(6b) The Effect of Trip Throttle Valve Pressure Loss on Steam Turbine Performance

The pressure loss of the inlet trip throttle valve affects the performance of the high pressure (HP) section of a controlled extraction condensing steam turbine.  Optimizing the selection of the size of the trip throttle valve for a specific application will reduce the overall inlet throttling loss of the turbine and improves its efficiency.

The paper provides the change in the available energy, i.e. heat drop, of the HP section of the turbine based on a given inlet steam flow and initial steam conditions, three controlled extraction steam pressures, and three size trip throttle valves

The change in available energy determined for each valve size and controlled extraction steam pressure are used to calculate the power output of the turbine based on the following relationship between throttle flow, actual heat into work and turbine power output.

  Throttle Flow, lb/hr x Actual Heat in to Work, btu/lb = Power Output, hp x 2545

The results obtained provide the performance improvement available from the HP section resulting from optimization of the size of the trip throttle valve.