Session: 23-14: Seal Turbomachinery Applications II

Submission Number: 176113

Understanding Fluid Destabilization Forces in the Blade Passage of Centrifugal Compressor Impellers: A Comparative Analysis of Flow Coefficients 

In turbomachinery, the trend toward higher performance, smaller size, and higher speed has led to a decrease in the rigidity of the rotor system and an increase in the pressure and flow velocity, which in turn has increased the fluid destabilization force and increased the risk of vibration problems.
In centrifugal compressors and pumps, closed impellers with a front shroud covering the impeller and a labyrinth seal are generally used. While The fluid destabilization force generated at the front shroud and labyrinth seal components has been studied by CFD analysis and verification tests, there are few researched and evaluated data on the generation mechanism of the fluid destabilization force generated in the main flow between impeller blades.
In this paper, the fluid destabilization force generated in the main flow region of two closed impellers for centrifugal compressors with a large flow coefficient and a small flow coefficient was evaluated by CFD analysis. The following results were obtained.
(1) Fluid destabilization force of a large flow coefficient impeller
- The effect of the blockage near the mixing region of the main flow and leakage flow is dominant, and the counter torque increases in the direction of eccentricity and decreases in the direction opposite to eccentricity.
- The stabilization force at the natural frequency is of the same order as the destabilization force calculated by the modified Alford equation.
(2) Fluid destabilization force of a small flow coefficient impeller
- The effect of the leakage flow is dominant, and the destabilization force is generated by the increase in the flow rate in the direction opposite to eccentricity. However, the destabilization force level is smaller than that of the modified Alford equation to cancel the effect of the blockage, and the destabilization force is almost zero near the natural frequency.
- As with the destabilization force in the front shroud section, the fluid destabilization force in the main flow region also has a frequency dependence and tends to be stabilized in the high-frequency region.

Presenting Author: Shuichi Yamashita Mitsubishi Heavy Industries, Ltd.

Presenting Author Biography: The author graduated from Kyushu University in 2008 and joined MHI (Mitsubishi Heavy Industries). For the past 17 years, he has been engaged in design, research and development as a turbomachinery engineer.
His expertise lies in the aerodynamics of industrial centrifugal compressors.
In recent years, in addition to his research and development work on the aerodynamics of centrifugal compressors, he has been collaborating with mechanical vibration engineers to study the fluid destabilization forces generated in centrifugal compressors.

Authors:

Shuichi Yamashita Mitsubishi Heavy Industries, Ltd.
Makoto Iwasaki Mitsubishi Heavy Industries, Ltd
Shinichiro Tokuyama Mitsubishi Heavy Industries Compressor, Ltd.