Mechanical governor and type of governor ?

GOVERNORS

Introduction - The function of a governors is to regulate the mean speed of an engine .

When there are variation in the load.When the load on an engine increases .its speed decreases therefore it becomes necessary to increases the supply of working fluid On the other hand,When the load on the engine decreases ,its speed increases and thus less working fluid is required . The governors automatically controls the supply of working fluid to the engine with the varying load conditions and keeps the mean speed within certain limits .

A little configuration of the governors changes and a valve is moved to increase the supply of the working fluid :

Types of governors 

The governors may broadly be classified as 

1. Centrifugal governors  

2. Inertia governors 

Centrifugal governors - 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 .It consists of two balls of equal mass which are attached to the arms .This balls are known as Governor balls or fly bolls . The bolls revolve with a spindle , which is driven by the engine through bevel gears . The upper ends of the arms are provided to the spindle .so that the balls may rise up or fall down as they revolve about the vertical axis . The arms are connected by the links to a sleeve which is keyed to the spindle .This sleeve revolves with the spindle : but can slide up & down  ward direction two stops S S are provided on the spindle .The sleeve is connected by a bell crank lever to a throttle valve . The supply of the working fluid decreases when the sleeve rises and increases when it falls . 
When the load on the engine increases the engine & the governor speed decreases .This results in the decrease of Centrifugal forces on the balls. Hence the balls move inwards and the sleeve move downward .The downward movement of the sleeve operates a throttle valve at the other end of the bell crank lever to increase the supply of working of fluid and thus the engine speed is increase .In this case the extra power output is provided to balance the increase load .When the load on the engine decreases .The engine and the governor speed increases, which result in the increases of centrifugal force on the balls .Thus the balls move outwards and the sleeve rises upwards .This upward movement of the sleeve reduces the supply of the working fluid and hence the speed is decreasesd .In this case the power output is reduced. 

Note - When the balls rotate at uniform speed ,controlling force is equal to the centrifugal force and they balance each other .



Terms Used In Governors 

The following terms used in governors are important from the subject point of view ;

1. Height of a governor -  It is the vertical distance from the center of the ball to a point where the axes of the arms ( or arms produced ) intersect on the spindle axis .It is usually denoted by h.

2. Equilibrium speed - It is the speed at which the governor  balls ,arms etc . are in complete equilibrium and the sleeve does not tends to upwards or downwards .

3. Mean equilibrium speed - It is speed at the mean position of the balls or the sleeve .

4. Maximum and minimum equilibrium speeds -  The speeds at the maximum and minimum radius of rotation of the balls ,without tending to move either way are known as maximum and minimum equilibrium speeds respectively .

5. Sleeve lift - It is the vertical distance which the sleeve travels due to change in equilibrium speed .



PENDULUM TYPE 

1. Watt Governor -  The  simplest from of a centrifugal governor  is watt governor .basically a conical pendulum with links attached to a sleeve of a negligible mass . The arms of the governor  may be connected to the spindle in the following there ways .
1.The pivot P, may be on the spindle axis as 
2. The pivot P, may be offset from the spindle axis and the arms when produced intersect at O,
3. The pivot P , may be offset ,but the arms cross the axis at O ,