Mixed-flow Turbomachines Research Articles

A compressible three‐dimensional design method for radial and mixed flow turbomachinery blades

AbstractA fully three‐dimensional compressible inverse design method for the design of radial and mixed flow turbomachines is described. In this method the distribution of the circumferentially averaged swirl velocity rVθ on the meridional geometry of the impeller is prescribed and the corresponding blade shape is computed iteratively. Two approaches are presented for solving the compressible flow problem. In the approximate approach the pitchwise variation in density is neglected and as a result the algorithm is simple and efficient. In the exact approach the velocities and density are computed throughout the three‐dimensional flow field by employing a fast fourier transform in the tangential direction. The results of the approximate and exact approach are compared for the case of a high‐speed (subsonic) radial‐inflow turbine and it is shown that the difference between the blade shapes computed by the two methods is well within the manufacturing tolerances. The method was validated by calculating the flow through a designed high‐speed radial‐inflow turbine by using a three‐dimensional inviscid Euler solver. Very good correlation was obtained between the specified and computed rVθ‐distributions.

Families of variational principles for inverse and H A hybrid problems of an S 2 stream sheet in mixed flow turbomachines

This paper deals with the semi-inverse, H A, and inverse problems of compressible flow along an S 2 stream sheet in mixed flow turbomachines, for which families of variational principles (VPs) are derived. In the VPs for the semi-inverse problem, the distributed gas injection and/or suction along the hub walls and casing walls are accounted for. VP families for axial and radial flow turbomachines can be obtained directly from this paper as special cases. Great attention is paid to taking full advantage of natural boundary conditions and “artificial interfaces” in order to offer a perfect theoretical basis for the finite element method or other direct variational methods in computational aerodynamics of turbomachinery. This theory also provides broader and versatile ways for blading design.

Analysis of the through-flow relative eddy of mixed-flow turbomachines

Turbomachine rotors viewed relative to rotation experience a relative eddy. The relative eddy component normal to the blade to blade flow, responsible for slip and for coriolis blade forces in mixed-flow turbomachines, is well known. The remaining eddy component which lies in the through-flow direction, is generally ignored in quasi-two-dimensional design methods. This paper presents the first stage of an analytical method for predicting the influence of the through-flow eddy in axial, mixed-flow or radial machines.

Closure to “Discussion of ‘Three-Dimensional Theory of Incompressible and Inviscid Flow Through Mixed Flow Turbomachines’” (1965, ASME J. Eng. Power, 87, pp. 372–373)

Closure to “Discussion of ‘Three-Dimensional Theory of Incompressible and Inviscid Flow Through Mixed Flow Turbomachines’” (1965, ASME J. Eng. Power, 87, pp. 372–373)

Paper 29: The Mechanism of Relative Eddy Flows in Mixed-Flow Turbo-Machines

In mixed-flow turbo-machines the energy transfer results partly from fluid deflection and partly from Coriolis forces due to the radial motion. The relative motion produces another effect not occurring in axial machines, namely that of slip or relative eddy. In this paper a conformai transformation theory is developed for radial bladed conical flow machines along similar lines to that of Busemann. The flow is regarded as the superposition of source/vortex prewhirl flow and a blade lifting vortex. The lift components due to Coriolis forces and deflection are thus separable. The theory also permits the calculation of surface velocities and streamlines. The main intention is to provide an exact theory for comparison with the extended Schlichting analysis of Pollard.

A Theory of the Direct and Inverse Problems of Compressible Flow Past Cascade of Arbitrary Airfoils

A Theory of the Direct and Inverse Problems of Compressible Flow Past Cascade of Arbitrary Airfoils