Heat Release Rate Estimation Using Multiple Non-Minimum Phase Sensor Measurements in a One-dimensional Combustor

This paper investigates the feasibility of estimating a thermoacoustic system’s heat release rate oscillations using multiple pressure sensors. The system dynamics are governed by an acoustic partial differential equation (PDE) coupled with flame heat release rate dynamics. Galerkin projection makes it possible to obtain lumped-parameter approximations of this PDE model for different sensor locations. These approximations exhibit non-minimum phase (NMP) zeros when pressure sensors are placed at a safe distance from the flame front, which complicates the problem of online heat release estimation. We address this challenge by choosing multiple acoustic sensor locations at safe distances upstream of the flame. The linear independence of the numerators of the resulting transfer functions makes it possible to construct an aggregate output related to heat release rate oscillation in a minimum-phase manner. This output simplifies the disturbance estimation problem by making plant inversion feasible: simulations show that this approach enables accurate disturbance estimation.