Session: 05-13 Instrumentation III: Intrusive Measurement

Paper Number: 129145

129145 - Flow Disturbance by Intrusive Instrumentation: Part 1 – Protrusions on the Pressure Side of HP Compressor Vanes 

In our study, we experimentally and numerically quantify the aerodynamic impact of spanwise pressure tube alike protrusions on either the pressure or the suction side of a high-pressure compressor stator vane. In this paper, we focus on the effects of the protrusions located on the pressure side. In part 2 of this study, which is submitted separately to ASME2024, the effects of the suction-sided protrusions are explored.

Our experiments are carried out in a linear cascade wind tunnel at a Mach number of approx. 0.5 and a Reynolds number of 790,000. By varying the dimensions of the protrusions, we confirm the expectation that the generated total pressure losses strongly increase when increasing the height of the tubes. Additionally, we somewhat unexpectedly find that the losses are reduced significantly when increasing the width of the protrusions.

The protrusion’s shape and dimensions are derived from intrusive instrumentation typically found on vanes of compressor rigs such as pressure tubes of static profile pressure taps or Kielhead probes located at the leading edge. Cables of multiple strain gauges glued to the vane surface can have a similar shape. For the application in our linear cascade, the instrumentation is modelled as a generic protrusion geometry. In total, we test eight pressure-sided protrusion configurations. The width of the protrusion varies between 8% and 24% of the chord length, while the height varies between 33% and 66% of the maximum vane thickness. The beginning of all protrusions, which is tangential to the vane surface, is always located at 30% of the streamwise surface length. The protrusions extend over the entire span of the vane. In our linear cascade wind tunnel, one modified vane is installed with four nominal vanes on each side. This setup is similar to the application in an axial compressor rig, where only a few vanes of a stator row are modified.

For the 33% height, three protrusions of 8%, 12% and 24% width are tested. The resulting integral total pressure loss coefficient is increased by a factor of 1.8, 1.4 and 1.2 compared to the loss of a nominal vane. At 66% height, widths of 8%, 12%, 16%, 20% and 24% are investigated, resulting in a loss increase by a factor of 4.7, 3.0, 2.2, 1.9 and 1.9, respectively. These outcomes reveal several interesting trends. At a given width, doubling the height always leads to an increase in the loss. Furthermore, narrower protrusions have a significantly stronger impact on the loss than wider protrusions. With oil flow visualization, we are able to show that this is a result of a reattachment of the flow on top of the protrusion. At 33% height, this reattachment occurs at 12% width, whereas at 66% height, it occurs at 16% width, demonstrating that the height to width ratio of the protrusion determines the reattachment behavior. For the neighboring nominal vanes, no influence by the modified vane on the total pressure loss is found.

In summary, we provide qualitative and – for the given parameters also - quantitative data on the effect of protrusions located on the pressure side of a compressor vane. Depending on the dimensions of the protrusions, the increase in total pressure loss varies significantly. Test engineers can use these results as a guide to design their intrusive instrumentation on compressor vanes to minimize additional total pressure loss. In future work, we will present methods to correct the influence of these protrusions on the overall compressor efficiency.

Presenting Author: Daniel Jung Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University

Presenting Author Biography: Aerospace Engineering M.Sc. from RWTH Aachen University
PhD student at Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University
Research interest: influence of intrusive instrumentation on the flow in a compressor cascade

Authors:

Daniel Jung Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University
Lukas Schäflein Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University
Peter Jeschke Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University
Roland Wunderer MTU Aero Engines AG