OCR Text |
Show 8 For a typical test run, the fuel pressure and exhaust back pressure are set to desired levels. At a minimum, measurements taken included fuel flow, exhaust gas temperature and composition, boost pressure, and fuel pressure. Exhaust-gas composition measurements included CO2, 02> and CO concentrations. In most cases, the peak-to-peak or dynamic pressure in the combustion chamber was also measured. PROCEDURES AND RESULTS After initial observations as described above are recorded, the optical measurements begin. Three types of measurements were performed. These include: (1) High-speed image-intensified movies of the CH emission and flow visualization (2) Raman spectroscopy of CH4, N2» and O2 (3) OH and CH emission intensity. The methodology and results obtained from these experiments are described in the following sections. High-Speed Filming of Combustion Radicals The quartz pulse-combustion system was used for high-speed filming of important combustion radicals. The radical of greatest interest was the CH radical. This species exists only in regions where active combustion is occurring. Consequently, filming the light emitted from this radical enables the combustion process to be followed. More specifically, the presence or absence of CH confirms the location of ignition sites and the presence of a flame front. Photographs of the quartz pulse combustor were accomplished by using an image intensifier (made necessary by the low light intensify of the CH radical) and an optical filter with a narrow band pass. The intensified light is imaged upon a phosphorescent screen and photographed at 1000 frames per second. The images shown in this paper (see Figure 4) are of the mix chamber and the first 9 inches of the combustion chamber. Flow is left to right with reactants entering from the top. The blurring |