• POD
• Experiments
• PIV
• Turbomachinery
• LPT
• TRS
• OGV

The flow field characteristics of a TRS (turbine rear structure) have been experimentally
investigated using the non-intrusive PIV (particle image velocimetry)
technique. The TRS is the structure located downstream of the LPT (low-pressure
turbine) in a jet engine. The flow features through this structure are extremely
complex since non-uniformities generated at the LPT interact with the OGVs (outlet
guide vanes) located inside this structure.
The experiments were conducted at the Chalmers Fluid Mechanics department
wind tunnel, which consists in a closed loop facility where an LPT is located upstream
of the test section to provide engine-realistic inlet boundary conditions to
the TRS.
In particular, the measurements involved the three following regions of the flow:
the outlet of the TRS (2D and stereo PIV), Plane B (stereo PIV) and the boundary
layer around the single OGV of the TRS (2D PIV).
Moreover, the experiments were conducted varying the value of two coefficients.
The first one is the Reynolds number based on the channel height. Two values
were tested corresponding to the low and high speed respectively: Re = 235000
and Re = 465000.
The second one is the flow coefficient that is defined as the ratio between the axial
velocity of the flow and the rotational speed of the turbine. Four different values
of this coefficient were tested in the whole experimental campaign: 0.588, 0.622,
0.657 and 0.775.
Several quantities of interest were calculated from the data recorded through the
software Dynamic Studio 2016-a, such as the instantaneous velocity and vorticity
fields but also the main statistics (mean velocity field, standard deviations of velocity
components etc.).
Afterwards, a POD (Proper Orthogonal Decomposition) analysis was applied to
the data to investigate the presence of relevant modes.
Finally, an FFT transform analysis was conducted to make a comparison with the
POD results.
To conclude, the quality of the results can be deemed satisfactory, considering
that new measurements will be taken in the near future. However, the presence
of technical issues such as multiple reflections coming from the internal structure
of the TRS or low images recording sampling frequency led to an only partial
comprehension of the complex phenomena happening inside the TRS.