Experimental Investigations of the Aerodynamics of Highly Loaded Tandem Vanes in a High-Speed Stator Cascade

Abstract

Tandem blade configurations are said to being able to outperform conventional single blades in terms of loss behaviour and flow turning. The work presented here is supported by experimental investigations which were conducted at a 2D linear stator cascade at the Chair for Aero Engines at the Technische Universität Berlin. Two different tandem blade configurations with a different load split are examined and compared against a conventional single reference blade. Multi-coloured oil flow visualisation complemented by wake flow measurements show the development of the secondary flow structures and enable a thorough understanding of the impact of varying tangential displacement for tandem blades. The results show that tandem blades can reduce the total pressure losses, especially in the midspan region, which also results in smaller overall values. In addition, the incidence angle variation has shown that the working range of the tandem vanes exceeds the originally designed working range of the single reference blade. The tandem configurations still allow flow guidance at stall condition and prove the capability of the concept.

Recent Insights into the Flow Topology Around Highly Loaded Tandem Vanes

“…The LS D F tandem design overally achieves higher values than the LS DH design and can even absorb some of the rapid decrease. As previously shown by Sanger [21] and also Heinrich et al [14,15] the positioning of the front and the aft blade and in particular the percent pitch variation has a strong influence on the flow topology. Previous work has analysed the flow topology with the aid of oil flow visualisation and shown in particular the influence of the gap flow on the secondary flow development on the aft blade.…”

“…The pressure distribution and the location of the transition and the separation bubble does not change. Heinrich et al previously could acknowledge that the front blade absorbs the incidence changes [14,15]. In addition to the off-design examinations they demonstrated that if the pitchwise gap is chosen too large, the front and aft blade perform as two single blades.…”

Experimental Investigation of a Transonic Compressor with Variable Stator Vanes in Tandem Arrangement

“…They proved a good performance for the tandem stator at varying flow conditions. Heinrich et al (2015), Tiedemann et al (2017), Heinrich et al (2017) as well as Heinrich and Peitsch (2019) investigated the flow topology of tandem blades at a cascade with respect to secondary flow structures. They showed that the gap flow has a strong influence on the boundary layer of the rear blade, resulting in different corner vortex formation.…”

Aerodynamic optimization to tandem stators by using sweep and dihedral

“…They emphasized the importance of finely designing parameters to fully exploit the performance potential of tandem blades. Heinrich et al 8,9 studied the influence of gap flow on aerodynamic performance and found that if the size of the gap is large, the two rows of blades tend to work independently, but if narrowing the gap, the separation flow on the suction side of the rear blade will shrink. Hergt et al optimized and investigated a state-of-the-art highly loaded transonic compressor tandem cascade in their recent research.…”