Computational investigation of impeller—diffuser interaction in a centrifugal compressor with different types of diffusers

Abstract

A computational study has been conducted to analyse the performance of a centrifugal compressor with different types of diffusers under various levels of impeller—diffuser interactions. Vaneless (VLD), vaned (VD), low solidity vaned (LSVD), and partial vaned diffusers (PVD) are used for this purpose. The study is carried out using commercial software ANSYS CFX. The interaction level is varied by varying the radial gap between the impeller and diffuser by keeping the diffuser vane at three different radial locations. Numerical simulations have been conducted for four different flow coefficients. At design flow coefficient maximum efficiency occurs when the leading edge is at R3 (ratio of radius of the diffuser leading edge to the impeller tip radius) = 1.10 for all vane-type diffuser configurations. At below design flow coefficient higher stage efficiency occurs when the diffuser vanes are kept far away ( R3 = 1.15) and at above design flow coefficient R3 = 1.05 gives better efficiency. The highest diffuser pressure recovery coefficient ( Cp) is observed for VD at design flow coefficient. For VLD, the Cp value increases with flow coefficient. In the case of VD and LSVD configurations the exit flow from the impeller is disturbed when the diffuser vanes are closer, and these disturbances are more evident in the last 10 per cent of the impeller flow. In the case of the impeller with PVD the interaction effects are minimum.

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].…”

“…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.…”

“…They also found the SST model to give the most realistic results. The SST turbulence model is identified as the most appropriate choice for turbomachinery applications in Shah et al 's review [12] and has also been widely used in a range of centrifugal compressor simulations [13,19]. A full discussion of the SST model is given by Menter [20].…”

The effect of impeller–diffuser interactions on diffuser performance in a centrifugal compressor

“…The time step was taken to be the time of an impeller blade passing 1/360 of a circle. This value is the optimum time step according to Anish and Sitaram (2009) and Anish et al (2014). The 'stage' method (ANSYS, 2011a) was adopted for analyzing the IDIs for steady simulations.…”

Influence of rotor–stator component partition structure on the aerodynamic performance of centrifugal compressors

“…Hosseini, Sun, He, and Zheng (2017) achieved a radial clearance ratio that yielded the best pressure recovery coefficient, loss coefficient, and grade efficiency when M u ≥ 1. Optimal radial clearance exists for specific working conditions (Krishnababu, Imregun, Green, & Hoyniak, 2010;Anish & Sitaram, 2009). Robinson, Casey, Hutchinson, and Steed (2012) reported that decreasing the radial clearance ratio substantially increased efficiency.…”