Numerical Investigation on Laser Ablation Characteristics of PTFE in Advanced Propulsion Systems

Abstract

The Polytetrafluoroethylene (PTFE or Teflon) based propellants may be used in Pulsed Plasma Thruster, laser ablation thruster and other advanced propulsion systems. Because of the complex behaviors and phenomena of PTFE in ablation process, the study on thrusters’ operation process becomes complicated. Thermal and mechanical events are investigated, including phase transition, thermo-chemical and optical property variations, and multi-pulses laser ablation of PTFE. Considering more details including internal absorption of radiation, reflectivity of material, surface emission, a one-dimensional ablation model is developed and implemented numerically using a non-uniform grid, and implicit finite-volume method to gain greater insight into the process of laser ablation. The model is validated against analytical solutions and is in accordance with previous experimental results. The parameters of optical transmittance, reflectance and absorption coefficients are measured in experiments and are used in the numerical simulation. The laser ablation characteristics of PTFE are investigated, including the effects of wavelength and multipulses. It’s indicated that the laser ablation processes are influenced intensively by changing the laser wavelength and the effects of multiple pulses are also significant. The above numerical simulation provides insight into physical mechanisms of laser ablation, and suggests potential ways of improving thruster’s efficiency