Exploring the Gas Turbine's Electronic Governor

The gas turbine electronic governor is a vital system takes charge of controlling the amount of fuel entering the combustion chamber. And it does this throughout the engine's entire operation, from the initial start-up to handling increases and decreases in power demand, including unexpected power drops. In the following sections, we'll be dissecting the core components of this electronic governing system and understanding how each piece contributes to this critical function.

the main objective of the governor system

The control system acts like the brain of the gas turbine. It receives data from various sensors and employs sophisticated algorithms to determine the perfect fuel flow for smooth operation. This ensures the engine maintains desired performance while staying within its safe operating zone. Think of this zone as having boundaries – limits for factors like maximum compressor pressure, speed, and turbine inlet temperature. The system also safeguards against sudden surges caused by rapid acceleration or flameouts.

The control system is made up of multiple "mini-managers" called control loops. Each loop focuses on a specific parameter, like exhaust gas temperature or speed. They constantly compare sensor readings with desired setpoints and adjust fuel flow accordingly. It's like having multiple dials to fine-tune different aspects of the engine. Ultimately, all the control loops work together, and the system chooses the lowest fuel demand required to meet all the parameters.

While fuel flow is the main tool, airflow can also be adjusted for more precise control. This is achieved by mechanisms like variable inlet guide vanes (VIGV) or variable stator vanes (VSV). These vanes can be moved using hydraulics or stepper motors. Additionally, the angle of the turbine nozzles can be adjusted to influence engine performance.

It's important to note that the specific design and layout of the governor system might vary between different gas turbines. However, the core function – maintaining smooth and safe operation – remains the same across all designs.

The Major Control Loops

The electronic governor relies on a team of specialized control loops, each playing a vital role in maintaining smooth and safe operation. We'll delve deeper into each loop in future articles, but for now, let's get acquainted with their functions:

Ramp Generator: Imagine a conductor setting the pace. This loop gradually increases fuel demand as the engine starts, ensuring a smooth transition from ignition speed to normal operation.

Acceleration Limiter: This loop acts like a safety governor. It sets a maximum fuel limit for acceleration, preventing the engine from ramping up too quickly and potentially causing damage.

Exhaust Gas Temperature (EGT) Limiter: This loop monitors the exhaust temperature, a crucial indicator of engine health. If the temperature rises above the safe limit, the loop adjusts fuel flow to bring it back down.

Power Turbine Speed Controller: Just like a car's cruise control, this loop keeps the power turbine spinning at the desired constant speed. It continuously adjusts fuel flow based on the actual speed compared to the setpoint.

Gas Generator Minimum Speed Controller: This loop safeguards against a potential engine damage during rapid power reductions. It ensures the gas generator (the core of the engine) maintains a minimum speed to prevent a flameout.

Gas Generator Maximum Speed Controller: Picture a car exceeding a speed limit. This loop functions similarly, monitoring the gas generator speed and adjusting fuel flow to prevent it from exceeding its safe limit and causing potential damage.

Variable Inlet Guide Vane Controller: the IGVs are used for surge control and protection by controlling the air flow on either a single or twin shaft machine. the IGV control algorithm controls the angle of the IGVs by manipulating the IGV actuator output depending on parameters like air compressor speed and engine exhaust temperature.

The Winning Formula: Prioritizing Safety

In essence, the gas turbine governor acts like a team of specialists working in concert. Each control loop focuses on a specific parameter, constantly monitoring and adjusting fuel flow to maintain optimal performance. But there's a twist – the loop demanding the lowest amount of fuel takes control. This clever algorithm ensures the engine always operates within its safe zone. By prioritizing the most restrictive parameter, like turbine temperature, speed, or compressor pressure, the governor prevents the engine from exceeding any of its design limits.

References:

1. Gas Turbine Handbook Principles and Practices 3rd edition, A. Giampaolo