The vacuum generator is the use of a new, positive pressure air supply to produce negative pressuen v2>>vl, when the V2 increases to a certain value, the P2 will be less than one atmospheric pressure, and then the negative pressure will be generated. Therefore, the negative pressure can be obtained by increasing the velocity of the flow and the suction will be generated by the P1>>P2. Vacuum generator classification According to Maher Ml (the number of nozzle exit velocity and local velocity ratio), vacuum generator can be divided into subsonic nozzle (M1<1), sonic nozzle (Ml=l) and supersonic nozzle (M1>1), Subsonic nozzle and sonic nozzle are convergent, and the supersonic nozzle must be shaped the nozzle expansion contraction (. Laval nozzle). In order to get the maximum inspiratory flow rate or maximum inlet pressure, vacuum generator are designed supersonic nozzle. Suction performance analysis Main performance parameters Air consumption: the flow rate from the nozzle qvl. Inhalation flow: refers to the air flow from the suction port qv2. , when the suction port opens to the atmosphere, the maximum suction flow, known as the maximum suction flow qv2max. Inhalation pressure at the mouth: Pv. , when the suction port is completely closed (such as suction cup suction workpiece), that is, when the suction flow is zero, the minimum pressure in the
