A New Concept for the Design of Turbine Diffusers

A new concept for annular diffuser design permits a layout of axial multi–diffusers with the potential to achieve the same pressure rise as single–annular diffusers, but over half the length. This is possible by using the full range of geometrical variability to gain a symmetrical loading for all flow channels. The optimal geometry with respect to the radial splitter position and the diffuser struts indicates strong dependence on the outflow of the leading turbine row, at the same time influencing this outflow by means of sharp wall angles. Moreover, an advantage can be derived from the additive pressure rise of the equalization process behind the diffuser. Therefore, it is no longer appropriate to treat the diffuser as an isolated component in the design process, but also to take into account the whole diffusion system including the turbine, diffuser and ducts. CFD turned out to be an adequate tool for this complex task.