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Why Speed of Diesel Generator Set Is Not Well-Distributed

Sep. 11, 2018

The uneven speed of diesel generator set is mostly caused by the abnormal resistance of the parts of the injection pump and governor and the slow response of the governor. Generally, there are two kinds of performance. One is a large swing, the voice is clearly identifiable, commonly known as gasp or tour car. The other is that the speed fluctuates in a small range, the sound is not easy to appear at low speed, which will lead to the diesel engine flameout. The following are eight reason for the uneven speed of diesel generator sets.

Why Speed of Diesel Generator Set Is Not Well-Distributed.jpg



1. Valve clearance is incorrect.

2. fuel spray nozzle is burnt or drip oil.

3. Fuel supply time is too early, easy to produce high-speed "tour", low-speed but stable phenomenon.

4. Oil injection pump regulating tooth rod or fork pull rod astringent, resulting in lower governor sensitivity.

5. The diesel supply system contains air and moisture and the pump is not working properly.

6. Individual cylinders do not work. If a multi-cyliner diesel engine does not work, its operation is not smooth, the noise is not uniform.

7. The oil supply is uneven. When the diesel engine is running, the cylinder with more fuel supply has strong working, percussive sound and black smoke. Less fuel supply cylinder, weak work, or even do not work. Finally, the engine speed is not uniform.

8. Speed regulation is not in time, cause diesel engine speed instability.


When the wear gap at the joints of the governor increases, the movement parts such as steel ball or air hammer are blocked and the speed regulating spring fails, then the governor must overcome the resistance or eliminate the clearance first before the governor can move to adjust the increase or decrease of the fuel supply of the tooth rod or the fork pull rod. As the speed regulation is not in time, speed fluctuates high and low. For 135 or 105 type of combined fuel injection pump, it can be seen that the regulating rod moves repeatedly regularly by opening the side cover of the fuel injection pump. If the diesel engine swims slightly, then you can see the pull rod will jitter.


Importance of reasonable rotational speed range of diesel generator set.


It is important for diesel generator to maintain a reasonable working speed range. The reason is that it can reduce wear and tear effectively, and extend the service life or the genset. Especially when the diesel generator set starts, the crankshaft speed is low, the oil supply of the genst oil pump is not timely, and the oil temperature is low, the oil viscosity is high, the friction surface is difficult to establish liquid lubrication, so the wear is very serious.


The friction of diesel generator increases with the increase of speed and load. As the load increases, the unit pressure on the friction surface increases and the thermal condition is poor. With the increase of rotational speed, the number of friction times per unit time is half plus, and at the same power, the increase of rotational speed is larger than the wear when load is increased. However, too low rotational speed can not guarantee good liquid lubrication conditions, also increase wear.



In addition, when diesel generator sets work unsteadily, such as acceleration, deceleration, stopping and starting, the lubricating condition of diesel generator sets is poor, the thermal state is unstable, and the wear will increase due to the frequent changes of rotational speed and load. Generally speaking, there are two kinds of rotating speed of normal generator sets. One is 1500 rpm, the other is 1800 rpm. It is wrong to artificially turn down or raise the speed of the generator.


Adjusting skill of speed controller before and after starting of diesel engine. In order to understand the adjustment of engine speed controller before and after starting, we must first understand how the speed controller works.



Adjustment before starting diesel engine


Observe a potentiometer that regulates gain and stability. In a general case factory set at 12:00 position (that is middle position red dial code open). The controller has already been set up when it is out of the factory, so it is not necessary to adjust the controller before starting the diesel engine, and the user only needs to start the diesel engine to make fine adjustment.


Adjustment of controller after starting


The actuator should supply the maximum amount of fuel until the diesel engine starts, and the controller should be controlled in the idle position. If the engine is unstable after starting, adjust the gain and stability potentiometer counterclockwise until the engine is stable.


The external high/low speed switch is disconnected and the diesel engine enters the rated speed. Adjust the rated speed potentiometer or the external micro=adjustable potentiometer to adjust the forehead fixed speed precisely. The clockwise rotation frequency of the rated speed setting point is increased.


After starting, the following adjustments are made when the diesel engine s no longer loaded.


Rotate the gain potentiometer clockwise until it is unstable, then fine tune it counterclockwise until the system is stable, and then progress counterclockwise to adjust a portion of the nozzle to ensure stability.


Rotate the stability potentiometer clockwise until instability occurs, then adjust counterclockwise to stability, and then further fine-tune part of the counter-clickwise to ensure that the engine rotates steadily.


After the adjustment of gain and stability, the rated speed is adjusted by trimming potentiometer to meet the design requirements of the generator set.


If the engine needs to introduce idle operation, the high/low speed switch is closed, and then adjust the speed of the potentiometer to the required speed, and adjust clockwise to increase the frequency (usually 50% of the rated speed).


If the diesel engine can not be stabilized by the above adjustment, it is necessary to adjust the dial up switch at this time, as follows, the gain and stability potentiometer are adjusted again after each trimming, until the engine is stable.


Adjustment of steady adjusting rate

The adjustment of steady state regulation rate is suitable for parallel operation of multiple genset. The droop characteristics of the diesel generator are softened by the short connection of terminal 10/11. the speed of the diesel engine will decrease with the increase of the engine load, and the steady state regulation rate will increase with clockwise adjustment. On the contrary, it will be smaller with the increase of engine load.


After adjustment, the speed of the diesel engine will have a small change, and then reset the speed.


Auxiliary Input


Terminal 13, as an auxiliary input signal, is introduced from a load distribution genset, an automatic synchronization device, and some other control system for automatic synchronization device, and some other control system for automatic synchronization as a system and for use in automatic load distribution.


When the auxiliary input signal is introduced, the speed will change slightly, so it is necessary to re-adjust the rated potentiometer or the external rotating speed fine-tuned potentiometer.


Auxiliary Output


Terminal 14 can be supplied with a power supply of 10V or 20mA to power the external system, but if a short circuit occurs in use, the controller will be damaged.


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