Test method for verifying the risk of thermal fatigue cracking at the piston throat

Abstract

The present invention relates to a test method for verifying the risk of thermal fatigue cracking at the throat of a piston, comprising the following steps: S100. adjusting the temperature of the intake manifold to a manually preset maximum target temperature; maintaining the temperature of the intake manifold at the maximum target temperature for a manually preset first target time, and then executing S200; S200. reducing the temperature of the intake manifold to a manually preset minimum target temperature; maintaining the temperature of the intake manifold at the minimum target temperature for a manually preset second target time, and then executing S300; S300. maintaining the temperature of the intake manifold at the minimum target temperature for a manually preset third target time, and then executing S400; S400. returning to and executing S100 until a manually preset cycle exit condition is met; S500. disassembling and inspecting the piston, and then determining the test results according to a manually preset assessment and verification method. The present invention makes piston detection more effective, saves development and debugging cycles, improves test results, and saves development costs.

Description

Technical Field

[0001] The present invention relates to the technical field of engine testing, and in particular to a test method for verifying the risk of thermal fatigue cracking at a piston throat position. Background Art

[0002] The piston is a key component within the engine's power cylinder, playing a vital role in combustion and power transmission. The piston throat is typically the hottest area of ​​the piston, placing it at a greater risk of thermal fatigue cracking. Therefore, engine reliability testing must assess the piston's resistance to thermal shock.

[0003] like Figure 2 As shown, the commonly used traditional testing method achieves thermal shock effects by controlling the temperature of the engine's outlet water. However, the piston is an internal component of the power cylinder and does not come into direct contact with the coolant, but rather with the air-fuel mixture. When air enters the combustion chamber from the intake manifold and mixes with the atomized fuel, the piston compresses the air-fuel mixture, achieving combustion and work. However, changes in the engine's outlet water temperature have far less direct impact on the piston than changes in the intake manifold temperature. Therefore, traditional thermal shock testing methods are not effective for piston verification.

[0004] The defects of the prior art are:

[0005] 1. In the prior art, the change in the engine outlet water temperature is far less direct than the change in the intake manifold temperature in affecting the piston, which affects the test verification effect and takes too long.

[0006] 2. The existing water temperature cold punching technology requires a dedicated cold punching equipment to be configured on the test bench, and the equipment is expensive, resulting in high testing costs. Summary of the Invention

[0007] In response to the above problems, the present invention provides a test method for verifying the risk of thermal fatigue cracking at the throat of a piston, the purpose of which is to make the detection of the piston more effective; save the development and debugging cycle; improve the test effect; and save development costs.

[0008] In order to solve the above problems, the technical solution provided by the present invention is:

[0009] The test method for verifying the risk of thermal fatigue cracking at the piston throat position includes the following steps:

[0010] S100. Setting the engine speed to a preset rated speed; setting the engine power to a preset rated power; adjusting the intake manifold temperature to a preset maximum target temperature; maintaining the intake manifold temperature at the maximum target temperature for a preset first target time, and then executing S200;

[0011] S200. Setting the engine speed to a manually preset torque point speed; setting the engine power to 0; lowering the intake manifold temperature to a manually preset minimum target temperature; maintaining the intake manifold temperature at the minimum target temperature for a manually preset second target time, and then executing S300;

[0012] S300. The engine speed is set to a manually preset low idle speed; the engine power is set to 0; the intake manifold temperature is maintained at the minimum target temperature for a manually preset third target time, and then S400 is executed;

[0013] S400. Return to and execute S100 until the manually preset loop exit condition is reached; the loop exit condition includes test completion and test abnormality; then perform the following operations according to the corresponding loop exit condition:

[0014] If the loop exit condition currently reached is that the test is completed, execute S500;

[0015] If the cycle exit condition currently reached is a test abnormality, the machine is shut down for inspection and the test is exited;

[0016] S500. Disassemble and inspect the piston, and then determine the test result according to the manually preset assessment and verification method.

[0017] Preferably, the maximum target temperature is expressed as follows:

[0018] T max =T1×k

[0019] Where: T max It is used to represent the maximum target temperature; T1 is used to represent the maximum temperature of the intake manifold of the engine during road operation collected before the test; k is used to represent the amplification factor.

[0020] Preferably, the maximum temperature of the intake manifold is the maximum temperature of the intake manifold collected under plateau conditions; the temperature range of the maximum temperature of the intake manifold is 75°C-85°C.

[0021] Preferably, the value of the amplification factor is 1.2.

[0022] Preferably, the method for lowering the temperature of the intake manifold to the manually preset minimum target temperature is: adjusting the opening of the inlet and outlet water valves of the intercooler of the test bench to the maximum, and then lowering the temperature of the intake manifold through the inlet and outlet water of the intercooler.

[0023] Preferably, the temperature range of the minimum target temperature is 30°C-35°C.

[0024] Preferably, the cycle exit condition in S400 is a condition for the completion of the test: the number of cycles from S100 to S300 reaches 6900 times, and the cumulative cycle time reaches 300 hours;

[0025] The cycle exit condition in S400 is a test abnormality condition, which is: the engine air leakage volume or exhaust temperature parameter has obvious abnormal fluctuations.

[0026] Preferably, the assessment and verification method in S500 specifically includes the following steps:

[0027] S510. Disassemble the throat position of the piston and inspect the throat position of the piston for cracks by magnetic particle inspection;

[0028] S520. If the inspection result of S510 shows that there is no crack at the throat of the piston, the assessment verification result is set to passed;

[0029] If the inspection result of S510 indicates that there is a crack at the throat of the piston, the inspection result is set to fail.

[0030] Preferably, the first target duration is 75 seconds; the second target duration is 30 seconds; and the third target duration is 50 seconds. Under the condition that the test engine is a 7.0-liter 350-horsepower engine:

[0031] The rated speed is 2300 rpm; the rated power is 257 kW; the torque point speed is 1500 rpm; and the low idle speed is 550 rpm.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. Since the intake manifold temperature difference is larger in the detection method of the present invention, and the intake manifold temperature directly affects the temperature of the piston, the detection of the piston is more effective.

[0034] 2. Since the intake manifold temperature changes greatly in the present invention, the thermal shock to the piston is large, and the test steps are simple, the cycle time is shortened, the test speed is accelerated, and the development and debugging cycle is saved.

[0035] 3. Since the test speed of the present invention is faster than that of the prior art, more cycles can be performed within the same time, thereby improving the test effect.

[0036] 4. Since the present invention can be tested without relying on external equipment, development costs are saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1A schematic flow chart of a test method according to a specific embodiment of the present invention;

[0038] Figure 2 Schematic diagram of the conventional hot and cold shock test method with water temperature changes in the prior art. DETAILED DESCRIPTION

[0039] The present invention is further illustrated below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0040] Test method to verify the risk of thermal fatigue cracking at the piston throat, such as Figure 1 As shown, the following steps are included:

[0041] S100. Set the engine speed to a manually preset rated speed; set the engine power to a manually preset rated power; adjust the temperature of the intake manifold to a manually preset maximum target temperature; maintain the temperature of the intake manifold at the maximum target temperature for a manually preset first target time, and then execute S200.

[0042] S200. Set the engine speed to a manually preset torque point speed; set the engine power to 0; reduce the temperature of the intake manifold to a manually preset minimum target temperature; maintain the temperature of the intake manifold at the minimum target temperature for a manually preset second target time, and then execute S300.

[0043] S300. Set the engine speed to a manually preset low idle speed; set the engine power to 0; maintain the intake manifold temperature at the lowest target temperature for a manually preset third target time, and then execute S400.

[0044] S400. Return and execute S100 until the manually preset loop exit condition is reached; the loop exit condition includes test completion and test abnormality; then perform the following operations according to the corresponding loop exit condition:

[0045] If the currently reached loop exit condition is that the test is completed, S500 is executed.

[0046] If the current cycle exit condition is a test abnormality, the machine will be stopped for inspection and the test will be exited.

[0047] S500. Disassemble and inspect the piston, and then determine the test result according to the manually preset assessment and verification method.

[0048] It should be noted that the maximum target temperature is expressed as follows:

[0049] Tmax =T1×k(1)

[0050] Where: T max It is used to represent the maximum target temperature; T1 is used to represent the maximum temperature of the intake manifold of the engine during road operation collected before the test; k is used to represent the amplification factor.

[0051] It should be noted that when the engine speed is set to the manually preset rated speed, the engine runs at full load; the temperature of the intake manifold is set to the maximum intake manifold temperature according to the road operating conditions.

[0052] In this specific embodiment, the maximum temperature of the intake manifold is 82°C; the maximum temperature of the intake manifold corresponding to different engine models may be different, and the corresponding temperature range is 75°C-85°C.

[0053] It should be further explained that the bench test simulates the worst road operating conditions.

[0054] It should be further explained that the maximum temperature of the intake manifold is the maximum temperature of the intake manifold collected under plateau conditions; the test data collected under plateau conditions may include experimental data collected under other harsh road operating conditions.

[0055] It should be further explained that the purpose of step S100 is to adjust the temperature of the intake manifold to the highest, thereby making the combustion temperature in the cylinder reach the highest and keeping the piston in a continuous heating stage.

[0056] In this specific embodiment, the value of the amplification factor is 1.2.

[0057] It should be noted that in step S200, the engine is running at zero load, the temperature of the intake manifold drops rapidly, the combustion temperature in the cylinder decreases, and the piston cools rapidly.

[0058] It should be further explained that the method for lowering the temperature of the intake manifold to the manually preset minimum target temperature is: adjust the opening of the inlet and outlet water valves of the test bench's intercooler to the maximum, and then lower the temperature of the intake manifold through the inlet and outlet water of the intercooler.

[0059] In this specific embodiment, the temperature range of the lowest target temperature is 30°C-35°C.

[0060] It should be noted that the purpose of step S300 is to keep the piston in a low temperature state and the combustion in the cylinder in a low temperature range.

[0061] In this specific embodiment, the low temperature range is 160°C-190°C.

[0062] It should be noted that the loop exit condition in S400 is the condition for the completion of the test: the number of cycles from S100 to S300 reaches 6900 times, and the cumulative cycle time reaches 300 hours.

[0063] The cycle exit condition in S400 is a test abnormality condition when: the engine leakage volume or exhaust temperature parameters show obvious abnormal fluctuations.

[0064] It should be noted that the assessment and verification method in S500 specifically includes the following steps:

[0065] S510. Disassemble and inspect the throat of the piston, and use magnetic particle inspection to check whether there are any cracks at the throat of the piston.

[0066] S520. If the inspection result of S510 shows that there is no crack at the throat of the piston, the inspection verification result is set to passed.

[0067] If the inspection result of S510 shows that there is a crack at the throat of the piston, the inspection result is set to fail.

[0068] In this specific embodiment, the first target duration is 75 seconds; the second target duration is 30 seconds; and the third target duration is 50 seconds.

[0069] Under the condition that the test engine is a 7.0-liter 350-horsepower engine:

[0070] The rated speed is 2300rpm; the rated power is 257kw; the torque point speed is 1500rpm; and the low idle speed is 550rpm.

[0071] In the foregoing detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that embodiments of the claimed subject matter require more features than are expressly recited in each claim. On the contrary, as reflected in the appended claims, the invention comprises less than all the features of any individual disclosed embodiment. The appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0072] The above description of the disclosed embodiments is intended to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments presented herein but is intended to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0073] The foregoing description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purposes of describing the above embodiments, but one of ordinary skill in the art will recognize that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to encompass all such changes, modifications and variations that fall within the scope of the appended claims. Furthermore, to the extent the term "comprising" is used in the specification or claims, the term is intended to be encompassed in a manner similar to the term "including," as explained in terms of "including," used as a transitional word in the claims. Furthermore, any use of the term "or" in the specification of the claims is intended to mean a "non-exclusive or."

[0074] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A test method for verifying the risk of thermal fatigue cracking at the piston throat, characterized by: The following steps are involved: S100. Setting the engine speed to a preset rated speed; setting the engine power to a preset rated power; adjusting the intake manifold temperature to a preset maximum target temperature; maintaining the intake manifold temperature at the maximum target temperature for a preset first target time, and then executing S200; S200. Setting the engine speed to a manually preset torque point speed; setting the engine power to 0; lowering the intake manifold temperature to a manually preset minimum target temperature; maintaining the intake manifold temperature at the minimum target temperature for a manually preset second target time, and then executing S300; S300. The engine speed is set to a manually preset low idle speed; the engine power is set to 0; the intake manifold temperature is maintained at the minimum target temperature for a manually preset third target time, and then S400 is executed; S400. Return to and execute S100 until the manually preset loop exit condition is reached; the loop exit condition includes test completion and test abnormality; then perform the following operations according to the corresponding loop exit condition: If the loop exit condition currently reached is that the test is completed, execute S500; If the cycle exit condition currently reached is a test abnormality, the machine is shut down for inspection and the test is exited; S500. Disassemble and inspect the piston, and then determine the test result according to the manually preset assessment and verification method.

2. The test method for verifying the risk of thermal fatigue cracking at the piston throat according to claim 1, characterized in that: The maximum target temperature is expressed as follows: T max =T1×k Where: T max It is used to represent the maximum target temperature; T1 is used to represent the maximum temperature of the intake manifold of the engine during road operation collected before the test; k is used to represent the amplification factor.

3. The test method for verifying the risk of thermal fatigue cracking at the piston throat according to claim 2, characterized in that: The maximum temperature of the intake manifold is the maximum temperature of the intake manifold collected under plateau conditions; the temperature range of the maximum temperature of the intake manifold is 75° C.-85° C.

4. The test method for verifying the risk of thermal fatigue cracking at the piston throat according to claim 3, characterized in that: The value of the amplification factor is 1.

2.

5. The test method for verifying the risk of thermal fatigue cracking at the piston throat according to claim 4, characterized in that: The method for lowering the temperature of the intake manifold to the manually preset minimum target temperature is: adjusting the opening of the inlet and outlet water valves of the intercooler of the test bench to the maximum, and then lowering the temperature of the intake manifold through the inlet and outlet water of the intercooler.

6. The test method for verifying the risk of thermal fatigue cracking at the piston throat according to claim 5, characterized in that: The temperature range of the minimum target temperature is 30°C-35°C.

7. The test method for verifying the risk of thermal fatigue cracking at the piston throat according to claim 6, characterized in that: The cycle exit condition in S400 is the condition for the completion of the test: the number of cycles from S100 to S300 reaches 6900 times, and the cumulative cycle time reaches 300 hours; The cycle exit condition in S400 is a test abnormality condition, which is: the engine air leakage volume or exhaust temperature parameter has obvious abnormal fluctuations.

8. The test method for verifying the risk of thermal fatigue cracking at the piston throat according to claim 7, characterized in that: The assessment and verification method in S500 specifically includes the following steps: S510. Disassemble the throat position of the piston and inspect the throat position of the piston for cracks by magnetic particle inspection; S520. If the inspection result of S510 shows that there is no crack at the throat of the piston, the assessment verification result is set to passed; If the inspection result of S510 indicates that there is a crack at the throat of the piston, the inspection result is set to fail.

9. The test method for verifying the risk of thermal fatigue cracking at the piston throat according to claim 8, characterized in that: The first target duration is 75 seconds; the second target duration is 30 seconds; and the third target duration is 50 seconds. Under the condition that the test engine is a 7.0-liter 350-horsepower engine: The rated speed is 2300 rpm; the rated power is 257 kW; the torque point speed is 1500 rpm; and the low idle speed is 550 rpm.

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