A method of active control nonlinear combustion instability

In the influences of noise signal, turbulence and burning in flow field, it is easy for the gas in combustor to form an autonomous oscillating system. This article uses secondary adjustable fuel valves, the centrifugal atomization nozzle with vortex generator as active control executor. Take the first order integral component to approximate the mathematical model of adjustable fuel valves. As the pressure of self-sustained oscillation produced by unstable combustion conforms to the Van der pol oscillation equation, and the relationship between the driving source and vaporizing ratio of the fuel injected by secondary adjustable fuel nozzles is linear, the oscillation equation of pressure in the flow field is obtained. In order to be convenient to deduce the nonlinear feedback linearization control law, change the equation of state of control system into an affine nonlinear mode. The calculation result of the relative order proves the system can be precisely feedback linearized. Through mapping state space from (x₁, x₂, x₃) to (z₁, z₂, z₃), the original nonlinear system is transformed into the completely controllable linear system. Because the active control system of unstable combustion obtained through the feedback linearization is the single input and single output linear system which state variables are phase variables, the sliding mold movement invariable condition is automatically be met. Draw the block diagram of variable-structure control system of the nonlinear feedback linearization so as to determine its inputs and outputs. Output z₁ mean the combustor oscillation pressure. The design of variable structure control law enables the system to arrive the sliding super plane from any original state at the finite time. Once it arrives the sliding super plane, the system state would not be able to leave and to move towards "the zero point" on the plane. Computer simulation results show the variable controller with well tracking accuracy, rapid response, and strong robustness is efficacious in controlling unstable combustion.