A novel isolation curtain to reduce turbine ingress heating and an advanced model for honeycomb labyrinth seals
A combination of 3-D and 2-D computational fluid dynamics (CFD) modeling
as well as experimental testing of the labyrinth seal with hexagonal honeycomb cells on
the stator wall was performed. For the 3-D and 2-D CFD models, the hexagonal
honeycomb structure was modeled using the concept of the baffle (zero-thickness wall)
and the simplified 2-D fin, respectively. The 3-D model showed that even a small axial
change of the tooth (or honeycomb wall) location, or a small circumferential change of
the honeycomb wall location significantly affected the flow patterns and leakage
characteristics especially for small tooth tip clearance. Also, the local details of the flow
field were investigated.
The seven basic procedural steps to develop a 2-D axisymmetric honeycomb
labyrinth seal leakage model were shown. Clearly demonstrated for varying test
conditions was the 2-D model capability to predict the 3-D honeycomb labyrinth flow
that had been measured at different operating conditions from that used in developing the
2-D model. Specifically, the 2-D model showed very close agreement with measurements. In addition, the 2-D model greatly reduced the computer resource
requirement needed to obtain a solution of the 3-D honeycomb labyrinth seal leakage.
The novel and advanced strategy to reduce the turbine ingress heating, and thus
the coolant requirement, by injecting a Â?coolant isolation curtainÂ? was developed
numerically using a 3-D CFD model. The coolant isolation curtain was applied under the
nozzle guide vane platform for the forward cavity of a turbine stage. Specifically, the
isolation curtain serves to isolate the hot mainstream gas from the turbine outer region.
The effect of the geometry change, the outer cavity axial gap clearance, the
circumferential location of the injection curtain slot and the injection fluid angle on the
ingress heating was investigated. Adding the chamfer to the baseline design gave a
similar or higher maximum temperature T*
max than did the baseline design without
chamfer, but implementation of the injection curtain slot reduced substantially T*
the outer region. In addition, a more desirable uniform adiabatic wall temperature
distribution along the outer rotor and stator surfaces was observed due to the presence of
the isolation curtain.
Advisor:Rhode, David L.; Anand, Nagamangala K.; Beskok, Ali; Hassan, Yassin A.
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:labyrinth seal turbine ingress heating
Date of Publication:05/01/2005