(172b) Centrifugal Compressor Surge Exploration TESTS and Second Quadrant Characteristic Dynamic Modeling

High Pressure Ration Compressor (HPRC) technology is based on an innovative architecture that combines unshrouded and shrouded impellers on a single high-speed shaft to achieve pressure ratios and efficiency levels higher than other available technologies. As final step of the product development and validation, a test campaign has been carried out aimed to test the performance and explore the operability of the new machine.
Surge exploration tests have been also performed allowing an evaluation of the transient behavior and the mechanical robustness of the compressor even during a critical event such as Surge.
Compressor Surge has been analyzed under different conditions, forcing the operating point to move beyond the performance envelope in full speed, at low and high pressure levels, and during emergency shut-downs. Thanks to the complex arrangement of the gas loops and several valves used to recycle back the compressed gas, different level of Surge intensity were induced upon emergency shut-down.
The explorations of a fast event like Surge called for special instrumentations, configured to acquire process data both in direct and reverse flow condition in the most reliable way, with a high frequency sampling for an Oil and Gas environment.
The results of this work is a breakthrough for the tuning of a centrifugal compressor model - not only HPRC ones - to be used for dynamic simulations and prediction of compressor dynamics during Surge events (like Surge cycle frequency and absorbed torque during Second Quadrant operation) in more reliable and robust way.
Surge exploration tests results analysis in terms of vibrations and thrust loads, together with development of a compressor enhanced dynamic model, allowed to move from a Surge acceptance criterion based on the time spent on the left of the Surge Limit Line during an Emergency Shutdown event to a more physics based criterion based on the acceptable number of Surge cycles, thus increasing selection optimization of additional protections like hot/cold gas bypass valves.