# Improving the Design of a Multi-Gear Pump Switchgear Using CFD Analysis
## 1 Introduction  
Gear pumps belong to a separate group of positive displacement pumps [1, 2]. The suction and injection of the working fluid into the hydraulic system from the gear pump are provided due to the variable volume in the low- and high-pressure cavities caused by the entrance and exit of the teeth of the meshing during their rotation [3, 4]. As the gears rotate and the teeth move out of engagement, the volume of the suction side chamber increases, and fluid is drawn due to the pressure difference between the suction inlet and the low-pressure chamber [4]. The liquid that has filled the cavities between the teeth is then carried along the outer arc by the gears in the direction of rotation. When the teeth engage, the volume of the chamber on the discharge side is reduced. Continuously rotating, the gear teeth displace the liquid into the discharge pipe [5, 6]. During the operation, the teeth are tightly adhered to each other, preventing the exit of pumping liquids in the opposite direction [7, 8]. But during operation, friction occurs between the gears [9, 10, 11]. Therefore,gear pumps can only be able to pump products with lubricating properties that do not contain abrasives [12]. To ensure the best suction capacity and to avoid the cavitation of the gear pumps, it is recommended to use underflow gear pumps [13]. Gear pumps are widely used in many industries [3; 14; 15]. Gear pumps have two, three, or more gears [16; 17; 18]. Despite the long history of use, there is not much in the literature on gear pump research and developments. The fluid flow pattern in a gear pump with two gears rotating in opposite directions has been well studied [19; 20; 21; 22; 23]. There are practically no studies for gear pumps with multiple gears. The design of a multiple-pinion pump construction allows us to solve the problems of increasing productivity, reducing the radial forces acting on the gears, and increasing the uniformity of flow when fluid is displaced into the pressure line. To achieve these goals, a multi-gear pump was developed with four driven pinions and one drive pinion, as shown in Figure 1[24]. The multi-gear pump consists of manifold 1 with several connection openings, representing the fluid distribution system. Front cover 1 has five holes: four suction holes and one outlet hole. The manifold is attached to housing 2 using bolted connections. Housing 2 has five holes in which five bearings 3 are installed. Four idler gears 4, as well as a centered master gear 5 with bearings, are installed, meshing with the idler gears. The four idler gears 4 arranged in the chambers are arranged relative to each other in such a way that they do not mesh with each other. Attached to housing 2 is a rear cover 8 with a flange 6, which also has holes for bearings 3. Cover 8 has an opening with an O-ring 7 for drive shaft 5. In this design, due to the four discharge zones, the radial forces acting on the shaft will be balanced. As a result of the fact that the volume of the pump working chamber has increased, the pump capacity will also have higher values. The uniformity of the delivery and the reduction in pressure pulsations are achieved by the fact that the gears engage and disengage with a time offset. In addition, all fluid discharged from the working chambers enters the manifold, where the displaced flows are combined into one. Focused parameter modeling provides information on the details of localized fluid flow, such as flow jets and cavitation formation sites, in addition to predicting basic pressure and flow characteristics throughout the plant [25; 26; 27]. Therefore, fluid flow modeling using CFD analysis was applied to the design of the multi-gear pump. Based on this analysis, decisions were made to select the optimal criteria for the fluid distribution system (manifold) of the multi-gear pump, designed to separate the high- and low-pressure regions and direct the fluid flows.