# Improving the Design of a Multi-Gear Pump Switchgear Using CFD Analysis
## 3 Results
Some liquid particles that move to the common cavity and flow around the inner surface also have the highest values (marked in red). When entering the common pressure tube with a larger diameter, the liquid acquires lower values of the speed of 6-7 m/s. Blue indicates the areas where the particles have velocities close to zero and do not participate in the energy conversion process in any way. This is due to the peculiarities of the collector's design. Figure 10 shows the results of the calculation of numerical experiments in SolidWorks according to the initial data of Tables 3 and 4. The results represent the graphical dependencies of the liquid velocity and pressure drop in the suction lines (Figure 10a) and pressure lines (Figure 10b) of the collector from changes in the liquid flow rate Q in the range from 0.00182 to 0.0055 m\({}^{3}\)/s, pressure in suction lines Ps (from 0.3 MPa to 1 MPa) and pressure lines P\({}_{\text{P}}\) (from 6 MPa to 24 MPa), and the dynamic viscosity coefficient \(\upmu\) in the range from 0.00861 to 8.2 Pa\(\cdot\)s.  
Figure 9: Schematic of the velocity change in the pressure line. An analysis of the obtained data allowed us to reveal some dependencies. With an increase in the liquid flow rate caused by a change in the driving gear rotation speed, the pressure drop \(\Delta\)P in the suction line (curve 1, Figure 10a) increases linearly from 0.066 to 0.35 MPa, and liquid velocity (curve 4, Figure 10a) increases with decreasing intensity from 1.67 to 6.03 m/s. In the header line, an increase in flow rate results in a linear increase in fluid velocity from 3.42 to 9.92 m/s (curve 4, Figure 10b). The pressure drop increases in direct proportion to the flow rate in the range of 0.093 to 0.401 MPa (curve 1, Figure 10b). The increase in the dynamic viscosity coefficient causes an increase in friction between the liquid layers and the internal walls of the collector, and as a consequence, the pressure drop in the lines increases from 0.42 to 1.65 MPa (curve 2, Figure 10a) and from 0.419 to 3.415 MPa (curve 2, Figure 10b), respectively. The fluid velocity in the suction line decreases from 4.33 to 3.21 m/s (curve 5, Figure 10a), and in the pressure line, it decreases from 9.11 to 6.73 m/s (curve 5, Figure 10b). It should be noted here that it is necessary to increase the pressure in the suction line in the case of liquids with viscosities of 0.0173 Pa-s or more. Increasing pressure in the suction line has no effect on the investigated parameters of the liquid flow (curves 3 and 6, Figure 10a). The liquid velocity is \(\sim\)4 m/s, and the pressure drop is \(\sim\)0.423 MPa. As the calculation results show, to ensure the operability of the multistage pump, the pressure in the suction line should not be less than 0.5 MPa at n = 1000 rpm, which will eliminate the cavitation and violation of the continuity of liquid flow. The change in pressure in the pressure line has an insignificant influence on the parameters sought. The pressure drop was 0.33 MPa, and the liquid velocity in the outlet pipe was 8.81 m/s (curves 3 and 6, Figure 10b). Figure 10: Velocity \(v\) and pressure drop \(\Delta\)P in the suction lines (**a**) and pressure (**b**) of the distribution system of a multi-gear pump: 1—dependence of pressure drop on fluid flow \(\Delta\)P = f(Q); 2—dependence of pressure drop on dynamic viscosity coefficient \(\Delta\)P = f(u); 3—dependence of pressure drop on suction pressure \(\Delta\)P = f(P\({}_{\rm s}\))/discharge pressure \(\Delta\)P = f(P\({}_{\rm p}\)); 4—dependence of fluid velocity on flow rate \(v\) = f(Q); 5—dependence of fluid velocity on the coefficient of dynamic viscosity \(v\) = f(u); 6—dependence of fluid speed on suction pressure \(v\) = f(P\({}_{\rm s}\))/discharge pressure \(v\) = f(P\({}_{\rm p}\)).