Transition Effect on the Flow Dynamics in a Compressor Blade Passage

Abstract

An experimental investigation was carried out to study the effect of the boundary layer transition on the flow dynamics in the blade passage of a compressor cascade. A model of a turbine compressor passage was designed and assembled in a transonic wind tunnel for this purpose. Two different flow control methods were used in the experiment to induce the transition upstream of the shock wave, one concerning the microstep application and the other using distributed roughness strips. Two locations of spanwise microsteps for the transition trigger were chosen, one at the leading edge and the other closer to the shock wave position. The distributed roughness in the form of standard sandpaper strips with different heights was applied in three various locations on the blade upstream of the shock. The main objective of investigations is to present the influence of the laminar and turbulent shock wave-boundary layer interaction on the flow dynamics in a compressor fan passage, and the specific objective is to show how the parameters of particular transition control methods affect the flow dynamics in the investigated channel. The major challenge for this research was to minimize the disturbance caused by the microstep or roughness to the laminar boundary layer, while still ensuring a successful transition. Very interesting results were obtained in the flow control application for the boundary layer transition control, demonstrating a positive effect on the flow unsteadiness in changing the nature of the interaction.

Suitableness of SLM Manufactured Turbine Blade for Aerodynamical Tests

“…This is caused by the size of the layers, as they increase the ‘waviness’, and the roughness is caused by the size of the powder particles that is not influenced by the direction of the layers. The table also proves that the values are in range corresponding to a coarse machining that is in agreement with the physical quality of the blade and available data [ 16 , 17 ]. The general Ra of the model is approximately 7 µm, corresponding to a very coarse machining.…”

“…This problem is even greater as the size of wind tunnels is limited and it is often the case that the blade model for experiments needs to be reduced in size, making it even more challenging. The problem is significant, but the model blades can be produced by using a significant amount of work and a highly skilled craftsmen supported by an extensive machine park, as for it is described by Szwaba et al in [ 17 ]. Such state-of-the-art technology does have a significant impact on the cost and time of preparing the experiment.…”