Mean-Line Design of a Supercritical CO2 Micro Axial Turbine

Abstract

Supercritical carbon dioxide (sCO2) power cycles are promising candidates for concentrated-solar power and waste-heat recovery applications, having advantages of compact turbomachinery and high cycle efficiencies at heat-source temperature in the range of 400 to 800 ∘C. However, for distributed-scale systems (0.1–1.0 MW) the choice of turbomachinery type is unclear. Radial turbines are known to be an effective machine for micro-scale applications. Alternatively, feasible single-stage axial turbine designs could be achieved allowing for better heat transfer control and improved bearing life. Thus, the aim of this study is to investigate the design of a single-stage 100 kW sCO2 axial turbine through the identification of optimal turbine design parameters from both mechanical and aerodynamic performance perspectives. For this purpose, a preliminary design tool has been developed and refined by accounting for passage losses using loss models that are widely used for the design of turbomachinery operating with fluids such as air or steam. The designs were assessed for a turbine that runs at inlet conditions of 923 K, 170 bar, expansion ratio of 3 and shaft speeds of 150k, 200k and 250k RPM respectively. It was found that feasible single-stage designs could be achieved if the turbine is designed with a high loading coefficient and low flow coefficient. Moreover, a turbine with the lowest degree of reaction, over a specified range from 0 to 0.5, was found to achieve the highest efficiency and highest inlet rotor angles.

A review of research on turbines for supercritical carbon dioxide power systems

“…The efficiency of the partial intake turbine is reduced by 15% compared to that under full admission. Salah et al developed and improved a preliminary design tool which is able to calculate passage losses by using loss models, in order to design a 100kW S-CO2 axial turbine [51]. A feasible single stage design can be achieved while the turbine has a high load coefficient and a low flow coefficient.…”

Design of a 130 MW Axial Turbine Operating with a Supercritical Carbon Dioxide Mixture for the SCARABEUS Project

“…An in-house mean line design tool is used to develop the turbine flow path [24,25]. Within the tool, the steady-state mass, energy, and momentum equations are solved to obtain the blade geometry, velocity triangles, and thermodynamic properties for all turbine stages.…”

Integrated Aerodynamic and Structural Blade Shape Optimization of Axial Turbines Operating With Supercritical Carbon Dioxide Blended With Dopants

“…The blade shape optimisation process is reported in Figure 1 and is constructed from a numerical model composed of an aerodynamic solver (CFD), a mechanical solver (FEA), a design of experiments (DoE) algorithm, a surrogate model, and an optimisation solver. The baseline blade geometry is created using a mean-line design model [27] that is developed for the SCARABEUS project [28] to design a large-scale blended sCO2 turbine using Aungier [29] loss model. Geometrical parameters including the number of stages, hub diameter, blade height, blade inlet/outlet angles, stagger angle, chord length, number of blades and trailing edge (TE) thickness are used to create the 3D blade along with assumptions defining the inlet/outlet wedge angles, leading edge (LE) thickness and control points defining thickness distribution of the aerofoil.…”