| Rocket Based Combined Cycle (RBCC) engines combine the high specific impulses of air breathing engines and the large operation envelop of rockets. Such engines incorporate 4 modes of operation with the first three modes relying on the performance of a mixing duct. The performance improves with a longer mixing duct but the problem with a long mixing duct is that it increases the overall engine weight. Thus, there have been studies done by other research groups to decrease this mixing duct length.;From simulations performed in ANSYS CFX 12.1, it is clear that any abrupt changes to the geometry should be avoided when designing the rocket flow path. Then in the exchange inlet / mixing duct simulations, by varying the mixing duct outlet pressure, it is found that mixing improves since the mass flow rate of air and Mach number decreases. Moreover, a comparison is done with a more conventional design that places a single rocket along the centerline (SRC). It is found that the current design outperforms the SRC configuration in terms of mixing for up to 4 mixing duct diameters downstream.;Research has been ongoing at Carleton University to design a RBCC engine concept that can potentially reduce the mixing duct length by improving mixing. This is done by using a design that expands the rocket exhaust from a singular throat through multiple clovers to a semi-annular profile. The current study focuses on the subsonic free stream flight conditions in order to analyze the rocket air interaction by using this profile. |
