It is combination of pressure compounding and velocity compounding as shown in Figure 5.9a. There are two rotors and only two rows of moving blades are attached on each rotor because two row wheels are more efficient than three row wheels. The steam on passing through each row of moving blades reduces its velocity, but pressure remains constant during passing through these blades. Thus, it acts as velocity compounded. The whole pressure drops in two nozzles as shown in Figure 5.13, thus it acts as pressure compounded.
Figure 5.13 Pressure–Velocity Compounding of Impulse Turbine
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