Combination of Turbocharger and Industrial Technologies for the Development of an Improved Mixed-Flow Turbine Design

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Abstract A new mixed-flow radial turbine design for industrial applications was developed and experimentally investigated. The presented mixed-flow turbine recovers energy in industrial processes, which have unused pressurized, hot off-gas available. The design parameter values are very similar to the ones of mixed-flow turbines for turbocharger applications. Consequently, a turbocharger design was used as starting basis. The mechanical requirements of the industrial application are less challenging for the turbine design. It was possible to extend the design space of the blades far beyond the typical radial fiber constraint, which is usually used to fulfill the mechanical restrictions. This gives more freedom for the parameters used in the blade geometry generation. The final design has an increased efficiency and operating range. In addition to a maximized design point efficiency, a wide operating range is one of the major requirements concerning the turbine performance. During the development process of the radial turbine’s wheel, an automated optimization was used. Due to the competitive design targets, multiple objectives and constrains were formulated. To satisfy the off-design efficiency requirements, each geometry was analyzed by means of six operating points. The mechanical integrity was checked by directly coupled FE simulations. The final design is further investigated and the reasons for the gained improvements are discussed. An experimental investigation of a prototype confirmed the numerically predicted improvements. A comparison of the measurements and the numerical results are shown. The objective of the paper is to show the possible potentials in efficiency and operating range of radial turbines with low mechanical restrictions. In many energy recovery applications, the operating conditions are well known and within clearly defined boundaries. For these applications, it is possible to engineer mixed-flow turbines primarily from the aerodynamical point of view ans secondly from the mechanical one. In the following described work, it was possible, starting from a good turbocharger design, to increase the turbine’s performance. An automatic multi-point and multi-physics optimization was set up to reach the performance improvements.