Types of governor

 

Types of governor

·         Mechanical governor

·         Mechanical hydraulic governor

·         Electronic governor

Mechanical governor

Mechanical governor consist of ball arm and flyweight which are connected to linkages that is supported on pivot the ball arm rotates in proportional speed to the engine speed the linkages are then connected to fuel rod that control the fuel oil supply.

                         

Centrifugal force on the flyweight is controlling element of the fuel  supply.

As load increases the speed of the ship reduces so proportional to that the speed of the fly weight also reduces and hence the centrifugal force acting through fly weight also reduces and this result in increase In fuel supply to the engine till the set speed of the engine is attained .

When decrease in load take place the engine speed increases and proportional to that speed of fly weight decreases this result in outward movement of the ball and the linkages provided will reduce the flow of fuel inside the engine till the set speed is attained

Mechanical hydraulic governor

1. Ball head   2. Centering spring   3. Receiving piston   4. Reservoir   5. Transmitting piston

 

·         When load increases, the engine speed decreases along with the centrifugal force. The spring force becoming greater causes the pilot valve 10 to move down. This allows oil to flow to the servo. The servo causes the increase in the fuel racks 6.

• The servo simultaneously acts on the transmitting piston 5 which applies a force onto the receiving piston 3. This receiving piston pushes the centering spring 2 and causes the closing of the pilot valve (pilot valve moving up). Thus, equilibrium and stability are achieved at a lower speed. Once the oil in the compensating system leaks past the needle valve, the centering spring causes the speeder spring to return to its original valve, so that equilibrium is brought about at the original speed, in spite of the increased load.
• The hydraulic governor has operational problems in case of low oil level, dirty oil, incorrect viscosity, air lock, wrong adjustments, excessive oil operating temperatures, and wear at fine clearances.

 

Electronic governor

§  The block diagram shows the general arrangement of an electronic governor. The speed sensor consists of a set of gear teeth that rotate at speed of engine and a Magnetic Pick Up (MPU) that has a slight air gap. The MPU has a permanent magnet and pole piece. A coil surrounds the pole piece. The permanent magnet creates its own magnetic field.

§  During running as each ferrous gear tooth passes the core, the reluctance path decreases, and the flux lines increase. The change in flux lines produces an AC sine wave voltage in the coil and its frequency represents the speed of engine. The AC voltage is amplified and rectified to a DC voltage which is proportional to the engine rpm. This DC voltage is compared with the desired set voltage at the controller (corresponding to the desired rpm). An appropriate electric signal is sent to an electro-hydraulic converter. The electro-hydraulic converter processes the signal and operates an actuator (hydraulic cylinder and piston) to increase or reduce the fuel supply as required. An actuator position feedback is provided to the controller as show