Influence of structural parameters of self-excited nozzle on oscillation effect of pulse jet

To design a self-excited oscillation pulse jet (SOPJ) nozzle with excellent performance and improve the rock breaking efficiency of hard rock roadway, the nonlinear mathematical model of SOPJ is firstly established, and the relationship between jet pressure versus time and pressure gradient with different control parameters β of self-excited oscillation system is studied. In addition, the internal and external flow fields with different system pressure p, cavity length Lc, cavity diameter Dc and cone angle αc are studied by numerical simulation to obtain its influence on the oscillation effect of the SOPJ. The results show that the average velocity of SOPJ and continuous jet all shows a power function, but the velocity of SOPJ is lower than that of continuous jet due to the internal energy consumption. The average velocity and variance of the SOPJ are considered as the evaluation criteria for the oscillation effect, the pulse jet presents better oscillation effect with the cavity length, and the cavity diameter and the section cone angle are selected as 80 mm, 30 mm and 160°, respectively, which can provide the basis for the design of self-excited oscillation nozzle and application of pulse jet technology in hard rock roadway driving.