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Radial Inflow Turbines
Published in Ahmed F. El-Sayed, Aircraft Propulsion and Gas Turbine Engines, 2017
The characteristics that make radial turbines desirable areHigh efficiencyEase of manufactureSturdy constructionHigh reliabilityRadial turbines are similar to centrifugal compressors as in both fluid enters and leave in two perpendicular directions. For radial turbines, the flow enters radially and leaves axially close to the axis of rotation. This turning of the flow takes place in the rotor passage, which is relatively long and narrow. Figure 15.1 illustrates a radial inflow turbine.
A comprehensive review on organic Rankine cycle systems used as waste heat recovery technologies for marine applications
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Olgun Konur, C. Ozgur Colpan, Omur Y. Saatcioglu
The working principle of turbo-expanders is based on the rotation of turbine blades, while the high-pressure working fluid in the gaseous-phase expands and transfers its kinetic energy to the turbine blades through its way on the expander. Turbo-expanders can be categorized as axial and radial turbines following the different flow directions of the working fluid at the turbine inlet in relation to the output shaft. Both turbine types have the advantage of a compact structure with lightweight construction. However, in addition to the efficiency drops in unsteady operations, wet expansion is another major challenge on turbo-expanders because liquid formations may easily damage the turbine blades (Pantano and Capata 2017; Talluri et al. 2020). Axial turbine blades are not appropriate for operations with low mass flow rates and high-pressure ratios because the leakages from the small tip clearance between the turbine casing and the blades increase and cause a significant drop in the expander efficiency (Alshammari, Usman, and Pesyridis 2018). Therefore, axial turbine arrangements are well suited to large-scale applications of over 500 kW with a low-pressure ratio and high mass flow rate. Unlike axial turbines, radial turbines can effectively handle the required enthalpy drop in a single-stage expansion process at operations with lower mass flow rates and high-pressure ratios. They are also advantageous in high-density working fluids because of the robust turbine blade design that can support high loads on the blades. Radial turbines are predominantly preferred in medium-scale applications ranging from 30 to 500 kW power output capacity. The economic viability and high-efficiency values achieved in high power outputs start reducing below this range, since micro-scale (<10 kW) turbo-expander arrangements have not been well developed yet (Alshammari, Usman, and Pesyridis 2018; Talluri et al. 2020).