Investigation on Thrust and Moment Coefficients of a Centrifugal Turbomachine

Abstract

In radial pumps and turbines, the centrifugal through-flow in both the front and the back chambers is quite common. It strongly impacts the core swirl ratio, pressure distribution, axial thrust and frictional torque. In order to investigate these relationships experimentally, a test rig was designed at the University of Duisburg-Essen and described in this paper. Based on both the experimental and numerical results, correlations are determined to predict the impacts of the centrifugal through-flow on the core swirl ratio, the thrust coefficient and the moment coefficient. Two correlations respectively are determined to associate the core swirl ratio with the local through-flow coefficient for both Batchelor type flow and Stewartson type flow. The correlations describing the thrust coefficient and the moment coefficient in a rotor-stator cavity with centripetal through-flow (Hu et al., 2017) are modified for the case of centrifugal through-flow. The Daily and Nece diagram distinguishing between different flow regimes in rotor-stator cavities is extended with a through-flow coordinate into 3D. The achieved results provide a comprehensive data base which is intended to support the calculation of axial thrust and moment coefficients during the design process of radial pumps and turbines in a more accurate manner.

Axial Thrust, Disk Frictional Losses, and Heat Transfer in a Gas Turbine Disk Cavity

“…The first one, noted as SRSCA, is used to perform the measurements of the pressure, the axial thrust, and the disk frictional losses. A sketch of the longitudinal section of it is depicted in Figure 2a [9,10]. A centrifugal pump system is used to supply the water to the test rig.…”

“…Will et al [7,8] associated the radial pressure distributions with both the tangential and the radial velocities for either Batchelor type or Couette type flow. By numerical simulations, Hu et al [9,10] determined part of the boundaries between the Batchelor type flow and the Couette type flow in a rotor-stator cavity with through-flow. Debuchy et al [11] investigated the flow behavior of the Batchelor type flow.…”

“…The demands for the safe operation and long service life require the precise prediction on the axial thrust. By force measurements, Bo Hu et al [9,10] determined some empirical correlations of the axial thrust coefficient C F , defined in Equation 6, in the side chambers of centrifugal pumps. Kurokawa et al [12,13] studied the variations of C F in the casing of a radial flow turbomachine with leakage flow.…”

“…The values of C F showed little change when the inlet angular momentum of the leakage flow is a constant. The disadvantage of the correlations is that they are only valid for G = {0.018, 0.036, 0.054, 0.072} in [9,10] and G = {0.024, 0.048, 0.097} in [12,13]. The parameter G is the non-dimensional axial gap width, defined in Equation (7).…”

“…Owen et al [4] found the relationship between C M and λ t . Hu et al [9,10] extended part of the Daily&Nece Diagram into three dimensions with a third axis of C w . They also organized two empirical correlations of C M for the two turbulent flow regimes (turbulent flow with either small or large axial gap width).…”