A Supersonic Jet facility has been established at LHSR to study the fluid dynamic phenomena of mixing layers which helps in improving the devices such
as aero-engines, injection of fuel into combustor, supersonic ejector, RAMJET/SCRAMJET and noise reduction in aero-engines. It consists of two compressed air tanks of 3 cubic meter capacity and one compressed air tank of 2
cubic meter capacity at 12 bar pressure. The tanks are filled by an Elgi E22-13
GS screw compressor system delivering compressed dry air at 12 bars, 95 CFM.
The flow from the tanks is regulated by a pressure regulator-solenoid valve assembly that allows control over the flow rates and stagnation pressures delivered to the downstream. The facility has flexibility to conduct various experi
mental configurations involving supersonic flows in general and jets in particular. Currently experiments are being conducted in supersonic ejectors and
wall jets. A supersonic ejector uses a primary motive fluid expanding from high
pressure to entrain a secondary flow into a mixing duct where by augmentation
of momentum and energy and the secondary flow is pumped to higher pressures. A purely aerodynamic device, it finds numerous applications in vacuum
generation, thrust augmentation, alternate refrigeration, gas dynamic lasers,
wind tunnels, and noise suppression from jets, RAM/SCRAMJET, recirculation
in fuel cells. A two dimensional ejector with a primary nozzle of Mach number
2.5 and a mixing duct of 20mm has been established. Studies are being conducted to understand the mixing phenomena of co-flowing supersonic jet
within confined ducts using optical tools like Schlieren, LASER scattering, pressure measurements. The facility can be interchangeably used with an axi-symmetric configuration which allows for use of different secondary fluids, nozzle
geometries and a range of mass flow ratios. The photograph of the facility is
shown above.
The jet facility has been modified to study a supersonic wall/free jet, which
within the same flow topology has interactions of shock with boundary layer
and mixing layer. This flow scenario is found in various aerospace applications,
especially in futuristic SCRAMJET applications. The flow features and its response to local thermal and momentum bumps have been investigated with
Schlieren, pressure measurements, and oil-flow visualizations. The photograph
The blow-down facility can also be operated in the supersonic free jet mode.
Photograph of the supersonic free jet facility is shown above. Supersonic jet
coming out of exotic nozzle shapes are studied in this facility for accessing the
mixing enhancement capabilities which are important in reducing the thermal
and acoustic signature in supersonic jet exhaust.
of the facility is shown below.