Computational Investigation of Flow Control Methods in the Impeller Rear Cavity

Abstract

In typical median and small aeroengines, the air used to realize the functions such as cooling of turbine blades and disks, sealing of turbine cavities and bearing chambers, adjusting of rotating assembly axial load is normally drawn through the rear cavity of centrifugal impeller, so the thorough understanding of flow characteristics and pressure distribution and the proposal of the corresponding control methods in the cavity are the key to design the rational secondary air system. With an impeller rear cavity in a small turbofan engine as an object, the current study was dedicated to the investigation of flow control methods in the cavity. Two methods, namely, baffle and swirl-controlled orifice, were proposed to regulate the pressure loss and distribution in the cavity. Furthermore, the influence of geometry parameters of the two methods such as the length of baffle, the space between the baffle and rotating disk wall, the orientation, and radial position of swirl-controlled orifice was investigated. The CFD results show that the swirl-controlled orifice which could deswirl the flow is more effective in regulating the pressure loss and its distribution in cavity than baffle. The variation of the radial position of the swirl-controlled orifice had little influence on pressure loss but obvious influence on pressure distribution; therefore, decreasing the radial position could reduce the axial load on the rotating disk without changing the outlet pressure.

Experimental and Numerical Analysis of the Impeller Backside Cavity in a Centrifugal Compressor for CAES

“…Li [11] calculated and analyzed the internal flow field characteristics of the IBC and its influence on the performance of the whole machine. Liu [12] summarized the influence of the change in radial position of the swirl-controlled orifice on the pressure distribution, and the effect of the axial load on the rotating disk under various radial inflow (including Re ω , C w , G, β 0 , λ T , etc.). Qiao [13] and Hazby [14] numerically studied the leakage flow in shroud and hub cavities of a multistage centrifugal compressor.…”