AME Unit 11 Q8

Sensitivity in a governor refers to its ability to respond quickly and effectively to changes in engine speed. It measures how much the governor’s output (typically a control signal to adjust fuel supply) changes for a given change in engine speed.  

1. [Solved] How is sensitivity and stability related to governor? – Testbook

Quantifying Sensitivity:

• Sensitivity is often expressed as a ratio of the change in governor output to the corresponding change in speed.
• A higher sensitivity value indicates that the governor responds more aggressively to speed changes.

Importance of Sensitivity:

• Quick response: A sensitive governor can quickly correct deviations in engine speed, ensuring stable operation.
• Load handling: A sensitive governor is better equipped to handle sudden load changes without significant fluctuations in engine speed.

Limitations of High Sensitivity:

• Instability: Excessive sensitivity can lead to hunting, where the engine speed oscillates around the desired value.   1. [Solved] How is sensitivity and stability related to governor? – Testbook testbook.com
• Wear and tear: Rapid movement of governor components due to high sensitivity can increase wear and tear.

In conclusion, governor sensitivity is a crucial parameter that must be carefully balanced to achieve optimal engine performance. A well-tuned governor should be sensitive enough to respond quickly to speed changes while avoiding instability.

Hunting in the context of governors refers to the oscillatory behavior of the controlled system. It occurs when the governor overcompensates for changes in speed, causing the engine to oscillate above and below the desired speed.

Causes of Hunting:

• Excessive sensitivity: A governor that is too sensitive can overreact to small speed changes, leading to hunting.
• Poor damping: Insufficient damping in the governor system allows oscillations to persist.
• Load variations: Rapid and frequent load changes can exacerbate hunting tendencies.

Consequences of Hunting:

• Reduced system performance: Hunting leads to fluctuations in engine speed and output power, affecting the overall system performance.
• Increased wear and tear: Continuous oscillations can cause excessive wear on engine components and the governor itself.
• Passenger discomfort: In applications like vehicles, hunting can result in uncomfortable vibrations.

To prevent hunting, governors are often equipped with damping mechanisms and have their sensitivity carefully tuned.

Speed droop is a characteristic of a governor that defines the intentional reduction in engine speed as the load increases. It’s expressed as a percentage of the rated speed.  

1. SPEED DROOP IN POWER GENERATION 🏎️ – Energy Central

2. Droop speed control – Wikipedia

How it Works:

• No load: At no load, the governor maintains the engine at its highest speed setting.
• Load increase: As the load on the engine increases, the engine tends to slow down. The governor, instead of immediately restoring the speed to the original setpoint, allows the speed to drop slightly.   1. What is speed droop on a diesel engine? What about isochronous? Why and when is each useful? – Welland Power tickets.wellandpower.net
• Fuel adjustment: The governor increases the fuel supply to compensate for the increased load, but it does not fully restore the original speed.

Purpose of Speed Droop:

• Load sharing: In systems with multiple engines connected in parallel, droop allows for automatic load sharing. The engine with the lower droop setting will take on a larger share of the load.   1. What is speed droop on a diesel engine? What about isochronous? Why and when is each useful? – Welland Power tickets.wellandpower.net
• Stability: Droop helps to stabilize the system by preventing excessive hunting and oscillations.   1. Speed Droop in Power Control Explained – RealPars www.realpars.com
• Simplified governor design: Governors with droop can be simpler and less complex than those without.

In essence, speed droop is a controlled reduction in engine speed as the load increases, ensuring stable operation and efficient load sharing.  

1. Speed Droop in Power Control Explained – RealPars

A governor is considered stable if, for a given speed within its operating range, there is only one equilibrium position for its moving parts. In simpler terms, the governor should return to its original position after a disturbance without oscillating excessively.  

1. [Solved] Statement (I): If a centrifugal governor is stable at a part – Testbook

Factors Affecting Stability:

• Sensitivity: A governor with high sensitivity can be prone to instability as it may overreact to small speed changes.
• Damping: Adequate damping is essential to absorb energy and prevent oscillations.
• Friction: Friction in the governor mechanism can help to dampen oscillations and improve stability.
• Load characteristics: The nature of the load can influence governor stability. Sudden load changes can challenge the governor’s ability to maintain stability.

Importance of Stability:

• Smooth operation: A stable governor ensures smooth engine operation without excessive speed fluctuations.
• Reduced wear: Stability reduces wear and tear on engine components.
• Improved performance: A stable governor contributes to better overall system performance.

In essence, a stable governor is crucial for reliable engine operation and prevents issues like hunting and erratic behavior.

Isochronous governing is a control mode where the engine speed is maintained constant, regardless of the load applied to it. In simpler terms, the governor continuously adjusts the fuel supply to the engine to compensate for load changes, ensuring a constant output speed.  

1. What is speed droop on a diesel engine? What about isochronous? Why and when is each useful? – Welland Power

Key Characteristics:

• Constant speed: The engine operates at a fixed speed, irrespective of load variations.   1. What is speed droop on a diesel engine? What about isochronous? Why and when is each useful? – Welland Power tickets.wellandpower.net
• Quick response: The governor must respond rapidly to load changes to maintain constant speed.   1. What is speed droop on a diesel engine? What about isochronous? Why and when is each useful? – Welland Power tickets.wellandpower.net
• High sensitivity: To achieve constant speed, the governor needs to be highly sensitive to speed deviations.   1. What is speed droop on a diesel engine? What about isochronous? Why and when is each useful? – Welland Power tickets.wellandpower.net

Applications:

• Standalone generators: Where maintaining a constant frequency is crucial.   1. What is speed droop on a diesel engine? What about isochronous? Why and when is each useful? – Welland Power tickets.wellandpower.net
• Applications requiring precise speed control: Such as in laboratory equipment or machine tools.

Challenges:

• Stability: Achieving perfect isochronous control can be challenging due to factors like load fluctuations and governor limitations.
• Load sharing: In parallel operation, isochronous governors can lead to unequal load sharing, requiring additional control mechanisms.

While isochronous governing offers precise speed control, it’s often combined with other control strategies to address its limitations.