Daniel Redmann

Engineering Approach for a Simplified Description of Rotor-Rotor Interaction Noise of a CROR Configuration

A simplified model for the principle description of the rotor-rotor interaction noise at counter rotating open rotors (CROR) was established. A numerical tool for the evaluation and fast performing parameter studies of different CROR configurations was created and results are shown for a generic rotor system and fuselage.

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.