# Improving the Design of a Multi-Gear Pump Switchgear Using CFD Analysis
## 3 Results  
Input Data to Estimate Hydraulic Parameters in the Section and Pressure Lines of the Distribution System  
Numerical experiments were performed in SolidWorks Flow Simulation. The main task of the experiments was the study and calculation of the hydraulic parameters of the flow (pressure losses and velocity in the suction and pressure lines) in order to determine the performance of the proposed collector design and operational characteristics of the gear hydraulic machine. The research was carried out in several stages:  
1. The calculation of the suction line of the collector at changes in performance and speed, dynamic viscosity coefficient, and pressure at the inlet of the suction pipe;
2. The calculation of the collector pressure line at changes in productivity and speed, the coefficient of dynamic viscosity, and pressure at the outlet of the discharge pipe. Thus, three series of experiments were conducted with a planning matrix of 2\({}^{3}\). In the first series of experiments (1-8), the number of revolutions per minute n = var, the dynamic viscosity coefficient \(\mu\) = const, and the pressures Ps = const and Pp = const. In the second series of experiments (9-16), n = const, \(\mu\) = var, Ps = const, and Pp = const. In the third series of experiments (17-24), n = const, \(\mu\) = const, Ps = var, and Pp = var. Figure 4: Example of setting the boundary conditions for the suction line: (**a**) input pressure; (**b**) outlet volumetric flow rate. The data input to estimate hydraulic parameters in the suction and pressure lines of the distribution system can be expressed as follows:  
\[\text{q}=4\pi\cdot\text{m}^{2}\cdot\text{b}\cdot\text{z}, \tag{1}\]  
where m is the gear module; b, the gear tooth width; and z, the number of teeth. The working volume of the multiple gear pump was q = 275 cm\({}^{3}\). The data from the experiments in the SolidWorks simulation are presented in Table 3.  
The results can be presented in the form of isosurfaces, cross-sectional, and surface patterns, as well as trajectories characterizing changes in the hydraulic parameters of the flow. The results can be most clearly represented by cross-sectional pictures (Figure 5a) or flow trajectories (Figure 5b). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \begin{tabular}{c} **No. of** \\ **Experience** \\ \end{tabular} & \begin{tabular}{c} **Speed, n, rpm** \\ **Viscosity, \(\mu\), Pa-s** \\ \end{tabular} & \
\begin{tabular}{c} **Coefficient of** \\ **Pressure P\({}_{\text{s}}\), kPa** \\ **Q, m\({}^{3}\)/s** \\ \end{tabular} &
\begin{tabular}{c} **Pump Capacity** \\ **Q, m\({}^{3}\)/s** \\ \end{tabular} \\ \hline \hline \multicolumn{5}{c}{Series \(1\)} \\ \hline  
line \hline \end{tabular}
\end{table} 
Table 3: Variable parameters in modeling fluid flow in the suction line of the distribution system. Investigation of Changes in the Main Hydraulic Parameters of a Pump System in Section and Pressure Lines  
At the inlet of the suction line, the pressure is at its maximum; then, upon entering the four suction ports, the pressure gradually decreases. The fluid loses energy to overcome resistance at the inlet of the orifices and in the orifices themselves (Figure 6). Figure 7 shows the change in flow velocity. At the inlet to the suction connections and in the common cavity of the manifold, the velocity values are minimum. As the liquid flows further into the pump working chamber through the 10 mm diameter holes, the velocity increases. From the velocity distribution diagram, it can be observed that in the center of the orifice cross-sections, the velocity is maximum, and as it moves away from the center to the walls, the velocity decreases as a result of friction between the liquid layers. Figures 6 and 7 show examples of the calculation of liquid flow parameters in the suction line for pressure Ps = 0.8 MPa and liquid flow rate Q = 0.00458 m\({}^{3}\)/s. At the inlet to the suction line, the pressure value is maximum and equal to 0.8 MPa; then, upon entering the four suction openings, the pressure gradually decreases.