Development of a Propeller Source Noise Model

Turboprop engines are known for their high fuel efficiency on short-range missions compared to turbofan engines. A disadvantage of turboprop engines is the noise they produce. The dominant noise source of the turboprop engine is the propeller. The goal of this research is to develop a propeller source noise model which has the future goal to extend already existing noise prediction tools like the VCNS (Virtual Community Noise Simulator). In this research the Helicoidal Surface theory is coupled with two external aerodynamic tools, XFoil and XRotor, for the computation of the harmonic noise sources of the propeller. The developed tool is called the HeliX-tool. The harmonic noise sources that are implemented for the computation of the propeller noise are the steady loading noise and the thickness noise. The HeliX-tool is successfully implemented in Matlab and the tool is validated using literature data and two NLR-tools (one for the propeller aerodynamics and one for the propeller acoustics). From the validation some limitations came to light. For operating conditions that result in high local Mach numbers (>0.7 Mach), the HeliX-tool shows bad agreement with the literature data. For lower local Mach numbers the HeliX-tool shows good agreement with literature data and the NLR-tools. Additional comparisons are made using the HeliX-tool and NLR-tools for operating conditions that are not considered in the literature data. The agreement with the NLR-tools is shown by these comparisons. However, for harmonic numbers higher than 1 the difference between the HeliX-tool and NLR-tools becomes more noticeable as the harmonic decay of the HeliX-tool is larger. More research into the higher harmonic numbers can possibly improve the agreement for the higher harmonic numbers. The ultimate aim of the HeliX-tool is to be able to perform a noise simulation of a propeller. Therefore an auralization of a propeller fly-over is performed. Several propagation effects are taken into account. These are the ground reflection, spherical spreading, atmospheric absorption and the Doppler frequency shift. As a result an audible simulation of a propeller fly-over is obtained.Aerospace Engineerin