Numerical loss analysis in a compressor cascade with leading edge tubercles

Abstract

A numerical analysis of loss has been carried out to explore the loss mechanism of leading edge tubercles in a high speed compressor cascade. Taking the lead from flippers of the humpback whale, tubercles are passive structures of a blade for flow control. Evaluation of the overall performance in terms of entropy increase shows that the loss reduction is achieved both at high negative and high positive incidence angles, while a rise in the loss is obtained near the design point. And a smaller wave number as well as a smaller amplitude results in lower additional losses at the design point. Spanwise and streamwise distributions of pitchwise-averaged entropy increase combined with flow details have been presented to survey the loss development and, subsequently, to interpret the loss mechanism. The tubercle geometry results in the deflection flow and the consequent spanwise pressure gradient. This pressure gradient induces formation of counter-rotating streamwise vortices, transports away the low-momentum fluid near wall from crests towards troughs and leads to local high loss regions behind troughs as well as loss reduction behind the crests in comparison to the baseline. The interaction between these vortices and flow separation by momentum transfer leads to separation delay and the consequent loss reduction at the outlet.

Study on the behavior of streamwise vortices formed between leading edge tubercles in a compressor cascade

“…The amplitude and wave number of the tubercles are respectively fixed at A = 0.03l and N = 2. These parameter values are selected according to the geometrical features of the baseline airfoil, suggestions given by studies of pioneering researchers (Johari et al, 2007;Hansen et al, 2011) and experience from the previous work done by the authors (Zheng et al, 2016(Zheng et al, , 2018. Table 2 gives the details of different configurations.…”

“…However, the analysis on streamwise vortices are not involved. The authors have carried out a previous study (Zheng et al, 2018) in compressor cascades elaborating the underlying loss mechanism of tubercle structures. But there still remains something unknown such as the formation mechanism and development process of streamwise vortices induced by the leading edge tubercles.…”

Preliminary Numerical Study of a Rectilinear Blade Cascade Flow for a Determination of Aerodynamic Characteristics

“…These losses primarily affect the values of the total pressure rise generated and the efficiency of the flow machine. An approach to analyse such issues is included in [20]. [21] shows a comparison of numerical results with experimental results of flow through a set of blade cascades.…”