Experimental Validation of the Aerodynamic Performance of an Innovative Counter-Rotating Centrifugal Compressor

Abstract

Turbomachinery with double counter-rotating impellers offers more degrees of freedom in the choice of design and control parameters compared to conventional machines. For these innovative machines, the literature review shows that more publications concerning axial type turbomachines are available than centrifugal ones. This work deals with a design and experimental performance analysis, applied to two counter-rotating impellers of a centrifugal compressor “CRCC”. CRCC was designed with a specifically developed tool based on mean-line approach coupled with optimization algorithms and a stream-curvature through-flow method to satisfy the design criteria. This paper presents an experimental validation of the CRCC design tool and its performances against the baseline “SR”, composed of one centrifugal impeller and a volute for which experimental data are available. CRCC numeric simulations are also validated by experimental data. For a fair comparison between CRCC and SR, the same volute is used for both configurations. The CRCC studied here includes a first conventional impeller with an axial inlet and a radial outlet, while the second impeller is parametrically designed and can be considered a rotating bladed diffuser with a radial inlet and outlet. The obtained results show that CRCC can deliver a pressure rise increase of two compared to SR, along with an increase of isentropic efficiency and also validate the design method of this novel layout. The experimental results also show that the speed ratio of CRCC has a positive effect on the surge and shock margin.

A novel experimental control method to suppress instability in a centrifugal compressor with two counter and co-rotating rotors

“…This CFD calculation method follows the numerical approach presented in Reference 21. 21 This figure shows that the incidence at RR leading edge for the operating point with the highest efficiency at _ m c ¼ 0:558kg:s À1 and theta = 1 is about À1.6°. Indeed, this value is excepted not to be equal to zero because CRCC1 is designed at N FR = 17 kRPM and N RR = 13 kRPM and not at theta = 1 with N RR = 13 kRPM.…”

“…The experimental setup shown in Figure 7 consists of a CRCC connected to an open-loop pipeline with a diameter of D = 158.5 mm and already presented in the first part of this work. 21 In Figure 7, a tank (1), on which a perforated plate (2) with 120 holes of 8 mm diameter, is placed upstream the compressor to control the amount of air entering the compressor. A honeycomb is placed inside the long inlet pipe to obtain a flow with minimum distortion for measuring mass flow rate and reducing the effect on the performance.…”

“…For the present experimental setup, CFD simulations were conducted in order to check the distortion caused by the inlet bend, and they showed that there is a very small impact on the stall margin as showed in the work of Abed. 21…”

“…Figures 3 and 4 show the first configuration (CRCC1) for the experimental study using Reference 21 in which its global experimental and numerical performance map and geometric data are presented.

Figure 3.CRCC1 configuration. 21

Figure 4.Counter-rotating centrifugal rotors of CRCC1. 21

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“…[17][18][19] In this study, two counter and co-rotating centrifugal compressors (CRCCs) using a front (FR) and rear (RR) rotors rotating in opposite and in the same direction are presented. It is in fact the second part of the already published work [20][21][22] but focusing only on the active control method to enlarge the map width toward very low mass flow rates by suppressing the instabilities. It's a breakdown technique of instability treatment compared to existing ones.…”