Upstream Forcing Due to Turbine Rear Structure Vanes on Low Pressure Turbine of an Aero-engine

Other conference contribution, 2026

In axial turbomachines, blade rows are subjected to aerodynamic forcing from both upstream and downstream components, including entropy, vortical, and acoustic disturbances. Assessing the impact of these disturbances on performance and stability is essential. This study focuses on the upstream forcing from outlet guide vanes (OGVs) in turbine rear structure (TRS) of a typical jet engine. The OGVs are designed to de-swirl the flow exiting the low-pressure turbine (LPT) and align the flow axially.

A key concern is the upstream forcing exerted by the OGVs on the LPT rotor. This phenomenon is influenced primarily by two factors: the thickness of the OGVs and their axial distance from the rotor. OGV thickness is driven by structural requirements and its function to accommodate lead-throughs like oil pipes. Thicker vanes generally require larger axial spacing to reduce their aerodynamic impact. However, reducing this distance could enable more compact engine designs, leading to improved fuel efficiency.

A two-step approach to study upstream forcing is used in this work. First, static pressure measurements are conducted at multiple axial locations upstream of the OGV using a turbine test rig. The experimental setup includes different vane types-regular, thick, and mount-vanes to represent realistic engine configurations. This step provides an indication of forcing function from OGVs. Second, transient numerical simulations are performed to evaluate impact of unsteady pressure fluctuations on the LPT rotor.

Results show that pressure disturbances from the OGV propagate upstream and decay with increasing distance from leading edge. The findings indicate that thicker vanes lead to stronger pressure fluctuations, highlighting the importance of vane design and axial positioning in minimizing upstream forcing effects.