Pressure Compounding or Reteau Staging

Pressure compounding is splitting of whole pressure drop of steam from steam chest pressure to condenser pressure into series of small pressure drops across several stages of impulse turbine. The whole pressure drops occur in series of nozzles and there is no pressure drop in fixed blades as shown in Figure 5.11. The kinetic energy of steam increases in nozzles at the expense of the pressure drops and it is absorbed by the blades in producing torque on the shaft.

The pressure compounding of turbine is shown in Figure 5.11a and pressure–velocity diagram in Figure 5.11b. The enthalpy drop in one stage is equal to total enthalpy drop divided by number of stages as shown in Figure 5.11c.

Figure 5.11 Pressure Compounding of Impulse Turbine