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What are the factors that affect the performance of vacuum generators?

A vacuum generator is a device that uses a positive pressure air source to generate negative pressure, and the following are the main factors that affect its performance:

I. Compressed air supply pressure

 • Principle: The pressure of compressed air is directly related to the ability of the vacuum generator to generate vacuum. According to Bernoulli’s principle, when high-speed airflow passes through the nozzle of a vacuum generator, pressure energy is converted into kinetic energy, forming a low-pressure zone at the outlet. The higher the supply pressure, the faster the airflow velocity, and the higher the vacuum degree generated.

 • Example: If the supply pressure is increased from 0.4MPa to 0.6MPa, the vacuum degree of the vacuum generator may increase from -60kPa to around -80kPa (the specific value varies depending on the generator model and other factors).

II. Structural design of the vacuum generator

1. Nozzle size and shape

 • Principle: The nozzle is a key component of the vacuum generator. A smaller nozzle diameter can allow compressed air to be ejected at a higher speed, which is beneficial for generating a higher vacuum degree, but it will limit the flow rate. A smaller nozzle diameter can allow compressed air to be ejected at a higher speed, which is beneficial for generating a higher vacuum degree, but it will limit the flow rate. The shape of the nozzle also affects the flow characteristics of the airflow, such as the tapered nozzle which can better accelerate the airflow.

 • Example: A vacuum generator using a conical nozzle may produce higher vacuum levels at the same pressure than one using a straight tube nozzle.

2. Diffuser design

 • Principle: The function of the diffuser is to slow down high-speed airflow, convert kinetic energy into pressure energy, and thereby increase vacuum suction. The right diffuser angle and length can optimize this process. 

 • Example: A vacuum generator with an optimized diffuser design can more effectively during suction, and its suction flow rate can be increased by 20% -30% compared to similar products without optimized diffusers.

III. Working environment temperature

 • Principle: Temperature affects the density and viscosity of gases. At low temperatures, the gas density increases and the viscosity decreases, which will reduce the performance of the vacuum generator in generating vacuum. Because an increase in gas density will reduce the mass flow rate at the same pressure, while a decrease in viscosity will reduce the flow resistance of gas inside the pipeline and generator, but the overall effect is a decrease in vacuum degree.

 • Example: At 0 ℃, the vacuum degree of the vacuum generator may decrease by about 10% -15% compared to at 20 ℃.

IV. The condition of the connecting pipeline

1. Pipeline length and diameter

 • Principle: The length and diameter of the pipeline connecting the vacuum generator and the object being sucked have a significant impact on its performance. Longer pipelines will increase the resistance of airflow along the way, causing a decrease in vacuum degree. A smaller diameter of the pipeline will limit the gas flow rate, reduce the response speed and suction capacity of the vacuum generator.

 • Example: If the length of the pipeline is increased from 1m to 3m, the vacuum may drop by 20% – 30%. Similarly, reducing the diameter of the pipeline from 8mm to 6mmmay result in a 30% -40% decrease in suction flow rate.

2. Pipeline sealing

 • Principle: If there is a leak in the pipeline, outside air will enter the pipeline system, causing the vacuum degree to fail to reach the expected value. Even small leakage points can have a significant impact on the performance of vacuum generators over time.

 Example: A piping system with a small leak (leakage rate of 0.1L/min) may experience a decrease in vacuum level of 5-10kPa compared to a completely sealed system.

V. Features of the sucked object

1. Breathability

 • Principle: If there is air permeability on the surface or inside of the object being sucked, such as porous materials, air will continuously leak from the inside of the object into the vacuum system, which will require the vacuum generator to continuously extract more gas to maintain the vacuum degree, thereby affecting its performance.

 • Example: When sucking a piece of sponge material, due to the porous nature of the sponge, the suction flow rate of the vacuum generator needs to be increased several times compared to sucking a non porous smooth plastic plate to maintain the same vacuum degree.

2. Shape and size

 • Principle: The shape and size of the object being sucked will affect the effective area of vacuum adsorption. A larger adsorption area requires a larger suction flow rate to generate sufficient adsorption force, and irregular shapes may lead to uneven adsorption, affecting the overall adsorption effect.

 • Example: When adsorbing a large area (1m ²) flat object, compared to adsorbing a small area (0.1m ²) object, the vacuum generator needs to provide a higher suction flow rate to ensure sufficient adsorption force.

There are many factors that affect the performance of a vacuum generator, including compressed air supply pressure, structural design, working environment, and the features of the object being sucked. When selecting and using a vacuum generator, it is necessary to consider these factors comprehensively to ensure that the equipment can meet specific application requirements and maintain optimal performance.

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