Steam quality, mass flow rate, temperature and pressure of the steam

[candice_84]

How should steam quality, mass flow rate, temperature and pressure of the steam be optimized in order to have the most out of turbine? I mean which ones have be to be higher?
Also when they design turbine, do they design it based on the properties of the steam or they change the properties of the reactor to meet the turbine requirement? (I assume this has to be dependent on the power density of the core as well)

 

[PaulS1950]

I believe most turbines operate on pressure drop.
the pressure has to be high enough for the turbine to move at a given torque but there also has to be sufficient volume to produce the speed (rpm) that's necessary.
Can you work it from that?

 

[gmax137]

Look at the enthalpy difference across the turbine (inlet to exhaust), multiply by mass flow rate to get energy 'delivered' to the shaft. Though in the real world this is complicated (e.g., extraction steam at various enthalpies).

In general, the turbine is designed based on specified steam conditions, not the other way around. Most nuclear units provide saturated steam (since the SG tubes are covered with liquid in a PWR and the fuel pins are covered in a BWR). An exception would be the 'once through' steam generators in B&W designs - the upper portion of the tubes is above the water level, and therefore produce some superheating of the steam. You could say that this design began with the desire to provide superheat steam to the turbine.

As far as steam quality (in the U-tube SG designs) - it is important to the turbine designers but I think it is a second order effect (whether the steam is 0.1% or 0.2% moisture carry-over has an effect on the power, but it isn't a big effect).

 

[Astronuc]

How should steam quality, mass flow rate, temperature and pressure of the steam be optimized in order to have the most out of turbine? I mean which ones have be to be higher?
Also when they design turbine, do they design it based on the properties of the steam or they change the properties of the reactor to meet the turbine requirement? (I assume this has to be dependent on the power density of the core as well)

The output of the plant is pre-determined - that's a basic functional requirement/spec. There is some thermodynamic model, so the thermodynamic efficiency is known to some degree.

Turbines are designed to run at a set speed, usually 1500 rpm in areas using 50 Hz, or 1800 rpm in areas using 60 Hz. This determines the blade tip speed based on the size of the blade, and the blade size is determined by the capacity of the turbine and number of stages. The stages and blade designs are optimized with respect to the properties of the steam. There are also high pressure and low pressure turbines on the same train. There can also be intermediate, but on large power turbine sets, I've seen 1 HP and 3 LP turbines.

ARABELLE™ Steam Turbine for Nuclear Power Plants
http://www.power-technology.com/projects/flamanvillenuclear/flamanvillenuclear4.html
http://www.memagazine.org/backissues/membersonly/aug98/features/reactor/reactor.html
http://goliath.ecnext.com/coms2/gi_0199-6648034/Steam-turbines-how-big-can.html

http://www.energy.siemens.com/hq/en/power-generation/steam-turbines/
http://aunz.siemens.com/Energy/Generation/FPG/EP/Pages/PG_4058_SteamTurbinesandGenerators.aspx

http://www.gepower.com/prod_serv/products/tech_docs/en/steam_turbines.htm

http://www.mhi.co.jp/en/products/category/steam_turbine.html

http://www.hitachipowersystems.us/products/steam_turbines/index.html
http://www.hitachipowersystems.us/s.../technical_papers/brochures/Steam_Turbine.pdf
http://www.powergenu.com/courses/9/PDF/PGU_9_HitchiNclrTrbns.pdf

http://www3.toshiba.co.jp/power/english/thermal/products/turbines/steamidx.htm