Effects of Inner Jet Injection on Particle Deposition in the Annular Modified Chemical Vapor Deposition Process Using Concentric Tubes

환상형원관을 사용하는 수정된 화학증착(MCVD)방법에서 내부 제트분사가 입자부착에 미치는 영향

In the annular Modified Chemical Vapor Deposition process using two concentric tubes, the inner tube is heated to maintain high temperature gradients to have high thermophoretic force which can increase particle deposition efficiency. However, higher axial velocity in a narrow gap between inner and outer tubes can result in a longer tapered entry length. In the present paper, a new concept using an annular jet from the inner tube is presented and shown to significantly reduce the tapered entry length with maintaining high efficiency. Effects of a jet injection on heat transfer, fluid flow and particle deposition have been studied. Of particular interests are the effects of jet velocity, jet location and temperature on the deposition efficiency and tapered length . Torch heating effects from both the previous and present passes are included and the effect of surface radiation between inner and outer tubes is also considered.