When operating excavator in high-altitude and cold environments, starting difficulties are often encountered. To initiate the engine, some experienced drivers even resort to methods like heating the oil pan, pouring hot water into the engine, or pushing the vehicle downhill. Today, let's discuss why it's challenging to start excavators in high-altitude and cold regions and explore corresponding solutions.
Diesel engines are compression-ignition internal combustion engines, and starting them requires certain conditions: (1) reaching a certain speed during startup, (2) having a mixture gas pressure greater than the pressure required for compression ignition at the end of the compression stroke, (3) ensuring sufficient temperature of the mixture gas inside the cylinder at the end of the compression stroke, and (4) attaining a certain concentration of oxygen in the compressed gas.
Why is it difficult to start engines in high-altitude cold environments?
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In high-altitude regions, the atmospheric pressure is lower, and winter temperatures are significantly lower than in plain areas, typically 20-30 degrees Celsius lower, with extreme temperatures around -40°C. The lower intake temperature and pressure make it difficult for the engine to reach the temperature and pressure required for compression ignition at the end of the compression stroke, resulting in starting difficulties.
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As altitude increases, the oxygen content in the air decreases. At elevations above 3000 meters, the air contains only 60%-70% of the oxygen found at sea level, making it difficult for diesel engines to start due to the low oxygen content in the mixture gas they intake.
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In cold high-altitude conditions, the output capacity of batteries decreases, limiting the output power of the starter motor and resulting in a lower starting speed for the diesel engine.
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At low temperatures, the viscosity of engine oil increases, leading to increased friction resistance in engine components and further reducing the starting speed of the diesel engine.
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Under low-temperature conditions, diesel viscosity increases, affecting fuel atomization. Some lower-grade diesel fuels may even solidify and wax, further hindering combustion and ignition.
How to improve the starting capability of diesel engines?
(1) Use batteries with low-temperature resistance technology and insulate them to ensure normal charging and discharging performance in low-temperature conditions, thereby enhancing the low-temperature starting performance of the diesel engine.
(2) Lower the ignition point of the mixture gas, for example, by using ether to assist cold starts. Since the ignition point of ether at 3.2 MPa pressure is only 57°C, injecting a certain proportion of ether into the intake manifold of the diesel engine before starting can facilitate ignition. Injecting ether starter fluid while the diesel engine is running yields the best results. However, ether and intake flame preheating or ether and intake resistance heating cannot be used simultaneously, as this may cause the starter fluid mixture to explode, resulting in serious consequences.
(3) Use lubricating oils with good low-temperature performance, as oils with lower viscosity at low temperatures provide better lubrication, facilitating cold starts.
(4) Preheat the diesel engine intake: One method is to electrically heat the resistor wire installed in the intake manifold to raise the intake temperature of the diesel engine. Another method is flame intake preheating, where the preheating plug is connected before starting, heating it to about 900°C after a dozen seconds. When the diesel engine starts, diesel is pumped out by the fuel pump, enters the nozzle for atomization via the controlled solenoid valve, and mixes with air to form a flammable mixture. When the flammable mixture contacts the red-hot plug, it ignites, preheating the intake.
The flame intake preheating method is very effective in cold regions; however, in oxygen-deficient high-altitude areas, using this method consumes a certain amount of oxygen, which reduces the oxygen content required for diesel engine detonation. Therefore, it is not recommended to use flame intake preheating in high-altitude regions.
(5) Install an engine preheating system: For construction machinery operating in cold high-altitude regions for extended periods, installing a "liquid fuel heater" that heats the engine's coolant by burning negative diesel can effectively preheat the entire engine. As the engine temperature increases, starting difficulties are resolved.
(6) Install a fuel heating system: Sometimes, simply adding negative diesel fuel is insufficient for machinery operating in cold regions, necessitating the installation of a fuel heating system. There are two types of fuel heating systems: one places a resistor wire above the diesel filter to heat the diesel inside the oil pipe, while the other is a tank heating system that heats the diesel inside the entire tank.
