EXPERIMENTAL EVALUATION OF PERFORMANCE AND MECHANICAL RELIABILITY FOR HIGH PRESSURE CO2 INTEGRALLY GEARED COMPRESSOR

Abstract

Energy saving has become a trend as well as a countermeasure for global environmental issues. It can be one of the efficient solutions for reducing energy consumptions by adopting integrally geared compressors instead of inline compressors for industrial plants. The development of key technologies for the design centrifugal compressor such as CFD, FEM, Rotor dynamic Analysis has enabled integrally geared centrifugal compressors for higher pressure applications than ever. A commercial size, 5 stages integrally geared CO2 centrifugal compressor of 20MPaG discharge pressure level was designed, manufactured and evaluated the fluid dynamic performances and rotor stability. It was installed in OEM’s factory and the full load and full pressure test was carried out using real CO2 gas. The actual compressor fluid dynamic performance has shown superior results even at high pressure supercritical gas conditions at the high pressure stages of the compressor. The mechanical performances such as rotor vibration and bearing temperature were also measured and observed that the vibration was substantially low and within safe limits even at high pressure operating conditions above 20MPaG. Also the authors established a novel on Direct Rotor Excitation Method to experimentally investigate the rotor stability even at a high operating pressure level of 20MPaG. With this technique the measurements of the actual rotor natural frequencies and the damping ratios (log decrement) during high pressure operating conditions provided more precise results rather than conventional casing excitation method. The open impeller blade vibration was measured during running condition by using a non-contact blade vibration measurement technique. This measurement results revealed that impeller blades stress against the centrifugal force and the external excitation force was very low compared to the allowable stress value of the impeller material. The fluid dynamic characteristics and mechanical reliability are assessed as acceptable including super critical gas condition of CO2 gas.