Advanced analysis of fan noise measurements supported by theoretical source models

Abstract

With the objective to improve the understanding of the dominant fan noise source mechanisms, a comprehensive experimental study was conducted at a low speed fan test rig. The aerodynamic fan map as well as the acoustic characteristics of the fan was measured for a new blade integrated disk (Blisk) rotor with systematic variation of the shaft speed and throttling. The interpretation of the results is supported by simulations of the experiment with a physics-based analytical in-house tool for fan noise prediction. For the acoustic measurements, an array of wall-flushed microphones was used in the inlet section. By means of radial mode analysis techniques, the broadband and tonal sound powers are calculated for each operating point. In the obtained comprehensive database, systematic variations of the tonal and broadband sound power with the flow rate are found. These patterns can only partly be correlated to the varying incidence angle of the rotor blades. Comparing the mode distributions of the measured noise and the analytical models then allows conclusions on the predominant noise sources of rotor–stator interaction and inflow-rotor interaction.

Development and Application of Smart Home Energy Management System Based on Wireless Network Technology

“…The basic standards for preliminary preparation are relatively complete, the main equipment products and service standards are almost covered, the standard technology level is steadily increasing, the standard application scope is constantly expanding, and it is a good situation to keep pace with the international advanced standard level [4]. The issuance of this guide may open up a huge multitrillion smart home market.…”

Phased array microphone measurement of a ducted low-speed axial flow fan at various operating points with the involvement of the acoustically transparent duct technique

“…For this reason, previous research often applied microphones placed in the flow and wall-mounted microphones to investigate ducted turbomachines. 18,20,22,23 The wall-mounted microphones are unfavorable since they measure the hydrodynamic pressure fluctuations as well as the turbulent boundary layer background noise generated on the solid walls. Additionally, if not installed perfectly flush with the circular air duct, the wall-mounted microphones may influence the local flow, which generates flow-induced self-noise, thus further reducing the signal-to-noise ratio.…”