Abstract
Experiments were carried on nozzles with different exit geometry to study their impact on supersonic core length. Circular, hexagonal, and square exit geometries were considered for the study. Numerical simulations and schlieren image study were performed. The supersonic core decay was found to be of different length for different exit geometries, though the throat to exit area ratio was kept constant. The impact of nozzle exit geometry is to enhance the mixing of primary flow with ambient air, without requiring tab, wire or secondary method to increase the mixing characteristics. The non-circular mixing is faster comparative to circular geometry, which leads to reduction in supersonic core length. The results depict that shorter the hydraulic diameter, the jet mixing is faster. To avoid the losses in divergent section, the cross section of throat was maintained at same geometry as the exit geometry. Investigation shows that the supersonic core region is dependent on the hydraulic diameter and the diagonal. In addition, it has been observed that number of shock cells remain the same irrespective of exit geometry shape for the given nozzle pressure ratio.
Nomenclature
- A
Area of the nozzle [m2]
- a
Semi-major axis [m]
- b
Semi-minor [m]
- CCD
Charged Coupled Device
- D
Exit diameter of circular nozzle [m]
- Dh
Hydraulic diameter of the nozzle [m]
- D
Diagonal of nozzle exit geometry [m]
- k
Turbulent Kinetic Energy (TKE) [m2s–2]
- Lc
The supersonic core length [m]
- M
Mach number
- P
Pressure [Nm–2]
- Pt
Pressure measured by Pitot tube [Nm–2]
- R
Outer radius of nozzle [m]
- T
Temperature [K]
- u
Velocity component in x direction [ms–1]
- x, y, z
Cartesian coordinate system
Dissipation Rate [m2s–3]
- Superscript and subscript
- *
Throat condition
- 0
Reservoir condition
- a
Atmospheric condition
- e
Exit condition
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