A piston thermal load analysis method, analysis system, and computer readable medium

Abstract

The present disclosure provides a piston thermal load analysis method, analysis system, and computer-readable medium. The piston thermal load analysis method includes: performing segmented time averaging on the temperature field and heat transfer coefficient obtained by CFD calculation according to the heat transfer time scale of the piston material to obtain the segmented time averaged thermal boundary conditions; and mapping the thermal boundary conditions to the FEA finite element model to perform quasi-steady-state heat transfer calculation.

Description

Technical Field

[0001] The present disclosure relates to the field of engine technology, and in particular to a piston thermal load analysis method, an analysis system, and a computer-readable medium. Background Art

[0002] With the increase of engine power density, the heat load of the core heat-receiving parts of the engine has increased significantly, which directly affects the reliability and durability of the entire engine. Therefore, the heat-receiving parts need to have a higher heat load bearing capacity. The core heat-receiving parts of marine diesel engines mainly include pistons, cylinder heads and cylinder liners. As components of the combustion chamber, they are subjected to high temperature loads for a long time, and have high requirements on the mechanical properties and deformation resistance of the materials. Among them, the piston is subjected to high temperature heat loads and a considerable mechanical load to achieve its own reciprocating motion. The working environment is extremely harsh. At the same time, a certain amount of lubricating oil is stored in the piston ring groove. Once the temperature in the ring groove is too high, the lubricating oil is easily oxidized and deteriorated, causing the heat transfer and lubrication between the piston and the cylinder liner to deteriorate sharply, seriously affecting the actual performance of the engine. In addition, during the long-term operation of the piston, more or less carbon deposits will be generated on the top of the piston. Carbon deposits have a certain degree of relief for the heat transfer from the flame in the cylinder to the piston. Therefore, the analysis of the heat load on the top of the piston is a multi-dimensional, multi-field, multi-component, and long-term subject, which is particularly important for the reliability and durability of marine diesel engines.

[0003] The key to studying the thermal load of the piston is to obtain the accurate temperature field of the piston, and the accuracy of the piston temperature field is closely related to the thermal boundary conditions of the piston, including the thermal boundary on the combustion side of the cylinder and the thermal boundary on the cooling side of the cooling cavity. At present, the calculation methods of heat transfer coefficient at home and abroad are mainly divided into the traditional "empirical formula method" and the "CFD-FEA thermal fluid-solid coupling method" based on multi-physics fields. Regarding the "empirical formula method", because the empirical formula is based on a certain limited number of models, there are inevitably errors. Moreover, with the improvement of the strengthening index of the diesel engine, the combustion environment in the diesel engine combustion chamber has undergone tremendous changes, and the heat transfer coefficient of various parts of the piston has also undergone tremendous changes, making the error even larger. Regarding the "CFD-FEA thermal fluid-solid coupling method", the current analysis of the thermal load of the piston based on the thermal fluid-solid coupling method generally uses CFD simulation software to obtain the temperature field and heat transfer coefficient of the entire working cycle of the diesel engine for time averaging, and this average thermal boundary is mapped to the FEA finite element model for steady-state heat transfer calculation. Since the time scale of the temperature field change in the engine is very small, and the cyclic average thermal boundary in this method contains a large proportion of the low-temperature intake stage, compared with the actual heating conditions of the diesel engine, the calculation using the average thermal boundary may greatly underestimate the actual piston heat load, resulting in the cooling capacity of the designed cooling system being unable to meet the piston requirements, causing reliability problems such as cylinder scuffing. Foreign scholars have considered the piston heat transfer under different working conditions and the transient heat transfer boundary of the piston changing with the crankshaft angle, and carried out a more comprehensive analysis of the piston heat load, and obtained more accurate piston temperature field data, but the transient calculation requires extremely high computer capabilities, requires complex modeling, a large number of grids, high calculation costs, and a long iteration cycle, which is quite difficult in actual engineering applications. In addition, the current analysis of piston heat load is based on the assumption that the piston surface is smooth and the lubricating oil has good properties during the heat transfer process. It does not take into account the inevitable piston carbon deposition and lubricating oil deterioration or even coking when the engine is running for a long period of time, thereby affecting the heat transfer process and piston heat load. It is difficult to effectively predict the piston heat load during long-term operation.

[0004] In summary, how to reasonably and cost-effectively perform heat load analysis on a piston running for a long period of time suitable for a temperature field variation time scale that is smaller is a difficult problem currently faced by this technical field. Summary of the invention

[0005] An object of the present disclosure is to provide a piston thermal load analysis method.

[0006] Another object of the present disclosure is to provide a piston thermal load analysis system.

[0007] Another object of the present disclosure is to provide a computer-readable medium.

[0008] According to the first aspect of the present disclosure, a piston thermal load analysis method includes: performing segmented time averaging on the temperature field and heat transfer coefficient obtained by CFD calculation according to the heat transfer time scale of the piston material to obtain the segmented time averaged thermal boundary conditions; mapping the thermal boundary conditions to an FEA finite element model to perform quasi-steady-state heat transfer calculations.

[0009] On the one hand, the above technical solution obtains the thermal boundary conditions averaged in segmented time, which has a smaller time scale than the analysis method that uses the temperature field and heat transfer coefficient of the entire working cycle for time averaging, and can more accurately measure the heat load of the piston under actual working conditions. On the other hand, the quasi-steady-state heat transfer calculation of the FEA finite element model based on the thermal boundary conditions averaged in segmented time can effectively reduce the computing power requirements, time costs, etc. compared to transient calculations.

[0010] In one or more embodiments, the temperature field and heat transfer coefficient obtained by the CFD calculation are simulation results of the in-cylinder thermal environment of a complete working cycle of the engine.

[0011] In one or more embodiments, the step of: performing segmented time averaging on the temperature field and heat transfer coefficient obtained by CFD calculation according to the heat transfer time scale of the piston material to obtain the segmented time averaged thermal boundary conditions, which includes: converting the heat transfer time scale into a crankshaft angle Δ°CA; performing segmented mapping averaging on the temperature field and heat transfer coefficient obtained by CFD calculation with the crankshaft angle Δ°CA as a step size to obtain multiple sets of thermal boundary conditions.

[0012] In one or more embodiments, the number of groups of thermal boundary conditions N = 720°CA / Δ°CA; and the step of mapping the thermal boundary conditions to the FEA finite element model for quasi-steady-state heat transfer calculations includes: setting N time steps, corresponding to the N groups of thermal boundary conditions, assigning the thermal boundary conditions to each time step in turn, and performing steady-state heat transfer calculations.

[0013] In one or more embodiments, the analysis method further comprises: correcting the heat transfer coefficient according to the influence of carbon deposits on the piston top of the piston on heat transfer.

[0014] In one or more embodiments, the step of: correcting the heat transfer coefficient according to the effect of carbon deposits on the piston top of the piston on heat transfer is achieved through a steady-state heat transfer test, including: coating carbon deposits of different thicknesses on the piston top of the piston specimen; simulating the thermal environment in the cylinder; measuring the temperature distribution, and calculating the heat transfer system under the conditions of carbon deposits of different thicknesses.

[0015] In one or more embodiments, the analysis method further comprises: correcting the heat transfer coefficient according to the influence of lubricating oil oxidation and deterioration on the piston-cylinder liner wall on heat transfer.

[0016] In one or more embodiments, the step of: correcting the heat transfer coefficient according to the effect of lubricating oil oxidation and deterioration on the piston-cylinder liner wall on heat transfer is achieved through a steady-state heat transfer test, including: applying lubricating oil of different operating time between the piston specimen and the cylinder liner specimen wall; simulating the thermal environment in the cylinder; measuring the temperature distribution, and calculating the heat transfer coefficient under the lubricating oil conditions of different operating time.

[0017] According to the second aspect of the present application, a piston thermal load analysis system comprises: a memory for storing a computer program; and a processor for executing the computer program to implement the steps of the above-mentioned analysis method.

[0018] In one or more embodiments, the analysis system also includes a steady-state heat transfer test bench, which includes: a cylinder head specimen, a heating device, a cylinder liner specimen, a piston specimen, and a piston ring specimen, which are used to simulate the thermal environment in the cylinder; and a temperature measuring unit, which is used to measure temperature distribution.

[0019] A computer-readable storage medium according to the third aspect of the present application is characterized in that the computer-readable storage medium stores a computer program, and the computer program can be executed by a processor to implement the steps of the above-mentioned analysis method. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other features, properties and advantages of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings and embodiments. In the accompanying drawings, the same reference numerals always represent the same features. It should be noted that these drawings are only examples and are not drawn according to the conditions of equal scale, and should not be used as a limitation on the actual scope of protection claimed by the present disclosure, wherein:

[0021] Figure 1 FIG. 4 is a flow chart of a piston thermal load analysis method according to an embodiment.

[0022] Figure 2 Schematic diagram of the structure of a steady-state heat transfer test bench according to an embodiment.

[0023] Figure 3 Schematic diagram of the arrangement of temperature measurement points of a piston specimen according to an embodiment.

[0024] Figure 4 Schematic diagram of the arrangement of temperature measurement points between cylinder liner specimens in one embodiment.

[0025] Figure 5 The figure is a flow chart of a method for analyzing a long-period thermal load of a piston according to an embodiment.

[0026] Reference numerals:

[0027] 1. Cylinder head test piece; 2. Heating device, 3. Cylinder liner test piece; 4. Piston test piece; 41. Piston top; 42. Piston top center position; 43. Throat position; 44. Edge position; 45. Piston ring groove; 5. Piston ring test piece; 6. Heating rod (or flame). DETAILED DESCRIPTION

[0028] Reference will now be made in detail to various embodiments of the present disclosure, examples of which are shown in the accompanying drawings and described below. Although the present disclosure will be described in conjunction with the exemplary embodiments, it should be appreciated that the present disclosure is not intended to be limited to those exemplary embodiments. On the contrary, the present disclosure is intended to cover not only these exemplary embodiments, but also various alternative forms, modifications, equivalent forms and other embodiments that may be included within the spirit and scope of the present disclosure as defined by the appended claims.

[0029] The present disclosure uses specific words to describe the embodiments of the present disclosure. For example, "one embodiment" and / or "an embodiment" means a certain feature, structure or characteristic related to at least one embodiment of the present disclosure. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" mentioned twice or more in different locations in the present disclosure does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of the present disclosure can be appropriately combined.

[0030] In the following description, the orientation or positional relationship indicated by "upper", "lower", "inner", "outer", "front", "back", or other orientation terms is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present disclosure and simplifying the description, and does not indicate or imply that the device or component referred to must have a specific orientation, be constructed and / or implemented in a specific orientation, and therefore cannot be understood as limiting the present disclosure. In the present disclosure, the terms "first", "second", etc. are only used for distinguishing descriptions, and cannot be understood as indicating or implying a positional relationship or an order of importance.

[0031] The present disclosure uses flowcharts to illustrate the operations performed according to the embodiments of the present disclosure. It should be appreciated that, according to actual conditions, the operations may not necessarily be performed in the order of the steps shown in the diagram, and other operations may be added to these processes, or one or more operations may be removed from these processes.

[0032] In the present disclosure, “CFD (Computational Fluid Dynamics)” refers to computational fluid dynamics simulation technology, and “FEA (Finite Element Analysis)” refers to finite element analysis method.

[0033] It can be understood that the analysis method, analysis system, and computer-readable medium described in the present disclosure are applicable to the design of marine diesel engines, but are not limited thereto and can also be applied to other occasions requiring piston thermal load analysis.

[0034] As mentioned above, the time scale of the temperature field change in the engine is very small, and the existing analysis method of calculating the temperature field and heat transfer coefficient of the entire working cycle of the engine through CFD simulation software for time averaging, because it includes a large proportion of low-temperature intake stage, compared with the actual heating conditions of the engine, it may greatly underestimate the actual piston heat load, which will lead to the cooling system design being unable to meet the needs, causing reliability problems such as cylinder pulling; on the other hand, the existing analysis method using transient heat transfer calculation has extremely high requirements on computer capabilities, requires complex modeling, a large number of grids, high calculation costs, and long iteration cycles, which are quite difficult in actual engineering applications; in addition, it is necessary to further develop heat load analysis methods under long-cycle piston operation conditions, especially under conditions of carbon deposits and lubricating oil deterioration.

[0035] Based on the above considerations, the inventors have conducted in-depth research and proposed a piston thermal load analysis method, which includes: performing segmented time averaging on the temperature field and heat transfer coefficient obtained by CFD calculation according to the heat transfer time scale of the piston material to obtain the segmented time average thermal boundary conditions; mapping the thermal boundary conditions to the FEA finite element model for quasi-steady-state heat transfer calculation. The quasi-steady-state heat transfer calculation refers to a heat transfer calculation performed using the segmented time average thermal boundary conditions, which is different from the thermal boundary conditions obtained by averaging the entire working cycle time and the transient thermal boundary conditions.

[0036] Specifically, the heat transfer time scale of the piston material can be obtained through investigation or calculation; the temperature field and heat transfer coefficient obtained by the CFD calculation include thermal boundary CFD calculation of the thermodynamic side and cooling side of the piston, the thermal boundary CFD calculation of the thermal side is to obtain the temperature and heat transfer coefficient distribution of the piston top through simulation calculation of the combustion process in the cylinder, and the thermal boundary CFD calculation of the cooling side of the piston is to obtain the temperature and heat transfer coefficient distribution of the piston cooling oil cavity wall through multiphase flow simulation calculation of the oscillating cooling oil cavity inside the piston; the thermal boundary conditions of the piston are obtained by segmented time averaging the temperature and heat transfer coefficient distribution of the thermodynamic side and the cooling side, and mapped accordingly to the thermodynamic side and cooling side of the FEA finite element model for heat transfer calculation; the FEA finite element model can be established according to the geometric model of the engine piston.

[0037] On the one hand, the quasi-steady-state CFD-FEA thermal fluid-solid coupling analysis method fully considers the heat transfer effect of the piston material and the small time scale of the engine temperature field change by obtaining the segmented time-averaged thermal boundary conditions. Compared with the analysis method that uses the temperature field and heat transfer coefficient of the entire working cycle for time averaging, it can more accurately measure the thermal load of the piston under actual working conditions; on the other hand, the quasi-steady-state heat transfer calculation of the FEA finite element model is performed with the segmented time-averaged thermal boundary conditions. While considering different thermal boundary conditions, it can effectively save computing power costs, time costs, etc. compared to transient calculations.

[0038] In one or more embodiments, the temperature field and heat transfer coefficient obtained by the CFD calculation are simulation results of the in-cylinder thermal environment of a complete working cycle of the engine. In this way, simulation calculation of the in-cylinder thermal environment changes of the entire working cycle makes the analysis results more accurate.

[0039] In one or more embodiments, the step of: performing segmented time averaging on the temperature field and heat transfer coefficient obtained by CFD calculation according to the heat transfer time scale of the piston material to obtain the segmented time averaged thermal boundary conditions includes: converting the heat transfer time scale into a crankshaft angle Δ°CA; performing segmented mapping averaging on the temperature field and heat transfer coefficient obtained by CFD calculation with the crankshaft angle Δ°CA as a step size to obtain multiple groups of thermal boundary conditions. This provides an analysis method with strong operability and applicability.

[0040] In one or more embodiments, the number of groups of thermal boundary conditions N = 720°CA / Δ°CA; and the step of mapping the thermal boundary conditions to the FEA finite element model for quasi-steady-state heat transfer calculation includes: setting N time steps, corresponding to the N groups of thermal boundary conditions, assigning the thermal boundary conditions to each time step in turn, and performing steady-state heat transfer calculation. This is suitable for simulation calculation of a complete working cycle of the piston.

[0041] In one or more embodiments, the analysis method further comprises: correcting the heat transfer coefficient according to the influence of carbon deposits on the piston top of the piston on heat transfer.

[0042] By introducing the effect of carbon deposition on the piston top on heat transfer and correcting the heat transfer coefficient, a more reliable piston top simulation calculation boundary can be provided for the quasi-steady-state CFD-FEA thermal-fluid-solid coupling analysis method, making the analysis method more accurate in measuring and analyzing the piston under long-cycle operating conditions.

[0043] In one or more embodiments, the step of: correcting the heat transfer coefficient according to the effect of carbon deposits on the piston top of the piston on heat transfer is achieved through a steady-state heat transfer test, including: coating carbon deposits of different thicknesses on the piston top 41 of the piston specimen 4; simulating the thermal environment in the cylinder; measuring the temperature distribution, and calculating the heat transfer system under the conditions of carbon deposits of different thicknesses.

[0044] Specifically, the carbon deposit on the piston top 41 can be the carbon powder produced by comparing the results of carbon deposit composition analysis and density analysis on the actual piston top wall. The piston top carbon deposit test can determine the temperature measurement point position according to the focus position; for example, holes are drilled at the wall and the depth h below the wall at the center position 42, throat position 43 and edge position 44 of the piston top 41, and high-frequency thermocouple measurement points are arranged to measure the temperature at different positions of the wall of the piston test piece 4 and calculate the heat transfer coefficient; the depth h can be 1mm; according to the different thicknesses of carbon on the top wall of the actual engine piston, the piston top 41 of the piston test piece 4 is coated with carbon deposits, and the piston test piece 4 is fixed at a specific position, and the cylinder is heated by a high-power heating rod 6 or fuel combustion to simulate the thermal environment in the cylinder of the actual engine, and the influence of carbon deposits of different thicknesses on the heat transfer coefficient of the piston top 41 is studied.

[0045] In one or more embodiments, the analysis method further comprises: correcting the heat transfer coefficient according to the heat transfer effect of the lubricating oil oxidation and deterioration between the piston and the cylinder liner wall.

[0046] By introducing the heat transfer effect of lubricating oil oxidation and deterioration between the piston and the cylinder liner wall to correct the heat transfer coefficient, a more reliable piston-piston ring-cylinder liner simulation calculation boundary can be provided for the analysis method, making the measurement and prediction of the piston under long-cycle operating conditions by the analysis method more accurate.

[0047] In one or more embodiments, the step of: correcting the heat transfer coefficient according to the heat transfer effect of the lubricating oil oxidation and deterioration between the piston and the cylinder liner wall is achieved through a steady-state heat transfer test, including: simulating the thermal environment in the cylinder; applying lubricating oil of different operating time between the piston specimen 4 and the cylinder liner specimen 3 wall; measuring the temperature distribution, and calculating the heat transfer coefficient under the lubricating oil conditions of different operating time.

[0048] Specifically, the test of the influence of oxidation and deterioration of the piston-cylinder liner lubricating oil on the heat transfer of the piston can determine the position of the temperature measuring point according to the key focus position; for example, holes are drilled at the depth h below the wall of the piston ring groove 45, the piston top bank 41 where the cylinder liner specimen 3 is flush with the piston specimen 4, the middle part between the piston ring 5, and the wall and the depth s below the wall, and high-frequency thermocouple measuring points are arranged to measure the temperature at different positions inside the cylinder liner specimen 3 and calculate the heat transfer coefficient; the depth s can be 1mm; optionally, the lubricating oil is the new lubricating oil of the actual engine, the lubricating oil that has been running for 500 hours, and the lubricating oil that has been running for 1000 hours. On the engine steady-state heat transfer bench, the inner side of the cylinder liner specimen 3 used in the test is coated with lubricating oil of different engine running times, and assembled with the piston specimen 4 and the piston ring specimen 5. The cylinder is heated by a high-power heating rod 6 or fuel combustion to simulate the thermal environment in the cylinder of the actual engine, and the influence of lubricating oil with different oxidation and deterioration degrees on the heat transfer coefficient of the top of the piston specimen 4 is studied.

[0049] According to the second aspect of the present application, a piston thermal load analysis system comprises: a memory for storing a computer program; a processor for executing the computer program to implement the steps of the above analysis method; please refer to the above description for details, which will not be repeated here.

[0050] In one or more embodiments, the analysis system further includes a steady-state heat transfer test bench, which includes: a cylinder head specimen 1, a heating device 2, a cylinder liner specimen 3, a piston specimen 4, and a piston ring specimen 5, which are used to simulate the thermal environment in the cylinder; and a temperature measuring unit, which is used to measure the temperature distribution. The cylinder head specimen 1, the cylinder liner specimen 3, the piston specimen 4, and the piston ring specimen 5 may have a structure and assembly relationship similar to the corresponding actual engine components to simulate the actual working environment, which will not be repeated here; optionally, the heating device 2 uses fuel combustion to generate a heating flame, or uses a heating rod 6 to simulate the thermal environment in the cylinder of an actual engine; the temperature measuring unit may use a high-frequency thermocouple.

[0051] Optionally, the temperature measuring point positions of the cylinder liner specimen 3 are determined according to the key focus positions, and holes are drilled at the corresponding wall surfaces and at a certain depth in the wall surfaces for arranging the high-frequency thermocouples; the measuring point positions may include: holes are drilled at the wall surfaces and the depth h below the wall surfaces at the center position 42 of the piston top 41, the throat position 43 and the edge position 44, the depth h below the wall surfaces, and the avoided depth s of the piston ring groove 45, as well as at the wall surfaces and the depth s below the wall surfaces at the middle part between the cylinder liner specimen 3 flush with the piston specimen top bank 4, the piston ring groove 45, and the piston ring specimen 5; the depth h and the depth s may both be 1 mm.

[0052] The steady-state heat transfer test bench designed in this way can meet the needs of the test analysis method of the influence of carbon deposits on the piston top on the thermal load, and can also meet the needs of the test analysis method of the influence of oxidation and deterioration of the piston-cylinder liner lubricating oil on the thermal load. At this time, the test can be to turn on the heating device 2 to make the flame in the cylinder or the heating rod 6 heat up, simulate the thermal environment in the cylinder of the actual engine, and carry out the heat transfer test of the piston top 41 coated with carbon deposits of different thicknesses and / or the heat transfer test of the cylinder liner coated with lubricating oil of different operating times, respectively, and measure the temperature by high-frequency thermocouples to calculate the heat transfer coefficient under the conditions of coating carbon deposits of different thicknesses and / or lubricating oil of different operating times; the heat transfer coefficient distribution obtained from the steady-state heat transfer test of the piston top carbon deposits and / or the oxidation and deterioration of the piston-cylinder liner lubricating oil is assigned to the piston top and the piston-cylinder liner wall of the FEA finite element model, so as to correct the thermal boundary of the piston under the conditions of different thicknesses of carbon deposits and / or different operating times of lubricating oil, and perform steady-state heat transfer calculation.

[0053] In one or more embodiments, the analysis system further comprises a database having at least one thermal load analysis result corresponding to the piston. Optionally, the database further comprises a thermal load analysis result corresponding to the piston and corresponding to at least one of the piston material, carbon deposits of different thicknesses, and different degrees of lubricating oil oxidation deterioration between the piston and the cylinder liner wall.

[0054] It should be noted that the above-mentioned memory, processor, and database are not limited to a specific memory, processor, or database. For example, in some cases, both the memory and the processor can have a distributed structure. For example, they can include a memory and a processor located on the test equipment side and the backend cloud, respectively, and the above-mentioned analysis method is jointly implemented by the test equipment side and the backend cloud. Furthermore, in an embodiment adopting a distributed structure, each step can adjust the specific execution terminal according to actual conditions, and the specific scheme of each step implemented in a specific terminal should not limit the scope of protection of the present invention.

[0055] A computer-readable storage medium according to the third aspect of the present application is characterized in that the computer-readable storage medium stores a computer program, and the computer program can be executed by a processor to implement the steps of the above-mentioned analysis method; please refer to the above description for details, which will not be repeated here.

[0056] In addition, it can be understood that the above-mentioned computer-readable storage medium can also be in a system form, that is, it includes multiple computer-readable storage sub-media, so as to jointly implement the steps of the analysis method described above through multiple computer-readable storage media.

[0057] In summary, the advanced technical effects of the present disclosure include but are not limited to at least one of the following:

[0058] 1. On the one hand, the quasi-steady-state CFD-FEA thermal fluid-solid coupling analysis method fully considers the heat transfer effect of the piston material and the small time scale of the engine temperature field change by obtaining the segmented time-averaged thermal boundary conditions. Compared with the analysis method that uses the temperature field and heat transfer coefficient of the entire working cycle for time averaging, it can more accurately measure the heat load of the piston under actual working conditions; on the other hand, the quasi-steady-state heat transfer calculation of the FEA finite element model is performed with the segmented time-averaged thermal boundary conditions. While considering different thermal boundary conditions, it can effectively save computing power costs, time costs, etc. compared with transient calculations.

[0059] 2. By introducing the effect of carbon deposition on the piston top on heat transfer and correcting the heat transfer coefficient, a more reliable piston top simulation calculation boundary can be provided for the quasi-steady-state CFD-FEA thermal-fluid-solid coupling analysis method, making the analysis method more accurate in measuring and predicting the piston under long-cycle operating conditions.

[0060] 3. By introducing the heat transfer effect of lubricating oil oxidation and deterioration between the piston and the cylinder liner wall to correct the heat transfer coefficient, a more reliable piston-piston ring-cylinder liner simulation calculation boundary can be provided for the analysis method, making the measurement and prediction of the piston under long-cycle operating conditions by the analysis method more accurate.

[0061] The various illustrative logic modules and circuits described in conjunction with the embodiments of the present disclosure may be implemented or executed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general purpose processor may be a microprocessor, but in an alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in cooperation with a DSP core, or any other such configuration.

[0062] The steps of the method or algorithm described in conjunction with the embodiments of the present disclosure may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor so that the processor can read and write information from / to the storage medium. In an alternative, a storage medium may be integrated into a processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In an alternative, the processor and the storage medium may reside in a user terminal as discrete components.

[0063] In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented as a computer program product in software, each function may be stored on or transmitted by a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, including any media that facilitates the transfer of a computer program from one place to another. Storage media may be any available media that can be accessed by a computer. As an example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of an instruction or data structure and can be accessed by a computer. Any connection is also properly referred to as a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwaves are included in the definition of the medium. Disk and disc as used herein include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wherein disk often reproduces data magnetically, while disc reproduces data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0064] Although the present disclosure is disclosed as above with preferred embodiments, it is not intended to limit the present disclosure, and any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, any modification, equivalent change and modification made to the above embodiments based on the technical essence of the present disclosure without departing from the content of the technical solution of the present disclosure shall fall within the protection scope defined by the claims of the present disclosure.

Claims

1. A piston thermal load analysis method, characterized in that: include: Performing segmented time averaging on the temperature field and heat transfer coefficient obtained by CFD calculation according to the heat transfer time scale of the piston material to obtain segmented time averaging thermal boundary conditions; The thermal boundary conditions are mapped to the FEA finite element model for quasi-steady-state heat transfer calculation.

2. The analysis method according to claim 1, characterized in that The temperature field and heat transfer coefficient obtained by the CFD calculation are simulation results of the in-cylinder thermal environment of a complete working cycle of the engine.

3. The analysis method according to claim 1, characterized in that The step of performing segmented time averaging on the temperature field and heat transfer coefficient obtained by CFD calculation according to the heat transfer time scale of the piston material to obtain the segmented time averaged thermal boundary conditions includes: The heat transfer time scale is converted into a crankshaft angle Δ°CA; The temperature field and heat transfer coefficient obtained by the CFD calculation are segmented and averaged with the crankshaft angle Δ°CA as a step size to obtain multiple groups of thermal boundary conditions.

4. The analysis method according to claim 3, characterized in that The number of groups of thermal boundary conditions N=720°CA / Δ°CA; Furthermore, the step of mapping the thermal boundary conditions to the FEA finite element model for quasi-steady-state heat transfer calculation includes: N time steps are set, corresponding to N groups of thermal boundary conditions, the thermal boundary conditions are sequentially assigned to each time step, and steady-state heat transfer calculations are performed.

5. The analysis method according to claim 1, characterized in that Also includes: The heat transfer coefficient is corrected according to the influence of carbon deposits on the piston top of the piston on the heat transfer.

6. The analysis method according to claim 5, characterized in that The step of correcting the heat transfer coefficient according to the influence of carbon deposits on the piston top of the piston on the heat transfer is achieved through a steady-state heat transfer test, and includes: Coating different thicknesses of carbon deposits on the piston top of the piston test piece; Simulate the thermal environment in the cylinder; The temperature distribution is measured, and the heat transfer coefficient under the conditions of carbon deposits of different thicknesses is calculated.

7. The analysis method according to claim 1, characterized in that Also includes: The heat transfer coefficient is corrected according to the influence of lubricating oil oxidation and deterioration on the piston-cylinder liner wall on heat transfer.

8. The analysis method according to claim 7, characterized in that The step of correcting the heat transfer coefficient according to the influence of lubricating oil oxidation and deterioration on the piston-cylinder liner wall on heat transfer is achieved through a steady-state heat transfer test, including: Lubricating oil with different running times is applied between the piston test piece and the wall surface of the cylinder liner test piece; Simulate the thermal environment in the cylinder; The temperature distribution is measured and the heat transfer coefficient is calculated under the lubricating oil conditions at different operating times.

9. A piston thermal load analysis system, characterized in that: include: Memory for storing computer programs; A processor, configured to execute the computer program to implement the analysis method according to any one of claims 1 to 8.

10. The analysis system according to claim 9, characterized in that Also included is a steady-state heat transfer test bench, the steady-state heat transfer test bench comprising: Cylinder head test piece, heating device, cylinder liner test piece, piston test piece, and piston ring test piece are used to simulate the thermal environment in the cylinder; The temperature measuring unit is used to measure the temperature distribution.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and the computer program can be executed by a processor to implement the steps of the analysis method according to any one of claims 1 to 8.

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