Design of Nozzles for Supersonic Gas Injector Prototype

Abstract

Supersonic Gas Injection (SGI) is an efficient and economical method than conventional Gas puffing and
complex Pellet injection methods for a small and medium sized tokamaks. To test SGI there is a need to develop a small
scaled prototype where we can study the behaviour of this technique. In this paper SGI prototype is designed for
hydrogen gas flow rate of 2.57E+21 molecules per pulse. This pulse flow, ranges from 2 ms to 6 ms time is analysed in
the vacuum test chamber. Various Convergent-Divergent (CD) supersonic conical nozzles were studied and analysed
with different divergence angles (70
, 120
and 150
) to know the best suitable dimensions of nozzle for different test
conditions and specified flow parameters. The observed flow velocities are in the range of 350 m/s to 2250 m/s and
maximum Mach no. 2.7 can be reached in the test chamber of SGI prototype. The flow properties like Temperature,
Velocity, Pressure, Density and Mach number (M) varies with position and flow time in the test chamber and for that
analysis comparative results are presented in this paper.