Vacuum Generator Basics

Vacuum generators are now widely used in many industries fields. It plays a huge role in industrial manufacturing. Today, we will introduce the working principle, classification, characteristics, selection of vacuum generators and functions. We hope you can have a general understanding of vacuum generators after reading this article.

Introduction

There are two types of vacuum generators: vacuum pump and vacuum generator. The vacuum pump is a machine that forms a negative pressure at the suction port. The exhaust port is directly connected to the atmosphere, and the pressure ratio between the two ends is very large. A vacuum generator is a pneumatic component that uses the flow of compressed air to form a certain degree of vacuum. Compared with the vacuum pump, it has the advantages of simple structure, small size, light weight, low price, convenient installation, and easy compounding with accessories. The generation and release of vacuum are fast, and it is suitable for intermittent work with small flow rate, which is suitable for dispersed use.

Working principle

A vacuum generator is a new type of high-efficiency, clean, economical, and small vacuum component that uses a positive pressure air source to generate negative pressure. It becomes very easy and convenient to obtain negative pressure in places. Vacuum generators are widely used in industrial automation in the fields of machinery, electronics, packaging, printing, plastics and robotics.

The traditional use of vacuum generators is to cooperate with suction cups for adsorption and handling of various materials, especially suitable for adsorption of fragile, soft, thin non-ferrous, non-metallic materials or spherical objects. In this type of application, a common feature is that the required pumping volume is small. The vacuum degree is not required, and the operation is intermittent. The analysis and study of the suction mechanism of the vacuum generator and the factors affecting its working performance have practical significance for the design and selection of the positive and negative pressure gas paths. Quick and easy automatic selection of vacuum generators is included.

Classification

According to the nozzle outlet Mach number M1 (the ratio of the outlet flow rate to the local sound speed), the vacuum generator can be divided into subsonic nozzle type, sonic nozzle type and supersonic nozzle type. Both subsonic nozzles and sonic nozzles are shrinking nozzles, while the supersonic nozzle type must be a first-shrinking and then expanding nozzle. In order to obtain the maximum suction flow or the highest suction pressure, the vacuum generators are designed as supersonic nozzles.

Features

• The generator has mechanical vacuum switch.
• The vacuum generator has a simple structure and long service life.
• There are chemical-resistant and gas-resistant materials, which can be used in various environments. The vacuum degree produced by the vacuum generator can reach more than 90Kpa, which can be customized and mass produced according to customer requirements.

Selection of vacuum generator

The selection of the vacuum generator should first estimate the suction vacuum flow according to the structure and surface conditions of the adsorption surface. And then select the minimum diameter of the vacuum generator nozzle according to the size of the suction vacuum flow. If the adsorption volume is large and the adsorption speed is fast, the minimum diameter of the nozzle should be larger. The selection of the vacuum generator should reduce its air consumption as much as possible under the premise of meeting the requirements of use, and the air consumption is related to the working pressure of the compressed air. The higher the pressure, the higher the air consumption, but the vacuum will not increase. Therefore, when determining the size of the vacuum degree, attention should be paid to improving the relationship between the working pressure of the system and the air consumption.

Vacuum generator suction technology has been more and more widely used in various fields of industrial automation. It is mainly used to absorb fragile and difficult-to-hold objects to complete operations such as handling, clamping or packaging. At this stage, the commonly used pneumatic vacuum components are vacuum generators. In the vacuum suction process, the system response process can be divided into a vacuum generation stage and a vacuum maintenance stage. Usually, the working time of the vacuum maintenance stage is relatively long.

Performance

The performance of the vacuum generator is related to many factors such as the minimum diameter of the nozzle, the shape of the shrinkage and diffusion pipe, the diameter and its corresponding position and the pressure of the gas source.

• Characteristic analysis of the maximum suction flow qv2max: The ideal qv2max characteristic of the vacuum generator requires that in the common supply pressure range, qv2max is at the maximum value and changes smoothly with the change of P01.
• The length of the diffuser should ensure that the various wave systems at the nozzle outlet are fully developed, so that an approximately uniform flow can be obtained on the cross section of the diffuser outlet. However, if the pipe is too long, the friction loss of the pipe wall increases. Generally, the length of the pipe is 6--10 times the diameter of the pipe, which is more reasonable. In order to reduce the energy loss, an expansion section with an expansion angle of 6°--8° can be added to the outlet of the straight pipe of the diffuser.
• The adsorption response time is related to the volume of the adsorption chamber (including the diffusion chamber, adsorption pipeline and suction cup or closed cabin volume, etc.). And the leakage of the adsorption surface is related to the required pressure at the suction port. For a certain pressure requirement at the suction port, if the volume of the adsorption chamber is smaller, the response time is shorter. If the pressure at the suction port is higher, the adsorption volume is smaller, and the surface leakage is smaller, the adsorption response time is also shorter. If the adsorption volume is large and the adsorption speed is fast, the nozzle diameter of the vacuum generator should be larger.