The difference between impulse and reaction turbines
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Impulse turbine: Steam expands mainly within the nozzle cascade. Reaction turbine: Steam expands within the stationary and moving blade stages. Impulse and reaction combined steam turbine: The rotor blades at each stage consist of both impulse blades and reaction blades. These are several concepts; may I ask the experts, how can we distinguish between a moving blade cascade and a stationary blade cascade? What are the differences in their structure? Are there any pictures to illustrate this?
The moving blade cascade refers to the area between the rotor’s moving blades, while the stationary blade cascade is the area between the stator’s stationary blades. The expansion process is one of pressure reduction and speed increase. In impulse-type moving blades, it is the steam that impacts the blades to drive the rotor; in reaction-type moving blades, as the steam flows through these blades, in addition to the impact from the steam, the steam itself continues to expand, resulting in pressure reduction and speed increase. It’s similar to a jet airplane, where exhaust gases are pushed backward, causing the plane to move forward. The flow channel has a variable cross-section that tapers gradually.
From the first stage to the final stage, the width and height of both the moving and stationary blades increase.
The reaction degree of ordinary moving blades is 50%
Reply 1# lauhob: The difference between impulse and reaction turbines lies in the following: 1. In a reaction turbine, the cross-sections on the inlet and outlet sides of the rotor blades are asymmetric; the blade profile is wider at the inlet side and narrower at the outlet side, with the steam flow path narrowing from the inlet to the outlet. In contrast, the cross-sections of the moving blades on the inlet and outlet sides of impulse turbines are relatively uniform, with the flow area remaining essentially constant from the inlet to the outlet. 2. In impulse turbines, the pressure drop of the steam occurs in the nozzles of the diaphragm, while in reaction turbines, the pressure drop of the steam occurs in the stationary blades mounted on the cylinder and the moving blades mounted on the rotor. The moving blades of an impulse turbine are mounted on the impeller. The blades of a reaction turbine are mounted on a drum. 3. To balance the thrust, impulse turbines have balance holes in their impellers, whereas reaction turbines are equipped with balance pistons on their rotors.