Rapid Interactive Design-to-Performance of Mixed-Flow Space Inducers

The article illustrates the invited lecture given by the author at International Symposium on Pump and Fan Technology, September 26-28, 2018, ShenYang, China, on the development and experimental validation of a reduced order model for preliminary design and noncavitating performance prediction of mixed-flow tapered-hub inducers for space propulsion applications. The model expresses the 3D incompressible, inviscid, irrotational flow in the blade channels by superposing a 2D axial vorticity correction to a fully-guided axisymmetric flow with radially uniform axial velocity. Suitable redefinition of the diffusion factor for bladings with non-negligible radial flow simultaneously allows for the control of the blade loading and the estimate of the boundary layer blockage and viscous blade losses at the specified design flow coefficient, providing a simple criterion for matching the hub profile to the axial variation of the blade pitch angle. Carter’s rule is employed to account for flow deviation at the inducer trailing edge. Mass continuity, angular momentum conservation and the Euler equation are used to derive a simple 2nd order boundary value problem whose numerical solution defines the far-field axisymmetric flow velocity at the inducer discharge. The noncavitating pumping characteristic is then obtained using suitably adapted semi-empirical corrections for incidence, casing and tip clearance losses. The model has been verified to closely approximate the geometry and noncavitating head characteristics of two space inducers tested in the Cavitating Pump Rotordynamic Test Facility, as well as those of a number of tapered-hub inducers documented in the literature.