Table of Contents
Diesel Engine Governors
A governor is a type of control mechanism used to manage the engine speed or rotational frequency (RPM) of diesel generators. In order to maintain a steady and constant speed of the engine, which in turn controls the voltage and frequency of the electrical power generated, the governor is a crucial part of the generator set.
By regulating the engine’s fuel supply, a governor’s principal job is to react to variations in load and keep the RPM constant. It does this by constantly observing the engine speed and modifying the fuel flow as necessary.
Types of Engine Governor
- Hydraulic type
- Mechanical type
- Inertia type
- Electronic type
Governor Characteristic
Diesel generators are equipped with a droop speed governor that includes an overspeed device. Meanwhile, the main engines feature a constant speed governor with an overspeed tripping function. The inclusion of an overspeed trip in the main engine is crucial for several reasons:
- It helps manage sudden increases in speed and abrupt changes in load, which could occur, for example, from the loss of a propeller in rough seas.
- The overspeed trip serves as a protective measure against potential damage to engine parts.
- This device is connected to the camshaft via gear arrangements, ensuring it responds accurately to speed changes.
- In the event the engine speed exceeds 10 to 15% above the rated speed, the overspeed trip device will automatically cut off the fuel supply.
- A manual reset is necessary before the engine can be restarted, ensuring safety checks and balances are in place.
Functions of the Hydraulic Servo Engine Governor
At the heart of every diesel generator, ensuring it runs smoothly, is a crucial component known as the governor. This device, especially in its form as a hydraulic servo engine governor, acts as the conductor of a complex mechanical orchestra, aiming to keep the generator operating both efficiently and steadily.
What sets the hydraulic servo engine governor apart is its unique combination of mechanical innovation and hydraulic accuracy. Its main job is to keep an eye on the engine’s speed and make sure it aligns with the changing demands for electrical power. It does this through a straightforward yet effective approach: sensors monitor the engine’s speed continuously. If the speed starts to drift away from what’s needed, the governor quickly adjusts the fuel supply to the engine.
The magic happens with a hydraulic control system, which uses pressurized fluid to move a servo mechanism that then adjusts the fuel flow. This action keeps the engine speed steady, no matter how much the electrical load might vary. As a result, the electricity generated is stable and reliable, keeping your home or business powered smoothly. This critical function of the governor highlights its essential role in ensuring diesel generators work reliably and efficiently, keeping our world powered up without a hitch.
Hunting of Engine Governor
Hunting is the result of abnormal increase or decrease of speed due to control of fuel supply. Hunting is caused due to the unavoidable time lag between the governor movement and response of the engine.
Engine Governor Droop
- Governor droop is the difference between the no load speed and full load speed in percentage.
- Small droop will result in frequent swinging.
- Large droop setting will result in slow response of Governor.
Governor Isochronous type
- Constant speed governor are known as Isochronous Governor.
- Isochronous Governor has the ability to maintain the speed with zero hunting.
- Isochronous type Governor has proportional and reset properties.
Method of Generator Engine Over speed trip test
- Slowly raise speed of Engine by speed adjusting knob at idle condition.
- The mechanism of Over speed device, should cut off the fuel supply above 15% of the engine normal speed.
Purpose of using the Speed Droop Governor in generator Engine
- For the load sharing ability
2.Governor should function as per the function of AVR of Alternator
Advantage of over speed trip in addition to the Governor
- Speed is controlled within prescribed limits by the governor.
- Rise of speed more than 15 % of the rated speed in the event of an accidental change in load from full load to no load.
- Parts may damage in the event of sudden over-speed due to the time delay action of Governor Control.
- For the above reasons the Over speed trip is provided.
Operation of Isochronous Governor
- Isochronous Governor maintains the constant speed without hunting.
- Isochronous Governor has the temporary speed droop.
Sensitivity of a Engine Governor
Is the ability of a governor to control the speed in narrow limits?
Maintenance schedules on Engine Governor
- Periodically check of Oil
- Change of Governor oil
- Greasing of linkages and joints
Governor function in details (Engine Governor)
The amount of fuel is required to be controlled for an engine operating under changing loads and speed range.This device is called the governor.
Factors affecting the Diesel Engine speed.. (Engine Governor)
- Injected fuel amount in to the cylinders.
- Engine working load.
Assuming the engine is operating at a certain speed. The Engine slows down upon the increase in load. Engine will speed up due to the fuel injection while the decrease of load. Engine speed at a specific range can be kept by regulating the fuel injection amount. Various types of governor has been desigined to do this.
Operating principle of the Governor is centrifugal force. Due to the centrifugal force an object rotating in a circular path will have the tendency of keeping away from its rotating axis. Forces due to the increase in speed will affect the rotating weights. Vital centrifugal force pushes the weights from their axis.
The speed governor prevents Engines from speeding or racing. Over speed governor is based on pair of flyweights fitted on the governor drive shaft. Flyweight’s outward motion is conveyed to a collar. Which slides on the shaft? Fuel pump linkage is actuated with the movement of this collar. A spring presses upward against the collar.
Collar is pressed upward by the spring. Flyweight has the tendency to move upward during the operation of the engine at average speed. Movement is retarded by the spring. As soon as the engine speed rises above the safe speed, the centrifugal for ce of the flyweight depresses the spring. This decreases the Engine speed by reducing the amount of fuel injected.
Over speeding of the engine is prevented by the over speed governor.
In some engines over speed governor is also named as over speed trip, prevents the engine from over speeding if the speed exceeds the limit.P rinciple of One flyweight over speed working is centrifugal force.The rotating flyweight is held closely to the driveshaft by a spring, during the engine operation at safe speed. Flyweights trip a latch by moving outward during the over speeding of Engine. Engine will stop shutting off the fuel to the injection vavle by the movement of fly weights.
Consider repeating the action in steps. A spring holds the flyweight to the drive shaft. Centrifugal force controls the resistance of spring during the engine speeding up, and the flyweights fly out away from the drive shaft. Spring loaded plunger is released due to the flyweights tripping the latch. Engine stops due to fuel cut out lever bringing the fuel control of the fuel pumps to no fuel position.
Reset the latch and fuel pumps before restarting the engine.This is done by this reset arm which is mounted on the reset lever shaft.
Stopping the engine manually (by hand) is done with the help of the cut-off cam mounted on the engine. Cam turns the cut-out lever and shuts off the fuel pumps when the Engine’s starting lever is moved to stop.
The regulating Engine Governor not only keeps the Engine from over speeding but maintains the engine speed at a fixed rate despite changes in load. In this governor, the flyweights are linked hydraulically to the fuel control assembly. A piston connected to the fuel system controls a housing spring is part of this assembly. Oil pressure on the lower side of the piston balances the downward pressure of the spring. The amount of oil in this space is regulated by a valve called the pilot valve controlled by the flyweights.
During the operation of engine at set speed, pilot valve plunger covers the port to power cylinder. The plunger is held in this position by the fly weights .if the engine load decreases however the engine speeds up and the additional centrifugal force throws the fly weights outward raising the pilot valve plunger.
Thus the pilot valve plunger uncovers the port and oil from the power cylinder flows to drain passage through pilot valve cylinder. The power spring forces the piston down actuated the linkage to the fuel system controls and the supply of fuel to the engine cylinders is diminished.
As the engine speed returns to the set rate the flyweights resume their original position and the pilot valve plunger again covers the port. The flyweights move inward if the load decreases. Inward movement of flyweights causes to lower the pilot valve plunger allowing the oil to flow the pilot valve chamber to the power cylinder.
This oil supplied by a pump is under a pressure sufficiently high to overcome the pressure of the power spring. The upward movement the power piston increases the amount of fuel injected. Once again as the speed returns to the set rate the flyweights resume their central position.
Governor shaft transmits the drive to the gear pump for the supply of high pressure into the system. Gear pump takes the suction from the governor sump. Return of excess oil to sump is affected by the spring loaded accumulator which maintains the stable head.
To increase the regulating governor’s sensitivity and to prevent overcorrection a compensating mechanism is used. Compensation mechanism enables the pilot valve port to keep in open for the suitable period for the engine speed to return back to pre-adjusted speed.
A compensating plunger on the power piston shaft moves in a cylinder which is also filled with oil. When the engine speed increases and the power piston moves downward the compensating plunger is also carried down drawing oil from a cylinder below the pilot valve bushing. This creates suction above the receiving compensating plunger which is part of the bushing. The bushing moves upward closing the port to the power piston. Hence the power piston in stop conditions to disable the overcorrection.
As the flyweights and pilot valve returned to their central position Oil flowing through a needle valve allows the compensating spring to return the pilot valve bushing to its central position. Bushing and Plunger should come down at the similar speed for closing the port. Therefore adjust the needle valve to ensure the pass of oil at the suitable rate for the particular engine.
The actuating compensating plunger moves upward with the power piston during the reduction of speed below its nominal set range. This increases the oil pressure above the receiving compensating plunger. The compensating plunger travels down along with the pilot valve bushing.
As before the port leading to the power cylinder is closed. the excess oil in the compensating system now drains out through the needle valve as the spring returns the bushing to its central position. By changing the tension of the speed adjusting spring the speed of the engine is set.
Oil allowed to leak past the various plungers for lubrication purposes is drained into the governor oil sump .these are the basic elements of this type of regulating governor In actual operation.
We shall review the functioning of the governor and maintain the engine speed under the sudden increase of load. Drop of engine speed takes place and the pilot valve plunger is lowered by the inward movement of fly weights.
Oil from the gear pump and the accumulator forces the power piston upward increasing the amount of fuel injected into the engine cylinders. in the meantime the pilot valve bushing has moved downward closing the port in the pilot valve. As the engine speed returns to normal the fly weights and the pilot valve plunger and bushing returned to their central position .now if the load suddenly decreases and the engine start to race the fly weights move outward lifting the pilot valve plunger.
The decreasing of injected fuel amount is affected by the movement of the power piston due to the oil drain from the power cylinder. In the meantime, the pilot valve bushing has moved upward closing the port in the pilot valve. Flyweights, plunger, and bushing resume their original position upon the normalization of engine speed. Always keep the governor clean and keep it free from dirty lubricating oil.
Flush it out every two weeks with clean fuel oil. Flush it out every six months with carbon tetrachloride. Refill it with lubricating oil of the viscosity specified by the operator’s manual. Be sure that the oil is always at the proper level keeping it above five-eighths of an inch in the gauge glass never. Never tamper with the governor unless you are positive that there is some trouble with it and even then all repairs should be made only by experienced personal.
Famous brands of Governors
Woodward Governors for Engines
Woodward hydraulic-mechanical governors provide reliable and precise control of engine speed and output in virtually every type of engine application. Woodward governors are used in power generation, marine, pump, compression, and vehicle applications. Available in work output ratings from 10.8 in-lbs up to 500 ft-lbs.
These governors control Engine speed by sensing turbine rotor speed via their input drive shaft, comparing this speed to an internal speed set point, then using a rotary output terminal shaft connected to the turbine’s governor valve to control Engine inlet fuel flow. The basic principle of working of governor is that the governor spring and flyweights are so selected that at any designed engine speed centrifugal force and spring force are in equilibrium
REGULATEURS EUROPA
Regulateour Europa is the world-class governor for the control and monitoring solutions. These Governors are used for Mechanical and electronics Governors and control systems for marine, traction, industrial and offshore applications.
FAQ on Diesel Engine Governors
Blog Conclusion
A diesel engine governor is an essential device for any power plant that runs on diesel. It is designed to automatically maintain the rotary speed of an engine or other prime mover within close limits, regardless of changes in load and fuel consumption. This device ensures that diesel engines run efficiently, produce consistent power, and are reliable over time.
Additionally, it helps reduce maintenance costs associated with excessive wear caused by fluctuating speeds. With a dedicated and accurate diesel engine governor, businesses can benefit from improved performance and longer-term savings.
We hope you enjoyed our blog post on Diesel Engine Governors. Whether you are an expert or just a casual reader, we hope that you found this article to be informative and helpful. Please send us any questions or thoughts you have about Diesel Engine Governors in the comments section of our blog. We would love to hear from you! Thank you for reading, we are always excited when one of our posts is able to provide useful information on a topic like this!
