City Research Online

Abstract

This study investigates dual-spiral-pitch nozzles, which are essential for high-discharge applications like deluge fire suppression systems (5–4000 L/min). Such nozzles produce multi-sprays, which have received little attention in the past. In the present research, experiments quantified the relationship between inlet pressure (0.2–3.4 bar), mass flow rate, and spray characteristics. Results reveal three distinct spray morphologies linked to inlet pressure: a gradual mass flow rate increase across 0.2–1 bar inlet pressure, a dramatic surge exceeding 1000% between 1 and 3 bar, and an approach to hydraulic saturation (maximum achievable flow) at 3.4 bar, due to geometric constraints. In addition, the results indicated that at 0.2 bar inlet pressure, the nozzle produces single, coarse droplets. As pressure increases to 1.6 bar and above, the spray pattern evolves into two distinct, separate jets: an outer spray (Spray 1) and an inner spray (Spray 2). While increasing the inlet pressure from 1.6 to 3.4 bar causes the outer spray cone angle to expand significantly (from 64° to 121°), the inner spray cone angle remains remarkably stable at approximately 30°. These experimental findings can be used to rigorously verify the accuracy of the corresponding CFD simulations, providing necessary experimental validation for the models.

Publication Type:	Article
Additional Information:	This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Publisher Keywords:	Experimental test, Mass flow rate, Spiral nozzle, Spray cone angle, Two spiral pitches
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology School of Science & Technology > Department of Engineering
SWORD Depositor:	Symplectic Administrator

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