ID 354

Experimental investigation of multiphysics control of a two-fluid coaxial atomizer

 

Abstract:

We investigate multiphysics control strategies on the atomization of a laminar liquid round jet by a turbulent coaxial gas jet. Spray control (i.e. driving the spatio-temporal distributions of droplets size and number density towards a desired objective) requires a mechanistic understanding of the processes that control droplet formation and transport: primary and secondary instabilities, turbulent transport, forces on the droplets, .etc. We present the experimental characterization of the break-up dynamics in a canonical coaxial atomizer in a series of open loop conditions with harmonic forcing of the gas swirl ratio, liquid injection rate. Both low frequency harmonic modulation of the inputs and high frequency perturbations of the nozzle, in particular at the measured natural frequency of the unperturbed spray, are investigated. Time resolved measurements of the spray structure, as well as the droplet size and velocity are provided. The effect of actuation is characterized for different gas momentum ratios ranging from 5 to 75. This open-loop characterization of the injector will be used to develop reduced order models for feedback control, as well as to validate assumptions underlying an adjoint-based computational control strategy. This work is part of a large-scale project funded by an ONR MURI to provide fundamental understanding of the mechanisms for feedback control of sprays.