24-08-2011, 09:23 AM
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AN INTRODUCTION TO A GOVERNOR
Once a diesel engine is running, the engine speed is monitored and controlled through a governor. The governor ensures that the engine speed stays high enough to idle at the right speed and that the engine speed will not rise too high when full power is demanded. The governor is a simple mechanical device which first appeared on steam engines. It operates on a diesel engine as shown in the diagram below.
The governor consists of a rotating shaft, which is driven by the diesel engine. A pair of flyweights are linked to the shaft and they rotate as it rotates. The centrifugal force caused by the rotation causes the weights to be thrown outwards as the speed of the shaft rises. If the speed falls the weights move inwards.
The flyweights are linked to a collar fitted around the shaft by a pair of arms. As the weights move out, so the collar rises on the shaft. If the weights move inwards, the collar moves down the shaft. The movement of the collar is used to operate the fuel rack lever controlling the amount of fuel supplied to the engine by the injectors.
What is the purpose of a governor/actuator on a diesel motor?
The governor keeps the motor from running faster than a set rate, an actuator receives an input from a button and causes a mechanical device to engage. Speed and Load controllers determine how fast the generator motor should turn over for a certain electrical demand, as in number of devices plugged in to the electric socket.
FUNCTIONS OF A GOVERNOR
A governor performs the following functions on the locomotive;
1-FUEL CONTROL
2-SPEED CONTROL
3-LOAD CONTROL
4-AS A SAFETY DEVICE
These functions help the locomotive in performing in well and efficient manner.
TYPES OF GOVERNORS
In Indian railways locomotives mainly three types of governors are used, which are given below:
1-MECHANICAL GOVERNOR
2-ELECTRICAL GOVERNOR
3-ELECTRONIC GOVERNOR
NOTE :- The Mechanical governor is also known as Woodward’s Governor or Electro hydraulic Governor. PGEV (Pneumatic governor electric variation) is a type of mechanical Governor. GE (General electric) governor is a type of electrical governor. MCBG (Micro controller base governor) is a type of Electronic Governor.
PARTS OF MECHANICAL GOVERNOR
Mechanical governor is a very sensitive part of locomotive. It acts in a locomotive as BRAIN in human body. Its design is very complicated, it consists of very large no. of components ( total 865 components). Some of those main parts are listed below:
1-BASE
2-POWER CASE
3-COLUMN
4-SIDE PLATE
5-INTEGRAL VANE SERVOMOTOR
6-RESISTANCE PACK
7-RESISTANCE PACK COVER
8-LUBE OIL INDICATOR GAUGE
9-LUBE OIL FILTER
10-FUEL LIMITER ASSEMBLY
11-SOLENOID PACK
12-TRIANGULAR PLATE
13-FLYWEIGHT ASSEMBLY
14-POWER PISTON
15-SHUTDOWN PLUNGER
Working principle of diesel engine governor
*A vital component of any diesel engine system is the governor, which limits the speed of the engine by controlling the rate of fuel delivery.
*Diesel engine speed is controlled solely by the amount of fuel injected into the engine by the injectors. Because a diesel engine is not self-speed-limiting, it requires not only a means of changing engine speed (throttle control) but also a means of maintaining the desired speed. The governor provides the engine with the feedback mechanism to change speed as needed and to maintain a speed once reached. A governor is essentially a speed-sensitive device, designed to maintain a constant engine speed regardless of load variation. Since all governors used on diesel engines control engine speed through the regulation of the quantity of fuel delivered to the cylinders, these governors may be classified as speed-regulating governors. As with the engines themselves there are many types and variations of governors. In this module, only the common mechanical-hydraulic type governor will be reviewed. The major function of the governor is determined by the application of the engine. In an engine that is required to come up and run at only a single speed regardless of load, the governor is called a constant-speed type governor. If the engine is manually controlled, or controlled by an outside device with engine speed being controlled over a range, the governor is called a variable- speed type governor. If the engine governor is designed to keep the engine speed above a minimum and below a maximum, then the governor is a speed-limiting type. The last category of governor is the load limiting type. This type of governor limits fuel to ensure that the engine is not loaded above a specified limit. Note that many governors act to perform several of these functions simultaneously.
