Aerodynamic noise analysis of a portable pneumatic extinguisher

摘要

The portable pneumatic extinguisher is one of the most important pieces of equipment for forest fire fighting in China. However, the working noise of the equipment is detrimental to the physiological and psychological health of people in terms of noise exposure. Few research studies have addressed the noise of portable pneumatic extinguishers. Changes of the geometric parameters of the fan can induce variations in the airflow field, thus modulating the resulting aerodynamic noise. This article describes how certain parameters influence the aerodynamic noise of a portable pneumatic extinguisher; the research object of this study was the 6MF-30 portable pneumatic extinguisher. Based on the literature, three parameters that influence the airflow in the fan were chosen for investigation: the stagger angle, exit installation angle and curvature ratio. Models of the portable pneumatic extinguisher fan were developed using Solid Works, and the values of the geometric parameters were calculated using formulas incorporating trigonometric functions. The noise simulation was conducted via FLUENT based on the FW-H equation, and ten two-dimensional models with different parameters were investigated. The results show that the exit installation angle has essentially no effect on aerodynamic noise. In contrast, the stagger angle and the curvature ratio can have a large influence on aerodynamic noise. The optimal model differs for different frequency bands; for example, at frequencies below 80 Hz, a fan with a stagger angle of 30 degrees exhibits better noise performance, and at frequencies in the range of 80 Hz to 1000 Hz, a fan with a stagger angle of 40 degrees produces lower working noise. The results are clearly different from those of an aerodynamic performance analysis. (C) 2017 Institute of Noise Control Engineering.