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Ultra-high molecular weight polyethylene (UHMWPE) powder was modified by surface treatment technology, then its wettability, dispersibility, mechanical, and tribological properties in polyurethane elastomer were studied. The testing results showed that after surface treatment, UHMWPE powder could infiltrate and disperse evenly in polyurethane, and build micro cross-link with the contact surface of polymer substrate, which is conducive to enhancing the internal stress of polymer and improving the mechanical properties. With a small amount of modified UHMWPE being added into the casting polyurethane (CPU) elastomer, the right-angled tearing strength increases and the abrasion loss decreases. Moreover, the elastomer surface self-lubricating performance of CPU compounding with modified UHMWPE is enhanced: compared with the neat CPU sample, the average friction coefficient of the CPU samples with 5%, 10%, and 15% of modified UHMWPE is reduced by 46.3%, 41.5%, and 39.0%, respectively, and the surface wear resistance is improved; under the high-load working condition, the CPU elastomer with 5% of modified UHMWPE has the optimal tribological performance. KEYWORDS mechanical properties, polyethylene, polyurethane elastomers, self-lubrication, surfaces, tribology, 1 | INTRODUCTION Due to the advantages in mechanical properties, compression resistance, wear and tear resistance, solvent and aging resistance, the materials of polyurethane, epoxy resin, and synthetic rubber have [...]

The substantial demand for enhanced combustion efficiency and achieving near-zero emissions in GDI engines has spurred the introduction of a novel approach employing elliptical divergent nozzle spray technology. This innovative method, which marries the elliptical shape with a divergent nozzle, not only elevates downstream atomization quality but also mitigates nozzle tip wetting. Nevertheless, there exists a dearth of documented research regarding the internal flow and outflow characteristics related to the atomization potential of elliptical divergent nozzles. Numerical investigations have been carried out to scrutinize alterations in the three-dimensional cavitation morphology, the dispersion of turbulent vortex structures, and the nozzle exit flow parameters across a range of cavitation number conditions for both circular and elliptical divergent nozzles. The research findings demonstrate that the cavitation intensity of the elliptical divergent nozzle consistently surpasses that of the circular divergent nozzle. Also, the elliptical divergent nozzle consistently exhibits a greater number of turbulent vortex structures compared to the circular divergent nozzle across all cavitation number conditions. Additionally, as the cavitation number decreases, the difference in turbulence vorticity magnitude between the exits of the circular and elliptical divergent nozzles gradually increases. Furthermore, the elliptical diverging orifices are more susceptible to cavitation compared to their circular counterparts. The elliptical divergent nozzle outperforms the circular nozzle with a substantial 24.6% increase in exit velocity, especially at a cavitation number of 1.016. [ABSTRACT FROM AUTHOR]

A shell-and-tube Methanol Steam Reformer (MSR) system was designed for diesel engines. The effects of structural and operational parameters of the spiral baffles in the methanol reformer on heat transfer and hydrogen production performance were investigated. Additionally, a multi-objective optimization using response surface methodology was conducted to study the interactive effects of spacing and thickness, as well as liquid hourly space velocity and steam–methanol ratio, on the methanol conversion rate, hydrogen concentration and hydrogen production. The results indicated that reducing the baffle spacing and increasing the baffle thickness further improved heat transfer efficiency. Optimal conditions were achieved at a spacing of 30 mm and a thickness of 2 mm, resulting in a methanol conversion rate of 64.2 %. Increasing the steam–methanol ratio from 0.5 to 2 increased the methanol conversion rate from 50.6 % to 79.7 %, with a subsequent decrease in hydrogen concentration. Increasing the liquid hourly space velocity from 635 h−1 to 1905 h−1 significantly reduced the methanol conversion rate from 94.5 % to 64.2 %, but the hydrogen production increased from 0.111 mol/s to 0.228 mol/s. Optimization results indicate that the liquid hourly space velocity and steam–methanol ratio have a greater influence on the hydrogen production efficiency of the methanol reformer. [ABSTRACT FROM AUTHOR]

The elliptical nozzle has the potential ability to increase the air-fuel mixture quality. A one-way coupled spray model and Homogenous Relaxation Model (HRM) was adopted to investigate the spray behaviors and the air-fuel mixture progress in real diesel combustion chamber with the application of elliptical and circular diesel nozzle. The results indicated that the spray cone angle and the air entrainment mass of elliptical nozzle were larger than that of the circular nozzle, while the spray penetration of the elliptical nozzle which the aspect ratio is 1.5 and 2 was shortened by 11% and 8.3% as compared to circular spray respectively. Also, the air entrainment mass of the elliptical spray with a ratio of 1.5 and 2 increased by 60% and 35% as compared with circular spray respectively. Furthermore, the partial equivalent ratio and the high concentration area in the cylinder is reduced for elliptical nozzle, and the air-fuel mixture is more uniform. The fuel evaporation rate of elliptical spray is always higher than that of the circular spray. [ABSTRACT FROM AUTHOR]