best turbine performance

When turbine is operated at constant inlet steam pressure or variable pressure mode,steam consumption drops or increases. What is the reason & why?ūüėē

Replies

  • rebellionofrebel
    rebellionofrebel
    You must go over the Tubine control philosophy and the powerp lant philosphy in general. There is something called as Turbine Follow Mode and Boiler Follow Mode. You will be able to get your answers hopefully.
  • akpower
    akpower
    Turbine follow mode or boiler follow mode refers towhich generation (MW ) to be hooked up. If hooked to turbine, it will vary as per the turbine inlet pressure variations. If hooked to boiler, it will respond to boiler outlet pressure variation. It is steam flow which dictates the generation (MW).I am interested to know how the steam admission control valve behave to corresponding steam pressure variation so that generation remains constant.
  • rebellionofrebel
    rebellionofrebel
    Kindly refer to the turbine governing system .. The governing system controls the flow of steam to turbine ......... It takes input from the power plant control !!! If you know turbine follow mode and boiler follow mode then you should also be aware of how it gives input to the contrl vavle using the Electro hyraulic governor and (corresponding EHC)!!!!
  • Ramani Aswath
    Ramani Aswath
    I shall give an analogy. Almost sixty years back I spent a couple of days visiiting the Pykara Hydro-electric Power Station in the Nilgiris. The generator was based on the old Pelton wheel system. At the end of the penstock pipe there was a valve linked to a simple four ball mechanical speed governor directly coupled to the Pelton wheel out put shaft. When the the load on the generator increased, the wheel slowed down because of higher torque on the shaft. The four balls moved closer to their drive shaft. This raised the valve flap so that more water could come in. The governor stabilized to the new demand level.

    The modern turbines have more sophisticated sensors and circuitry. However, the control principle is the same. When load goes up, steam inlet to turbine also goes up.
  • akpower
    akpower
    We all know the governing principle of engine/rotational machines.Steam flow is function dependent on area & velocity.Any control valve with fixed cross sectional area will admit the steam proportional to demand by adjusting its lift. Since flow & pressure are inversely proportional with each other for fixed opening,electrical demand/steam flow when increased, drops the inlet steam pressure of turbine. If the constant pressure mode of operation is used in turbine mode, then the control valves will try to close to maintain inlet steam pressure which will reduce steam flow contrary to actual expectation.Therefore boiler will have generate more steam to meet the demand i.e.steam flow for turbine /electrical demand of generator. Therefore, co-ordinated boiler & turbine steam control may solve the issue.

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