[ashish_sinha]

Why steam turbine is rotating machine and steam engine is reciprocating machine,even they use same type of fuel(steam) and the working cycle,both of them plot same curve,,

[shatriya]

Conventional piston steam locomotive give a varying, sinusoidal torque, making wheel slip much more likely when starting. That's why Steam turbine was used.

The side rods and valve gear of conventional steam engine locomotives create horizontal forces that cannot be fully balanced without substantially increasing the vertical forces on the track, known as hammer blow.

Steam turbine has greater thermal efficiency and higher power-to-weight ratio. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator - about 80% of all electric generation in the world is by use of steam turbines.
The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam (as opposed to the one stage in the Watt engine), which results in a closer approach to the ideal reversible process.

With all these advantages, steam turbine rules. It was the requirement to get a different technology for the use of steam to overcome all the above mentioned issues with the conventional steam engine.

[ashish_sinha]

Conventional piston steam locomotive give a varying, sinusoidal torque, making wheel slip much more likely when starting. That's why Steam turbine was used.

The side rods and valve gear of conventional steam engine locomotives create horizontal forces that cannot be fully balanced without substantially increasing the vertical forces on the track, known as hammer blow.

Steam turbine has greater thermal efficiency and higher power-to-weight ratio. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator - about 80% of all electric generation in the world is by use of steam turbines.
The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam (as opposed to the one stage in the Watt engine), which results in a closer approach to the ideal reversible process.

With all these advantages, steam turbine rules. It was the requirement to get a different technology for the use of steam to overcome all the above mentioned issues with the conventional steam engine.

I'm not comparing both of two,,
I'm understanding what you have said.
I just want 2 ask why this fundamental difference in motion. If turbine is so much beneficial then why it is not use in steam engine??

[FlyYakker]

Do you mean - why was the turbine not used in the first place instead of pistons??

[ashish_sinha]

Do you mean - why was the turbine not used in the first place instead of pistons????

I am asking that what factor or parameter will be decide that one should b a rotating machine and other b reciprocating machine?
I mean that what is the parameter will not b same in both the machine,that is why this constructional difference occours??

[shatriya]

Steam at a high pressure and temperature is admitted to a working chamber where it expands and acts upon a piston, then the piston consequently reciprocates. the steam enters the cylinder, expands once and exhausts. As steam expands its temperature drops, this is known as adiabatic expansion. As we can see that the reciprocating steam engines works only by the pressure exerted by the steam while expansion.

A steam turbine extracts thermal energy from pressurized steam, and converts it into useful mechanical work. It has its greater thermal efficiency and higher power-to-weight ratio. Here heat of the steam is also utilized with the expansion pressure exerted by the steam. This makes a great difference in terms of thermodynamics and which is the base for all engines.

Moreover, Steam turbines provide direct rotational force and therefore do not require a linkage mechanism to convert reciprocating to rotary motion as in reciprocating steam engines. Thus, they produce smoother rotational forces on the output shaft with less power loss.