OCR Text |
Show EXPERIMENTAL EQUIPMENT In the fuel-staging combustor used in this study and shown in figure 3, fuel and air are premixed and injected into the top of the combustor where they burn in a planar mode in section 1 of the combustor. The combustor is a cylindrical chamber 20.3 cm (8 in.) in internal diameter, 91.4 cm (36 in.) in external diameter and 182.9 cm (72 in.) long. Multiple 4.5-cm (1-3/4 in.) diameter ports, labeled A through Q in figure 3, are provided along the combustor length. At station "a" the remainder of the fuel is injected with additional air and rapidly mixed with the combustion products from section 1. The N0X reduction process occurs In section 2. Finally, air needed to complete combustion is injected at station "b" and is rapidly mixed with the combustion products from section 2. Fuel/air injectors can be placed in ports C, E, F, H, J, L, N and P to vary stage residence times. The combustion processes in the subscale fuel-staging combustor are essentially one dimensional, which is an easily interpretable environment for defining the mechanisms and rates of the fuel-staging process. Since all of the combusted gases must pass through the second flame zone, mixing impacts on the N0X reduction process are avoided in this design. Radial probing tests, before and after injection, have shown that fuel and air are rapidly mixed with the combustion products producing a uniform mixture downstream of the injector. Also, no backmixing of injected reactants into section 1 or 2 is observed. In addition, temperature probing tests along the length of the combustor have shown that the backfiring system reduces heat losses to a level where practical gas temperatures are achieved at the combustor exit. A stainless steel water-cooled and quenched probe is used to extract solid and gaseous samples along the length of the combustor through ports A through Q as well as at the "exhaust" location, sample port 0. In addition, ports A through Q can be fitted with glass viewports for flame observation or they can be used for thermocouple, 8-7 |