Theory of Machines : Governors

Governor

 PROELL GOVERNOR

A Porter governor is known as a Proell governor if the two balls are fixed on the upward extensions of the lower links which are in the form of bent links BAE and CDF as shown in Figure.

                                                                                  Fig.7: Schematic and Dynamics of Proell governor

 HARTNELL GOVERNOR (SPRING CONTROLLED GOVERNORS)

• It is a spring-controlled governor in which balls are mounted on the bell crank lever and sleeve is loaded by spring force as shown in Fig.
• Initially, the spring is fitted in compression so that a force is applied to the sleeve.
• Two bell-crank levers, each carrying a mass at one end and a roller at the other, are pivoted to a pair of arms which rotate with the spindle. The rollers fit into a groove in the sleeve.

Schematic and Dynamic of Hartnell Governor

 GOVERNOR TERMINOLOGY

Stability:

• A governor is said to be stable if with the increase in the speed, radius of rotation of balls increases.
• A stable governor brings the speed of the engine to the required value and there is not much hunting.      

Sensitiveness of a Governor:

• A governor is said to be sensitive when there is larger displacement of the sleeve due to a fractional change in speed.
• Sensitiveness of the governor shall be defined as the ratio of speed range to the mean speed.

Isochronous Governor:

• A governor is said to be isochronous when the equilibrium speed is constant (i.e. range of speed is zero) for all radii of rotation of the balls within the working range, neglecting friction.

Hunting:

• An excessive fast to & fro motion of the sleeve between the stoppers is known as hunting. It is the worst situation & will introduce noise and vibration.
• Hunting takes place in oversensitive governor.
• Higher the sensitiveness of the governor, the problem of hunting becomes more acute.

Controlling force:

• When the balls of a governor rotate in their circular path, the centrifugal force on each ball tends to move it outwards which is resisted by an equal and opposite force acting radially inwards and is known as the controlling force (CF).

                                                                                                             Fig.9: Controlling force

 Graphical representation of various spring-controlled governors

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