Multi-Blade Row Interactions in a Low Pressure Ratio Centrifugal Compressor Stage With a Vaned Diffuser

Abstract

Previous experimental and CFD investigation of a GE Oil and Gas centrifugal compressor stage with a vaneless diffuser revealed a complex excitation mechanism caused by an aero-acoustic interaction between three blade rows. In stages with vaned diffusers, additional sources of aeromechanical excitation on the impeller can be expected. This unsteady CFD investigation is a follow-up from the previous vaneless diffuser study to identify any additional sources of excitation that arise in the presence of a vaned diffuser in preparation for aeromechanic tests to be conducted later. The study confirms that excitation from impeller-diffuser interaction generated acoustic modes can dominate the potential field excitation from the diffuser vanes. In addition, a significant aero-acoustic excitation to the impeller at a vane pass frequency corresponding to the sum of the vane counts in the two downstream vane rows is observed, and its origination is discussed. The latter excitation is different from that observed in the vaneless diffuser stage where the vane pass frequency observed by the impeller corresponds to the sum of the vane counts in the upstream and downstream vane rows.

Cavity Flow Modeling in an Industrial Centrifugal Compressor Stage at Design and Off-Design Conditions

“…Previous validations and modeling experiences with TACOMA on centrifugal compressor stages can be found in [16], [17], [18] , [1] and [19] .…”

Description of the Flow in a Two-Stage Low-Pressure Turbine With Hub Cavities

“…This last contribution emanates from the cooling requirements of the rotor disks under the main flow passage that induce additional losses by a blowing process of the cavity flow in the main annulus. The understanding of these effects is important since potential for further improvement in the turbomachine are still expected with the potential unsteady effects [4], mixing processes due to non-uniformities, intermittent wakes [5], and interaction between the different blade rows [6]. The interactions of wakes of upstream rows can have a strong impact on the stability and turbulent characteristic of the downstream blades boundary layers and endwall losses as experimentally studied by Steurer et al [7] using upstream moving bars to generate wakes on a low-pressure turbine cascade.…”

The Efficient Numerical Simulation of Unsteady Flow in a Centrifugal Compressor Stage Equipped with a Vaned Diffuser

“…Their study showed the efficiency of the TT method in terms of computation costs and accuracy. Ramakrishnan et al (2011) presented unsteady CFD results on a compressor stage equipped with a vaned diffuser. In this paper, the authors identified the aerodynamic modes in the radial gap between the impeller and the vaned diffuser only through numerical simulations, according to the Tyler-Sofrin theory (1961).…”