Reinhard Pongratz

An Experimental Study on a Low Noise Blade Concept for CROR

Currently, the counter rotating open rotor (CROR) is one of the most promising and exhaustively investigated propulsion concepts for future commercial aircraft. There exists a big variety of numerical studies, dealing with the fundamental understanding of the noise generation mechanism from CROR configurations. A number of wind tunnel measurements have already been performed, but most of them were used for the validation of numerical methods. The work described in this paper goes beyond by introducing first experimental investigations on low noise CROR blades. The experimental study was performed on a small scale test rig on laboratory level.

Aeroacoustic liner applications of the broadband special acoustic absorber concept

Aircraft exterior noise reduction is a major task for manufacturer and carrier. However, optimum sound absorption over a broad frequency range at engine level is still a challenging aspect for acoustic liner. This paper presents the special acoustic absorber concept as broadband working liner with limited space needed. Experimental as well as numerical work is presented for different applications as there are hot stream liner for exhaust integration, broadband liner for bypass integration and low frequency broadband liner for integration into a shrouded fan.