Numerical study on the leakage characteristics of a stepped labyrinth seal with mixed honeycomb cell diameters

As the performance improvement of gas turbines becomes marginal, it is required to develop a seal geometry that can reduce unwanted leakage more effectively than conventional seals. Accordingly, in this paper, a new honeycomb structure with improved sealing performance was suggested. The proposed seal is a mixed honeycomb seal (MHS), where honeycomb cells with a smaller diameter (D′) are inserted into the base honeycomb structure with a cell diameter (D) to reduce the effective clearance. To compare the performance of the mixed honeycomb seal and a uniform honeycomb seal (UHS), computational fluid dynamics (CFD) analyses were performed by altering the pressure ratios and clearance sizes. At the same pressure ratio and clearance size, the MHS shows a performance improvement of up to 19 % (i.e., less leakage flow rate) compared to the UHS. In addition, the effects of D and D′ on the leakage performance were examined through a parametric study.