Gas Turbine Modulated Inlet Guide Vane System

Variable compressor inlet guide vanes are installed on the turbine to provide compressor pulsation protection during start-up and shut-down and also to be used during operation under partial load conditions. The variable inlet guide vane actuator is an hydraulically actuated assembly having a closed feedback control loop to control the guide vanes angle. The vanes are automatically positioned within their operating range in response either to the control system exhaust temperature limits for normal loaded operation, or to the control system pulsation protection limits during the start-up and shut-down sequences. Inlet guide vanes are modulated in order to maintain various stresses, pressures and flows within required limits. Their corrected speed control system is a portion of their control system, to accomplish this function.

Guide vane actuation
The modulated inlet guide vane actuating system includes the following components: Servo valve 90TV-1, position sensors (LVTD) 96TV-1 and 96TV-2, solenoid valve 20TV and hydraulic dump valve VH3. These are shown on the piping diagram here after. Actuation of the dump valve allows hydraulic oil to flow through servo valve 90 TV-1. Control of 90 TV-1 will port hydraulic oil through the dump valve to operate the variable inlet guide vane actuator.

For normal shutdown, inlet guide vane actuation is the reverse of the startup sequence; the compressor bleed valves will open when the generator breaker is opened. The inlet guide vanes will ramp to the full closed position as a function of temperature corrected speed. In the event of a turbine trip, the 11th stage bleed valves will open and the inlet guide vanes will ramp to the closed position as a function of temperature corrected speed.

In a trip condition, lube oil is dumped by action of dump valve 20TV-1. This causes inlet guide vane dump valve VH3-1 to move to the dump position by action of the spring re-turn feature, thereby dumping actuator cylinder oil which closes the inlet guide vanes.


Operation
I.G.V. operation is described in GEH 6195 in the "Gas turbine operation guide (MARK V) chapter". The various parameters entering the control and protection system (SPEEDTRONIC) are (Figure MGI-1):

TA compressor inlet temperature signal (sometimes referred to as CTIM).

CPD compressor discharge pressure signal.

FSR electronic control signal of the fuel.

TNH turbine speed signal.

TTXM exhaust temperature signal.

Modulated Inlet Guide Vane Hydraulic System

1 comment:

  1. Well i was confused about the design but the diagram has made it clear. It is nice that all the abbreviations are also provided.

    Thanks
    Bruce Hammerson

    Hydraulic Hammers

    ReplyDelete