Search Results (8)

In this study, a comprehensive regeneration process was employed to enhance the recycling efficiency and performance of waste gear oil. The process began with the waste gear oil subjected to extraction flocculation, which was then followed by vacuum distillation for solvent removal. Then, catalytic hydrogenation was performed, and HiTEC 3339 additive was incorporated at concentrations that ranged from 0.25% to 1.5%, thus resulting in the regenerated gear oil. The tribological properties of the regenerated gear oil were investigated under various load conditions using a friction and wear testing apparatus. When a load of 10 N was applied, the filtered oil (Oil 2) exhibited an average friction coefficient of 0.092 and a volumetric wear rate of 8.25 × 10⁻⁸ mm³/Nm, which represented reductions of 8.23% and 42.7%, respectively, when compared to the unfiltered oil (Oil 1). As the load was increased to 50 N, Oil 2 demonstrated a wear rate of 23.4 × 10⁻⁸ mm³/Nm, indicating a 20.9% improvement in wear resistance. As the concentration of the additive increased, the following trends were observed: (i) Under a load of 10 N, the friction coefficients demonstrated a gradual decreasing trend, while at 50 N, the friction coefficients were remarkably similar and significantly lower than those at 10 N. (ii) The wear rates initially decreased and then increased. Among the tested lubricants, Oil 4 (containing 0.5% HiTEC 3339) exhibited the shallowest wear scar depth under various loads, which indicated superior anti-wear performance. When Oil 4 was thoroughly evaluated through bench tests, it indicated excellent extreme pressure and anti-wear properties, as well as superior rust and corrosion prevention capabilities and high–low temperature performance. The overall performance indicators of Oil 4 were discovered to be similar to those of fresh oil. Full article

Biobased greases are derived from renewable resources, are considered more environmentally friendly, and offer comparable performance to petroleum-based greases. In this study, lubricating greases from frying cooking oils were prepared, thus valorizing waste in order to obtain sustainable and environmentally friendly products. Twelve batches (500 g each) were produced from sunflower and palm frying oils, with 20% by weight calcium/lithium stearate soaps prepared in situ and filled with 15 wt.% cellulose or lignin sulfate. The greases were rheologically characterized. Their consistency was assessed by the penetration test performed before and after working the greases. Dropping point determinations offered information about the stability at higher temperatures, and oil bleeding tests were performed. The average values of the friction coefficient (COF), the contact resistance, and the wear scar diameter were measured through mechanical tests. The greases prove to be comparable to those obtained from mineral oils, with good rheological properties, soft consistency, and good antiwearing behavior, e.g., in open or total-loss lubricating systems, like in open gears and certain food processing machinery; they are thermally stable andprone touse in low-loading working mechanisms. Full article

The main objective of this study was to assess the usefulness of the low-quality brown coal, ash obtained as a result of its combustion, as well as used gear oil for the production of mineral-carbon adsorbents. The adsorbents were characterized in terms of textural parameters, acidic-basic character of the surface, mineral matter contribution to the structure, as well as their suitability for drinking water purification. Adsorption tests were carried out against two synthetic dyes—methylene blue and methyl orange. In order to understand the nature of the organic pollutants adsorption, the effect of the initial dye concentration, temperature, and pH of the system as well as the phase contact time were investigated. The obtained mineral-carbon composite and activated carbons significantly differed not only in terms of the elemental composition and chemical character of the surface (from slightly acidic to strongly alkaline), but also showed a very diverse degree of specific surface development (from 21 to 656 m²/g) and the type of porous structure generated (from micro/mesoporous to typically mesoporous). Adsorption tests showed that the efficiency of organic dye removal from aqueous solutions primarily depends on the type of the adsorbent and adsorbate applied, and, to a lesser extent, on the temperature and pH of the system. In turn, kinetic studies have shown that the sorption of dyes on such materials is consistent with a pseudo-second-order kinetics model, regardless of the type of adsorbed dye. Full article

With the rapid development of China’s manufacturing industry, products are changing toward better energy efficiency and precision. Reducing transmission energy waste, enhancing transmission lubrication, and increasing transmission efficiency have all become critical concerns. The moving particle semi-implicit particle approach is utilized in this study to create a high-speed rotating meshing gear lubrication model and conduct a simulation analysis of transmission gears by studying the influence law of sensitive parameter injection diameter on lubrication. The oil distribution state on the gear surface, the gear tooth surface heat dissipation effect, and the degree of gear operating stability are all calculated by computing the gear surface fluid coverage and convective heat transfer coefficient. According to the numerical simulation results, increasing the liquid injection diameter can greatly enhance fluid coverage and convective heat transfer coefficient on the gear surface, hence improving lubrication. However, when the injection diameter reaches a critical value, the contact area between the liquid and the gear is maximized, and additional increases in the injection diameter will not improve the lubricating effect. Experiments have revealed that the liquid injection diameter is the most critical factor influencing gears. The gear torque dramatically increases as the liquid injection diameter increases. According to a rigorous analysis, the gear lubrication effect is optimal when the liquid injection diameter is 2.0 mm. This provides a theoretical foundation for transmission system lubrication design. Full article

This paper investigates the impact of thermal management methods on the design point and synthesis exchange rates of an ultra-high bypass ratio geared turbofan engine. In a typical thermal management system, where heat is managed by means of heat exchangers that transfer engine waste heat into oil, air, or fuel. However, the utilization of air–oil and fuel–oil heat exchangers has an adverse impact on engine performance. This paper investigates the impact on and engine’s specific fuel consumption and summarizes it into common exchange rates for different thermal management configurations. The results show that any pressure loss in the bypass duct results in a severe specific fuel consumption penalty (an increase of 1% pressure loss in the bypass duct causes a 2% specific fuel consumption increase at cruise conditions). In addition, quite severe is the impact of extracting air from the gas path, particularly when the bleed location is in the bypass duct or the high-pressure compressor. It is also found that the utilization of a fuel–oil heat exchanger improves the specific fuel consumption at a higher rate than an air–oil heat exchanger. For the performance characteristics of the examined engine, the specific fuel consumption benefit with the former is 1.33%, while for the latter it is 0.38%. Full article

Cellular materials have been used in many applications such as insulation, packaging, and protective gear. Expanded polystyrene has been widely used as energy-absorbing liner in helmets due to its excellent cost-benefit relation. This synthetic material can absorb reasonable amounts of energy via permanent deformation. However, in real-world accidents, helmets may be subjected to multi-impact scenarios. Additionally, oil-derived plastic is presently a major source of societal concern regarding pollution and waste. As a sustainable alternative, cork is a natural cellular material with great crashworthiness properties and it has the remarkable capacity to recover after compression, due to its viscoelastic behavior, which is a desired characteristic in multi-impact applications. Therefore, the main goal is to analyze the applicability of agglomerated cork as padding material in safety helmets. First, a finite element model of a motorcycle helmet available on the market was developed to assess its safety performance and to establish a direct comparison between expanded polystyrene and cork agglomerates as liners. Secondly, a new helmet model with a generic geometry was developed to assess the applicability of agglomerated cork as liner for different types of helmets, based on the head injury risk predictions by the finite element head model, YEt Another Head Model (YEAHM), developed by the authors. Several versions of helmet liners were created by varying its thickness and removing sections of material. In other words, this generic helmet was optimized by carrying out a parametric study, and by comparing its performance under double impacts. The results from these tests indicate that agglomerated cork liners are an excellent alternative to the synthetic ones. Thus, agglomerated cork can be employed in protective gear, improving its overall performance and capacity to withstand multi-impacts. Full article

Screw-type expanders offer excellent prospects for energy conversion in lower and medium power ranges, for instance as expansion engines in Rankine cycles with regard to either waste or geothermal heat recovery. With the aim of identifying the potential in organic Rankine cycle (ORC) power systems, an oil-flooded twin-screw expander without timing gears was designed and experimentally investigated in an ORC with R245fa as working fluid. Here, the scope for the experimental determination of the expander characteristic map was limited by the test rig specifications. Based on the experimental results, a multi-chamber model of the test twin-screw expander was calibrated and theoretical approaches according to mechanical and hydraulic loss calculation were applied. Consequently, the expander’s complete characteristic map could be calculated. Furthermore, relevant mechanisms influencing the operational behaviour of oil-flooded twin-screw expanders were identified and analysed in-depth. Full article

This paper presents a case study based on a LCA (Life Cycle Assessment) research program of the silicon foundry sand (SFS) due to the large quantity of produced waste foundry sand (WFS). The foundry waste is a high priority sector within the growing European foundry industry. It is necessary to understand the full life cycle of the foundry waste in order to correctly identify magnitude and types of impacts it has on the environment. System boundary includes the processes: mining, modification, packing, storage and transport to foundry. Inventory analysis data were analyzed and finally converted to the functional unit, which has been defined as one ton of SFS. The resulting environmental impact of SFS production in endpoint is: consumption of natural resources 70.9%, ecosystem quality 18.2% and human health 10.9%. The following portions, with respective percentages, have the greatest overall effect on these results: diesel fuel consumption 32.4% and natural gas consumption 28.7%, electricity usage 17.2%, transport 12.2%, devastation caused by the SFS 5.35% and oil (engine, gear and hydraulic) consumption 4.14%. The highest contributor to the diesel fuel consumption is the SFS exploitation. The overall effect of desiccation was 35.8% and was caused by high consumption of resources and electricity. Full article