Radial turbine preliminary design and performance prediction

Abstract

This work will present a model for the preliminary optimized design of a radial turbine and an analysis of the most relevant loss models for efficiency prediction.A one-dimensional code, Radial Turbine Global Design, was developed in MATLAB environment. The model developed has the objective to estimate the efficiency and optimization of the parameters related to it, and losses prediction.The flow that through a turbine is complex and many mechanisms of the flow losses in turbine, have not be known well. The computational fluid dynamics CFD simulations is based on complex three-dimensional viscous methods, which require considerable iterations and, therefore time, in order to obtain an improvement of the geometry, through the convergence to an acceptable solution often not optimal. While, can be used of one-dimensional models able to predict the global design of the machine based on the combination of empirical and experimental loss models, able to provide a good performance estimate with reduced times. In this work, the loss models are analyzed and developed to obtain useful thermodynamic and geometrical information, necessary for an optimization CFD simulation.The RTGD has proven useful for the geometric design three-dimensional of the rotor blades and was tested by considering literature data of real radial turbines that use both Aria and Argon as working fluid, in addition it was compared with the NASA code RIFTUD.The code has excellent reliability because the results obtained reproduce the turbine geometry with a low error compared to the literatures case.Furthermore, RTGD can predict turbine performance through two approaches, the first considering the turbine geometry and the second considering the enthalpy drop due to losses. The second approach for estimating efficiency is necessary in order to confirm the one calculated with the first approach, and therefore the good geometric design of the turbine.The code, after being validated, was used for the radial turbines design for space applications for expander cycle rocket engines which require a high efficiency and a low expansion ratio.