Spray characteristics of high-pressure mist nozzle of lubrication device for space mechanisms

To solve the lubricating failure of spacecrafts in orbit for lack of lubrication, a high-pressure mist nozzle was applied to the spatial lubrication field. A gas-liquid two-phase flow model for direct mist nozzles was established, and the mist flow generating process was simulated using the software of computational fluid dynamic technology CFD-ACE+2009. On this basis, both the lubricant flow velocity and pressure distribution near the nozzle were investigated. By comparison of two high-viscosity fluids, NYE 2001 and Krytox 143AB, with diesel oil in numerical experiments, the effects of fluid physical parameters on pressure propagation and flow velocity variation were analyzed. The simulation results show that the high viscosity of aerospace lubricant NYE 2001 would inhibit the pressure transfer in the mist nozzle severely; for instance, the pressure decreased from 1.5 MPa at the inlet to 0.42 MPa at the end of the 1 mm long nozzle, with a declining rate of 97.2%. Therefore, overhigh viscosity of liquid and overlong nozzle are unfavorable to droplets spray.