# Simulation and Experimental Research on the Energy Loss of Confluence Pipelines
## 4 Application  
As shown in Figure 11, the PSP1500 car-mounted fire pump produced by AMPRO is equipped with a standard T-shaped manifold with a diameter of 150 mm. The water pump inlet pipeline is designed with a water inlet at two sides. However, during the performance testing of the vehicle water pump, whether it is a single-sided water inlet or a simultaneous water inlet on both sides, it cannot meet the design requirements of the water pump very well. According to analysis, this is caused by the influence of local resistance on the direction of water inflow. Therefore, the structure of the inlet pipe was changed by using two 90\({}^{\circ}\) curved pipes to connect and form a curved confluence pipe, as shown in Figure 11. Then, when tested again, it could easily meet the design requirements for pump performance flow rate and pressure. The impact of the structure with water inflow on both sides on the performance of the fire truck pump cannot be ignored.  
The application of fire pumps is special. When using fire pumps, due to emergency situations that require additional water intake, the inlet pipeline often adopts a situation where two branches merge to all the water to enter, as shown in the figure. For the situation where two branches of a fire truck merge into the water inlet, reducing the energy loss of the inlet channel can increase the flow rate of the inlet pipe while ensuring that cavitation does not occur, thereby obtaining sufficient fire water flow; secondly, a higher suction height can be achieved at a certain water flow rate without cavitation.  
For a fixed power water pump, the energy loss in the inlet pipeline will equally cause a decrease in pressure in the outlet pipeline or a decrease in the outlet lifting height. The relationship between the head, suction, and energy loss of a pump is shown in the following Equations (18) and (19).  
\[\frac{P_{1}}{\gamma}=H_{p}-H_{0}-\frac{v^{2}}{2g}-H_{s} \tag{18}\]  
\[H_{s}=\frac{\Delta P}{\gamma} \tag{19}\]  
In the formula, \(P_{1}\) is the outlet pressure of the pump, Pa; \(H_{p}\) is the head of the pump, m; \(H_{0}\) is the suction stroke of the pump, m; \(v\) is the outlet flow velocity of the pump, m/s; and \(H_{s}\) is the energy loss of the inlet pipeline, m.  
According to the above relationship, it can be seen that the energy loss of the inlet pipeline of a constant power pump will affect the head height of the pump, and the energy loss saved by the circular arc manifold will increase the lifting height of the pump. In addition, fire trucks often require outdoor water intake, such as shallow river water, lake water, etc. Therefore, if the energy loss of the pump inlet pipeline is effectively reduced, sufficient fire water flow and a greater suction height can be obtained.  
Due to the relationship between the diameter and flow rate of common fire truck inlet pipelines, the flow rate of the DN100 mm inlet pipeline is 15 L/s (54 m\({}^{3}\)/h) and the  
Figure 11: Fire truck water supply pump merging system.  
flow rate of the DN150 mm inlet pipeline is 35 L/s (126 m\({}^{3}\)/h). Based on the relationship between flow rate and pipe diameter, the average flow velocity of the pipeline cross-section can be calculated as m/s and m/s. The minimum cross-sectional area flow velocity m/s is taken for energy loss calculation.  
The calculation results show that compared to T-shaped, Y-shaped, and bifurcated confluence pipes, the application of circular arc confluence pipes in the combined inlet pipeline of fire truck water supply pumps can increase the suction height by about 1.3 m, 0.6 m, and 0.33 m. This is of great significance for improving the on-site performance of fire trucks and enhancing firefighting efficiency.