The performance of the vacuum generator is related to the minimum diameter of the nozzle, the shape of the contraction and diffusion tube, the path and its corresponding position, and the pressure of the air source, etc.. Figure 2 is a vacuum generator inlet pressure, suction flow, the relationship between quantity and supply pressure of air consumption. The diagram shows that the supply pressure reaches a certain value, the inlet pressure is low, then the suction flow rate reaches the maximum, when the supply pressure continues to increase, the inlet pressure increases, then suction flow decreases.
Analysis of characteristics of maximum inspiratory flow qv2max: qv2max characteristics of vacuum generator ideal, in common supply pressure range (P01=0.4---0.5MPa), qv2max is the maximum, and with the change of P01 flat.
Analysis of the characteristics of pressure Pv at the suction port: the ideal Pv characteristics of the vacuum generator require that the Pv is at the minimum in the common supply pressure range (P01=0.4---0.5MPa), and with the change of Pv1, it is gentle.
The noisy completely closed condition in the inlet, on the specific conditions of suction pressure at Pv and relationship between inspiratory flow is shown in Figure 3. The matching relation between the inlet to obtain ideal pressure and suction flow, can be designed into a multi-stage vacuum generators in a series combination.
The length of the diffusion tube should ensure the development of various wave systems at the nozzle exit, and the uniform flow can be obtained at the exit section of the diffusion pipe, but the friction loss of the pipe wall is too long. The general foreman is 6---10 times the diameter is more reasonable. In order to reduce the energy loss, pipe straight pipe in the diffusion outlet expansion section of a divergent angle of 6 DEG ---8 deg.
The adsorption response time is related to the volume of the adsorption chamber (including the diffusion cavity, the adsorption pipeline and the suction cup or the volume of the closed chamber, etc.), and the leakage amount of the adsorbed surface is related to the pressure required at the suction port. Some of the inlet pressure, volume if the adsorption cavity is smaller, shorter response time; if the inlet pressure is higher, the adsorption volume is small, the surface leakage is small, then the response time is short of sorption; if the adsorption volume, and breathed faster, while the diameter of nozzle vacuum the generator should be bigger.
The vacuum generator should reduce the consumption of gas to meet the operation requirements under the premise (L/min), the gas consumption and the compressed air supply pressure, the greater the pressure, the vacuum generator gas consumption is larger. So in determining the inlet pressure service hours on duty should pay attention to the relation between supply and consumption of gas pressure system the general vacuum generator inlet pressure in 20kPa to 10kPa. At this time for the table pressure increase mouth, suction pressure will not decrease, while the gas consumption is increasing. Thus reducing the inlet pressure should consider the velocity control.
Sometimes, due to the effect of the shape of the workpiece or material, it is difficult to obtain low inlet pressure, due to the inhalation of air from the edge of the suction cup or the workpiece, caused by the inlet pressure increases. In this case, you need to choose the right size of the vacuum generator, which can compensate the leakage caused by the inlet the pressure rise. Because it is difficult to know the effective cross-sectional area of the leak, a simple test can be used to determine the pressure rise at the suction port. Because it is difficult to know the effective cross-sectional area of leakage, a simple test can be used to determine the leakage. It is easy to know the size of the leakage by checking the display of the vacuum meter and checking the performance curve of the vacuum generator.
When the leakage is considered, the characteristic curve of the vacuum generator is very important for the correct determination of the vacuum generator. The leakage is sometimes unavoidable. The method of determining the size of the vacuum generator when the leakage occurs is as follows: the nominal suction flow and the leakage flow are added, and the size of the vacuum generator can be detected.