ANALYTICAL LEAKAGE MODEL DEVELOPMENT FOR LABYRINTH SEALS WITH HONEYCOMB STRUCTURE: VALIDATION AND DESIGN OF EXPERIMENTS

Honeycomb structures are commonly used for many years in land and air turbomachinery applications to enhance the sealing effectiveness of labyrinth seals. Leakage control is the primary asset for honeycomb seals and directly impacts system-level efficiency; thus, estimating the correct leakage flow rate is crucial for the gas turbine engine performance. Leakage predictions are reliable for smooth land configurations using empirical correlations from available literature, however, accurate predictions are considerably challenging in the presence of honeycomb structures. This paper aims to develop a robust analytical model to estimate accurate leakage mass flow rate by identifying the parameters influencing the flow discharge behavior of honeycomb seals. Reynolds-Averaged Navier-Stokes (RANS) based numerical simulations were performed to investigate flow phenomenon inside the labyrinth seals and honeycomb structures. Experimental test results of Stocker and Collins are the basis of numerical simulations for validation and design of experiments studies. Design of experiments studies were conducted to derive flow coefficients by changing operating conditions and geometric parameters of honeycomb and labyrinth seals. In the available literature, there are limited efforts taken to investigate the flow dynamic behavior of alternative and deteriorated honeycomb structures. For this reason, deteriorated honeycomb structures were investigated for radial displacement, rub groove events, and alternative liner geometries (slanted, square, triangle, circle) were examined and discussed in addition to the conventional honeycomb structures. The proposed analytical model shows good agreement with the test results and has an extensive application range with reliable leakage prediction accuracy for straight-through labyrinth seals with honeycomb structures. The current model serves as a guideline for secondary air system design engineers and helps in the progress of honeycomb seal design in addition to analytical leakage models.