Short Answer:

A Proell governor is a type of centrifugal governor used to control the speed of an engine by regulating the fuel supply. It is a modification of the Porter governor in which the balls are attached to the extension of the lower arm instead of the upper arm. This arrangement provides greater sensitivity and stability. The Proell governor can respond quickly to small changes in engine speed, making it suitable for high-speed engines.

In this governor, when the engine speed increases, the balls move outward due to centrifugal force, lifting the sleeve upward to reduce fuel supply, and when speed decreases, the opposite happens. Thus, it maintains a nearly constant engine speed under varying load conditions.

Detailed Explanation :

Proell Governor

The Proell governor is an improved form of the Porter governor that is designed to provide better sensitivity and stability for speed regulation in engines. It works on the same basic principle as all centrifugal governors — the regulation of engine speed by adjusting the amount of fuel or working fluid supplied to the engine according to its speed. However, the arrangement of its arms and balls gives it better performance characteristics compared to the Porter governor.

The main function of the Proell governor is to control the speed of an engine automatically by changing the supply of fuel or steam when load conditions vary. When the engine runs too fast, the governor reduces the fuel supply, and when it slows down, it increases the fuel supply, thus maintaining a steady speed.

Construction of Proell Governor

The Proell governor consists of the following main parts:

1. Spindle:
   It is the vertical shaft that rotates with the engine. The rotation of the spindle provides motion to the arms and balls of the governor.
2. Arms:
   There are two upper and two lower arms that form linkages to support the governor balls. The upper arms are connected to the spindle, while the lower arms are connected to a sleeve that can slide up and down the spindle.
3. Balls (Fly Balls):
   Two equal balls are attached at the end of the extensions of the lower arms. These balls rotate with the spindle and move outward or inward depending on the engine speed.
4. Sleeve:
   A sleeve is mounted on the spindle and is free to move vertically. It is connected to the throttle valve through a linkage system. The upward or downward movement of the sleeve controls the fuel supply.
5. Load (Central Dead Weight):
   A central weight is placed on the sleeve to increase the controlling force and maintain balance during high-speed operation.
6. Linkages:
   The linkages connect the arms, sleeve, and throttle valve mechanism. They help transmit motion and adjust the fuel supply according to the movement of the sleeve.

In the Proell governor, unlike the Porter governor, the balls are attached to the extension of the lower arm beyond the joint connecting it to the sleeve. This small structural change significantly affects the performance of the governor.

Working of Proell Governor

When the engine is running at normal speed, the balls rotate in a balanced position under the combined effect of centrifugal force and gravity. The sleeve remains at a mean position, maintaining a constant fuel supply.

• When engine speed increases:
  The centrifugal force acting on the balls increases. Due to this, the balls move outward and upward. This movement raises the sleeve along the spindle through the arm and linkage mechanism. The upward motion of the sleeve partly closes the throttle valve, reducing the fuel supply. As a result, the engine speed decreases and returns to normal.
• When engine speed decreases:
  The centrifugal force on the balls reduces, causing them to fall inward and downward. The sleeve then moves downward, opening the throttle valve more. This increases the fuel supply, which causes the engine to speed up and regain its normal speed.

This process continues automatically, maintaining a nearly constant engine speed under different load conditions.

Advantages of Proell Governor

1. Higher Sensitivity:
   The Proell governor is more sensitive than the Porter governor because of the modified ball position on the extended lower arms.
2. Better Stability:
   The center of gravity of the system is lower, which improves stability during operation.
3. Less Friction Loss:
   The movement of the sleeve and arms is smoother, reducing energy losses.
4. Quick Response:
   The governor reacts faster to changes in engine speed due to improved geometry.
5. More Suitable for High-Speed Engines:
   Its performance is reliable even at higher speeds, making it ideal for modern applications.

Applications

Proell governors are used in:

• Steam engines
• Internal combustion engines
• Turbines and other rotating machinery where accurate speed control is essential

Conclusion

The Proell governor is a modified form of the Porter governor, designed to achieve better sensitivity, stability, and control over engine speed. By attaching the balls to the extended portion of the lower arm, the Proell governor provides smoother operation and quicker response to speed variations. It plays an important role in maintaining a constant speed of engines under changing load conditions, making it widely used in mechanical systems requiring precise control.