Optimization of Mixed Helical-Labyrinth Seal Design to Improve the Efficiency of the Machine

Paudel, Wisher, Mechanical and Aerospace Engineering - School of Engineering and Applied Science, University of Virginia
Wood, Houston, En-Mech/Aero Engr Dept, University of Virginia

Non-contacting annular seals are used in rotating machinery to reduce the flow of fluid across a pressure differential. Helical and labyrinth groove seals are two types of non-contacting annular seals frequently used between the impeller stages in a pump. Labyrinth seals have circumferential grooves cut into the surface of the rotor, the stator, or both. They function to reduce leakage by dissipating kinetic energy as fluid expands in the grooves and then is forced to contract in the jet stream region. Helical groove seals have continuously cut grooves in either or both of the rotor and stator surfaces. Like labyrinth seals, they reduce leakage through dissipation of kinetic energy but also have the added mechanism of functioning as a pump to push the fluid back towards the high pressure region as it tries to escape. Several works in literature have shown that labyrinth and helical groove seals with grooves on both the rotor and the stator surfaces have lower leakage than seals with grooves on just one surface.
The goal of this work is to analyze seals with helical grooves on one surface and labyrinth grooves on the other for both high pressure and low pressure applications. Designs for both helical stator, labyrinth rotor and helical rotor, labyrinth stator are simulated and the performance of each configuration is compared. The primary variables considered for the designs of the seals include the width, depth, and the number of grooves for labyrinth seals and the width, depth, and the angle of the grooves for helical seals. The set of simulation designs is chosen using a Kennard-stone algorithm to optimally space them within the design space. Then, for both configurations, multi-factor quadratic regression models are generated. Backward regression is used to reduce the models to only statistically significant design parameters. From there, the response surfaces are created to demonstrate the effects of each design parameter on the performance of the seal. Finally, an optimal design is produced based on the regression models.
The designs are simulated to show the predictive power of the regression models. The simulations for this work are run in ANSYS CFX for each seal type and configuration and the solutions are compared against those from previous studies. The findings from this study were hypothesized to show substantial decrease in leakage for a mixed helical-labyrinth seals in comparison to the seal with either helical or labyrinth grooves on both surfaces. Thus, the effectiveness of mixed helical labyrinth grooved seals is highlighted for both low and high pressure cases and their efficiency and reliability for numerous industrial applications.

MS (Master of Science)
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