Strojniški vestnik - Journal of Mechanical Engineering

Analytical, Numerical 1D and 3D Water Hammer Investigations in a Simple Pipeline Apparatus

2025-04-07T11:49:09+00:00

This paper deals with the analytical and numerical simulation of a water hammer in the reservoir-pipeline-valve (RPV) system. An analytical solution of the water hammer equations with unsteady friction term was derived for transient laminar pipe flow in a RPV system. For simulation of an arbitrary flow situation a number of one-dimensional (1D) numerical methods have been developed. The physically based method of characteristics proved to be computationally efficient and can handle complex boundary conditions. The accuracy of the 1D numerical model is increased by introducing terms that take into account 3D effects (example of an unsteady skin friction). The 3D model predicts these influences directly and represents an excellent tool for researching multidimensional properties of fluids (numerical laboratory). Calculation results based on 1D and 3D numerical models are in good agreement with the results of measurements taking into account adequate prediction and modelling of influential physical parameters during laminar and low-Reynolds number turbulent water hammer events. Quantitative comparison analysis yields up to 2 % difference in maximum head at the valve and up to 5 % relative difference in pressure head drop at the midpoint of the pipeline monitored over the first four positive pressure pulses.

Study on the Influence of the Splitter Blade Length on Radial and Axial Force of a Centrifugal Pump

2025-03-21T07:16:06+00:00

To enhance the operational stability of centrifugal pumps, this study investigates the influence of splitter blade length on the axial and radial forces of centrifugal pumps. Using the SST k-ω turbulence model and experimental research, the external characteristics, axial force, radial force, and time-frequency characteristics of pressure pulsation were compared among impellers without splitter blades and those with splitter blades of two different lengths. The results show that impellers with a conventional structure achieve higher efficiency near the design operating point. However, under low-flow conditions, the rectifying effect of splitter blades allows impellers with splitter blades to achieve higher efficiency. For impellers with splitter blades, the axial force shows a periodic behavior, presenting two peak values — one large and one small — within each cycle. The addition of splitter blades shifts the radial force acting on the impeller to one side, requiring an increase in the support strength and stiffness of the rotor system. Furthermore, splitter blades influence the pressure pulsation at the impeller's inlet and outlet, the original impeller has an additional pulsation energy at 145 Hz but the splitter blades are different. Thus, an impeller with splitter blades can reduce the frequency pulsation and optimizing flow conditions. This study provides valuable theoretical insights and data support for the hydraulic structural optimization of centrifugal pumps.

Multi-Objective Optimization Design of the Ejector Plate for Rear-Loader Garbage Trucks

2025-03-19T14:07:49+00:00

This work presents a multi-objective optimization design approach for the ejector plate, a critical component of rear-loading garbage trucks, with the goal of maintaining structural integrity while optimizing lightweight performance. A parametric finite element model of the ejector plate is developed with optimization objectives focused on minimizing mass, maximizing deformation limits, and reducing the maximum von Mises stress. Through sensitivity analysis, seven key variables are identified as constraints. A Box-Behnken design (BBD) is used to systematically design these parameters, and a Kriging surrogate model is created to approximate the objective function, with performance compared to response surface methodology (RSM). The Non-dominated Sorting Genetic Algorithm II (NSGA-II) is applied to derive the optimal solution, achieving a lightweight design meeting all structural requirements. The results show that the mass of the ejector plate of the rear-loading waste compactor can be reduced by 6.06 % through structural optimization, while meeting the strength and deformation criteria. This improvement not only enhances waste transportation efficiency, but also lowers production costs and enhances material utilization.

Identification Method of Tire-Road Adhesion Coefficient Based on Tire Physical Model and Strain Signal for Pure Longitudinal Slip

2025-04-01T10:21:08+00:00

To precisely calculate the tire-road adhesion coefficient of rolling tires at various slip rates, and enhance the safety and stability of vehicle operation, an approach for estimating the tire-road adhesion coefficient based on strain sensors and brush models was proposed. First, a finite element model of 205/55R16 radial tire was established, and the effectiveness of the model was verified through static ground contact and radial stiffness experiments. Then, the circumferential strain signal of the inner liner centerline of the tire during braking was extracted, utilizing the average peak angle spacing of the first-order and second-order circumferential strain curves, and the contact area length was estimated using the arc length formula. Subsequently, the braking simulation of rolling tires confirmed the asymmetry of pressure distribution within the ground contact area, estimating the position of slip points within the contact area based on arbitrary pressure distribution function and brush model, while nonlinear regression was utilized to fit the estimation function of slip point under various slip rates. Finally, a functional relationship was developed between tire-road adhesion coefficient and slip rate, considering the friction characteristics between tire rubber and road surface, while the friction model used is based on exponential decay. The results suggest that the methods described above enable estimation of the tire-road adhesion coefficient under different slip rates, providing valuable insights for intelligent tire applications in vehicle dynamics control.

Tooth Contact Analysis of Involute Beveloid Gear Based on Higher-Order Curve Axial Modification

2025-04-09T11:38:37+00:00

This study investigates the tooth flank contact characteristics of a beveloid gear pair through the lens of higher-order curve tooth modification of the involute beveloid gear. The machining coordinate system of the modified gear pair is established, and its tooth surface equations are derived based on the principle of gear meshing and coordinate transformation. In this context, a contact analysis of the modified gear is conducted, examining the impact of varying parameters on the contact trace and contact ellipses, as well as the implications for meshing characteristics in the presence of assembly errors. The findings indicate that the contact form of the high-order curve axial modification of the beveloid gear pair is point contact. Furthermore, the maximum modification magnitude and the order of the modification curve influence the meshing performance of the beveloid gear pair. Additionally, the beveloid gear pair demonstrates enhanced tolerance to the center distance and the axis crossed error, while exhibiting reduced tolerance to the axis intersected error.

Geometric Design Method of Lightweight Line Gear Mechanism

2025-02-12T08:44:19+00:00

Based on the space curve meshing theory, a lightweight line gear mechanism (LLGM) was proposed in this paper. The LLGM can achieve the objective of lightweight design by reducing the radial dimension of the gear, which has an improvement in terms of size reduction. The outstanding advantage of the LLGM is its ability to achieve a high transmission ratio. Three aspects were proposed to design the LLGM: first, the primary design method was obtained; second, an approach to simply and effectively establish the analytical model of the LLGM was presented, which showed that the lightweight characteristic of the LLGM is mainly reflected in the radial dimension; third, the discriminant condition of the LLGM was built. The simplicity and effectiveness of the LLGM were demonstrated by a design example, while gear contact simulation and kinematics experiments were carried out to verify the theoretical basis. The lightweight design method proposed in this paper belonged to structural lightweight design, which can effectively solve the lightweight design issue in gear transmissions characterized by light loads and high transmission ratios.

Simulation Analysis and Experimental Study on Vibration Reduction Performance of Groove-Textured Friction Pair Surfaces

2025-03-10T12:51:12+00:00

To further investigate the influence of surface texture on the vibration characteristics of friction pair surfaces, this study fabricated groove textured on 45# steel surfaces using laser marking technology, forming a friction pair with chloroprene rubber. Numerical analysis of their friction processes under varying speeds was conducted via the finite element analysis software ABAQUS/Explicit (explicit dynamic solver).The results indicate that with increasing speed, the grooved-texture surface enhances its capability to reduce both the intensity and continuity of contact stress concentration on the friction plate surface, while simultaneously accelerating the diffusion speed of contact stress from the leading edge to the trailing edge of the friction block, thereby better suppressing its concentration at the leading edge. Meanwhile, friction tests at varying speeds were conducted on the HCM-5 reciprocating friction and wear testing machine for the 45# steel-chloroprene rubber friction pair. The results show that at all speeds, the system damping of the freely decaying oscillation component on the surface of the groove texture after "groove-crossing fluctuations" is significantly increased compared to the non-textured surface. As the speed increases, the damping effect of the groove texture on the vibration of the friction pair surface gradually enhances, and the reduction in energy density at the main frequency of the friction pair surface becomes increasingly evident. This corresponds to the numerical analysis results, illustrating the influence of speed on the improvement of the vibration characteristics of the friction pair surface by the groove texture.