BY : RAFAEL, Israel - A Leitner

Development at RAFAEL of an apogee kick motor to launch satellites into orbit created the need for a design of high altitude test facility with a supersonic diffuser, enabling ground level testing of rocket motors at atmospheric conditions while maintaining full flow expansion in the motor divergent section of the nozzle.
Supersonic diffuser performance is sensitive to its configuration.
Experimental work suggests an explanation of the complex phenomena of viscous, turbulent, compressible sub trans and supersonic flow.
PHOENICS has been used to simulate these experiments.
After verification with te experimental tests on a sub-scale model, PHOENICS was applied to assist in the design process of the full-size, supersonic diffuser by up-scaling simulations.

The following assumptions were made:

A two-dimensional axisymmetric model was used.
Steady state.
Single phase flow (the exhaust gases include a condensed phase but the void fraction of the condensed phase is approximately 1%).
The flow is assumed to be fully turbulent and the k-e model was used.
Some computations were carried out without turbulence to study the way in which turbulence modofies this specific flow.

The results showd satisfactory agreement between the measured pressures in the diffuser inlet cone and throat entrance and those predicted by PHOENICS.
This indicates that PHOENICS can be applied to predictions of flow and thermal regimes in these regions.
Scale-up calculations with similar geometry and boundary conditions showed a similar flow field except in the thickness of the boundary layer.

Full details of the PHOENICS simulation and the experimental results may be obtained in:

Flow computation for high altitude test facility

A Leitner

Heat and mass transfer group, RAFAEL, Haifa, Israel

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