In doing so the gas continuously enters the rotating impeller. Mechanical shaft power is transferred to the fluid with the help of the blades and resulting in a significant pressure and temperature increase. The remaining kinetic flow energy is afterwards mostly converted into pressure in the diffusor. The compressed gas is then either collected in a volute or transferred to a second compressor stage with the help of a return channel. In Figure 1, the components of a one-stage, centrifugal turbo compressor are shown, where Figure 2 shows the close-up of an impeller including blades.
In general, different types of turbo compressors can be defined based on their design:
- Centrifugal turbo compressors: the flow enters the turbo compressor in axial direction and exits the impeller in the centrifugal direction. Both 2D- or 3D-impeller blades are possible.
- Mixed flow turbo compressors: the flow enters the turbo compressor in axial direction and exits the impeller neither in a pure centrifugal nor in a pure axial direction, and the exit has a larger radius.
- Axial turbo compressors: the flow enters the turbo compressor in axial direction and exits the impeller in axial direction with a similar radius.
The following figures illustrate the different compressors-types:
The capability of a turbo compressor is best illustrated in a compressor performance and a power map (see Figures 6 and 7), where the pressure ratio (outlet pressure p2 to inlet pressure p1) versus the mass flow at a constant speed n is shown. Dots with the same efficiency η on different characteristic curves are joined to provide efficiency curves. In general, the compressor map is defined by the maximum speed of the compressor (to the right) and by the surge line (to the left). Surging is defined as the unpreventable aerodynamic instability. Operating the compressor left of the surge line is not allowed. The performance of the Celeroton products is presented in this visual form and to see more specific details please view the product datasheet.
The pros and cons of a turbo compressor can be summarised as follows:
Advantages of turbo compressors
- High power density and therefore small physical dimensions and low weight
- High reliability, due to only one rotating partin and proven technology
- High efficiency of the energy conversion
- Low noise level
Disadvantages of turbo compressors
- Dynamic operating principle limits the operating area (see compressor map)
- High power density leads to a more challenging thermal management system
- Limited pressure ratios can be achieved for each stage. Higher pressure ratios can be achieved by the series connection of several turbo compressors
To find out more, see our articles on:
- Is a ultra-high-speed turbo compressor the right compressor for your application
- Product and technology overview of Celeroton
Celeroton publications on this topic:
- The design of ultra-high-speed miniature centrifugal compressors
- Design and control of an ultra-high speed turbo compressor for the air management of fuel cell systems
- Micro-generator for ultra micro gas turbine
- Vorteile und Herausforderungen von miniaturisierten, gasgelagerten, ölfreien Turbo Kompressoren für Wärme- & Kälteanlagen