Effects of Radial Gap Ratio between Impeller and Vaned Diffuser on Performance of Centrifugal Compressors

Abstract

Abstract:A high-performance centrifugal compressor is needed for numerous industry applications nowadays. The radial gap ratio between the impeller and the diffuser vanes plays an important role in the improvement of the compressor performance. In this paper, the effects of the radial gap ratio on a high-pressure ratio centrifugal compressor are investigated using numerical simulations. The performance and the flow field are compared for six different radial gap ratios and five rotational speeds. The minimal radial gap ratio was 1.04 and the maximal was 1.14. Results showed that reducing the radial gap ratio decreases the choke mass flow rate. For the tip-speed Mach number (impeller inlet) with M u < 1, the pressure recovery and the loss coefficients are not sensitive to the radial gap ratio. However, for M u ≥ 1, the best radial gap ratio is 1.08 for the pressure recovery and the loss coefficients. Furthermore, the impeller pressure ratio and efficiency are reduced by increasing the radial gap ratio. Finally, the compressor efficiency was compared for different radial gap ratios. For M u < 1, the radial gap ratio does not have noticeable effects. In comparison, the radial gap ratio of 1.08 has the best performance for M u ≥ 1.

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

“…The first is radial clearance-if it is too long, the gas flow path is prolonged, thereby increasing friction loss; if it is too short, the rotor and stationary blades interfere with each other such that the wake of the impeller blade affects the uniformity of the inlet air flow at the stationary blade (Ji, Li, Fang, & Sun, 2018). 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).…”

Investigation of the Influence of Splitter Blades on the Resonance Conditions of Impellers

“…The excitation from the impeller-diffuser interaction is the main excitation acting on the impeller. Because the impeller-diffuser radial gap is becoming smaller by design [13,14], the interaction is getting more intense and the resulting unsteady aerodynamic loads are bigger. Moreover, the five-axis machine is now a common tool for impeller machining and the impeller is machined as one piece with very low structural damping [15,16].…”

Loss Mechanism of Static Interstage Components of Multistage Centrifugal Compressors for Integrated Blade Design

“…Impeller-diffuser interaction has also been studied for improving the performance of centrifugal compressors, as it is an important part of the complete machine [7]. Tamaki [8] 2 Mathematical Problems in Engineering performed experiments using seven different vane diffusers and the same impeller, to study the influence of diffuser blade installation angle on the performance of a centrifugal compressor.…”