Impact of clocking on the aero-thermodynamics of a second stator tested in a one and a half stage HP turbine

Abstract

This paper focuses on the experimental investigation of the time-averaged and time-accurate aero-thermodynamics of a second stator tested in a 1.5 stage high-pressure turbine. The effect of clocking on aerodynamic and heat transfer are investigated. Tests are performed under engine representative conditions in the VKI compression tube CT3. The test program includes four different clocking positions, i.e. relative pitch-wise positions between the first and the second stator. Probes located upstream and downstream of the second stator provide the thermodynamic conditions of the flow field. On the second stator airfoil, measurements are taken around the blade profile at 15, 50 and 85% span with pressure sensors and thin-film gauges. Both time-averaged and time-resolved aspects of the flow field are addressed. Regarding the time-averaged results, clocking effects are mainly observed within the leading edge region of the second stator, the largest effects being observed at 15% span. The surface static pressure distribution is changed locally, hence affecting the overall airfoil performance. For one clocking position, the thermal load of the airfoil is noticeably reduced. Pressure fluctuations are attributed to the passage of the upstream transonic rotor and its associated pressure gradients. The pattern of these fluctuations changes noticeably as a function of clocking. The time-resolved variations of heat flux and static pressure are analyzed togethershowing that the major effect is due to a potential interaction. The time-resolved pressure distribution integrated along the second stator surface yields the unsteady forces on the vane. The magnitude of the unsteady force is very dependent on the clocking position.

On the Aerothermal Flow Field in a Transonic HP Turbine Stage with a Multi-Profile LP Stator Vane

“…As modern engine design philosophy places emphasis on higher blade loading and smaller engine length, the effects of unsteady interactions in a multi-row scenario become of utmost interest for turbine designers. Research focused on the study of the stator-stator clocking effects on both the aerothermal performance of the downstream vane [28][29][30] and the unsteady rotor flow field [31,32]. Additionally, a number of publications addressed the interactions within an aggressive s-shaped inter-turbine diffuser [33,34].…”

“…Less work has been done on the effect of the HP turbine on the downstream components and their mutual interaction. Billiard et al [30] investigated the effect of clocking on one and a half turbine stage. The author reports the positive effect of the vane-vane interaction on the LP stator performance when the first stator wake avenue impinges on the leading edge of the second stator.…”