Experimental investigation of turbulent flame propagation and pressure oscillation in a constant volume chamber equipped with an orifice plate

In this work, the main contribution is an understanding of different combustion phenomena involving flame acceleration, flame propagation, and the pressure oscillation resulting from flame-shock interactions. These physical phenomena were experimentally studied using a newly developed confined combustion chamber equipped with one or two orifice plates. The results showed that there are five stages of flame propagation when a laminar flame passes through the orifice plate in a confined space. These include the deceleration of the laminar flame, jet flame formation and rapid acceleration, deceleration of the flame, turbulent flame formation and acceleration, and turbulent flame propagation in the end-gas region. Flame acceleration and pressure oscillation were found to be strongly related to the aperture size of the orifice plate. The high amplitudes of pressure oscillations were found to be the results of two combustion mechanisms: the end gas auto-ignition and the interactions between the accelerated turbulent flame and shock wave. To further accelerate the flame and promote stronger disturbance in the end gas, another identical orifice plate was employed. Subsequently, strong flame-shock interaction caused end-gas auto-ignition with an extremely high-amplitude pressure oscillation. Eventually, the maximum amplitude of pressure oscillation exceeded 8 MPa as end-gas auto-ignition occurred in the end region of the combustion chamber.