Centrifugal compressors are dynamic, which means that compression is performed by converting kinetic energy into static energy. The characteristic of a centrifugal compressor is that the head is determined by the volume flow through the unit.
A centrifugal compressor with an axial inlet (a typical full-wheel gearbox) uses a hose of the appropriate length to allow gas to flow smoothly into the opening of the first impeller.
The flow rate of the these types of compressors is relatively constant at full load for a given inlet pressure and temperature. In the common terminology of screw compressors, they are called “base load”, which means that they must always operate at full load. If there are truly properly controlled screw compressors that are used as “trim” and have relatively constant intake conditions, then this is a simplified but correct representation of most compressor applications. radial air. However, most current centrifugal air compressor systems do not operate at base load and intake conditions change dramatically over the season.
Sometimes centrifugal air compressors are in a purely centrifugal system. They are oversized and have low efficiency at part load. One is working and the other is on standby. Or there are several units operating in different parts of a large factory air system, working independently, sometimes efficiently, sometimes inefficiently. Or they are in a hybrid screw / centrifugal system, where they run parallel to the screw compressors and also in part load operation.
Centrifugal compressor parts
1) Air Inlet
The inlet of a centrifugal compressor is usually a single pipe. It can include functions such as valves, fixed blades / profiles (to rotate the flow), and pressure gauges and temperature gauges. All additional devices have important uses in plugging centrifugal compressors.
2) Centrifugal Wheel
The necessary element of compressor centrifugation is the centrifugal wheel, which consists a lay of rotating blades (or vanes) that can steadily increase the energy of the working gas. It’s like an axial compressor, except the gas can reach higher speeds and energy levels due to the increased radius of the wheel. In various current high performances centrifugal compressors, the gas released from the impeller move at a speed near to the speed of sound.
The design of wheel has a variety of compositions including “open” (blades visible), “covered or blanket”, “with baffle” (remove all other inductors) and “no baffle” (all complete blades). Figures 0.1 and 3.1 show an open wheel with a splitter. Most modern high performances wheels use a shovel-shaped “sweep”.
The next most necessary component of a simple centrifugal compressor is the diffuser. Behind the impeller in the flow path, the diffuser is responsible for converting the kinetic energy (high velocity) of the gas into pressure by steadily reducing (diffusing) the velocity of the gas. The diffuser has no fins, or a possible combination. The highly efficient vane diffuser is also construct for various solids from less than 1 to greater than 4. Hybrid versions of vane diffusers include: corner, channel and tube diffusers. Some turbochargers do not have a diffuser.
The collector of centrifugal compressors can have numerous shapes. When the collector is emptied into a large cavity, the manifold can be called a plenum. If the diffuser is built into a device that looks a bit like a snail shell, horn, or French horn, the dispenser is most likely called a scroll or parchment. As the name suggests, the collector is used to collect the flow from the diffuser outlet ring and direct it to the downstream pipeline. The manifolds or pipes may also contain valves and pressure gauges that control the compressor.
Advantages of centrifugal compressor
- Lightweight, easy to sketch and manufacture.
- Acceptable for continuous compressed air supply, e.g cooling devices.
- Essentially oil-free.
- They have fewer friction parts.
- The flow rate is higher than that of a positive displacement compressor.
- Relative energy savings.
- Wide speed range.
- The centrifugal compressor is definitive and has low maintenance costs.
- Compared to an axial compressor, each stage generates a higher-pressure ratio.
- Does not require a special base.
Disadvantages of Centrifugal Compressor
- Compared to an axial compressor, the front surface is larger for a given air flow.
- Not acceptable for very high compression and finite pressure.
- They are very careful to alters in gas composition.
- They work at high speeds and demand accurate vibration setup.
- Problems with overvoltage, constipation and suffocation.
Applications of Centrifugal Compressor
- Radial compressors in the food industry provide oil-free compressed air for certain delicate applications (e.g food processing).
- Centrifugal compressors require high compressed air essential.
- Oil refineries, natural gas processing.
- Cooling, air conditioning and HVAC.