Assessment of turbulence model predictions for a centrifugal compressor simulation

Abstract

Steady-state computational fluid dynamics (CFD) simulations are an essential tool in the design process of centrifugal compressors. Whilst global parameters, such as pressure ratio and efficiency, can be predicted with reasonable accuracy, the accurate prediction of detailed compressor flow fields is a much more significant challenge. Much of the inaccuracy is associated with the incorrect selection of turbulence model. The need for a quick turnaround in simulations during the design optimisation process also demands that the turbulence model selected be robust and numerically stable with short simulation times. In order to assess the accuracy of a number of turbulence model predictions, the current study used an exemplar open test case, the centrifugal compressor “Radiver”, to compare the results of three eddy-viscosity models and two Reynolds stress type models. The turbulence models investigated in this study were: (i) Spalart-Allmaras (SA), (ii) Shear Stress Transport (SST), (iii) a modification to the SST model denoted the SST-curvature correction (SST-CC), (iv) Reynolds stress model of Speziale, Sarkar and Gatski (RSM-SSG), and (v) the turbulence frequency formulated Reynolds stress model (RSM-ω). Each was found to be in good agreement with the experiments (below 2% discrepancy), with respect to total-to-total parameters at three different operating conditions. However, for the near surge operating point P1, local flow field differences were observed between the models, with the SA model showing particularly poor prediction of local flow structures. The SST-CC showed better prediction of curved rotating flows in the impeller. The RSM-ω was better for the wake and separated flow in the diffuser. The SST model showed reasonably stable, robust and time efficient capability to predict global performance and local flow features.

CFD Modelling of a Centrifugal Compressor with Experimental Validation through Radial Diffuser Static Pressure Measurement

“…Following [11][12][13][14] the k-SST model was selected. The chosen k-SST model is widely used and has been validated for turbomachinery applications [20].…”

“…This is the same approach as used in [7,18]. The combination of a total pressure and temperature inlet with a mass flow rate outlet is the approach favoured for stability [11]. The hub and shroud for the inlet and diffuser domains, the hub for the impeller domain, and the blades themselves were set to wall (adiabatic, no slip, and smooth wall) boundary conditions.…”

“…Out of the accumulation of a body of work, a number of common approaches have resulted in terms of CFD model settings with regard to turbulence models [11][12][13][14], interface settings [4,6,7,9,[15][16][17], and boundary conditions [7,11,18]. There are a number of turbulent models which can be applied in a RANS simulation.…”

“…There are a number of turbulent models which can be applied in a RANS simulation. Gibson et al [11] assessed the performance of different turbulence models for the numerical simulation of a centrifugal compressor. Simulations were performed using different models including the Spalart-Allmaras, SST, a modified SST approach (SST-CC), and a turbulent frequency formulated Reynolds stress model (RSM-).…”

Mechanisms of Sweep on the Performance of Transonic Centrifugal Compressor Impellers

“…Near surge conditions, significant differences between turbulence models occur because the predicted fully separated flow in blade passages is highly depended on the modeled turbulent viscosity, but there seems to be no universal turbulence model that is always superior to others [31]. Assessment of turbulence models in centrifugal compressors were carried out in the SRV2-O case [32] and the Radiver case [33]. It is generally found that the Spalart-Allamaras model, the k-ω shear stress transport model, the v 2 -f-k-ε Durbin model and the Reynolds stress model can predict very similar flow features at the impeller peak efficiency condition, but the Spalart-Allamaras model has limitations in vaned diffuser flow fields where the fully separated flow is dominate.…”