The influence of the entrance angle to the bell-shaped tip of a shortened round supersonic nozzle of a rocket engine on its impulse characteristics

Heading: 
Space Energy, Power and Propulsion
1Pryadko, NS, 1Strelnikov, HO, 1Ternova, KV
1Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and State Space Agency of Ukraine, Dnipro, Ukraine
Space Sci. & Technol. 2024, 30 ;(3):53-60
https://doi.org/10.15407/knit2024.03.053
Publication Language: Ukrainian
Abstract: 
In gas-dynamic studies of rocket engines, much attention is paid to the characteristics of the nozzle - its geometry, momentum, losses, and manifestation of traction characteristics under various operating conditions. This work is devoted to the study of the influence of the entry conditions into the bell-shaped tip of a shortened nozzle on its gas-dynamic and impulse characteristics. We consider shortened nozzles with the same conical supersonic parts and the same total length of the nozzle but with different angles of connection of the conical part of the nozzle with the bell-shaped tip.
          When working at sea level, changing the angle of inclination of the forming bell-shaped tip does not significantly change the value of the static pressure at the corner point and the coefficient of nozzle impulse. This is due to the occurrence of flow separation at the corner point and the presence of a large-scale vortex. With a continuous flow in the nozzle during the operation of the rocket engine at altitude, the nature of the pressure distribution on the nozzle wall at the corner point differs when the angle of connection of the conical part with the tip changes, and the maximum value at the nozzle section is approximately the same. This fact is explained by the appearance of a hanging shock wave near the tip wall at small entrance angles (30°).
           The study examines the flow's impulse characteristics in the nozzle under different pressure values at the inlet and the surrounding environment. The impulse coefficient in terrestrial conditions depends little on changing the tip and decreases with increasing pressure at the nozzle inlet. When working at height, there is a weak effect of changing the angle of entry into the nozzles on the momentum coefficient.
Keywords: bell-shaped tip, corner point, flow disturbance, impulse characteristics, shortened nozzle
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