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.
Highlights
The idea of using CR machines goes back a long way
The objective of this work was to present a first experimental validation of a design method adapted to an innovative CRCC using two successive impellers
The aim of the study was to investigate experimentally the aerodynamic performances of this new layout compared to a baseline
Summary
The idea of using CR machines goes back a long way. Already in 1825, a certain engineer named Jacob Perkins, and in 1829, William Church, had imagined this solution for boat propellers [1]. Lesley [2] performed a first experimental study of these machines in 1933 on counter-rotating propellers. Since those machines have attracted great interest in the turbomachine application by their particular potential to improve performance over conventional ones by exploiting the counter swirl of the flow received by the downstream rotor. Those machines have attracted great interest in the turbomachine application by their particular potential to improve performance over conventional ones by exploiting the counter swirl of the flow received by the downstream rotor This is possible by recovering the flow from the upstream impeller and adding energy to it by turning the downstream impeller in the opposite direction. This configuration should allow an increase of the head compared to its conventional counterpart in comparable sizes and gives an additional degree of freedom resulting from the second turning impeller
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