Radial Turbine Global Design for Liquid Rocket Engine Application

Abstract

The present work aims to show a methodology for estimating the compact radial turbine performance prediction for expander cycle rocket engine application, avoiding a detailed fluid dynamics analysis. Radial turbines find nowadays-widespread use in turbochargers for automotive applications, but their use in aerospace applications has not so frequently been reported. This turbine type represents a viable alternative to the axial turbine, used for space engine application, specifically for the required power generation by the turbo pump feed system. In the expander rocket engine, the performance of the impulse turbines and of the velocity compounding of impulse turbines are limited due to the low expansion ratio. Therefore, the use of a radial turbine, which is characterized by a higher efficiency with a low-pressure ratio, would be more suitable for this motor type. The design of a turbomachine system is a very complex engineering operation, which can be looked upon as an iterative procedure made of various steps. 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. Radial Turbine Global Design RTGD is based on 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 code according to the type of fuel, hydrogen, methane or kerosene, determines the optimal velocity triangles, on the mean line, to minimize the overall dimensions, the losses, the flow rate and the pressure ratio, in order to maximize turbine performance for liquid rocket engine application. The model developed have the objective to estimate the efficiency and optimization of the parameters related to it, and losses prediction. In conclusion, the results obtained through simplified models based on engineering methods able to predict the turbomachine main characteristics must not be neglected, because are fundamental nowadays for next analysis detailed of viscous flow phenomena on the blade by CFD simulations, thanks to the modern computers computing power.