Enhancing hydrogen mixing efficiency using extruded nozzles behind struts in supersonic combustion chambers
Seyyed Amirreza Abdollahi, Seyyed Faramarz Ranjbar, M. Barzegar Gerdroodbary, Mir Biuok Ehghaghi
Abstract
This study investigates the fuel mixing dynamics behind a strut in a scramjet engine, focusing on two innovative extruded nozzle configurations: a 3-lobe and a 4-lobe annular nozzle. Using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations, the research examines the effects of nozzle geometry and the inclusion of an internal air jet on circulation strength and fuel mixing efficiency. The results indicate that the unsymmetrical structure of the 3-lobe nozzle enhances circulation strength by approximately 25 % compared to the 4-lobe configuration. However, the mixing efficiency of the 4-lobe nozzle is higher, as its fuel jet forms a narrow strip that interacts more effectively with the supersonic airflow, enabling more efficient fuel-air mixing. The addition of a central air jet significantly improves the mixing process for both configurations, increasing the mixing efficiency by up to 40 %. This enhancement is attributed to the amplified interaction between the supersonic airflow and the fuel jet due to the expanded internal airflow. The impact of the central air jet is most pronounced near the nozzle exit and diminishes further downstream. These findings highlight the trade-offs between circulation strength and mixing efficiency for the two nozzle configurations, emphasizing that the 4-lobe nozzle outperforms the 3-lobe nozzle in terms of fuel mixing, especially at greater distances downstream. The study provides valuable insights into optimizing nozzle design for efficient fuel injection in scramjet engines.