# Analysis of Flow Field Characteristics in the Three-Phase Jet Fire Monitor Head
## 1 Introduction  
Fire is one of the major disasters that threaten public safety and cause significant property damage [1]; urban fires alone result in over 3 million deaths globally each year [2]. As a crucial firefighting apparatus, the performance of fire monitors directly affects firefighting efficiency and firefighter safety. In recent years, three-phase jet fire extinguishing technology has been widely applied in various fields such as forestry and chemical industries due to its high extinguishing efficiency and strong re-ignition resistance. The three-phase jet fire monitor (TPJFM), with its advantages of long range, large water volume, and strong adjustability, has become a research hotspot in the firefighting field. The internal flow field (IFF) is the key component of the TPJFM, converting the pressure energy of the water or other extinguishing agents into jet kinetic energy. The TPJFM typically consists of water, compressed air, and powdered extinguishing agents. The powder pipe is inserted into the center of the IFF, with compressed air propelling the powder out, and water being ejected in an annular shape to envelop the air and powder, carrying them to the fire source. Compared to traditional fire monitors, its complex IFF structure significantly affects the flow characteristics, thereby determining the performance of the TPJFM. [PERSON] et al. [3] used Fluent software for the numerical simulation of nozzles on fire trucks, analyzing performance indicators such as flow rate and velocity for different nozzle structures, revealing the impact of various nozzle designs on water jet performance. [PERSON] et al. [4] conducted finite element analysis on nozzle selection based on high-pressure water jet technology, studying the effects of different nozzle structures on jet performance. [PERSON] et al. [5] investigated the structure and hydraulic performance of typical straight nozzles, revealing the internal flow characteristics. [PERSON] et al. [6] conducted structuraloptimization and numerical simulation studies on high-pressure water jet nozzles, proposing optimized design schemes and verifying their effectiveness. [PERSON] et al. [7] analyzed the structural strength and stability of liquid nitrogen fire monitors using computational fluid dynamics (CFD) methods and improved performance and efficiency through optimized structural design, demonstrating that numerical simulation can effectively guide structural optimization. Additionally, other studies have shown the importance of CFD methods in understanding and optimizing the IFF of fire monitors. [PERSON] et al. [8; 9] used CFD simulations to study the detailed effects of jet angle, velocity, and flow rate on the dynamic behavior of jet systems, finding that jet angle significantly impacts system stability. These studies have revealed the complex dynamic behavior within the flow field, providing a theoretical basis for further optimization design. [PERSON] et al. [10] investigated the internal shape design of fire nozzles to reduce recoil force, with the optimized design significantly improving jet performance. [PERSON] et al. [11] studied optimization schemes for liquid fire monitors with self-swing devices through simulation and experiments, with optimized designs significantly improving jet characteristics. [PERSON] et al. [12] analyzed the jet characteristics of hydraulic fire monitors with self-swing mechanisms using CFD and conducted structural optimization. The optimized design significantly improved jet velocity, angle, and spray patterns. [PERSON] et al. [13] found that the modification of the inner surface of the nozzle can significantly improve the flow performance of the IFF, and then affect the high-pressure wave peak of the outer jet. [PERSON] et al.