Radial inflow expanders

Figure 4-37. Two radial inflow expanders mounted on a single gear box. (Source GHH-Borsig.)...

Figure 4-40. Two-stage radial inflow expander with variable inlet guide vanes (right). (Source Demag Delaval.)...

Radial-Inflow Turbine The radial-inflow turbine, or inward-flow radial turbine, has been in use for many years. Basically a centrifugal compressor with reversed-flow and opposite rotation, the inward-flow radial turbine is used for smaller loads and over a smaller operational range than the axial turbine. Radial-inflow turbines are only now beginning to be used because little was know about them heretofore. Axial turbines have enjoyed tremendous interest due to their low frontal area, making them suited to the aircraft industiy. However, the axial machine is much longer than the radial machine, making it unsuited for certain vehicular and helicopter applications. Radial turbines are used in turbochargers and in some types of expanders. 

If hquid droplets form as ihe gas is expanded in the turboexpander, one s first thought may be that a radial inflow design is the last diing to use, but the following explanation will show that this is the only design that can accomphsh expansion efficiently. 

Most ethylene plants operate continuously with the expanders operating at or near design conditions. If necessary, due to their unique design characteristics, radial inflow turboexpanders can accommodate a wide range of process conditions without significant losses in thermal or mechanical efficiency. Expanders may be loaded with booster compressors, gear-coupled generators, dynamometers, or other in-plant mechanical equipment such as pumps. In ethylene plants, turboexpanders are typically used in eitlier post-boost or pre-boost applications. 

Power is generated by the pressurized gas expanding through an 11,000 rpm single-stage, radial-inflow turbine expander, which drives a synchronous generator. Exhaust gas from the expander is liquified by air-cooled condensers and is pumped back to the heat exchangers to repeat the cycle. 

Type of expander Single-stage, radial-inflow Single-stage, radial-mflow... 

In a radial-inflow turbine the problems of erosion and exducer blade vibration are prominent. The size of the particles being entrained decreases with the square root of the turbine wheel diameter. Inlet filtration is suggested for expanders in the petrochemical industry. The filter usually has to... 

At lower temperature levels, refrigeration is provided by hydrogen turbo expanders which are the first of their kind for this particular service. These turbo expanders are the key to efficient, low-horsepower-per-pound-of-liquid production and are quite flexible to meet varying operating conditions in the plant. The turbo expanders are of the radial inflow type and the power generated... 

---