OCR Text |
Show of larger particles appears. Very large droplets can be seen in the recirculation zone behind the injector. Figure 9 is a series of photos using the small injector at the same conditions as above. Again, very good atomization is seen initially, with very little atomization occurring after 5 ms. Uith this injector it should be noted that the large droplets are seen below the stream of pulsing flow from the tailpipe. Similar results were obtained for the small injector with a flow of 3 g/s. Figure 10 shows the 2 g/s water flow in the presence of steady cold air flow through the pulse combustor. It shows that no atomization occurs due to just the cold air flow. 4. DISCUSSION The photographic studies offer valuable insight into the mechanisms allowing the intermittent production of large slurry drops. Uhile similar atomization and combustion were obtained with both injectors in the combustion tests, with approximately the same number of large drops exiting the system, from the photos it is clear that different mechanisms produce these drops. For the small injector diameter the momentum of the fluid jet carries it through the atomizing stream, while for the large jet the large droplets are produced in the wake of the injector. Thus, the seeming insensitivity to injection method seen in the combustion tests is really a result of completely different processes. These observations indicate a need to test small diameter injectors with flow parallel to, rather than perpendicular to, the atomizing stream. This should eliminate the problem of injecting completely |