No abstract

No abstract

No abstract

Abstract. Abrasive flow machining (AFM) is an effective method that uses the flow of a pressurized abrasive media for removing workpiece material. It is used to deburring, polishing or radiusing, etc. In this paper, the effect that AFM process on the surface of the helical gear is investigated. Then, the distribution of the velocities, shear rates and shear forces of the abrasive flow on the helical gear surface is obtained by CFD module of the COMSOL Multiphysics software. The simulation results show that the abrasive grains near the addendum, tooth surface and tooth root can be subjected to corresponding shear stress. Experimental results indicated that the surface roughness Ra of the left tooth surface, right tooth surface and addendum before processing 1.429um, 1.108um and 2.732um dropped after processing 0.228um, 0.216um and 1.754um. All burrs at the intersection between tooth surface and end surface has been cleared, the surface quality of the helical gear has been improved. Therefore, AFM method can improve the surface quality of the helical gear effectively.

Two-dimensional numerical simulations with Eulerian-Lagrangian method are conducted to study propagation and extinction of stoichiometric hydrogen/air detonations in fine water sprays. Parameterized by water mass loading and initial droplet size, a detonation extinction map is developed. Detonation extinction would occur with larger mass loading and/or smaller droplet size. General features of gas phase and water droplets and local detonation frontal structures are well captured. Numerical soot foils are used to characterize the influence of mass loading and droplet size on the detonation wave. The results also show that the detonation cell size increases with increased mass loading or decreased droplet size. Analysis on unsteady detonation extinction process is performed with the evolutions of detonation frontal structure, spatial distribution of thermochemical variables and interphase transfer rates (mass, energy, and momentum). Moreover, the chemical explosive mode analysis reveals that for stable detonation, thermal runaway dominates behind the Mach stem, while chemical propensities of auto-ignition and thermal runaway appear alternately behind the incident wave. When the induction zone length increases as the reaction front (RF) and shock front (SF) are decoupled, localized burned pockets surrounded by the autoignition chemical explosive mode can be observed. In addition, the interactions between detonation wave and water droplets demonstrate that the energy and momentum transfer have more direct interaction with SF and RF than the mass transfer. The interphase transfer rates increase with the water mass loading. Under the same mass loading, the smaller the droplet size, the larger the interphase transfer rates. However, the size of fine water droplets has a limited influence on the interphase momentum exchange. Moreover, high energy and mass transfer rates are observed at the onset of detonation extinction, and they gradually decrease when the reaction and detonation fronts are decoupled.