Expander (flow machine)
An expander , also turboexpander , gas relaxation - or - expansion turbine called, is a gas turbine in the narrower sense , i. H. a turbine ( turbo-machine ), in which a pressurized gas expands and thereby work guaranteed.
In contrast to a gas turbine, an expander only consists of the actual turbine in the broader sense , i.e. it does not have a compressor or a combustion chamber as an integral part of the machine. The gas to be expanded is therefore not generated by the machine itself (e.g. through a combustion process), but is generated from upstream processes.
In contrast to the pressure reduction through a simple throttle , the energy of the gas is also used by the expander.
The turbine can be single-stage or multi-stage, axial or radial. The dissipated work can be used to drive a generator , a pump or a compressor . The turbocharger of an internal combustion engine consists, for example, of an expander driven by the exhaust gas flow, which is connected by a shaft to a compressor for the combustion air.
The expander is a subordinate of the thermal fluid energy machines and thermal turbo machines (from the Latin turbare = to rotate ).
Components
The expander basically consists of
- a single or multi-stage output shaft of axial (bladed stages) or radial ( impellers ) design
- the guide stages ( guide vanes or diffusers )
- the outer casing.
The output can be on the inlet or outlet end of the shaft.
Similar to gas turbines, the hot gas parameters (temperature, composition) also place high demands on the materials used for the expander components in terms of their strength and temperature stability as well as resistance to corrosion and oxidation. For this reason, only high-alloy ferritic and austenitic steels and nickel-based alloys are mainly used.
Areas of application
For procedural processes in
- Coal and oil gasification plants
- Nitric acid and terephthalic acid plants
- Fluid Catalytic Cracking (FCC) and Residual Catalytic Cracking (RCC) systems
- Furnace gas systems
- Compressed air power plants
either gases with high temperatures and high pressure are generated and only partially “consumed” in the process, or the gases are created in the process itself.
The enthalpy contained in these hot gases can be converted into mechanical energy by expansion and is available again as usable mechanical energy w T for the drive.
The efficiency of an expander is higher, the higher the inlet temperature of the gas and the pressure ratio of the turbine.
If a gas expansion turbine is used to generate electricity with the pressure of a gas network (e.g. natural gas), this is also referred to as pressure to power .
Manufacturer
General Electric , MAN Diesel & Turbo , Siemens Power Generation , Atlas Copco and DEPRAG in Europe and Mitsubishi in Japan.
Individual evidence
- ↑ FAZ.net: Electricity from pressure differences in the gas network from May 8, 2013, accessed on January 12, 2015.