GOVERNORS

• 

  The function of governor is to regulate the mean speed of an engine, when there are variations in the load.
• Ex. When the load on an engine increases, it becomes necessary to increase the supply of working fluid.
• When the load decreases, less working fluid is required.
• It automatically controls the supply of working fluid to the engine with the varying load condition and keeps the mean speed within certain limits.

Note:

The function of a flywheel in an engine is entirely different from that of a governor. It controls the speed variation caused by the fluctuations of the engine turning moment during each cycle of operation. It does not control the speed variations caused by a varying load. The varying demand for power is met by the governor regulating the supply of working fluid.

Types of Governors:

1. Centrifugal governors
2. Inertia governors

Centrifugal Governor:

The centrifugal governors are based on the balancing of centrifugal force on the rotating balls by an equal and opposite radial force, known as the controlling force.

Watt Governor:

The simplest form of a centrifugal governor is a watt governor. It is basically a conical pendulum with links attached to a sleeve of negligible weight.

Porter Governor:

The porter governor is a modification of a watt governor, with a central load attached to the sleeve.

Proell Governor:

The Proell governor has the balls fixed at the end point to the extension of the links.

Hartnell Governor:

A Hartnell governor is a spring-loaded governor. It consists of two bell crank levers pivoted at the point to the frame. The frame is attached to the governor spindle and therefore rotates with it.

Hartung Governor:

In this type of governor, the vertical arms of the bell crank levers are fitted with spring balls which compress against the frame of the governor when the rollers at the horizontal press against the sleeve.

Wilson-Hartnell Governor:

A Wilson-Hartnell governor is a governor in which the balls are connected by a spring in tension. An auxiliary spring is attached to the sleeve mechanism through a lever by means of which the equilibrium speed for a given radius may be adjusted. The main spring may be considered of two equal parts each belonging to both the balls.

Pickering Governor:

A pickering governor is mostly used for driving a gramophone. It consists of three straight leaf springs arranged at equal angular intervals round the spindle. Each spring carries a weight at the center. The weights move outwards and the springs bend as they rotate about the spindle axis with increasing speed.

Sensitiveness of Governor:

The sensitiveness is defined as the ratio of the difference between the maximum and minimum equilibrium speeds to the mean equilibrium speed.

Stability of Governor:

- For a stable governor, if the equilibrium speed increases, the radius of governor balls must also increase.

- A governor is said to be unstable, if the radius of rotation decreases as the speed increases.

Isochronous Governors:

A governor is said to be isochronous, when the equilibrium speed is constant (i.e., range of speed is zero) for all radii of rotation of the balls within the working range, neglecting friction. The isochronism is the stage of infinite sensitivity.

Hunting:

A governor is said to be hunt if the speed of the engine fluctuates continuously above and below the mean speed.

Effect and Power of a Governor:

- The effect of a governor is the mean force exerted at the sleeve for a given percentage change of speed (or lift of the sleeve).

- The power of a governor is the workdone at the sleeve for a given percentage change of speed. It is the product of the mean value of the effort and the distance through which the sleeve moves.

Controlling force:

When a body rotates in a circular path, there is an inward radial force or centripetal force acting on it. In case of a governor running at a steady, the inward force acting on the rotating balls is known as controlling force.