Strojniški vestnik - Journal of Mechanical Engineering

Cam Ring Curve Optimization for Radial Hydraulic Motor Based on Seagull Algorithm

Tue, 09 Sep 2025 00:00:00 +0000

With the accelerated adjustment of the global energy structure, the intensity of strategic mineral resource development continues to rise. The growing demand for construction machinery and equipment has led to increased use of radial piston hydraulic motors, known for their low-speed and high-torque characteristics, in heavy-duty mining machinery and equipment. To address the issues of significant contact stress, noticeable output pulsation, and considerable flexible shock in the stator curve design of a radial piston hydraulic motor, this paper proposes a multi-step composite curve optimization design method based on the Seagull Optimization Algorithm (SOA). This method integrates the concepts of “stepped” and “trapezoidal” acceleration curve design, utilizing the SOA algorithm to tackle these challenges. The SOA algorithm is more adaptive than the genetic algorithm (GA) and the particle swarm optimization (PSO) algorithm, maintaining population diversity even in the later stages of iteration. This effectively overcomes the limitations of PSO and GA in multi-peak problems. By establishing a stator curve optimization model aimed at minimizing contact stress through theoretical modeling and dynamics analysis, and combining the global search and local development capabilities of SOA, we achieve multi-constraint optimization on key parameters such as the amplitude-angle ratio in the acceleration zone and the amplitude-angle in the zero-speed zone. This results in a composite stator curve with no shock, low pulsation, and low stress. The effectiveness of this method was validated through bench tests, which showed that the maximum contact stress of the optimized multistep composite curve is reduced by 5.4% and 18.3% compared to the conventional equal acceleration curve and trapezoidal curve, respectively. Additionally, the speed pulsation rate decreases by 10.81% and 25.73% under 20 MPa and 30 MPa conditions, respectively, with no sudden change in reaction force and a reduction in pulsation shock during operation.

Comprehensive Performance Evaluation of Sliding-bearing Wind Turbine Gearboxes

Yao Li, Longsheng Li, Gaoxiang Ni, Xinlong Li, Jianjun Tan, Kongde He — Tue, 09 Sep 2025 00:00:00 +0000

Considering the structural characteristics and multi-source excitations of sliding-bearing wind turbine gearboxes, this study constructs a multi-body dynamic model of high-power sliding-bearing wind turbine gearboxes. A comprehensive performance evaluation methodology is proposed, integrating the analytic network process (ANP) with an improved fuzzy comprehensive evaluation (IFCE). A multidimensional comprehensive performance evaluation framework, emphasizing the practicality and cost-effectiveness is developed consisting of target, criterion, and indicator layers. The key evaluation indicators identified within this framework include the main shaft bearing support force, transmission system reliability, load-sharing coefficient, vibration characteristics, and power density. Utilizing ANP and IFCE methodologies the comprehensive performance of two sliding-bearing wind turbine gearboxes is systematically assessed.

Thermodynamic Evaluation and Working Fluid Selection for a Heat Pump Integrated into a Hydropower Plant HVAC System: A Case Study from Serbia

Nedžad Rudonja, Ivan Zlatanovi´c, Miloš Banjac, Milan Gojak, Ružica Todorović — Tue, 09 Sep 2025 00:00:00 +0000

This paper presents a thermodynamic analysis of two types of heat pumps integrated into the heating, ventilation, and air conditioning (HVAC) system of the “Bajina Bašta” hydropower plant located in Serbia. The study aims to replace existing electric boilers with more energy-efficient solutions by utilising renewable heat sources. A comparative evaluation of water source heat pump (WSHP) and air source heat pump (ASHP) configurations was conducted using a custom-developed MATLAB model based on CoolProp data of working fluids. The analysis was supported by real data obtained through in situ measurements of air and water temperatures at the selected location, ensuring accurate input parameters for the simulations. Five refrigerants (R-410A, R-407C, R-134a, R-32, and R-1270) were used, and R-32 was selected as the optimal working fluid because of its high efficiency, moderate flammability, and low environmental impact. The lowest coefficient of performance (COP) for the WSHP was 3.27 in January, while the seasonal coefficient of performance (SCOP) reached 3.36, approximately 15.5 % higher than the ASHP counterpart (SCOP = 2.91). The study confirms that, upon analyzing the entire heating period, WSHP systems are technically and environmentally superior to ASHPs in the locations studied. The proposed configuration, based on real measured data and obtained results, can significantly improve energy efficiency and reduce internal electricity consumption in hydropower plants, thereby supporting the decarbonisation of large-scale renewable energy facilities. While most previous studies have focused on improving energy efficiency in buildings, this work demonstrates the substantial yet underexplored potential for efficiency improvements in the electricity production sector in Serbia. The study specifically examines hydropower plants in Serbia, where heating and air conditioning systems built in the 1960s remain highly energy inefficient. By quantifying the benefits of integrating WSHP and ASHP systems, the research highlights a pathway toward significantly enhancing the energy efficiency of hydropower infrastructures.

Differential Tooth Surface Modification Method for Reducing Vibration in Spiral Bevel and Hypoid Gears

Yu Zhang, Chenyu Duan, Xiao Li, Zhiyong Wang, Yanli Ma, Guoqi He — Tue, 09 Sep 2025 00:00:00 +0000

To address the issue of increased gear noise in electric vehicle drivetrains due to higher rotational speeds, a differential tooth surface modification method for spiral bevel and hypoid gears is proposed. A mathematical model for spiral bevel and hypoid gears is established using the vector method. Based on this model, a finite element dynamic model of the gears is developed through secondary development using Adams software. A tooth surface modification approach involving parameters (bias factor and profile separation factor) varying according to a sinusoidal function is investigated, alongside its impact on micro-topography of the tooth surface. A comparative simulation analysis is performed to evaluate the sinusoidal parameter design method against traditional modification methods, emphasizing gear angular acceleration and meshing force under various operating conditions. The results demonstrate that the differential modification method achieves a significant reduction in the first three orders of meshing frequencies under almost all conditions, with maximum reductions in the first-order frequency amplitudes of the gear angular acceleration and meshing force reaching 22.98 % and 36.05 %, respectively. This confirms the method effectiveness in reducing gear vibration and noise. The proposed differential modification method for spiral bevel and hypoid gears offers a novel approach for vibration and noise mitigation, offering valuable technical support for designing and manufacturing of high-performance electric vehicles.

Evaluation of Surface Functional Properties of Polymeric Sliding Materials for Lubricated Metal-Polymer Pairs Applications

Tue, 09 Sep 2025 00:00:00 +0000

This work presents a comparative study of the surface mechanical properties and tribological wear resistance of polymeric sliding materials. The authors focused on the application of polymeric materials in producing spare parts for vehicles that are still in use but for which original components are no longer manufactured or are disproportionately expensive compared to the vehicle’s market value. The subject of the study was frictional interactions between the timing chain and the sliding element. Three commercial materials were tested, designated: PA6G, PA6G+MoS2, PE 1000. A commercial lubricant PMO 5W40 Extreme 100 % (intended for vehicles without a particulate filters) was used. The coefficient of friction and wear were analyzed under dry friction and oil bath. The lowest coefficient of dry friction was obtained for the PA6 G, whereas PE 1000 exhibits the highest. Under oil lubrication, however, PE 1000 demonstrated the lowest coefficient of friction. Microscopic analysis of wear scars was performed. The extent of wear depends on the type of material used and the nature of the interaction (dry friction, oil-bath friction). Wear under dry friction was lower than under oil-bath conditions, possibly due to the influence of the Rebinder effect.