GOVERNOR

Q.1. Define governor.

Ans. A governor is a device which automatically controls the supply of fuel to the engine. When the load varies and keeps the mean speed within certain limits.

Q.2. Name two types of governor.

Ans. There are two types of governors:

1. Centrifugal governors,

2. Inertia governors.

Q.3. State the principle of working of centrifugal governor.

Ans. The centrifugal governor works on the principle of balancing the centrifugal force on the rotating balls by an equal and opposite radial force known as controlling force.

Q.4. Define height of governor.

Ans. It is the vertical distance from the centre of the governor balls to a point where the axes of the upper arm intersect on the spindle axis. It is denoted by h.

Q.5. Define equilibrium speed in case of governor.

Ans. It is the speed at which the governor balls are in complete equilibrium and the sleeve does not tend to move in either direction.

Q.6. Define sleeve lift.

Ans. The vertical distance which the sleeve travel due to change in equilibrium speed is called sleeve lift.

The average force which acts on the sleeve for a given percentage change of speed is called effort of a governor.

Q.7. Define effort of a governor.

Ans. The average force which acts on the sleeve for a given percentage change of speed called effort of a governor.

Q.8. Define power of a governor.

Ans. The power of a governor is defined as the work done on the sleeve of governor for a given percentage change in speed of the governor. It is calculated by the product of effort and displacement of the sleeve.

Q.9. Define sensitiveness of a governor.

Ans. A governor is said to be sensitive when it readily responds to a small variation in speed.

This may also be defined as the ratio of the mean speed to the change of speed of the governor over its limit of operation.

Q.10. Define hunting of a governor.

Ans. A governor is said to hunt if the engine speed fluctuates continuously above and below the mean speed. This is caused by a too sensitive governor.

Q.11. Define slab sling of a governor.

Ans. A governor is said to be stable if there is one equilibrium speed for each radius of rotation of balls. The balls occupy a definite position for each speed of the engine within the working range.

Q.12. Define isochronisms of a governor.

Ans. A governor is said to be isochronous if, neglecting friction, the equilibrium speed is the same for all the radii of rotation of balls. This results in infinite sensitivity and the governor will always fly to one or other extreme position.

Short Answer Question

Q.1. Draw a neat sketch of centrifugal governor.

Ans.

Fig. Centrifugal Governor

Q.2. Classify centrifugal governors.

Ans. The centrifugal governors can be further classifieds as follows:

1. Pendulum type : Simple Watt governor

2. Loaded type :

(a) Dead weight type:

(i) Porter governor,

(ii) Proell governor.

(b) Spring loaded type:

(i) Hartnell governor,

(ii) Hartung governor,

(iii) Wilson-Hartnell governor,

(iv) Pickering governor,

(v) Governor with stability and spring control.

LONG ANSWER QUESTION

Q.1. Differentiate between flywheel and governor.

Ans.

Sr. no.	Flywheel	Governor
1.	The function of a flywheel is to control the fluctuation of speed due to variation in the engine turning moment during each cycle of motion.	The function of governor is to control the fluctuation of speed due to variation in the load over a period of time.
2.	It works continuously in each cycle.	It works intermittently when the load varies.
3.	A flywheel stores energy when it is available in excess of the load requirement and gives the same when it is less than the requirement.	A governor regulates the speed by controlling the quality or quantity of fuel according to the load requirements.
4.	A flywheel may not be used when there is no undesirable cyclic fluctuation of energy output	The governor is essential for all types of engines as it adjusts the supply according to demand.
5.	A flywheel does not have any control over the quality or quantity of the working fuel.	A governor has control over the quality and quantity of the working fuel.
6.	It is provided on engines and fabricating machines such as shear machines, punching machines etc.	It is provided on prime movers such as engines and turbines etc.

Q.2. Derive an expression for the height of a porter governor.

Ans. Porter governor is modification of a simple Watt governor. A central load is attached to the sleeve as shown in fig. The central load moves along the central spindle. This additional downward force increases the speed of rotation required to enable the balls to rise to any predetermined level.

Fig. Porter Governor

Neglecting the friction between the spindle and sleeve and considering the equilibrium of right half configuration, let us take moments about I.

if the arms of the governor are equal and pivoted on the axis of spindle or are at equidistant from the axis of spindle, then

Now let us consider the force of friction between the sleeve and the spindle.

The force of friction always acts in a direction opposite to that of motion. Thus, when the sleeve move upward, the force of friction on sleeve acts downward. Similarly, when sleeve moves downward, the force of friction on sleeve acts downward. Similarly, when sleeve moves downward, the force of friction on sleeve acts upward. In general, the net force acting on the sleeve is depending upon the movement of sleeve.

After considering friction, the equation (i) becomes

Q.3. Explain the construction and working of hartnell governor with the help of neat sketch.

Ans. Hartnell governor is a spring loaded governor. Initially, the spring is fitted in compression so that a force is applies to the sleeve. It consists of two bell crank levers hinged in the frame. The frame is attached to the governor spindle and therefore, rotates with it. Each bell crank lever carries a mass at one and a roller at the other. The rollers fit into a groove in the sleeve as shown in fig.

As the speed increases, the balls move away from the spindle axis, the bell crank levers move on the pivot and lift the sleeve against the spring force. As the speed decreases, the sleeve moves downwards. The movement of the sleeve is further taken to the throttle of the engine. The spring force can be adjusted with the help of a screw cap nut.

Fig. Hartnell Governor

Q.4. Derive an expression for the effort of a governor.

Ans. When a governor is running at constant speed, it is in equilibrium and the net force acting on the sleeve is zero. If the load on the engine changes, the speed also changes and hence, the sleeve of the governor changes its position. This can take place only if, a certain force acts on the sleeve and the sleeve will occupy a new equilibrium position when the resultant force acting on it becomes zero again. The average force which acts on the sleeve for a given percentage change of speed is called effort of the governor.

The governor effort may be calculated in the following way:

Let us consider a Porter governor. Let be the equilibrium speed of the governor and let it change to .

If the arms of the governor are equal and pivoted on the axis of rotation, then

Let R is the force applied on the sleeve which prevents its motion at new speed .

Dividing equation (i) by (ii), we get

Let is the frictional force between the sleeve and the spindle of the governor, then

Let are the angles of inclination of the upper and lower arms with the axis of governor spindle respectively, then neglecting friction,

For a simple watt governor,

It can be seen from te equation (iii) and (iv) that the effort of Porter governor is more than Simple Watt governor.

Q.5. Derive an expression for the power of governor.

Ans. Power of a Governor : The power of governor is defined as the workdone on the sleeve of governor for a given percentage change in speed of the governor. It is calculated by the product of effort and the displacement of the sleeve.

Let us consider a Porter governor. Let be the equilibrium speed of the governor and let it changes to .

If the arms of the governor are equal and pivoted on the axis of rotation, then

At new speed ,

Change in the level of balls,

For a simple Watt governor,