STEAM TURBINES–Definition and comparison with Reciprocating Steam Engine

STEAM TURBINES–Definition and comparison with Reciprocating Steam Engine


Steam turbine is a prime mover which gets its rotary motion from the gradual change in momentum of steam jet by simply changing the direction of the jet which is coming at high velocity from nozzles and striking the blades of the turbine.




Steam Turbine Reciprocating Steam Engine
1. In this there is a double conversion of energy, first steam is set in motion by nozzles and then this jet rotates the steam turbine. Steam is directly used to overcome the external resistance and there is no dynamic action of steam.
2. It is versatile in application. It is used to produce large power with generators. It runs big ships. It can be used to run pumps, compressors and fans. It has limited application.
3. It can be used with widely fluctuating loads. Steam engine is not suitable with widely fluctuating loads.
4. Thermal efficiency is high. Thermal efficiency is low.
5. Perfect balancing possible. There is problem with perfect balancing.
6. Robust foundations are not required because of perfect balancing. Robust foundations are required because of imperfect balancing.
7. There are no rubbing parts. Hence lubrication is much simpler. There are rubbing parts. Hence lubrication posses problems.
8. Much higher speeds and hence more power can be developed. Much higher speeds are not practical and hence more power cannot be developed.
9. There is no additional device to achieve rotary motion. Eccentric is used to convert reciprocating motion into rotary motion. Thus there will be more friction and more losses.
10. Steam turbines can be overloaded with little drop in efficiency. There is sudden big drop in efficiency under ove5rload conditions.
11. Rate of steam consumption does not increase with years of use. Rate of steam consumption increases with years of use due to development of leakages.
12. Its life is long. Its life is less due to the rubbing action.
13. Steam turbines can be built in sizes to produce power from a few kW to around 200 MW or even higher. Power producing capacity of steam engines is small and limited.
14. Steam turbine develops power at a uniform rate and thus does not need a flywheel. Steam engine does not  develop power at a uniform rate and thus  needs a flywheel.
15. There is a less Repair maintenance. There is more Repair maintenance.