Figure 1
The first two images, obtained at a delay of 1.5 ms after shock reflection, show the difference between injection of H2 fuel at an equivalence ratio of 0.5 into air (Fig. 1) and into nitrogen (Fig. 2). For the case of injection into air, the wake region of the flow is much more pronounced, indicating that combustion takes place within this region.
Figure 2
Figure 3 shows the same flow as that obtained in Figure 1 but at a later time delay of 6.0 ms after shock reflection. The flow appears to be similar to that in Figure 2, indicating that combustion is not occurring at that time within the visible part of the duct.
Figure 3
Figure 4 is a shadowgraph that is less sensitive to density variations in the flow than those obtained in Figures 1, 2 or 3. In this image, the fuel-air equivalence ratio is 1.0. A Mach stem can be seen in this image 2-3 cm downstream of the injector exit, indicating that the oblique shock waves originating from the leading edge of the strut injector interact with the hydrogen jet to cause the flow within the jet to become subsonic, enhancing mixing with the freestream.
Figure 4
In all images, flow is from left to right. The duct is 25 mm high, 50 mm wide and the images are 200 mm long.
Comments? Write Sean O'Byrne (sean@aerodec.anu.edu.au)