A method for judging advantages and disadvantages of an engine rear end gear train scheme based on angular acceleration level

Abstract

This invention discloses a method for judging the merits of engine rear-end gear system designs based on angular acceleration levels, belonging to the technical field of engine gear transmission system design verification. The method includes: establishing a rigid-flexible coupling dynamic model of the engine rear-end gear system, determining three typical operating conditions: idle speed, rated power point, and common operating speed; performing rigid-flexible coupling dynamic simulation analysis on four design schemes: internal straight-external skew, double skew, maximum overlap, and internal large-external small; extracting angular velocity time history data for the four schemes under the three operating conditions; numerically differentiating the angular velocity data to obtain angular acceleration, and then calculating the angular acceleration level and total angular acceleration level; by comparing the total angular acceleration levels of the four schemes under different operating conditions, selecting the gear system design scheme with optimal dynamic performance. This invention directly uses angular acceleration level as an evaluation index, which can more purely and sensitively reflect the meshing quality of the gear system, avoiding the shortcomings of traditional housing vibration signal transmission paths and interference, realizing quantitative evaluation of the dynamic performance of gear system schemes during the design stage, and providing a reliable basis for low-vibration and low-noise design of engine gear systems.

Description

Technical Field

[0001] This invention relates to the field of engine gear transmission system design verification technology, and more specifically, to a method for judging the merits of engine rear gear system design schemes based on angular acceleration levels. Technical Background

[0002] The rear-end gear train of an engine is one of the core components of high-end power plants such as aero-engines and high-speed heavy-load transmission equipment. It is responsible for transmitting the power and speed of the core engine to the accessory gearbox and various engine accessories. As engines develop towards higher power density and higher thrust-to-weight ratio, the working environment of the gear train is becoming increasingly harsh, and its dynamic performance directly affects the reliability, vibration and noise levels, and even service life of the entire engine. Therefore, accurately evaluating the dynamic performance of the gear train during the design phase and selecting the optimal gear train design scheme is a key step in ensuring the overall performance of the engine. Traditional simulation analysis and experimental verification are disconnected. Current dynamic simulations are mostly based on frequency domain analysis, evaluating the system response by calculating transmission errors and meshing stiffness excitations. However, in actual physical experiments, these internal excitations are difficult to measure directly and accurately, making it difficult to effectively calibrate and correct the simulation results through experiments.

[0003] The present invention is proposed based on the above-mentioned technical background, and aims to improve gear meshing performance and reduce engine radiated noise by using a method for judging the merits of engine rear gear system design schemes based on angular acceleration signals. Summary of the Invention

[0004] The purpose of this invention is to provide a method for judging the merits of a gear system design at the rear end of an engine. By introducing the concept of "angular acceleration stage", this invention solves the problem that existing technologies cannot directly judge the merits of a gear system design through angular acceleration.

[0005] The technical solution of this invention provides a method for judging the merits of an engine rear-end gear system design based on angular acceleration stages, mainly including the following steps: (1) Establish a dynamic model of the engine rear gear system and determine typical analysis conditions. First, based on the structural parameters and material properties of the engine's rear-end gear system, a precise geometric model including all gears, drive shafts, and support structures is established in 3D modeling software. This model is then imported into dynamics simulation software to establish a rigid-flexible coupled multibody dynamics model. Simultaneously, typical analytical conditions for judging the merits of different gear system designs are determined, specifically including the engine's idling condition (representing low-speed no-load conditions), rated power point condition (representing full-load output conditions), and commonly used speed condition (representing the engine's long-term stable operating speed range). These three conditions cover the main operating range of the engine from start-up to full load, enabling a comprehensive evaluation of the gear system's dynamic performance under different loads and speeds.

[0006] (2) Four comparison schemes were determined and rigid-flexible coupling dynamic simulation analysis was performed. To comprehensively evaluate the impact of different design concepts on the dynamic performance of gear systems, four representative gear system layouts and parametric design schemes were selected for comparative study: the inner spur and outer helical scheme (inner gears use spur teeth, outer gears use helical teeth), the double helical scheme (all main transmission gears use helical teeth), the scheme with maximum contact ratio (designed to optimize tooth profile parameters to improve end face contact ratio), and the inner-large and outer-small scheme (differentiated design with a larger module for inner gears and a smaller module for outer gears). Rigid-flexible coupling dynamic simulation analysis was performed on these four schemes. During the analysis, considering the influence of elastic deformation of gears on meshing characteristics under high-speed conditions, key gears needed to be made flexible in Ansys software. Modal neutral files (MNF files) containing gear natural frequencies and mode shapes were generated through modal solving. The generated MNF files were imported into Adams dynamics software, and the original rigid gear model was replaced with a flexible body to establish a rigid-flexible coupling dynamic model that more closely approximates the actual physical prototype. Furthermore, the dynamic responses of the four schemes under three typical operating conditions were simulated and solved.

[0007] (3) Extract angular velocity data for four different schemes at three typical rotational speeds. After the simulation calculations are completed, the post-processing module extracts angular velocity time history data for four different gear system schemes (inner straight, outer helical, double helical, maximum overlap, and inner large, outer small) under idling, rated power point, and common speed conditions. The extracted measurement points are usually located at the critical output end or vibration-sensitive position of the gear system for subsequent data analysis.

[0008] (4) Taking the inner straight and outer oblique scheme as an example, calculate the angular acceleration level of the intake camshaft gear under idling conditions. To clearly illustrate the data processing flow of this invention, the calculation process of the angular acceleration stage is explained in detail using the intake camshaft gear of the inner straight and outer oblique scheme under idling conditions as an example. The specific flow is as follows: First, the angular velocity of the intake camshaft gear over time is derived from the Adams simulation results. Second, the extracted angular velocity data is numerically differentiated to calculate the angular acceleration over time curve. Then, based on the calculated angular acceleration time-domain signal, the angular acceleration level and total angular acceleration level are quantified according to relevant standards for acoustic and vibration analysis. By comparing these quantified indicators horizontally, the dynamic performance of different gear system designs can be objectively judged from the perspective of vibration energy excitation. The specific process is as follows: % Calculate angular acceleration (rad / s²) n = length(angular_velocity); angular_acceleration = zeros(size(angular_velocity)); % Using the central difference method for i = 2:n-1 dt = time(i+1) - time(i-1); if dt > 0 angular_acceleration(i) = (angular_velocity(i+1) - angular_velocity(i-1)) / dt; end Calculate the angular acceleration level, which is: 10 times the logarithm of the square of the angular acceleration. % Calculate the angular acceleration level (10 times logarithm) epsilon = 1e-10; % Avoid taking the logarithm of zero angular_acceleration_squared = angular_acceleration.^2 + epsilon; angular_acceleration_level_dB = 10 * log10(angular_acceleration_squared); Calculate the total angular acceleration stage, which is the logarithm of the sum of the squares of the angular accelerations of each gear multiplied by their moments of inertia. % Calculate the total angular acceleration level total_angular_acceleration_level= 10 * log10 angular_acceleration_squared * inertia; Where angular_acceleration represents angular acceleration, angular_acceleration_level represents the angular acceleration level, inertia represents the moment of inertia, and total_angular_acceleration_level represents the total angular acceleration level.

[0009] Ultimately, a method for judging the merits of engine rear-end gear system design schemes was developed. Compared with existing methods for judging the merits of gear system designs, this invention has the following innovative aspects: 1) A new evaluation index for the dynamic performance of gear systems based on "angular acceleration level" is proposed. Traditional methods often use housing vibration acceleration or noise signals to evaluate the quality of gear systems, but these signals have long transmission paths and are prone to interference. This invention directly uses angular acceleration level as the core evaluation index. By differentiating the angular velocity data, angular acceleration information reflecting the torsional vibration characteristics of the shaft system is obtained. Angular acceleration is more sensitive to gear meshing impact and torsional vibration, and can more purely and directly reflect the meshing quality of the gear system itself, avoiding interference from other structural vibrations and fluid noise.

[0010] 2) A comparative evaluation system of "multiple schemes and multiple operating conditions" was constructed. This invention does not evaluate a single design, but systematically identifies four representative design schemes (inner straight and outer oblique, double oblique, maximum overlap, inner large and outer small) and three typical operating conditions (idle speed, rated power point, and common speed). This multi-dimensional comparison system can comprehensively reveal the adaptability of different design concepts across the entire operating range of the engine, avoiding the one-sidedness of evaluation based on a single operating condition or a single scheme, and making the results of "judging the superiority or inferiority" more universal and of greater engineering reference value.

[0011] The beneficial effects of this invention are: 1) By establishing rigid-flexible coupling dynamic models in Ansys and Adams, the dynamic performance of different schemes can be predicted at the design drawing stage, which greatly shortens the R&D cycle and reduces trial and error costs and physical test expenses.

[0012] 2) Angular acceleration is extremely sensitive to nonlinear characteristics such as impact loads, torsional vibration abrupt changes, and tooth backlash during gear meshing. Meanwhile, since the signal originates from the shaft system itself, external interference such as engine casing vibration and combustion noise is effectively avoided, making the evaluation results more realistic and accurate in reflecting the meshing quality of the gear system itself.

[0013] 3) It overcomes the limitations of traditional evaluation methods that only focus on the rated point or a single scheme. By examining the dynamic performance of different schemes across the low, medium, and high speed ranges, it is possible to select robust design schemes that perform well throughout the entire engine operating envelope, thus avoiding the design flaw of "paying attention to one aspect while neglecting another."

[0014] 4) The influence of elastic deformation of gears under high-speed operation on meshing force is considered, making the simulation analysis results closer to the actual operating state of the physical prototype. Compared with traditional rigid body dynamics analysis, the judgment basis (angular acceleration data) of this invention has higher reliability and engineering reference value. Attached Figure Description

[0015] Figure 1 Flowchart of the steps in an embodiment of the present invention; Figure 2 Gear system dynamics model; Figure 3(a) Dynamic load on intake camshaft gear; Figure 3(b) Dynamic load on exhaust camshaft gear; Figure 3(c) Dynamic load on the fuel injection pump gear; Figure 3(d) Dynamic load on air compressor gears; Figure 3(e) Dynamic load on the oil pump gear; Figure 4(a) Dynamic angular velocity of intake camshaft gear; Figure 4(b) Dynamic angular velocity of exhaust camshaft gear; Figure 4(c) Dynamic angular velocity of the first idler gear of the camshaft; Figure 4(d) Dynamic angular velocity of the second idler gear of the camshaft; Figure 4(e) Dynamic angular velocity of the two-stage gear; Figure 4(f) Dynamic angular velocity of the fuel injection pump gear; Figure 4(g) Dynamic angular velocity of crankshaft gear; Figure 4(h) Dynamic angular velocity of the air compressor idler gear; Figure 4(i) Dynamic angular velocity of air compressor gears; Figure 4(j) Dynamic angular velocity of the oil pump idler gear; Figure 4(k) Dynamic angular velocity of the oil pump gear; Detailed Implementation

[0016] This invention relates to a new index for evaluating the dynamic performance of gear systems based on "angular acceleration levels." The specific embodiments of this invention are described in detail below with reference to the accompanying drawings. The following examples are for illustrative purposes only and should not be construed as limiting the invention.

[0017] (1) First, establish a system dynamics model of the engine rear gear system. Taking the timing gear system of a certain type of diesel engine as an example, the gear system includes crankshaft gear, camshaft gear, oil pump gear, fuel pump gear, air compressor gear and intermediate idler gear.

[0018] Based on the design drawings, set the material properties of the gear pair and gear material model, and set the gear rotary pair, contact force, load, and drive.

[0019] Loads are applied to the camshaft gear, oil pump gear, fuel injection pump gear, and air compressor gear, with the crankshaft gear being the drive gear and the camshaft gear load, oil pump gear load, fuel pump gear load, and air compressor gear load being the output loads.

[0020] (2) In order to cope with the complex operating conditions of the engine rear gear system, three operating conditions were selected for simulation analysis: the power point operating condition with high load and high speed, the idle operating condition with low load and low speed, and the commonly used speed operating condition. (3) Establishment of the rigid-flexible coupling dynamic model and replacement of the flexible body: First, using Pro / Engineer (Pro / E) 3D modeling software, accurate CAD models of each gear were established based on the design parameters of the engine's rear gear system. To ensure the compatibility of the model across different simulation platforms, each gear model was saved in Parasolid (*.x_t) format and imported into the finite element simulation platform ANSYS. Modal analysis was performed on each gear in ANSYS to generate a modal neutral file (MNF) containing the gear's natural frequencies and mode shapes. The generated MNF file was imported into the dynamic analysis software ADAMS, and the original rigid gear model was replaced with a flexible body to establish a rigid-flexible coupling dynamic model that accurately reflects the influence of gear elastic deformation.

[0021] (4) Determination and preprocessing of load boundary conditions: In order to ensure the accuracy and comparability of load input during dynamic simulation analysis, it is necessary to standardize the load boundary conditions. The load curves of each gear at an engine speed of 1700 r / min are used as an example for illustration.

[0022] Because the load characteristics of the accessory gears in the gear train are different, their load curves may differ in the time domain. To facilitate convergence and comparative analysis in subsequent simulation calculations, the load curve of the fuel injection pump gear, which has the largest load in the gear train, is used as the time reference. First, the time domain of the five load curves is uniformly adjusted to a range of 0.075s. Then, linear interpolation is used to resample each load curve in the angular domain (x-axis) at crankshaft rotation intervals of 0.01°, ensuring that the load data have consistent data length and correspondence on the same angular domain scale. Finally, the interpolated load curve data is extracted and used as the external load input for the ADAMS dynamic simulation.

[0023] (5) Simulation and solution of multiple schemes under multiple working conditions: After the model is established and the load is input, dynamic simulation calculations are performed on four different gear system design schemes (i.e., internal straight and external helical scheme, double helical scheme, maximum overlap scheme, and internal large and external small scheme) under idling, rated power point, and common speed conditions. After the simulation calculation is completed, the angular velocity time history data of the four schemes under three working conditions are extracted in the post-processing module of ADAMS as the basis for subsequent analysis.

[0024] (6) Quantitative calculation of angular acceleration level and selection of optimal solution: In order to objectively evaluate the dynamic performance of different design schemes, the simulation data needs to be processed in depth. The specific steps are as follows: First, the data on the change of angular velocity of the intake camshaft gear over time were derived from the ADAMS simulation results; Secondly, the extracted angular velocity data is numerically differentiated to calculate the curve of angular acceleration changing with time. Then, based on the calculated angular acceleration time-domain signal, the angular acceleration level and total angular acceleration level are quantitatively calculated according to relevant standards for acoustic and vibration analysis (such as ISO or GB / T standards). Among them, the total angular acceleration level can comprehensively reflect the vibration energy level of the gear over a wide frequency range.

[0025] Finally, by comparing the total angular acceleration level calculation results of the four design schemes under three characteristic speed conditions, the gear system design scheme with the best dynamic performance—the scheme with the lowest total angular acceleration level—can be selected from the perspective of vibration energy excitation, and thus determined as the optimal scheme.

Claims

1. The purpose of this invention is to provide a method for judging the merits of a gear system design at the rear end of an engine. By introducing the concept of "angular acceleration stage", this invention solves the problem that existing technologies cannot directly judge the merits of a gear system design through angular acceleration.

2. The technical solution of the present invention provides a method for judging the merits of an engine rear-end gear system design based on angular acceleration stages, mainly including the following steps: (1) Establish a dynamic model of the engine rear gear system and determine typical analysis conditions. First, based on the structural parameters and material properties of the engine's rear gear system, an accurate geometric model containing all gears, drive shafts, and support structures is established in 3D modeling software. This model is then imported into dynamics simulation software to establish a rigid-flexible coupled multibody dynamics model. Simultaneously, typical analytical conditions for judging the merits of different gear system designs are determined, specifically including the engine's idling condition (representing low-speed no-load state), rated power point condition (representing full-load output state), and commonly used speed condition (representing the engine's long-term stable operating speed range). These three conditions cover the main operating range of the engine from start-up to full load, and can comprehensively evaluate the dynamic performance of the gear system under different loads and speeds. (2) Four comparison schemes were determined and rigid-flexible coupling dynamic simulation analysis was performed. To comprehensively evaluate the impact of different design concepts on the dynamic performance of gear systems, four representative gear system layouts and parametric design schemes were identified for comparative study: the inner straight and outer helical scheme (the inner gears use straight teeth and the outer gears use helical teeth), the double helical scheme (all main transmission gears use helical teeth), the scheme with maximum overlap (the design goal is to optimize tooth profile parameters to improve end face overlap), and the inner large and outer small scheme (a differentiated design with a larger module for the inner gears and a smaller module for the outer gears). Rigid-flexible coupling dynamic simulation analysis was performed on these four schemes. During the analysis, considering the influence of elastic deformation of gears on meshing characteristics under high-speed conditions, the key gears needed to be made flexible in Ansys software. Modal neutral files (MNF files) containing the natural frequencies and mode shapes of the gears were generated through modal solving. The generated MNF files were imported into Adams dynamics software, and the original rigid gear model was replaced with a flexible body to establish a rigid-flexible coupling dynamic model that more closely approximates the actual physical prototype. Furthermore, the dynamic responses of the four schemes under three typical operating conditions were simulated and solved. (3) Extract angular velocity data for four different schemes at three typical rotational speeds. After the simulation calculation is completed, the angular velocity time history data of four different gear system schemes (inner straight and outer helical, double helical, maximum overlap, and inner large and outer small) are extracted in the post-processing module under idling, rated power point and common speed conditions. The extracted measurement points are usually located at the key output end or vibration sensitive position of the gear system for subsequent data analysis. (4) Taking the inner straight and outer oblique scheme as an example, calculate the angular acceleration level of the intake camshaft gear under idling conditions. To clearly illustrate the data processing flow of this invention, the calculation process of the angular acceleration stage is explained in detail using the inner straight and outer oblique scheme for the intake camshaft gear under idling conditions as an example. The specific flow is as follows: First, the angular velocity of the intake camshaft gear over time is derived from the Adams simulation results. Second, the extracted angular velocity data is numerically differentiated to calculate the angular acceleration over time curve. Then, based on the calculated angular acceleration time-domain signal, the angular acceleration level and total angular acceleration level are quantified according to relevant standards for acoustic and vibration analysis. By comparing these quantified indicators horizontally, the dynamic performance of different gear system design schemes can be objectively judged from the perspective of vibration energy excitation. The specific process is as follows: % Calculate angular acceleration (rad / s²) n = length(angular_velocity); angular_acceleration = zeros(size(angular_velocity)); % Using the central difference method for i = 2:n-1 dt = time(i+1) - time(i-1); if dt > 0 angular_acceleration(i) = (angular_velocity(i+1) - angular_velocity(i-1)) / dt; end Calculate the angular acceleration level, which is: 10 times the logarithm of the square of the angular acceleration. % Calculate the angular acceleration level (10 times logarithm) epsilon = 1e-10; % Avoid taking the logarithm of zero angular_acceleration_squared = angular_acceleration.^2 + epsilon; angular_acceleration_level_dB = 10 * log10(angular_acceleration_squared); Calculate the total angular acceleration stage, which is the logarithm of the sum of the squares of the angular accelerations of each gear multiplied by their moments of inertia. % Calculate the total angular acceleration level total_angular_acceleration_level= 10 * log10 angular_acceleration_squared* inertia; Where angular_acceleration represents angular acceleration, angular_acceleration_level represents the angular acceleration level, inertia represents the moment of inertia, and total_angular_acceleration_level represents the total angular acceleration level.

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