Session: 23-14: Seal Turbomachinery Applications II

Submission Number: 178353

Effect of Surface Roughness on See-through Labyrinth Seals in Supercritical CO2
Turbomachinery 

Design and development of radial turbomachinery is being extensively explored for a sub megawatt supercritical carbon dioxide (sCO2) Brayton power cycle. Parasitic losses in a sCO2 radial turbomachinery are key concerns and pose commercialization challenges. These losses comprise mass flow leakage and viscous drag (windage) exerted by the fluid on the rotor at the turbomachinery back side cavity. Labyrinth seal is prominently used to mitigate the parasitic losses. The theoretical, experimental, and numerical investigation to evaluate the labyrinth seal performance ideally neglected the effect of realistic internal surface roughness. Presently, advancements in technology have made it possible to achieve a seal clearance of <150 microns. At this small seal clearance, the influence of surface roughness on pressure drops and fluid flow is significant. However, these effects have yet to be quantified in existing literature. Comprehensive CFD investigation is conducted to evaluate the impact of surface roughness on labyrinth seal performance under key seal geometric variables and operating conditions. A detailed investigation of flow physics within the labyrinth seal is also conducted. Arithmetic average roughness (Ra) values vary from 0 to 10 microns in CFD analysis, including smooth and rough internal surfaces of the labyrinth seal. Preliminary CFD findings reveal that roughness increases momentum transfer across the fluid layer at seal clearance region, which reduces mass flow leakage. In contrast, seal windage loss increases with an increase in surface roughness. This suggests that a detailed understanding of the effect of surface roughness on internal flow structure and labyrinth seal performance contributes significantly to improving seal design.

Presenting Author: Saurabh Lanjewar Indian Institute of Science Bengaluru, Karnataka

Presenting Author Biography: The presenting author is Saurabh Deorao Lanjewar. He is from Maharashtra, India. He finished
his Bachelor's in the Mechanical Department at Nagpur University, Maharashtra, in 2019. He
has done his Master's in Heat Power Engineering at VNIT, Nagpur, in 2021. Presently, he is
pursuing his PhD in the Mechanical Department at IISc, Bengaluru, India. In IISc, he works
with Prof. Pramod Kumar in the sCO2 Lab.

Authors:

Saurabh Lanjewar Indian Institute of Science Bengaluru, Karnataka
Pramod Kumar Indian Institute of Science Bengaluru, Karnataka
Jayshankar Ray Triveni Turbines Limited