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.
Highlights
Micro-gas turbines coupled with concentrated-solar power systems (CSP) can provide a viable solution for renewable energy generation
A parametric study is presented to investigate the effect of the flow coefficient (φ), degree of reaction (Λ) and loading coefficient (ψ) on the turbine performance ηtt and design feasibility
This paper has presented the design of a small-scale single-stage 100 kW axial turbine for implementation within a supercritical carbon dioxide power system
Summary
Micro-gas turbines coupled with concentrated-solar power systems (CSP) can provide a viable solution for renewable energy generation. They have been shown to be ideally suited for small-scale standalone and off-grid applications [1]. For a high thermal efficiency, in the range of 40 to 50%, the system needs to operate at high heat-source temperatures, above 600 ◦ C. Cycles operating with supercritical carbon dioxide (sCO2 ) can achieve similar thermal efficiencies at more moderate temperatures. SCO2 can be considered as a potential candidate for concentrated-solar power applications, for stand-alone solar dish units; offering a simple layout, high-power density and compact structures [2]
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