Structural design method and device for engine connecting rod bearing lubricating oil film cavitation erosion inhibition

Abstract

The invention discloses a structural design method and device for engine connecting rod bearing lubricating oil film cavitation erosion inhibition, and the method comprises the steps: 1, selecting a connecting rod bearing of a diesel engine as an object, building a geometric model of a lubricating oil film between bearings, introducing the built geometric model into a pre-built external flow field, and obtaining a corresponding flow field physical model; 2, simulating the flow field physical model by adopting a numerical simulation method to obtain gas phase volume fraction and oil film pressure distribution data; 3, the bearing bush grooving method of the diesel engine is changed, and the step 1 and the step 2 are repeated; 4, analyzing the engine connecting rod bearing lubricating oil film cavitation simulation result to obtain the change rule of the cavitation degree under different bearing bush grooving methods; and 5, a bearing bush slotting method for the selected diesel engine connecting rod bearing is established. According to the method, the optimal bearing bush slotting mode is compared and selected through a numerical simulation method to achieve the purpose of engine connecting rod bearing lubricating oil film cavitation erosion inhibition.

Description

Technical Field

[0001] The invention relates to the field of engine cavitation suppression, and in particular to a structural design method and device for suppressing cavitation erosion of lubricating oil film of engine connecting rod bearing. Background Art

[0002] The engine connecting rod bearing is one of the key components of the engine, and its lubrication performance directly affects the working efficiency and life of the engine. In a high-speed engine, the connecting rod bearing lubricating oil film is prone to cavitation, which can cause bearing surface damage, reduce the service life of the bearing, and even cause engine failure in severe cases. Therefore, it is of great practical significance to explore the cavitation mechanism that occurs during the lubrication of the connecting rod bearing, predict the reliability and life of the connecting rod bearing, and propose feasible suppression schemes. Traditional bearing design methods mainly focus on improving load-bearing capacity and reducing friction, and the consideration of cavitation problems is relatively insufficient. Existing cavitation suppression methods are mostly focused on changing the properties of lubricating oil or adjusting working parameters, while there is less research on bearing structure design, and the cavitation suppression strategies proposed in previous studies are difficult to be effectively promoted and applied for different types of diesel engines. In particular, as a commonly used bearing structure optimization method, bearing slotting has not been effectively applied in diesel engine connecting rod bearing cavitation suppression. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a structural design method and device for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing, and the method is verified by numerical simulation.

[0004] The object of the present invention is achieved through the following technical solutions: A structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing, comprising:

[0005] Step 1: Select the connecting rod bearing of the diesel engine as the object, extract the lubricating oil film between the bearings and establish the corresponding geometric model, introduce the established geometric model into the pre-constructed external flow field, and obtain the corresponding flow field physical model;

[0006] Step 2: Use numerical simulation method to simulate the flow field physical model to obtain gas phase volume fraction and oil film pressure distribution data;

[0007] Step 3, changing the slotting method of the bearing shell of the selected diesel engine, including selecting different slotting forms, slotting depths and quantities, and repeating steps 1 and 2;

[0008] Step 4: Analyze the simulation results of the cavitation erosion of the lubricating oil film of the engine connecting rod bearing according to the gas phase volume fraction and oil film pressure distribution data obtained by different bearing slotting methods, and obtain the variation law of the cavitation degree under different bearing slotting methods;

[0009] Step 5: According to the analysis results of step 4, select the bearing grooving method for the selected diesel engine connecting rod bearing.

[0010] The present invention finds through numerical simulation that changing the bearing bushing slotting method, especially increasing the number of slots and the slot depth and using a half-slot model, can significantly reduce the degree of cavitation of the connecting rod bearing lubricating oil film and further improve the operating reliability and service life of the diesel engine.

[0011] Specifically, in step 1, the geometric model includes a bearing shell, a journal and an oil inlet at a connecting rod bearing.

[0012] Specifically, in step 1, the external flow field includes a pressure inlet of the journal oil inlet, a pressure outlet on both side end surfaces of the bearing gap, and a rotating surface for restoring the relative rotational motion between the journal and the bearing shell.

[0013] Specifically, in step 2, the numerical simulation method includes using the Singhal cavitation model and the moving mesh technology.

[0014] Specifically, in step 2, the gas phase volume fraction and oil film pressure distribution data include the oil film gas phase volume fraction peak value, oil film pressure peak value change data with time, and the oil film gas phase volume fraction and oil film pressure distribution data along the circumferential position.

[0015] Specifically, in step 3, the bearing grooving method includes three different grooving modes: single groove, double groove, and triple groove, four different oil groove depths, and three groove shapes: no groove, half groove, and full groove.

[0016] Specifically, in step 4, the variation of the cavitation degree under different bearing grooving methods refers to the influence of the number of grooves, oil groove depth, and groove shape on the oil film gas phase volume fraction and oil film pressure distribution.

[0017] Specifically, in step 5, a method for grooving the bearing shell of the diesel engine connecting rod bearing is selected according to the results of steps 3 and 4.

[0018] In a second aspect, the present invention also provides a structural design device for suppressing cavitation erosion of the lubricating oil film of an engine connecting rod bearing, comprising a memory and one or more processors, wherein the memory stores executable code, and when the processor executes the executable code, the structural design method for suppressing cavitation erosion of the lubricating oil film of an engine connecting rod bearing is implemented.

[0019] In a third aspect, the present invention further provides a computer-readable storage medium having a program stored thereon, and when the program is executed by a processor, the structural design method for suppressing cavitation erosion of the lubricating oil film of an engine connecting rod bearing is implemented.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention realizes accurate prediction of the cavitation condition of the lubricating oil film of the engine connecting rod bearing under different bearing grooving methods by means of numerical simulation.

[0022] (2) The present invention provides a strategy for suppressing lubricating oil film cavitation by changing the bearing grooving method, specifically increasing the number of grooves, the groove depth and using a half-groove model, thereby providing a new method for structural design to suppress diesel engine cavitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of a structural design method for inhibiting cavitation erosion of lubricating oil film of an engine connecting rod bearing provided by the present invention;

[0024] Figure 2 A schematic diagram of the geometric model and flow field physical model provided in this embodiment, Figure 2 (a) in the figure corresponds to a two-dimensional geometric model. Figure 2 (b) corresponds to the schematic diagram of the three-dimensional flow field;

[0025] Figure 3 Temperature and pressure distribution cloud diagrams using three different cavitation models provided for this embodiment;

[0026] Figure 4 Schematic diagram of different bearing grooving methods provided in this embodiment, Figure 4 (a) in the figure corresponds to the schematic diagram of the groove depth. Figure 4 (b) in the figure corresponds to a schematic diagram of different slot numbers. Figure 4 (c) in the figure corresponds to schematic diagrams of different groove shapes;

[0027] Figure 5 The distribution diagram of the oil film gas phase volume fraction along the circumferential position and the distribution diagram of the oil film pressure along the circumferential position corresponding to different groove numbers provided in this embodiment are as follows: Figure 5 (a) corresponds to the distribution diagram of the oil film gas phase volume fraction along the circumferential position. Figure 5 (b) corresponds to the distribution diagram of oil film pressure along the circumferential direction;

[0028] Figure 6 The distribution diagram of the oil film gas phase volume fraction along the circumferential position and the distribution diagram of the oil film pressure along the circumferential position corresponding to different groove depths provided in this embodiment are: Figure 6 (a) corresponds to the distribution diagram of the oil film gas phase volume fraction along the circumferential position. Figure 6 (b) corresponds to the distribution diagram of the oil film pressure along the circumferential position;

[0029] Figure 7The distribution diagram of the oil film gas phase volume fraction along the circumferential position and the distribution diagram of the oil film pressure along the circumferential position corresponding to the different groove shapes provided in this embodiment are as follows: Figure 7 (a) corresponds to the distribution diagram of the oil film gas phase volume fraction along the circumferential position. Figure 7 (b) corresponds to the distribution diagram of the oil film pressure along the circumferential position;

[0030] Figure 8 The present invention is a structural diagram of a structural design device for inhibiting cavitation erosion of lubricating oil film of an engine connecting rod bearing. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the embodiments and the accompanying drawings. It should be noted that the description of specific parameters is only exemplary and is not intended to limit the scope of the present invention. In addition, the present invention does not focus on simulation algorithms and specific mechanisms, so the parts involving specific calculation methods and mechanism analysis are not described in detail.

[0032] like Figure 1 As shown, the present invention provides a structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing, comprising:

[0033] Step 1: Figure 2 As shown, the lubricating oil film between the bearings is extracted and the corresponding geometric model is established including: oil inlet 1, journal 2 and bearing shell 3. Figure 2 The two-dimensional schematic diagram of the bearing slotting method without slots shown in (a) shows the relative motion setting of the connecting rod bearing. Considering rotation and translation, the journal radius r = 47.955mm, the bearing radius R = 48.005mm, and the circular oil inlet diameter d = 7mm. In order to restore the relative motion between the journal and the bearing, the journal surface in the oil film model is set to linear motion along the -45° and 135° directions by editing the user-defined file. Among them, the movement speed of the journal is 0.72mm / s, and the minimum oil film gap thickness varies in the range of 1μm to 500μm. This process corresponds to the process of the connecting rod big end bearing rotating and approaching and moving away from the journal under the action of radial load at different strokes of the diesel engine. Figure 2 (b) in the figure is a schematic diagram of the three-dimensional flow field established according to the geometric model. The oil inlet 1 corresponds to the pressure inlet boundary, the surface of the journal 2 is a solid wall boundary and performs translational motion, the surface of the bearing 3 is a rotating surface (moving wall), the rotation speed is 1800rpm, the temperature of the bearing surface is 140℃, the end faces 4 on both sides of the bearing clearance are set as pressure outlets, the gauge pressure is 0Pa, the flow field liquid is a lubricating oil film, and the lubricating oil inlet temperature is 110℃.

[0034] Step 2: During the numerical simulation, Figure 3As shown in the figure, the accuracy of three different cavitation models, namely the Singhal model, the Schnerr and Sauer model and the Zwart-Gerber-Belamri model, in calculating the cavitation of lubricating oil films is compared. Finally, the Singhal model is selected as the cavitation model used in this paper to carry out numerical simulation calculations. In this model, the bubbles that move with the fluid and have no speed difference with the fluid are described by the Rayleigh-Plesset equation. A dynamic grid is used to simulate the translation (bearing clearance change) and rotation (bearing rotation) during bearing lubrication. Numerical simulations are performed on different working conditions to obtain the data on the change of the peak value of the oil film gas phase volume fraction and the peak value of the oil film pressure over time, and the distribution data of the oil film gas phase volume fraction and the oil film pressure along the circumferential position.

[0035] Step 3: Figure 4 As shown, different bearing grooving methods include: no groove, single groove, double groove, triple groove, four different grooving methods, corresponding groove widths are d1 = 4mm, d2 = 2mm, d3 = 1.33mm, four different oil groove depths h are 0.5mm, 1mm, 1.5mm and 2mm, and three groove shapes are no groove, half groove, and full groove. Repeat steps 1 and 2 under different bearing grooving methods.

[0036] Step 4: Analyze the simulation results of the lubricating oil film cavitation of the engine connecting rod bearing, such as Figure 5 As shown in the figure, the comparison of the circumferential gas volume fraction and the circumferential pressure under different slotting conditions is listed, where the gas volume fraction and pressure are averaged along the axial direction of the oil film. It can be seen from the figure that slotting can significantly reduce the size of the gas volume fraction and the range of oil film cavitation. Under the condition of a certain total width of the slot, the increase in the number of slots can further improve the effect of alleviating cavitation, but the degree of improvement gradually weakens. For the pressure distribution of the oil film, it can be found that compared with the no-slot model, slotting can effectively reduce the oil film pressure. Among them, the single-slot and three-slot models are more effective in reducing the oil film pressure, and the slotting here can control the peak pressure to a certain extent. Figure 6 The distribution of the gas phase volume fraction of the oil film and the pressure along the circumferential position of different groove depths is given. With the increase of the groove depth, the range and degree of cavitation are reduced to a certain extent, but the overall improvement is limited. The effect of alleviating cavitation from no groove to 1mm groove is significantly higher than the effect of improving from 1mm groove to 2mm groove. The groove depth of 0.5-1mm can significantly improve the pressure peak and cavitation fraction at the minimum oil film gap inside the bearing, achieving the effect of inhibiting cavitation. Figure 7As shown in the figure, the maximum gas volume fractions of the three models of no groove, half groove and full groove are 0.94, 0.61 and 0.39 respectively. Compared with the no groove model, the half groove model reduces the maximum gas volume fraction by 58.51%. The half groove and full groove models have similar effects on improving the pressure at the minimum oil film gap inside the bearing.

[0037] Step 5. Based on the variation of the cavitation degree obtained in step 4 under different bearing grooving methods, a bearing grooving method for the selected diesel engine connecting rod bearing can be established. Increasing the number of grooves and the groove depth can improve the suppression effect, but with the further increase in the number of oil grooves and the depth of the oil grooves, the degree of improvement gradually decreases. In general, selecting a single groove or three grooves in a semi-ring with an appropriate groove depth can effectively suppress the cavitation phenomenon of the oil film during the movement of the bearing.

[0038] Corresponding to the aforementioned embodiment of a structural design method for suppressing cavitation erosion of a lubricating oil film of an engine connecting rod bearing, the present invention also provides an embodiment of a structural design device for suppressing cavitation erosion of a lubricating oil film of an engine connecting rod bearing.

[0039] See also Figure 8 A structural design device for suppressing cavitation erosion of lubricating oil film of engine connecting rod bearing provided by an embodiment of the present invention comprises a memory and one or more processors, wherein the memory stores executable code, and when the processor executes the executable code, it is used to implement a structural design method for suppressing cavitation erosion of lubricating oil film of engine connecting rod bearing in the above embodiment.

[0040] An embodiment of a structural design device for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing provided by the present invention can be applied to any device with data processing capability, and the device with data processing capability can be a device or apparatus such as a computer. The device embodiment can be implemented through software, or through hardware or a combination of software and hardware. Taking software implementation as an example, as a device in a logical sense, it is formed by the processor of any device with data processing capability in which it is located reading the corresponding computer program instructions in the non-volatile memory into the internal memory for execution. From the hardware level, if Figure 8 As shown, it is a hardware structure diagram of any device with data processing capability where a structural design device for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing provided by the present invention is located, except Figure 8 In addition to the processor, memory, network interface, and non-volatile memory shown, any device with data processing capabilities in which the apparatus in the embodiments is located may also include other hardware, generally based on the actual functions of the device with data processing capabilities, which will not be described in detail.

[0041] The implementation process of the functions and effects of each unit in the above-mentioned device is specifically described in the implementation process of the corresponding steps in the above-mentioned method, and will not be repeated here.

[0042] For the device embodiment, since it basically corresponds to the method embodiment, the relevant parts can refer to the partial description of the method embodiment. The device embodiment described above is only schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of the present invention. Ordinary technicians in this field can understand and implement it without paying creative work.

[0043] An embodiment of the present invention further provides a computer-readable storage medium having a program stored thereon. When the program is executed by a processor, a structural design method for suppressing cavitation erosion of a lubricating oil film of an engine connecting rod bearing in the above embodiment is implemented.

[0044] The computer-readable storage medium may be an internal storage unit of any device with data processing capability described in any of the aforementioned embodiments, such as a hard disk or a memory. The computer-readable storage medium may also be an external storage device of any device with data processing capability, such as a plug-in hard disk, a smart media card (SMC), an SD card, a flash card, etc. equipped on the device. Furthermore, the computer-readable storage medium may also include both an internal storage unit and an external storage device of any device with data processing capability. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capability, and may also be used to temporarily store data that has been output or is to be output.

[0045] The present invention also provides a computer program product, including a computer program, and when the computer program is executed by a processor, the structural design method for inhibiting cavitation erosion of the lubricating oil film of the engine connecting rod bearing is implemented.

[0046] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing, characterized in that: include: Step 1: Select the connecting rod bearing of the diesel engine as the object, establish a geometric model of the lubricating oil film between the bearings, introduce the established geometric model into the pre-constructed external flow field, and obtain the corresponding flow field physical model; Step 2: Use numerical simulation method to simulate the flow field physical model to obtain gas phase volume fraction and oil film pressure distribution data; Step 3, changing the slotting method of the bearing shell of the selected diesel engine, including selecting different slotting forms, slotting depths and quantities, and repeating steps 1 and 2; Step 4: Analyze the simulation results of the cavitation erosion of the lubricating oil film of the engine connecting rod bearing according to the gas phase volume fraction and oil film pressure distribution data obtained by different bearing slotting methods, and obtain the variation law of the cavitation degree under different bearing slotting methods; Step 5: According to the analysis results of step 4, select the bushing grooving method for the selected diesel engine connecting rod bearing.

2. The structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing according to claim 1, characterized in that: In step 1, the geometric model includes a bearing shell, a journal, and an oil inlet at a connecting rod bearing.

3. The structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing according to claim 1, characterized in that: In step 1, the external flow field includes a pressure inlet of the journal oil inlet, pressure outlets on both side end surfaces of the bearing gap, and a rotating surface for restoring the relative rotational motion between the journal and the bearing shell.

4. The structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing according to claim 1, characterized in that: In step 2, the numerical simulation method includes using the Singhal cavitation model and the moving mesh technology.

5. The structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing according to claim 1, characterized in that: In step 2, the gas phase volume fraction and oil film pressure distribution data include the oil film gas phase volume fraction peak value, oil film pressure peak value change data with time, and the oil film gas phase volume fraction and oil film pressure distribution data along the circumferential position.

6. The structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing according to claim 1, characterized in that: In step 3, the bearing grooving method includes three different grooving modes: single groove, double groove, and triple groove, four different oil groove depths, and three groove shapes: no groove, half groove, and full groove.

7. The structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing according to claim 1, characterized in that: In step 4, the variation of the cavitation degree under different bearing grooving methods refers to the influence of the number of grooves, oil groove depth, and groove shape on the oil film gas phase volume fraction and oil film pressure distribution.

8. The structural design method for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing according to claim 1, characterized in that: In step 5, a method for grooving the bearing shell of the diesel engine connecting rod bearing is selected according to the results of steps 3 and 4.

9. A structural design device for inhibiting cavitation erosion of lubricating oil film of engine connecting rod bearing, comprising a memory and one or more processors, wherein executable code is stored in the memory, characterized in that: When the processor executes the executable code, a structural design method for suppressing cavitation erosion of lubricating oil film of an engine connecting rod bearing according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, a structural design method for inhibiting cavitation erosion of lubricating oil film of an engine connecting rod bearing according to any one of claims 1 to 8 is implemented.

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