Impeller Cavity Research Articles

A novel design of impeller cavity pre-swirl system for efficient supercharging and low power consumption

Abstract A design for a turbine pre-swirl system with impeller cavity is proposed to improve the quality of cooling air supplied to the turbine blades of an aeroengine. Impeller cavity is analyzed in order to increase the system pressure ratio with a low system power consumption at the system outlet. Theoretical and numerical investigation are used to investigate the flow characteristics in an impeller cavity pre-swirl system. The conclusions in this study indicate that the impeller structure can increases the pressure ratio by changing the power consumption and distribution of the absolute velocity in the impeller cavity and system outlet. To obtain high pressure ratio and low power consumption, the impeller should have a structure with a high outlet installation radius and low outlet angle. The highest increase in the pressure ratio compared with the empty cavity pre-swirl system is 6.4% and the corresponding increase in the power consumption is 2620 W.

Numeric flow simulation for an innovative ventricular assist system secondary impeller.

The secondary impeller of the Cleveland Clinic Foundation Innovative Ventricular Assist System heart pump is designed to pump the blood from the journal bearing through the annulus back to the discharge to rejoin the main flow. It is crucial, however, that the amount of hemolysis and potential for thrombus formation is minimized. Based on our earlier computational fluid analysis of the initial design, an improved secondary impeller has been proposed. The objective of this work was to analyze the flow with the new impeller configuration by computational fluid dynamics and to find out where in the geometry hemolysis becomes high, as well as where the potential for thrombosis exists. The present work includes: 1) visualizing the 3-dimensional flow pattern in the secondary impeller cavity, 2) investigating the tip clearance effect, and 3) estimating the shear stress distribution as a measure for blood damage caused in the secondary impeller cavity.

Blood Flow Analysis for the Secondary Impeller of an IVAS Heart Pump

The rotodynamic heart pump (IVAS), designed by the Cleveland Clinic Foundation, includes a secondary flow path along the journal bearing, through a secondary impeller, and over the rotor outer surface. The flow behaviors of the blood through the journal bearing and the secondary impeller are investigated by a computational fluid dynamics method that solves the 3-dimensional Navier-Stokes equations using a new solution algorithm. Results of the analyses include: 1) the blood flow patterns within the journal bearing, 2) the effect of the non-uniform bearing clearance on the flow patterns of the impeller cavity, 3) the flow patterns around a secondary impeller blade that include effects of tip clearance and the gap between the blade and the inner or outer side wall, 4) effects of the blade angles on the secondary impeller performance, and 5) the shear stress distribution.

An Analysis Methodology for Internal Swirling Flow Systems With a Rotating Wall

This paper presents an analysis methodology for the calculation of the flow through internal flow components with a rotating wall such as annular seals, impeller cavities, and enclosed rotating disks. These flow systems are standard components in gas turbines and cryogenic engines and are characterized by subsonic viscous flow and elliptic pressure effects. The Reynolds-averaged Navier-Stokes equations for turbulent flow are used to model swirling axisymmetric flow. Bulk-flow or velocity profile assumptions aren’t required. Turbulence transport is assumed to be governed by the standard two-equation high Reynolds number turbulence model. A low Reynolds number turbulence model is also used for comparison purposes. The high Reynolds number turbulence model is found to be more practical. A novel treatment of the radial/swirl equation source terms is developed and used to provide enhanced convergence. Homogeneous wall roughness effects are accounted for. To verify the analysis methodology, the flow through Yamada seals, an enclosed rotating disk, and a rotating disk in a housing with throughflow are calculated. The calculation results are compared to experimental data. The calculated results show good agreement with the experimental results.

Gas recirculation rate through impeller cavities and surface aeration in sparged agitated vessels

A novel method for determining gas recirculation rates through impeller cavities in sparged agitated vessels is described. It is based on the withdrawal, particularly from the cavities themselves, of gas samples forsubsequent analysis. Oxygen is used as the tracer gas and nitrogen for sparging. The method can also be used for determining surface aeration rates. The method gives values for the external distribution coefficient α (=Q R/Q S) of between 0 and 1. These values agree well with those calculated from power measurements at high impeller speeds N > N R. However, the method also suggests that recirculation occurs at N < N R but in this region the method is not entirely valid. The measurements of surface aeration clearly show that attempts to relate the effect of surface aeration without sparging to the sparged condition are unsatisfactory.