Unit-6

GOVERNOR

Q1) Explain Controlling force?

A1) During the governing action of a governor the centrifugal force acting on the balls due to the rotation is balanced by an equal and opposite force on the balls, this radially inward balancing force is known as the controlling force for a governor.

Q2) Discuss Sensitivity of a governor

A2) An equipment is said to be sensitive if the value of variation or range is having significant vale with respect to the mean value otherwise if variation is negligible with respect to mean value is said to be insensitive. Hence, the sensitivity of a governor is given by the ration of range of speed to the mean speed, and It is represented by S.

But if the sensitivity of the governor will be too high, it will continuously oscillate between upper stop and lower stop. In such condition the governor will not control the speed of engine rather it operates the engine by switching on and off continuously, this phenomenon of large sensitivity is known as hunting.

Q3) Discuss Power of a Governor

A3) The power of a governor is defined as the work done at the sleeve for a given percentage of change in speed. It is calculated by the product of effort and displacement of the sleeve

The work to be done on the sleeve to change the by a given percentage is known as the Power of a governor, it can be represented by the product of the displacement of the sleeve and effort of the governor.

Q4) Explain Isochronism of a governor

A4) It the variation in the speed of a governor becomes zero the governor is said to be isochronous. This means that for all position of sleeves and balls governor has the same equilibrium speed.

For Porter governor, with all arms equal in length and intersecting on the axis (neglecting friction),

For governor to be isochronous but if we see above equations it is impossible to have two positions of balls for same speed. Hence pendulum governors such as watt, porter and Proell can never be isochronous. But spring governor such as Hartnell can be isochronous.

Q5) How many types of governor?

A5) There are two types of governors:

1)     Centrifugal governors-This kind of governors are extensively used and control the exact speed of vehicle or machinery. In this kind of governors controlling forces balances the centrifugal force.

2)     Inertia governors: In this kind of governors controlling force balances the inertia force. Inertia governor controls the rate of change of speed, hence this kind of governor’s also known as fine-tuned governors.

Q6) Define hunting of a governor

A6) 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.

Q7) Define stability of a governor

A7) A governor is said to be stable if there is only one radius of rotation of the fly balls for the governor equilibrium, for each speed of the engine within the working range.

Q8) State the principle of working of centrifugal governor.

A8) 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.

Q9) The height of a Watt’s governor is equal to?

A9) If N is the speed of the arm and ball about the spindle axis, then the height of the governor (h) is given by h = 895/N2 metres

Q10) Explain the height of a Watt’s governor?

A10) If N is the speed of the arm and ball about the spindle axis, then the height of the governor (h) is given by h = 895/N2 metres from this expression, we see that the height of a Watt’s governor is inversely proportional to N2