Effects of Pulsating Flow Conditions on Mixed Flow Turbine Performance

Turbines work under actual pulsating flow conditions due to the operating characteristics of a reciprocating internal combustion engine. The pulsating flow conditions affect the flow fields in a turbine, and lead to obvious difference between actual and steady performance. A three-dimensional numerical investigation into mixed flow turbine under different kinds of pulsating flow conditions was conducted, in order to get an inner sight of the unsteady impact. The effects of the pulsation frequency and amplitude on the turbine performance were analyzed. The results show that the period average performance of the turbine under pulsating conditions is lower than the steady performance under the mean pulsating conditions. The actual power output varies little with the pulsation frequency changing, while the phase lag increases as the pulsation frequency increases. The unsteady characteristics become more obvious when the pulsation amplitude increases. Under the pulsating flow conditions, of which amplitude is 0.8, the period average efficiency is 4.11 percent lower than the steady efficiency. The flow fields fluctuate seriously under this high pulsating flow conditions. The occurrence and vanishing of the votex are dynamic procedures, and hysteresis effect is observed in the unsteady flow.Copyright © 2011 by ASME