Short Answer:

Sleeve lift in governor operation is the vertical movement of the governor sleeve when the speed of the engine changes. When the engine speed increases or decreases, the centrifugal force acting on the governor balls also changes, causing the sleeve to move up or down along the spindle. This movement adjusts the fuel supply to the engine, bringing the speed back to its normal or equilibrium value.

The amount by which the sleeve moves is known as sleeve lift, and it represents the sensitivity of the governor. A higher sleeve lift means the governor responds more effectively to small speed changes.

Detailed Explanation:

Sleeve Lift in Governor Operation

The sleeve lift in a governor refers to the total vertical displacement of the sleeve that occurs when the engine speed varies between its minimum and maximum limits. This lift is a crucial aspect of governor performance, as it indicates how effectively the governor can respond to speed variations and control the fuel supply.

In any centrifugal governor, such as Watt, Porter, or Hartnell types, the balls are connected to arms, which in turn are connected to a sleeve mounted on a spindle. As the engine runs, the spindle rotates, and due to centrifugal force, the balls move outward when speed increases. This outward movement of the balls causes the sleeve to rise. Similarly, when the engine slows down, the centrifugal force decreases, and the sleeve moves downward due to gravity or spring tension.

This up-and-down motion of the sleeve is known as sleeve lift, and it directly controls the throttle valve or fuel supply system of the engine.

Working Principle of Sleeve Lift

When the engine operates, the speed of rotation of the governor spindle depends on the engine speed. As the speed increases, the centrifugal force acting on the rotating balls also increases. This force pushes the balls outward, lifting the sleeve upwards along the spindle. The upward movement of the sleeve reduces the fuel supply to the engine, which in turn decreases the speed.

When the engine speed falls below the normal value, the centrifugal force decreases. The controlling force, either due to gravity or spring, becomes dominant and pulls the balls inward. This causes the sleeve to move downward. The downward movement increases the fuel supply to the engine, which raises the speed back to normal.

Thus, sleeve lift occurs continuously during engine operation as the governor maintains balance between fuel supply and engine load variations.

Magnitude of Sleeve Lift

The magnitude of sleeve lift depends on several factors such as:

1. Type of Governor:
   Different types of governors (Watt, Porter, Hartnell, etc.) have different sleeve lift characteristics due to variations in their mechanism and geometry.
2. Range of Speed:
   The greater the difference between the maximum and minimum engine speeds, the larger the sleeve lift will be.
3. Arm Length and Ball Mass:
   Larger arms and heavier balls result in higher centrifugal forces, which can increase sleeve lift.
4. Spring Stiffness (in Spring-controlled Governors):
   In a spring-controlled governor, the stiffness of the spring affects how easily the sleeve moves. A stiffer spring results in smaller sleeve lift, while a flexible spring allows more movement.
5. Governor Sensitivity:
   Highly sensitive governors show larger sleeve lifts even for small speed variations. Sensitivity is a measure of how quickly and effectively a governor reacts to changes in engine speed.

Relation between Sleeve Lift and Speed Range

The sleeve lift is proportional to the difference in centrifugal forces acting on the balls between the minimum and maximum speeds. This means that:

where  is the maximum speed and  is the minimum speed of the governor.

Hence, if the speed variation of the engine is large, the sleeve lift will also be large. This relation shows that sleeve lift serves as an indicator of the governor’s ability to control speed fluctuations.

Importance of Sleeve Lift in Governor Operation

1. Regulates Fuel Supply:
   The sleeve lift directly operates the throttle or fuel valve. When the sleeve rises, it reduces fuel supply, and when it lowers, it increases the supply.
2. Maintains Engine Speed Stability:
   By adjusting the sleeve position, the governor keeps the engine speed constant despite load variations.
3. Indicates Governor Sensitivity:
   Greater sleeve lift indicates that the governor is more responsive to small changes in speed, which is desirable for smooth operation.
4. Prevents Overspeeding and Stalling:
   Proper sleeve lift ensures that the engine does not overspeed (too much fuel) or stall (too little fuel).
5. Helps in Design Evaluation:
   The amount of sleeve lift is an important parameter considered during the design and testing of governors to ensure reliable performance.

Example

If a governor controls an engine whose speed varies between 280 rpm and 320 rpm, the sleeve may move up or down by about 10–15 mm. This movement is known as sleeve lift. The value of sleeve lift helps determine how sensitive the governor is and how effectively it maintains the speed within the given range.

Conclusion

In conclusion, sleeve lift in governor operation is the vertical movement of the sleeve that occurs when the engine speed changes. It plays a vital role in adjusting the fuel supply to maintain the desired engine speed. The amount of sleeve lift indicates how sensitive and effective a governor is in controlling the engine. Without adequate sleeve lift, the governor cannot respond properly to speed changes, leading to unstable operation. Therefore, sleeve lift is an essential parameter for efficient and accurate governor performance.