Preliminary comparison of the performance of thermodynamic models of the subsonic ejector and turbofan

Abstract

Flow-mixing is common in technological processes and both ejectors and turbofans are able to realize the interaction between flows with different energy potentials. Ejectors have been extensively used and their analytical models have been widely presented. Meanwhile to the best of authors’ knowledge there is a lack of studies exploring efficiencies of turbofans. The goal of this paper is to compare thermodynamic processes in these devices. Their efficiencies are compared in terms of compression and entrainment ratios. A comprehensive one-dimensional subsonic thermodynamic models of the ejector and turbofan are presented. The quantitative indices are obtained for the same initial conditions expressed as the ratio of differences in enthalpies for ideal compression and ideal expansion. When initial conditions are equal to the numeric value of the combination of isentropic efficiency of evaluated components (numerical case 0.16), both devices have the same efficiencies; at lower initial conditions (numerical case 0.10), turbofan’s entrainment ratio is 1.5 times and compression efficiency 1.25 times higher; at higher value of initial conditions (numerical case 0.28) – the ejector is more efficient. Such distinctive characteristics of turbofans and the nature of their variation may correspond to the specific application areas of the technological equipment, which require certain flow mixing parameters.