Stage selection
CST optimizes the compressor thermodynamic design, starting from standardized compression stages (integrally geared or between bearings compressor layout, 2D or 3D open or close impellers, vaneless or vaned diffusers, bladed return channels or volutes), to be adapted to customer requirements. Through this approach, we select the best stage configuration, matching the specific application and compressor performance curves, from choke to surge as a function of speed or IGV position.
Real gas equations of state are used to guarantee accurate performance curves.
Once the machine configuration is selected, the aerodynamic design of rotating and stationary components is defined. All geometries (impellers, diffusers, volutes or return channels) are optimized to maximize efficiency and flow capability across the operating range.
3D model CFD simulation
3D CFD simulations are widely used by CST for:
- Detailed design and optimization of standardized stages (impeller, diffuser and volutes or return channels). CFD allows to obtain an accurate characterization of velocity fields, pressure distribution and minimize sources of losses.
- Performance assessment on design and off-design conditions, determining compression efficiency and power consumption to verify the preliminary stage selection.
- Specific investigation for In-Field Support activities (e.g. justify performance decay, investigate modifications/actions aimed to refurbish old compressor).
FE structural & modal analyses
The Finite element analysis (FEA) is typically performed by CST, here are some applications:
- Characterize the structural behavior of every critical component, to assure compressor integrity and rubbing avoidance (e.g. impeller tip/casing shroud clearances).
- Impeller dynamic behavior assessment (natural frequencies and mode shape); Singh's Advanced Frequency Evaluation (SAFE) diagram approach is used to avoid resonance conditions.
Rotor-Dynamics
CST gives special attention to all the aspects of the dynamic behavior of rotating parts
In addition to impeller modal analysis a rotodynamic study of rotating parts (pinion shaft of IGC, compressor shaft of between bearings ) is carried out by Lumped Parameter Models. This is according to API617 and API684 Standards, focusing on:
Lateral analysis for calculation of:
- natural frequencies & mode shapes,
- response to unbalance,
- stability. </ul >
Torsional analysis for calculation of:
- natural frequencies & mode shapes,
- torsional forced response.
- Lateral analysis for calculation of:
- natural frequencies & mode shapes,
- responce to umbalance,
- stability
- Torsional analysis for calculation of:
- natural frequencies & model shapes
- torsional forced response
Inlet guide vane
Variable Inlet Guided Vanes (known as IGVs) are commonly used to control the inlet mass flow of integrally geared compressors. IGV can lead to important energy savings with respect to a conventional inlet butterfly valve. This component strongly affects overall compressor performance and represents a critical component to design. CST has invested a significant effort to design IGVs for both levers and gear actuating system.
Fully comprehensive compression unit engineering design
Process centrifugal compressors are designed by CST based on customer’s needs and requirements, in accordance with API617 Standards or API672 in case of packaged IGC for air.
Control and anti-surge
CST engineering services also include the philosophy of the control system, and the study and optimization of the best solution to prevent surging.
Dry gas seal system selection and specification
CST collaborates with the most reputed suppliers of dry gas seals with the aim to select the best solution for this very important component and its relevant system.
Lubrication systems for rotor bearings, gearbox and motor
CST can design customized systems based on specific requirement for the machine and customer needs.
