A piston profile design method, a piston, and an internal combustion engine system

Abstract

The present invention discloses a piston profile design method, which includes the following steps: establishing a finite element model of the piston and the cylinder liner, performing thermal deformation analysis to obtain thermal deformation data; based on the thermal deformation data, establishing a dynamic model of the piston and the cylinder liner, performing dynamic analysis to determine the initial piston profile where the cylinder liner does not undergo cavitation and the distribution range of the easy-to-scuff region; searching for the thermal deformation data corresponding to the easy-to-scuff region to obtain a thermal deformation curve; replacing the profile corresponding to the middle of the initial piston profile and the easy-to-scuff region with the inwardly concave thermal deformation curve to form the final piston profile; based on the final piston profile, establishing an actual structure model of the piston and the cylinder liner, performing tests to determine whether scuffing and cavitation will occur. If so, optimize the final profile and repeat this step. The present invention also provides a piston and an internal combustion engine system. The present invention can simultaneously take into account reducing the risks of piston scuffing and cylinder liner cavitation.

Description

Technical Field

[0001] The invention relates to the technical field of pistons, and in particular to a piston profile design method, a piston and an internal combustion engine system. Background Art

[0002] For internal combustion engine systems, cylinder pulling and cavitation are two main problems in piston design. The main reason for cylinder pulling is that under thermal load, the deformation between the piston and the cylinder liner is not coordinated, and there is a local protrusion, which can easily cause cylinder pulling on the matching surface of the piston and the cylinder liner. The main measure to solve the cylinder pulling problem is to increase the ovality of the skirt profile. Although this measure can reduce the contact area between the piston and the cylinder liner, it will increase the local knocking force between the piston and the cylinder liner and increase the risk of cylinder liner cavitation. In other words, it is impossible to take into account the problems of piston cylinder pulling and cavitation at the same time. Summary of the invention

[0003] The object of the present invention is to provide a piston profile design method, a piston and an internal combustion engine system, while taking into account the reduction of the problems of piston cylinder scuffing and cavitation.

[0004] In order to solve the above technical problems, the present invention provides a piston profile design method, comprising the following steps:

[0005] Step S1: establishing a finite element model of the piston and the cylinder liner, and performing a thermal deformation analysis to obtain thermal deformation data of the piston skirt surface and the cylinder liner inner surface;

[0006] Step S2: Based on the thermal deformation data, a dynamic model of the piston and the cylinder liner is established, and a dynamic analysis is performed to determine the initial piston profile where no cavitation occurs to the cylinder liner, and the distribution range of the cylinder liner area that is prone to pulling;

[0007] Step S3: searching for the thermal deformation data corresponding to the easy-to-pull cylinder area to obtain a thermal deformation curve of the easy-to-pull cylinder area;

[0008] Step S4: replacing the profile corresponding to the easy-to-pull cylinder area in the initial profile of the piston with the thermal deformation curve to form a final profile of the piston, wherein the profile corresponding to the easy-to-pull cylinder area in the final profile of the piston is concave inwards;

[0009] Step S5: Based on the final piston profile, an actual structural model of the piston and cylinder liner is established, and a cylinder scuffing and cavitation test is performed to determine whether the piston and cylinder liner will have cylinder scuffing and cavitation problems. If so, the final profile is optimized and step S5 is repeated.

[0010] The piston profile design method of the present invention first obtains the thermal deformation data of the piston skirt surface and the cylinder liner inner surface to provide boundary conditions for the next step of dynamic analysis, and also provides data reference for the subsequent combined profile design; secondly, a dynamic analysis is performed to determine the initial piston profile in which the cylinder liner does not suffer from cavitation, that is, the initial piston profile has solved the cylinder liner cavitation problem, and on this basis, the distribution range of the cylinder pull-prone area is determined. Since the cylinder pull problem is mainly caused by the uncoordinated thermal deformation between the piston and the cylinder liner, the profile in the initial piston profile corresponding to the cylinder pull-prone area is replaced by a thermal deformation curve, and The thermal deformation curve is concave relative to the initial piston profile, which is equivalent to "removing" the material in the cylinder-pull-prone area in advance, ensuring that the risk of cylinder pull due to thermal deformation is reduced as much as possible under the premise of no cavitation. At this point, the obtained final piston profile has theoretically solved both the cavitation and cylinder pull problems. Finally, based on the final piston profile, an actual structural model of the piston and cylinder liner is established, and a cylinder pull and cavitation test is carried out. Only when the measured results confirm that cylinder pull and cavitation problems will not occur again, the final piston profile design is completed. Otherwise, the final piston profile is continuously adjusted until the requirements are met.

[0011] It can be seen that the piston profile design method of the present invention no longer uses a standard elliptical profile, but instead uses a spliced ​​piston profile structure, while taking into account the reduction of the problems of piston cylinder pulling and cavitation, and increasing the service life of the piston and cylinder liner.

[0012] Optionally, determining an initial piston profile where cavitation does not occur on the cylinder liner specifically comprises the following steps:

[0013] Step S211: Check the dynamic simulation results to obtain the vibration data of the cylinder liner;

[0014] Step S222: Based on the vibration data, the cavitation pressure of the coolant is calculated by an empirical formula to determine whether the cavitation pressure is greater than the current saturated vapor pressure of the coolant. If so, no cavitation occurs in the cylinder liner.

[0015] Optionally, determining the distribution range of the easy-pull cylinder area specifically includes the following steps:

[0016] Step S221: Check the dynamic simulation results to obtain the rough contact pressure of each contact area between the piston and the cylinder liner;

[0017] Step S222: Determine whether each rough contact pressure is greater than a preset standard value, and if so, the contact area is the easy-to-pull cylinder area.

[0018] Optionally, the initial piston profile is an elliptical function profile.

[0019] Optionally, the thermal deformation curve is an nth-order polynomial function curve, where n≥2.

[0020] Optionally, thermal deformation analysis is performed by finite element analysis software Abaqus;

[0021] And / or, dynamic analysis is performed by software AVL excite PU.

[0022] The present invention provides a piston obtained based on the foregoing piston profile design method. The piston profile includes a base circle, and a concave area is formed at a preset position of the base circle.

[0023] The piston of the present invention is obtained based on the foregoing piston profile design method, and thus has the same technical effects as the foregoing piston profile design method, which will not be elaborated herein.

[0024] Optionally, the base circle is elliptical.

[0025] Optionally, the profile of the concave area is an nth-order polynomial function curve, where n≥2.

[0026] The present invention provides an internal combustion engine system, including a cylinder liner and the foregoing piston, and the piston is movably installed inside the cylinder liner.

[0027] The internal combustion engine system of the present invention includes the foregoing piston, and thus has the same technical effects as the foregoing piston, which will not be elaborated herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flowchart of a specific embodiment of the piston profile design method provided by the present invention;

[0029] Figure 2 is Figure 1 a schematic diagram of the formation of the thermal deformation curve in the piston profile design method;

[0030] Figure 3 is Figure 1 a schematic diagram of the final piston profile in the piston profile design method;

[0031] Figure 4 is Figure 1 a flowchart of determining the initial piston profile that prevents the cylinder liner from cavitation in the piston profile design method;

[0032] Figure 5 is Figure 1 a flowchart of determining the distribution range of the easy-to-scuff region in the piston profile design method;

[0033] Wherein, Figures 2 - 3 the reference numerals in

[0034] are described as follows: DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] The terms "first", "second", etc. described herein are only for facilitating the description of two or more structures or components having the same or similar structures and / or functions, and do not represent a certain special limitation on the order and / or importance.

[0037] The term "a plurality" described herein refers to an indefinite number of more than one, usually more than two; and when the number of several components is represented by "a plurality", it does not represent the mutual relationship in terms of quantity among these components.

[0038] Please refer to Figures 1 - 3 , Figure 1 , which is a flowchart of a specific embodiment of the piston profile design method provided by the present invention; Figure 2 is Figure 1 a schematic diagram of the formation of the thermal deformation curve in the piston profile design method;

[0039] Figure 3 is Figure 1 a schematic diagram of the final piston profile in the piston profile design method.

[0040] The present invention provides a piston profile design method, including the following steps:

[0041] Step S1: Establish a finite element model of the piston and the cylinder liner, and perform thermal deformation analysis to obtain the thermal deformation data of the piston skirt surface and the inner surface of the cylinder liner;

[0042] Step S2: Based on the thermal deformation data, establish a dynamic model of the piston and the cylinder liner, and perform dynamic analysis to determine the initial piston profile where the cylinder liner does not cavitate, and determine the distribution range of the easy-to-scuff region;

[0043] Step S3: Search for the thermal deformation data corresponding to the easy-to-scuff region to obtain the thermal deformation curve L of the easy-to-scuff region;

[0044] Step S4: Replace the profile corresponding to the easy-to-scuff region in the initial piston profile with the thermal deformation curve L to form the final piston profile A. In the final piston profile A, the profile corresponding to the easy-to-scuff region is recessed inward;

[0045] Step S5: Based on the final piston profile A, establish an actual structure model of the piston and the cylinder liner, and perform a scuffing and cavitation test to determine whether the piston and the cylinder liner will have scuffing and cavitation problems. If so, optimize the final profile and repeat Step S5.

[0046] The piston profile design method of the present invention first obtains the thermal deformation data of the piston skirt surface and the cylinder liner inner surface to provide boundary conditions for the next step of dynamic analysis, and also provides data reference for the subsequent combined profile design; secondly, a dynamic analysis is performed to determine the piston initial profile where the cylinder liner does not suffer from cavitation, that is, the piston initial profile has solved the cylinder liner cavitation problem, and on this basis, the distribution range of the cylinder pull-prone area is determined. Since the cylinder pull problem is mainly caused by the uncoordinated thermal deformation between the piston and the cylinder liner, the profile in the piston initial profile corresponding to the cylinder pull-prone area is replaced by the thermal deformation curve L, and the The thermal deformation curve L is concave relative to the initial piston profile, which is equivalent to "removing" the material in the cylinder-pull-prone area in advance, ensuring that the risk of cylinder pull due to thermal deformation of the piston is reduced as much as possible under the premise of no cavitation. At this time, the obtained piston final profile A has theoretically solved both the cavitation and cylinder pull problems. Finally, based on the piston final profile A, an actual structural model of the piston and cylinder liner is established, and a cylinder pull and cavitation test is carried out. Only when the measured results confirm that cylinder pull and cavitation problems will not occur again, the design of the piston final profile A is completed. Otherwise, the piston final profile A is continuously adjusted until the requirements are met.

[0047] in:

[0048] In step S1, thermal deformation analysis of the piston and cylinder liner is performed, which can be performed using finite element analysis software Abaqus. The specific steps are prior arts well known to those skilled in the art and will not be described in detail here. The thermal deformation data of the piston skirt surface and the inner surface of the cylinder liner mainly refer to radial thermal deformation data.

[0049] In step S2, a dynamic model of the piston and cylinder liner is established, and a dynamic analysis is performed, which can be performed by using software AVLexcite PU. The specific steps are prior arts well known to those skilled in the art, and thus will not be described in detail here.

[0050] In step S2, determining the initial piston profile without cavitation of the cylinder liner specifically includes the following steps:

[0051] Step S211: Check the dynamic simulation results to obtain the vibration data of the cylinder liner;

[0052] Step S212: Based on the vibration data, the cavitation pressure of the coolant is calculated by an empirical formula to determine whether the cavitation pressure is greater than the current saturated vapor pressure of the coolant. If not, the piston and cylinder liner dynamic models are optimized and the dynamic analysis is performed again; if so, the current piston profile is the initial piston profile when no cavitation occurs in the cylinder liner.

[0053] In step S2, the distribution range of the easy-pull cylinder area is determined, which specifically includes the following steps:

[0054] Step S221: Check the results of the dynamic simulation to obtain the rough contact pressure at each contact area between the piston and the cylinder liner.

[0055] Step S222: Determine whether each of the rough contact pressures is greater than a preset standard value. If so, this contact area is the cylinder scuffing area.

[0056] Among them, since the evaluation criteria are different, the specific value of this preset standard value will also change accordingly. In practical applications, it can be adjusted according to requirements.

[0057] In step S2, the determined initial piston profile is an elliptic function profile.

[0058] In step S3, the determined thermal deformation curve L is an nth-order polynomial function curve, where n≥2. By adjusting each exponent, the specific shape of the function curve can be flexibly controlled. The value standard of n is: to ensure a smooth transition at the connection between the thermal deformation curve L and the initial piston profile.

[0059] It can be seen from this that in the piston profile design method of the present invention, the piston profile no longer adopts a standard elliptical profile. Instead, through the thermal deformation analysis and dynamic analysis of the piston and the cylinder liner, a design boundary is provided for the profile design. The piston profile is designed using a profile structure spliced by an elliptic function and an nth-order polynomial function. Utilizing the characteristics of the nth-order polynomial function profile with smooth transition and flexible adjustment, the profile shape of the cylinder scuffing area is flexibly controlled. While ensuring the ellipticity requirement, the relative deformation amount between the piston skirt after thermal expansion and the cylinder liner has no local protrusion. Furthermore, the piston profile takes into account both reducing the risk of cavitation erosion and the problem of cylinder scuffing, improving the service life of the piston and the cylinder liner.

[0060] The present invention also provides a piston obtained based on the aforementioned piston profile design method. The piston profile includes a base circle a, and a concave area b is formed at a preset position of the base circle a.

[0061] The piston of the present invention is obtained based on the aforementioned piston profile design method. Therefore, it can take into account both reducing piston cylinder scuffing and cavitation erosion problems, and improve the service life of the piston and the cylinder liner.

[0062] Among them, based on the aforementioned piston profile design method, this preset position is the area where the piston is prone to cylinder scuffing problems.

[0063] Among them, this base circle a is elliptical, and the ellipticity is obtained through dynamic analysis to ensure that no cavitation erosion problem occurs in the cylinder liner.

[0064] Among them, the profile of the concave area b is an nth-order polynomial function curve, where n≥2. By adjusting each exponent, the specific shape of the function curve can be flexibly controlled. The value standard of n is: to ensure a smooth transition at the connection between the thermal deformation curve L and the initial piston profile.

[0065] The present invention also provides an internal combustion engine system, including a cylinder liner and the aforementioned piston, and the piston is movably installed inside the cylinder liner.

[0066] The internal combustion engine system of the present invention includes the aforementioned piston, and thus has the same technical effects as the aforementioned piston, which will not be elaborated herein.

[0067] The above has introduced in detail a piston profile design method, a piston and an internal combustion engine system provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A piston profile design method, characterized in that, It includes the following steps: Step S1: Establish a finite element model of the piston and the cylinder liner, and conduct a thermal deformation analysis to obtain the thermal deformation data of the piston skirt surface and the inner surface of the cylinder liner; Step S2: Based on the thermal deformation data, establish a dynamic model of the piston and the cylinder liner, and conduct a dynamic analysis to determine the initial piston profile where the cylinder liner does not suffer from cavitation, and determine the distribution range of the easy-to-scuff region; Step S3: Search for the thermal deformation data corresponding to the easy-to-scuff region to obtain the thermal deformation curve (L) of the easy-to-scuff region; Step S4: Replace the profile corresponding to the easy-to-scuff region in the initial piston profile with the thermal deformation curve (L) to form the final piston profile (A). In the final piston profile (A), the profile corresponding to the easy-to-scuff region is recessed inward; Step S5: Based on the final piston profile (A), establish an actual structure model of the piston and the cylinder liner, and conduct a scuffing and cavitation test to determine whether the piston and the cylinder liner will have scuffing and cavitation problems. If so, optimize the final profile and repeat Step S5.

2. The piston profile design method according to claim 1, wherein To determine the initial piston profile where the cylinder liner does not suffer from cavitation, it specifically includes the following steps: Step S211: Check the dynamic simulation results to obtain the vibration data of the cylinder liner; Step S212: Based on the vibration data, calculate the cavitation pressure of the coolant through an empirical formula, and determine whether the cavitation pressure is greater than the saturation vapor pressure of the current coolant. If not, optimize the dynamic model of the piston and the cylinder liner and conduct a dynamic analysis again; if so, the current piston profile is the initial piston profile where the cylinder liner does not suffer from cavitation.

3. The piston profile design method according to claim 1, characterized in that, To determine the distribution range of the easy-to-scuff region, it specifically includes the following steps: Step S221: Check the dynamic simulation results to obtain the rough contact pressure of each contact region between the piston and the cylinder liner; Step S222: Determine whether each rough contact pressure is greater than a preset standard value. If so, this contact region is the easy-to-scuff region.

4. The piston profile design method according to claim 1, characterized in that, The initial piston profile is an elliptic function profile.

5. The piston profile design method according to claim 1, characterized in that The thermal deformation curve (L) is an nth-order polynomial function curve, where n≥2.

6. The piston profile design method according to claim 1, wherein The thermal deformation analysis is carried out by using the finite element analysis software Abaqus; and / or, the dynamic analysis is carried out by using the software AVL excite PU.

7. A piston obtained based on the piston profile design method according to any one of claims 1-6, characterized in that, The piston profile includes a base circle (a), and an inner concave region (b) is formed at a preset position of the base circle (a).

8. The piston according to claim 7, wherein, The base circle (a) is elliptical.

9. The piston according to claim 7, characterized in that, The profile of the inner concave region (b) is an nth-order polynomial function curve, where n≥2.

10. An internal combustion engine system, characterized in that, It includes a cylinder liner and the piston according to any one of claims 7-9, and the piston is movably installed inside the cylinder liner.

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