Computational analyses of dynamic rocket ejector flowfields

Numerical analysis of high-frequency jet-switching on dynamic ejector flowfields

“…Slower secondary fluid in the duct from the air inlet is accelerated by the leading edge of the switched jet. Computed results for this configuration have shown that thrust increases of over 30% are possible for thruster cycling frequencies up to 500 Hz and exhaust deflections of 10° [9]. The results also showed that effective acceleration of the secondary air required the jet to impinge on the wall (or plane of symmetry) to trap a pocket of low-speed air.…”

“…The physical phenomenon involved in causing the elevated bypass ratio and specific impulse in low-frequency dynamic ejectors was reported previously [9] and is summarized here. When jet switching occurs, a front forms between the rocket exhaust and the secondary air that has been trapped by the switching action, shown hi Fig.…”

“…The lowfrequency results from Ref. [9] are also included. The specific impulse is calculated as the thrust divided by the product of the acceleration of gravity and the mass flow rate of the rocket, which is constant for all cases.…”

“…Accelerated pockets of air and pressure fronts associated with the jet switching event are a main cause of the thrust increase [9]. The mass flow rate as a function of time for square-wave mode frequencies of 250, 370, and 500 Hz are shown in Fig.…”

“…The purpose of the present work is to use computational techniques to build on previous work [9] to gain a better understanding of the unsteady momentum exchange phenomenon hi the flowfield of the dynamic ejector configuration shown in Fig. 1.…”