A numerical investigation of second throat supersonic exhaust diffuser performance

摘要

An attempt has been made to numerically compute the flow field within Second Throat Supersonic Exhaust Diffusers (STED) to study their performance characteristics in the maintenance of high vacuum conditions by the ejector action during the testing of high altitude rockets. The computational resutls have been compared with the data of cold flow experimetnal studies usign Nitrogen gas ( gamma =1.4) for the sake of validation. Hot flow experimetnal studies have also been subsequently conducted for similar configurations and are compared with the computational studies using a gamma value of 1.2. An optimised second throat ejector diffuser will be an important aid for determining the realisable vacuum specific impulse (I_sp) of a rocket motor with a highor area ratio nozzle (Ae/At=70.0).