Dual bell nozzles represent a possible solution to improve the performance of large liquid rocket engines for launcher first stages. During the low-altitude mode, the flow is separated and the separation line is located near the inflection of the nozzle wall, in a region characterized by a negative value of the wall pressure gradient and where side loads may occur. At high altitude the flow attaches to the nozzle wall and the full area ratio is used. The flow behavior during the transition between the two operating modes is analyzed by time-accurate simulations carried out on a simplified planar geometry and considering two configurations: one with a wall film cooling and the other without film. Aim of this study is to analyze the effect of the secondary gas injection on the dynamics of the separation point, the transition time and the velocity of the separation front.
Film cooling effect on dual-bell nozzle flow transition / E., Martelli; Nasuti, Francesco; Onofri, Marcello. - ELETTRONICO. - (2009), pp. 1-9. (Intervento presentato al convegno 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit tenutosi a Denver, CO nel 2 August 2009 through 5 August 2009).
Film cooling effect on dual-bell nozzle flow transition
NASUTI, Francesco;ONOFRI, Marcello
2009
Abstract
Dual bell nozzles represent a possible solution to improve the performance of large liquid rocket engines for launcher first stages. During the low-altitude mode, the flow is separated and the separation line is located near the inflection of the nozzle wall, in a region characterized by a negative value of the wall pressure gradient and where side loads may occur. At high altitude the flow attaches to the nozzle wall and the full area ratio is used. The flow behavior during the transition between the two operating modes is analyzed by time-accurate simulations carried out on a simplified planar geometry and considering two configurations: one with a wall film cooling and the other without film. Aim of this study is to analyze the effect of the secondary gas injection on the dynamics of the separation point, the transition time and the velocity of the separation front.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.