used to select the nose bridge area between the intake and exhaust valves and extract the temperature data of all nodes in this area. The node temperature data was statistically analyzed, and the arithmetic mean of all node temperatures was calculated to obtain the average actual temperature of the nose bridge area. This temperature value was set as the target temperature for the experimental heating.

[0052] The cooling device is used to obtain the cooling parameters of the cylinder head in a stable temperature range.

[0053] Furthermore, the pre-applied temperature load not only involves the temperature rise of the fire surface, but also includes the cooling effect of the cooling water channel. By keeping the cylinder head temperature stable within a certain range, the cooling water significantly reduces the thermal fatigue caused by temperature cycles. This embodiment uses air cooling instead of water cooling, and by keeping the wind speed constant, the stability of the cooling process is ensured, and the wind speed is used as a cooling parameter.

[0054] It should be noted that the cooling water circulates in the water channel inside the cylinder head, effectively absorbing and transferring the heat generated by the combustion of the cylinder head, thereby effectively limiting the excessive concentration of thermal stress in a local area of ​​the cylinder head, extending the service life of the cylinder head and improving its reliability. The air cooling in this embodiment has the same effect as the cooling water.

[0055] More specifically, a mechanical load application device is used to simulate various mechanical loads that the cylinder head bears in actual work, including bolt preload and gas explosion pressure. Then, the simulation test is carried out on the simulation part according to 27 sets of mechanical load application schemes corresponding to different parameters. Among them, the bolt preload is simulated by the actual assembly torque, and the size is precisely controlled by the torque wrench. The gas explosion pressure is simulated by the hydraulic loading sub-device. Stress strain sensors and displacement sensors are installed in the nose bridge area of ​​the simulation part to monitor the stress, strain response and deformation of the nose bridge area under the simulation test. Finally, the feedback signal of the sensor is received by the control module, and the operating state of the cylinder head simulation device is automatically adjusted.

[0056] Furthermore, in the cooling stage after the pre-temperature load simulation, rapid cooling is achieved by blowing air into the water channel, and the wind speed is controlled to remain constant during the cooling period, that is, the cooling rate remains constant.

[0057] More specifically, if Figure 4 As shown, in this embodiment, a cyclically loaded sinusoidal hydraulic pressure curve is applied to the bottom surface of the simulation component by a hydraulic loading sub-device. The hydraulic pressure curve can well reproduce the changes in the gas pressure in the working cycle of the internal combustion engine. The specific changes include:

[0058] Intake phase, which begins when the piston moves downward, the high-pressure valve in the cylinder closes and the pressure in the cylinder begins to gradually decrease. As the piston continues to move downward, the air-fuel mixture is sucked into the cylinder until the piston reaches the bottom dead center, at which point the pressure in the cylinder reaches its minimum value.

[0059] Compression stage: During this stage, the piston begins to move upward, the valve in the cylinder remains closed, and the mixture in the cylinder is compressed, causing the pressure to gradually increase, which continues until the piston approaches the top dead center. At this time, the pressure in the cylinder reaches its maximum value, creating the necessary conditions for ignition.

[0060] During the combustion phase, after ignition, the mixture begins to burn, generating a large amount of heat and pressure. The pressure in the cylinder increases sharply, reaching the so-called explosion point. The explosion point is the peak of pressure during the combustion process, and this stage is also the key stage for the output power of the internal combustion engine.

[0061] During the exhaust phase, when the piston moves upward again, the exhaust gas in the cylinder is discharged through the exhaust valve, and the pressure in the cylinder begins to gradually decrease until the piston reaches the top dead center, completing a working cycle. After that, the piston moves downward, and new mixed gas enters the cylinder again, and the cycle repeats.

[0062] It should be noted that, in this embodiment, one cycle period is defined as the time difference between two adjacent maximum burst pressure moments, where the peak value is the maximum burst pressure collected during the test, and the valley value is 0. The test uses the method of stopping the machine every 100 cycles to check the cracks to monitor the crack development in the nose bridge area of ​​the simulation part. When the crack length reaches 5mm, it is regarded as the failure boundary. At this time, the experiment is stopped and the internal combustion engine coupling fatigue life N (number of cycles) is recorded.

[0063] The beneficial effects of the present invention are as follows:

[0064] 1) The simulation test was carried out using a cylinder head simulation device, which significantly shortened the heating time and accelerated the test process;

[0065] 2) The cylinder head simulation device fully considers the water channel structure to improve the accuracy of the test;

[0066] 3) By studying the influence of changes in ignition advance angle, load and speed on the gas explosion pressure, the corresponding mechanical load application scheme was obtained, which improved the accuracy of the simulation test.

[0067] 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.

[0068] 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 mechanical load to a cylinder head simulation component, characterized in that: The steps include: Obtaining the internal relationship of the mechanical load according to the mechanical load characteristics; the mechanical load includes: bolt preload and maximum burst pressure; Simulating different internal combustion engine operating conditions to obtain mechanical load data under different internal combustion engine operating conditions; the internal combustion engine operating conditions include: ignition advance angle, load and speed; A mechanical load application scheme is obtained according to the mechanical load data and the internal relationship of the mechanical load.

2. The method for applying mechanical load to a cylinder head simulation component according to claim 1, characterized in that: The calculation formula of the internal relationship of the mechanical load is: P0 = (1.25 ~ 2) πR 2 P max ; Wherein, P0 is the bolt preload, R is the average radius of the sealing belt, P max The maximum burst pressure.

3. The method for applying mechanical load to a cylinder head simulation component according to claim 1, characterized in that: Simulate different internal combustion engine operating conditions to obtain mechanical load data under different internal combustion engine operating conditions, including: By changing the ignition advance angle, the maximum explosion pressure and the maximum explosion pressure moment under different ignition advance angles are obtained; By changing the load, the maximum burst pressure and the maximum burst pressure moment under different loads are obtained; By changing the rotation speed, the maximum explosion pressure and the maximum explosion pressure moment at different rotation speeds are obtained.

4. A cylinder head simulation device under pre-temperature load, used to implement the cylinder head simulation part mechanical load application method according to any one of claims 1 to 4, characterized in that: include: Simulation parts, fixtures, mechanical load application devices, heating equipment, measurement modules and control modules; 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 connected to the mechanical load applying device and the control module respectively; The heating device is used to apply the pre-temperature load, the mechanical load applying device is used to simulate the different mechanical loads borne by the cylinder head, the measuring module is used to measure the stress and deformation of the simulated part, and the control module is used to process the transmission data of the measuring module.

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