Types of governor
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Mechanical governor
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Mechanical hydraulic governor
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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
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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
