UNSTEADY-FLOW FIELD DUE TO NOZZLE WAKE INTERACTION WITH THE ROTOR IN AN AXIAL-FLOW TURBINE .2. ROTOR EXIT FLOW-FIELD

The two-dimensional steady and unsteady flow field at midspan in a tur bine rotor has been investigated experimentally using an LDV with an e mphasis on the interaction of the nozzle wake with the rotor flow fiel d. The velocity measurements are decomposed into a time-averaged veloc ity, a periodic velocity component, and an unresolved velocity compone nt. The results in the rotor passage were presented in Part I. The flo w field downstream of the rotor is presented in this paper. The rotor wake profiles and their decay characteristics were analyzed. Correlati ons are presented that match the decay of the various wake properties. The rotor wake velocity defect decays rapidly in the trailing edge re gion, becoming less rapid in the near and far wake regions. The rotor wake semi-wake width increased rapidly in the trailing edge region and then grows more gradually in the near and far wake regions. The decay of the maximum unresolved unsteadiness and maximum unresolved velocit y cross correlations is very rapid in the trailing edge region and thi s trend slows in the far wake region. In the trailing edge region, the maximum periodic velocity correlations are much larger than the maxim um unresolved velocity correlations. But the periodic velocity correla tions decay much faster than the unresolved velocity correlations. The interactions of the nozzle and rotor wakes are also studied. While th e interaction of the nozzle wake with the rotor does not influence the decay rate of the various wake properties, it does change the magnitu de of the properties. These and other results are presented in this pa per.