A Project Study of Open Rotor Noise

Abstract

Open Rotor Noise consists of a number of different noise sources, each of which generates noise over a wide frequency range (one of the main features of contra-rotating turbomachinery). Consequently, parametric studies of relevance to engine and aircraft projects are best conducted over the audible frequency range and appraised in terms of the standard aircraft noise metric of EPNL. In this paper, we undertake a parametric study of open rotor noise in terms of its dependence on both front and rear blade numbers and blade tip speeds. In the first phase of the study blade numbers and tip speeds are varied independently. In the second phase they are varied simultaneously to show the close coupling between the two. The study is based on predictions and, to aid these predictions, extremely fast analytic tools – with some essential simplifications – are used for both the aerodynamics and noise calculations.