Session: 33-03 Low Pressure Turbines 1

Paper Number: 103164

103164 - On the Development of High Lift, High Work Low-Pressure Turbines 

Because the low-pressure turbine module accounts for a substantial portion of overall engine weight, increasing the amount of lift achievable per airfoil in the stage is desirable.  Additionally, by increasing the amount of work extracted per stage of turbomachinery, it is possible to reduce the overall weight of the low-pressure turbine.  However, it is well known that the low-pressure turbine is susceptible to a substantial decrease in efficiency as the aircraft on which it is installed climbs to higher altitude.  This phenomenon is denoted as “Reynolds lapse,” and it is associated with separation of the boundary layer from turbine surfaces as atmospheric density decreases with altitude.  So, any drive to increase the lift and work of turbomachinery components in the low-pressure turbine must contend with the possibility that un-reattaching separations can lead to poor performance at cruise.  Here we describe a combined design, numerical, and experimental program intended substantially to increase the lift and work of low-pressure turbine stages.  The effort proceeds through the design of turbine stages consistent with future unmanned air vehicle engine cycles.  This exercise is critically dependent upon the appropriate modeling of boundary-layer transition over airfoil surfaces.  Then, a series of experiments are described that increase in complexity while driving the technology to more realistic embodiments.  Representative experimental data are compared to pre-test predictions of the flow field, and it is shown that acceptable Reynolds lapse behavior is achievable even for turbines with significantly increased lift and work over state-of-the-art systems.  Additionally, it is shown that through the judicious use of appropriate flow control technologies, it is possible to improve further the lapse characteristics of very high-lift airfoils.  Finally, the benefits of applying such high lift, high work low-pressure turbine components are outlined with respect to a notional aircraft system, and future experiments are proposed.

Presenting Author: John P. Clark AFRL

Presenting Author Biography: John Clark is Principal Engineer and Lead for Turbine Research at AFRL.

Authors:

John P. Clark AFRL
Guillermo Paniagua Purdue University
Beni Cukurel Technion