INFLUENCE OF SWIRL ON THE DISCHARGE COEFFICIENTS OF SONIC NOZZLES

Flow characteristics of a swirl generator are studied using an open ci rcuit flow loop, and influence of upstream swirl on the discharge coef ficients of sonic nozzles is investigated using a high pressure gas fl ow standard measurement system. The open circuit flow loop consists of swirl generator, testsection, sonic nozzle, suction fan and LDV syste m. The gas flow measurement system comprises two compressors, storage tank, temperature control loop, sonic nozzle testsection, weighing tan k, gyroscopic scale and data acquisition system. Experiments are perfo rmed at various nozzle throat diameters, inlet pressures and angles of swirl generator. As the angle of swirl generator becomes larger, axia l velocities decrease near the wall and rapidly increase in the pipe c ore, and swirl velocities increase to form swirl flow. Influence of up stream swirl on discharge coefficients becomes greater as the intensit y of swirl increases and as the nozzle throat diameter is enlarged. Va riation trend with Reynolds number, however, is very similar each othe r regardless of swirl intensity.