Numerical analysis of small scale axial and radial turbines for solar powered Brayton cycle application

In the current work two types of turbines, axial and radial turbine, with their three configurations, Single Stage Axial, Dual Stage Axial and Single Stage Radial turbines, for solar Brayton cycle applications have been parametrically investigated with the aim of figuring out their performance in terms of efficiency and power output. The mean line design for each turbine was effectively completed in order to figure out the initial guess for the dimensions, the power output and the efficiency. Consequently, the Computational Fluid Dimension CFD analysis was employed for the sake of visualising the 3-Dimentions behaviour of the fluid inside the turbine as well as determining the main output like the power output and the efficiency at different boundary conditions. These boundary conditions were selected to be compatible with a small scale solar powered Brayton cycle. An evaluation for some types of losses such as tip clearance and trailing edge losses as well as the total loss coefficient of the rotor of each configuration, in terms of pressure losses, has been established as well. The current paper deals with Small Scale Turbines SST ranged from 5 to 50 kW as a power output. The outcomes showed that the Dual stage axial turbine performances better at the off design conditions. By contrast, the single stage radial turbine achieved higher power output during the same operating conditions. The results of the CFD analysis have been successfully validated against the experimental work done by the researchers for small scale (axial) compressed air turbine in the lab

Stress analysis and aerodynamic optimization of small-scale compressed air turbines

This study aims to enhance the performance of the solar heater, consisting of parabolic dish concentrator and thermal receiver, as well as the expander, Small Scale Turbines SSTs. Using an advance ray tracing technique, OptisWorks software, both; a small scale parabolic dish concentrator and thermal cavity receiver were developed and optically enhanced. Simultaneously, small scale axial and radial turbines were developed using meanline approach and 3D CFD modelling using ANSYS CFX software. Then, the stator and the rotor of the SSRT were parametrized using two optimization techniques of multi-objective Genetic Algorithm optimization. To examine the SSRT mechanical design reliability, finite element analysis was utilised to determine the values and the locations of each; stresses, deflection and minimum allowed cycle number for the rotor. Consequently, to reduce the Von Mises stresses and deflections and increase the minimum number of cycles on both the rotor shaft and blades, multidisciplinary optimization was conducted to ensure better structural performance without influencing its aerodynamic performance. Comparing numerical and experimental, results showed that the maximum deviation in predicting the compressed air outlet temperature for the thermal receiver was less than 5%. Also, the deviation in SSRT efficiency and power output were about 16% and 14% respectively