Governors:

In the previous unit, you studied flywheel that minimises fluctuations of speed in the cycle however it cannot minimise fluctuations because of load variation. It means flywheel does not exercise any control on mean speed of the engine. In order to minimise fluctuations in the mean speed that may occur because of load variation, governor is utilized. The governor contains no effects over cyclic speed fluctuations but it controls the mean speed over a long period throughout which load on the engine might vary.

While there is modification in load, variation in speed also occur then governor operates a regulatory control and adjusts the fuel supply to maintain the mean speed closely constant. Thus, the governor automatically regulates through linkages, the energy provide to the engine as demanded by variation of load so that the engine speed is maintained nearly constant.

Given figure shows an illustrative sketch of a governor along linkages that regulates the supply to the engine. The governor shaft is rotated through the engine. If load on the engine enhance the engine speed tends to drop, as a consequence of which governor balls move inwards. It causes sleeve to move downwards and this movement is transmitted to the valve from linkages to enhance the opening and, so, to enhance the supply.

Alternatively reduction in the load increases engine speed. As a consequence of which the governor balls try to fly outwards. It causes an upward movement of the sleeve and it drop off the supply. Therefore, the energy input (fuel supply in IC engines, steam in steam turbines, and water in hydraulic turbines) is adjusted to the new load on the engine. So the governor senses the modification in speed and then regulates the supply. Because of this type of action it is simple instance of a mechanical feedback control system that senses the output and accordingly regulates input.

                              Governor and Linkages

Objectives

After learning this unit, you must be able to

• classify governors,
• analyse different kind of governors,
• know regarding the characteristics of governors,
• know about the stability of spring controlled governors, and
• compare different kind of governors.