Evaluation of a Strut-Plasma Torch Combination as a Supersonic Igniter-Flameholder
As the flight speeds of aircraft are increased above Mach 5, efficient methods of propulsion are needed. Scramjets may be a solution to this problem. Supersonic combustion is one of the main challenges involved in the operation of a Scramjet engine. In general, both an igniter and a flameholder are needed to achieve and maintain supersonic combustion.
The current work examines a plasma torch-strut combination as an igniter-flameholder. The plasma torch-strut combination was tested in the Virginia Tech unheated supersonic wind tunnel at Mach 2.4. Pressure and temperature sampling, filtered photography, and spectroscopic measurements were used to compare different test cases. These results provide both qualitative and quantitative results on how the combination responds to changes in the mass flow rate of fuel and the power to the plasma torch.
The key conclusions of the work were the following:
- Tests showed that an exothermic reaction takes place.
- The amount of heat release increases with an increase in the mass flow rate of fuel.
- The plasma torch-fuel injector interaction caused the heat release to be well above the tunnel floor and sometimes off the strut centerline
- One change in the fuel injector pattern caused more temperature rise near the floor of the tunnel.
- The flow penetration height of the plasma torch alone was reduced by the fuel-plasma torch interaction.
- Moving the strut upstream reduced the measured temperature rise at a fixed downstream location, but increased the penetration height of the plasma torch.
- The computed heat release was found to be small compared to the potential heat release from all the fuel burning.
- The amount of temperature rise caused by the fuel is not greatly affected by the power to the plasma torch.