The transmission in automobiles is the core component to ensure operational stability. Heat accumulation in the meshing process will reduce the transmission efficiency and affect the service life. Here, the essential physical process to improve transmission heat dissipation is the dynamic evolution process and the thermal transfer characteristics of lubricating oil fields during gear meshing. This paper presents a modeling and solving method for gear meshing lubrication and thermal transfer features based on the volume of the fluid model and piecewise linear interface construction (VOF-PLIC). The dynamic mesh technique combines spring smoothing and reconstruction to optimize the numerical solution process. The dynamic evolution law of gear meshing lubrication and thermal transfer is obtained by analyzing the lubrication evolution process under different speed/steering conditions. The results show that the proposed modeling and solving method could well reveal the lubrication and thermal transfer laws of the gear meshing. The temperature of the gear meshing regions was higher than that in the other regions, and the lubrication temperature showed an increasing linear trend with the stirring process. As the gear speed increased, the meshing resistance moment increased, the transmission power loss increased, and the lubrication oil temperature was larger than that of the gearbox. The power loss under the clockwise rotation of the driving gear G4 was higher than that under the counterclockwise rotation of the driving gear. The relevant results can provide theoretical references for the dynamic analysis of automotive transmission lubrication and technical support for gear profile design and lubrication optimization.

The gear transmission system occupies a core position in mechanical equipment due to its numerous advantages such as high efficiency, high reliability, and long durability, making it an indispensable key component. Investigating the distribution mechanism of the two-phase flow field in gear transmission systems and its optimization design strategies is crucial for enhancing the efficiency and reliability of gearboxes. This paper couples the Lattice Boltzmann Method (LBM) with Large Eddy Simulation (LES) to construct a dynamic modeling and solution method suitable for the lubrication flow field of high-speed gears with baffles. The core objective is to explore the distribution mechanism and dynamic characteristics of the lubrication flow field in gears with baffles. Based on the LBM–LES coupled model, this paper sets up a two-phase flow dynamic model for the high-speed gear lubrication flow field. By conducting a detailed analysis of the dynamic evolution of the lubrication process in the gearbox with the presence of baffles, this study reveals the changing patterns of flow field dynamics under different flow velocities and configurations of mixing components. The research findings indicate that when the radial speed of the gears reaches 8 m/s, a stable oil film can be formed on the gear surface, which is crucial for ensuring smooth operation and reducing wear. Additionally, it has been confirmed that larger baffle diameters and hole diameters can effectively increase the enthalpy of the fluid, thereby optimizing energy transfer and thermal performance. However, it is noted that a larger baffle diameter is not always better; when it exceeds a certain limit, the performance improvement effect gradually diminishes, indicating the existence of an optimal baffle diameter value. By optimizing the design of the baffle, the flow characteristics and energy dissipation of the fluid within the gearbox can be controlled, improving thermal management and lubrication performance. These research findings provide valuable references for the lubrication design and optimization of gear transmission systems in high-tech fields such as aviation and aerospace. They can help relevant technicians gain a deeper understanding of the complex mechanisms involved in the lubrication process, allowing for the design of more efficient and reliable lubrication systems, effectively enhancing the performance of the entire transmission system, and promoting progress and development in related technological fields.

The detailed unsteady turbulent flow inside a centrifugal fan and its downstream pipe was studied using detached eddy simulation (DES) at three flowrates, namely, the best efficiency point (BEP), 0.75BEP, and 1.49BEP. Both the mean and fluctuating flow fields were analyzed on the basis of the root-mean-square value as the indication of fluctuating intensity. Results showed that the pressure fluctuation had the minimum value at BEP, but the velocity fluctuation increased with the flowrate. Most regions inside the centrifugal fan underwent large pressure fluctuation with the magnitude of about 10~20% of p_ref = 0.5 ρu₂², where u₂ is the blade velocity at the impeller outlet. The pressure fluctuation had a maximum value at the impeller side of the tongue tip rather than the stagnation point, and it decreased rapidly along the outlet pipe with magnitude about 1% of p_ref after distance of five pipe diameters. The spectra of hydrodynamic pressure showed conspicuous spikes at the blade passing frequency (BPF) in the volute but not in the downstream pipe. At the downstream pipe entrance, pressure fluctuation spectra agreed with experimental results, showing that hydrodynamic pressure fluctuations were dominant; however, the experimental data showed a much slower decreasing rate due to the acoustic fluctuations.

In response to the growing demand for lightweight and high-efficiency industrial equipment, this study addresses the critical issue of lubrication failure in high-speed, heavy-duty gear reducers, which often leads to reduced transmission efficiency and premature mechanical damage. A three-dimensional transient multiphysics-coupled model of oil-jet lubrication is developed based on computational fluid dynamics (CFD). The model integrates the Volume of Fluid (VOF) multiphase flow method with the shear stress transport (SST) k−ω turbulence model. This framework enables the accurate capture of oil-jet interface fragmentation, reattachment, and turbulence-coupled behavior within the gear meshing region. A parametric study is conducted on oil injection velocities ranging from 20 to 50 m/s to elucidate the coupling mechanisms between geometric configuration and flow dynamics, as well as their impacts on oil film evolution, energy dissipation, and thermal management. The results reveal that the proposed method can reveal the dynamic evolution characteristics of the gear injection lubrication. Adopting an appropriately moderate injection velocity (30 m/s) improves oil film coverage and continuity, with the lubricant transitioning from discrete droplets to a dense wedge-shaped film within the meshing zone. Optimal lubrication performance is achieved at this velocity, where oil shear-carrying capacity and kinetic energy utilization efficiency are maximized, while excessive turbulent kinetic energy dissipation is effectively suppressed. Dynamic monitoring data at point P further corroborate that a well-tuned injection velocity stabilizes lubricant-velocity fluctuations and improves lubricant oil distribution, thereby promoting consistent oil film formation and more efficient heat transfer. The proposed closed-loop collaborative framework—comprising model initialization, numerical solution, and post-processing—together with the introduced quantitative evaluation metrics, provides a solid theoretical foundation and engineering reference for structural optimization, energy control, and thermal reliability design of gearbox lubrication systems. This work offers important insights into precision lubrication of high-speed transmissions and contributes to the sustainable, green development of industrial machinery.

Brake noise, a principal component of vehicle noise, is among the most critical measures of vehicle quality. The perceived quality of cars can be improved by reducing brake noise; therefore, vehicle manufacturers are extensively investigating the influencing factors, generating mechanism, and solutions of brake noise. Compressive strain is one of the most influential performance parameters of a brake pad and can be adjusted by regulating the material elastic modulus and by modifying the shape of the brake lining. In this study, the compressive strain of a brake pad was adjusted through four methods, and the noise characteristics of brake pads with different elastic modulus, section outlines, lining widths, and chamfers were studied through finite element analysis and the complex-eigenvalue method. The effects of compressive strain of a brake pad on brake noise were examined, and an optimized brake-pad scheme was developed. A dynamometer test conducted to validate the effectiveness of the optimized scheme confirmed a clear alleviation in brake noise.

Brake noise is one of the principal components of vehicle noise and is also one of the most critical measures of vehicle quality. During the braking process, the occurrence of brake noise has a significant relationship with the working conditions of the brake system. In the present study, dynamometer test data and the finite element method (FEM) were used to analyze the direct and indirect effects of variations in the working parameters on the brake noise, and a brake noise reduction method was developed. With this method, Monte Carlo sampling was used to consider variations in the parameters of the brake lining during the braking procedure, and the particle swarm optimization method was used to calculate the optimal parameter combination for the brake lining. A dynamometer test was carried out to validate the effect of optimization on brake noise mitigation.