| description abstract | The article examines the dynamic characteristics of porous air bearings in the critical pneumatic hammer state (the transition state from the steady state to the pneumatic hammer state). The dynamic characteristics mainly include the critical load (film load capacity) and the critical frequency (vibration frequency) of the bearings. This study presents two fluid domain models: the first model depicts flow channels with annular grooves for air supply (annular grooved model), while the second model does not include annular grooves (nongrooved model). The effects of bearing permeability and air supply pressure are analyzed. Numerical simulation results show that the critical loads and the critical frequencies in the annular grooved model are quite different from those in the nongrooved model. When the permeability is 1.33 × 10−14 m2 and the supply pressures are 400 kPa, 450 kPa, and 500 kPa, the critical loads in the annular groove model are 54.5 N, 48.9 N, and 45.9 N, while the critical loads in the nongrooved model are 42 N, 52.5 N, and 68 N. Reducing the permeability of the air bearing significantly increases the critical load and the critical frequency. Finally, an experimental facility is set up to investigate the critical load and the critical frequency of the air bearings. The critical loads in the experiment are 59.1 N, 52.5 N, and 49.3 N. The fluid domain model's and solution method's accuracy has been confirmed. The simulation results of the annular grooved model are closer to the experimental results. | |
