Session: 8.4 - Turbomachinery

Paper Number: 158094

158094 - Study on the Effect of Inhaled Droplets on Internal Energy Loss in the Centrifugal Compressor 

Abstract: 

Marine centrifugal compressors utilize atmospheric air directly as a working medium, which inevitably contains a certain amount of water vapor droplets and other impurities. While various solid impurities can be removed using high-efficiency intake filtration systems, the presence of water vapor and droplets in the air poses unavoidable impacts on the compressor system. Once the droplets enter the centrifugal compressor, they undergo heat and mass transfer with the airflow through evaporation, complicating the internal flow field structure. The evaporation of droplets provides a cooling effect to the compressor. However, the frequent turbulent fluctuations in the surrounding airflow result in high-frequency slip between the droplets and the surrounding gas, causing significant aerodynamic and mechanical loss within the compressor. To better identify and control the sources of loss induced by droplets in the centrifugal compressors, this paper initially investigates the typical flow characteristics of droplets within the compressor, simulation requirements, and method adaptability, selecting the Euler-Lagrange particle tracking method as the numerical technique for the two-phase flow. A bidirectional coupling numerical simulation method between droplets and airflow is established, considering their mutual interactions. The numerical model incorporates a droplet evaporation phase-change model, a droplet breakup model, and a droplet-wall impact model for simulation purposes, allowing for a visual analysis of the internal flow field under the influence of droplets. The study examines the movement, forces, and breakup of droplets in the airflow, along with the impact of droplets on compressor blades and the resultant effects on performance. Entropy generation rate is employed to quantitatively analyze energy loss within the compressor, unveiling the variation patterns and mechanisms of loss under the influence of droplets. Utilizing Fast Fourier Transform and spectral analysis methods, the study explores the amplitude fluctuations in the time domain and principal frequency shifts in the frequency domain of the centrifugal compressor's flow field and performance parameters. It was found that the intrusion of liquid droplets significantly increases these fluctuations and alters the original oscillation characteristics of the compressor parameters, forcing it to operate under a series of suboptimal conditions characterized by low frequency, large amplitude, and long cycles, thereby compromising operational stability. When the intake moisture content or droplet size increases, the main amplitude of fluctuations further increases, yet the principal frequency remains unchanged. By revealing the mechanisms of flow field changes and loss mechanisms induced by droplets, this paper provides essential guidance for the design of high-efficiency centrifugal compressors.

Presenting Author: jun zhang zhejiang university

Presenting Author Biography: Jun Zhang is currently a Doctor’s degree candidate in the Institute of Process Equipment, College of Energy Engi-neering, Zhejiang University (China). His research interests are in the design of low vibration centrifugal compres-sors.