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Atomization and Sprays, Vol.27, No.8, 741-757, 2017
EFFECT OF GAS SWIRL ON THE PERFORMANCE OF A GAS-CENTERED SWIRL CO-AXIAL INJECTOR
Gas-centered swirl co-axial (GCSC) injectors are important to several propulsion applications. We report an experimental study of the near injector spray structure of a gas-centered swirl co-axial (GCSC) injector, where the effect of introducing swirl into the central gas stream has been investigated. Two different swirl numbers were chosen such that they span the critical swirl number for vortex breakdown of a swirling gas jet. Both co-swirl and counter-swirl conditions were investigated. A non-intrusive method based on feature correlation velocimetry (FCV) was used to quantitatively characterize the velocity of the liquid sheet as a function of gas phase Reynolds number (Re g), swirl number (S) and liquid phase Reynolds number (Rel). It was observed that as Re l increases or as Re g decreases, both spray cone angle and the intact sheet length at the injector exit appear to increase. In addition, swirl in the gas stream appears to cause a reduction in the mean liquid sheet thickness as well as the intact length irrespective of its direction. The effect of gas phase swirl is most pronounced at low Rel. An unsteady analysis of the flapping annular sheet reveals higher fluctuation frequency of the conical liquid sheet with a swirling central gas phase.
Keywords:GCSC injector;near injector spray structure;high-speed imaging;FCV;co-swirl;counter-swirl;dimensionless parameters;instantaneous fluctuations