Effect of the tip clearance variation on the performance of a centrifugal compressor with considering impeller deformation

Abstract

The effects of impeller tip clearance variation on centrifugal compressor performance have been investigated experimentally and numerically in a centrifugal compressor. In order to accurately calculate the real tip clearance, the influence of impeller geometry deformation caused by the thermal load (temperature variation) and mechanical loads (aerodynamic pressure and centrifugal force) under working condition on the compressor aerodynamic performance is taken into account by fluid/solid interaction method during the computational fluid dynamics flow field analysis process. In this article, tip clearance flow under the real working environment is investigated with three different tip clearance cases. The impeller deformation combined with the adjustment of tip clearance causes some influence on the aerodynamic performance and on the structure reliability of the compressor system. For the aerodynamic design, an increase in the impeller tip clearance decreases the overall pressure rise and isentropic efficiency of the compressor, mainly due to the tip clearance loss in the impeller. Regarding structure design, the uniform relative tip clearance from the inlet to the outlet CR = 7.3 per cent is changed to non-uniform distribution from 6.4 per cent to 4.15 per cent. The largest deformation location occurs at the blade inducer and trailing-edge tip. The relative clearance near the outlet of the blade is reduced about 3.15 per cent which will cause great influence on the impeller working reliability.

Losses and blade tip clearance for a centrifugal compressor

“…The trend in developing these new turbo shaft engines is to increase specific power with decreasing weight and volume. Another highly studied issue in recent years regarding the centrifugal compressor impeller is the influence of the tip clearance on the performance of the compressor [14]. It has been noticed that aerodynamics of the tip clearance plays an important role in the development of a centrifugal compressor and will have an important significance for the new engine models.…”

A numerical approach for predicting flow-induced acoustics at near-stall conditions in an automotive turbocharger compressor

“…Measurements performed by Wang et al [76] indicated that variations of tip clearance caused small influence on stall inception. However, the reasons could not be investigated because their mixing-plane, steady simulations failed to converge at near surge conditions.…”

“…Wang et al [76] used a two-step calculation procedure to take into account impeller deformation when simulating centrifugal compressor flow, avoiding a two-way coupled fluid-structure simulation. First, the deformation of the compressor blades were simulated with finite element method (FEM).…”

“…Deformation due to thermal and pressure loads and centrifugal forces can be taken into account with a one-way fluid-mechanical simulation. If noise is highly dependent on TCR, the flow field should be recalculated with the actual tip clearance geometry, following the approach of Wang et al [76].…”

“…Pressure deformation was not considered because its contribution to impeller deformation is marginal [76]. Selection of mean value instead of temperature distribution is justified by high thermal diffusivity of aluminum, which is the material of most compressor wheels [78].…”