TWO POINT CONTROL SYSTEM

Modern turbocompressors must deliver not only high performance, but also adaptive efficiency, especially in applications like wastewater treatment, where operating conditions change frequently and energy consumption is a major cost factor. This is where our two-point control system, combining Variable Diffuser Vanes (VDV) and Inlet Guide Vanes (IGV), plays a fundamental role.

Why not just vary speed?

Conventional speed control adjusts the motor and impeller speed to reduce airflow. While this approach is simple, it comes with a major drawback:

  • Airflow reduces linearly (e.g. 50% speed = 50% flow)
  • Pressure drops exponentially (e.g. 50% speed = only ~25% pressure)

This means that to meet minimum flow demands, compressors must be oversized in pressure thus resulting in poor efficiency during most of their operating time.

VDV: smart internal geometry

Variable Diffuser Vanes work by adjusting the geometry of the diffuser channel behind the impeller. Rather than changing the speed, the system modifies how the air decelerates and recovers pressure:

  • Airflow is reduced while maintaining constant pressure
  • Each vane position acts like a different impeller-diffuser configuration
  • The result is high efficiency across a wide turndown range, with no need for pressure overdesign

This makes VDV an ideal strategy for plants requiring flexible, yet energy-optimized operation.

IGV: aerodynamic control at the inlet

Inlet Guide Vanes add a second layer of control. They introduce a pre-swirl to the incoming air, changing its direction before it enters the impeller:

  • This alters the incidence angle between the airflow and the impeller blades
  • It improves aerodynamic alignment and the efficiency of the blade profile
  • It stabilizes the compression process, especially at partial load

Functionally, this is similar to how aircraft wings adjust during takeoff to maintain lift at different speeds

Why two point control system is the best practice

By combining IGVs and VDVs, the compressor can maintain optimal impeller speed while dynamically adjusting to real process conditions both at the inlet and the outlet:

  • Wide turndown range without compromising pressure
  • High efficiency at both high and low flow conditions
  • Better stability under partial load.
  • No need for oversizing or inefficient safety margins
  • Lower total energy consumption and reduced operating costs
  • No need for VFDs

This two-point control system is now considered best practice in high-efficiency single-stage turbocompressor design, particularly in applications like aeration for wastewater treatment, where performance, flexibility, and energy savings are all essential.