Abstract
Abstract The article discusses the stress optimisation process of the highly loaded disc of a high-speed radial-axial microturbine. At the design stage, the strength optimisation is vitally important for these types of devices because they must withstand very high temperatures (600∘C in this case) and be capable of operating at high rotational speeds (96,000 rpm in this case). Calculations were made using a three dimensional FE numerical model. The optimisation process is strictly connected with the choice of materials — which in this case are Inconel 738 (nickel-cobalt super alloy) and silicon nitride. Several stress reduction methods were developed, which took into account the mass of the disc, the rotational speed of the rotor and the complex shape of the rear part of the disc. Numerical computations helped to choose the best optimisation method, which decreased maximum reduced von Mises stresses by about 45% (from 1,288 MPa to 705 MPa). The methods proposed in this article are universal and can be implemented in the design process of various high-speed radial-axial microturbines. This article could be of interest to scientists and engineers who deal with highly loaded microturbines, which are increasingly used in many industrial sectors.
Highlights
People with basic technical knowledge are aware of the existence of fluid-flow machines such as gas turbines
Not everybody knows that gas turbines play a remarkably significant role in distributed power engineering and CHP (Combined Heat and Power) systems, which have become increasingly popular in recent years [1, 2]
This paper focuses on developing a method for designing the discs of radial gas microturbines, which can withstand very high temperatures and high rotational speeds without any changes in their aerodynamics
Summary
People with basic technical knowledge are aware of the existence of fluid-flow machines such as gas turbines. There are described, among other things, radial-flow microturbines with power capacities of about 3 kW, which operate in ORC systems using waste heat, with a temperature not exceeding 160∘C and pressure at the turbine inlet of 11 bar. This paper focuses on developing a method for designing the discs of radial gas microturbines, which can withstand very high temperatures and high rotational speeds without any changes in their aerodynamics. To develop this method, general information about strength calculations was provided to understand the importance of certain parameters. All the changes had no effect on the turbine fluid-flow system and their relevance was confirmed by FEM calculations
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