Mr. Hartnell designed his governor circa 1875 and at the time it was considered to be of a superior design to other governors of the day. It rotated between 500 and 600rpm and by utilizing smaller fly balls and fewer parts, the internal friction was less than that of others.
The function of a governor is to regulate the mean speed of an engine, when there are variations in the load e.g. when the load on an engine increases, its speed decreases, therefore it becomes necessary to increase 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 governor automatically controls the supply of working fluid to the engine with the varying load conditions and keeps the mean speed within certain limits.
It is a Spring-loaded Governor. It has two bell crank levers carrying the fly ball at one end and roller attached to the other end, the function of spring is to provide the counterforce which acts against centrifugal force. The spring and shaft are enclosed inside a casing. The sleeve is pressed against the spring when the centrifugal force on the balls increases. Due to spring return nature this governor can be mounded in a horizontal, inverted, (inclined) position.
Parts of Hartnell Governor:
The following are the main parts of the Hartnell Governor.
Frame: This is provided with a spring inside which protects and supports it and the frame is connected to the bell crank lever which rotates along with the lever.
Balls: These are placed on the bell crank lever which is done with some specified weight.
Bellcrank lever: This is used to rotate along with the balls provided on it and it is connected to the frame to rotate it.
Nut: This is proved on the top of the frame, which used to adjust the force on the sleeve.
Spring: This is used to apply the pressure on the sleeve whenever required and this helps to push the sleeve downwards when it raised more than the required.
Collar: This provided on the top of the sleeve to support the spring on it.
Sleeve: This used to move in an upward and downward direction according to the rotation of the bell crank lever attached to it. and this helps to flow the required amount of fluid into the engine when it raised above from the bottom point.
Working of Hartnell Governors :
Hartnell governor is a spring controlled centrifugal governor, in which a spring controls the movement of the ball and hence the sleeve. Above fig shows a Hartnell governor. It consists of a frame /casing, in which a precompressed helical spring is housed. The casing and spring can rotate about the spindle axis. The spring applies a downward force on the sleeve through an adjustable collar. The spring force can be adjusted by a nut provided. Two bell crank levers are pivoted at O,O’ to the frame, each carrying a ball at one end a roller at another end. The roller fits into the grooves of the sleeve.
The sleeve moves up and down depending on the governor’s speed. When the speed of the governor/ engine increases, the ball tends to fly outward from the axis of the governor, but the ball’s movement is constrained. The bell crank lever moves on a pivot, roller end of lever lifts the sleeve upward against the spring force. This movement transferred to the throttle valve through a suitable mechanism, the result is low fuel supply and decreasing speed.
When speed decreases the sleeve moves downward, and throttle open to more fuel supply; which results in increasing speed.
Advantages of Hartnell governor
It can be operated at very high speed
Smaller in size
Very close regulation
Pre-compression can be adjusted to give the required equilibrium speed.
Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.
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