Low temperature start of diesel engine
Under low temperature conditions, the increase in fuel viscosity is not conducive to the atomization and combustion of fuel, the deterioration of lubricating oil fluidity increases the resistance of various moving parts, and the influence of factors such as the reduction of battery working capacity can easily lead to difficulty in starting the engine, Mechanical wear, power reduction, fuel consumption increase and power performance decrease. In order to ensure that all kinds of construction machinery can be put into use under cold conditions, in addition to daily maintenance, it is necessary to install a low-temperature auxiliary starting system.
Four common low-temperature starting methods
(1) Filling with cold start fluid
Cold start fluid is an auxiliary starting fuel (consisting of ether, low volatile point hydrocarbons and low freezing point engine oil with additives). The addition of low freezing point engine oil with additives can improve the lubrication conditions of the cylinder wall , To achieve the purpose of starting. Because ether has better volatility, easy ignition and compression ignition, the more ether content, the lower the temperature at which the diesel engine can be started directly, but the rougher the diesel engine will work when starting. Therefore, when using cold start fluid, be sure to fill the specified amount, and never add too much. Although this kind of starting method can start the engine in an instant, but because of the low temperature and high viscosity of the oil at this time, there is not much oil on the cylinder wall for a period of time after starting, and the lubrication conditions are bad. The engine body does reciprocating motion and rotation when the engine is working. Dry friction will be formed between the moving parts, which will increase the wear and tear of the parts; therefore, do not increase the throttle operation after starting the engine with cold start fluid. When choosing this starting method to start, you should choose a starting fluid with better atomization. , And control the injection time, injection position and injection volume. In addition, do not spray the starting fluid directly from the intake port of the air filter, so as not to affect the quality of the air filter element and increase the amount of lifting fluid injected, causing the engine to run over-speed when the cold engine starts. According to the above description, it is recommended to use cold liquid cautiously.
(2) Flame preheating start
The low working temperature of the flame preheating device is -40℃, and the working process is electronically controlled automatically. The flame preheating starting device generally consists of an electronic controller, solenoid valve, temperature sensor, flame glow plug, fuel pipe and wire. The working process of the device is to heat the glow plug to 850-950°C and then turn on the starter. The solenoid valve automatically opens the oil circuit and supplies oil to the glow plug through the fuel pipe to perform flame preheating. After using this device to start the engine Due to the low temperature and high viscosity of the oil at this time, there is not much oil on the cylinder wall for a period of time after starting, and the lubrication conditions are bad. When the engine is working, dry friction will also form between the reciprocating and rotating parts in the body. Increase the wear of the machine parts; due to the high temperature generated in the friction, the friction surface metal can be melted, which can easily cause the machine parts to jam. Therefore, after using the flame preheating device to start the engine, you should also avoid increasing the throttle operation, otherwise it is easy to cause a cylinder pulling accident.
(3) Circulating water heating system (also called fuel heater heating system)
This is a newly adopted low-temperature auxiliary starting method in recent years. This low-temperature starting method is to pump out the coolant in the engine block through the water pump attached to the fuel heater, and recirculate it to the engine block after being heated by the fuel heater. In this way, the engine is heated to achieve the purpose of starting the engine under low temperature conditions. The working principle of the fuel heater is that the electric motor 3 drives the oil pump 2 and the combustion-supporting fan is sent to the atomizer through the oil pipe 22. After atomization, the air sucked by the combustion-supporting fan is mixed in the main combustion chamber 8 and ignited by the hot glow plug 7. After being fully burned in the post combustion chamber 11, it is turned back, and the heat is transferred to the cooling medium in the water jacket interlayer through the heat sink 16 on the inner wall of the water jacket. The heated medium is under the action of the water pump (or thermal convection) in the entire pipeline Circulate in the system to achieve heating purpose. The exhaust gas from combustion is discharged from the exhaust port. The entire heating process of this low-temperature start method takes 30-40min, which can heat the engine body temperature to about 40-50℃. At this time, the engine oil is also heated, the viscosity of the oil decreases, and the lubrication conditions of the engine under low temperature conditions are improved. , So that the engine starts smoothly. This low-temperature starting method has obvious advantages and greatly improves the engine's starting performance under low temperature and cold conditions. It is recommended.
(4) Other preheating methods
In addition to the above preheating methods, hot water preheating (injecting hot water to the boiling point into the cooling system) steam preheating method (upper steam enters the cooling system from the downpipe of the water tank through a pipe, or directly into the engine Cooling water jacket), electric preheating method (inserting the heater directly into the cooling system or engine oil, this method has high thermal efficiency and is more convenient to use) and other methods for low-temperature startup.