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Numerical Analysis of Laser Pulse Frequency and Number of Laser Pulses in Multi-pulsed Laser Propulsion
J.L. Song, Y.J. Hong, M. Wen and Q. Li

A flat-roofed parabolic nozzle is adopted to study the multi-pulse laser propulsion performance. The multi-pulse impulse coupling coefficient decreases when the laser pulse frequency increases in the range of 10 to 400 Hz. Details of the evolution process of the inner and outer flow fields are simulated. The results indicate that the air exhaust and refill processes influence multi-pulse propulsion performance directly. By comparing the initial and multi-pulse flow fields, the air in the nozzle is found to be partially recovered. An uneven low-density distribution and the mass loss result in a decrease in the impulse coupling coefficient, Cm, when the pulse number increases. Moreover, breathing in air to the nozzle for multi-pulse when the focal position is near the exit is beneficial.

Keywords: Laser cutting, steel, reflectivity, real-time measurement, infrared, CO2 laser

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