The term "Governing" means the action of varying the fuel supply in accordance with the load demand so that the engine runs at practically constant speed. Below are the some important methods of governing of internal combustion engines.
01) Hit & Miss Governing-
This method is suitable for small gas engines. In this, the rotational motion of the cam actuates the rocker through the roller. The rocker carries a pecker, which strikes against the pecker block and lifts the valve against the pressure of the spring. At very high speed, the pecker block is lifted by the rod due to rise up of governor sleeve resulting the engine performs an idle cycle because no fuel is now being supplied.
This method of governing is quite simple but owing to the violent explosions which usually occurs as a result of extra scavenging which takes place immediately after "missed explosion', produces uneven turning moment necessitating the use of heavy flywheel which increase the friction at the bearing and lowers the mechanical efficiency of the engines.
02) Qualitative Governing-
This method is widely used in all heavy oil engines besides being always used on two stroke cycle engines in which the air fuel mixture has to be admitted to the engine cylinder to drive out the burnt charge of the previous cycle.
In this method, under the action of centrifugal governor the amount of fuel entering the cylinder is varied by altering the stroke of the Oil Pump or by passing a part of fuel which would have otherwise been injected into the engine cylinder back to the oil tank or by delaying the closing of the suction valve in the fuel pump.
03) Quantitative Governing-
In this method, the quantity of air -fuel mixture flowing into the cylinder is varied accordingly. This may be done by decreasing the lift of the inlet valve or by throttling the mixture before it is made to enter the engine cylinder. This method is largely used for governing petrol and big gas engines.
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