Acoustic: Air Compressor

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Air Compressor Acoustics Analysis in ANSYS Fluent

Introduction

This project investigates the aeroacoustics and noise generation mechanisms of airflow within a four-row multistage axial flow compressor using ANSYS Fluent. As engine manufacturers continue to prioritize noise reduction as a key design objective, understanding the acoustic contribution of individual engine components has become an essential first step toward developing effective noise mitigation strategies. This simulation focuses specifically on quantifying and visualizing the sound power generated by the rotor and stator stages of a compressor assembly, building on prior turbomachinery flow analysis of the same geometry.

Geometry and Mesh

The three-dimensional compressor geometry was constructed in Design Modeler, comprising two rotor rows and two stator rows, with each row containing 22 airfoil-section blades. The rotor blades feature aerodynamic deflection, while the stator blades remain horizontal without deflection. Taking advantage of the geometry's rotational symmetry, only a single blade passage from each rotor and stator row was modeled, with periodic boundary conditions applied to the lateral surfaces to represent the full annular assembly while substantially reducing computational cost. The domain was discretized in ANSYS Meshing using an unstructured mesh totaling 972,354 elements, providing adequate resolution for capturing the flow and acoustic phenomena around the blade rows.

Methodology

The acoustic analysis was performed using the Broadband Noise Sources model within Fluent, applied on top of the underlying turbomachinery flow solution obtained with periodic boundary conditions. Reference acoustic properties were defined consistent with standard air conditions: a density of 1.225 kg/m³, a sound speed of 340 m/s, and a reference acoustic power of 1×10⁻¹² W, forming the basis for computing acoustic power level contours throughout the domain.

Results and Conclusion

Results indicate that the rotor rows are the dominant source of noise generation within the compressor stage, exhibiting substantially higher acoustic power levels in the corresponding contour plots compared to the stator rows. Contours of the linearized Euler equations further illustrate how sound waves propagate through the gap region between successive rotor and stator rows, offering insight into the spatial distribution and directivity of noise transmission within the multistage compressor.