PSI - Issue 71

Abhijit Parate et al. / Procedia Structural Integrity 71 (2025) 256–262

261

Fig. 6. Variation of particle velocity (V p )-to-fluid velocity (U) ratio with acceleration tube length.

3.5 Effect of Stand-Off distance The impact of varying the stand-off distance was examined while maintaining the acceleration tube length of 600 mm, the nozzle area ratio of 0.5 and inlet velocity of 25 m/s. Fig. 7 presents the effect of increase in stand-off distance on particle-to-fluid velocity ratio. It shows that increasing the stand-off distance from 17 mm to 25 mm resulted in a slight increment in particle impact velocity. However, further increasing the stand-off distance leads to a reduction in particle velocity. The initial increase in particle velocity at a shorter stand-off distance may be attributed to the particles remaining within the high fluid velocity core of the fluid stream. Although as the distances increases the fluids kinetic energy available for particle acceleration dissipates, resulting in decline in particle velocity at larger distances.

Fig. 7. Variation of particle velocity (V p )-to-fluid velocity (U) ratio with stand-off distance.

4. Conclusion This study investigates the particle impact characteristics in a JIT for gas-solid flow using CFD based particulate simulations. Effects of different parameters affecting the particle impact characteristics on the target specimen, such as nozzle area ratio, acceleration tube length, stand-off distance and inlet velocity were evaluated and analyzed. It was found that the use of acceleration tube downstream to the nozzle reduces the variation in particle impact velocity with the change in inlet velocity. Further, the increase in nozzle exit area and acceleration tube length increases the particles-to-fluid velocity ratio. Whereas, the increase in stand-off distance beyond 25 mm decreases the particle impact velocity.