Purpose and characteristics of multistage centrifugal blower

1.1 Blower principle

The multistage centrifugal blower works on the gas through the high-speed rotating impeller to increase the gas pressure and speed. The gas with a certain pressure air out of the impeller edge at a higher speed and flows into the diffuser. The gas speed decreases, and part of the kinetic energy of the gas is converted into potential energy, so as to continue to increase the gas pressure, After that, the gas flows through the bend and reflux device into the next stage compression unit to continue compression; In this way, after compression by multi-stage impeller, the gas reaching the required pressure is collected by volute and sent to the system through exhaust port.

1.2 Purpose and classification

The blower is mainly used in various smelting boilers, coal washing plants, mine flotation, sewage treatment, chemical gas making and other occasions where air needs to be transported. It can also be used to transport other non corrosive gases, such as blast furnace air supply, sewage treatment aeration blast, coke oven gas, shaft furnace sintering air supply, etc.

1.3 Structure and technical performance

* The main structure of the blower is a cast body, which is composed of an air inlet casing, an air outlet casing and an intermediate casing. Generally, according to the air capacity and pressure requirements of customers, the intermediate casing can be combined in series to form a 2 ~ 8-stage booster blower. For special users, it can be combined to 10 stages, and the pressure rise can be up to 98kpa. At present, the air capacity of the model under production can cover 35 ~ 220m3 / min.

* Multistage labyrinth seal is adopted between stages, and multistage labyrinth seal plus carbon ring combination seal is adopted at both ends of the inlet and outlet to prevent and reduce leakage to the greatest extent. At the same time, with scientific diffuser, flow stabilizer and reflux device, the blower efficiency is improved to the most advanced international level.

* The steel parts of shaft system are quenched and tempered, and the aluminum alloy parts such as impeller are treated with T6 to ensure the dimensional stability, functional requirements and service life requirements. After finishing machining of precision cast aluminum impeller, first conduct static balance verification, and then install it on the main shaft in sequence, and then conduct dynamic balance verification. The balance grade is G25 (ISO1940), effectively eliminating the generation of harmful vibration under high-speed operation.

* SKF or the brand designated by the customer shall be used for the bearing, and the special lubricating oil for the bearing plus forced air cooling shall be used to ensure that the bearing operates under 75 ℃ for a long time.

* The machine is directly driven by variable frequency motor, and the blower and motor are directly connected by coupling. Temperature and vibration sensors are equipped at the bearing of the blower to prevent damage to the blower caused by excessive temperature or increased vibration. At the same time, lifting holes, hooks or lifting rings are installed on the blower body and base to facilitate installation and maintenance.

* Before leaving the factory, the blower shall be tested on the test bench for aerodynamic test and collection, and the data shall be summarized to form the performance curves of outlet pressure rise, inlet air capacity and efficiency, which shall be recorded and saved.

The general reference indexes of the blower are as follows:

*Inlet air capacity (air volume): when the blower reaches the rated speed, the inlet air capacity generally changes in the range of 75% ~ 105% of the rated air capacity. When the inlet air capacity changes from large to small, the pressure rise changes from small to large.

Caution: When the inlet air capacity is less than 60% of the rated air capacity, the blower is prone to surge, resulting in abnormal vibration or impact, which shall be avoided. The optimal air capacity of the blower can achieve high output efficiency under the working condition of 80% ~ 95% of the rated air capacity.

* boost: the outlet boost increases with the increase of the set value of the frequency modulation motor. After frequency modulation, it is best to set it in the range of 80% ~ 100% of the rated boost value. When the optimal air capacity of the blower is 80% ~ 95% of the rated air capacity, the corresponding range of the boost value is 87% ~ 100% of the rated boost value.

* Outlet temperature: the input medium is generally normal temperature air. If the input temperature of the medium is higher than 20 ℃, the output pressure will be reduced accordingly; On the contrary, if the temperature is lower than 20 ℃, the output pressure will increase and the shaft power will increase. At this time, the motor speed can be appropriately reduced.