Pump of coffee machine

From the understanding of the principle of the pump, the pump can be divided into three types: volumetric pump, power pump and electromagnetic pump.

The volumetric pump is pressurized by changing the volume of the cavity, such as plunger pump, rotary plate pump, gear pump.

Power pump is the impeller rotation work to promote the liquid to boost, such as vane pump, centrifugal pump and so on. An electromagnetic pump is used to transport a good liquid conductor. Volumetric pumps are used in places with high pressure and low flow, such as hydraulic systems. Power pumps are used in places with large flow and low pressure, such as fuel supply lines, or where pre-pressurization is needed. Electromagnetic pumps are generally used to transport liquid metal or blood. So obviously the espresso coffee machine uses a volumetric pump, which is the only way to generate 15bar pressure.

Force.

As for the choice of piston pump or rotary plate pump should be considered from the cost (gear pump has not been used). Usually the plunger pump selected by the domestic machine produces the piston movement by electrifying the solenoid valve repeatedly through the diode half-wave rectifier, so the pressure pulsation is larger. In fact, in the aviation field, if multiple plunger pumps work together to produce high pressure, the fluctuation is much smaller at this time. The professional machine uses a rotary plate pump. The retractable rotary plate rotates at the center of the pump body. The pump is divided into two cavities, and the volume changes as the rotating plate rotates, resulting in high pressure. The pressure fluctuation is obviously much smaller than that of the electromagnetic pump.

As for the ability to stabilize the pressure, it depends on the working curve of the pump. No pump can keep the pressure constant at high flow rates, even in high-end aviation. As mentioned earlier, the pressure stabilizing ability of the professional machine is good, and the pressure rises little after blocking. This is because the pressure relief valve at the pump outlet returns the overpressurized liquid to the inlet of the pump, keeping the pressure stable. The plunger pump of the household machine can also relieve pressure through the relief valve after blocking to keep the pressure stable, which is no different from the former. The relief valve is used to stabilize the pressure, the flow rate is lost, and the energy is not fully utilized. In the aviation field, the pressure is stabilized by changing the inclined plate of the piston pump.