Theoretical and experimental study of the dynamics of a liquid swirl injector

The purpose of this paper is to summarize important aspects of the dynamic characteristic of an open-end swirl injector used in a liquid rocket engine. Theoretical analysis about the dynamic characteristics of open-end swirl injectors has been performed, considering the influence of the axial velocity of liquid in the vortex chamber on the volume flux pulsation. Moreover, the model of interaction between the tangential channel and the vortex chamber has also been modified by taking into account the influence of reflected waves; the formula for the transfer functions of the open-end swirl injectors has been deduced. The dynamics of the open-end swirl injector have been calculated. To investigate the dynamic characteristics of the swirl injector experimentally, aninner flow-pulsation measurement method has been developed according to the characteristics of the liquid flow in the swirl injector. The principle of measuring the instantaneous volumeflow using conductance methodisdiscussed. The sensoris composedofalock-in amplifying circuit and an electronic probe, fabricated from porous titanium material; an experimental measurement of the open-end swirl injector is conducted using this sensor. The experimental result shows that both the method and the sensor can meet the requirement for a flow-pulsation measurement in the swirl injector. This is of considerable significance in the experimental investigation of the swirl injector dynamic characteristics and liquid rocket engine unstable combustion.