Influence of the Nozzle Contraction Angles of Gaseous Extinguishing Systems on Discharge Noise

Abstract

Fire extinguishing systems are essential equipment in all indoor facilities to address unexpected fire scenarios, and appropriate fire extinguishing agent should be used depending on the place and object to protect. Among these, gaseous fire-extinguishing systems are used to protect electronic equipment. Therefore, inert gases that do not undergo chemical reactions are used mainly in those systems. On the other hand, recently, owing to the high integration of electronic equipment, there are some cases, in which large noise generated from gaseous systems damage the electronic equipment. In this study, numerical analysis of the discharge noise with various nozzle contraction angles was carried out to improve the gas fire extinguishing system. Numerical analysis was carried out using ANSYS FLUENT ver 18.1. The causes of the noise were elucidated using the swirl distribution. The noise level of the modified model was reduced by approximately 6 dB compared to the reference model, which is similar to the result of a previous study, confirming the validity of the method.

Experimental Assessment of the Acoustic Performance of Nozzles Designed for Clean Agent Fire Suppression

“…On the other hand, silent nozzles were employed in the discharge of nitrogen IG100. It is worth clarifying that the tested silent nozzles present a sound-absorbent layer included within their frame, which makes them similar to those investigated in the works by Kim et al [3,13]. Figure 4 presents simplified technical sketches of the employed nozzles, highlighting the orifice diameter.…”

“…As a technical solution to reduce the noise generated by clean agent discharge, silent nozzles-often also referred to as acoustic nozzles-have been developed. Since modifying the nozzle outlet does not appear to fully address the challenge, given that SPL was proven to be largely independent of nozzle shape [7], adding sound absorptive layers to the nozzle outer surface has become the most employed approach [3,12,13], with the insertion of horizontal plates also being recommended to make the released flow rate and pressure as balanced as possible in multiorifice nozzles [12,14]. Currently, the open literature presents relatively few studies that focus on the design of such nozzles and on assessing their acoustic performance, especially when compared with that exhibited by standard nozzles under the same discharge conditions.…”

“…The extensive use of numerical modeling generally permeates the works on silent nozzles, most of which [12,14] are focused on determining the most effective nozzle selection and configuration within an enclosure towards making SPL at the HDD locations lower than the previously mentioned threshold (110-120 dB, in those studies). On the other hand, the more recent contributions by Kim et al [3,13] present a computational approach-remarkably validated through dedicated experiments-to optimize some design parameters of silent nozzles. Guided by DOE (Design of Experiments), their research effort led to them identifying the diameter of the external sound-absorbing shell as the most impactful variable.…”