Translated Abstract
Multi-stage centrifugal compressor is widely applied in industries like petrochemical industry, coal chemical industry and natural gas due to its long operation time, less wearing parts and low maintenance costs. Because high efficiency and wide working condition range are always used as criteria to evaluate the operational benefit of a centrifugal compressor, a lot of researchers at home and abroad have carried on the intensive investigate to impeller and diffuser in order to increase the performance of centrifugal compressor. However, in a multi-stage centrifugal compressor, the aerodynamic performance of the return system plays a significant role in the efficiency of the whole machine.
In this thesis, return channel of centrifugal compressor is studied by numerical investigation and optimization method in detail.
First, a return channel of basic stage D of multi-stage centrifugal compressor is numerically investigated in depth, obtaining the improved meridian plane profile and return channel vanes which can bring about the optimal polytropic efficiency of the basic stage D. The results show that there is usually an optimal b5_Ref=b5/ b4 for each basic stage, and the inlet width b5 has on influence on inlet setting angle α5A of the return channel vane to some extent, which should be considered in design procedure. The increase of the return channel vane number has a certain effect on suppressing the secondary flow in the return channel, but it also increases the friction loss in return channel. Therefore, the number of the vane of the return channel should be considered because of the flow loss.
More, two types of return channel vane, ARV(Aungie Return channel Vane) and DRV(Double circular Return channel Vane)，for basic stage D are designed. Two types of basic stage that separately configure with ARV and DRV return channel are studied numerically. The results show that the aerodynamic performance of stage D-ARV is more higher than stage D-DRV, the polytropic efficiency ηpol of stage D-ARV is increased by 1.31% than that of stage D-DRV when flow coefficient φ1 is equal to 0.026.
Then, the influence of the vane loading distribution controlling parameter K5 of the ARV is studied numerically in detail. The results show that K5 has a great influence on the performance of return channel. The polytroic efficiency of the return channel reaches to the maximum values when K5 is equal to 2.4.
Finally, through the parametric modeling for the return channel cascade, optimization design for the return channel vane shape of basic stage D-ARV is conducted by the method combined with artificial neural network, CFD technology and genetic algorithm. After optimization, the camber angle and the vane thickness became low, and the return channel vanes show a three dimensional structure. The results show that optimized three dimensional vanes are beneficial to reduce the loss in return channel, increase the static pressure recovery coefficient and improve the flow uniformity in flow passage of return channel. Three dimensional return channel vane can improve the whole stage performance remarkably at the off-design conditions. The stage polytropic efficiency ηpol increases by 2.32% when flow coefficient φ1 is equal to 0.026.
Translated Keyword
[Basic stage, Centrifugal compressor, Numerical study, Optimization, Return channel]
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