The inspection before starting the diesel generator set is the basis for ensuring its normal operation, and whether the diesel generator can start normally is the key to ensuring its normal operation. Below, based on the starting conditions of diesel generators, we will introduce the factors that affect the starting of diesel generators and relevant precautions.
1. Conditions for starting diesel generators
When starting a diesel generator, there should be sufficient fresh air in the cylinder, the fuel supply system should work properly, and there must be a high temperature inside the cylinder. At this point, the fuel injector sprays diesel into the combustion chamber in a mist, and the diesel generator can start normally. But the increase in temperature inside the cylinder must be achieved through multiple compressions of the piston inside the cylinder.
When a diesel generator operates at low speeds, the temperature and compression force inside the cylinder are low, and there is also a lot of air leakage inside the combustion chamber. The movement speed of the plunger inside the fuel injection pump is slow, and the fuel injector cannot spray fuel into the combustion chamber in a mist form according to the specified technical requirements. If the external ambient temperature is low, the minimum starting speed of the diesel generator must be increased in order to meet the requirements for normal starting.
2. Analysis of the starting power process of diesel generators
The main task of the diesel generator starting device is to provide a certain torque to the crankshaft of the diesel generator and make the crankshaft speed reach above the starting speed of the diesel generator. The speed of the crankshaft is determined by the difference between the torque of the starting device and the resistance torque of the diesel generator itself.
The torque of the starting device is determined by the voltage and capacity of the battery and the power of the starter. If the voltage or capacity of the battery does not meet the specified technical requirements, the diesel generator cannot be started; If the power of the starter is too low, it cannot start the diesel generator normally.
The resistance torque during the start-up of a diesel generator is mainly determined by the viscosity of the engine oil, the frictional resistance of the operating components of the diesel generator, and the gas compression force inside the cylinder. So, different grades of engine oil should be selected in different seasons. When starting a diesel generator in winter, in some cases, depressurization starting is also necessary to reduce the starting resistance of the diesel generator.
3. Methods to improve the starting conditions of diesel generators
At present, there are many methods to improve the starting conditions of diesel generators, including the following.
(1) Decompression method
Adopting the method of reducing pressure on the intake or exhaust valves of the diesel generator to decrease the compression ratio, thereby reducing the starting resistance and starting the diesel generator. This method is more commonly used in winter (refer to the pressure reduction adjustment of diesel generators for specific methods). For some small diesel generators, manufacturers generally design specialized pressure reducing devices to reduce starting resistance.
(2) Preheating method
The methods for preheating diesel generators generally include air preheating, oil preheating, and cooling water preheating. Regardless of which method is used for preheating, it should be determined based on specific conditions.
(3) Manual turning method
This method involves using a large flathead screwdriver to turn the flywheel ring gear of the diesel generator. Before starting, it is generally necessary to turn the flywheel ring gear two or more times. The main purpose of doing this is to reduce starting resistance.
4. The main work of the operator when starting the diesel generator set in winter
When starting a diesel generator in winter, the following tasks should be done: first, ensure good fuel supply; The second is to ensure the capacity and voltage of the battery. For example, the 135 series diesel generator set generally uses a 6Q-195 battery, and in winter, a high-capacity 12V battery with a capacity of 6Q-210 or higher can be replaced, because the starting torque of the diesel generator is determined by the capacity of the battery and the quality of the starter itself; The third step is to manually turn the diesel generator, and the fourth step is to start the intake and exhaust valves by reducing pressure; The fifth step is to heat the cooling water to ensure that the diesel generator is in a hot state.
5. Rapid power supply is not allowed after the diesel generator set is started

After the diesel generator set is started, there should be a preheating and lubrication process for the diesel generator, and normal power supply can only be provided after this process is completed. There are generally three types of preheating and lubrication processes, each requiring a different amount of time. Low speed preheating and lubrication generally require 5 minutes, medium speed requires 5-8 minutes, and high speed requires the water temperature and oil temperature to reach around 50 ℃ before normal power supply can be carried out. After the diesel generator set is just started, supplying power during the preheating and lubrication process can easily cause cylinder pulling, cylinder head cracking, and body cracking of the diesel generator.

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