Reasons for Difficulty Starting Diesel Generator Sets in Communication Base Stations at Low Temperature

Analysis of the reasons for the difficulty in starting diesel generator sets in communication base stations at low temperatures mainly includes the following points:

 

(1) Low temperature environment causes the battery capacity to decrease, thereby reducing the torque of the starting motor. Most diesel generator sets use electric starting, especially the backup small-power units of communication base stations. The optimal operating temperature of the battery is usually between 10 and 40°C. When the temperature drops, the capacity of the battery will drop significantly, sometimes only 50% of the capacity is left at 25°C, which directly affects the torque of the starting motor and makes starting difficult.

 

(2) The starting resistance torque between moving parts increases. Under low temperature conditions, the shrinkage deformation of different materials will cause the fitting clearance to decrease. The crankshaft and bearing, piston and cylinder liner of the diesel engine have different thermal expansion coefficients due to different materials. The difference in shrinkage deformation rate will cause abnormal fitting clearance, thereby increasing the starting resistance. At the same time, the viscosity of the diesel engine lubricating oil increases at low temperatures, the fluidity deteriorates, and it may even lose its flow ability, which will also increase the resistance torque of the diesel engine. Taking all these factors into consideration, the increase in starting resistance torque makes it difficult for the diesel engine to reach the speed required for starting, resulting in starting difficulties.

 

(3) Intake air temperature is too low and compression end pressure is insufficient

In a low temperature environment, the air temperature is low, and the combustion air temperature entering the diesel engine cylinder is also low. At the same time, the temperature of the diesel engine's cylinder, piston and other components and lubricating oil is also low, resulting in a large heat loss of the air during the compression process. The heat is absorbed by the cylinder and piston and other components. Finally, the temperature of the air during compression may not reach the auto-ignition point of the diesel. In addition, the temperature of the oil-gas mixture in the cylinder is too low, and the contact surfaces of the cylinder and piston and other components are poorly lubricated, which may cause the pressure of the compressed oil-gas mixture to be lower than the pressure required for starting.

 

(4) Changes in the physical properties of diesel in low temperature environments

Related data show that when the temperature drops from 40°C to -10°C, the viscosity of diesel increases by 83% and the density increases by 8%. Under low temperature conditions, the viscosity and density of diesel both increase, the surface tension increases, the fluidity deteriorates, and the atomization effect is poor, thereby extending the ignition lag period of diesel.