Aero-piston engine crankcase and its lightweight optimization method

Abstract

The present application relates to a kind of aero piston engine crankcases and its lightweight optimization method.The method includes: obtaining the core design target of crankcase, displacement boundary condition and load boundary condition;Establish the initial thin shell model of crankcase, and the initial thin shell model is checked and regionally divided by thin shell theory;The main force topology structure of crankcase is constructed, and the initial thickness and structure size estimation of the key area of crankcase is carried out;The key area of crankcase is carried out in sub-region topological optimization, and the shell structure, reinforcing rib layout and thickness distribution of the optimized crankcase are obtained;The finite element model of the optimized crankcase is established, and the finite element model is checked;The finished product weight of the crankcase that passes the check is accounted, and the final crankcase model is obtained.The present application can guarantee strength and rigidity, substantially reduce the weight of crankcase, and improve the power-to-weight ratio of aero piston engine.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, and in particular to an aero-piston engine crankcase and its lightweight optimization method. Background Technology

[0002] In the fields of general aviation and unmanned aerial vehicles (UAVs), lightweight engine design is a crucial way to improve aircraft performance, directly impacting payload capacity and fuel efficiency. Aero piston engines have stringent requirements for power density and power-to-weight ratio, making the lightweight design of the crankcase, as a core load-bearing structure, paramount. Traditional aero piston engine crankcases, limited by design methods, typically employ high-strength metal materials to increase wall thickness for enhanced strength and rigidity, relying on empirical formulas and stacked reinforcing ribs. This results in significant redundant weight, uneven stress distribution, and insufficient stiffness. While this design approach can meet strength requirements, it struggles to achieve lightweighting. Therefore, achieving lightweighting while maintaining crankcase strength and rigidity has become a pressing issue.

[0003] In traditional technologies, cast aluminum 105A possesses excellent specific strength, castability, and corrosion resistance, making it an ideal material for lightweight applications. However, its potential in crankcases has not been fully explored. Traditional technologies suffer from several problems, such as topology optimization potentially leading to localized stress concentration, optimized design potentially affecting manufacturing process feasibility, high redundancy in empirical designs, oversimplification of mechanical models, significant weakening effect of openings, and insufficient stiffness matching.

[0004] To further reduce crankcase weight, Chinese patent CN104879235A, "Aluminum Crankcase Cylinder Bore Assembly Structure and Processing Method Thereof," proposes an aluminum crankcase cylinder bore assembly structure and processing method that can effectively reduce the deformation of the aluminum crankcase cylinder bore. This invention employs an aluminum crankcase cylinder bore assembly structure, which ensures the fit between the steel support sleeve and the cylinder liner while reducing the deformation of the aluminum crankcase cylinder bore. However, this method does not optimize the structural weight of the crankcase itself; therefore, there is still considerable room for improvement in optimizing the overall weight of the crankcase.

[0005] Furthermore, Chinese patent CN107992638A, entitled "A Method and Apparatus for Establishing an Engine Crankcase Structural Model," proposes a method and apparatus for establishing an engine crankcase structural model. Combining vibration theory and optimization theory, it utilizes virtual simulation calculations before prototype manufacturing to guide crankcase design. This method involves multiple simulation calculations for optimization before trial production, which can shorten the development cycle, but requires numerous calculations and corrections, demanding experienced designers and strong computational capabilities.

[0006] In summary, traditional lightweight design and manufacturing methods for aircraft piston engine crankcases do not take into account the requirements of aircraft for aircraft piston engines, making it difficult to guarantee optimal performance and power-to-weight ratio. Therefore, there is still much room for improvement in the lightweight design of crankcases. Summary of the Invention

[0007] This invention provides a crankcase for an aero-piston engine and a method for its lightweight optimization. While ensuring strength and rigidity, it can significantly reduce the weight of the crankcase of an aero-piston engine, thereby solving the problems of large crankcase weight and insufficient structural optimization in traditional designs and improving the power-to-weight ratio of the aero-piston engine.

[0008] To achieve the above objectives, the present invention provides a method for optimizing the lightweight design of a crankcase in an aero-piston engine, comprising: S1. Obtain the core design objectives, displacement boundary conditions, and load boundary conditions of the crankcase of an aero-piston engine; wherein, the core design objectives include weight objectives, strength objectives, stiffness objectives, high-cycle fatigue strength objectives, manufacturability objectives, and functional integration objectives; S2. Establish an initial thin-shell model of the crankcase, and verify and divide the initial thin-shell model into regions using thin-shell theory. That is, based on the initial envelope size of the initial thin-shell model of the crankcase, verify the ratio of shell thickness to radius of curvature, and divide the crankcase into thin-shell regions that meet the application conditions of thin-shell theory, and thick-shell regions or combined shell regions that do not meet the application conditions of thin-shell theory. S3. Analyze the load transfer path of the crankcase, construct the main load-bearing topology of the crankcase based on the in-plane bearing characteristics of the thin shell, and estimate the initial thickness and structural dimensions of the key areas of the crankcase in combination with thin shell theory. S4. With minimizing structural mass as the optimization objective and strength, stiffness, natural frequency, manufacturing process, and thin-shell stability as constraints, perform regional topology optimization on the key areas of the crankcase to obtain the optimized crankcase shell structure, stiffener layout, and thickness distribution. S5. Establish a finite element model for the optimized crankcase, and verify the static strength, stiffness, high-cycle fatigue strength and thin-shell buckling stability of the finite element model under multiple working conditions. S6. Calculate the finished weight of the crankcase that has passed the verification. If the weight does not meet the target requirements, iteratively optimize the structural parameters within the performance constraint boundary, and at the same time complete the casting process adaptability adjustment to obtain the final crankcase model.

[0009] Furthermore, the present invention also proposes an aircraft piston engine crankcase, characterized in that the aircraft piston engine crankcase is designed and manufactured using the lightweight optimization method for aircraft piston engine crankcases described above.

[0010] The beneficial effects of the technical solution provided by this invention include: 1. The structure of the crankcase of an aero-piston engine was optimized using thin-shell theory to achieve weight reduction requirements. In the finite element analysis, various load conditions during the operation of the aero-piston engine were simulated, including gas pressure, inertial force, and thermal stress. The crankcase was designed as a structure composed of curved thin-shell units. Through optimization, the weight of the crankcase was reduced by approximately 25%.

[0011] 2. Despite the weight reduction, thin-shell theory ensures the structural strength of the crankcase by optimizing the structural shape and stress distribution. Stress concentration and fatigue life were considered in the design, enabling the crankcase to withstand high-load operating conditions while maintaining a lighter weight, thus extending its service life. Strength and stiffness calculations were performed using thin-shell theory, and the design was verified through finite element analysis, ensuring its reliability.

[0012] 3. The thin-shell design helps absorb and disperse vibrations generated during engine operation, reducing noise. Through meticulous optimization of the crankcase shape and materials, the overall vibration and noise levels of the engine can be effectively reduced, improving flight comfort and environmental friendliness.

[0013] 4. Due to the reduced material usage, the crankcase designed based on thin-shell theory has a significant decrease in raw material costs. At the same time, the optimized structural design simplifies manufacturing and assembly processes, reduces production time and labor costs, and lowers overall manufacturing expenses.

[0014] 5. The thin-shell structure design facilitates more efficient heat dissipation. By optimizing the heat dissipation area of ​​the crankcase surface and the airflow path, heat can be dissipated more quickly, keeping the engine operating within its optimal temperature range and improving performance and reliability.

[0015] 6. Due to the reduced overall weight, the engine requires less thrust, directly improving fuel efficiency. Higher fuel efficiency not only reduces operating costs but also decreases carbon emissions, contributing to environmental protection and sustainable development.

[0016] 7. By optimizing stress distribution through thin-shell theory, stress concentration and fatigue crack formation are reduced. The crankcase exhibits better fatigue resistance during long-term use, extending maintenance cycles and service life, and reducing maintenance and replacement costs.

[0017] 8. The thin-shell structure design offers better environmental adaptability, enabling stable operation under harsh conditions such as high temperature, high pressure, and vibration. This enhanced environmental adaptability allows the engine to maintain excellent performance under different flight conditions, improving reliability and safety. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a simplified schematic diagram illustrating the steps of the lightweight optimization method for the crankcase of an aero-piston engine according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the overall structure of the crankcase of the aero-piston engine according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the upper housing of the crankcase of the aero-piston engine according to an embodiment of the present invention; Figure 4 This is a side view of the upper housing of the crankcase of the aero-piston engine according to an embodiment of the present invention; Figure 5 This is a cross-sectional view of the lubrication oil passage of the main bearing of the crankcase of the aero-piston engine according to an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Traditional lightweight design and manufacturing methods for aircraft piston engine crankcases do not take into account the requirements of aircraft for aircraft piston engines, making it difficult to guarantee optimal performance and power-to-weight ratio. Therefore, there is still considerable room for improvement in the lightweight design of crankcases. To address the above technical problems, this invention proposes a lightweight optimization method for aircraft piston engine crankcases, as well as an aircraft piston engine crankcase design.

[0022] like Figure 1 As shown, this invention provides a method for lightweighting and optimizing the crankcase of an aero-piston engine, comprising: S1. Obtain the core design objectives, displacement boundary conditions, and load boundary conditions of the crankcase of an aero-piston engine; wherein, the core design objectives include weight objectives, strength objectives, stiffness objectives, high-cycle fatigue strength objectives, manufacturability objectives, and functional integration objectives; S2. Establish an initial thin-shell model of the crankcase, and verify and divide the initial thin-shell model into regions using thin-shell theory. That is, based on the initial envelope size of the initial thin-shell model of the crankcase, verify the ratio of shell thickness to radius of curvature, and divide the crankcase into thin-shell regions that meet the application conditions of thin-shell theory, and thick-shell regions or combined shell regions that do not meet the application conditions of thin-shell theory. S3. Analyze the load transfer path of the crankcase, construct the main load-bearing topology of the crankcase based on the in-plane bearing characteristics of the thin shell, and estimate the initial thickness and structural dimensions of the key areas of the crankcase in combination with thin shell theory. S4. With minimizing structural mass as the optimization objective and strength, stiffness, natural frequency, manufacturing process, and thin-shell stability as constraints, perform regional topology optimization on the key areas of the crankcase to obtain the optimized crankcase shell structure, stiffener layout, and thickness distribution. S5. Establish a finite element model for the optimized crankcase, and verify the static strength, stiffness, high-cycle fatigue strength and thin-shell buckling stability of the finite element model under multiple working conditions. S6. Calculate the finished weight of the crankcase that has passed the verification. If the weight does not meet the target requirements, iteratively optimize the structural parameters within the performance constraint boundary, and at the same time complete the casting process adaptability adjustment to obtain the final crankcase model.

[0023] The crankcase structure was redesigned using thin-shell theory to meet weight reduction requirements. Thin-shell theory simplifies structures to two-dimensional surfaces with thickness. Through rational surface design, it's possible to maintain or improve structural strength and rigidity while reducing material usage. The curved shape of an eggshell effectively disperses external pressure. Although thin, its unique shape gives it excellent structural strength. Under external forces, it resists deformation through bending and torsion. Circular and elliptical structures can distribute forces evenly, reducing localized stress concentration.

[0024] This invention proposes a lightweight optimization method for aero-engine crankcases based on thin-shell theory, which can design an optimized crankcase for aero-engine heavy oil piston engines. Specifically, it can significantly reduce the weight of the aero-engine crankcase while ensuring strength and rigidity, thus solving the problems of heavy crankcases and insufficient structural optimization in traditional designs, and improving the power-to-weight ratio of aero-engines. This method is specifically designed for aero-engine twin-cylinder diesel engines, aiming for extreme lightweighting (total weight ≤ 3.8 kg), high rigidity, and high fatigue strength of the crankcase. In this embodiment, the crankcase material can be cast aluminum 105A, and the following description will use crankcases made of cast aluminum 105A.

[0025] Specifically, in step S1, among the core design objectives of the crankcase of the aero-piston engine, the weight objective can be that the final product weight does not exceed 3.8 kg; the strength objective can be that, under the maximum burst pressure, the maximum paradigm equivalent stress does not exceed the yield strength of cast aluminum 105A. 60% (75MPa), with a safety factor of 1.67; the high-cycle fatigue strength target is The cycle is repeated, with a safety factor of not less than 1.5.

[0026] In addition, the stiffness targets are as follows: the main bearing housing of the crankcase, under the combined action of maximum burst pressure and maximum inertial force, has a maximum deformation of less than 3 μm along the crankshaft axis; the cylinder liner mounting surface of the crankcase, under bolt preload and gas pressure, has a flatness deformation of less than 3 μm; and the entire crankcase, under 1.5 times the maximum burst pressure, has a torsional stiffness of ≥5000 Nm / deg.

[0027] Furthermore, the process objectives are that the crankcase be adaptable to sand casting, with uniform wall thickness (min≥3mm), avoidance of hot spots, reasonable draft angle, and reduction of complex internal cavities. In addition, the functional integration objectives are that the crankcase can efficiently integrate lubrication channels, sensor mounting bases, and accessory mounting surfaces.

[0028] Furthermore, in step S1, the displacement boundary conditions may include the Z-direction constraint of the crankcase oil pan mounting surface, the X and Y-direction rotational constraints and the Z-direction sliding constraint of the crankcase flywheel housing mounting surface to simulate thermal expansion, and the X, Y, and Z-direction constraints of the crankcase front cover mounting surface.

[0029] Furthermore, load boundary conditions may include the maximum burst pressure inside the cylinder, the reciprocating and rotational inertial forces of the piston assembly and connecting rod, the preload of the cylinder head bolts and main bearing cap bolts, accessory loads, and thermal loads caused by the temperature gradient in the cylinder region.

[0030] Specifically, maximum burst pressure , which is the gas force acting on the inner wall of the cylinder liner; the reciprocating and rotational inertial force of the piston assembly and connecting rod, which is the maximum value of the reciprocating and rotational inertial force of the piston assembly and connecting rod, equivalent to the inertial force applied to the center of the main bearing housing; the preload of the cylinder head bolts and main bearing cap bolts, which is the bolt preload of the cylinder head bolts, main bearing cap bolts, and oil pan bolts according to the target preload (such as 0.7 times the bolt yield strength); the accessory load is the force and torque of accessories such as the fuel pump; the thermal load caused by the temperature gradient in the cylinder area is the thermal stress caused by the temperature gradient in the cylinder area, with the maximum operating temperature set at 150°C.

[0031] Furthermore, in step S2, establishing the initial thin-shell model of the crankcase may include creating a basic envelope containing the crankcase. In this embodiment, the crankcase has dimensions of approximately 250 mm in length, approximately 200 mm in width, and approximately 150 mm in height, with a preliminary wall thickness (shell thickness) of 5 mm.

[0032] Furthermore, the crankcase can be configured as an initial thin-shell model composed of curved thin shells, dividing it into upper and lower housings (i.e., upper housing and lower housing). During machining, the upper and lower housings are decomposed into several thin-shell units, each with a radius of curvature much larger than its shell thickness. The criterion for verifying the initial thin-shell model using thin-shell theory is that the shell thickness t of the initial thin-shell model of the crankcase is related to the local minimum radius of curvature. The ratio t / ≤0.1; where the cylinder region of the initial thin-shell model is treated as a thick-shell region or a combined shell region, and the remaining regions with a curvature radius R>80mm are treated as thin-shell regions.

[0033] Specifically, for the initial thin-shell model of the crankcase, the ratio of shell thickness to radius of curvature (t / R) is the local minimum radius of curvature of the initial thin-shell model. Must meet t / ≤0.1 (≤0.05 is generally preferred). Preliminary estimation of the crankcase bore area. If the initial wall thickness is set to t = 4 mm, then (Near the boundary). Therefore, the cylinder area of ​​the crankcase needs to be treated as a thick-shell area or a combined shell area, while most other areas (R>80mm) can be treated as thin-shell areas using the thin-shell theory (t / R≤0.05).

[0034] Furthermore, as can be seen from the above steps, the main types of loads borne by the crankcase are in-plane membrane forces (gas forces, inertial force transmission) and bending moments (bolt preload, accessory couples). Moreover, thin-shell theory can accurately calculate displacement and stress within a small deformation range, thus limiting deformation.

[0035] Furthermore, in step S3, the load transfer path specifically involves the gas force within the engine cylinder being transferred from the cylinder liner to the cylinder liner mounting flange, then through the top housing, cylinder block, main bearing diaphragm, main bearing housing, and side housing to the base flange or oil pan flange, and finally to the engine mounting bracket via the crankcase base bolts. Moreover, the gas force under maximum burst pressure can be as follows: (per cylinder)

[0036] Furthermore, the main load-bearing topology may include the top shell of the crankcase, the inter-cylinder load-bearing partition, the main bearing partition, the side shell, the base flange, or the oil pan flange; wherein, the top shell is a continuous curved surface shell with an arch height, and the arch height is 1 / 10 to 1 / 8 of the cylinder center distance.

[0037] Specifically, the main load-bearing topology is constructed as follows: The top shell of the crankcase can be constructed as a continuous curved shell (cylindrical or slightly saddle-shaped) with appropriate arch height, effectively utilizing membrane tension to bear gas force and avoiding large bending deformation of planar structures; its initial arch height H is estimated to be 1 / 10 to 1 / 8 of the cylinder center distance (cylinder center distance L≈1.5*Bore≈117mm, H≈12-15mm).

[0038] The inter-cylinder load-bearing partition (inter-cylinder wall) can be constructed as a critical longitudinal load-bearing partition, connecting the mounting holes of the two cylinder liners, transmitting gas force, and withstanding high pressure differentials; a variable thickness design can be adopted, with the top thickness (load-bearing capacity)... The bottom gradually thins (connecting to the main bearing housing), and can be treated as a plane stress plate or a shallow arch shell.

[0039] The main bearing diaphragm can be constructed as a core rigidity unit, connecting the cylinder wall and the side shell, and supporting the main bearing housing. Its shape can be a rotationally symmetric shell (quasi-cylindrical section), which can withstand complex in-plane forces and out-of-plane bending moments, and is key to stiffness control.

[0040] The side shell can be constructed to connect the top shell, main bearing partition and base flange. It mainly bears in-plane shear force (transmits lateral tilting moment) and out-of-plane bending (resists attachment moment). It can be designed as a cylindrical shell or a conical shell transition.

[0041] The base flange or oil pan flange can be constructed as a thick-edged annular plate to provide installation rigidity and sealing, connect to the side housing, and withstand bolt preload and internal pressure. It can be processed as a thick annular plate or combined housing area.

[0042] Furthermore, in step S3, the key areas include the cylinder liner mounting flange, cylinder wall, main bearing housing, top shell, side shell, base flange or oil pan flange. Combining the calculation formulas for the stiffness and stress of the annular plate, pressure plate and cylindrical shell of thin shell theory, the initial thickness estimation of each area is completed.

[0043] Specifically, the initial thickness estimates for each region are as follows: Among them, the cylinder liner mounting flange bears the preload of the cylinder head bolts. and gas force The resulting localized bending can be simplified as the annular plate being subjected to a uniformly distributed load (equivalent load of bolts) and a concentrated load at the center. Function. The maximum bending moment of the cylinder liner mounting flange is near the bolt holes, and the estimation formula is as follows: Equation (1); in, The section modulus of bending is related to the diameter of the bolt distribution circle. Related, and ; , These are empirical coefficients (related to constraints, preliminary). , ); The thickness of the cylinder liner mounting flange; make (Considering fatigue), substitute... (If a single cylinder has four M10 bolts, the preload of a single bolt is approximately:) ; ; It can be seen that, , , ; The thickness of the cylinder liner mounting flange can then be calculated using equation (1). : ; The initial thickness of the cylinder liner mounting flange can be taken as... (Further optimization and thinning).

[0044] In addition, the inter-cylinder wall mainly bears the membrane pressure (approximately equal to) This can be simplified as a tension plate with a center opening (cylinder bore). Therefore, the stress concentration factor of the opening needs to be considered. (Theoretical value ≥ 3, optimization required). The minimum net cross-sectional area of ​​the cylinder wall is as follows: Equation (2); where S is the cylinder center distance and D is the cylinder diameter; The thickness of the cylinder wall.

[0045] It can also be known that the average membrane stress of the inter-cylinder wall is as follows: Equation (3); Maximum stress required ; Substituting S=100mm and D=78mm, , Applying the optimized target value to equation (3), we can obtain: Equation (4); Further results can be obtained: Equation (5); The thickness of the inter-cylinder wall can be obtained. as follows: The initial thickness of the inter-cylinder wall can be taken as... (Considering bending contribution and optimization space).

[0046] In addition, the main bearing housing bears the reaction force of the main bearing. and bending moment The stiffness can be estimated based on the in-plane stiffness of a thick-walled cylinder (bearing bore) or a combination of a locally pressure plate and a thin shell. The key stiffness index of the main bearing housing is its ability to resist radial deformation, which can be simplified to the local annular stiffness.

[0047] It can be seen that the radial stiffness has the following relationship: Equation (6); in, ; The wall thickness of the main bearing housing; When the target deforms hour, Then the following relationship exists: Equation (7); in, This is the shape factor, approximately equal to 0.1; Substituting E=70GPa into equation (7), we get: The wall thickness of the main bearing housing can be calculated. : Then the initial wall thickness of the main bearing housing can be taken. (Subsequent topology optimization to reduce weight).

[0048] Furthermore, the top or side shells primarily transmit in-plane membrane forces and withstand minor bending; therefore, they can be estimated as shear shells. The specific estimation of shear force is as follows: Equation (8); set up typical , .

[0049] Then the thickness of the top shell or side shell as follows: Equation (9); Considering the local buckling stability of thin shells, the initial thickness of the top or side shells can be taken. (Minimum process thickness + stability margin)

[0050] In addition, the base flange bears the bolt preload. and oil pan internal pressure The resulting bending can be treated as a uniformly distributed bending moment on a ring plate. And the estimation of uniformly distributed pressure. The maximum bending moment is conservatively taken as follows: Equation (10); Where, the coefficient of C is approximately 0.25. For flange diameter ≈ 200mm, =12, ≈50kN; then we can obtain: .

[0051] It can be seen that the stress on the base flange is as follows: Equation (11); in, This refers to the thickness of the base flange.

[0052] Calculate based on the unit width of the plate, and let The thickness of the base flange can then be obtained from equation (11). The initial base flange thickness can be taken. It is 6mm.

[0053] Furthermore, in step S4, the optimization objective of the geometric topology optimization (lightweight core) based on thin-shell theory is to minimize structural compliance (maximize stiffness) or minimize mass while satisfying the strength, stiffness, and manufacturing constraints of steps S1, S2, and S3. The design variable is the material density distribution (0-1) of each region of the shell, which is equivalent to the thickness distribution.

[0054] Furthermore, the constraints for topology optimization may specifically include: Strength constraints: stress in each region ≤ 75 MPa; Stiffness constraints: relative displacement of the main bearing housing along the crankshaft axis ≤ 0.02 mm; flatness of the cylinder liner mounting surface ≤ 0.03 mm. Natural frequency constraint: first-order torsional frequency ≥ 1.5 times engine ignition frequency; Manufacturing constraints: minimum wall thickness ≥ 3.0 mm, maximum thickness ≤ 20 mm, draft direction and symmetry constraints (i.e., draft direction constraints, symmetry constraints (double cylinder)). Thin-shell stability constraint, local buckling factor ≥ 1.5.

[0055] Furthermore, in step S4, the regional topology optimization specifically includes: The main bearing diaphragm is optimized for lightweighting by maximizing the stiffness-to-mass ratio of the main bearing housing. This is achieved by creating a radially reinforcing rib structure and adding a thickened load-bearing ring around the bearing bore. Specifically, the radially reinforcing rib structure extends from the bearing bore towards the cylinder wall and sides, with a rib height of approximately 8mm, a rib width of approximately 5mm, and a base plate thickness reduced to approximately 4mm (from the original 16mm solid). A thickened load-bearing ring (approximately 10mm) is formed around the central bearing bore, resulting in a weight reduction potential of >50%.

[0056] The lightweight optimization of the cylinder wall aims to achieve stress uniformity by employing a variable thickness design. The high-stress area maintains its thickness, while a weight-reducing hole is created in the middle with flanged edges. The bottom transition area is thinned. Specifically, the top high-stress area of ​​the cylinder wall maintains a thickness of approximately 7mm (originally 5mm), a large-sized weight-reducing hole is created in the middle (with thickened flanged edges ≥4mm), and the bottom transition area is thinned to approximately 4mm. This can form an "I"-shaped or "double-peak" topology, with a weight reduction potential of >30%.

[0057] The lightweight optimization of the top or side shell involves minimizing mass under in-plane stiffness constraints by incorporating longitudinal main ribs, transverse corrugated ribs, and diagonal mesh ribs, and reducing the thickness of the shell base. Specifically, the top shell can form longitudinal main ribs (along the cylinder centerline, height ≈ 5 mm) and transverse corrugated ribs (in the arched area, height ≈ 4 mm), reducing the shell thickness to ≈ 2.5-3.0 mm (from the original 3 mm); the side shell can form diagonal mesh ribs (to transfer shear force, rib height ≈ 4 mm), reducing the shell thickness to ≈ 2.5 mm; and thickening the flange edges (5-6 mm); the weight reduction potential is ≈ 20%.

[0058] The base flange is optimized for lightweight design by minimizing weight under bolt stiffness constraints. Local bosses are installed around the bolt holes, and the flange body adopts a corrugated or grid-like structure. Specifically, local bosses (thickness ≈ 8mm) are formed around the bolt holes, and the flange body adopts a corrugated or grid-like structure with an average thickness ≈ 4mm (originally 5mm); the weight reduction potential is ≈15%.

[0059] Furthermore, in the topology optimization step S4, the integrated design of the lubricating oil passage, cooling water passage, sensor mounting base, and accessory mounting base is completed simultaneously. The lubricating oil passage is embedded inside the reinforcing rib, and the sensor and accessory mounting base is designed as a locally thickened boss fused with the main rib. The specific integrated functional features are as follows: the lubricating oil passage is embedded in the main bearing diaphragm rib or the top longitudinal rib, with a minimum hole diameter of φ6mm and a wall thickness ≥2.5mm; the cooling water passage can be arranged around the cylinder liner and inside the cylinder wall, designed as a pressure vessel (wall thickness ≥4mm); the sensor / accessory base can be set as a locally thickened boss fused with the main rib.

[0060] In addition, after the topology optimization is completed in step S4, the topology optimization results are converted into a parametric CAD (Computer-Aided Design) model, and a shell element finite element model of the crankcase is generated (that is, the topology optimization results are converted into a parametric CAD model and a shell element finite element model is generated), which is used for the comprehensive performance verification in step S5.

[0061] Furthermore, in step S5, the multiple operating conditions include at least: The maximum burst pressure condition LC1 is the condition where the maximum burst pressure, corresponding peak inertial force, and preload of all bolts are applied. The maximum burst pressure condition is the most dangerous, with the maximum pressure Pmax = 14 MPa + corresponding peak inertial force + preload of all bolts under this condition.

[0062] The maximum inertial force condition LC2 is when the maximum reciprocating and rotational inertial forces and bolt preload are applied. The maximum inertial force condition is the condition where the main bearing is subjected to impact, and the maximum inertial force P = 0 + maximum reciprocating / rotational inertial force (including centrifugal force) + bolt preload.

[0063] The whole machine is installed under reaction force condition LC3, which simulates the aircraft maneuvering overload condition. That is, it simulates the aircraft maneuvering overload, such as +4g / -2g.

[0064] Thermo-mechanical coupling condition LC4 refers to the superimposed working temperature field and mechanical load condition. For example, the maximum burst pressure condition LC1 / maximum inertial force condition LC2 load superimposed temperature field (cylinder 150°C, box average 80°C).

[0065] Furthermore, in step S5, the static strength check needs to verify that the maximum stress in the crankcase under each working condition is ≤75MPa. Specifically, it is necessary to calculate the equivalent stress of the normal form under each working condition (LC1, LC2, LC3, LC4). The maximum normal form equivalent stress is required to have the following relationship: (Taking a crankcase made of cast aluminum 105A as an example, the safety factor is 1.67).

[0066] In addition, special attention should be paid to the area around the cylinder liner mounting flange bolt holes, the rounded transition area of ​​the main bearing housing (R≥1.5t), the top of the cylinder wall and the edge of the weight reduction hole, and the root of the main bearing diaphragm rib.

[0067] Furthermore, in step S5, the stiffness check needs to verify that the axial deformation of the main bearing housing, the flatness of the cylinder liner mounting surface, and the torsional stiffness of the entire gearbox meet the preset targets.

[0068] Specifically, stiffness verification may include main bearing seat displacement verification: that is, extracting the relative displacement of the main bearing bore center along the crankshaft axis (Y direction) under the maximum burst pressure condition LC1. (i.e., axial deformation of the main bearing housing). The maximum relative displacement is required to have the following relationship: Equation (12); Stiffness verification may also include cylinder liner mounting surface flatness: that is, extracting the Z-direction displacement of several points on the cylinder liner mounting surface under the maximum burst pressure condition LC1, calculating the maximum deviation ΔZ relative to the best fitting plane, and requiring the maximum deviation ΔZ ≤ 0.03mm.

[0069] Stiffness verification may also include torsional stiffness verification: that is, fixing the oil pan flange, applying a torque T to the flywheel end, and measuring the torsion angle of the flywheel end relative to the flange. The stiffness is calculated as follows: Equation (13); Requirements .

[0070] Furthermore, in step S5, the high-cycle fatigue strength verification uses the SN curve modified by cast aluminum material and combines it with the Goodman mean stress correction criterion to verify that the fatigue safety factor is ≥1.5.

[0071] Specifically, in this embodiment, the high-cycle fatigue strength verification uses the modified SN curve of cast aluminum 105A (considering casting defects). It can be seen that the maximum principal stress at the key point (stress concentration point) is... as follows: Equation (14); and The mean stress correction adopts the Goodman criterion: in, , For average stress, Then the maximum principal stress at the key points (stress concentration points) can be checked. as follows: Equation (15).

[0072] In addition, stiffness checks may include checks for weakening openings (ASME standard reference): for critical openings (weight reduction holes, oil holes), calculate the net section stress and check it after applying the stress concentration factor Kt (FEA or empirical formula), requiring... .

[0073] Furthermore, in step S5, the buckling stability of the thin shell is checked using linear eigenvalue buckling analysis to verify that the minimum buckling load factor is ≥1.5.

[0074] Specifically, when checking the stability (buckling) of thin-shell structures, it is necessary to first analyze the operating conditions: namely, the maximum burst pressure condition LC1 (maximum surface pressure) and the thermo-mechanical coupling condition LC4 (thermal pressure). The linear eigenvalue buckling analysis method is used. Furthermore, the specific calculation steps are as follows: Static analysis was performed on the maximum burst pressure condition LC1 and the thermo-mechanical coupling condition LC4 to obtain the structural stress state and geometric stiffness matrix, and the buckling characteristic equation was solved as follows: Equation (16); in, It is the stiffness matrix. It is the geometric stiffness matrix. It is an eigenvalue. buckling mode; Furthermore, the buckling load factor (BLF): ; Minimum buckling load factor required (Safety factor).

[0075] Areas requiring attention include large flat or low-curvature areas (top panel, large side panels), and areas with varying thickness transitions. Thin-plate areas between stiffeners, and thin-walled areas around weight-reduction holes. The improvement strategy is: if... Then it is necessary Increase the density or height of local stiffeners, slightly increase the thickness of local plates, and optimize the direction of stiffeners to improve the critical buckling load.

[0076] Furthermore, in step S6, the weight calculation is specifically as follows: Based on the optimized solid model volume, the weight of the finished product is calculated by combining the density of the cast aluminum material and the blank allowance coefficient, where the blank allowance coefficient is taken as 1.15.

[0077] When calculating weight, the volume V(m) of the optimized structure's solid model can be extracted from the CAD model. 3 Material density (Cast aluminum 105A), calculate weight (k is the casting blank allowance coefficient, including draft and machining allowance, and is taken as k=0.15).

[0078] The target verification is W≤3.8kg; if not, the thickness of non-critical areas or the height of stiffeners are adjusted iteratively (within the strength, stiffness, and buckling constraint boundaries).

[0079] Furthermore, in step S6, the casting process adaptability adjustment specifically includes: Set a draft angle of ≥1° for all vertical walls, use a gradual transition for the wall thickness of adjacent areas, with the transition zone length being ≥3 times the thickness difference, set a fillet transition of ≥1.5mm for all internal corners, set a fillet transition of ≥2.0mm for external corners, and set a fillet radius of ≥3mm for high-stress areas. At the same time, control the casting hot spots (avoid the isolation or convergence of thick areas, and set chills or optimize risers if necessary).

[0080] Furthermore, in this embodiment, the crankcase can be made of cast aluminum 105A or A356 cast aluminum alloy and designed and manufactured in the T6 heat-treated state. For example, when the crankcase is made of cast aluminum 105A (AlSi7MgCu1) and designed and manufactured in the T6 heat-treated state, , , , , .

[0081] The overall dimensions of the crankcase can then be as follows: length 250mm, width 200mm, and height 150mm. Furthermore, the optimized key structural parameters are as follows: Among them, the top shell has an arch height of H=12mm; main ribs: 2 longitudinal ribs (along the cylinder center line), 5mm high, 8mm wide at the top, and 12mm wide at the bottom; transverse corrugated ribs: 3 ribs, 4mm high, 50mm long, and the shell plate thickness is 2.8mm. Cylinder wall: Top thickness 7mm (rounded corner R=4mm), middle weight-reducing elliptical hole (80x40mm), hole edge flange thickness 4.5mm, height 5mm, bottom thickness 4.0mm; Main bearing partition: 4 radial main ribs (extending to the cylinder wall and side), 8mm high and 6mm wide; bearing housing bearing ring thickness 10mm, bottom plate thickness 4mm, and rib plate thickness 3.2mm. Side shell: 45° diagonal grid ribs (rib spacing ≈ 40mm), 4mm high, 5mm wide, shell plate thickness 2.7mm, connecting flange thickness to top shell and base 5mm; Base flange: corrugated structure (wave depth 5mm, wavelength 60mm), average thickness 4.2mm, bolt hole boss (diameter φ20mm), thickness 8mm; Cylinder liner mounting flange: final optimized thickness 7.5mm (with local countersinking for weight reduction), 8mm around bolt holes; Main bearing cap: Independently designed, with precision-machined mating surfaces with the main bearing housing, and tightened by four M10 transverse bolts (preload 35kN / bolt).

[0082] Integrated structure: The main lubrication channel is integrated into the longitudinal main rib on the top surface (φ8mm), and the branch pipe is embedded in the main bearing partition rib (φ6mm); the upper cooling water jacket of the cylinder liner is integrated around the cylinder liner boss with a wall thickness of 4mm; the oil pressure sensor seat and speed sensor seat are integrated into the boss at the intersection of the diagonal ribs on the side housing.

[0083] Furthermore, in this embodiment, the FEA (Finite Element Analysis) verification results are as follows: Maximum stress in LC1 under maximum burst pressure condition: 73MPa (located at the root of the main bearing housing fillet) < 75MPa; Stress at the top of the cylinder wall: 68MPa; Y-direction displacement of the main bearing housing: 0.018mm < 0.02mm; Flatness of the cylinder liner mounting surface: 0.022mm < 0.03mm; Torsional stiffness: 5500Nm / deg > 5000Nm / deg; Minimum buckling load factor (BLF): 1.65 > 1.5 (occurring in the middle of the large side panel); Weight calculation: Model volume V ≈ 1250cm³ 3 The weight of the blank is W = 27000.001251.15 ≈ 3.88 kg (meets the requirements).

[0084] The lightweight optimization method for crankcases of aero-piston engines proposed in this invention can systematically apply thin-shell theory and topology optimization to eliminate redundant materials and achieve an extremely low weight of 3.8 kg for cast aluminum structures, realizing ultimate lightweighting. Based on the characteristics of thin shells, force flow can be guided, resulting in uniform stress distribution, significantly reduced stress concentration, and greatly improved stiffness, leading to excellent mechanical properties. It provides a complete process from theoretical analysis to optimized design, reducing trial-and-error costs and improving design efficiency. Through rigorous strength, stiffness, and stability checks, it ensures that the high reliability requirements of aero-engines are met, i.e., high reliability. The design fully considers casting process constraints, resulting in strong manufacturability and good process adaptability.

[0085] Furthermore, this invention also proposes an aero-piston engine crankcase, which is designed and manufactured using the lightweight optimization method for aero-piston engine crankcases described above. In this embodiment, the lightweight aero-piston engine crankcase designed based on thin-shell theory can be die-cast from cast aluminum 105A or cast aluminum A356. While ensuring sufficient strength, rigidity, and stability, the total weight of the crankcase made from cast aluminum 105A or cast aluminum A356 can be reduced to 3.8 kg, a 70% weight reduction compared to traditional technologies.

[0086] like Figures 2 to 5 As shown, the crankcase may include a crankcase body and various auxiliary structures disposed on the crankcase body. Furthermore, the crankcase body may include a thin-shell closed curved surface 1 and reinforcing ribs 2. The thin-shell closed curved surface 1 forms the upper housing 4 and the lower housing 5, and the reinforcing ribs 2 are disposed on the upper housing 4 and the lower housing 5. Various auxiliary structures may include lubrication channels 3, bearing mounting holes 6, crankcase bolts 7, gear oil pump housing 8, oil pump outlet 9, oil pump inlet 10, built-in bearing lubrication distribution channels 11, main lubricating oil inlet 12, fuel pump mounting base 13, main bearing lubrication channels 14, bearing studs 15, oil pump mounting studs 16, etc.

[0087] Furthermore, the upper housing 4 and the lower housing 5 are clamped together by bearing studs 15 and crankcase bolts 7. Based on stress analysis, appropriate bolt diameters and lengths are selected, and the bolts are evenly distributed on the mating surfaces of the crankcase. In addition, the required bolt preload is precisely calculated using thin-shell theory and finite element analysis to ensure the sealing and rigidity of the mating surfaces. Reinforcing ribs and supporting structures are added at the mating surfaces to ensure overall rigidity and stability.

[0088] In addition, the fuel pump is mounted on the fuel pump mounting base 13 of the upper housing 4 and is fixed by the fuel pump mounting studs 16 on the mounting base. Lubricating oil can enter the engine from the main lubricating oil inlet 12, and flow into the main bearing lubricating oil passage 14 through the built-in bearing lubrication distribution oil passage 11 in the crankcase to lubricate the main bearing.

[0089] In addition, such as Figure 3 As shown, the bearing shell is installed in the bearing shell mounting hole 6, and the contact surface between the bearing shell and the crankshaft is lubricated by the main bearing shell lubrication oil passage 14. Reinforcing ribs are designed around the bearing shell hole to enhance the strength and rigidity of the crankcase and prevent deformation of the area around the hole during operation. A main oil passage is designed along the length of the crankcase inside to ensure that lubricating oil can effectively reach all lubrication points. Branch oil passages are led out from the main oil passage to each lubrication point. Appropriate reinforcing ribs are used to enhance the structural strength.

[0090] In addition, the crankcase integrates the gear oil pump housing 8, oil pump outlet 9, and oil pump inlet 10 for lubrication. The gear pump housing is directly cast into the crankcase, reducing the number of parts and assembly complexity. In a thin-shell structure, ensuring the sealing of the oil passages and the thin shell is crucial.

[0091] The beneficial effects of the technical solution provided by this invention include: 1. The structure of the crankcase of an aero-piston engine was optimized using thin-shell theory to achieve weight reduction requirements. In the finite element analysis, various load conditions during the operation of the aero-piston engine were simulated, including gas pressure, inertial force, and thermal stress. The crankcase was designed as a structure composed of curved thin-shell units. Through optimization, the weight of the crankcase was reduced by approximately 25%.

[0092] 2. Despite the weight reduction, thin-shell theory ensures the structural strength of the crankcase by optimizing the structural shape and stress distribution. Stress concentration and fatigue life were considered in the design, enabling the crankcase to withstand high-load operating conditions while maintaining a lighter weight, thus extending its service life. Strength and stiffness calculations were performed using thin-shell theory, and the design was verified through finite element analysis, ensuring its reliability.

[0093] 3. The thin-shell design helps absorb and disperse vibrations generated during engine operation, reducing noise. Through meticulous optimization of the crankcase shape and materials, the overall vibration and noise levels of the engine can be effectively reduced, improving flight comfort and environmental friendliness.

[0094] 4. Due to the reduced material usage, the crankcase designed based on thin-shell theory has a significant decrease in raw material costs. At the same time, the optimized structural design simplifies manufacturing and assembly processes, reduces production time and labor costs, and lowers overall manufacturing expenses.

[0095] 5. The thin-shell structure design facilitates more efficient heat dissipation. By optimizing the heat dissipation area of ​​the crankcase surface and the airflow path, heat can be dissipated more quickly, keeping the engine operating within its optimal temperature range and improving performance and reliability.

[0096] 6. Due to the reduced overall weight, the engine requires less thrust, directly improving fuel efficiency. Higher fuel efficiency not only reduces operating costs but also decreases carbon emissions, contributing to environmental protection and sustainable development.

[0097] 7. By optimizing stress distribution through thin-shell theory, stress concentration and fatigue crack formation are reduced. The crankcase exhibits better fatigue resistance during long-term use, extending maintenance cycles and service life, and reducing maintenance and replacement costs.

[0098] 8. The thin-shell structure design offers better environmental adaptability, enabling stable operation under harsh conditions such as high temperature, high pressure, and vibration. This enhanced environmental adaptability allows the engine to maintain excellent performance under different flight conditions, improving reliability and safety.

[0099] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0100] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0101] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A method for optimizing the lightweight design of an aircraft piston engine crankcase, characterized in that, include: S1. Obtain the core design objectives, displacement boundary conditions, and load boundary conditions of the crankcase of an aero-piston engine; wherein, the core design objectives include weight objectives, strength objectives, stiffness objectives, high-cycle fatigue strength objectives, manufacturability objectives, and functional integration objectives; S2. Establish an initial thin-shell model of the crankcase, and verify and divide the initial thin-shell model into regions using thin-shell theory. That is, based on the initial envelope size of the initial thin-shell model of the crankcase, verify the ratio of shell thickness to radius of curvature, and divide the crankcase into thin-shell regions that meet the application conditions of thin-shell theory, and thick-shell regions or combined shell regions that do not meet the application conditions of thin-shell theory. S3. Analyze the load transfer path of the crankcase, construct the main load-bearing topology of the crankcase based on the in-plane bearing characteristics of the thin shell, and estimate the initial thickness and structural dimensions of the key areas of the crankcase in combination with thin shell theory. S4. With minimizing structural mass as the optimization objective and strength, stiffness, natural frequency, manufacturing process, and thin-shell stability as constraints, perform regional topology optimization on the key areas of the crankcase to obtain the optimized crankcase shell structure, stiffener layout, and thickness distribution. S5. Establish a finite element model for the optimized crankcase, and verify the static strength, stiffness, high-cycle fatigue strength and thin-shell buckling stability of the finite element model under multiple working conditions. S6. Calculate the finished weight of the crankcase that has passed the verification. If the weight does not meet the target requirements, iteratively optimize the structural parameters within the performance constraint boundary, and at the same time complete the casting process adaptability adjustment to obtain the final crankcase model.

2. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 1, characterized in that, In step S1, the displacement boundary conditions include the Z-direction constraint of the crankcase oil pan mounting surface, the X and Y-direction rotational constraints and the Z-direction sliding constraint of the crankcase flywheel housing mounting surface to simulate thermal expansion, and the X, Y, and Z-direction constraints of the crankcase front cover mounting surface. The load boundary conditions include the maximum burst pressure inside the cylinder, the reciprocating and rotational inertial forces of the piston assembly and connecting rod, the preload of the cylinder head bolts and main bearing cap bolts, accessory loads, and the thermal load caused by the temperature gradient in the cylinder region.

3. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 1, characterized in that, In step S2, the criterion for verifying the initial thin-shell model using thin-shell theory is that the ratio of the shell thickness t of the initial thin-shell model of the crankcase to the local minimum radius of curvature Rmin is t / Rmin≤0.

1. The cylinder region of the initial thin-shell model is treated as a thick-shell region or a combined shell region, while the remaining regions with a curvature radius R > 80 mm are designed as thin-shell regions.

4. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 1, characterized in that, In step S3, the load transmission path is specifically as follows: the gas force inside the engine cylinder is transmitted from the cylinder liner to the cylinder liner mounting flange, through the top housing, cylinder block, main bearing partition, main bearing seat, and side housing to the base flange or oil pan flange, and finally to the engine mounting bracket through the crankcase base bolts. The main load-bearing topology includes the top shell of the crankcase, the inter-cylinder load-bearing partition, the main bearing partition, the side shell, and the base flange or oil pan flange; wherein, the top shell is a continuous curved surface shell with an arch height, and the arch height is 1 / 10 to 1 / 8 of the cylinder center distance.

5. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 4, characterized in that, In step S3, the key areas include the cylinder liner mounting flange, cylinder wall, main bearing housing, top shell, side shell, base flange or oil pan flange. Using the formulas for calculating the stiffness and stress of annular plates, pressure plates and cylindrical shells based on thin shell theory, the initial thickness of each area is estimated.

6. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 1, characterized in that, In step S4, the constraints for topology optimization specifically include: Strength constraints: stress in each region ≤ 75 MPa; Stiffness constraints: relative displacement of the main bearing housing along the crankshaft axis ≤ 0.02 mm; flatness of the cylinder liner mounting surface ≤ 0.03 mm. Natural frequency constraint: first-order torsional frequency ≥ 1.5 times engine ignition frequency; Manufacturing constraints: minimum wall thickness ≥ 3.0 mm, maximum thickness ≤ 20 mm, draft direction and symmetry constraints; Thin-shell stability constraint, local buckling factor ≥ 1.

5.

7. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 6, characterized in that, In step S4, the regional topology optimization specifically includes: The main bearing partition is optimized for lightweighting, that is, with the goal of maximizing the stiffness-to-mass ratio of the main bearing housing, a radial reinforcing rib structure is formed and a thickened bearing ring is set around the bearing hole. The cylinder wall lightweight optimization aims to achieve stress uniformity by adopting a variable thickness design. The thickness is maintained in the high stress area, a weight reduction hole is opened in the middle and the hole edge is set with a flange, and the thickness is reduced in the bottom transition area. Lightweight optimization of the top or side shell, that is, minimizing the mass under in-plane stiffness constraints, by setting longitudinal main ribs, transverse corrugated ribs and diagonal mesh ribs, and reducing the thickness of the shell plate foundation; The base flange is optimized for lightweight design, which means minimizing weight under bolt stiffness constraints, setting local bosses around the bolt holes, and adopting a wave-shaped or grid-like structure for the flange body.

8. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 7, characterized in that, After the topology optimization is completed in step S4, the topology optimization results are converted into a parametric CAD model, and a shell element finite element model of the crankcase is generated for comprehensive performance verification in step S5.

9. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 7, characterized in that, In the topology optimization in step S4, the integrated design of lubricating oil channels, cooling water channels, sensor mounting bases and accessory mounting bases is completed simultaneously. The lubricating oil channels are embedded inside the reinforcing ribs, and the sensor and accessory mounting bases are designed as locally thickened bosses that are integrated with the main ribs.

10. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 1, characterized in that, In step S5, the multiple operating conditions include at least: Maximum burst pressure condition LC1, which is the application of maximum burst pressure, corresponding peak inertial force and all bolt preload; The maximum inertial force condition LC2 refers to the application of the maximum reciprocating and rotational inertial force and the bolt preload. The whole machine installation reaction force condition LC3 is a simulation of the aircraft maneuver overload condition; Thermo-mechanical coupling condition LC4 refers to the superimposed working temperature field and mechanical load condition.

11. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 10, characterized in that, In step S5, the static strength check needs to verify that the maximum stress of the crankcase under each working condition is ≤75MPa; The stiffness check needs to verify that the axial deformation of the main bearing housing, the flatness of the cylinder liner mounting surface, and the torsional stiffness of the entire gearbox meet the preset targets. The high-cycle fatigue strength verification adopts the modified SN curve of cast aluminum material, combined with the Goodman mean stress correction criterion, to verify that the fatigue safety factor is ≥1.5; The buckling stability of the thin shell was checked using linear eigenvalue buckling analysis, which verified that the minimum buckling load factor was ≥1.

5.

12. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 1, characterized in that, In step S6, the weight calculation specifically involves: Based on the optimized solid model volume, the weight of the finished product is calculated by combining the density of the cast aluminum material and the blank allowance coefficient, where the blank allowance coefficient is taken as 1.

15.

13. The method for lightweight optimization of the crankcase of an aero-piston engine according to claim 12, characterized in that, In step S6, the casting process adaptability adjustment specifically includes: Set a draft angle of ≥1° for all vertical walls, adopt a gradual transition for the wall thickness of adjacent areas, with the transition zone length being ≥3 times the thickness difference, set a fillet transition of ≥1.5mm for all internal corners, set a fillet transition of ≥2.0mm for external corners, and set a fillet radius of ≥3mm for high-stress areas, while controlling the casting hot spot.

14. A crankcase for an aircraft piston engine, characterized in that, The crankcase of the aircraft piston engine is designed and manufactured using the lightweight optimization method for the crankcase of the aircraft piston engine as described in any one of claims 1-13.

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