Performance of multiple, angled nozzles with short mixing stack eductor systems

Abstract

Cold flow tests were conducted on a four-nozzle gas educator system to evaluate the feasibility of reducing mixing stack lengths by the application of angled primary flow nozzles. Three short mixture stacks with length to diameter ratios of 1.73, 1.5, and 1.25 were tested using a set of straight nozzles and a series of angled nozzles having tilt angles of 10, 15, 20 and 22.5 degrees. the nozzles were constructed with an area of primary flow to area of mixing stack ratio of 2.5 Pumping coefficients, mixing stack pressure distributions, flow changes, exit velocity profiles, and back pressures were used to evaluate the various mixing stack length and angled nozzle combinations. A preferred combination was obtained, which, when compared with a longer mixing stack with a length to diameter ratios of 2.5 using straight nozzles, showed equal pumping coefficients and comparable mixing stack pressure distributions while actually improving the mixing. Back pressure increases for the preferred combination of short mixing stack and angled nozzles were slightly greater than for the longer mixing stack with straight nozzles.