Background:
The impulse for the propulsion of a rocket engine is obtained from the combustion
of propellant mixture inside the combustion chamber and as the plume exhausts through a convergent-
divergent nozzle. At stoichiometric ratio, the temperature inside the combustion chamber can
be as high as 3500K. Thus, effective cooling of the thrust chamber becomes an essential criterion while
designing a rocket engine.
Objective:
A new cooling method of thrust chambers was introduced by Chiaverni, which is termed as
Vortex Combustion Cold-Wall Chamber (VCCW). The patent works on cyclone separators and confined
vortex flow mechanism for providing high propellant mixing with improved degree of turbulence
inside the combustion chamber, providing the required notion for studies on VCCW. The flow inside a
VCCW has a complex structure characterised by axial pressure losses, swirl velocities, centrifugal
force, flow reversal and strong turbulence. In order to study the flow phenomenon, both the experimental
and numerical investigations are carried out.
Methods:
In this study, non-reactive flow analysis was conducted with real propellants like gaseous
oxygen and hydrogen. The test was conducted to analyse the influence of mixture ratio and injection
pressure of the propellants on the chamber pressure in a vortex combustion chamber. A vortex combustor
was designed in which the oxidiser injected tangentially at the aft end near the nozzle spiraled up to
the top plate and formed an inner core inside the chamber. The fuel was injected radially from injectors
provided near the top plate and the propellants were mixed in the inner core. This resulted in enhanced
mixing and increased residence time for the fuel. More information on the flow behaviour has been
obtained by numerical analysis in Fluent. The test also investigated the sensitivity of the tangential
injection pressure on the chamber pressure development.
Results:
All the test cases showed an increase in chamber pressure with the mixture ratio and injection
pressure of the propellants. The maximum chamber pressure was found to be 3.8 bar at PC1 and 2.7 bar
at PC2 when oxidiser to fuel ratio was 6.87. There was a reduction in chamber pressure of 1.1 bar and
0.7 bar at PC1 and PC2, respectively, in both the cases when hydrogen was injected. A small variation in
the pressure of the propellant injected tangentially made a pronounced effect on the chamber pressure
and hence vortex combustion chamber was found to be very sensitive to the tangential injection pressure.
Conclusion:
VCCW mechanism has been to be found to be very effective for keeping the chamber
surface within the permissible limit and also reducing the payload of the space vehicle.