After scheme design, it was determined that the electro-hydraulic servo control system is composed of mechanical, electrical, and hydraulic components. The instruction signals emitted by the automatic control system are compared with the actual position signals of the cylinder in the servo controller, forming error signals. These signals are amplified and sent to the electro-hydraulic servo valve. The servo valve converts electrical signals into hydraulic oil flow rates to drive the cylinder movement. The feedback signals from the position sensors continuously change until they match the instruction signals, at which point the cylinder stops moving, stopping at the designated position, stabilizing the still blade at this opening. The linear motion of the cylinder is converted into a rotary motion of the valve plate through a crank mechanism, altering the working angle of the valve plate or still blade. Through this analysis, it is explained that as the system signals continuously change, the opening of the still blade also changes accordingly. This change in still blade opening achieves the purpose of controlling the revolution, gas flow rate, and turbine output.

Valve block failure primarily manifests as excessive clearance between the hole and rod, dynamic sealing wear, console shoulder wear, and cavitation. It can be summarized into the following three forms:

Performance Degradation: Accounts for approximately 15% of failures.

(2) Performance Decline: Accounts for approximately 70% of failures, categorized into corrosion and mechanical wear. Mechanical wear can be further divided into abrasion, aging, and adhesive damage.

(3) Accidental Incidents: Account for approximately 15% of failures.

The primary reasons for the failure of valve blocks are:

(1) Insufficient cleanliness of the oil.

(2) The system has entered the air.