The Advances in Positive Displacement Turbo Blowers

Since 1868, Aerzen has been developing positive displacement blowers according to the Roots principle. Then, in 1987, Aerzen introduced the three-lobe blower to the market, while simultaneously patenting the process technology. The company has continued to develop on these many years of experience and has built the positive displacement blower into an advanced high-tech product

Image Credit: Aerzen

Functionality of the Positive Displacement Blower

The conveying direction is based on the turning direction of the rotors as well as the installation position of the stage. Depending on the assumption that the normal installation position provides vertical conveyance, and that the rotational direction makes the top-to-bottom conveyance easy, the basic principle is as follows: as demonstrated, the air flows from the upper inlet port into the stage.

In combination with the exterior wall and the lobes of the pistons, the rotation of the rotors creates so-called “conveying chambers”, where there is still ambient pressure. The system pressure is adjusted as soon as the first lobe passes the opening to the pressure side. This is known as isochoric compression. The rotors seal off each other to the inside, and this prevents a change of pressure.

Technology

Compression Principle

The isochoric compression principle, also called external compression, is used to operate the positive displacement blowers. By intermittently transporting a gaseous medium, for example, atmospheric air, into a system, the pressure increase is attained. The relevant pressure increase is attained by forcing the medium from atmospheric conditions into a system with a specified resistance, for example, a water column. The blower should operate at a particular output level in order to overcome this resistance. Aerzen calls this «coupling performance» (Pk).

Delta Blowers

Versatility in Numbers

Delta Blowers are solid all-rounders: the largest machines are used to operate lifting systems, while the smallest packaged units are mounted to silo trucks. They can be employed to unload transport ships, and have hourly performance of up to 1,000 tons.

• Control range from 25 to 100%
• Pressures up to 1,000 mbar
• Nominal sizes from DN 50 to DN 400
• Intake volume flows in negative pressure up to 500 mbar
• Intake volume flows from 30 m³/h to 15,000 m³/h

Applications

• Water and wastewater treatment
• Ventilation
• Backwash of filters and much more

Advantages

• Extremely reliable and robust
• No absorbing material in base support
• Oil-free as per Class 0 according to ISO 8573-1
• Sustainable energy efficiency
• Minimized maintenance time and costs

Power consumption of a positive displacement blower. Image Credit: Aerzen

The vertical axis corresponds to the «pressure» p

p₁: Pressure at the blower inlet
p₂: Pressure at the blower outlet
p_V: Suction and pressure loss taking place at the inlet and outlet (also dependent on periphery)
∆p: Difference between intake and discharge pressure

The horizontal axis corresponds to the «volume flow» Q

Q₀: Theoretical volume flow that is defined by the volume in the conveying chamber in the blower
Q_V: Volume flow loss which is produced by the medium flowing back in the clearances of the conveying chamber (between housing and rotor lobe)
Q₁: Usable volume flow

The resulting areas correspond to the power requirement. Technically, this can be deduced mathematically from the below formula:

    P = Q* ∆p

The following can be deduced from the main formula.

P_th: The theoretical power requirement P_th is determined by the differential pressure ∆p and the product of the theoretical volume flow.

    P_th=Q₀ *∆p

In the above illustration, the power requirement corresponds to the area a-b-c-d.

P_K: For the theoretical power requirement P_th, the coupling performance P_K also considers performance losses P_V.

    P_K=P_th+ P_V=Q₀ *(∆p+p_V)

In the above illustration, coupling performance corresponds to the area a-b-e-f.

Characteristics of the Positive Displacement Blower

Currently, positive displacement blowers of the Delta Blower Generation 5 serve as the driving force behind various processes, and are the core of a strong machine combination. Many innovations with this young range have been introduced by Aerzen. They represent outstanding blower power for oil-free conveyance of neutral gases and air, without the requirement for absorbing media. Positive displacement blowers provide a large volume of flow range from 30 to 15,000 m³/hour with simpler handing; reduce life-cycle costs, and even quieter operation.

However, one thing remains the same: the blower class remains extremely robust, thoroughly reliable and has a very long service life. So, it is not surprising that customers choose for uninterrupted, long-term applications - over years and decades.

Image Credit: Aerzen

This information has been sourced, reviewed and adapted from materials provided by Aerzen Machines Ltd.

For more information on this source, please visit Aerzen Machines Ltd.