Micro-Particles and Gas Dynamics in an Axi-Symmetric Supersonic Nozzle

A new biolistic gene gun for micromolecular drug delivery to human skin has been developed and numerically tested. The device generates supersonic flow to accelerate the mediated microparticles to sufficient speeds to breach the outer human skin layer. The device is referred to as CDN-WPI and consists of; a high pressure gas tank, a convergent-divergent nozzle (C-D), and a constant area mixing duct. The mediated microparticles are entrained from a parallel inlet after the exit of the C-D nozzle. The gas from the high pressure tank accelerates through the C-D nozzle to supersonic speeds which in turn accelerate the powder microparticles through the constant area mixing duct to high speeds.;A validated numerical procedure is used to study the two-phase flow dynamics inside the biolistic gun using different geometrical configurations. Different driver gas pressures, gas type (helium and air), adding gas swirl, microparticles types and size are considered in this study. The dimensions of the device C-D nozzle, mixing duct length, and the number of particles inlets are the geometrical configurations studied. It is found that using the CDN-WPI device requires reduced driver gas pressure by 50 % compared to the existing devices. The reduction in the gas driver pressure is a result of the elimination of the losses due to boundary layer separation found in all previous devices. The entrainment of the solid microparticles and gas from the parallel inlets precludes flow separation by energizing the boundary layer over the constant area duct walls. As a result, the CDN-WPI is more efficient and safer to use. Further validation is done using semi-empirical particle penetration calculations and the computed flow field which compare very well with the available experimental data.;The axi-symmetric model has been used exclusively in all previous numerical solutions of biolistic guns. To check the validity of this assumption, the axi-symmetric results are compared with the results of 3-D model solutions with continuous particles inlet along periphery. The results compare very well which justify the axi-symmetric assumption. We investigated the 3-D two-phase flow field with one, two, and four particle inlets. The 3-D simulations show that for a practical and efficient gene gun device, more than one particle inlet is required.