TIME-ACCURATE EULER SIMULATION OF INTERACTION OF NOZZLE WAKE AND SECONDARY FLOW WITH ROTOR BLADE IN AN AXIAL TURBINE STAGE USING NONREFLECTING BOUNDARY-CONDITIONS
S. Fan et B. Lakshminarayana, TIME-ACCURATE EULER SIMULATION OF INTERACTION OF NOZZLE WAKE AND SECONDARY FLOW WITH ROTOR BLADE IN AN AXIAL TURBINE STAGE USING NONREFLECTING BOUNDARY-CONDITIONS, Journal of turbomachinery, 118(4), 1996, pp. 663-678
The objective of this paper is to investigate the three-dimensional un
steady flow interactions in a turbomachine stage. A three-dimensional
time-accurate Euler code has been developed using an explicit four-sta
ge Runge-Kutta scheme. Three-dimensional unsteady nonreflecting bounda
ry conditions are formulated at the inlet and the outlet of the comput
ational domain to remove the spurious numerical reflections. The three
-dimensional code is first validated for two-dimensional and three-dim
ensional cascades with harmonic vortical inlet distortions. The effect
iveness of the nonreflecting boundary conditions is demonstrated. The
unsteady Euler solver is then used to simulate the propagation of nozz
le wake and secondary flow through the rotor and the resulting unstead
y pressure field in an axial turbine stage. The three-dimensional and
time-dependent propagation of of nozzle wakes in the rotor blade row a
nd the effects of nozzle secondary flow on the rotor unsteady surface
pressure and passage flow field are studied. It was found that the uns
teady flow field in the rotor is highly three dimensional and the nozz
le secondary flow has significant contribution to the unsteady pressur
e on the blade surfaces. Even though the steady flow at the midspan is
nearly two dimensional, the unsteady flow is three dimensional and th
e unsteady pressure distribution cannot be predicted by a two-dimensio
nal analysis.