Development and Testing of an Integrated Liquid-Fuel-Injector/Plasma-Igniter for Scramjets
MetadataShow full item record
Cody Dean Anderson
A newly designed liquid fuel (kerosene) aeroramp injector/plasma igniter was tested in cold flow using the Virginia Tech supersonic wind tunnel at Mach 2.4. The liquid fuel (kerosene) injector is flush wall mounted and consists of a 2 hole aeroramp array of impinging jets that are oriented in a manner to improve mixing and atomization of the liquid jets. The two jets are angled downstream at 40 degrees and have a toe-in angle of 60 degrees. The plasma torch used nitrogen and air as feedstocks and was placed downstream of the injector as an ignition aid. First, schlieren and shadowgraph photographs were taken of the injector flow to study the behavior of the jets, shape of the plume, and penetration of the liquid jet. The liquid fuel aeroramp was found to have better penetration than a single, round jet at 40 degrees. However, the liquid fuel aeroramp does not penetrate as well as an upstream/downstream impinging jet in a plane aligned with the flow. Next, the Sauter mean droplet diameter distribution was measured downstream of the injector. The droplet diameter was found to vary from 21 to 37 microns and the atomization of the injector does not appear to improve beyond 90 effective jet diameters from the liquid fuel aeroramp. These results were then used to decide on an initial location for the plasma torch. The combined liquid injector/plasma torch system was tested in an unheated (300 K) Mach 2.4 flow with a total pressure of 345 kPa. The liquid fuel (kerosene) volumetric flow rate was varied from 0.66 lpm to 1.22 lpm for the combined liquid injector/plasma torch system. During this testing the plasma torch was operated from 1000 to 5000 watts with 25 slpm of nitrogen and air as feedstocks. The interaction between the spray plume and the plasma torch was observed with direct photographs, videos, and photographs through an OH filter. It is difficult to say that any combustion is present from these photographs. Of course, it would be surprising if much combustion did occur under these cold-flow, low-pressure conditions. Differences between the interaction of the spray plume and the plasma torch with nitrogen and air as feedstocks were documented. According to the OH wavelength filtered photographs the liquid fuel flow rate does appear to have an effect on the height and width of the bright plume. As the liquid fuel flow rate increases the bright plume increases in height by 30% and increases in width slightly (2%). While, a decrease in liquid fuel flow rate resulted in an increase in height by 9% and an increase in width by 10%. Thus, as the liquid fuel flow rate varies the width and height of the bright plume appear to always increase. This can be explained by noticing that the shape of the bright plume changes as the liquid fuel flow rate varies and perhaps anode erosion during testing also plays a part in this variation of the bright plume. From the OH wavelength filtered photographs it was also shown that the bright plume appears to decrease in width by 9% and increase in height by 22% when the plasma torch is set at a lower power setting. When air is used as the torch feedstock, instead of nitrogen, the penetration of the bright plume can increase by as much as 19% in width and 17% in height. It was also found that the height and width of the bright plume decreased slightly (2%) as the fuel flow rate increased when using air as the torch feedstock. Testing in a hot-flow facility is planned.
- Masters Theses