 Myself, Akshay Kumar Subde, Assistant Professor, Mechanical Engineering Department. Today, we will study Governors. Learning outcome, at the end of this session, students will be able to understand the working of centrifugal governor and the terminology of governor. Function of a governor, function of the governor is to regulate the speed of the engine under varying load conditions. For example, when the load on the engine increases, its speed decreases. And therefore, it becomes essential to supply more working fluid to the engine. On other hand, when the load on the engine decreases, the speed of the engine increases. And therefore, it becomes essential to decrease the supply of working fluid. Hence, governor automatically controls the supply of working fluid to the engine under varying load conditions and keeps the mean speed within the subton limit. Or in other words, we can say when the load on the engine increases, the configuration of the governor changes and valve is moved to increase the supply of working fluid. Similarly, when the load decreases, the speed increases and governor decreases the supply of working fluid to the engine. Now, we will study the working principle of centrifugal governor. Centrifugal governor based on the balancing of centrifugal forces acting on the rotating masses by an equal and opposite, the two word radial force which is known as controlling force. So, centrifugal governor consists of two balls which are of same masses known as fly balls or governor balls. These two balls are attached to the arms of the governor and the arms of the governor are devoted on the axis of the spindle. So, that when the spindle rotates, the arm and ball will also rotate about the vertical axis of the spindle. The spindle of the governor is driven by the engine through the bevel gear. The arms are connected to the slew by the links. This slew also rotates about the spindle as well as it slides along the spindle. So, when the speed of the engine increases, the slew will slide in the upward direction and when the speed decreases, the slew will move in the downward direction. So, in order to limit the travel of the slew, the two stoppers SS are provided on the spindle. Now, as the speed of the engine increases, the arms of the governor moves in the outward direction and when the speed decreases, the arms of the governor will move in the inward direction. A slew is connected by a bell crank lever where one end of the bell crank lever is connected to the slew and other end of the bell crank lever carries a throttle valve. Now, when the speed increases, the slew will slide upward and when the speed decreases, the slew will fall down. Now, consider an example when the speed of the engine increases, the centrifugal force acting on the ball which is given by f c is equal to m r omega square. Centrifugal force acting on this ball increases as a result of this, the arms will move in the outward direction which causes the slew to move in the upward direction. And hence, at the other end of the bell crank lever, the throttle valve is operated and the supply of the working fluid to the engine is decreased. And hence, the speed will decrease. Similarly, when the load on the engine increases, the speed of engine and governor decreases. At that time, the centrifugal force acting on this ball also decreases which results in the inward movement of the arm due to decrease in the centrifugal force acting on the ball. Which causes the slew to move in the downward direction. As a result of this, the throttle valve which is connected to the other end of the bell crank lever gets opened and the supply of working fluid to the engine increases. And hence, the slew will move in the upward direction as the speed increases. Hence, the centrifugal governor works on the principle of centrifugal forces acting on the fly balls. Now, think for a while in case of centrifugal governor which is the parameter used in order to control the action of the centrifugal governor. In case of centrifugal governor, the action of the governor is controlled by the gravity action. Also, when the balls are rotating at uniform speed, then controlling force is balanced with centrifugal force acting on the balls. This is the working principle of centrifugal governor. Now, we will see the various terms which are used in governor. The first is the height of governor. So, this figure shows a simple type of vat governor where the height of governor is defined as it is the vertical distance from the center of the fly ball to the point where the axis of the arms intersect on the spindle. That is known as height of the governor and it is represented by h. Second, equilibrium speed. Equilibrium speed of the governor is defined as it is the speed at which the arms balls are in complete equilibrium and slew does not tends to move in either way. That is known as equilibrium speed and it is represented by letter n. Third, slew lift. Slew lift is defined as it is the vertical distance traveled by the slew due to percentage change in the equilibrium speed that is known as slew lift and it is represented by letter x. The next term is maximum and minimum equilibrium speed. Maximum and minimum equilibrium speed of the governor is defined as it is the speed at maximum and minimum radius of rotation of fly balls in which the slew does not tend to move in either way is known as maximum and minimum equilibrium speed. And next term is mean equilibrium speed. Mean equilibrium speed is defined as it is the speed at which the arms and balls are at mean position. That is known as mean equilibrium speed of the governor. The references used in this particular session that is from the book of theory of machine by Arvish Khurmi. Thank you.