Contra-rotating open rotors (CRORs) show promise for use in future aircraft, but suffer from high noise emission levels. Analytic models for CROR noise prediction exist, but they make fundamental assumptions which are being examined in the current work. Geometry changes are shown to have significant effects on radiated noise, and corrections for this effect should be included in future models.
There is an ever-growing need to reduce the impact of aircraft operations on the environment. This can been seen in various efforts and requirements to reduce fuel consumption, emissions and noise generation. An example of such requirements can be seen as those set out by Advisory Council for Aeronautics Research in Europe (ACARE), which call for significant reductions in carbon dioxide, nitrogen oxides and a reduction in perceived aircraft noise of 50% by 2020, against 2010 baseline values.
The use of CRORs is one of the most promising technological strategies to meet environmental requirements. Propeller based engines have long been recognised as likely to provide more efficient propulsion than future turbofans since they exert a relatively small force on a large mass of air, and CRORs can provide additional efficiency in similar performance ranges such as 0.7 < M < 0.8.
Results show that geometric effects have a significant impact on leading edge gust interaction noise. Therefore future analytic solutions would benefit from scaling laws to account for these effects.