Difference between reaction and impulse turbine (MEACS 2)

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Difference

Sl. No. Impulse Turbine Reaction Turbine
1 Steam completely expands in the nozzle itself. Hence its pressure remains constant as it pass over the moving blades Fixed blades (guide blades) act as nozzles. Hence steam expands both in fixed and moving blades continuously as it passes over them. Thus the pressure drop occurs gradually and continuously as it pass over both the fixed and moving blades
2 Blade (steam passage) is of constant cross section area, as there is no expansion of steam. Blade (steam passage) is of variable cross-sectional area (converging type), as there is expansion of steam
3 As pressure remains constant in moving blades, the relative velocity of steam passing over the moving blades remains constant As Pressure drop occurs continuously in the moving blades (steam expands continuously as it passes over the moving blades), the relative velocity of the steam passing over the moving blades continuously increases
4 Shape of the Blades are symmetrical, hence manufacturing of blade is simple. Shape of the Blades are non-symmetrical (aerofoil), hence manufacturing of blade is difficult
5 Because of large pressure drop in the nozzle, the steam velocity is high & turbine rpm /speed is also high. Due to small pressure drop in the fixed blades (guide blades), the steam velocity is low & turbine rpm/speed is  also low.
6 Because of large pressure drop in the nozzles, the number of stages is less, for the same pressure drop. Hence the size of the turbine, for the same power output is small. Because of small pressure drop in each stage, the number of stages is more, for the same pressure drop. Hence the size of the turbine, for the same power output is large. These turbines are multi-stage turbines only.
7 Occupies less space per unit power Occupies more space per unit power
8 Suitable for small powers Suitable for medium and higher powers

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