Dynamical Analysis and Active Control for Flow Instabilities in Boiling Microchannel

Abstract

Received: 1 December 2018 Accepted: 4 March 2019 The purpose of this study is to investigate dynamical behaviors and active control synthesis of mass flowrate in the flow boiling of microchannel, which provides the inspiration to effective pressure drop treatments under parameter variations, exogenous disturbances, and measurement noises. The nonlinear mathematical model has been established through the momentum balance of surge tank and boiling microchannel. The pressure drop oscillations are one of the most severe dynamical instabilities for the boiling two-phase flow microchannel system under various uncertainties and disturbances, certainly leading to thermal and mechanical fatigues and breakage with excessive wear on the microchannel constituents. The boiling microchannel system exhibits complex dynamical behaviors; periodic, quasi-periodic, and chaotic behaviors. Those behaviors are characterized by using phase portrait, bifurcation diagram, and time series analysis. Based on Jacobian linearization around the equilibrium points, the dynamical system can be expressed in the state-space representation with parametric uncertainty. Through this study, it was found that the robust control synthesis can cope with flow oscillations as well as flow instability in an uncertain microchannel system. The extensive simulation results indicate that the proposed control scheme has offered robust performances and stability of the microchannel system under various uncertainties.