Investigation of transient flow characteristics inside a centrifugal compressor for design and off-design conditions

Abstract

As the flow rate decreases from the design to the rotating stall condition, the enhanced impeller-diffuser interaction considerably deteriorates the flow condition at the diffuser inlet, which may trigger stall and blade vibration problems. In order to reveal the underlying mechanism and estimate the impact of the interaction within the impeller and diffuser passages, measurements using the wireless acquisition technique and high-frequency response system have been conducted on a 1.5 stage centrifugal compressor with the vaned diffuser. The details of its transient flow characteristics suggest that the effects of the impeller sweep extensively propagate in the diffuser passage. Distinctions of the shroud reversed vortex effect exist between the main and splitter blades at the impeller outlet, which initiates the predominant passage passing frequency at the diffuser inlet under small flow rate condition. In addition, the present study explains why the dominant disturbance shifts back and force between the passage passing frequency and blade passing frequency for different positions of the diffuser and flow rates. Through flow throttling, the diffuser reaction toward the impeller passage considerably strengthens due to the growing pressure potential near the convex surface of the diffuser vane, which is associated with the reversed flow.

Analysis and application of shroud wall optimization to an axial compressor with upstream boundary layer to improve aerodynamic performance

“…With respect to the validations conducted by other researchers, performance maps and inner flow-fields predicted by NUMECA FINE-Turbo also correspond well with the available experimental results (Wang et al , 2015; Zhao et al , 2018). Based on the aforementioned validations, it is believed that the CFD tool and method used in this work can provide reliable and accurate flow-field details and performance map predictions for a transonic axial-flow compressor.…”

Optimization of a transonic axial-flow compressor under inlet total pressure distortion to enhance aerodynamic performance

“…Specifically, an explicit fourthorder Runge-Kutta scheme is employed for temporal discretization, while the second-order central-differencing scheme is utilized for spatial discretization. The Spalart-Allmaras turbulence model has been used in this work due to its successful applications and good performances in fluid machines (Elfarra, 2019;Lu et al, 2019;Suarez et al, 2018;Zhao et al, 2018).…”

Numerical investigation of deep surge in a centrifugal compressor with vaned diffuser and large plenum

“…Because the paper is to investigate the deep surge phenomenon at low mass flow rate, the unsteady simulated data at low mass flow rate (3.5 kg/s) near surge are compared with the experimental measurement to validate the numerical model. In the previous paper, 21 two high-response Kulite pressure transducers were located at the 5% and 40% chord of the pressure surface of the diffuser blade to investigate the unsteady behavior induced by rotor/stator interaction at off-design condition. An assembly-averaged technique is utilized to eliminate the random disturbance in the experimental data.…”

“…The centrifugal compressor was originally designed for the investigation on the detailed feature of internal flow to develop its design theory. Our team have done a large quantity of researches on the rig, covering rotor/stator interaction, 20,21 vane clocking effect 22 and diffuser rotating stall. 23 The detailed description of the experimental measurement can be found in the previous papers.…”