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Date of Publication:2022-10-04

Journal:大连理工大学学报

Affiliation of Author(s):能源与动力学院

Volume:51

Issue:4

Page Number:498-504

ISSN No.:1000-8608

Abstract:The impact velocity of particles plays an important role in coating
   formation of cold spray.A proper standoff distance from the nozzle exit
   to the substrate surface can ensure sprayed particles to achieve
   relatively high impact velocities.Numerical simulations were conducted
   by using a CFD software,Fluent,to predict the supersonic flow field
   outside the nozzle.Based on the simulation results,the effect of
   particle conditions on impact velocity is studied and also the way to
   determine the optimal standoff distance is proposed.It is found that
   particles with small size,low density or irregular shape can be
   significantly affected by the dilatational waves,oblique shock waves and
   bow shock waves.With the energy dissipation or passing through the bow
   shock waves,these particles are decelerated sharply.Moreover,there
   exists an optimal standoff distance for different conditions.The
   determination of the optimal standoff distance requires two essential
   considerations:One is that the substrate must be located at the place
   where the carrier-gas velocity is relatively low to weaken the strength
   of the bow shock waves;the other is that particles should be accelerated
   twice by dilatational waves before entering the bow shock waves,which
   means there must be two groups of dilatational waves in front of the bow
   shock waves.

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