Theoretical study of dynamic characteristic of open-end liquid swirl injector

The purpose of this paper is to summarize important aspects of dynamic characteristic of open swirl injector which is used in liquid rocket engine. Customarily, propellant is injected into vortex chamber through one row of tangential passage which is located at the bottom of vortex chamber in swirl injector. In this paper, we also make an investigation on the dynamic of open swirl injector which has two rows of tangential passage used as filter. Theoretical analysis about the dynamic of open swirl injector has been done, regarding to the influence of axial velocity of liquid in vortex chamber on the mass flow rate pulsation. Moreover, the model of relative effect between tangential passage and vortex chamber has also been modified by taking account of the influence of reflected wave, and the formula for transfer function of the two types of swirl injector has been deduced. The dynamic of "filter" injector, open swirl injector and common swirl injector have been calculated respectively in order to make a comparison of their dynamic characteristic. The result shows that the flux fluctuation of open swirl injector is greatly less than common swirl injector via frequency, moreover, the phase characteristics of open swirl injector is more stable than that of common swirl injector with the increase of frequency. So we can come to the conclusion easily that open injector simultaneously acts as a sensitive element that may modify flow oscillations in addition to its main function of injecting propellant and preparing a combustible mixture. And the open swirl injector with two rows of tangential passage can filter flow oscillation by adjusting the distance between the two rows of tangential passages to half of the oscillation wavelength.