Experimental and Numerical Investigation of the Unsteady Flow Field in a Vaned Diffuser of a High-Speed Centrifugal Compressor

Wang

Proceedings of the Institution of Mechanical Engineers, Part A:

et al. 2017

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.

Section: Introductionmentioning

confidence: 99%

“…Vogel et al. 7 used high-response transducers to investigate transient behaviors in the diffuser. Their results revealed that the high intensity of impeller–diffuser interaction spreads all along the diffuser vane.…”

Section: Introductionmentioning

confidence: 99%

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

Wang

Proceedings of the Institution of Mechanical Engineers, Part A:

et al. 2017

“…Gallier, Lawless, and Fleeter (2010) found that there is a highly nonuniform flow field in the vaneless space between the impeller and the diffuser that results in a large variation in the flow angle at the diffuser vane leading edge and subsequently causes an unsteady vane loading. Vogel, Abhari, and Zemp (2014) indicated that with an increase in the flow coefficient, the pressure fluctuation amplitude decreases in the diffuser passage. Zhao et al (2015) employed CFD techniques to analyze the interaction of the inlet guide vane and the impeller, observing two loading peaks at the impeller blade leading edge for a small mass flow coefficient during a passage cycle.…”

Section: Introductionmentioning

confidence: 99%

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

Engineering Applications of Computational Fluid Mechanics

Liu

et al. 2016

The unsteady phenomenon abounds in centrifugal compressors and significantly affects the compressor performance. In this paper, unsteady simulations are carried out to investigate the aerodynamic performance of a process-unshrouded centrifugal compressor and the unsteady mechanism in the vaned diffuser. The predicted stage performance and pressure fluctuations at some locations are in good agreement with experimental data. The predicted main pressure fluctuation frequency spectrums at the diffuser inlet and outlet are consistent with the measured results. The results indicate that at the inlet of the diffuser there are two pressure peaks in a passage cycle. The higher pressure peak relates to the impeller wake and the lower peak is connected with the vortex generated at the diffuser's leading edge. With a decrease in the mass flow coefficient, the vortex core region becomes larger and the lower pressure peak becomes more pronounced. The change in circumferential flow angle at the diffuser inlet is mainly responsible for the unsteadiness in the diffuser flow field, which in turn affects the inlet incidence of the diffuser vane and the vane loading distributions. ARTICLE HISTORY

Advances in Mechanical Engineering

“…Burguburu and le Pape 22 reported the numerical aerodynamic optimization of a transonic compressor, and found that the suction of a 2D blade is optimized with a significant efficiency improvement. Vogel et al 23 carried out unsteady numerical simulation of centrifugal compressor, and found that the inlet pressure fluctuation is as high as 34.4%. Rao et al 24 found that TVD with radius ratio of 1.10 and impeller diffuser is the optimal configuration under the condition of blade tip Mach number of 0.35.…”

Section: Introductionmentioning

confidence: 99%

Numerical study on the flow characteristics of centrifugal compressor impeller with crack damage

Liang

Xiang

Wei

et al. 2021

The distribution and characteristics of internal flow field of the impeller with crack damage in service environment was investigated via numerical simulation with RNG k-ε turbulence model. The diffuser and volute are added based on the original impeller to simulate the internal flow field comprehensively. It was found that along the flow direction, the pressure, velocity, and temperature of the fluid increase continuously, and the maximum value appears near the outlet of the impeller. The maximum pressure and velocity in the crack area are distributed around the middle section and the trailing edge of the crack. Entropy production theory was applied in the study of internal flow, which reveals that the entropy production becomes larger around the crack. The further propagation of the crack is promoted by the opening force perpendicular to the entrance direction of the middle crack, the corrosion propagation at the rear edge of the crack, and the thermal deformation of the blade. The accelerated crack process will finally lead to the blade fracture accident.